CN101478631A - Imaging system, imaging apparatus, portable terminal apparatus, onboard apparatus, medical apparatus and method of manufacturing the imaging system - Google Patents

Abstract

The present invention provides an imaging system capable of improving the quality of image data obtained by capturing an optical image projected on a light receiving surface. An imaging system composed of an imaging lens (10) and an imaging element (20) is prepared, and the imaging system also makes the point The maximum diameter of the effective area of the image ( P1 ) is 3 pixels or more related to the light-receiving pixels. The signal processing unit (40) generates a second image equivalent to the first image data output from the imaging element (20) when the resolution of the imaging lens (10) is high, on the first image data output from the imaging element (20). Data recovery processing. The imaging lens has in order from the object side: a first lens group consisting of at least one lens and having a positive refractive power; a second lens group consisting of at least one lens and having a negative refractive power; The third lens group is composed of at least one lens, and the lens on the most image side has a negative refractive power.

Description

Camera system, manufacturing method thereof, and camera device including the camera system

technical field

The present invention relates to an imaging system that improves the quality of image data obtained by capturing an optical image of a subject by restoration processing, a method of manufacturing the imaging system, an imaging device, a portable terminal device, an in-vehicle device, and a medical device including the imaging system.

Background technique

There is known an imaging system that captures an optical image of a subject formed on the light receiving surface by an imaging lens using an imaging element such as a CCD element or a CMOS element having a light receiving surface configured by arranging a plurality of light receiving pixels two-dimensionally.

In addition, as an example of such an imaging system, a vehicle-mounted camera or a mobile phone camera, etc. are known by directly mounting an imaging system having an imaging lens designed to increase the depth of field on a circuit board (see Patent Document 1). Such a camera system mounted directly on a circuit board is limited in size, so the device size is designed to be small.

Furthermore, there are also known high-performance vehicle-mounted cameras or mobile phone cameras equipped with an imaging system that increases the number of light-receiving pixels of an imaging element and improves the resolution of an imaging lens. As an imaging system mounted on such a high-performance vehicle-mounted camera or a camera for a mobile phone capable of obtaining an image with high resolution, an imaging system having a performance in which the resolution of an imaging lens is close to the diffraction limit is known.

Patent Document 1: (Japanese) Unexamined Patent Publication No. 2007-147951

However, further improvement in resolution is required for images obtained by such imaging systems.

To increase the resolution of images obtained by the camera system, it is necessary to increase the number of light-receiving pixels and at the same time increase the resolution of the camera lens. That is, for example, while increasing the pixel density of the light-receiving pixels arranged on the light-receiving surface of the imaging element, the resolution of the imaging lens is increased so that the point image projected onto the light-receiving surface through the imaging lens converges within the range of one light-receiving pixel, Thereby, the resolution of the image obtained by the camera system can be improved.

Here, as technology has improved in recent years, it is relatively easy to increase the pixel density of the light-receiving pixels constituting the imaging element without increasing the size of the device.

On the other hand, it is very difficult to increase the resolution of an imaging lens. That is, in order to improve the resolution of the imaging lens without increasing the size of the imaging lens or reducing the depth of field, it is necessary to suppress shape errors, assembly errors, and the like of each lens constituting the imaging lens. However, in some cases, the resolution of such an imaging lens has been improved to approach the diffraction limit, and there is a problem that it is very difficult to further improve the manufacturing precision (processing, assembly, adjustment precision, etc.) to improve the resolution.

However, in manufacturing an imaging system having such an imaging lens capable of forming an image with high resolution, it is difficult to improve the yield due to the difficulty of manufacturing. That is, since image data capable of forming an image with a predetermined resolution cannot be generated, there is a possibility that many camera systems that are dismantled from the manufacturing line and returned to be readjusted or reassembled are generated. Furthermore, in the case of an imaging system removed from a manufacturing line, by identifying the cause and correcting it, image data capable of forming an image of a predetermined resolution is reproduced and generated.

However, there are many reasons for the decrease in the resolution of the image represented by the image data output from the imaging system. , Adjustment error (lens offset error, tilt error, air gap error between lenses), positioning error of the imaging element to the imaging lens, etc. Therefore, there is a problem that huge costs are incurred in order to regenerate an imaging system capable of generating high-quality image data capable of forming an image with a predetermined resolution by identifying the cause of the decrease in resolution and performing readjustment or reassembly. .

Contents of the invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide an imaging system capable of improving the quality of image data obtained by photographing an optical image projected on a receiving surface, a method of manufacturing the imaging system, and an imaging system having the same. Camera equipment, portable terminal equipment, vehicle-mounted equipment, and medical equipment.

The imaging system according to the first aspect of the present invention is characterized in that it includes: an imaging lens; output the first image data representing the object; and the signal processing unit generates second image data equivalent to the first image data output from the imaging element when the resolution of the imaging lens is high on the first image data. Restoration processing of image data; the imaging lens has sequentially from the object side: a first lens group including at least one lens and having a positive refractive power, a second lens group including at least one lens and having a negative refractive power, And the 3rd lens group that comprises at least 1 lens and the lens that is positioned at the closest to the image side has positive refractive power; The imaging lens and the imaging element are constituted: for any position from the X, Y, Z directions through the imaging lens projection The point image on the light-receiving surface is also made such that the maximum diameter of the effective area of the point image is 3 pixels or more related to the light-receiving pixel.

The above-mentioned imaging lens can be configured such that the optical image of the subject projected onto the light-receiving surface through the imaging lens from any position in the X, Y, and Z directions that is more than 10 times the focal length of the imaging lens is also compatible with the imaging lens. The value of the MTF characteristic related to the optical image becomes positive.

The above-mentioned signal processing unit can perform restoration processing on a pixel area involving a total of 9 pixels or more consisting of more than 3 pixels in the vertical direction and more than 3 pixels in the horizontal direction on the light-receiving surface; The minimum pixel area of the area is used as the minimum unit to perform restoration processing.

The signal processing unit may perform restoration processing so that a size of an effective area representing a point image in an image represented by the second image data is smaller than a size of an effective area representing a point image in an image represented by the first image data.

The signal processing unit executes the restoration process using a restoration coefficient corresponding to a state of a point image represented by the first image data.

The above-mentioned restoration coefficient may be obtained individually for each imaging system; or may be obtained from the points represented by the first image data among the candidates for the restoration coefficients corresponding to the states of the point images classified into a plurality of types. selected according to the state of the point image; or may be a restoration coefficient selected according to the state of the point image represented by the first image data from a plurality of candidates for restoration coefficients corresponding to each state of the point image divided into a plurality of types The restoration coefficient is further corrected according to the state of the point image.

The imaging system described above may further include a restoration coefficient obtaining unit for obtaining a restoration coefficient.

The imaging system according to the second aspect of the present invention is characterized in that it includes: an imaging lens; The optical image of the object is output to represent the first image data of the object; the coefficient storage unit, when the maximum diameter of the effective area of the point image projected onto the light receiving surface by the above-mentioned imaging lens is related to the size of more than 3 pixels, for Store the restoration coefficient corresponding to the state of the point image represented by the first image data output from the imaging element; and the signal processing unit generates the first image data output from the imaging element using the restoration coefficient stored in the coefficient storage unit Restoration processing of the second image data equivalent to the first image data output from the imaging element when the resolution of the imaging lens is high; the signal processing unit combines a total of 9 The pixel area above the pixel is used as the smallest unit for restoration; the imaging lens has in order from the object side: the first lens group including at least one lens and having a positive refractive power, including at least one lens and having a negative refractive power The second lens group, and the third lens group including at least one lens and the lens on the most image side has positive refractive power.

The coefficient storage means may store, for each imaging system, the restoration coefficient obtained individually for the imaging system.

In addition, the coefficient storage unit may store a restoration coefficient selected from the candidates for each restoration coefficient corresponding to each state of the point image classified into a plurality of types according to the state of the point image represented by the first image data.

Furthermore, the coefficient storage unit may store a restoration coefficient selected from the state of the point image represented by the first image data from among candidates for a plurality of restoration coefficients corresponding to each state of the point image classified into a plurality of types. Corrected restoration coefficient corrected according to the state of the point image.

The imaging system described above may be provided with a restoration coefficient obtaining unit that obtains the restoration coefficient and stores it in the coefficient storage unit.

The above-mentioned signal processing unit may perform restoration processing using the minimum pixel area including all effective areas of the point image projected on the light receiving surface as a minimum unit.

The signal processing unit preferably performs restoration processing so that the effective area of the point image in the image represented by the second image data is smaller than the effective area of the point image in the image represented by the first image data.

In the above-mentioned imaging systems of the first aspect and the second aspect, the lens surface of the third lens group located closest to the image side may have an off-axis inflection point, or may have a concave surface toward the image side at the center portion of the lens surface. On the other hand, the peripheral portion is convex toward the image side, or satisfies the following conditional expression (1).

0.5H<h<H...(1)

in,

H: The effective radius of the lens surface on the image side closest to the third lens group,

h: the distance from the off-axis inflection point to the optical axis of the lens surface located closest to the image side in the third lens group.

Here, the inflection point is a point on the lens surface, and when the tangent plane of the point is perpendicular to the optical axis C (Z axis), the point is called an inflection point. In addition, a curved point other than a point intersecting the optical axis on the lens surface is called an off-axis curved point.

The lens surface on the object side of the lens located closest to the image side in the third lens group may be convex toward the object side at the center of the lens surface and concave toward the object side at the peripheral portion.

The imaging lens may be composed of three single lenses.

The single lens of the first lens group may have a meniscus shape with a convex surface facing the object side, and the single lens of the second lens group may have a meniscus shape with a convex surface facing the image side.

An imaging device of the present invention is characterized by comprising the imaging system of the first aspect or the second aspect described above.

A mobile terminal device according to the present invention includes the imaging system of the first aspect or the second aspect described above.

An in-vehicle device of the present invention is characterized by comprising the imaging system of the first aspect or the second aspect.

A medical device of the present invention is characterized by comprising the imaging system of the first aspect or the second aspect.

The imaging system according to the third aspect of the present invention is characterized in that it has: an imaging lens; output the first image data representing the subject; the coefficient storage unit, when the maximum diameter of the effective area of the point image projected onto the light-receiving surface through the imaging lens is a size of more than 3 pixels, stores the same as A restoration coefficient corresponding to the state of the point image represented by the first image data output from the imaging element; Restoration processing of the second image data equivalent to the first image data; the signal processing unit performs restoration processing on a pixel area involving a total of 9 pixels or more consisting of 3 or more pixels in the vertical direction and 3 or more pixels in the horizontal direction on the light receiving surface as the minimum unit; In order from the object side: the first lens group including at least one lens and having positive refractive power, the second lens group including at least one lens and having negative refractive power, and the second lens group including at least one lens and located at The lens closest to the image side has a third lens group with positive refractive power.

The manufacturing method of the imaging system of the present invention is characterized in that, in the manufacturing of the imaging system of the above-mentioned third aspect, the point image is projected onto the light receiving surface of the imaging element through the imaging lens, and the coefficient storage unit is stored in the coefficient storage unit based on the The restoration coefficient corresponding to the state of the point image represented by the first image data output by the imaging element.

The aforementioned restoration coefficient may be calculated for each imaging system individually.

The restoration coefficients may be selected from the candidates for the restoration coefficients corresponding to the states of the point images classified into a plurality of types according to the state of the point image represented by the first image data.

In addition, the above-mentioned restoration coefficient may be a restoration coefficient selected based on the state of the point image represented by the first image data from a plurality of types of restoration coefficient candidates corresponding to each state of the point image classified into a plurality of types. The state of the point image is corrected by the restoration factor.

In addition, the above-mentioned restoration coefficient may be obtained individually for each imaging system.

In each aspect of the present invention described above, the maximum diameter of the effective area of the point image projected on the light receiving surface may be the maximum diameter of the effective area in the direction in which the effective area of the point image projected on the light receiving surface contains the most light receiving pixels. Diameter, the above-mentioned "the maximum diameter of the effective area of the point image becomes a structure with a size of more than 3 pixels" may be "in the direction in which the effective area of the point image includes the most light-receiving pixels, the effective area becomes 3 pixels related to the light-receiving pixels. Structures above the size of a pixel".

The above-mentioned "effective area of the point image" means an area having a light intensity equal to or greater than 1/e ² (about 13.5%) of the peak intensity in the light intensity distribution of the point image.

In addition, the above-mentioned "restoration processing" can adopt the image restoration processing described in Japanese Patent Laid-Open No. 2000-123168, paragraphs 0002-0016, and the like. In addition, the following non-patent literature [Koichi Washizawa and Yukihiko Yamashita, entitled "Kernel Wiener Filter", 2003 Workshop on Information-Based Induction Sciences, (IBIS2003), Kyoto, Japan, Nov 11, can be used in the implementation of the restoration process. -12, 2003] techniques et al.

In addition, the above-mentioned "position at least 10 times the focal length of the imaging lens" means "the position where the surface closest to the subject side (object side) among the lens surfaces constituting the imaging lens intersects the optical axis of the imaging lens is taken as A reference position is a position away from the reference position toward the subject side along the optical axis direction (Z-axis direction) of the imaging lens by 10 times or more of the focal length".

In the imaging system according to the first aspect of the present invention, the imaging lens is made to have in order from the object side: a first lens group including at least one lens and having a positive refractive power, and a first lens group including at least one lens and having a negative optical power degree of the second lens group, and the third lens group including at least one lens and the lens on the closest to the image side has a positive refractive power; the imaging lens and the imaging element are configured to: To the point image on the light-receiving surface, the maximum diameter of the effective area of the point image becomes the size of 3 pixels or more related to the light-receiving pixel, and the first image data output from the imaging element is generated and compared with the resolution of the imaging lens. Since the restoration process of the second image data equivalent to the first image data output from the imaging element is high, the quality of the image data obtained by capturing the optical image projected on the light receiving surface can be easily improved.

That is, in the imaging system according to the first aspect of the present invention, an imaging lens having a low resolution can be used to obtain an image equivalent to an image obtained by capturing an optical image projected through an imaging lens having a resolution higher than that of the imaging lens. . For example, the effective area of the point image projected through the imaging lens may be 9 pixels in total of 3 pixels in the vertical direction and 3 pixels in the horizontal direction on the light receiving surface. Then, a restoration process is performed on the first image data outputted from the imaging element by shooting the point image involving a total of 9 pixels, so that the image data generated from the image data when, for example, the effective area of the point image converges in the area of 1 pixel on the light-receiving surface The first image data output from the element (that is, the first image data output from the imaging element when the resolution of the imaging lens is high) is equivalent to the second image data, so the resolution of the image expressed by the first image data can be obtained. Higher resolution represents the second image data of the same image.

Furthermore, in this imaging system, the restoration process can be performed on an optical image projected from an arbitrary position on the light receiving surface through the imaging lens, so that the resolution of the entire image represented by the first image data can be improved. That is, the resolution of any region in the image represented by the second image data may be higher than the resolution of the image represented by the first image data.

As a result, the quality of image data can be improved more easily than in the conventional case of increasing the manufacturing accuracy (processing, assembly, adjustment accuracy, etc.) of the imaging system to increase the resolution of the imaging lens.

In addition, the imaging lens is configured such that if the optical image of the subject projected onto the light-receiving surface through the imaging lens from any position in the X, Y, and Z directions that is more than 10 times the focal length of the imaging lens is such that When the value of the MTF characteristic related to the optical image becomes positive, the quality of the first image data representing a subject located at a distance of 10 times or more from the focal length of the imaging lens can be further reliably improved.

In addition, if the signal processing unit performs the above-mentioned restoration processing on a pixel area consisting of 3 or more vertical pixels and 3 or more horizontal pixels on the light receiving surface and involving a total of 9 pixels or more as the minimum unit, the restoration processing can be performed more reliably.

Furthermore, if the signal processing unit executes the restoration process using the minimum pixel area including all effective areas of the point image projected on the light receiving surface as the minimum unit, the restoration process can be efficiently performed while suppressing an increase in the calculation amount of the restoration process. .

In addition, if the signal processing unit performs restoration processing so that the size of the effective area representing the point image in the image represented by the second image data is smaller than the size of the effective area representing the above-mentioned point image in the image represented by the first image data, Then, the quality of the image data can be improved more reliably.

Here, if the signal processing unit executes the restoration process using a restoration coefficient corresponding to the state of the point image represented by the first image data (hereinafter also referred to as the blurred state of the point image), the blurred state of the above-mentioned point image can be more accurately determined. Since the corrected second image data can be obtained, the quality of the image data can be improved more reliably.

Furthermore, the "state of a point image" is also referred to as a "blurred state of a point image". The quality of the point image is slightly lower than that of the object point corresponding to the point image, that is, the subject due to the influence of image lens aberration and the like. That is, for example, when the subject is a resolution chart, the image of the resolution chart projected onto the light-receiving surface through the imaging lens and the image of the resolution chart represented by the first image data obtained by capturing the image of the resolution chart resolution that is lower than that of the subject's resolution chart. Also, the "state of point image" or "blurred state of point image" mainly indicates the state of degradation of the resolution of the point image.

In addition, if the restoration coefficient is calculated individually for each imaging system, the restoration coefficient that can improve the quality of image data can be obtained more accurately.

In addition, if the restoration coefficient is selected from the candidates for each restoration coefficient corresponding to each blur state of the point image classified into a plurality of types based on the blur state of the point image represented by the first image data, then for each image Compared with the case where the system calculates the restoration coefficient independently, the restoration coefficient can be obtained more easily.

Furthermore, if the restoration coefficient is based on the blurred state of the point image, the blurring of the point image represented by the first image data is further corrected from the candidates of multiple restoration coefficients corresponding to each blurred state of the point image classified into a plurality of types. The restoration coefficient of the restoration coefficient selected by the state can be obtained more easily while suppressing a decrease in accuracy when obtaining the restoration coefficient than when obtaining the restoration coefficient individually for each imaging system.

In addition, if the imaging system includes a restoration coefficient acquisition unit that acquires a restoration coefficient, the restoration coefficient can be obtained more reliably.

The imaging system of the second aspect of the present invention has: a coefficient storage unit, when the maximum diameter of the effective area of the point image projected on the light receiving surface through the imaging lens is 3 pixels or more, it is compared with the output from the imaging element. The restoration coefficient corresponding to the state of the point image represented by the first image data (hereinafter also referred to as the blurred state of the point image) is stored; and the signal processing unit uses the restoration coefficient to perform generation and resolution in the imaging lens on the first image data When the rate is high, the restoration process of the second image data equivalent to the first image data output from the imaging element; the signal processing unit regards the pixel area involving a total of 9 pixels or more consisting of 3 or more pixels in the vertical direction and 3 or more pixels in the horizontal direction on the light receiving surface as The smallest unit performs restoration processing; the imaging lens has sequentially from the object side: a first lens group including at least one lens and having a positive refractive power, a second lens group including at least one lens and having a negative refractive power, And the third lens group including at least one lens and the lens on the closest image side has a positive refractive power. Therefore, if the restoration coefficient is stored in the coefficient storage unit, the restoration process using the restoration coefficient can be implemented, thereby , it is possible to easily improve the quality of the image data obtained by projecting the optical image onto the light receiving surface.

That is, when the resolution of the image represented by the first image data output from the imaging system does not reach a predetermined level as in the past, it is not necessary to identify the cause and readjust or reassemble the imaging lens. The restoration coefficient corresponding to the blurred state of the point image is stored in the coefficient storage unit, and only the restoration processing (image processing) is performed on the first image data, and the second image data representing an image with a predetermined resolution can be obtained, so that the shooting can be improved. The quality of the image data obtained by projecting the optical image onto the light-receiving surface.

Furthermore, as described above, the "state of the point image" is also referred to as "the blurred state of the point image".

In addition, if the coefficient storage unit stores the restoration coefficient obtained individually for each imaging system, the restoration coefficient can be obtained more accurately and the restoration process can be performed more accurately, so that the imaging projection can be improved more reliably. The quality of the image data obtained from the optical image of the light-receiving surface.

Furthermore, if the coefficient storage means stores a restoration coefficient selected from the blurred state of the point image represented by the first image data among the candidates for the respective restoration coefficients corresponding to the respective blurred states of the point images classified into a plurality of types, then the same as The restoration coefficient can be set more easily than the case where the restoration coefficient is obtained individually for each imaging system.

Here, if the coefficient storage unit stores, according to the blurred state of the point image, the number of candidates for the restoration coefficients corresponding to the respective blurred states of the point image divided into a plurality of types, of the point image represented by the first image data The corrected restoration coefficient that is further corrected for the restoration coefficient selected in the blurred state can suppress the decrease in accuracy when obtaining the restoration coefficient and make it easier Get the coefficient of restitution.

Furthermore, if the imaging system includes a restoration coefficient obtaining unit that obtains the restoration coefficient and stores it in the coefficient storage unit, the restoration coefficient can be obtained more reliably.

In addition, if the signal processing unit executes the restoration process using the minimum pixel area including all the effective areas of the point image projected on the light receiving surface as the minimum unit, the increase in the amount of computation for performing the restoration process can be suppressed, and efficient perform recovery processing.

In addition, if the signal processing unit performs restoration processing so that the size of the effective area of the point image in the image represented by the second image data is smaller than the size of the effective area of the point image in the image represented by the first image data, it can be more reliably Improves the quality of image data obtained by capturing an optical image projected onto a light receiving surface.

In addition, in the above-mentioned imaging systems of the first and second aspects, if the lens surface of the third lens group located closest to the image side has an off-axis inflection point, or has a concave surface toward the image side at the central portion and a concave surface toward the image side at the peripheral portion, If the image side is convex, or satisfies the conditional expression (1), that is, the expression 0.5H<h<H, then the telecentricity of the imaging lens can be improved more reliably, so the performance of the first image data representing the object can be improved more reliably. quality.

Here, if the lens surface of the lens on the object side of the lens closest to the image side in the third lens group is convex toward the object in the center of the lens surface and concave toward the object in the peripheral portion, it can be more reliably improved. Indicates the quality of the first image data of the subject.

Moreover, if the imaging lens is composed of three single lenses, and the single lens of the first lens group has a meniscus shape with a convex surface facing the object side, and the single lens of the second lens group has a meniscus shape with a convex surface facing the image side, Then, the quality of the first image data representing the subject can be improved more reliably. .

The imaging device, portable terminal equipment, vehicle-mounted equipment, and medical equipment of the present invention each have the imaging system of the first or second aspect described above. Therefore, as described above, the image obtained by capturing the optical image projected on the light-receiving surface can be easily improved. the quality of the data.

The imaging system according to the third aspect of the present invention has: a coefficient storage unit, when the maximum diameter of the effective area of the point image projected on the light receiving surface through the imaging lens is 3 pixels or more, stores the coefficient corresponding to the coefficient output from the imaging element. The restoration coefficient corresponding to the state of the point image represented by the first image data; and the signal processing unit, using the restoration coefficient to perform generation on the first image data and the first image output from the above-mentioned imaging element when the resolution of the imaging lens is high Restoration processing of the second image data with the same data; the signal processing unit performs restoration processing on a pixel area involving a total of 9 pixels or more consisting of 3 or more pixels in the vertical direction and 3 or more pixels in the horizontal direction on the light receiving surface as the minimum unit; In order: a first lens group including at least one lens and having positive refractive power, a second lens group including at least one lens and having negative refractive power, and a second lens group including at least one lens and located closest to the image The lens on the side has a third lens group with positive refractive power; therefore, similar to the above-mentioned first imaging system, by performing restoration processing using a restoration coefficient, it is possible to easily improve the image obtained by capturing the optical image projected on the light-receiving surface. the quality of the data.

In the manufacturing method of the imaging system of the present invention, in the manufacturing of the imaging system of the above-mentioned third aspect, the point image is projected onto the light receiving surface of the imaging element through the imaging lens, and the coefficient storage unit stores the point image corresponding to the first output from the imaging element. 1 The restoration coefficient corresponding to the state of the point image represented by the image data, so the second imaging system can be manufactured efficiently.

For example, even when the resolution of the image represented by the image data output from the imaging system does not reach a predetermined level due to manufacturing conditions, etc., it is easier than before to perform regeneration processing of the imaging system to increase the resolution of the image. That is, with the image pickup system that stores the restoration coefficients in the coefficient storage unit, it is possible to easily perform restoration processing that improves the quality of image data output from the image pickup system, and therefore, it is possible to easily reproduce the image pickup system whose image resolution does not reach a predetermined level. An imaging system capable of obtaining a predetermined level of image resolution can be manufactured efficiently.

Furthermore, by producing a large number of imaging systems, it is possible to enjoy a greater effect of efficiently manufacturing the above-mentioned imaging systems.

Description of drawings

FIG. 1 is a block diagram showing a schematic configuration of an imaging system of the present invention.

FIG. 2( a ) is a diagram showing a light intensity distribution of a point image, and FIG. 2( b ) is a diagram showing a point image projected onto a light receiving surface.

3( a ) is a diagram of an image of a point image shown in an image represented by the first image data, and FIG. 3( b ) is a diagram of an image of a point image shown in an image represented by the second image data.

Fig. 4(a) is a diagram showing the light intensity distribution of the point image projected on the light receiving surface when the resolution of the imaging lens is high, and Fig. 4(b) is the light intensity distribution of the point image projected on the light receiving surface when the resolution of the imaging lens is high A graph of the point image.

5 is a graph showing changes in the maximum diameter of an effective area of a point image which is an optical image of an object point projected onto a light receiving surface when the object point is moved in the optical axis direction.

6 is a graph showing changes in values (%) of MTF characteristics related to an optical image of an object point projected onto a light receiving surface when the object point is moved in the optical axis direction.

Fig. 7 is a diagram showing a second example of a restoration coefficient acquisition device.

Fig. 8 is a diagram showing a third example of a restoration coefficient acquisition device.

FIG. 9 is a diagram showing an imaging system including a restoration coefficient acquisition device inside.

FIG. 10 is a diagram showing an imaging system including a restoration coefficient acquisition device inside a signal processing unit.

11 is a block diagram showing a schematic configuration of an imaging system and a method of manufacturing the imaging system according to the present invention.

Fig. 12 is a diagram showing a second example of a restoration coefficient acquisition device.

Fig. 13 is a diagram showing a third example of a restoration coefficient acquisition device.

FIG. 14 is a diagram showing an imaging system including a restoration coefficient acquisition device.

15 is a diagram showing an imaging system including a restoration coefficient acquisition device and a coefficient storage unit in a signal processing unit.

16 is a cross-sectional view showing a schematic configuration of an imaging lens disposed in the imaging system of the first embodiment.

Fig. 17 is a diagram showing a change in the value of the MTF characteristic when the light receiving surface is defocused. Fig. 17(a) is a diagram showing a change in the value of the MTF characteristic at a spatial frequency of 20 lines/mm, and Fig. 17(b) is Figure 17(c) is a graph showing the change in the value of the MTF characteristic at the spatial frequency of 30 wires/mm, and Figure 17(d) shows the change in the value of the MTF characteristic at the spatial frequency of 40 wires/mm. A graph of the change in the value of the MTF characteristic for root/mm spatial frequency.

FIG. 18 is a graph showing aberrations related to the imaging lens of Example 1. FIG.

19 is a cross-sectional view showing a schematic configuration of an imaging lens arranged in an imaging system of a comparative example.

Fig. 20 is a graph showing changes in the value of the MTF characteristic when the light receiving surface is defocused, and Fig. 20(a) is a graph showing a change in the value of the MTF characteristic at a spatial frequency of 20 lines/mm, and Fig. 20(b) is Figure 20(c) is a graph showing changes in the value of the MTF characteristic at a spatial frequency of 30 lines/mm, and Figure 20(d) shows changes in the value of the MTF characteristic at a spatial frequency of 40 lines/mm, and Figure 20(d) shows 50 A graph of the change in the value of the MTF characteristic for root/mm spatial frequency.

FIG. 21 is a diagram showing an automobile equipped with an in-vehicle device including an imaging system.

FIG. 22 is a diagram showing a mobile phone which is a portable terminal device equipped with an imaging system.

FIG. 23 is a diagram showing an endoscope apparatus that is medical equipment including an imaging system.

In the figure: 10-imaging lens, 20-imaging element, 21-light-receiving surface, 30-coefficient storage unit, 40-signal processing unit, 70A-reconstruction coefficient acquisition device of the first example, 70B-reconstruction coefficient acquisition of the second example Device, 70C-the restoration coefficient acquisition device of the 3rd example, 72-ideal point image storage unit, 74-point image diameter acquisition unit, 76-judgment unit, 78-restoration coefficient acquisition unit, 79-candidate coefficient storage unit, 100, 200-camera system, G1-first image data, G2-second image data, F-restoration processing, P1-point image, K-restoration coefficient, Dr-design data, ideal point image state data, Dk-coefficient data.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(first embodiment)

FIG. 1 is a block diagram showing a schematic configuration of an imaging system according to a first embodiment of the present invention.

[About the structure of the camera system]

The configuration of the imaging system of the first embodiment will be described below.

The imaging system 100 of the present invention shown in Fig. 1 has: imaging lens 10; The optical image P1 of the subject is taken, and the first image data G1 representing the subject is output; Restoration processing of the second image data G2 equivalent to the output first image data G1.

The imaging lens 10 includes, in order from the subject side (object side), a first lens group consisting of at least one lens and having positive refractive power; a first lens group consisting of at least one lens and having negative refractive power; a second lens group; and a third lens group consisting of at least one lens, the lens on the most image side having positive refractive power.

The imaging lens 10 and the imaging lens element 20 are configured so that the point image (P1) projected onto the light-receiving surface 21 through the imaging lens 10 from any position in the X, Y, and Z directions is effective. The maximum diameter of the region is 3 or more pixels related to the light-receiving pixels.

Here, the maximum diameter of the effective area of the point image projected on the light receiving surface 21 is the diameter of the effective area of the point image P1 projected on the light receiving surface 21 in the direction in which the effective area of the point image P1 includes the most light receiving pixels.

In FIG. 1 , the direction indicated by the arrow Z is the optical axis direction of the imaging lens 10 , and the directions indicated by the arrows X and Y are directions parallel to the light receiving surface 21 .

Outside the imaging system 100 is provided a restoration coefficient acquisition device 70A that acquires a restoration coefficient K corresponding to the blurred state of the point image P1 represented by the first image data G1 output from the imaging device 20 . The signal processing unit 40 performs the restoration process F using the restoration coefficient K acquired by the restoration coefficient acquisition device 70A.

Here, the imaging system 100 may have the coefficient storage unit 30 that stores the restoration coefficient K acquired by the restoration coefficient acquisition device 70A, but the coefficient storage unit 30 may be incorporated in the signal processing unit 40 . Furthermore, the coefficient storage unit 30 does not necessarily need to be provided in the imaging system 100 .

The above-mentioned restoration coefficient acquisition device 70A has: an ideal point image storage unit 72, which stores in advance design data related to a point image when there is no error in the optical system including the imaging lens 10 or related to an ideal point image state superior to it. Any one of the data Dr in the ideal point image state data; the point image blur state acquisition part 73 is used to obtain the blur point image state data of the blur state of the point image P1 represented by the first image data G1 output from the imaging element 20 Db; and the restoration coefficient acquisition unit 78A, which inputs the blurred point image state data Db representing the blurred state of the point image P1 obtained by the point image blurred state acquisition unit 73 and the design data stored in the ideal point image storage unit 72 or The ideal point image state data is the data Dr, and the coefficient data Dk representing the restoration coefficient K corresponding to the blurred state of the point image P1 represented by the first image data G1 is obtained through the operation using both, and the coefficient data Dk The indicated restoration coefficient K is stored in the coefficient storage unit 30 .

In addition, the imaging lens used in the imaging system of the present invention (including the second embodiment described below) is not limited to the imaging lens that "accurately" forms an optical image on the light-receiving surface through the imaging lens. An imaging lens whose optical image is "inaccurately" formed on the light-receiving surface can also be used, so an imaging system that "projects" an optical image on the light-receiving surface through the imaging lens is used and described in the present invention. Although the "non-imaging" state can be interpreted as a so-called blurred image, it includes, for example, a state in which a point image that is more diffuse than the original point image is generated due to manufacturing errors, or due to design constraints (size or cost of the optical system) ) can only provide a point image larger than the point image originally intended by the design value itself.

In addition, as described above, the blurred point image state data Db mainly representing the degradation state of the resolution of the point image may represent, for example, the size of the effective area of the point image P1 or the luminance distribution on the light receiving surface of the point image P1 (in the image). concentration distribution), etc.

[About the role of the camera system]

Next, the operation of the imaging system described above will be described.

First, an example in which the restoration coefficient is obtained by the restoration coefficient acquisition device and the restoration coefficient is stored in the coefficient storage unit will be described.

The optical image of the subject projected onto the light receiving surface 21 through the imaging lens 10 is captured by the imaging element 20, and the first image data G1 representing the subject output from the imaging element 20 is input to the point image blurred state acquisition unit 73. .

The point image blurred state acquisition unit 73 that receives the first image data G1 analyzes the blurred state of the point image represented by the first image data G1 and outputs blurred point image state data Db indicating the analysis result.

The restoration coefficient acquisition unit 78A receives the blurred point image state data Db output from the point image blurred state acquisition unit 73 and the design data prestored in the ideal point image storage unit 72 or the data Dr as the ideal point image state data, and passes The restoration coefficient K corresponding to the blurred state of the point image P1 is obtained by the calculation of both, and the coefficient data Dk representing the restoration coefficient K is output.

The coefficient data Dk representing the restoration coefficient K output from the restoration coefficient acquisition unit 78A is input to the coefficient storage unit 30 , and the restoration coefficient K indicated by the coefficient data Dk is stored in the coefficient storage unit 30 .

In addition, as an example of realizing the function of the point image blurred state acquisition unit 73, a D×O analyzer (analyser) manufactured by D×O Labs (France) described later is mentioned. According to this D×O analyzer, the blur state of the point image P1 on the projection light receiving surface 21 can be obtained by analyzing the first image data G1 output from the imaging element 20 .

[about restoration processing]

Next, the second image obtained by performing the restoration process F on the first image data output from the imaging device 20 using the restoration coefficient K stored in the coefficient storage unit 30 and obtaining an image with a higher resolution than the image represented by the first image data will be described. The condition of the data. In addition, in the following description, the case where the restoration process F is performed on the 1st image data which shows a point image is mainly demonstrated.

FIG. 2( a ) is a diagram showing the light intensity distribution of a point image on coordinates in which the vertical axis represents the light intensity E and the horizontal axis represents the position in the X direction on the light receiving surface. Fig. 2 (b) shows each pixel region of the light-receiving pixel constituting the light-receiving surface (symbol Rg represents) and the figure of the point image projected on this light-receiving surface; Fig. 3 (a) is the figure of the image of the point image shown in the image shown in the first image data; Fig. 3 (b) is in the 2nd image The data represent a plot of the image of the point image shown in the image. In addition, the respective sizes of the pixel regions (indicated by symbol Rg' in the figure) in the images shown in FIG. 3( a ) and FIG. 3( b ) coincide with each other. Further, each pixel area Rg constituting the light receiving pixels of the light receiving surface 21 corresponds to an image area Rg' in the image represented by the first image data G1 or the second image data G2.

In addition, FIG. 4( a ) shows the points projected on the light receiving surface 21 when the resolution of the imaging lens 10 is high, on coordinates in which the vertical axis represents the light intensity E and the horizontal axis represents the position in the X direction on the light receiving surface. A graph of the light intensity distribution of an image. In addition, this can also be considered to represent an ideal point image state regardless of the optical system. Fig. 4 (b) shows each pixel area of the light-receiving pixel constituting the light-receiving surface (symbol Rg represents ) and a point image P2 projected on the light receiving surface 21 when the resolution of the imaging lens 10 is high.

The maximum diameter M1 of the effective region R1 of the point image P1, which is the optical image projected on the light receiving surface 21 through the imaging lens 10, is three continuous pixels related to the light receiving pixels constituting the light receiving surface 21 as shown in FIG. 2(b). the size of. In addition, this effective region R1 is a region involving a total of 9 pixels consisting of 3 pixels in the vertical direction and 3 pixels in the horizontal direction on the light receiving surface 21 . That is, the effective region R1 is a region occupying 9 pixels (3 pixels×3 pixels) constituting the light receiving pixels of the light receiving surface 21 .

Furthermore, as shown in FIG. 2( a ), the effective region R1 of the point image P1 is a region having a light intensity equal to or greater than 1/ ^e2 of the peak intensity Ep1 in the light intensity distribution H1 of the point image P1.

The point image P1 projected on the light receiving surface 21 is captured by the imaging device 20 , and the first image data G1 representing the point image P1 is output from the imaging device 20 .

As shown in Figure 3 (a), the image P1' corresponding to the above-mentioned point image P1 shown in the image Zg1 represented by the first image data G1 still represents that the effective region R1' involves a 9-pixel portion in the image (3 pixels × 3 pixels) of the image.

Next, the signal processing unit 40 that has received the image data G1 executes the restoration process F using the restoration coefficient K1 on the first image data G1 to obtain the second image data G2.

As shown in Fig. 3 (a), (b), the image P2' of the point image in the image Zg2 represented by the second image data G2 corresponding to the image P1' of the point image represented by the above-mentioned first image data G1, the image The effective area R2' of P2' is smaller than the effective area R1' of the image P1' of the point image in the image Zg1 represented by the first image data G1. Therefore, the maximum diameter M2' (the area of the 3-pixel portion of the image region Rg') of the point image P2' represented in the image Zg2 is different from the maximum diameter M1' (the region of the image region Rg') of the image P1' of the point image represented in the image Zg1. The area of 1-pixel portion of Rg') is also reduced.

That is, the image P2' of the point image represented by the second image data G2 shown in FIG. 4) The image of the point image captured and represented by the first image data output from the imaging element 20 becomes an equivalent image.

More specifically, the first point image P1 (see FIG. The image P2' of the point image represented by the second image data G2 (refer to FIG. The point image P2 expected to be projected on the light receiving surface 21 (the maximum diameter M2 of the effective region R2 is included in one pixel region Rg, referring to FIGS. The images of the point images represented by the 1 image data G1 become equivalent images.

And, the effective region R2 of the point image P2 contained in one pixel region Rg on the light receiving surface 21 shown in FIG. A region of light intensity equal to or greater than 1/ ^e2 of the peak intensity Ep2 in the light intensity distribution H2. Here, the effective area R2 of the point image P2 has a size included in one pixel area Rg.

In this way, the resolution of the image represented by the second image data obtained by performing the restoration process on the first image data may be higher than the resolution of the image represented by the first image data.

In addition, through this restoration processing F, an image identical to that obtained when the depth of field of the imaging lens 10 is enlarged can be obtained, so the above restoration processing is also referred to as processing that substantially enlarges the depth of field of the imaging lens 10 .

In addition, in the restoration process F using the restoration coefficient K corresponding to the state of the point image P1 represented by the first image data G1 by the signal processing unit 40, the above-mentioned Japanese Patent Application Laid-Open No. 2000-123168 No. 0002-10 can be used. The image restoration processing and so on introduced in the 0016 section.

In the above description, the case of capturing a point image has been described. However, the optical image of the object projected onto the light receiving surface 21 through the imaging lens 10 is considered as a collection of point images representing the object. Regardless of what kind of object the subject is, the restoration process may be performed on the first image data to generate second image data representing an image at a higher resolution than the image represented by the first image data.

[About the performance of the camera system]

Next, the performance of the imaging system composed of the imaging lens 10 and the imaging element 20 used in the imaging system 100 described above will be described.

5 shows the distance U from the imaging lens to the object point in the optical axis direction on a logarithmic scale (m) on the abscissa, and the length corresponding to the number (N) of pixel regions arranged consecutively on the light-receiving surface on the ordinate. Coordinates schematically show changes in the maximum diameter of the effective area of the point image corresponding to the object point projected onto the light receiving surface when the object point is moved along the optical axis direction.

Here, the object point is moved from a near point position approximately in contact with the imaging lens (approximately 0.01 m position) to a far point position approximately infinitely far from the imaging lens (a position approximately 10 m apart).

The three kinds of curves (solid lines) represented by the series A-1, A-2, and A-3 in Fig. 5 schematically show the mutual differences projected on the light-receiving surface 21 by the imaging lens 10 of the imaging system of the present invention. The change in the maximum diameter of the effective area of each point image in the same specific area (specific areas on the light-receiving surface with different image heights). In addition, the curves (dotted lines) represented by the series Aw in Fig. 5 represent the images projected onto the light-receiving surface by the imaging lenses used in existing imaging systems (such as cameras for vehicles, cameras for mobile phones, cameras for medical equipment, etc.) A general variation on the maximum diameter of the effective area of the point image.

According to Fig. 5, in the existing imaging system, the maximum diameter of the effective area of the point image formed by projecting the object point on the light-receiving surface 21, as the object point moves along the optical axis direction, from the 1-pixel part The size of the varies greatly up to the size of the 30 pixel portion.

On the other hand, the maximum diameter of the effective area of the point image formed by projecting the object point onto the light receiving surface 21 through the imaging lens 10 included in the imaging system 100 of the present invention, for the series A-1, A-2, and A-3 Any of them relates to a size of not less than 3 pixels and not more than 10 pixels. That is, regardless of the distance from the imaging lens 10 to the object point and regardless of the position of the projected point image on the light receiving surface (for example, the image height on the light receiving surface), the size of the effective area of the point image on the light receiving surface changes less. Furthermore, regarding the point image projected onto the light-receiving surface through the imaging lens 10 from any position in the X, Y, and Z directions, that is, from any position in the three-dimensional space, it can also be said that the size of the effective area of the point image varies little. .

FIG. 6 schematically shows the distance U along the optical axis on a logarithmic scale (m) on the horizontal axis and the distance U from the imaging lens to the object point in the optical axis direction on the vertical axis and the value (%) of the MTF characteristic on the vertical axis. A graph showing changes in the value (%) of the MTF characteristic related to the optical image of the object point projected on the light receiving surface when the object point is moved in the direction.

Here, the object point is moved from a near point position approximately in contact with the imaging lens (approximately 0.01 m position) to a far point position approximately infinitely far from the imaging lens (a position approximately 10 m apart).

Three kinds of curves (solid lines) related to the imaging system of the present invention represented by the series B-1, B-2, and B-3 in FIG. Changes in the value (%) of the MTF characteristic related to the optical image in the same specific region (specific regions with different image heights). In addition, the curves (dotted lines) represented by the series Bw in FIG. 6 represent general changes in the value (%) of the MTF characteristic related to the optical image projected on the light-receiving surface of the conventional imaging system.

As can be seen from FIG. 6 , in the conventional imaging system, the value (%) of the MTF characteristic related to the optical image projected on the light receiving surface 21 varies greatly from 0% to a value exceeding 80%. Furthermore, at the near point where the imaging lens 10 and the object point are close, the object point located in a region closer to the imaging lens 10 than a position where the value of the MTF characteristic becomes 0% (the region where the value of the MTF characteristic is reversed from 0%), produce false resolution. In addition, at the far point where the imaging lens 10 is separated from the object point, false positives also occur for the object point located in a region farther than the position where the value of the MTF characteristic becomes 0% (the region where the value of the MTF characteristic is reversed from 0%). distinguish.

On the other hand, the value (%) of the MTF characteristic related to the optical image projected onto the light-receiving surface 21 by the imaging lens 10 included in the imaging system 100 of the present invention is The size of 10% to 60% does not produce false resolution. That is, regardless of the distance from the imaging lens 10 to the object point and regardless of the position (image height) on the light-receiving surface of the projected optical image, the value of the MTF characteristic related to the projected optical image on the light-receiving surface Changes are reduced and false resolutions are not generated. Furthermore, it can be said that the MTF characteristic related to the optical image projected onto the light receiving surface through the imaging lens 10 from any position in the X, Y, and Z directions, that is, any position in the three-dimensional space, has little variation.

Furthermore, the imaging lens 10 is configured such that the image projected onto the light-receiving surface 21 through the imaging lens 10 is projected from any position in the X, Y, and Z directions that is 10 times or more away from the focal length (for example, 4 to 5 mm) of the imaging lens 10 . The optical image of the subject also makes the value of the MTF characteristic related to the optical image positive.

In addition, in this imaging system 10, the imaging lens and the imaging element are configured, for example, within a range limited to 10f or more in the Z direction and limited to a certain object height in the X and Y directions. A point image projected at an arbitrary position in the X, Y, and Z directions on the light receiving surface has a maximum diameter of an effective area of 3 pixels or more related to the light receiving pixels forming the light receiving surface of the imaging element.

However, the imaging lens 10 is not limited to the case where this condition must be satisfied. If the imaging lens 10 and the imaging element 20 are configured such that a point image projected onto the light-receiving surface 21 through the imaging lens 10 from any position in the X, Y, and Z directions Even if the maximum diameter of the effective area of the point image is set to be 3 pixels or more related to the light receiving pixels on the light receiving surface, the effect of improving the quality of the image data output from the imaging element 20 can be obtained.

As described above, according to the imaging system according to the first embodiment of the present invention, if the resolution of the image represented by the first image data output from the imaging system is insufficient as in the past, it is possible to simply perform restoration processing on only the first image data ( image processing) to be compensated. That is, the second image data representing an image with a predetermined resolution can be obtained by restoring the first image data, so the quality of the image data obtained by photographing the optical image projected on the light receiving surface can be easily obtained. improve.

[About the function of the restoration coefficient acquisition device]

Next, the operation of the restoration coefficient acquisition device 70A will be described in detail.

As a function of the restoration coefficient obtaining device 70A, it is necessary to:

(1) Point image measurement, judging the uniformity in the screen

(2) Deriving the coefficient group (restoration coefficient) that provides the best restoration process

(3) Record the best coefficient group

Each function is explained in more detail.

(1) It is a function of actually measuring and judging the imaging performance (resolution) of the combination of each imaging lens and imaging element. As a mechanism for measuring an optical point image based on an electrical signal (first image data) obtained from an imaging element, there is a commercially available D×O analyzer of French D×O company. It is a mechanism that expresses the so-called B×U blur concept advocated by D×O Corporation, so it is possible to obtain a point image from the output signal from a digital camera (both optical point images and image-processed point images can be obtained) .

Specifically, the D×O analyzer analyzes image data (first image data) obtained by photographing a specified graph (a graph in which countless black dots are arranged on a white background) to calculate the Point image size at an arbitrary point on the light-receiving surface (http://www.dxo.com/jp/image_quality/dxo_analyzer).

Furthermore, the mechanism for measuring an optical point image is not limited as long as it can calculate a point image from an output signal from a digital camera (that is, a sensor).

On the other hand, the size of the point image in the case of following the optical design value can be calculated by a tool for designing the optical system, so by comparing the "design value point image" obtained by this calculation with that obtained by a D×O analyzer, etc. The size of the "measurement point image" measured by the measuring instrument can determine how far the measurement point image deviates from the design value. For example, the size of the measured point image when there is an assembly error in the optical part is likely to be larger than the design value point image. In addition, the shape or luminance distribution of the effective area of the point image projected onto the light-receiving surface of the imaging element is originally a point-symmetrical shape or distribution, but if the imaging lens is tilted or its axis is shifted, front blur and back blur will locally occur, becomes a so-called "single-ambiguity state". By comparing the above-mentioned "design value point image" and "measurement point image", this deviation from the design value can be obtained, and it can be judged whether it can be said to be exactly the design value. In addition, the ideal state can be defined arbitrarily without being limited to the point image of the design value, and the difference between the ideal state ("ideal point image") and the "measured point image" can be judged by comparing it.

(2) Perform the restoration process based on the Kernel Wiener Filter (Kernel Wiener Filter), and calculate the coefficient group that makes the above-mentioned "measured point image" close to the "design value point image" or "ideal point image" (restitution coefficient) stage. Kernel Wiener filter is as shown in the literature (Joyazawa Kaichi, Yukihiko Yamashita, topic "Kernel Wiener Filter", 2003 Workshopon Information-Based Induction Sciences, (IBIS2003), Kyoto, Japan, Nov 11-12, 2003), as When the original signal is observed with noise after some filtering, the technical method of inferring the original signal from the observed signal containing noise is widely used. Here, if the original signal is set as "object to be photographed", the filter is set as "imaging lens + imaging device", the observation signal is set as "image signal (first image data)", and the noise is set as "design value point image (or ideal point image) and the difference between the measured point image", the kernel Wiener filter can be applied to deduce the "object to be photographed".

If the actual "imaging lens+imaging element" has no error causes, then the captured object should be an image signal, and the ideal "image signal (second image data)" in principle is obtained after this restoration process. In fact, there are still measurement errors based on the original (1), and some noise components are not completely removed, but the fact that the measured point image is close to the design value point image or the ideal point image is reliable. As the final image quality is improved.

Specifically, when the optical point image is larger than the design value due to some error reason, or is not uniform in the imaging plane, the point image can also be corrected to be smaller or uniform in the imaging plane through restoration processing, Thereby, practical performance can be ensured. Furthermore, in optical systems that have to have a designed lower performance (the optical point image is larger than the element pitch) not only due to manufacturing errors, the apparent optical performance can also be improved by correcting the point image. Pursuing the improvement of the optical performance in this appearance may exceed the theoretical limit resolution, so it is very useful in consideration of the trend of miniaturization of the pixel size in recent years.

Here, the limiting resolution is given by the size of the Airy disk, and the radius Re of the effective region (peak intensity × (1/e ² )) of the point image intensity of the aberration-free lens and the radius Rc at which the intensity becomes zero are given by the following formula Regulation. The pixel pitch of the latest CMOS element used as an imaging element is 2.2 microns and 1.75 microns, and 1.4 microns and 1.0 microns are expected to become mainstream in the future. As an example, if Re and Rc are calculated with F2.8 and a wavelength of 550nm, they are respectively:

Re (the radius of the effective region of the point image intensity)=0.82λF=0.82×2.8×550×0.001=1.26 microns (the diameter of the effective region of the point image intensity is 2.52 microns)

Rc (the radius at which the point image intensity becomes zero)=1.22λF=1.22×2.8×550×0.001=1.88 microns (the diameter at which the point image intensity becomes zero is 3.76 microns),

And the pixel pitch has exceeded the diffraction limit.

Diffraction limit is based on the premise of no aberration, but the actual optical system is not free of aberration, especially in view of the pursuit of miniaturization and cost reduction, aberrations will remain, and performance has to be compromised. Restoration processing based on the kernel Wiener filter can improve the quality of the final image to a practical level even in this situation.

The above-mentioned restoration process is assumed to be performed on a specific image plane or very close to it (the range of front blur and back blur), but in the countless image plane groups in the defocus direction corresponding to the change of the shooting distance, if we consider Restoration processing that eliminates the difference between the measured point image and the design value point image can expand the depth of focus.

During execution of the restoration process, noise components to be eliminated vary depending on each "imaging lens+imaging element", and it is desirable to perform optimal restoration processing for each combination of "imaging lens+imaging element". However, since the algorithm of the restoration process itself is the same, it is sufficient that the "coefficient group" to be referred to is the best.

(3) is the stage of actually combining the "imaging lens+imaging element" group with the "optimum coefficient group". For this reason, a coefficient group for performing optimal restoration processing should be stored in a certain recording medium and added to the group of "imaging lens+imaging element". Therefore, the process needs to be documented.

In this way, by using the imaging system as a set of "imaging lens + imaging element + recording medium", the optical point image (also called optical point image) is corrected to a form suitable for the application, and finally a good quality image can be obtained. image. Specifically, even if the resolution is not satisfactory due to some reason (manufacturing tolerance, original design value is low), a mechanism that can realize a satisfactory resolution as a processed image is provided. In addition, it is also possible to provide a depth-of-focus expansion mechanism that matches the characteristics of each imaging lens and imaging element set.

[Regarding a modified example of the restoration coefficient acquisition device]

Next, a modified example of the reconstruction coefficient acquisition device will be described.

The restoration coefficient acquisition device that stores the restoration coefficient K1 corresponding to the blurred state of the point image represented by the first image data output from the imaging element in the coefficient storage unit 30 can be configured as follows: 70A is different from the reconstruction coefficient acquisition device 70B of the second example or the reconstruction coefficient acquisition device 70C of the third example described below.

FIG. 7 is a diagram showing a second example of a restoration coefficient acquisition device 70B that stores, in a coefficient storage unit, candidates for each restoration coefficient corresponding to each blurred state of a plurality of types of point images according to The restoration coefficient selected from the blur state of the point image represented by the first image data.

As shown in FIG. 7, the restoration coefficient acquisition device 70B has: a candidate coefficient storage unit 79 storing candidates K1, K2, ... of restoration coefficients corresponding to each blurred state of point images classified into a plurality of types in advance; The blurred state obtaining unit 73 obtains the blurred state of the point image P1 projected onto the light receiving surface 21 through the imaging lens 10; and the restoration coefficient obtaining unit 78B selects the above-mentioned first image among the above-mentioned restoration coefficient candidates K1, K2 . . . The restoration coefficient (for example, K1 ) corresponding to the blur state of the point image P1 represented by the data G1 is stored in the coefficient storage unit 30 .

In the restoration coefficient acquisition device 70B, the blurred point image state data Db representing the blurred state of the point image is obtained by the point image blurred state acquisition unit 73, and the restoration coefficient acquisition unit 78B obtains the restoration coefficient candidates K1, In K2..., a restoration coefficient (for example, K1) corresponding to the blurred state of the point image P1 represented by the blurred point image state data Db is selected, and the coefficient data Dk representing the restoration coefficient K1 is output to the coefficient storage unit 30 for storage.

That is, in the coefficient storage unit 30, the data selected in accordance with the blurred state of the point image represented by the first image data G1 from the candidates K1, K2, ... of restoration coefficients corresponding to the blurred states of the point images divided into a plurality of types are stored. out of the recovery coefficient.

8 is a diagram showing a third example of a restoration coefficient acquisition device 70C that stores, in a coefficient storage unit, candidates for various restoration coefficients corresponding to each blurred state of a point image divided into a plurality of types. Among them, the restoration coefficient selected according to the blur state of the point image represented by the first image data is further the corrected restoration coefficient corrected according to the blur state of the point image.

As shown in FIG. 8, the restoration coefficient acquisition device 70C has: a candidate coefficient storage unit 79 storing candidates K1, K2, ... of restoration coefficients corresponding to each blurred state of point images classified into a plurality of types in advance; The image storage unit 72 stores in advance design data or ideal point image state data related to the ideal point image P1 projected on the light receiving surface 21 through the high-resolution imaging lens 10 when the resolution of the imaging lens 10 is high. Dr; the point image blurred state acquisition unit 73, which acquires the blurred state of the point image P1 projected onto the light-receiving surface 21 through the imaging lens 10; and the restoration coefficient acquisition unit 78C, which is selected from the above-mentioned restoration coefficient candidates K1, K2 . . . The restoration coefficient (such as K1) corresponding to the blurred state of the point image P1, and obtain design data or ideal point image state data representing the blurred state of the point image P1 and the point image pre-stored in the ideal point image storage unit 72 That is, the coefficient data Dk(K1') of the corrected restoration coefficient K1' obtained by correcting the restoration coefficient K1 through the calculation of the data Dr stores the corrected restoration coefficient K1' represented by the coefficient data Dk(K1'). in the coefficient storage unit 30 .

The restoration coefficient acquisition device 70C acquires blur state data representing the blur state of the point image P1 projected onto the light receiving surface 21 through the imaging lens 10 by the point image blur state acquisition unit 73 . The restoration coefficient acquisition unit 78B selects a restoration coefficient (for example, K1 ) corresponding to the blurred state of the point image P1 from the restoration coefficient candidates K1 , K2 . . . stored in the candidate coefficient storage unit 79 . Then, the restoration coefficient K1 obtained by correcting the restoration coefficient K1 is obtained by calculating the data Dr using the blur state of the point image P1 and the point image design data or ideal point image state data previously stored in the ideal point image storage unit 72. The corrected restoration coefficient K1 ′ is stored in the coefficient storage unit 30 .

That is, in the coefficient storage unit 30 is stored: from among the candidates of multiple restoration coefficients corresponding to the respective blurred states of the point images classified into a plurality of types, selected in accordance with the blurred state of the point image P1 represented by the first image data G1 The restoration coefficient (for example K1) of K1 further implements the corrected restoration coefficient K1' corresponding to the above-mentioned correction of the blurred state.

Moreover, as shown in FIG. 9 , the imaging system of the present invention may be such that a restoration coefficient acquisition device 70 or a coefficient storage unit 30 having the same function as the restoration coefficient acquisition device 70A, 70B, or 70C is installed in the housing of the above-mentioned imaging system. camera system 100'.

Moreover, as shown in FIG. 10 , the imaging system of the present invention may also be an imaging system 100 ″ provided with a signal processing unit 40 ′ incorporating the restoration coefficient obtaining device 70 or the coefficient storage unit 30. That is, the signal processing unit 40 may be ' doubles as the restoration coefficient acquisition means 70.

[About modifications of each component]

Next, modified examples of constituent elements of the imaging system will be described.

The signal processing unit is not limited to the case of performing restoration processing on the light-receiving surface with a pixel area consisting of more than 3 pixels in the vertical direction and more than 3 pixels in the horizontal direction involving a total of 9 pixels or more as the minimum unit. The composed pixel area involving less than 9 pixels in total is used as the minimum unit for restoration processing.

In addition, the signal processing unit is not limited to the case of calculating the restoration coefficient by using the first image data indicating the blurred state of the point image, and may obtain the restoration coefficient by other methods.

In addition, the signal processing unit is not limited to the case where the smallest pixel area including the entire effective area of the point image projected on the light receiving surface is used as the minimum unit to perform the restoration process, and the smallest pixel area including the entire effective area may be used as the smallest pixel area. The unit performs recovery processing.

Furthermore, the signal processing unit is not limited to the case where the restoration process is performed so that the size of the effective area of the point image in the image represented by the second image data is smaller than the size of the effective area of the point image in the image represented by the first image data, and The restoration process may be performed so that the size of the effective area of the point image in the image represented by the first image data is greater than or equal to the size of the effective area of the point image in the image represented by the second image data.

(second embodiment)

FIG. 11 is a block diagram showing a schematic configuration of an imaging system according to a second embodiment of the present invention.

[About the structure of the camera system]

Hereinafter, the configuration of the imaging system of the second embodiment will be described.

The imaging system 200 of the present invention shown in Figure 11 has: imaging lens 10; The optical image P1 of the object is taken, and the first image data G1 representing the object is output; the coefficient storage unit 30, the maximum diameter of the effective area of the point image projected onto the light receiving surface 21 by the imaging lens 10 is related to 3 When the size is larger than a pixel, the restoration coefficient K corresponding to the blurred state of the point image P1 represented by the first image data G1 output from the imaging element 20 is stored; and the signal processing unit 40 uses the restoration coefficient stored in the coefficient storage unit 30 K performs restoration processing on the first image data G1 to generate second image data G2 equivalent to the first image data G1 output from the imaging element 20 when the resolution of the imaging lens 10 is high.

The signal processing unit 40 executes the restoration process F with a pixel region involving a total of 9 or more pixels consisting of 3 or more pixels in the vertical direction and 3 or more pixels in the horizontal direction on the light receiving surface 21 as a minimum unit.

The configuration of the imaging lens 10 is the same as that of the first embodiment described above.

Here, the maximum diameter of the effective area of the point image P1 projected on the light receiving surface 21 is the diameter of the effective area in the direction in which the effective area of the point image P1 projected on the light receiving surface 21 includes the most light receiving pixels.

The direction indicated by arrow Z in FIG. 11 is the optical axis direction of the imaging lens 10 , and the directions indicated by arrows X and Y are directions parallel to the light receiving surface 21 .

Here, the restoration coefficient acquisition device 70A provided outside the imaging system 100 acquires the restoration coefficient K corresponding to the blur state of the point image P1 represented by the first image data G1 output from the imaging element 20, and stores it in the coefficient storage unit 30. The restoration factor K.

This restoration coefficient obtaining device 70A has: an ideal point image storage unit 72, which stores in advance design data related to the point image when there is no error in the optical system including the imaging lens 10 or related to the state of the ideal point image superior to it. Any one of the data Dr in the ideal point image state data; the point image blur state acquisition part 73 analyzes the blur state of the point image represented by the first image data G1 output from the imaging element 20 and obtains a value representing the analysis result. Fuzzy point image state data Db; point image diameter acquisition part 74, used to obtain the maximum diameter of the point image P1 effective area projected onto the light-receiving surface 21 through the imaging lens 10; judging part 76, judged by the point image diameter acquisition part 74 Whether or not the above-mentioned maximum diameter of is related to the size of 3 pixels or more on the light receiving surface 21; From the blurred point image state data Db output from the point image blurred state acquisition part 73, and the design data or ideal point image state data stored in the ideal point image storage part 72, that is, the data Dr, and the operation using both of them is used to obtain a representation. The coefficient data Dk of the restoration coefficient K corresponding to the blurred state of the point image P1 indicated by the first image data G1 is stored in the coefficient storage unit 30 .

[About the role of the camera system]

Next, the operation of the imaging system described above will be described.

First, an example in which the restoration coefficient is obtained by the restoration coefficient acquisition device and the restoration coefficient is stored in the coefficient storage unit will be described.

The optical image of the subject projected onto the light receiving surface 21 through the imaging lens 10 is captured by the imaging element 20, and the first image data G1 representing the subject output from the imaging element 20 is input to the point image blurred state acquisition unit 73. And the point image diameter acquisition unit 74.

The point image blurred state acquisition unit 73 that receives the first image data G1 analyzes the blurred state of the point image represented by the first image data G1 and outputs blurred point image state data Db indicating the analysis result.

Further, the point image diameter acquisition unit 74 that receives the first image data G1 obtains the maximum diameter of the effective area of the point image P1 projected on the light receiving surface 21 and outputs diameter data Dm indicating the maximum diameter. The judging section 76 having input the diameter data Dm representing the above-mentioned maximum diameter judges whether the maximum diameter of the effective area of the point image P1 is a size involving 3 pixels or more on the light receiving surface 21, and when it is judged that the maximum diameter is 3 pixels or more. When the size is large, the signal Te is output.

The restoration coefficient acquisition unit 78A having received the signal Te receives the blurred point image state data Db output from the point image blurred state acquisition unit 73 and the design data or ideal point image state data previously stored in the ideal point image storage unit 72 . Dr, obtains the restoration coefficient K corresponding to the blurred state of the point image P1 through the calculation using both, and outputs the coefficient data Dk representing the restoration coefficient K.

The coefficient data Dk output from the restoration coefficient acquisition unit 78A is input to the coefficient storage unit 30 , and the restoration coefficient K indicated by the coefficient data Dk is stored in the coefficient storage unit 30 .

Furthermore, as an example of realizing the function of the point image blurred state acquisition unit 73, a D×O analyzer (analyser) manufactured by D×O Labs (France), which will be described later, is mentioned. According to this D×O analyzer, by analyzing the first image data G1 output from the imaging element 20, the blur state (deterioration state of resolution) or the effective area of the point image P1 on the projection light receiving surface 21 can be obtained. of the maximum diameter.

As described above, by storing the restoration coefficient K in the coefficient storage unit 30 , the imaging system 100 is in a state where restoration processing can be performed.

[about restoration processing]

A method of performing restoration processing F on the first image data output from the imaging element 20 using the restoration coefficient K stored in the coefficient storage unit 30 to obtain second image data of an image having a higher resolution than the image represented by the first image data, The same method as that of the above-mentioned first embodiment can be adopted.

[Regarding a modified example of the restoration coefficient acquisition device]

Next, a modified example of the reconstruction coefficient acquisition device will be described.

The restoration coefficient acquisition device that stores the restoration coefficient K1 corresponding to the blurred state of the point image represented by the first image data output from the imaging element in the coefficient storage unit 30 may be configured as the restoration coefficient acquisition device 70A of the first example above. The difference is the reconstruction coefficient acquisition device 70B of the second example or the reconstruction coefficient acquisition device 70C of the third example described below.

FIG. 12 is a diagram showing a restoration coefficient acquisition device 70B of a second example, and FIG. 13 is a diagram showing a restoration coefficient acquisition device 70C of a third example. FIG. 14 is a diagram showing an imaging system including a restoration coefficient acquisition device, and FIG. 15 is a diagram showing an imaging system including a restoration coefficient acquisition device and a coefficient storage unit in a signal processing unit. In FIGS. 12 to 15 , components having the same functions as those of the restoration coefficient acquisition apparatus 70A of the first example above are denoted by the same symbols as in the case of the restoration coefficient acquisition apparatus 70A of the first example.

As shown in FIG. 12 , the restoration coefficient acquisition device 70B of the second example includes a candidate coefficient storage unit 79 storing candidates K1, K2, . The point image blurred state acquisition part 73 analyzes the blurred state of the point image represented by the first image data G1 output from the imaging element 20 and obtains the blurred point image state data Db representing the analysis result to the restoration coefficient described later. Obtaining part 78B output; Point image diameter obtaining part 74 is used to obtain the maximum diameter of the effective area of the point image P1 projected on the light receiving surface 21 through the imaging lens 10; Whether the above-mentioned maximum diameter is related to the size of 3 pixels or more on the light receiving surface 21; Among the restoration coefficient candidates K1 , K2 .

The restoration coefficient acquisition device 70B acquires the maximum diameter of the effective area of the point image P1 projected onto the light receiving surface 21 through the imaging lens 10 by the point image diameter acquisition unit 74 , and outputs diameter data Dm indicating the maximum diameter to the determination unit 76 . The judging section 76 having received the diameter data Dm judges whether or not the above-mentioned maximum diameter is related to the size of 3 pixels or more on the light receiving surface 21. Section 78B output. The restoration coefficient acquisition unit 78B to which the signal Te is input selects a restoration coefficient corresponding to the blurred state of the point image P1 represented by the blurred point image state data Db above from the candidates K1, K2, . . . of the restoration coefficient stored in the candidate coefficient storage unit 79 ( For example, K1), the coefficient data Dk representing the restored coefficient K1 is output to and stored in the coefficient storage unit 30 .

That is, in the coefficient storage unit 30, the data selected in accordance with the blurred state of the point image represented by the first image data G1 from the candidates K1, K2, ... of restoration coefficients corresponding to the blurred states of the point images divided into a plurality of types are stored. The recovery coefficient (such as K1) is obtained.

On the other hand, as shown in FIG. 13 , the restoration coefficient acquisition device 70C of the third example includes a candidate coefficient storage unit 79 storing candidates for restoration coefficients corresponding to blur states of point images classified into a plurality of types in advance. K1, K2...; the ideal point image storage unit 72 stores in advance design data or ideal point images related to the ideal point image projected onto the light receiving surface 21 through the high-resolution imaging lens 10 when the resolution of the imaging lens 10 is high. The point image state data is the data Dr; the point image blurred state acquisition unit 73 analyzes the blurred state of the point image represented by the first image data G1 output from the imaging element 20 and obtains the blurred point image state data Db representing the analysis result. And output to the restoration coefficient acquisition part 78C described later; The point image diameter acquisition part 74 is used to obtain the maximum diameter of the effective area of the point image P1 projected on the light receiving surface 21 through the imaging lens 10; Whether or not the above-mentioned maximum diameter obtained by the point image diameter obtaining unit 74 has a size of 3 pixels or more on the light receiving surface 21 is involved.

Furthermore, this restoration coefficient acquisition device 70C has a restoration coefficient acquisition unit 78C that, when it is determined by the determination unit 76 that the maximum diameter is related to a size of 3 pixels or more on the light-receiving surface 21 , calculates the maximum diameter from the above-mentioned restoration coefficient. Candidates K1, K2, ... select a restoration coefficient (for example, K1) corresponding to the blurred state of the point image P1 represented by the blurred point image state data Db output from the point image blurred state acquisition unit 73, and acquire the The calculation of the image state data Db and the design data of the point image or the ideal point image state data stored in the ideal point image storage unit 72 in advance, that is, the data Dr, corrects the restoration coefficient K1 and corrects the restoration coefficient K1'. The coefficient data Dk ( K1 ′) stores the corrected restoration coefficient K1 ′ represented by the coefficient data Dk ( K1 ′) in the coefficient storage unit 30 .

In this restoration coefficient acquisition device 70C, the point image diameter acquisition unit 74 acquires the maximum diameter representing the effective area of the point image P1 projected onto the light receiving surface 21 through the imaging lens 10, and outputs diameter data Dm representing the maximum diameter to the determination unit 76. . The judging section 76 having input the diameter data Dm judges whether the above-mentioned maximum diameter is related to a size of 3 pixels or more on the light receiving surface 21. The restoration coefficient acquisition unit 78B outputs. The restoration coefficient acquisition unit 78B having received the signal Te selects a restoration coefficient corresponding to the blurred state of the point image P1 represented by the aforementioned blurred point image state data Db from the restoration coefficient candidates K1, K2, . . . stored in the candidate coefficient storage unit 79 ( For example, K1), the restoration coefficient K1 is further performed by calculating the design data or the ideal point image state data that is data Dr using the above-mentioned blurred point image state data Db and the point image stored in the ideal point image storage unit 72 in advance. The corrected restoration coefficient K1 ′ is corrected, and the corrected restoration coefficient K1 ′ is stored in the coefficient storage unit 30 .

That is, the coefficient storage unit 30 stores: among the candidates of multiple types of restoration coefficients corresponding to the respective blurred states of the point images divided into a plurality of types, selected in accordance with the blurred state of the point image P1 represented by the first image data G1 The restoration coefficient (for example K1) further implements the corrected restoration coefficient K1' corresponding to the correction of the aforementioned blur state.

Furthermore, the imaging system 200 may include the restoration coefficient acquisition devices 70A, 70B, and 70C as a part thereof, or may be formed without any of the restoration coefficient acquisition devices 70A, 70B, and 70C.

In addition, an imaging system 200' shown in FIG. 14 is an imaging system in which a restoration coefficient acquisition device 70 having the same function as a restoration coefficient acquisition device 70A, 70B, or 70C is incorporated in the housing of the imaging system. The camera system can be structured like this.

Furthermore, the imaging system 200" shown in FIG. 15 is an imaging system in which the above-mentioned restoration coefficient acquisition device 70 and the coefficient storage unit 30 are incorporated in the signal processing unit 40'. The imaging system may also be configured in this way.

[About the performance of the camera system]

Next, the imaging system composed of the imaging lens 10 and the imaging lens 20 used in the imaging system 200 can have performance equivalent to that of the first embodiment described above.

As described above, according to the imaging system according to the second embodiment of the present invention, when the resolution of the image represented by the first image data output from the imaging system does not reach a predetermined level as in the past, it is not necessary to identify the cause and readjust or readjust. By assembling an imaging lens, etc., simply storing a restoration coefficient corresponding to the blur state of a point image in the coefficient storage section and performing restoration processing on the first image data, a second image representing an image having a predetermined resolution can be obtained. Therefore, the quality of the image data obtained by shooting the optical image projected on the light-receiving surface can be easily improved. In addition, it can also be said that the lack of resolution of the imaging system can be easily recovered.

[About modifications of each component]

Next, modifications of the constituent elements of the imaging system of the second embodiment will be described.

In addition, the signal processing unit is not limited to the case where the minimum pixel area including all effective areas of the point image projected on the light receiving surface is used as the minimum unit to perform the restoration process, and the minimum unit may be a pixel area that includes all effective areas but is not the smallest. Execute recovery processing.

Furthermore, the signal processing unit is not limited to the case where the restoration process is performed so that the size of the effective area of the point image in the image represented by the second image data is smaller than the size of the effective area of the point image in the image represented by the first image data, and The restoration process may be performed so that the size of the effective area of the point image in the image represented by the first image data is greater than or equal to the size of the effective area of the point image in the image represented by the second image data.

Moreover, the imaging device of the present invention equipped with the above-mentioned imaging system, portable terminal equipment, vehicle-mounted equipment, and medical equipment, etc. require depth of field devices, which can easily improve the imaging system equipped in each device. Projected to the light-receiving surface The quality of the image data obtained by taking the optical image.

Moreover, in the imaging system of the present invention, the imaging lens and the imaging element can be configured such that, for example, they are limited to more than 10f with respect to the Z direction, and are also limited to a certain object height with respect to the X and Y directions. The point image projected onto the light-receiving surface at any position in the Y, Z directions, the maximum diameter of the effective area of the point image also becomes the size of 3 pixels or more related to the light-receiving pixels forming the light-receiving surface of the imaging element.

In addition, the imaging lens is preferably configured such that the optical image of the subject projected onto the light-receiving surface through the imaging lens from any position in the X, Y, and Z directions that is more than 10 times the focal length of the imaging lens is compatible with the optical image. Like the value of the related MTF characteristic becomes positive. Furthermore, "a position away from the focal length of the imaging lens by more than 10 times" means "taking the position where the surface closest to the object side among the lens surfaces constituting the imaging lens intersects the optical axis of the imaging lens as a reference position, from The reference position is at least 10 times the focal length away from the subject side along the optical axis direction (Z-axis direction) of the imaging lens".

And, with regard to this imaging system, the imaging lens and the imaging element may also be configured such that only the point image projected onto the light-receiving surface through the imaging lens from a position limited in at least any direction about the X, Y, and Z directions is used. The maximum diameter of the effective area of the point image is 3 or more pixels related to the light-receiving pixels forming the light-receiving surface. In this case, the second image data can be obtained by performing restoration processing only on the first image data representing an area in which the maximum diameter of the effective area of the point image projected on the light receiving surface is the size of 3 pixels related to the light receiving pixel. .

The imaging device, portable terminal equipment, vehicle-mounted equipment, medical equipment, etc. of the present invention, equipped with the imaging system of the above-mentioned first embodiment or second embodiment, can easily improve the projection effect similarly to the above. The quality of the image data obtained by capturing the optical image on the light-receiving surface of the imaging system included in each device.

Furthermore, the imaging systems of the first and second embodiments of the present invention may be configured to project the optical image of the subject onto the light receiving surface only by optical components having an axisymmetric shape, or may be configured by The optical image of the subject is projected onto the light-receiving surface by an optical component composed of a non-axisymmetric shape. Furthermore, the above imaging lens is preferably a lens with a deep field of view. That is, it is preferable to configure the imaging lens and the imaging element so that even if the state of the optical image of the object projected on the light receiving surface changes due to the movement of the object or the focus adjustment of the imaging lens, it is possible to make the projected image on the light receiving surface change. Changes in the blur state of point images on a surface are reduced. More specifically, the imaging lens and the imaging element are configured to reduce variations in the size and contrast of an effective area of a point image projected on a light receiving surface. However, the imaging system is not limited to the case of including an imaging lens with a deep depth of field, and may include an imaging lens with a shallow depth of field.

In addition, the imaging element used for the imaging system of the said 1st Embodiment and 2nd Embodiment may be a CCD element or a CMOS element.

[About the manufacturing method of the camera system]

11, 12, 13, etc., to describe the manufacturing method of the imaging system of the present invention, that is, the method of manufacturing the imaging system with the stored restoration coefficient by storing the predetermined restoration coefficient for the imaging system without storing the predetermined restoration coefficient.

This imaging system manufacturing method is a method of storing restoration coefficients in the coefficient storage unit 30 to manufacture imaging systems 200A, 200B, .

Furthermore, the imaging systems 200A, 200B, ... are the same systems as the imaging system 200 already described with reference to FIGS. 11 to 15 .

The manufacturing method of the above-mentioned imaging system is the manufacturing method of the imaging system 200A, 200B..., the imaging system has: an imaging lens 10; 10 project the optical image of the object on the light receiving surface 21 to output the first image data G1 representing the object; the signal processing unit 40 will be composed of more than 3 pixels in the vertical direction and more than 3 pixels in the horizontal direction on the light receiving surface 21. A restoration process for generating second image data G2 equivalent to the first image data G1 output from the imaging element 20 when the resolution of the imaging lens 10 is high is performed on the first image data G1 with a pixel area of 9 pixels or more in total as the minimum unit. F; and a coefficient storage section 30 storing a restoration coefficient K for restoration processing; the imaging system executes restoration processing using the restoration coefficient K stored in the coefficient storage section 30 .

In this manufacturing method, the point image P1 is projected onto the light receiving surface 21 through the imaging lens 10, and the restoration coefficient K corresponding to the state of the point image P1 represented by the first image data G1 output from the imaging element 20 is stored in the coefficient storage unit 30. .

The manufacturing method of this imaging system employs the restoration coefficient obtaining device 70A of the first example, the restoration coefficient obtaining device 70B of the second example, or the restoration coefficient obtaining device 70C of the third example of the second embodiment to obtain the restoration coefficient and This restoration coefficient is stored in the coefficient storage unit of each imaging system 200A, 200B, . . .

Hereinafter, a method of manufacturing an imaging system using the restoration coefficient acquisition device 70A of the first example, the restoration coefficient acquisition device 70B of the second example, and the restoration coefficient acquisition device 70C of the third example will be specifically described. Furthermore, the structures and functions of the imaging systems 100A, 100B... and the restoration coefficient acquisition device 70A of the first example, the restoration coefficient acquisition device 70B of the second example, and the restoration coefficient acquisition device 70C of the third example are similar to those described above. Since the content related to the imaging system 100 is the same, overlapping descriptions will be omitted, and the content of the manufacturing method of the imaging system that does not overlap with the description of the imaging system 100 described above will be described.

"Regarding the manufacturing method of the imaging system corresponding to the restoration coefficient acquisition device 70A of the first example"

In the "1-to-1" manufacturing process of storing the restoration coefficients obtained individually for each camera system in the camera system, it is necessary to:

(1) Point image measurement, judging the uniformity in the screen,

(2) deriving the coefficient set (restoration coefficient) that provides the best restoration process,

(3) Record the best coefficient group.

As each function, the function described in "Action of the restoration coefficient acquisition device" of the above-mentioned first embodiment can be applied.

"Regarding the manufacturing method of the imaging system corresponding to the restoration coefficient acquisition device 70B of the second example"

A second preferred method of manufacturing the above-mentioned point image correction optical system composed of an imaging lens, an imaging element, and a signal processing circuit will be described, but as its positioning, it is assumed that a large number of digital cameras are produced at low cost. In its manufacturing process, it needs to carry out:

(1) Constructing a library of coefficients (restoration coefficients) groups for restoration processing,

(2) Point image measurement, judging the uniformity in the screen,

(3) extracting from the library the coefficient group that provides the best restoration process in group units,

(4) Record the optimal coefficient group in group units.

Each function will be described in more detail.

(1) The number of imaging lenses (for example, 1/10 of all lot numbers) that can capture the overall trend is measured in advance, and the resolution trends (defective trends) are grouped. The optimal restoration process for each group is calculated, and the optimal coefficient group for each group unit is calculated to construct a library. Ideally, as in the first example, it would be ideal to associate the allocation coefficient groups "1:1", but it is not suitable for mass production or when costs are to be suppressed. Therefore, as in the present embodiment, the whole is divided into groups to some extent, and a library for obtaining the optimal solution in units of the groups is created.

(2) It is the same as (1) of the first example, however, it is judged which group it belongs to in the above-mentioned second example (1) based on the measurement point image. Actually, when the above-mentioned grouping is performed, those other than those measured in advance are also assigned to groups (for example, 9/10 of all lot numbers).

(3) is a step of extracting the optimal coefficient group of the group determined in (2) above from the library, and the selected coefficient group is applied to the group of "imaging lens+imaging element". At this time, the optimal coefficient group for each "imaging lens+imaging element" group is not calculated one by one. Accordingly, the calculation time required for the first example can be shortened, and mass production can be achieved at low cost.

(4) is the same as (3) of the first example.

"Regarding the manufacturing method of the imaging system corresponding to the restoration coefficient acquisition device 70C of the third example"

A third preferred method of manufacturing the above-mentioned point image correction optical system composed of an imaging lens, an imaging element, and a signal processing circuit will be described, but as its orientation, it is assumed that a large number of digital cameras are produced at low cost. In its manufacturing process, it needs to carry out:

(1) Constructing a library of coefficients (restoration coefficients) groups for restoration processing,

(2) Point image measurement, judging the uniformity in the screen,

(3) Extract the coefficient group that provides the best restoration process from the library,

(4) partially modify the coefficient group,

(5) Record the modified coefficient group.

Each function will be described in more detail.

(1)(2)(3) are the same as (1)(2)(3) in the second example.

(4) is a process of partially modifying the extracted coefficient group. The coefficient group is an array of certain numerical values, but a necessary modification is made to the "imaging lens+imaging element" in which only a part of it is modified. Unlike the above-mentioned first example in which all coefficient groups are optimized, only a part of the coefficients is modified, so it only needs to be short in time.

(5) is a stage of recording the modified corrected coefficient group, whereby a group of "imaging lens+imaging element+recording medium" is constituted.

As mentioned above, the imaging system manufactured by the manufacturing method of the imaging system of this invention can improve the quality of the image data obtained by imaging the optical image projected on the light receiving surface easily.

[About the lens structure and function of the camera lens]

Next, the configuration and operation of the imaging system of Embodiment 1 used in the imaging systems 100 and 200 described above will be described in detail. An imaging lens 10A, which will be described later, and the like used in the imaging system of the first embodiment described above are examples of the imaging lens 10 described above.

Furthermore, as will be described later, the imaging lens 10 includes, in order from the subject side (object side), the first lens group G-1 consisting of at least one lens and having positive refractive power, consisting of at least one lens The second lens group G-2 is composed of lenses and has negative refractive power, and the third lens group G-3 is composed of at least one lens and the lens on the most image side has positive refractive power.

"About the Camera System of Embodiment 1"

16 is a cross-sectional view showing a schematic configuration of an imaging lens 10A composed of three single lenses according to Embodiment 1, and FIGS. On the coordinates of the defocus amount Ud (μm) in the optical axis direction (Z-axis direction) of the light-receiving surface and the value (%) of the MTF characteristic on the vertical axis, it shows that when the light-receiving surface is defocused with respect to the above-mentioned imaging lens, the projected A graph showing changes in the value (%) of the MTF characteristic of the optical image on the light receiving surface. Here, the defocus range of the light receiving surface 21A is 400 μm.

More specifically, FIGS. 17( a ) to ( d ) above show optical images projected at various image heights when the light receiving surface 21A is defocused while the position of the subject relative to the imaging lens 10A is fixed. Graphs of changes in the value (%) of the MTF characteristic. Fig. 17 (a) is a figure showing the change of the value of the MTF characteristic of the spatial frequency of 20 / mm, Fig. 17 (b) is a figure showing the change of the value of the MTF characteristic of the spatial frequency of 30 / mm, Fig. 17 17( d ) is a graph showing changes in the MTF characteristic value at a spatial frequency of 50 lines/mm.

Furthermore, the direction in which the value of the horizontal axis Ud indicating the amount of defocus in FIG. 0) indicates the direction in which the light-receiving surface and the imaging lens approach.

As shown in FIG. 16, in the imaging lens 10A, aperture stops Sat, corresponding to the first lens group G-1 The first single lens La1, the second single lens La2 corresponding to the second lens group G-2, the third single lens La3 corresponding to the third lens group G-3, and the optical component GLa1. In addition, lens surfaces R1, R3, and R5 shown in FIG. 16 represent incident-side surfaces of the single lenses La1 to La3, respectively, and lens surfaces R2, R4, and R6 respectively represent exit-side surfaces of the single lenses La1 to La3. The optical image of the subject is projected onto the light receiving surface 21A through the imaging lens 10A.

Furthermore, on the subject side of the light receiving surface 21A, it is preferable to arrange a cover glass, a low-pass filter, an infrared cut filter, etc. depending on the configuration of the imaging system, and FIG. Example of an optic GLa1 with no optical power. In addition, the aperture stop Sat does not indicate the shape or size but the position on the optical axis Z.

In addition, in Fig. 16, from the on-axis ray Ja1 to the off-axis ray Ja7 incident at the maximum viewing angle, seven rays Ja1, Ja2, Ja3, Ja4, Ja5, Ja6, and Ja7 are shown sequentially from the side of the image height. .

The seven MTF curves Mta20 shown in FIG. 17( a ) represent changes in the value of the MTF characteristic at a spatial frequency of 20 rays/mm at each position where the above-mentioned seven light rays are projected onto the light receiving surface 21A. The seven MTF curves Mta30 described in FIG. 17( b ) represent changes in the value of the MTF characteristics at the spatial frequency of 30 wires/mm at the same positions as above, and the seven MTF curves described in FIG. 17( c ) Mta40 also shows the change in the value of the MTF characteristic at the spatial frequency of 40/mm at the same positions as above, and the seven MTF curves Mta50 described in FIG. 17( d) also show the values at the same positions as above. Changes in the value of the MTF characteristic at a spatial frequency of 50 threads/mm.

In addition, in the configuration example shown in FIG. 16 , an example in which the optical component GLa1 is arranged between the third single lens La3 and the light receiving surface 21A is shown, but a low-pass filter or a cutoff filter may be arranged between each lens. Various filters for different bands. Alternatively, surface treatment (coating) having the same function as various filters may be applied to the lens surface of any lens from the first single lens La1 to the third single lens La3.

This imaging lens 10A has, in order from the object side, a single lens La1 which is a first lens group G-1 having a positive refractive power; a single lens La2 which is a second lens group G-2 which has a negative refractive power; and a single lens La2 which has a negative refractive power. The third lens group G-3 with positive refractive power is a single lens La3; the lens surface R6 on the image side corresponding to the single lens La3 of the third lens group G-3 has an off-axis inflection point Qa.

Furthermore, as described above, a curved point is a point on the lens surface, and when the tangent plane of this point is perpendicular to the optical axis C (Z axis), this point is called a curved point. In addition, inflection points other than the point intersecting the optical axis on the lens surface are referred to as off-axis inflection points.

In this imaging lens 10A, the lens surface R6 of the third lens group closest to the image side is a lens surface that is concave toward the image side at the center of the lens surface R6 and convex toward the image side at the peripheral portion. And this lens surface R6 satisfies the following conditional expression (1).

0.5H<h<H...(1)

in,

H: effective radius of lens surface R6

h: the distance from the off-axis inflection point Qa of the lens surface R6 to the optical axis.

In addition, the distance h from the off-axis inflection point Qa of the lens surface R6 to the optical axis is also referred to as a point on the aspheric surface where the inclination of the tangent plane to the vertex of the aspheric surface (the plane perpendicular to the optical axis) becomes zero. height from the optical axis.

Furthermore, as for the single lens La3 which is the lens located closest to the image side of the third lens group G-3 of this imaging lens 10A, the lens surface R5 on the object side is convex toward the object side at the center of the lens surface R5, and the peripheral portion Concave toward the object side.

The single lens La1 constituting the first lens group G-1 has a meniscus shape with a convex surface facing the object side, and the single lens La2 constituting the second lens group G-2 has a meniscus shape with a convex surface facing the image side.

Hereinafter, design data of the imaging lens 10A according to the first embodiment will be described.

Table 1 shows lens data and various data, Table 2 shows each coefficient of the aspheric formula on each aspheric surface, and Table 3 shows a brief specification of the imaging lens 10A.

[Table 1]

Embodiment 1 (three lenses)

face number Ri Di Ndj vdj Aperture stop ∞ -0.070 1* 1.060 0.672 1.47136 77.6 2* 2.298 0.799 3* -2.168 0.570 1.60595 27.0 4* -5.366 0.250 5* 1.313 0.690 1.53159 55.4 6* 1.429 0.500 7 ∞ 0.300 1.51633 64.1 8 ∞ 0.522 Image surface ∞ 0.000

Focal length 3.847

F value 3.5

[Table 2]

Embodiment 1 (three lenses)

face number K A3 A4 A5 A6 1 1.67530380 -0.01932744 -0.02985018 -0.12489137 -0.01225001

2 8.15043250 0.03605327 -0.04792006 0.11130041 0.31864904 3 1.98987400 -0.01691895 -0.02882516 -0.04157052 -0.10622967 4 -22.94585750 -0.28231890 0.08051906 -0.04346302 0.03066265 5 -2.24143450 -0.32245902 -0.01054630 0.05102366 0.02042473 6 -3.33611150 -0.08863879 -0.10108346 0.07800228 -0.00239551

face number A7 A8 A9 A10 1 0.27595695 0.10620366 -0.67945287 -0.08377876 2 -0.16205189 -0.29792806 -1.71742400 2.93183590 3 -0.03383005 0.12327341 0.25461410 -0.35326388 4 -0.01891840 0.01135644 0.02101196 -0.01119125 5 -0.01256704 -0.00258553 0.00610633 -0.00217838 6 -0.01183056 -0.00321420 0.00422294 -0.00081224

[table 3]

Example 1 F value 3.5/focal length 3.847mm 3-chip structure

As shown below the lens data in Table 1, the focal length f of the imaging lens 10A is 3.847 mm, and the F value is 3.5.

In the lens data in Table 1, the surface number indicates the i-th (i=1, 2, 3, ...) surface that increases sequentially toward the image side with the lens surface closest to the subject side as the first Number. In addition, Table 1 also includes descriptions of the aperture stop Sat and the optical component GLa1, and also describes the surface number (i=7, 8) of the optical component GLa1.

Ri in Table 1 represents the paraxial radius of curvature of the i-th (i=1, 2, 3, ...) surface, and Di represents the i-th (i=1, 2, 3, ...) surface and the i+1 Surface spacing on the optical axis Z of the surface. Ri in Table 1 corresponds to symbols Ri (i=1, 2, 3, . . . ) in FIG. 16 .

Ndj in Table 1 represents the first optical factor on the side closest to the subject, and the jth (j=1, 2, 3, ...) optical factor that increases sequentially toward the image side versus the d-line (wavelength 587.6nm), vdj represents the Abbe number of the jth optical factor to the d line. In Table 1, the unit of the paraxial curvature radius and the surface distance is mm, and the paraxial curvature radius is defined as positive when it is convex on the subject side (object side), and negative when it is convex on the image side. .

In the lens data in Table 1, aspherical surfaces are marked with * in the surface number. Each aspherical surface is defined by the following aspheric surface formula.

[mathematical formula 1]

$\mathrm{<span\; class="notranslate">\; Z</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="A200810179823E00621.png,A200810179823E00631.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="A200810179823E00591.png,A200810179823E00611.png"\; state="\{\{state\}\}">R</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Y"\; filenames="A200810179823E00621.png,A200810179823E00631.png"\; state="\{\{state\}\}">Y</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 3</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 20</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; Ai</span>}{\mathrm{<span\; class="notranslate">\; Y</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}$

Z: Depth of the aspheric surface (the length of a vertical line sagging from a point on the aspheric surface of height Y to a plane perpendicular to the optical axis tangent to the apex of the aspheric surface)

Y: height (distance from optical axis)

R: paraxial radius of curvature

K, Ai: Aspheric coefficient (i=3～20)

Table 2 shows the values of coefficients K, A3, A4, A5... of each aspheric surface in the aspheric surface formula.

Each of the single lenses La1 to La3 constituting the imaging lens 10A has an aspherical shape on both the incident side and the outgoing side lens surfaces.

In addition, Table 3 shows the maximum diameter Dmax of the effective area of the point image in the imaging system of Example 1, the number of pixels (the number of pixel regions) Ngs corresponding to the maximum diameter Dmax of the effective area of the point image, the shortest photographic The relationship between distance Sk and focal depth Sd.

In addition, "h" in the column of "h: H/2" in Table 3 represents the distance from the optical axis to the off-axis inflection point of the above-mentioned lens surface R6. In addition, "H/2" shows the magnitude|size of 1/2 of the effective radius H of the lens surface R6 (the magnitude|size of 0.5H). Here, it can be seen that the lens surface R6 satisfies the above-mentioned conditional expression (1) of “0.5H<h<H”.

In addition, the number of pixels Ngs in Table 3 shows the number of pixel regions corresponding to the maximum diameter of the effective region of the point image per pixel pitch Pg (2.2 μm, 1.85 μm, 1.4 μm) of the pixel region on the light receiving surface . Here, the value of the number of pixels Ngs is obtained from the formula: number of pixels Ngs=maximum diameter Dmax/pixel pitch Pg.

The maximum diameter Dmax of the effective area of the above-mentioned point image is the diameter of the effective area of the point image on the direction in which the effective area of the point image contains the most pixels, and the pixel pitch Pg is the pitch of the pixel area (light-receiving pixel) on the above-mentioned direction. distance.

The shortest imaging distance Sk is a recommended value when the imaging lens is used in practical use, and represents the shortest distance from the imaging lens capable of projecting an image of the object with a desired resolution onto the light receiving surface to the object. The shortest distance is represented by the distance (photographic distance) from the lens surface (here, lens surface R1 ) closest to the subject side (object side) of the imaging lens to the subject.

The shortest imaging distance is included in the range of imaging distance that can obtain the effect of improving the quality of image data obtained by imaging the optical image projected on the light receiving surface through restoration processing.

Furthermore, in the image pickup system of Embodiment 1, the range of shooting distance that can obtain the effect of improving the quality of image data through restoration processing is the range of shooting distance 0 to ∞ (infinity), which is the range where the subject can be photographed. the whole range.

The depth of focus Sd indicates the defocused range within which an image of the subject can be projected on the light receiving surface with a resolution greater than or equal to a predetermined resolution when the light receiving surface is defocused while the position of the subject relative to the imaging lens is fixed. The depth of focus Sd is considered to be a value corresponding to a range of photographic distances capable of projecting an object on the light receiving surface with a predetermined resolution in a state where the position of the light receiving surface imaging lens is fixed at a predetermined position. . That is, as the value of the depth of focus Sd increases, it can be considered that the range of imaging distance for projecting an object on the light receiving surface with a predetermined resolution also increases.

As can be seen from Table 3, the imaging system of Embodiment 1 is configured such that when the effective area of the point image projected on the light receiving surface 21A is 9 μm or more and the pixel pitch of the light receiving pixels constituting the light receiving surface 21A is 2.2 μm or less, the point The maximum diameter of the effective area of the image is 3 pixels (4.1 pixels) or more.

In addition, the value of the shortest imaging distance Sk is 16f (approximately 61.5 mm) when the maximum diameter Dmax of the effective area of the point image is set to 9 μm.

The value of the depth of focus Sd of the imaging lens 10A is 300 μm when the maximum diameter Dmax of the effective area of the point image is 9 μm.

Regarding the value of the MTF characteristic related to the imaging system of Example 1 above, when the light receiving surface 21A is brought closest to the imaging lens 10A, that is, when the value of the defocus amount Ud is 0 in FIGS. 17( a ) to ( d ), , the value of all MTF characteristics of spatial frequency 20～50Line/mm (also known as root/mm) is positive.

Also, when the light receiving surface 21A is separated from the imaging lens 10A, that is, when the defocus amount is set to 300 μm in FIGS.

That is, when the value of the defocus amount is in the range of 0 to 300 μm, the values of all MTF characteristics at the spatial frequency of 20 to 50 Line/mm are positive.

When the value of the defocus amount is in the range of 300 μm to 400 μm, the value of the MTF characteristic at the spatial frequency of 30 to 50 Line/mm is reversed from 0% and false resolution occurs. The range in which false resolution occurs is indicated by the arrow Gik in the figure.

Here, when the value of the MTF characteristic related to the image of the subject projected on the light-receiving surface is greater than 0%, the image data obtained by capturing the image can be said to have optically meaningful information, so the image data has a practical value. Restoration processing can improve the possibility of resolution data. However, when the value of the MTF characteristic related to the image of the subject projected on the light receiving surface is 0% or is reversed from 0% to cause false resolution, the image data obtained by capturing the image does not have optically meaningful information. Therefore, even if restoration processing is performed on such image data, the quality of the image data (resolution of an image represented by the image data) cannot be improved.

According to the above facts, if this imaging system is adopted, in the predetermined state where the positional relationship between the light receiving surface 21A and the imaging lens 10A is fixed, and the imaging distance is changed to a range of 16f to ∞, it is possible to project the subject onto the light receiving area. The MTF characteristic of the image formed on the surface 21A is always a value greater than 0% (it is possible to prevent false resolution from occurring).

That is, in the range of the imaging distance of 16 to ∞, the image of the subject projected on the light receiving surface 21A can be a meaningful image.

Moreover, when the imaging distance is changed within the range of 0 to ∞, the effective area of the point image projected on the light receiving surface 21A becomes the size of 3 pixels or more related to the light receiving surface 21A, so it can be captured by the subject existing in the range. The image data captured by the volume is restored to improve the resolution of the image.

In other words, the image data obtained by capturing images of various subjects projected onto the light-receiving surface 21A with the imaging system of Embodiment 1, including images of various subjects within the range of imaging distances from 16f to ∞, can be said to satisfy the premise for performing restoration processing. Conditions (conditions for increased resolution).

Furthermore, the restoration process can be performed more easily by suppressing the size variation of the point image projected on the light receiving surface 21A to a small amount. That is, for example, even if the image projected on the light receiving surface includes subjects placed at various photographic distances that are different from each other, if the blur states of the point images constituting the images of the subjects are the same, it is not necessary to indicate any position For the image data of the subject at the same position, the restoration process may be performed without changing the parameters. This can reduce the load on the signal processing unit that performs calculations for restoration processing.

On the other hand, on the premise that the restoration process is always performed using the same parameters, if the blurred state of the point images constituting the image of the subject at various shooting distances projected onto the light receiving surface is the same , by performing the restoration process, the resolution of the image representing the subject can be similarly improved for the image data representing the subject at any position. That is, by performing restoration processing, the resolution of the image can be uniformly increased over the entire image.

In this way, by implementing a design to increase the depth of focus of the imaging lens 10A, images obtained by capturing images of various subjects including imaging distances in the range of 16f to ∞ projected onto the light receiving surface 21A through the imaging lens 10A The resolution of the entire image represented by the image data can be improved by restoration processing.

Furthermore, according to the imaging lens 10A designed as above, the incident angle of the light incident on the light receiving surface 21A with respect to the light receiving surface 21A can be reduced, that is, an imaging lens with good telecentricity can be obtained.

"Aberration of the imaging lens described in Example 1"

FIG. 18 is a diagram showing aberrations related to the imaging lens 10A. In FIG. Aberration) (also referred to as distortion) and chromatic aberration of magnification are shown in order of each aberration diagram of the imaging lens described in Example 1.

The aberration diagrams show aberrations with the e-line (wavelength 546.07nm) as the reference wavelength, but the spherical aberration diagrams and lateral chromatic aberration diagrams also show aberrations for the F-line (wavelength 486.1nm), C-line ( wavelength 656.3nm) aberration. The diagram of distortion aberration uses the focal length f of the entire system and the half angle of view θ (variable processing, 0≤θ≤ω), and assumes that the ideal image height is f×tanθ, indicating the amount of deviation from it.

"Camera System of Comparative Example"

Next, a conventional imaging lens such as a camera for a mobile phone will be described as a comparative example.

19 is a cross-sectional view showing a schematic structure of an imaging lens composed of four single lenses of a comparative example, and FIGS. On the coordinates of the focal amount Ud (μm) and the MTF characteristic value (%) on the vertical axis, the MTF characteristic value (%) of the optical image projected on the light-receiving surface when the light-receiving surface is defocused with respect to the above-mentioned imaging lens is shown change graph. Here, the defocus range of the light receiving surface is 400 μm.

20( a ) to ( d ) showing the MTF characteristics correspond to FIGS. 17 ( a ) to ( d ) showing the MTF characteristics of the imaging lens 10A described above.

As shown in FIG. 19 , in the imaging lens 10H of the comparative example, the first single lens Lh1 and the second single lens Lh2 are arranged in order from the subject side (the arrow - Z direction side in the figure) along the optical axis C (Z axis). , the third single lens Lh3, the fourth single lens Lh4, and the optical component GLh1. The imaging lens 10H having these four single lenses is designed so that the depth of field becomes deeper.

The optical image of the subject is projected onto the light receiving surface 21H through the imaging lens 10H.

Furthermore, the optical component GLh1 is an optical component having no refractive power, which is composed of a parallel plate.

In addition, in Fig. 20 (a) to (d), five rays Jh1, Jh2, Jh3, Jh2, Jh3, Jh4, Jh5.

The five MTF curves Mth20 shown in FIG. 20( a ) represent changes in the value of the MTF characteristic at a spatial frequency of 20 rays/mm at each position where the five light rays are projected onto the light receiving surface 21H. The five MTF curves Mth30 described in FIG. 20( b ) represent changes in the value of the MTF characteristics at the spatial frequency of 30 wires/mm at the same positions as above, and the five MTF curves Mth40 described in FIG. 20( c ) It also shows the change in the value of the MTF characteristic at the spatial frequency of 40 wires/mm at the same positions as above, and the five MTF curves Mth50 described in FIG. The change in the value of the MTF characteristic of the spatial frequency /mm.

The value of the MTF characteristic related to the imaging system of the above-mentioned comparative example is about 0 to 120 μm for the value of the defocus amount in FIG. In the range, the MTF characteristic with respect to the spatial frequency of 30 to 50 Line/mm is in a state where the value is reversed from 0%, and false resolution occurs. The range in which false resolution occurs is indicated by the arrow Gik in the figure.

In addition, when the light receiving surface is separated from the imaging lens, that is, the value of the defocus amount in Fig. 20 (a) to (d) is in the range of 280 μm to 400 μm, and the MTF characteristic with respect to the spatial frequency of 30 to 50 Line/mm becomes the value A state that reverses from 0% and produces false resolution. The range in which false resolution occurs is indicated by the arrow Gik in the figure.

Here, when the value of the defocus amount Ud is between 120 μm and 280 μm (the range of the depth of focus), the value of the MTF characteristic is positive, and the fluctuation range of the value of the MTF characteristic at each spatial frequency is 85% (50 Line/mm), 90 % (40Line/mm), 70% (30Line/mm), 45% (20Line/mm).

As described above, according to the imaging system of the comparative example, the value of the MTF characteristic becomes positive only in a relatively narrow defocus range (approximately 160 μm), and the variation of the value of the MTF characteristic is large.

Regarding the range of defocus in which the value of the MTF characteristic is reversed from 0% (indicated by the arrow Gik in the figure), the point image is a pseudo-resolved image, and the effective area involves more than 3 pixels, which can be specified and has optical significance. picture.

That is, only in a very limited range of photographic distances, the value of the MTF characteristic is positive, and the image of the subject projected onto the light receiving surface can be formed into a meaningful image. In addition, the size of the point image projected on the light receiving surface fluctuates greatly.

In addition, the imaging system of this comparative example is not configured so that when the imaging distance is changed in the range of 0 to ∞, the effective area of the point image projected on the light-receiving surface has a size of 3 pixels or more related to the light-receiving surface. The image data obtained by the imaging system does not satisfy the preconditions (conditions for increasing the resolution) for restoration processing.

Therefore, even if restoration processing is performed on the image data obtained by capturing the image of the subject projected onto the light receiving surface 21H by the imaging system of the comparative example, the effect of improving the resolution of the image representing the subject cannot be obtained.

FIG. 21 is a diagram showing an automobile equipped with an in-vehicle device having an imaging system.

As shown in FIG. 21 , in-vehicle devices 502 to 504 including the imaging system of the present invention can be mounted on an automobile 501 or the like for use. This car 501 has an in-vehicle device 502 which is an exterior camera for photographing a blind spot on the side of the passenger seat, an in-vehicle device 503 which is an exterior camera for photographing a blind spot on the rear side of the car 1, and an interior mirror. The in-vehicle device 504 is an in-vehicle camera that captures the same field of view as the driver's backside.

Fig. 22 is a diagram showing a mobile phone which is a portable terminal device having a camera system.

As shown in the figure, the mobile phone 510 is equipped with a camera system 512 in a casing 511 of the mobile phone.

Fig. 23 is a diagram showing an endoscope device which is a medical device having an imaging system.

As shown in the figure, this endoscope device 520 for observing a biological tissue 525 is provided with an imaging system 522 for imaging a biological tissue 525 illuminated with illumination light La at a front end portion 521 of the endoscope device 520 .

In this way, the imaging device, portable terminal equipment, vehicle-mounted equipment, and medical equipment of the present invention equipped with an imaging system as described above can be compared with existing imaging devices, portable terminal equipment, vehicle-mounted equipment, and medical equipment equipped with known imaging systems in the past. There are camera systems that are easily replaced. That is, the present application can be constituted by replacing the existing imaging system of these devices with the imaging system of the present invention without changing the size or shape of the previously known imaging devices, portable terminal equipment, vehicle-mounted equipment, and medical equipment. Invented camera devices, portable terminal equipment, vehicle-mounted equipment, and medical equipment.

Moreover, in the above-mentioned embodiments, the example in which the imaging lens is limited by various conditions is shown, but the imaging lens used in the imaging system of the present invention may be provided sequentially from the object side and composed of at least one lens with positive optical focal length. degree of the first lens group, the second lens group consisting of at least one lens with negative refractive power, and the third lens group consisting of at least one lens and the lens on the most image side has positive refractive power The imaging lenses of the lens groups are not limited to the number or shape of lenses constituting each group. For example, each group may be composed of a plurality of lenses.

Claims (26)

1. An image pickup system comprising:

a camera lens;

an image pickup element having a light receiving surface in which a plurality of light receiving pixels are two-dimensionally arrayed, for picking up an optical image of an object projected onto the light receiving surface by the image pickup lens and outputting 1 st image data representing the object; and

a signal processing unit configured to perform restoration processing on the 1 st image data to generate 2 nd image data equivalent to the 1 st image data output from the image pickup device when the resolution of the image pickup lens is high;

the imaging lens includes, in order from an object side: a1 st lens group including at least 1 lens and having positive power, a2 nd lens group including at least 1 lens and having negative power, and a3 rd lens group including at least 1 lens and having positive power located closest to the image side;

the imaging lens and the imaging element are configured such that: the maximum diameter of the effective area of a point image projected onto the light receiving surface through the imaging lens from an arbitrary position in the direction X, Y, Z is also set to a size of 3 pixels or more with respect to the light receiving pixel.

2. The imaging system according to claim 1, wherein the imaging lens is configured to: an optical image of an object projected onto the light receiving surface through the imaging lens from an arbitrary position in an X, Y, Z direction that is 10 times or more away from the focal length of the imaging lens is also set such that the value of the MTF characteristic relating to the optical image is positive.

3. The imaging system according to claim 1 or 2, wherein the signal processing means performs the restoration processing with a pixel region for a total of 9 pixels or more, which is composed of 3 pixels or more in a vertical direction and 3 pixels or more in a horizontal direction on the light receiving surface, as a minimum unit.

4. The imaging system according to any one of claims 1 to 3, wherein the signal processing unit executes the restoration processing using a restoration coefficient corresponding to a state of a point image represented by the 1 st image data.

5. An image pickup system comprising:

a camera lens;

an image pickup element having a light receiving surface in which a plurality of light receiving pixels are two-dimensionally arrayed, for picking up an optical image of an object projected onto the light receiving surface by the image pickup lens and outputting 1 st image data representing the object;

a coefficient storage unit that stores a restoration coefficient corresponding to a state of the point image represented by the 1 st image data output from the image pickup device when a maximum diameter of an effective region of the point image projected onto the light receiving surface by the image pickup lens is a size of 3 pixels or more; and

a signal processing unit that performs restoration processing for generating 2 nd image data equivalent to the 1 st image data output from the image pickup device when the resolution of the image pickup lens is high, on the 1 st image data using the restoration coefficient;

the signal processing means performs the restoration processing with a pixel region of 9 pixels or more in total, which is composed of 3 pixels or more in the vertical direction and 3 pixels or more in the horizontal direction on the light receiving surface, as a minimum unit;

the imaging lens includes, in order from an object side: the zoom lens includes a1 st lens group including at least 1 lens and having positive power, a2 nd lens group including at least 1 lens and having negative power, and a3 rd lens group including at least 1 lens and having positive power located closest to the image side.

6. The imaging system according to claim 4 or 5, wherein the coefficient storage unit stores, for each imaging system, a restoration coefficient that is individually obtained for the imaging system.

7. The imaging system according to claim 4 or 5, wherein the coefficient storage unit stores a restoration coefficient selected in accordance with a state of the point image represented by the 1 st image data from among the restoration coefficient candidates corresponding to the respective states of the point images classified into the plurality of types.

8. The imaging system according to claim 4 or 5, wherein the coefficient storage unit stores: and a corrected restoration coefficient in which a restoration coefficient selected in accordance with the state of the point image indicated by the 1 st image data from among a plurality of types of restoration coefficient candidates corresponding to the respective states of the point image classified into a plurality of types is further corrected in accordance with the state of the point image.

9. The imaging system according to any one of claims 4 to 8, further comprising a restoration coefficient acquisition means that acquires the restoration coefficient and stores the restoration coefficient in the coefficient storage means.

10. The imaging system according to any one of claims 1 to 9, wherein the signal processing means performs the restoration processing with a minimum pixel region including all of an effective region of a point image projected onto the light receiving surface as a minimum unit.

11. The imaging system according to any one of claims 1 to 10, wherein the signal processing unit performs the restoration processing so that a size of an effective area of the point image in the image represented by the 2 nd image data is smaller than a size of an effective area of the point image in the image represented by the 1 st image data.

12. The imaging system according to any one of claims 1 to 11, wherein a lens surface located closest to an image side in the 3 rd lens group has an off-axis curvature point.

13. The imaging system according to any one of claims 1 to 12, wherein a lens surface located closest to the image side in the 3 rd lens group is a lens surface that is concave toward the image side at a central portion of the lens surface and convex toward the image side at a peripheral portion.

14. The imaging system according to claim 12 or 13, wherein a lens surface of a lens located closest to the image side in the 3 rd lens group satisfies the following conditional expression (1):

0.5H<h<H……(1)，

wherein,

h is an effective radius of a lens surface located closest to the image side in the 3 rd lens group,

h is a distance from an off-axis curvature point to the optical axis of a lens surface located closest to the image side in the 3 rd lens group.

15. The imaging system according to any one of claims 1 to 14, wherein a lens surface of a lens in the 3 rd lens group which is located on an object side closest to an image side is a lens surface which is convex toward the object side at a central portion of the lens surface and concave toward the object side at a peripheral portion.

16. The image pickup system according to any one of claims 1 to 15, wherein said image pickup lens is constituted by 3 single lenses.

17. The image capturing system of claim 16, wherein the single lens element of the 1 st lens group has a meniscus shape with its convex surface facing the object side, and the single lens element of the 2 nd lens group has a meniscus shape with its convex surface facing the image side.

18. An image pickup apparatus having the image pickup system according to any one of claims 1 to 17.

19. A portable terminal device characterized by having the imaging system according to any one of claims 1 to 17.

20. An in-vehicle apparatus characterized by having the imaging system of any one of claims 1 to 17.

21. A medical apparatus characterized by having the imaging system of any one of claims 1 to 17.

22. An image pickup system comprising:

a camera lens;

an image pickup element having a light receiving surface in which a plurality of light receiving pixels are two-dimensionally arrayed, for picking up an optical image of an object projected onto the light receiving surface by the image pickup lens and outputting 1 st image data representing the object;

a coefficient storage unit that stores a restoration coefficient corresponding to a state of the point image represented by the 1 st image data output from the image pickup device when a maximum diameter of an effective region of the point image projected onto the light receiving surface by the image pickup lens is a size of 3 pixels or more; and

a signal processing unit that performs restoration processing for generating 2 nd image data equivalent to the 1 st image data output from the image pickup device when the resolution of the image pickup lens is high, on the 1 st image data using the restoration coefficient;

the signal processing means performs the restoration processing with a pixel region of 9 pixels or more in total, which is composed of 3 pixels or more in the vertical direction and 3 pixels or more in the horizontal direction on the light receiving surface, as a minimum unit;

the imaging lens includes, in order from an object side: the zoom lens includes a1 st lens group including at least 1 lens and having positive power, a2 nd lens group including at least 1 lens and having negative power, and a3 rd lens group including at least 1 lens and having positive power located closest to the image side.

23. A method of manufacturing an imaging system according to claim 22,

a point image is projected onto a light receiving surface of the image pickup device through the image pickup lens, and a restoration coefficient corresponding to a state of the point image represented by the 1 st image data output from the image pickup device is stored in the coefficient storage unit.

24. The method of manufacturing an imaging system according to claim 23, wherein the restoration coefficient is determined for each imaging system individually.

25. The method of manufacturing an imaging system according to claim 23, wherein the restoration coefficient is selected from among the restoration coefficient candidates corresponding to the respective states of the point images classified into the plurality of types, based on the state of the point image represented by the 1 st image data.

26. The method of manufacturing an imaging system according to claim 23, wherein the restoration coefficient is a restoration coefficient in which a restoration coefficient selected in accordance with a state of the point image indicated by the 1 st image data is further corrected in accordance with a state of the point image, from among a plurality of kinds of restoration coefficient candidates corresponding to respective states of the point image classified into a plurality of kinds.

Images