JP2002296499A - Reading lens, reading lens block, image reader and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reading lens whose cost is made very low though it has a function and performance exceeding the conventional reading lens using a lens surface having non-rotationally symmetric (anamorphic) shape. SOLUTION: This reading lens has a front group 1 consisting of two or more lenses including at least one positive lens and a rear group 2 consisting of one negative lens in order from an object side, and a back focus in an actual using state is <=25% of the entire length of the lens, and a distance between the front group 1 and the rear group 2 is equal to or above the half of the entire length of the lens, and at least one surface of a rear group lens L4 has the non-rotationally symmetric shape. A curve formed by making the surface having the non-rotationally symmetric shape of the lens L4 cross with a plane including an optical axis forms non-circular-arc shape. The reading lens block having a photodetector element for sampling and photoelectrically converting an image formed by the reading lens is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading lens, a reading lens block, an image reading apparatus, and an image forming apparatus, and is applicable to a digital copying machine, an image scanner, a facsimile, and the like.

[0002]

2. Description of the Related Art As a relatively large-diameter, high-resolution reading lens used in a document reading unit such as a digital copying machine or an MFP, a Gauss type is widely known. As a known example of the Gaussian type, a recent one is disclosed in
And those described in JP-A-111794.

In the present invention, as will be described later, a lens having a negative power is arranged in the vicinity of the image plane.
There is one described in Japanese Patent Publication No. However, the reading lens described in this publication has a two-lens configuration, the performance is low, and the performance is insufficient for use in a document reading unit such as a digital copying machine or an MFP.

A reading lens having a non-rotationally symmetric (anamorphic) lens surface is also used. Such a reading lens is described in Japanese Patent Application Laid-Open No. 2000-307800. However, in the reading lens described in this publication, the lens is not disposed near the image plane, and the effect of the non-rotationally symmetric lens surface cannot be sufficiently exhibited.

[0005]

SUMMARY OF THE INVENTION Digital copier, MF
A reading lens used for a document reading unit such as a P or a high-end flatbed scanner is required to have a relatively large diameter and a high resolution. Conventionally, the Gauss type is widely used for such a purpose, but the cost is not sufficiently low because the number of components is as large as 6 or more and all are made of glass lenses.

[0006] Further, the reading density of the above-described original reading section and scanner is 300 dpi, 400 dpi to 600 dpi.
pi, and further to 1200 dpi, and in some cases, Gauss type, which is composed entirely of spherical surfaces, cannot provide sufficient performance.

[0007] In order to improve the performance, it is conceivable to introduce an aspherical surface. However, when the above-mentioned document reading unit or scanner is constituted by using a one-dimensional light receiving element array (line sensor), an additional non-spherical surface is required. It is also possible to introduce a lens surface having a rotationally symmetric (anamorphic) shape, and such an example is described in JP-A-2000-307800. However, it cannot be said that the reading lens described in this publication sufficiently exerts the effect of the lens surface having a non-rotationally symmetric shape.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and the invention according to claim 1 uses a conventional lens surface having a non-rotationally symmetric (anamorphic) shape. It is an object of the present invention to provide a sufficiently low-cost reading lens while having functions and performances exceeding those of a conventional reading lens.

A second object of the present invention is to improve the performance of the reading lens according to the first embodiment without increasing the cost. A third aspect of the present invention aims to further reduce the size and thickness of the reading lens according to the first aspect. A fourth object of the present invention is to enable various adjustments of the reading lens according to the first embodiment to be performed by a simple method.

A fifth aspect of the present invention is directed to the reading lens according to the fourth aspect, in which the inclination of the image plane due to the eccentricity can be adjusted by a simple method. According to a sixth aspect of the present invention, in the reading lens according to the fourth aspect, it is an object to enable the focus to be adjusted by a simple method.

According to a seventh aspect of the present invention, there is provided a reading lens having a function and performance exceeding those of a conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and a light receiving lens having a sufficiently low cost. Combining element arrays,
It aims to provide a high-performance and low-cost lens block.

An eighth aspect of the present invention is to reduce the cost of the lens block according to the seventh aspect. The invention according to claim 9 and claim 10 is:
It is another object of the present invention to further reduce the cost of the lens block according to the seventh aspect.

According to the eleventh aspect of the present invention, a light receiving lens is provided to a reading lens having a function and a performance that are superior to those of a conventional reading lens using a lens surface having a non-rotationally symmetric (anamorphic) shape, and at a sufficiently low cost. It is an object of the present invention to provide a high-performance, low-cost image reading apparatus combining an element array, a document illuminating unit, a scanning unit, a signal processing unit, and an image processing unit. According to a twelfth aspect of the present invention, in the image reading apparatus according to the eleventh aspect, an object is to simplify optical adjustment.

According to a thirteenth aspect of the present invention, there is provided a reading lens having a function and performance exceeding those of a conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and a light receiving lens having a sufficiently low cost. It is an object of the present invention to provide a high-performance, low-cost image forming apparatus combining an element array, an original illuminating unit, a scanning unit, a signal processing unit, an image processing unit, and an image output unit.

According to a fourteenth aspect of the present invention, there is provided a reading lens which has a function and performance that are superior to those of a conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and has a sufficiently low cost. It is intended to be provided by means of.

[0016]

A reading lens, a reading lens block, an image reading apparatus and an image forming apparatus according to the present invention have the following features. 2. The reading lens according to claim 1, comprising, in order from the object side, a front group consisting of two or more lenses including at least one positive lens, and a rear group consisting of one negative lens. The back focus at 25% or less of the total lens length, the air gap between the front group and the rear group is at least half of the total lens length, and at least one surface of the rear group lens has a non-rotationally symmetric shape. It is characterized by.

The reading lens according to the second aspect is the first aspect.
Wherein the curved surface formed by the non-rotationally symmetric surface of the rear group lens intersecting with the plane including the optical axis has a non-circular shape. According to a third aspect of the present invention, in the reading lens according to the first aspect, the rear lens group has a non-rotationally symmetric outer shape with respect to the optical axis. According to a fourth aspect of the present invention, there is provided the reading lens according to the first aspect, wherein the holding member of the front group and the holding member of the rear group are formed separately.

The reading lens according to the fifth aspect is the same as the fourth aspect.
In the reading lens described in 1, the holding member of the front group lens has a rotationally symmetric shape with respect to the optical axis, and only the front group is rotated around the optical axis, whereby the inclination of the image plane due to eccentricity or the like can be adjusted. It is characterized by the following. According to a sixth aspect of the present invention, in the reading lens according to the fourth aspect, focus adjustment is performed by moving only the front group in the optical axis direction.

According to a seventh aspect of the present invention, there is provided a reading lens block comprising:
From the object side, in order from the object side, there is a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens, and the back focus in actual use is 25% or less of the entire lens length. Wherein the air gap between the front group and the rear group is equal to or more than half of the entire length of the lens, and at least one surface of the rear group lens has a non-rotationally symmetric shape, and is formed by the reading lens. It has a light receiving element array for sampling an image and performing photoelectric conversion.

The reading lens block according to claim 8 is
The reading lens block according to claim 7, wherein the rear group lens of the reading lens and the light receiving element array are integrated. In the reading lens block according to the ninth aspect, in the reading lens block according to the eighth aspect, the rear group lens of the reading lens directly shields a package of the light receiving element array, and the package of the light receiving element has a shield glass. It is characterized by not having. Claim 10
A reading lens block according to claim 8, wherein the light receiving element array is directly attached to the rear lens image side surface of the reading lens in the reading lens block according to claim 8, and the light receiving element array does not have a package. It is characterized by.

The image reading apparatus according to the eleventh aspect includes, in order from the object side, a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens. The back focus in actual use is not more than 25% of the entire length of the lens, the air gap between the front group and the rear group is not less than half of the entire length of the lens, and at least one surface of the rear group lens is non-rotationally symmetric. A reading lens having a shape, a light receiving element array for sampling and photoelectrically converting an image formed by the reading lens, a means for illuminating a document, a means for scanning the document, a signal processing means, and an image processing Means.
According to a twelfth aspect of the present invention, in the image reading apparatus of the eleventh aspect, the reading magnification is adjusted not optically but electrically.

An image forming apparatus according to a thirteenth aspect has, in order from the object side, a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens. The back focus in actual use is not more than 25% of the entire length of the lens, the air gap between the front group and the rear group is not less than half of the entire length of the lens, and at least one surface of the rear group lens is non-rotationally symmetric. A reading lens having a shape, a light receiving element array for sampling and photoelectrically converting an image formed by the reading lens, a means for illuminating a document, a means for scanning the document, a signal processing means, and an image processing Means and an image output means.

According to a fourteenth aspect of the present invention, there is provided a reading lens comprising at least three lenses, wherein a lens closest to the image side has negative power and is arranged near an image plane.
At least one surface of the lens closest to the image has a non-rotationally symmetric shape.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a reading lens, a reading lens block, an image reading apparatus, and an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram of a reading lens according to an embodiment of the present invention. The reading lens according to this embodiment has, in order from the object side, a front group 1 composed of two or more lenses including at least one positive lens, and a rear group 2 composed of one negative lens L4. . More specifically, it includes, in order from the object side, a front group 1 including three lenses, a positive lens L1, a negative lens L2, and a positive lens L3, and a rear group 2 including negative lenses L4 to L4. Reference numeral 3 indicates an image plane. The front group 1 mainly shares the imaging function, and the rear group 2 plays a role as a so-called field flattener.

Here, in order to ensure sufficient imaging performance, it is necessary that the front unit 1 includes two or more lenses. When the front unit 1 has a single-sheet configuration, even if an aspherical surface or the like is introduced, its aberration correction capability is low, and a digital copier or M
Insufficient performance is obtained for use in a document reading unit such as an FP. In order for the rear group 2 to sufficiently fulfill the role of a field flattener, the back focus in the actual use state needs to be 25% or less of the entire length of the lens. In order to efficiently correct the field curvature of the front unit 1 in the rear unit 2, the height of the off-axis principal ray in the rear unit 2 needs to be as high as possible, and it is desirable that the back focus is short. Further, in order to reduce the size of the front group 1, the air gap between the front group 1 and the rear group 2 needs to be at least half of the total lens length. If the air gap between the front group 1 and the rear group 2 is smaller than half of the total length of the lens, the size of the front group 1 becomes large and causes an increase in cost.

According to the reading lens having the above configuration,
The function and performance equivalent to or higher than the Gaussian type can be realized with a smaller number of lenses than the Gaussian type, and a sufficient cost reduction can be achieved. In addition, at least one surface of the rear group 2 is not rotated. By adopting a symmetric (anamorphic) shape, higher performance can be obtained. The effect of the lens surface having a non-rotationally symmetric shape is that the curvature of field and coma in the main scanning direction (meridional) and the sub-scanning direction (sagittal) can be corrected to some extent independently, but the lens surface passes through the lens surface. The more the luminous flux for each image height is separated at a point in time, the higher the degree of freedom of correction.

In the reading lens according to the present invention, the rear lens group is disposed near the image plane. At the time when the rear lens group passes through the rear lens group, the light flux at each image height is sufficiently separated, so that at least one surface of the lens is separated. With the non-rotationally symmetric shape, the curvature of field in the main scanning direction and the sub-scanning direction can be corrected with a very high degree of freedom. The present invention maximizes the effect of a lens surface having a non-rotationally symmetric shape, which has not been sufficiently exhibited in a reading lens, and provides a conventional reading lens using a non-rotationally symmetric lens surface. The performance can be greatly improved.

It should be noted that the cost can be further reduced by forming the rear group lens of plastic.
In the reading lens according to the present invention, by disposing the rear lens group near the image plane, the paraxial ray height in the rear lens group becomes small. Even if the power fluctuation increases, the influence on aberration and back focus is small. Therefore, the rear lens group can be relatively easily made of plastic.

In order to make the reading lens according to the present invention larger in diameter and higher in performance, it is necessary to form a curve in which the non-rotationally symmetric (anamorphic) surface of the rear lens intersects with the plane including the optical axis. , It is desirable to form it in a non-arc shape. As described above, since the rear group lens is close to the image plane and the light flux for each image height passes sufficiently separated, the cross section of the rear group lens in the main scanning direction and the sub scanning direction is made non-circular. Off-axis aberrations can be effectively corrected. In particular, when the rear lens unit is a plastic molded product, there is almost no increase in cost due to the non-circular cross section.

In the reading lens according to the present invention, the rear lens group can have a non-rotationally symmetric shape with respect to the optical axis, if necessary. When the reading lens according to the present invention is used in combination with a one-dimensional light receiving element array (line sensor), the effective light range required for the rear lens group is long in the main scanning direction and short in the sub-scanning direction. Therefore, the rear group lens L4 can have an outer shape obtained by cutting out a part of a circle as shown in FIG. 2 or can have a rectangular outer shape as shown in FIG. Thus, the rear lens group L
Although it is possible for the rear lens group L4 to be a non-rotationally symmetric shape even if the rear lens group L4 is made of glass, it can be more easily realized by forming the rear lens group L4 as a molded plastic product. If the rear lens group L4 is a plastic molded product,
It is easy to integrally form the projections 4 and 5 for positioning, holding and fixing on the upper surface or the side end surface of the rear lens group L4 as shown in FIG. A recess may be provided instead of the projections 4 and 5.

In the reading lens according to the present invention, since the air gap between the front group and the rear group is large, it may be better to form the holding member for the front group lens and the holding member for the rear group lens separately. For example, if the front lens group has a rotationally symmetric shape and the rear lens group has a non-rotationally symmetrical shape, as shown in FIG. The holding member of the group lens 2 may be a substrate 6, and the lens frame of the front group lens 1 may be attached to the substrate 6 which is a holding member of the rear group lens 2. That is, the rear group lens 2 composed of one lens has the projections 5 on both side ends shown in FIG. 4, and the rear group lens 2 is placed on the substrate 6 via the plate-like intermediate member 8. The rear group lens 2 is attached to the substrate 6 by pressing the projections 5 with a leaf spring 10 against a pair of quadrangular prisms 9 integrally formed at the rear end. On the other hand, the front lens group 1 has a plurality of constituent lenses held by a generally used cylindrical lens frame, and the lens frame is mounted on the protrusion 5 by a band-shaped mounting member 7.

As shown in FIG. 5, when the holding member of the front lens group 1 and the holding member of the rear lens group 2 are formed separately, the holding member of the front lens group 1 has a rotationally symmetric shape with respect to the optical axis. By using a certain lens frame, only the front unit 1 can be rotated around the optical axis, whereby the inclination of the image plane caused by the eccentricity of the lenses can be adjusted.
In particular, when the reading lens according to the present invention is used in combination with a one-dimensional light receiving element array (line sensor),
The effect is great. The structure is also simple.

When the holding member of the front lens group 1 and the holding member of the rear lens group 2 are formed separately as in the embodiment shown in FIG. 5, only the front lens group 1 is moved in the optical axis direction. Can be used to adjust the focus. By not moving the rear group lens 2, the mounting structure can be simplified especially when the rear group lens 2 has a non-rotationally symmetric shape.

In a reading lens according to the present invention, the off-axis illuminance decreases in proportion to the cosine fourth power of the angle of view, and it is necessary to correct this in some way. Generally, a light beam regulating plate having a shape such that a light beam having a smaller angle of view is more largely blocked, that is, a so-called shading correction plate, is often provided on the object side of the reading lens. In the reading lens of the present invention,
This shading correction plate can be provided inside the lens. FIG. 6 shows a specific example. The example shown in FIG.
A shading correction plate 11 is arranged between the front group 1 and the rear group 2 on the substrate 6 in the example shown in FIG.
Since the shading correction plate 11 is disposed between the front group 1 and the rear group 2, it is not necessary to secure a space for providing the shading correction plate on the object side of the reading lens.

In the reading lens of the present invention, if necessary,
A mirror for bending the optical path can be provided between the front group and the rear group. FIG. 7A shows an example in which the optical path is not bent, and FIG. 7B shows an example in which the mirror 12 is disposed between the front group 1 and the rear group 2 and the optical path is bent. By bending the optical path in this way, the degree of freedom in layout within the device increases. As shown in FIG. 8, by forming the reflection surface 12a of the mirror 12 in the same shape as the shape of the light transmission window of the shading correction plate, it is possible to additionally have a function as a shading correction plate.

The reading lens according to the present invention is used in combination with a light receiving element array 15 for sampling an image formed by the reading lens and performing photoelectric conversion, as shown in FIG. Specific examples of the light receiving element array include a CCD and a CMOS sensor. The state in which the reading lens and the light receiving element array are combined can be considered as one module, and this module is called a reading lens block.

In the reading lens block according to the present invention, the rear group lens of the reading lens and the light receiving element array can be integrated. As shown in FIG. 10, the light receiving element array is generally housed in a package 17 disposed on a substrate 16, and the package 17 is sealed with a shield glass 18. If the image side surface of the rear group lens is flat, the rear group lens 2 and the shield glass 18 are joined by an adhesive layer 19 as shown in FIG. Is possible. By integrating the rear lens group 2 and the light receiving element array 15, the structure of the reading lens block can be simplified.

As shown in FIG. 12, the package 17 of the light receiving element array can be directly sealed with the rear lens group 2. With such a structure, the shield glass 18 in the example shown in FIG. 11 becomes unnecessary, and the cost can be reduced. Further, as shown in FIG. 13, the package 17 of the light receiving element array 15 can be omitted, and the light receiving element array 15 can be directly adhered to the image side surface of the rear lens group 2. As shown in FIG. 14, the image side surface of the rear group lens 2 to which the light receiving element array 15 is attached may be a curved surface. By making the image side surface of the rear group lens 2 a curved surface along the curvature of field of the reading lens, the configuration of the front group lens can be simplified and further improved performance can be realized.

In the reading lens block according to the present invention, when the rear group lens of the reading lens and the light receiving element array are not integrated, the light receiving element array 15 is moved in the optical axis direction as shown in FIG. Can be used to adjust the focus. If the focus adjustment is performed by moving the light receiving element array 15, the advantage that the performance fluctuation of the reading lens due to the focus adjustment can be reduced as compared with the case where the focus adjustment is performed by moving only the front group 1 in the optical axis direction. There is.

When the focus adjustment is performed by moving the light receiving element array in the optical axis direction, the front lens and the rear lens can be held by the same member. This embodiment is shown in FIGS. 16 and 17, the front group holding unit 22 and the rear group holding unit 23 are mounted on one base 21.
Are provided so that the front group 1 and the rear group 2 can be held by these holding portions. The front group holding section 22 is formed by forming a groove for holding substantially the lower half of a plurality of lenses constituting the front group. The holding structure of the rear group is substantially the same as the holding structure of the rear group shown in FIGS.
After the front lens 1 is inserted into the holding portion 22, it is fixed by bonding or the like. As described above, if the front group lens 1 and the rear group lens 2 are held by one base 21, the parts of the front group lens 1 and the rear group lens 2 can be greatly reduced as compared with the case where the rear group lens 2 has a separate lens frame. The number can be reduced, and the cost can be reduced.

In the examples shown in FIGS. 16 and 17, the base 21 is attached to the horizontal portion of the L-shaped light receiving element array holding member 24.
The rear end of the light receiving element array 15 is fixed to the vertical part of the light receiving element array holding member 24 via a substrate.
Has a fixed structure. The base 21 and the light receiving element array holding member 24 may be relatively movable in the optical axis direction to perform focus adjustment.

FIG. 18 is a schematic diagram showing an example in which the reading lens and the reading lens block according to the present invention are applied to a document reading section such as a digital copying machine or an MFP or an image reading apparatus such as a flatbed scanner. The original 26 placed on the contact glass 25 is illuminated by illumination means including a light source 34 and a reflection plate 35 attached to the first traveling body 31, and a light beam from the original 26 is transmitted to the first traveling body 31. The first mirror 36 attached, and the second and third mirrors 37, 38 attached to the second traveling body 32.
Is led to the reading lens 33 by the front lens 1
The image of the document 26 is formed on the light receiving element array 15 such as a CCD by the reading lens 33 including the rear lens group 2 and the rear lens 2. The first traveling body 31 scans the document 26 at the speed V, and the second traveling body 32 moves at the speed V / 2, thereby
The distance from 6 to the reading lens 33 is kept constant. The signal output from the light receiving element array 15 is processed by an appropriate signal processing unit 39 and an image processing unit 40.

The reading magnification can be adjusted electrically using the signal processing means 39 or the image processing means 40. Since the reading magnification is adjusted optically instead of optically, it is not necessary to consider the reading magnification at the time of focus adjustment, and the adjustment mechanism and the adjustment process can be simplified.

FIG. 19 is a schematic view showing an example in which the reading lens and the reading lens block according to the present invention are applied to an image forming apparatus such as a digital copying machine or an MFP. FIG.
The image information read by the image reading device shown in FIG. 19 is processed by the signal processing unit 39 and the image processing unit 40 in the example shown in FIG. As image output means,
Electrophotographic printers, inkjet printers, etc., which mainly output to sheet-like materials such as paper and film;
Displaying on an RT display, a liquid crystal projector or the like is conceivable.

The reading lens according to the present invention is composed of at least three lenses. The lens closest to the image side has negative power and is arranged near the image plane. This can also be realized by having one surface having a non-rotationally symmetric shape.

Hereinafter, specific numerical examples of the reading lens according to the present invention will be described. The aberration of the embodiment is sufficiently corrected, and a document reading unit such as a digital copying machine and an MFP,
It can be used for high-end flatbed scanners. Note that Numerical Embodiment 2, Numerical Embodiment 6, Numerical Embodiment 7, and Numerical Embodiment 8 are assumed to be used in combination with a light receiving element array having a shield glass. The other numerical examples assume that the shield glass is eliminated and the package of the light receiving element array is directly sealed with the rear lens group.

The meanings of the symbols in the examples are as follows. f: focal length of the entire system (paraxial focus in the main scanning direction) m: magnification Fm: effective F number at magnification m Y: maximum object height R: radius of curvature (paraxial curvature in the main scanning direction on a non-rotationally symmetric surface) Radius; = Ry) D: Surface spacing Nd: Refractive index νd: Abbe number Ky: Conical constant of anamorphic aspheric surface in main scanning direction Kz: Conical constant of anamorphic aspheric surface in sub-scanning direction Rz: Sub-scanning direction of anamorphic aspheric surface Ar4: fourth-order rotationally symmetric component coefficient of an anamorphic aspheric surface Ar4: sixth-order rotationally symmetric component coefficient of an anamorphic aspheric surface Ar8: eighth-order rotationally symmetric component coefficient of an anamorphic aspheric surface Ar10: anamorphic aspherical surface 10th order rotationally symmetric component coefficient Ap4: 4th order non-rotationally symmetric component coefficient of anamorphic aspheric surface Ap6: 6th order anamorphic aspherical surface Rotationally symmetric component coefficients AP8: 8-order non-rotationally symmetric element coefficient of the anamorphic aspherical AP 10: non-rotationally symmetric component coefficient 10 following the anamorphic aspherical

However, the anamorphic aspherical surface used here has a reciprocal of the paraxial radius of curvature in the main scanning direction (paraxial curvature) of Cy, a reciprocal of the paraxial radius of curvature in the sub-scanning direction (paraxial curvature) of Cz, and Cz. The distance from the optical axis in the main scanning direction is Y,
When the distance from the optical axis in the sub-scanning direction is Z, it is defined by the following equation.

Numerical Example 1: FIG. 20 shows the optical arrangement, and FIG. 28 shows various aberrations.

Numerical Example 2: FIG. 21 shows the optical arrangement, and FIG. 29 shows various aberrations.

Numerical Example 3: FIG. 22 shows the optical arrangement, and FIG. 30 shows various aberrations.

Numerical Example 4 : FIG. 23 shows the optical arrangement, and FIG. 31 shows various aberrations.

Numerical Example 5 : FIG. 24 shows the optical arrangement, and FIG. 32 shows various aberrations.

Numerical Embodiment 6 : FIG. 25 shows the optical arrangement, and FIG. 33 shows various aberrations.

Numerical Example 7 : FIG. 26 shows the optical arrangement, and FIG. 34 shows various aberrations.

Numerical Embodiment 8 : FIG. 27 shows the optical arrangement, and FIG. 35 shows various aberrations.

[0057]

According to the first aspect of the present invention, reading is performed at a sufficiently low cost while having functions and performances exceeding those of a conventional reading lens using a lens surface having a non-rotationally symmetric (anamorphic) shape. A lens can be provided.

According to the invention described in claim 2, according to claim 1
Without increasing the cost,
Higher performance can be achieved. According to the third aspect of the invention, the reading lens of the first aspect can be further reduced in size and thickness. According to the fourth aspect, various adjustments of the reading lens according to the first aspect can be performed by a simple method.

According to the invention set forth in claim 5, according to claim 4,
In the reading lens described in (1), the inclination of the image plane due to eccentricity can be adjusted by a simple method. According to the sixth aspect of the invention, in the reading lens according to the fourth aspect,
Focus can be adjusted in a simple way.

According to the seventh aspect of the present invention, a reading lens having a function and performance exceeding those of a conventional reading lens using a lens surface having a non-rotationally symmetric (anamorphic) shape, and having a sufficiently low cost can be obtained. A high-performance and low-cost lens block combining a light receiving element array can be obtained. According to the eighth aspect, the lens block according to the seventh aspect can be reduced in cost. According to the invention described in claims 9 and 10,
The lens block according to claim 7 can be further reduced in cost.

According to the eleventh aspect of the present invention, a reading lens having a function and performance exceeding those of a conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and having a sufficiently low cost can be obtained. It is possible to provide a high-performance and low-cost image reading apparatus combining a light receiving element array, a document illuminating means, a scanning means, a signal processing means and an image processing means. According to the twelfth aspect,
In the image reading device according to the eleventh aspect, the optical adjustment can be simplified.

According to the thirteenth aspect of the present invention, a reading lens having a function and performance superior to those of a conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and having a sufficiently low cost can be obtained. It is possible to provide a high-performance and low-cost image forming apparatus in which a light receiving element array, a document illuminating unit, a scanning unit, a signal processing unit, an image processing unit, and an image output unit are combined.

According to the fourteenth aspect of the present invention, there is provided a reading lens which has functions and performances exceeding those of the conventional reading lens using a lens surface having a non-rotationally symmetrical (anamorphic) shape, and has a sufficiently low cost. , Can be provided by other means.

[Brief description of the drawings]

FIG. 1 is an optical layout diagram showing an embodiment of a reading lens according to the present invention.

FIG. 2 is a perspective view and a front view showing an example of a rear lens group applicable to the present invention.

FIG. 3 is a perspective view and a front view showing another example of a rear group lens applicable to the present invention.

FIG. 4 is a perspective view and a front view showing still another example of a rear group lens applicable to the present invention.

FIG. 5 is a perspective view showing an embodiment of a reading lens block according to the present invention.

FIG. 6 is a perspective view showing another embodiment of the reading lens block according to the present invention.

FIG. 7 is an optical layout diagram showing an example of an optical path of a reading lens block according to the present invention.

FIG. 8 is a front view showing an example of a reflection mirror applicable to the present invention.

FIG. 9 is an optical layout diagram showing still another embodiment of the reading lens block according to the present invention.

FIG. 10 is a partial cross-sectional plan view showing an example of a light receiving element array applicable to the reading lens block according to the present invention.

FIG. 11 is a partial sectional plan view showing another example of the light receiving element array applicable to the reading lens block according to the present invention.

FIG. 12 is a partial cross-sectional plan view showing still another example of the light receiving element array applicable to the reading lens block according to the present invention.

FIG. 13 is a partial sectional plan view and a side view showing still another example of the light receiving element array applicable to the reading lens block according to the present invention.

FIG. 14 is a partial sectional plan view and a side view showing still another example of the light receiving element array applicable to the reading lens block according to the present invention.

FIG. 15 is an optical layout diagram showing still another embodiment of the reading lens block according to the present invention.

FIG. 16 is a side view showing still another embodiment of the reading lens block according to the present invention.

FIG. 17 is a perspective view of the reading lens block according to the third embodiment;

FIG. 18 is an optical layout diagram and a block diagram showing an embodiment of a reading device according to the present invention.

FIG. 19 is an optical layout diagram and a block diagram illustrating an embodiment of an image forming apparatus according to the present invention.

FIG. 20 is an optical layout diagram showing a first embodiment of the reading lens according to the present invention.

FIG. 21 is an optical arrangement diagram showing a second embodiment of the reading lens according to the present invention.

FIG. 22 is an optical layout diagram showing a third embodiment of the reading lens according to the present invention.

FIG. 23 is an optical arrangement diagram showing a fourth embodiment of the reading lens according to the present invention.

FIG. 24 is an optical layout diagram showing a fifth embodiment of the reading lens according to the present invention.

FIG. 25 is an optical arrangement diagram showing a sixth embodiment of the reading lens according to the present invention;

FIG. 26 is an optical arrangement diagram showing a seventh embodiment of the reading lens according to the present invention.

FIG. 27 is an optical arrangement diagram showing an eighth embodiment of the reading lens according to the present invention.

FIG. 28 is an aberration diagram showing various characteristics of the first example of the reading lens according to the present invention.

FIG. 29 is an aberration diagram showing various characteristics of the second example of the reading lens according to the present invention.

FIG. 30 is an aberration diagram showing various characteristics of the third example of the reading lens according to the present invention.

FIG. 31 is an aberration diagram showing various characteristics of the fourth example of the reading lens according to the present invention.

FIG. 32 is an aberration diagram showing various characteristics of the fifth example of the reading lens according to the present invention.

FIG. 33 is an aberration diagram showing various characteristics of the sixth example of the reading lens according to the present invention.

FIG. 34 is an aberration diagram showing various characteristics of the seventh example of the reading lens according to the present invention.

FIG. 35 is an aberration diagram showing various characteristics of the eighth example of the reading lens according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 front group lens 2 rear group lens 3 image plane 15 light receiving element array 17 package 18 shield glass 39 signal processing means 40 image processing means 41 image output means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/19 H04N 1/04 102 F term (Reference) 2H044 AC01 2H087 KA08 KA18 LA04 PA03 PA04 PA05 PA17 PB03 PB04 PB05 QA02 QA05 QA12 QA17 QA21 QA22 QA25 QA26 QA37 QA38 QA41 QA45 QA46 RA05 RA07 RA12 RA13 2H108 AA01 CB01 DA01 DA06 HA01 HA03 5B047 AA01 BA02 BB02 BC05 BC09 BC11 BC14 5C072 AA04 DA02 X02 DA02 DA02

Claims (14)

[Claims] 1. A lens system comprising: a front group consisting of two or more lenses including at least one positive lens and a rear group consisting of one negative lens in order from the object side; The reading is characterized by being not more than 25% of the total length, the air gap between the front group and the rear group being more than half of the total lens length, and at least one surface of the rear group lens has a non-rotationally symmetric shape. lens. 2. The reading lens according to claim 1, wherein
A reading lens, wherein a curve formed by a non-rotationally symmetric surface of a rear lens group intersecting with a plane including an optical axis forms a non-arc shape. 3. The reading lens according to claim 1, wherein
A reading lens, wherein the rear group lens has a non-rotationally symmetric outer shape with respect to the optical axis. 4. The reading lens according to claim 1, wherein
A reading lens, wherein the holding member of the front group and the holding member of the rear group are formed separately. 5. The reading lens according to claim 4, wherein
A reading lens, characterized in that the holding member of the front group lens is rotationally symmetrical with respect to the optical axis, and that only the front group is rotated around the optical axis to adjust the inclination of the image plane due to eccentricity or the like. . 6. The reading lens according to claim 4, wherein
A reading lens wherein focus adjustment is performed by moving only the front group in the optical axis direction. 7. A lens system according to claim 1, further comprising, in order from the object side, a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens. A reading lens having an air gap between the front group and the rear group of not more than 25% of the total length, and having at least one surface of the rear group lens having a non-rotationally symmetric shape; A light-receiving element array for sampling and photoelectrically converting an image formed by the lens. 8. The reading lens block according to claim 7, wherein a rear group lens of the reading lens and a light receiving element array are integrated. 9. The reading lens block according to claim 8, wherein a rear group lens of the reading lens directly shields a package of the light receiving element. 10. The reading lens block according to claim 8, wherein a light receiving element array is directly attached to a side surface of a rear lens image of the reading lens. 11. A lens system according to claim 1, further comprising, in order from the object side, a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens. Less than 25% of the total length, and
The air gap between the front group and the rear group is equal to or more than half of the total lens length, and at least one surface of the rear group lens has a non-rotationally symmetric shape. A light receiving element array for conversion, a means for illuminating the document, a means for scanning the document, a signal processing means for processing a signal obtained from the light receiving element array by scanning the document, and an image processing means; An image reading apparatus comprising: 12. The image reading apparatus according to claim 11, wherein the reading magnification is adjusted electrically. 13. A lens system according to claim 1, further comprising, in order from the object side, a front group including at least one positive lens and including two or more lenses, and a rear group including one negative lens. Less than 25% of the total length, and
The air gap between the front group and the rear group is equal to or more than half of the total lens length, and at least one surface of the rear group lens has a non-rotationally symmetric shape. A light receiving element array for conversion, a means for illuminating the document, a means for scanning the document, a signal processing means for processing a signal obtained from the light receiving element array by scanning the document, and an image processing means; And an image output means for outputting an image based on an image processing signal. 14. An image forming apparatus comprising at least three lenses, wherein a lens closest to the image side has a negative power and is arranged near the image plane, and at least one surface of the lens closest to the image side is non-rotationally symmetric. A reading lens having a special shape.