JP2024085850A - Wide-field image acquisition optical device and wide-field imaging device - Google Patents

Abstract

[Problem] To provide a wide-field image acquisition optical device and a wide-field imaging device that can capture an image with reduced image distortion and no noticeable seams when the images are combined, even though the image has an ultra-wide field of view. [Solution] From the incident side of light carrying subject information, imaging lenses 4, 5, 6 and an optical waveguide 7 are provided in this order, the imaging lenses 4, 5, 6 are configured so that their optical axes are different from each other, the optical waveguide 7 is configured so that light incident end faces 11A, 11B, 11C are each perpendicular to the optical axis of the corresponding imaging lenses 4, 5, 6, and has a light exit end face 12 that exits to the outside the light that is emitted from each imaging lens 4, 5, 6, enters each of the light incident end faces 11A, 11B, 11C, and propagates through the light propagation section 13 of the optical waveguide 7, and an imaging element 2 that acquires subject information is provided behind the light exit end face 12 of the optical waveguide 7. [Selected Figure] Figure 1

Description

The present invention relates to a wide-field image acquisition optical device and a wide-field imaging device for acquiring images with a wide field of view (angle of view), such as panoramic images.

In terms of video media technology, it is hoped that in addition to the high sense of realism that video brings, technology will be realized that will enable the viewing and experiencing of a variety of programs, such as VR (Virtual Reality) and AR (Augmented Reality).
Among these technologies, there is a strong demand for a device that can capture an image with an ultra-wide field of view without image distortion.

2. Description of the Related Art Conventionally, a technique for acquiring an image with an ultra-wide field of view is known that uses one or more cameras equipped with an ultra-wide-angle (fisheye) lens (see, for example, Japanese Patent Application Laid-Open No. 2003-233663).
Furthermore, in a camera system for a drive recorder that contributes to safe driving of a car, there is known one that realizes wide-field shooting by stitching together images obtained from two cameras, one for the front and one for the rear, and two cameras for blind spot compensation, based on information obtained by a separate wide-angle lens (for example, see Patent Document 2 below).

Furthermore, a shooting method using multiple lens groups has been proposed for a camera using a double-image system called TOMBO (see, for example, Patent Document 3 below), and in particular, a camera that achieves ultra-wide-angle shooting with an angle of view equivalent to 180 degrees by performing a synthesis process on each image acquired using multiple optical prisms is known (see, for example, Non-Patent Document 1 below).

JP 2006-315380 A JP 2011-250193 A JP 2001-61109 A

Compound eye camera using CMOS image sensor and its application, Takashi Toyoda, Journal of the Institute of Image Information and Television Engineers, Vol. 63, No. 3, pp. 284-287 (2019)

However, in the technology described in Patent Document 1, due to the characteristics of an ultra-wide-angle (fisheye) lens, problems such as curved image distortion and reduced light intensity, particularly in the periphery of an image, cannot be avoided.
In addition, the technology described in Patent Document 2 cannot avoid problems such as image distortion caused by lenses, as in the technology described in Patent Document 1. Furthermore, when multiple camera images are synthesized into a single image, the seams of the images become conspicuous, and a satisfactory image is not necessarily obtained.

Furthermore, in the technologies described in Patent Document 3 and Non-Patent Document 1, the system is inevitably large because multiple prisms (or diffraction gratings) are used. Furthermore, image quality has not been improved due to the fact that the seams when the images formed by each compound lens are synthesized are noticeable and curved distortion originating from the lenses occurs.
In the technology described in Patent Document 3 and Non-Patent Document 1, when a double-image eye method that does not use an optical prism is used, the parallax between the images obtained by each lens is extremely small, making it difficult to achieve wide-field shooting.

The present invention has been made to solve the above problems, and aims to provide a wide-field image acquisition optical device and wide-field imaging device that can capture images with reduced image distortion and inconspicuous seams when the images are combined, even though the images have an ultra-wide field of view.

In order to achieve the above object, the wide-field image acquisition optical device and wide-field imaging device of the present invention are configured as follows.
That is, the wide-field image acquisition optical device according to the present invention comprises:
an imaging lens and an optical waveguide are provided in this order from an incident side of light carrying subject information;
the imaging lens is configured with at least two imaging lenses having optical axis directions different from each other,
The optical waveguide is characterized in that each of the light incident end faces into which light from the imaging lenses is incident is configured to be perpendicular to the optical axis of the corresponding imaging lens, and the optical waveguide is provided with a light exit end face that exits each of the imaging lenses, enters from each of the light incident end faces, and exits to the outside the light that has propagated inside the optical waveguide.
It should be noted that the above-mentioned "imaging lens" includes not only a single lens but also a lens system made up of a combination of multiple lenses (the same applies below).

Here, the light emitting end surface can be configured in a single planar shape that emits light incident from each portion of the light incident end surface in the same direction.
The optical waveguide may have a structure in which a plurality of optical fibers are bundled together.
It is also preferable that at least one of the imaging lenses is directly or indirectly attached to the optical waveguide so that movement of the imaging lens in the optical axis direction is adjustable.
It is also preferable that the image carrying the subject information be displayed on the light emitting end surface so that it can be visually recognized.
It is also possible to add a means for evaluating the image carrying the subject information, which is displayed on the light emitting end surface.

On the other hand, the wide-field imaging device of the present invention is characterized in that it comprises a wide-field image acquisition optical device described above, and has a flat imaging section that acquires the subject information downstream of the light emission end face of the optical waveguide of the wide-field image acquisition optical device.
In this case, the imaging section may be configured with one or more image sensors that perform photoelectric conversion, or the imaging section may be a camera equipped with an imaging lens.

In the wide-field image acquisition optical device and wide-field imaging device according to the present invention, the angle of view is shared by multiple imaging lenses, and the incident light from each imaging lens is imaged on the light input end face of the optical waveguide, and propagated through the optical waveguide, so that a wide-field photographed image (panoramic image) made by connecting images from multiple imaging lenses can be projected on the light output end face of the optical waveguide. In other words, since it is sufficient to carry out optical design equivalent to a standard lens that is not particularly wide-angle for multiple lenses, it is possible to achieve wide-field photographing that can avoid nonlinear distortion, peripheral image distortion, and insufficient peripheral light, particularly in the peripheral areas of the image, which are problems with super-wide-angle lenses (large angle of view) such as fisheye lenses.
Furthermore, since there is no need to place a structure for expanding parallax, such as a prism, on the light incident side of the imaging lens, the optical design is easy, and a small, lightweight device can be realized.

In addition, according to the wide-field image acquisition optical device of the present invention, the image carrying the subject information displayed on the light-emitting end surface can be set to be visible, allowing the optical image to be directly observed. In addition, by providing a means for evaluating information on the visible image (such as brightness and darkness information) downstream of the light-emitting end surface, the lens and optical system disposed in the optical path can be evaluated.

Furthermore, according to the wide-field imaging device of the present invention, an imaging section that captures subject information is provided downstream of the light-emitting end face of the optical waveguide of the wide-field image acquisition optical device, so that subject information can be obtained as a panoramic image.

1 is a conceptual diagram showing the structure of a wide-field imaging device and the structure of a wide-field image acquisition optical device according to a first embodiment of the present invention. 5A to 5C are conceptual diagrams showing the structure of a wide-field imaging device and the structure of a wide-field image acquisition optical device according to a second embodiment of the present invention. 11A to 11C are conceptual diagrams showing the structure of a wide-field imaging device and the structure of a wide-field image acquisition optical device according to a third embodiment of the present invention. FIG. 4 is a schematic diagram showing an example of a mechanism for changing the back focus of a lens according to each embodiment of the present invention. 1A and 1B are conceptual diagrams showing the structures of imaging devices according to conventional techniques ((a) a conventional general imaging device, and (b) a conventional imaging device using an optical imaging waveguide (FOP)).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a wide-field image acquisition optical device and a wide-field imaging device according to embodiments of the present invention will be described with reference to the drawings.
The wide-field image acquisition optical device and wide-field imaging device according to this embodiment are devices capable of capturing an image with a wider field of view (angle of view) than any other imaging method used in television cameras.

(overview)
First, an overview of a wide-field image acquiring optical device according to the present embodiment will be described with reference to FIG. 1 showing the first embodiment as a representative diagram.
This wide-field image acquisition optical device 1000 includes a plurality of imaging lenses (three lenses in FIG. 1 ) 4, 5, 6 arranged on the light incident side and with different optical axis directions from each other. It also includes an optical waveguide (in this embodiment, a FOP (Fiber Optics Plate) is used as the optical waveguide 7, and therefore hereinafter also referred to simply as FOP 7) having light incident end faces 11A, 11B, 11C arranged substantially perpendicular to the optical axes of the imaging lenses 4, 5, 6, into which light emitted from the plurality of imaging lenses 4, 5, 6 is incident, a light propagation section 13 that propagates the light incident from the light incident end faces 11A, 11B, 11C, and a light exit end face 12 that emits the light propagated by the light propagation section 13 to the outside.
On the other hand, the wide-field imaging device 2000 of this embodiment is equipped with a wide-field image acquisition optical device 1000, and an imaging section (image sensor 2 in Figure 1) is provided downstream of the light exit end face 12 of the optical waveguide 7 of this wide-field image acquisition optical device 1000 (so as to be approximately abutting the light exit end face 12 in Figure 1).

The main features of this embodiment are listed below.
(1) The multiple imaging lenses 4, 5, and 6 are each composed of at least two imaging lenses whose optical axes are different from each other.
(2) The light focused on each of the light incident end faces 11A, 11B, and 11C of the optical waveguide 7 by the imaging lenses 4, 5, and 6, which are directed in each direction (having different optical axis directions), is aligned so that the light is emitted in the same direction at the light exit end face 12 of the optical waveguide 7.

(3) As described above, by arranging the imaging unit 2 (including a single imaging element or a group of multiple imaging elements) on the same plane (the side of the light exit end surface 12 of the optical waveguide 7) to configure the wide-field imaging device 2000, it is possible to output an image signal based on the subject information.
(4) On the other hand, even if the wide-field image acquisition optical device 1000 is configured without the imaging unit 2, the light-emitting end face 12 of the optical waveguide 7 can be made visible, and the performance of the imaging lenses 4, 5, 6 and the optical waveguide 7 can be evaluated using various optical measuring instruments, etc., based on the optical image information displayed on the light-emitting end face 12 of the optical waveguide 7.
Moreover, a panoramic image can be obtained by re-capturing the optical image information displayed on the light emitting end surface 12 of the optical waveguide 7 using an imaging device (including various cameras).

(5) As described above, the wide-field imaging device 2000 is equipped with an imaging unit 2. The imaging unit 2 may be a single imaging element or a group of multiple imaging elements, and may be driven as a set of elements or may be divided and driven for each pixel or each pixel region.
(6) The wide-field image acquisition optical device 1000 and the wide-field imaging device 2000 according to the present embodiment employ a wide-field imaging technique that realizes a compound-eye imaging method, and can determine the wide-field imaging angle of view based on the focal length (angle of view) of each imaging lens 4, 5, 6, the number of imaging lenses 4, 5, 6, and the light incidence angle to the optical waveguide 7 (for example, when three lenses 4, 5, 6 are used as shown in FIG. 1, it is possible to set the incidence angle with respect to the optical axis of the optical waveguide 7 to 0 degrees for lens 4, -60 degrees for lens 5, and +60 degrees for lens 6, as described below). In other words, it is essential to determine the specifications of the imaging lenses 4, 5, 6 and the optical waveguide 7 from the imaging angle of view required for the desired acquired image.
This makes it unnecessary to provide a structure for expanding parallax, such as a prism, on the light incident side of the imaging lenses 4, 5, and 6, making the optical design easier and enabling a compact and lightweight device to be realized.

Specifically, for example, if the angle of view (horizontal direction of the imaging range) of each of the imaging lenses 4, 5, and 6 is 60 degrees or more, the imaging lenses 4, 5, and 6 may be designed to have three numbers, and three directions of light incidence into the optical waveguide 7. That is, as shown in Fig. 1, when the optical axis direction of the first lens 4 from the center (central axis) of the optical waveguide 7 is set to 0 degrees, the optical axis of the second lens 5 may be rotated counterclockwise by 60 degrees (-60 degrees) and the optical axis of the third lens 6 may be rotated clockwise by 60 degrees (+60 degrees) around the fulcrum P of the optical axis (180 degrees÷3=60 degrees).
Regarding the number of imaging elements, in addition to a method of capturing an optical image guided from multiple lenses through an optical waveguide using a single imaging element on a plane, a method of divided photography using multiple imaging elements can also be adopted.

(Embodiment 1)
Hereinafter, the wide-field image acquisition optical device 1000 and the wide-field imaging device 2000 according to the first embodiment of the present invention will be described in more detail with reference to the drawings.
<Basic configuration of wide-field imaging device>
1 ((a) is a vertical cross-sectional view, and (b) is a perspective view seen from diagonally above) shows the basic configuration of a wide-field imaging device 2000 of this embodiment. Here, an example is shown in which three imaging lenses 4, 5, and 6 having optical axes with different angles are used.
The wide-field imaging device 2000 of this embodiment includes an imaging lens 4 whose optical axis is set parallel to the optical axis of an imaging section 2 (hereinafter also simply referred to as the imaging element 2) consisting of an imaging element, and imaging lenses 5 and 6 whose optical axes are set at an angle to each other. The wide-field imaging device 2000 further includes an optical waveguide 7 having light incident end faces 11A, 11B, and 11C that are approximately perpendicular to the optical axes of these three imaging lenses 4, 5, and 6, a light propagation section 13 consisting of a plurality of optical fibers, and a planar light exit end face 12 that exits light that is incident from the light incident end faces 11A, 11B, and 11C and propagated by the light propagation section 13. The wide-field imaging device 2000 further includes a flat imaging element 2 (having a planar light receiving surface) arranged in close proximity to and facing this light exit end face 12.
On the other hand, the basic configuration of the wide-field image acquisition optical device 1000 of this embodiment can be expressed by removing the configuration of the image sensor 2 from the basic configuration of the wide-field imaging device 2000 of this embodiment.
In FIG. 1, a11, a12, and a13 indicate the diameters of the imaging lenses 4, 5, and 6, b11, b12, and b13 indicate the back focal lengths of the imaging lenses 4, 5, and 6, and c11, c12, and c13 indicate the imaging ranges (diameters) of the imaging lenses 4, 5, and 6.

Incidentally, a general conventional imaging device has a schematic configuration as shown in FIG.
5A shows the simplest conventional imaging device. Light collected by an imaging lens 501 is focused on the light receiving surface of an imaging element 502, which performs photoelectric conversion to obtain electrical image data.
Also, FIG. 5(b) shows a conventional imaging device (e.g., Patent No. 6518038, etc.) in which an FOP 603 is inserted between an imaging lens 601 and an imaging element 602, in which an optical image is formed on the light incident end surface of the FOP 603 by the imaging lens 601, the light is propagated inside the FOP 603, and the optical image is projected on the light exit end surface.
In contrast, the wide-field imaging device 2000 of this embodiment uses three imaging lenses 4, 5, and 6, as shown in Figure 1, and the field of view and turning angles are set as follows, which is significantly different from the above-mentioned conventional technologies.

1 and 2, when the light incident direction (0 direction) from above that is perpendicular to the light receiving surface of the image sensor 2 is taken as 0 degrees, the turning angles of the three imaging lenses 4, 5, 6 are 0 degrees for the imaging lens 4, 60 degrees (-60 degrees) to the left (counterclockwise) for the imaging lens 5, and 60 degrees (+60 degrees) to the right (clockwise) for the imaging lens 6, with the fulcrum P of the optical axis (the point where the optical axes of all the imaging lenses 4, 5, 6 intersect) as the center.
First, the three imaging lenses 4, 5, and 6 are made to have the same specifications, the diagonal of the imaging range is set to an angle of view of 60 degrees or more (60 degrees x 3 = 180 degrees) as described above, and the turning direction of each imaging lens 4, 5, and 6 is set to the turning angle described above, so that an optical image with a wide field of view of 180 degrees can be emitted (projected) at the light emitting end face 12 of the optical waveguide 7.

Here, the optical waveguide, which is a main component of the wide-field image acquisition optical device 1000 and the wide-field imaging device 2000 according to this embodiment, will be described in more detail.
An optical waveguide is an optical component that has the function of transmitting incident light to a light emitting end face and emitting the light therefrom. Its components are optical fibers made of core glass, cladding glass, and coupling glass for preventing crosstalk. There are types in which single-layer optical waveguides 7 in which these optical fibers are arranged in parallel are stacked in multiple stages, and types in which multiple optical fiber components are bundled together.
In the wide-field image acquiring optical device 1000 and the wide-field imaging device 2000 according to the present embodiment, an FOP formed in the shape of a plate by arranging optical fibers in a fibrous form is used as the optical waveguide 7. However, it is of course possible to use other types of optical waveguides for the wide-field image acquiring optical device and the wide-field imaging device of the present invention.

In the optical waveguide 7, by using the FOP, when optical images from the imaging lenses 4, 5, and 6 are formed on the light incident end faces 11A, 11B, and 11C, respectively, as shown in FIG. 1, the optical images can be optically propagated to the light exit end face 12.
Furthermore, by closely contacting the light receiving surface of the imaging element 2, which is a solid-state imaging element such as a CMOS, the optical waveguide 7 can effectively transmit the optical image formed on the light incident end faces 11A, 11B, and 11C to the imaging element 2.
That is, the optical image obtained by the imaging lenses 4, 5, and 6 is projected onto the light-emitting end face 12 of the optical waveguide 7. In addition to capturing the optical image by placing the imaging element 2 close to the light-emitting end face 12 (optically coupling) as in the wide-field imaging device 2000 of this embodiment, in the wide-field image acquisition optical device 1000 of this embodiment, it is possible to directly view the optical image projected onto the light-emitting end face 12 or to capture this optical image with a separate camera.

By using the above-mentioned elemental technologies and configuring the optical waveguide 7 with a shape according to the turning angle and imaging area of each imaging lens 4, 5, 6 based on the number of imaging lenses 4, 5, 6, the focal length (angle of view) of the imaging lenses 4, 5, 6, and the position of the fulcrum P of the optical axis, it is possible to obtain a wide-field optical image with reduced distortion and inconspicuous seams in the image.

Next, the imaging element 2 and other components of the wide-field imaging device 2000 according to this embodiment will be described in more detail.
As the imaging element 2, for example, a solid-state imaging element such as a CCD, in addition to the above-mentioned CMOS, can be used. In addition, in the wide-field imaging device of the present invention, an imaging device such as a normal imaging tube or an FOP-HARP imaging tube using an FOP as a substrate can be used instead of the imaging element.
Furthermore, when high-sensitivity photography is required, it is possible to use an image intensifier or a microchannel plate (MCP). Also, a photosensitive material such as film can be used.

Furthermore, if the planar light receiving surface of the image sensor 2 is disposed within 40 μm of the light emitting end surface 12 of the optical waveguide 7, it is possible to realize good wide-field imaging with an angle of view of 180 degrees. Note that, as described above, the minute gap between the image sensor 2 and the optical waveguide 7 that occurs due to the close proximity can be filled with a dedicated grease or the like to achieve good optical coupling between the opposing light receiving surfaces of the image sensor 2 and the light emitting end surface 12 of the optical waveguide 7, making it possible to obtain a highly accurate image without distortion.
The imaging element 2 may be a single imaging element, or a combination of a plurality of imaging elements.
The imaging element 2 may be driven as a single element, or may be divided and driven for each pixel or each pixel region.

<Light Propagation Action of Optical Waveguide>
The FOP used in the optical waveguide 7 shown in FIG. 1 generally has a structure in which a large number of optical fibers are bundled together, as described above, and is made up of three types of glass structures: a core glass that is a light-transmitting portion, a cladding glass that is a light-shielding portion, and a coupling glass for preventing fiber crosstalk.
Generally, the core glass portion that propagates light is a linear straight fiber, and the emission ranges (horizontal lengths) c11', c12', c13' emitted from the light emitting end face 12 of the optical waveguide 7 after light propagation differ depending on the light incident angle to this optical fiber. That is, even if the imaging ranges (diameters) c11, c12, c13 on the corresponding light incident end faces 11A, B, C of the imaging lens 4, imaging lens 5, imaging lens 6 are approximately the same range, if the light incident angle to this optical fiber differs, the horizontal emission ranges c11', c12', c13' emitted from the light emitting end face 12 will differ.

However, in the wide-field imaging device 2000 of embodiment 1 shown in Figure 1, light incident along the optical axis of the imaging lens 4 is set to be incident on the optical fiber arranged perpendicular to the optical waveguide 7 at 0 degrees, while light incident along the optical axis of the imaging lens 5 is set to be incident on the optical fiber at -60 degrees (a counterclockwise angle from the above 0 degrees is defined as -), and light incident along the optical axis of the imaging lens 6 is set to be incident on the optical fiber at +60 degrees (a clockwise angle from the above 0 degrees is defined as +). Therefore, when the imaging ranges (diameters) c12, c13 on the light incident end faces 11B, C are the same range, the emission ranges (horizontal direction) c12', c13' emitted from the light emitting end face 12 will be the same range.
That is, in this case, the following formula (1) holds.
c11'≠c12'=c13' (1)

As described above, the image area of the light emitting end face 12 of the optical waveguide 7 is reduced in the horizontal direction in FIG. 1A at the c12' and c13' portions compared to the c11' portion.
As a method for returning such a shape to the original shape, a method can be adopted in which the expansion/contraction ratio of the image is calculated in advance based on the cross-sectional shape of the core glass, etc., and the output image is corrected according to the expansion/contraction ratio.
It is also possible to add correction lenses in front of and behind the imaging lenses 5 and 6 to expand or contract the image in the horizontal direction (the lateral direction in FIG. 1A) and to restore the original shape.

(Embodiment 2)
A wide-field image acquisition optical device 1100 and a wide-field imaging device 2100 according to a second embodiment of the present invention will be described below with reference to Fig. 2 ((a) is a vertical cross-sectional view, and (b) is a perspective view seen from diagonally above). Note that since the second embodiment has a similar configuration to the first embodiment, the corresponding components are indicated by adding 100 to the reference numerals of the first embodiment, and detailed description thereof will be omitted.
2, a21, a22, and a23 indicate the diameters of the imaging lenses 104, 105, and 106, b21, b22, and b23 indicate the back focal lengths of the imaging lenses 104, 105, and 106, and c21, c22, and c23 indicate the imaging ranges (diameters) of the imaging lenses 104, 105, and 106.
In the optical coupling method between the optical waveguide 107 and the image sensor 102 according to the second embodiment, for example as shown in Fig. 2A, an optical waveguide 107' for optical imaging is inserted between the optical waveguide 107 and the image sensor 102. Note that since CCD cameras with FOPs, in which an FOP is attached in advance to the light receiving surface of a solid-state image sensor, are generally available on the market, it is possible to easily construct the wide-field imaging device 2100 according to this embodiment by using such cameras.
The optical waveguide 107' for optical coupling may use the same FOP as the optical waveguide 107, or may use a different FOP.
Furthermore, when the same FOP is used for both the optical waveguide 107 and the optical waveguide 107' for optical coupling, the optical coupling between them can be improved by using a special grease in the gap between them, as in the method described above, to improve the adhesion between them.

(Embodiment 3)
Hereinafter, a wide-field image acquisition optical device 1200 and a wide-field imaging device 2200 according to a third embodiment of the present invention will be described with reference to Fig. 3 ((a) is a longitudinal sectional view, (b) is a partially enlarged schematic view of (a), and (c) is a perspective view seen from diagonally above). Note that, among the components of the third embodiment, those corresponding to those of the first embodiment are indicated by adding 200 to the reference numerals of the components of the first embodiment, and detailed description thereof will be omitted.
The wide-field image acquisition optical device 1200 and the wide-field imaging device 2200 according to the third embodiment show a case in which the number of imaging lenses 201 is increased compared to the first and second embodiments. When the number of imaging lenses 201 is increased in this manner, the shape of the optical waveguide approaches a cylindrical shape (semi-cylindrical shape), and the imaging range covered by one imaging lens 201 becomes smaller.

FIG. 3A shows a configuration in which the number of imaging lenses 201 arranged in the circumferential direction on the outer circumferential surface of the optical waveguide 207 is 15, and the angle of view of the imaging range (diagonal) of each imaging lens 201 is 12 degrees or more.
FIG. 3( c ) is a perspective view of the optical waveguide 207 shown in FIG. 3( a ) when viewed obliquely from above, and shows how the imaging lenses 201 are arranged in an orderly manner on the outer circumferential surface of the cylindrical optical waveguide 207, and how incident light from direction 0 perpendicular to the axis of the cylindrical optical waveguide 207 is irradiated onto this circumferential surface.
When the number of lenses is increased, it is possible to integrate the lenses and the structure supporting them into an array structure.

Incidentally, in a configuration including a larger number of imaging lenses 201, for example in the configuration shown in the above-mentioned embodiment 3, the light incident from the imaging lens 201 whose optical axis is inclined by ±70 degrees or more with respect to the incidence direction 0 direction will have a large angle with respect to the extension direction of the core glass 220 of the cylindrical optical waveguide 207 (see the partially enlarged schematic diagram in FIG. 3(b)).
In such a case, it is sufficient to use an optical waveguide (FOP) 207 with a refractive index Na (determined based on the refractive index _n0 of the core glass 220 and the refractive index _n1 of the cladding glass 221) of 1, which makes it possible to receive light from each imaging lens 201 over a range of ±90 degrees with respect to the above-mentioned 0 direction. Therefore, even light from an imaging lens 201 whose optical axis is greatly inclined with respect to the incident direction 0 direction can be propagated well in the direction of the light output end face 32 via each optical fiber of the optical waveguide 207.

A specific formula (2) for calculating the refractive index Na is shown below, where n is the refractive index of the medium (usually air) on the incident side of the optical fiber, and θ is the light incident angle with respect to the light incident end surface 31 of the optical waveguide 207 (of each optical fiber).
NA=n・Sinθ=(n ₀ ² - n ₁ ² ) ^1/2 (2)

(Modifications)
The wide-field image acquisition optical device and the wide-field imaging device of the present invention are not limited to the above-mentioned embodiment, and various other modifications are possible. For example, the characteristics of the imaging lenses, such as focal length, size, performance, etc., may be the same for all the imaging lenses, or the characteristics of some or all of the imaging lenses may be different from each other as necessary.
In addition, in the wide-field imaging device of the above embodiment, the light incident end surface of the optical waveguide has a planar shape, but instead, it is also possible for this light incident end surface to have a curved shape (including a spherical shape, a cylindrical shape, etc.).

Furthermore, when the lens specifications are changed, it is necessary to change the back focus of the imaging lens (b11, b12, and b13 shown in FIG. 1 in the first embodiment, and b21, b22, and b23 shown in FIG. 2 in the second embodiment). Therefore, when there is a possibility of changing the lens specifications, it is preferable to have a configuration in which the imaging lens is indirectly or directly locked to the optical waveguide and can be moved perpendicularly to the light incident end face of the optical waveguide as necessary.
For example, as shown in FIG. 4, the imaging lens 304 is a structure connected to a partition 308 for preventing crosstalk, and therefore this partition 308 may be utilized to configure so that the back focus b41, which corresponds to the distance between the light exit surface of the imaging lens 304 and the light incident end surface of the optical waveguide 307, can be adjusted using screws, spacers, springs, or the like.

That is, a lens holder 351 that holds the imaging lens 304 is screwed into a lens barrel 352 that is connected to a partition wall 308 installed in an optical waveguide 307, and the distance of the back focus b41 can be easily changed as needed by rotating the lens holder 351 in either the left or right direction relative to the lens barrel 352. In addition, in Fig. 4, a41 indicates the diameter of the imaging lens 304, and c41 indicates the imaging range (diameter) of the imaging lens 304.
The lens barrel 352 may be configured to be directly connected to the optical waveguide 307 instead of to the partition wall 308 .

In addition, in the above embodiment, an imaging element placed close to the light output end face of the optical waveguide is used as the imaging section of the wide-field imaging device of the present invention, but instead of this imaging element, a camera equipped with an imaging lens may be used, and this camera may be for capturing still images or for capturing moving images, and any conventional camera system may be applicable.
Moreover, a plurality of cameras may be provided.
Furthermore, the image to be acquired may be not only visible light, but also infrared light, ultraviolet light, or other radiation, and the type can be selected according to the application of the image to be acquired.
When an imaging element is used, it is possible to obtain a wide-field panoramic image of 180 degrees or more by forming light receiving surfaces on the front and back of the imaging element on a flat plate.

In addition, the wide-field image acquisition optical device of the above embodiment uses an image sensor that has the function of emitting an ultra-wide field image onto the light receiving surface of a single plane, but instead, it is also possible to optically transmit an image signal related to the light from the light emitting end face of the optical waveguide using an optical fiber or the like.

2, 102, 202, 502, 602 Image sensor (imaging section)
4, 5, 6, 104, 105, 106, 201, 304, 501, 601 Imaging lens 7, 107, 107', 207, 307, 603 Optical waveguide (FOP)
8, 108, 208, 308 Partition wall 11A, 11B, 11C, 21A, 21B, 21C, 31 Light incident end surface 12, 22, 32 Light emitting end surface 13, 23, 33 Light propagation section 220 Core glass 221 Cladding glass 351 Lens holder 352 Lens barrel 1000, 1100, 1200 Wide-field image acquisition optical device 2000, 2100, 2200 Wide-field imaging device a11, a12, a13, a21, a22, a23, a41 Diameter of imaging lens b11, b12, b13, b21, b22, b23, b41 Back focus of imaging lens c11, c12, c13, c21, c22, c23, c41 Imaging ranges of the imaging lens c11', c12', c13', c21', c22', c23': Light emission range from the light emission end face (horizontal length)
P: Fulcrum of optical axis

Claims (9)

an imaging lens and an optical waveguide are provided in this order from an incident side of light carrying subject information;
the imaging lens is configured with at least two imaging lenses having optical axis directions different from each other,
a light guide configured so that each of the light incident end faces into which light from the imaging lenses is incident is perpendicular to the optical axis of the corresponding imaging lens, and the optical waveguide is provided with a light exit end face that outputs to the outside the light that is emitted from each of the imaging lenses, incident from each of the light incident end faces, and propagated inside the optical waveguide. The wide-field image acquisition optical device according to claim 1, characterized in that the light exit end surface forms a single planar shape that outputs light incident from each portion of the light entrance end surface in the same direction. The wide-field image acquisition optical device according to claim 1, characterized in that the optical waveguide has a structure in which multiple optical fibers are bundled together. The wide-field image acquisition optical device according to claim 1, characterized in that at least one of the imaging lenses is attached directly or indirectly to the optical waveguide so that the movement of the imaging lens in the optical axis direction is adjustable. The wide-field image acquisition optical device according to claim 1, characterized in that the image carrying the subject information displayed on the light-emitting end surface is configured to be visible. The wide-field image acquisition optical device according to claim 1, further comprising a means for evaluating the image carrying the subject information displayed on the light exit end surface. A wide-field imaging device comprising the wide-field image acquisition optical device according to any one of claims 1 to 6, characterized in that the wide-field image acquisition optical device is provided with a flat imaging section that acquires the subject information, downstream of the light-emitting end face of the optical waveguide. The wide-field imaging device according to claim 7, characterized in that the imaging section is composed of one or more imaging elements that perform photoelectric conversion. 8. The wide-field imaging device according to claim 7, wherein the imaging unit is a camera equipped with an imaging lens.

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