Wide-field video acquisition optical device and wide-field imaging device

Abstract

To provide a compact wide-field video acquisition optical device and a wide-field imaging device that make it possible to photograph an image which is a super-wide field image, but still has less image distortion and an inconspicuous joint when composed.SOLUTION: In a compact wide-field video acquisition optical device, Optical member combinations 51, 52 and 53, in which imaging lenses 8, 9 and 10 and optical waveguides 5, 6 and 7 are arranged in this order from an incidence side (0 direction) for light carrying subject information, are provided on common optical axes P11, P12 and P13 extending in a plurality of directions, respectively. The compact wide-field video acquisition optical device may be configured to be a reduced optical system in which core parts of light emission end faces (113A, 113B and 113C) of optical waveguides (105, 106 and 107 are made smaller in diameter than core parts of light incidence end faces (112A, 112B and 112C).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wide-field image acquisition optical device and a wide-field imaging device for acquiring an image with a wide field of view (angle of view), such as a panoramic image. [Background technology]

[0002] In terms of video media technology, in addition to the high sense of realism that video brings, there are high hopes for the realization of technology that will enable the viewing and experience of a variety of programs, such as VR (Virtual Reality) and AR (Augmented Reality). Among these technologies, there is a strong demand in the broadcasting and medical fields for a device that can capture images with an ultra-wide field of view without image distortion.

[0003] 2. Description of the Related Art Conventionally, a technique for acquiring an image with a super-wide field of view is known that uses one or more cameras equipped with a super-wide-angle (fisheye) lens (see, for example, Patent Document 1 below). 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).

[0004] Furthermore, in a camera using a double-image system called TOMBO, a shooting technique using multiple lens groups has been proposed (see, for example, Patent Document 3 below). 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). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-315380 A [Patent Document 2] JP 2011-250193 A [Patent Document 3] JP 2001-61109 A [Non-patent literature]

[0006] [Non-Patent Document 1] "Compound-eye camera using CMOS image sensor and its applications" Takashi Toyoda, Journal of the Institute of Image Information and Television Engineers, Vol. 63, No. 3, pp. 284-287 (2019) Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technology described in Patent Document 1, due to the characteristics of the super-wide-angle (fisheye) lens, problems such as curved image distortion and reduced light intensity, particularly in the periphery of the 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.

[0008] Furthermore, in the technology described in Patent Document 3 and Non-Patent Document 1, the system is inevitably large because multiple prisms (or multiple mirrors) 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 occurs due to the lenses. 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.

[0009] The present invention has been made to solve the above problems, and aims to provide a compact wide-field image acquisition optical device and wide-field imaging device that can capture ultra-wide-field images with reduced image distortion and inconspicuous seams when combined. [Means for solving the problem]

[0010] 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 has The optical element pair, in which an imaging lens and an optical waveguide are arranged in this order from the incident side of light carrying subject information, is disposed on a common optical axis extending in a plurality of directions. 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).

[0011] Here, the optical waveguide can be configured so that each light incident end face into which light from the imaging lens is incident is arranged perpendicular to the optical axis of the corresponding imaging lens, and so that the optical image formed on each light incident end face is propagated internally to the light exit end face that emits light to the outside. The optical waveguide may have a structure in which a plurality of optical fibers are bundled together. The optical waveguide may be a reduction optical system in which the diameter of a core portion at the light exit end face is smaller than the diameter of a core portion at the light entrance end face. Here, the optical waveguide can be configured so that multiple stages are superimposed in series. In such a case, the "light emitting end face" refers to the light emitting end face of the optical waveguide located closest to the light emitting side, and the "light incident end face" refers to the light incident end face of the optical waveguide located closest to the light incident side.

[0012] At least one of the imaging lenses constituting the optical member pair is preferably attached directly or indirectly to the optical waveguide so that movement of the imaging lens in the optical axis direction is adjustable.

[0013] It is also preferable that the image carrying the subject information be displayed on the light exit end face of the optical waveguide so as to be visually recognizable. It is also possible to add a means for evaluating an image carrying the subject information, which is displayed on the light exit end surface of the optical waveguide.

[0014] On the other hand, it is preferable that a wide-field imaging device according to the present invention includes any of the wide-field image acquisition optical devices described above, and further includes a flat imaging section facing the light emission end face of the optical waveguide for acquiring the subject information. In this case, the imaging section may be configured with one or more imaging elements that perform photoelectric conversion, or the imaging section may be a camera equipped with an imaging lens. Effect of the Invention

[0015] In the wide-field image acquiring optical device and wide-field imaging device according to the present invention, optical member pairs each consisting of an imaging lens and an optical waveguide are provided in a plurality of different directions, and each optical member pair is assigned a different angle of view. That is, by forming an image of the light emitted from each imaging lens on the light input end face of the corresponding optical waveguide and propagating through these optical waveguides, a wide-field captured image made by joining images from the multiple imaging lenses can be projected on the light output end faces of these multiple optical waveguides.

[0016] This makes it possible to perform optical design equivalent to a standard lens that is not particularly wide-angle for multiple lenses, making it possible to capture a wide field of view that avoids issues that have been a problem with ultra-wide-angle lenses (large angle of view) such as fisheye lenses, such as nonlinear distortion, peripheral image distortion, and insufficient peripheral light, especially at the periphery of the image. 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. Furthermore, because of the above-mentioned configuration, the back focal distance can be easily adjusted, and the lens can be easily replaced with one having different specifications. In addition, since the imaging lens and the optical waveguide corresponding to this imaging lens have a common optical axis, and the angle between the optical axis of the imaging lens and each plane of the optical waveguide does not change, there is no need to adjust the arrangement of the lenses for the output image. Also, since a lens assembly using multiple lenses does not use a wide-angle lens as each lens, image distortion can be suppressed even if image processing is not performed when acquiring or outputting an image.

[0017] Furthermore, according to the wide-field image acquisition optical device of the present invention, the image carrying the subject information displayed on each light-emitting end face of the multiple optical waveguides is set to be visible, so that the optical image can be directly observed. Furthermore, by providing a means for evaluating information on the visible image (such as brightness information) at the rear stage of the light-emitting end face, the lens and optical system arranged in the optical path can be evaluated. [Brief description of the drawings]

[0018] [Figure 1] 1A and 1B 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 first embodiment of the present invention ((a) is a vertical cross-sectional view, and (b) is a perspective view). [Diagram 2] 1A and 1B are conceptual diagrams ((a) is a longitudinal sectional view, and (b) is a perspective view) 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. [Diagram 3] 11A and 11B are conceptual diagrams ((a) is a longitudinal sectional view, and (b) is a perspective view) 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. [Figure 4] 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. [Diagram 5]1A and 1B are conceptual diagrams showing 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

[0019] 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 the present 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.

[0020] (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 acquiring optical device comprises a plurality of imaging lenses (three lenses in FIG. 1) 8, 9, 10 arranged on optical axes P11, P12, P13 that are oriented in different directions, and optical waveguides (in this embodiment, FOPs (Fiber Optics Plates) are used as the optical waveguides 5, 6, 7) corresponding to the respective imaging lenses 8, 9, 10. That is, this wide-field image acquiring optical device comprises an optical element pair 51 in which the imaging lens 8 and the optical waveguide 5 are arranged on the common optical axis P11, an optical element pair 52 in which the imaging lens 9 and the optical waveguide 6 are arranged on the common optical axis P12, and an optical element pair 53 in which the imaging lens 10 and the optical waveguide 7 are arranged on the common optical axis P13. Furthermore, each optical waveguide 5, 6, 7 is provided with light incident end faces 12A, 12B, 12C arranged approximately perpendicular to the optical axis of each imaging lens 8, 9, 10, into which light emitted from each imaging lens 8, 9, 10 is incident, light propagation sections 14A, 14B, 14C that propagate the light incident from these light incident end faces 12A, 12B, 12C, and light exit end faces 13A, 13B, 13C arranged approximately parallel to the light incident end faces 12A, 12B, 12C and that emit the light propagated by these light propagation sections 14A, 14B, 14C to the outside.

[0021] On the other hand, the wide-field imaging device of this embodiment includes the above-mentioned wide-field image acquisition optical device, and each includes an imaging section (image pickup elements 2, 3, 4 in Figure 1) downstream of the light output end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7 of this wide-field image acquisition optical device (so as to be approximately abutting the light output end faces 13A, 13B, 13C in Figure 1).

[0022] The main features of this embodiment are listed below. (1) Optical element pairs 51, 52, 53 in which imaging lenses 8, 9, 10 and optical waveguides 5, 6, 7 are arranged on common optical axes P11, P12, P13 are composed of at least two optical element pairs whose optical axis directions are different from each other (in the embodiment of FIG. 1, each optical element pair is composed of three optical element pairs 51, 52, 53). (2) The light focused on each of the light incident end faces 12A, 12B, 12C of the optical waveguide 7 by the imaging lenses 8, 9, 10 directed in each direction (having different optical axis directions), is adjusted so that the light emitted from the light exit end faces 13A, 13B, 13C of the optical waveguide 7 is directed toward the same fulcrum P.

[0023] (3) The light carrying the subject information is imaged on the light incident end faces 12A, 12B, 12C of the optical waveguides 5, 6, 7 by the imaging lenses 8, 9, 10 whose optical axes (common optical axes) P11, P12, P13 are oriented in each direction, and propagates inside the optical waveguides 5, 6, 7, more specifically inside the light propagation sections 14A, 14B, 14C, and the optical images are displayed on the light exit end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7. Here, the optical axis refers to the straight line connecting the center and focal point of a lens, spherical mirror, ellipsoidal mirror, etc. in an optical system. That is, it coincides with the rotational symmetry axis of the coaxial optical system (this embodiment acquires a wide-field image using two or more optical element pairs 51, 52, 53, and for example, the optical axes P11, P12, P13 of the three optical element pairs 51, 52, 53 are arranged such that the lines extending from the fulcrum P of each optical axis P11, P12, P13 in the direction in which each imaging lens 8, 9, 10 is pointed are the optical axes P11, P12, P13, as shown in FIG. 1, and the center lines of the imaging lenses 8, 9, 10 and the center lines of the optical waveguides 5, 6, 7 become the optical axes).

[0024] (4) In addition, by visually observing the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7, or by combining an imaging device with a video output waveform monitor to capture an image of, for example, a chart for evaluating resolution, it is possible to evaluate the resolution from the signal waveform of the amplitude modulation of the obtained luminance signal. Furthermore, by capturing an image of an evaluation chart for image distortion formed in a lattice or circle, it is also possible to evaluate the distortion rate for each region of the image from the acquired image, and the device can be used as a measuring device. Furthermore, if the characteristics of the imaging lens are known in advance, optical measurements (set to combine an imaging device and a video output waveform monitor in the same manner as in the above-mentioned embodiment) and evaluations of the optical waveguides 5, 6, and 7 can be performed based on those characteristics.

[0025] (5) As shown in FIG. 2, the FOP used in the optical waveguides 105, 106, 107 may be a reduction optical system in which the diameter of the core portion on the light emitting end face 113A, 113B, 113C side is smaller than the diameter of the core portion on the light incident end face 112A, 112B, 112C side. In this case, the diameter of the core portion on the light emitting end face 113A, 113B, 113C side can be set smaller, so that the imaging lenses 108, 109, 110, the optical waveguides 105, 106, 107, and the imaging unit (image sensors 2, 3, 4 in FIG. 1) can be positioned closer to the fulcrum P of the optical axis. In the first embodiment, the distance from the fulcrum P to the light incident end faces 12A, 12B, and 12C of the optical waveguides 5, 6, and 7 is taken as the radius, and the circle with the fulcrum P at its center is taken as F11 (see FIG. 1). A circle F21 of the same size is shown in FIG. 2 (similarly, a circle F31 of the same size is shown in FIG. 3). In contrast, in the second embodiment, the reduction optical system is used to reduce the distance from the fulcrum P to the light incident end faces 112A, 112B, and 112C of the optical waveguides 105, 106, and 107, so that the circle F22 with the fulcrum P at its center and with the radius of this distance can be made significantly smaller than the circle F21, as shown in FIG. 2. This makes it possible to reduce parallax in the acquired wide-field-of-view image, and prevents failure of the image synthesis process caused by a nearby subject obscuring a distant subject.

[0026] (6) The wide-field imaging device of this embodiment (including any of embodiments 1, 2, and 3; the same applies below) includes a plurality of imaging sections as described above. When imaging elements are used as the imaging sections, a single imaging element may be provided in correspondence with the optical member pairs 51, 52, and 53 including the imaging lenses 8, 9, and 10 and the optical waveguides 5, 6, and 7, or an imaging element group consisting of a plurality of imaging elements may be provided, or further, a set of flexible imaging elements whose shape can be changed may be provided. In addition, the set of elements may be driven separately, or may be divided and driven for each pixel or each pixel region.

[0027] (7) According to the configuration of this embodiment, since no optical prism is used, it is possible to realize a small-sized wide-field image acquiring optical device and wide-field imaging device. The imaging angle of view of the wide-field image acquiring optical device and wide-field imaging device is determined by the focal length (angle of view) of the imaging lenses 8, 9, 10, the number of imaging lenses 8, 9, 10, and the number and angle of the incidence directions of the optical member pairs 51, 52, 53. In addition, the specifications of the imaging lenses 8, 9, 10 and the optical waveguides 5, 6, 7 are determined based on the angle of view required for the acquired image.

[0028] Specifically, for example, if the angle of view (horizontal angle of view of the imaging range) of each of the optical member pairs 51, 52, 53 (imaging lenses 8, 9, 10) is 60 degrees or more, the optical member pairs 51, 52, 53 may be designed to have three pairs of optical members, and the directions of the common optical axes P11, P12, P13 of the optical member pairs 51, 52, 53 may be designed to have three directions. That is, as shown in Fig. 1, when the direction of the center (common optical axis P11) of the optical member pair 51 is set to 0 degrees, the common optical axis P12 of the optical member pair 52 may be rotated 60 degrees (-60 degrees) counterclockwise around the fulcrum P of the optical axis, and the common optical axis P13 of the optical member pair 53 may be rotated 60 degrees (+60 degrees) clockwise (180 degrees÷3=60 degrees).

[0029] Furthermore, by constructing the optical waveguides 5, 6, and 7 using FOPs of a reduction optical system, it is possible to arrange each optical component on the optical axis, which makes it possible to further suppress parallax (amount of occlusion). As a result, when images relating to each direction are synthesized, there is no disruption of continuity at the joints of the images, and a good wide-field image with a field of view of 180 degrees or more can be obtained. As described above, in the wide-field image acquisition optical device and wide-field imaging device according to this embodiment, various measures are taken to realize the compound-eye imaging method.

[0030] (Embodiment 1) Hereinafter, the wide-field image acquiring optical device and the wide-field imaging device 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> The basic configuration of the wide-field imaging device of this embodiment is shown in Figure 1 ((a) is a vertical cross-sectional view, and (b) is a perspective view seen from diagonally above). Here, an example is shown that uses three pairs of optical members 51, 52, and 53, each of which has a common optical axis with a different angle.

[0031] The wide-field imaging device of this embodiment includes an optical component pair 51 set so that a common optical axis P11 coincides with the optical axes of each imaging element 2, 3, and 4, an optical component pair 52 set so that a common optical axis P12 coincides with the optical axes of each imaging element 2, 3, and 4, and an optical component pair 53 set so that a common optical axis P13 coincides with the optical axes of each imaging element 2, 3, and 4. That is, the optical waveguides 5, 6, and 7 constituting the optical member pairs 51, 52, and 53 have planar light incident end faces 12A, 12B, and 12C that are approximately perpendicular to the common optical axis P11, P12, and P13, light propagation sections 14A, 14B, and 14C formed by bundling a plurality of optical fibers, and planar light emitting end faces 13A, 13B, and 13C that are approximately perpendicular to the common optical axis P11, P12, and P13 and emit light that is incident from the light incident end faces 12A, 12B, and 12C and propagated by the light propagation sections 14A, 14B, and 14C, and further, flat imaging elements 2, 3, and 4 (having planar light receiving surfaces) are arranged in close proximity to face the light emitting end faces 13A, 13B, and 13C.

[0032] <Basic configuration of wide-field image acquisition optical device> The basic configuration of the wide-field image acquisition optical device of this embodiment can be expressed by removing the configuration of the image pickup elements 2, 3, and 4 from the basic configuration of the wide-field imaging device of this embodiment described above. In FIG. 1, a11, a12, and a13 indicate the diameters of the imaging lenses 8, 9, and 10, b11, b12, and b13 indicate the back focal points of the imaging lenses 8, 9, and 10, and c11, c12, and c13 indicate the imaging ranges (diameters) of the light incident end faces 12A, 12B, and 12C of the optical waveguides 5, 6, and 7.

[0033] Incidentally, a general conventional imaging device has a schematic configuration as shown in FIG. 5(a) shows the simplest conventional imaging device. Light collected by an imaging lens 501 is imaged on the light receiving surface of an imaging element 502, which performs photoelectric conversion to obtain electrical image data. Moreover, 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. 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, and the optical image is captured by the imaging element 602. In contrast, the wide-field imaging device of this embodiment uses three optical component pairs 51, 52, and 53, 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.

[0034] That is, the angles of view of the imaging lenses 8, 9, and 10 in the three optical member pairs 51, 52, and 53 are all 60 degrees or more. On the other hand, the turning angles of these three imaging lenses 8, 9, and 10 are set to 0 degrees for the imaging lens 8, 60 degrees (-60 degrees) to the left (counterclockwise) for the imaging lens 9, and 60 degrees (+60 degrees) to the right (clockwise) for the imaging lens 10, with the fulcrum P of the optical axis (the point where the common optical axes P11, P12, and P13 of all the optical member pairs 51, 52, and 53 intersect) as the center, when the direction of light incidence from above that is perpendicular to the light receiving surface of the imaging element 2 (0 direction) is set to 0 degrees in Fig. 1. First, by making the three imaging lenses 8, 9, and 10 have the same specifications, setting the diagonal of the imaging range to an angle of view of 60 degrees or more (60 degrees x 3 = 180 degrees) as described above, and setting the direction of rotation of each imaging lens 8, 9, and 10 to the above-mentioned direction angles, it is possible to emit (project) wide-field optical images in three directions with angles of view of 60 degrees or more at each light exit end face 13A, 13B, and 13C of the optical waveguides 5, 6, and 7. Note that the optical waveguides 5, 6, and 7, which share an optical axis with the imaging lenses 8, 9, and 10, are also set to the direction angles of the imaging lenses 8, 9, and 10 described above.

[0035] It is also desirable to provide partitions 11 for preventing crosstalk between each of the optical member pairs 51, 52, 53 and adjacent to each of the optical member pairs 52, 53, and for this purpose it is essential to ensure gaps between each of the imaging elements 2, 3, 4. Note that crosstalk here refers to a phenomenon in which light incident from each member in the adjacent optical member pairs 51, 52, 53, or light incident from other optical lenses, etc., is reflected by various structures, members, etc., and appears in the acquired image as a ghost.

[0036] Here, the optical waveguide, which is a main component of the wide-field image acquisition optical device and wide-field imaging device 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 it 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 are stacked in multiple stages with these optical fibers arranged in parallel, and types in which multiple optical fiber components are bundled together. In the wide-field image acquisition optical device and wide-field imaging device according to the present embodiment, FOPs in which optical fibers are arranged in a fibrous form and formed into a plate shape are used as the optical waveguides 5, 6, and 7. However, other types of optical waveguides can of course be used for the wide-field image acquisition optical device and wide-field imaging device of the present invention. Note that crosstalk here refers to a state in which crosstalk occurs due to the members of the core glass portion and the clad glass portion becoming overlapped or entangled during the manufacture of the FOP.

[0037] In the optical waveguides 5, 6, and 7, the FOP is used, and when optical images from imaging lenses 8, 9, and 10 are formed on light incident end faces 12A, 12B, and 12C, respectively, as shown in FIG. 1, the optical images can be optically propagated to light exit end faces 13A, 13B, and 13C. In addition, by closely contacting the light receiving surfaces of the image pickup elements 2, 3, and 4, which are solid-state image pickup elements such as CMOS, the optical waveguides 5, 6, and 7 can effectively transmit the optical images formed on the light incident end faces 12A, 12B, and 12C to the image pickup elements 2, 3, and 4. That is, the optical images obtained by the imaging lenses 8, 9, and 10 are projected onto the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7. In addition to capturing the optical images by arranging the imaging elements 2, 3, and 4 in close proximity to (optically coupling) the light emitting end faces 13A, 13B, and 13C as in the wide-field imaging device of this embodiment, it is possible in the wide-field image acquisition optical device of this embodiment to directly view the optical images projected onto the light emitting end faces 13A, 13B, and 13C, or to capture these optical images with a separate camera.

[0038] By using the above-mentioned elemental technologies and configuring the optical waveguides 5, 6, 7 to have a shape according to the turning angle and imaging area of ​​each imaging lens 8, 9, 10 based on the number of imaging lenses 8, 9, 10, the focal lengths (angles of view) of the imaging lenses 8, 9, 10, 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 image seams.

[0039] Next, the imaging elements 2, 3, and 4 of the wide-field imaging device according to this embodiment will be described in more detail. In addition to the above-mentioned CMOS, solid-state imaging elements such as CCD and TFT can be used as the imaging elements 2, 3, and 4. 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 also be used instead of the imaging elements. Furthermore, when high-sensitivity photography is required, it is possible to use an image intensifier (II) or a microchannel plate (MCP). Also, photosensitive materials such as film can be used.

[0040] Furthermore, by arranging the planar light receiving surfaces of the imaging elements 2, 3, and 4 in close proximity to the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7, for example within 40 μm, it is possible to realize good wide-field imaging with an angle of view of 60 degrees or more for each. Note that minute gaps between the imaging elements 2, 3, and 4 and the optical waveguides 5, 6, and 7 that arise due to the close arrangement can be filled with a dedicated grease or the like to achieve good optical coupling between the opposing light receiving surfaces of the imaging elements 2, 3, and 4 and the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7, making it possible to obtain high-precision images without distortion. When actually obtaining a 180° wide-field-of-view image, each image can be similarly cropped so that the angle of view is 60°, and then the three cropped images can be displayed side-by-side, providing a wide-field-of-view image without parallax being a problem.

[0041] <Light propagation in optical waveguide> The FOP used in the optical waveguides 5, 6, and 7 shown in FIG. 1 is generally structured as a bundle of multiple optical fibers, as described above, and is composed of three types of glass structures: core glass, which is the light-transmitting portion; cladding glass, which is the light-blocking portion; and coupling glass, which prevents fiber crosstalk.

[0042] Generally, the core glass portion that propagates light is a linear straight fiber, the light incidence angle and the light emission angle are perpendicular to the light incident end faces 12A, 12B, 12C and the light emission end faces 13A, 13B, 13C of each optical waveguide 5, 6, 7, and the areas of each light incident end face 12A, 12B, 12C are the same, so that the emission ranges of light emitted from the light emission end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7 after light propagation are also the same. In other words, if the imaging ranges (diameters) c11, c12, c13 on the corresponding light incident end faces 12A, 12B, 12C of the imaging lens 8, imaging lens 9, imaging lens 10 are approximately the same, the ranges of the emitted light emitted from these light emission end faces 13A, 13B, 13C will also be approximately the same.

[0043] (Embodiment 2) A wide-field image acquisition optical device and a wide-field imaging device 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.

[0044] <Basic configuration of wide-field imaging device> The basic configuration of the wide-field imaging device of this embodiment will be described using an example in which three optical member pairs 151, 152, and 153 having different angles of their common optical axes are used, as shown in Fig. 2. Note that the optical member pair 151 is configured by arranging an imaging lens 108 and an optical waveguide 105 on a common optical axis P21, the optical member pair 152 is configured by arranging an imaging lens 109 and an optical waveguide 106 on a common optical axis P22, and the optical member pair 153 is configured by arranging an imaging lens 110 and an optical waveguide 107 on a common optical axis P23.

[0045] The wide-field imaging device of this embodiment is similar to that of embodiment 1 in that a common optical axis P21 is set to coincide with the optical axis of image sensor 102, a common optical axis P22 is set to coincide with the optical axis of image sensor 103, and a common optical axis P23 is set to coincide with the optical axis of image sensor 104. That is, the optical waveguides 105, 106, 107 constituting the optical element pairs 151, 152, 153 have light incident end faces 112A, 112B, 112C that are approximately perpendicular to the common optical axes P21, P22, P23, light propagation sections 114A, 114B, 114C consisting of a plurality of optical fibers, and planar light emitting end faces 113A, 113B, 113C that emit light that is incident from the light incident end faces 112A, 112B, 112C and propagated by the light propagation sections 114A, 114B, 114C, and are similar to those of embodiment 1 in that flat image pickup elements 102, 103, 104 (having planar light receiving surfaces) are arranged adjacent to and facing the light emitting end faces 113A, 113B, 113C.

[0046] However, in this embodiment, the light carrying the subject information imaged on the light incident end faces 112A, 112B, and 112C of the optical waveguides 105, 106, and 107 by the imaging lenses 108, 109, and 110 forms a reduced image at the light exit end faces 113A, 113B, and 113C (50% reduction in the embodiment of FIG. 2), which is different from the first embodiment. That is, in this embodiment, a (2:1) reduced optical system is used as the optical waveguides 105, 106, and 107. Therefore, compared to the structure of the first embodiment using a 1:1 optical system, the imaging surface of the imaging elements 102, 103, and 104 can be reduced, and the entire device can be made smaller, and further each component (lens, optical waveguide, imaging element) can be arranged close to the fulcrum P of the optical axis.

[0047] This makes it possible to minimize parallax, and when synthesizing wide-field-of-view images, it is possible to obtain the effect of smoothing the seams of the images. Also, on each of the light-emitting end faces 113A, 113B, and 113C, an image that is free of distortion and blur and reduced in size by 50% is displayed. Furthermore, since a space can be secured between each of the image pickup elements 102, 103, and 104, it becomes easy to provide the partition 11 in this gap. The reduction ratio of the reduction optical system can be freely set according to the shape and size of the lens and image sensor, the number of divisions, and the like. In addition, in the optical waveguides 105, 106, and 107, the core glass portion that propagates light is generally linear (straight fiber), but in this embodiment, it is preferable to use a fiber that is bent near the light incident end faces 112A, 112B, and 112C and near the light emitting end faces 113A, 113B, and 113C, as shown in Figure 2. However, in this embodiment, at the surface positions of the light incident end faces 112A, 112B, and 112C and the light emitting end faces 113A, 113B, and 113C, the optical fibers are set so as to be disposed perpendicular to these end faces.

[0048] <Basic configuration of wide-field image acquisition optical device> The basic configuration of the wide-field image acquisition optical device of this embodiment is similar to that of the first embodiment, except that the configuration of the image sensors 102, 103, and 104 is removed from the basic configuration of the wide-field imaging device of this embodiment. In addition, in Figure 2, a21, a22, and a23 indicate the diameters of the imaging lenses 108, 109, and 110, b21, b22, and b23 indicate the back focal points of the imaging lenses 108, 109, and 110, and c11, c12, and c13 indicate the imaging ranges (diameters) of the light incident end faces 22A, 22B, and 22C of the optical waveguides 105, 106, and 107.

[0049] (Embodiment 3) Hereinafter, a wide-field image acquisition optical device and a wide-field imaging device according to a third embodiment of the present invention will be described with reference to Fig. 3 ((a) is a vertical cross-sectional view, and (b) is a perspective view seen from diagonally above). Note that many of the components of the third embodiment are similar to those of the first embodiment, and the corresponding components are indicated by adding 200 to the reference numerals of the components of the first embodiment, and detailed descriptions thereof will be omitted. Moreover, the basic configuration of the wide-field imaging device of this embodiment will be described using an example in which three pairs of optical members 251, 252, and 253 having mutually different angles of their common optical axes are used, as shown in FIG.

[0050] Optical element pair 251 is formed by arranging an imaging lens 208 and an optical waveguide 205 on a common optical axis P31, optical element pair 252 is formed by arranging an imaging lens 209 and an optical waveguide 206 on a common optical axis P32, and optical element pair 253 is formed by arranging an imaging lens 210 and an optical waveguide 207 on a common optical axis P33.

[0051] In this embodiment, photoelectric conversion films 212, 213, and 214 are provided between light output end faces 213A, 213B, and 213C of optical waveguides 205, 206, and 207 each having light propagation portions 214A, 214B, and 214C, and the corresponding image pickup elements 202, 203, and 204. This makes it possible to significantly increase the image signal and improve the sensitivity. In addition, in FIG. 3, a31, a32, and a33 indicate the diameters of the imaging lenses 208, 209, and 210, b31, b32, and b33 indicate the back focal points of the imaging lenses 208, 209, and 210, and c31, c32, and c33 indicate the imaging ranges (diameters) of the light incident end faces 212A, 212B, and 212C of the optical waveguides 205, 206, and 207.

[0052] (Modifications) The wide-field image acquisition optical device and the wide-field imaging device of the present invention are not limited to those of the above-mentioned embodiment, and various other modifications are possible. For example, in the wide-field imaging device of the above-mentioned embodiment, the light incident end surface of the optical waveguide is flat, but instead, this light incident end surface can be curved (including spherical, cylindrical, etc.). Furthermore, the focal length, size, performance, etc. of the lens may be different for each imaging lens or may be the same.

[0053] Furthermore, when changing the lens specifications, it is necessary to change the back focus of the imaging lens (b11, b12, and b13 shown in FIG. 1 in the first embodiment, b21, b22, and b23 shown in FIG. 2 in the second embodiment, and b31, b32, and b33 shown in FIG. 3 in the third 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 engaged with the optical waveguide and can be moved perpendicularly to the light incident end face of the optical waveguide as necessary.

[0054] 4 shows the back focus adjustment mechanism for the imaging lens 308. The partition 311 is configured to hold a structure in which a lens holding part 351 that holds the lens 308 and a lens up-down movement mechanism 352 that adjusts the distance of the back focus b41 of the imaging lens 308 by moving the lens holding part 351 up and down are integrated together. Both side surfaces of the lens holding part 351 and the lens up-down movement mechanism 352 are screwed together like a screw, which makes it easy to change the back focus b41 and realizes a mechanism for movably holding the imaging lens 308. Since an adjustment mechanism is provided for each imaging lens independently, back focus adjustment is possible for each imaging lens, and even if there is variation in characteristics during the manufacturing process, it does not pose a problem in acquiring a wide-field image. Also, even if the focal length differs between the imaging lenses, the focus of the entire device can be easily adjusted.

[0055] 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.

[0056] In addition, in the wide-field image acquisition optical device of the above embodiment, a device is used that has the function of emitting an ultra-wide field image onto the light receiving surface of a flat image sensor, but instead, it is also possible to optically transmit an image signal related to light from the light emitting end face of the optical waveguide using an optical fiber or the like. [Explanation of symbols]

[0057] 2, 3, 4, 102, 103, 104, 202, 203, 204, 502, 602 Image sensor 5, 6, 7, 105, 106, 107, 205, 206, 207, 305, 603 optical waveguide 8, 9, 10, 108, 109, 110, 208, 209, 210, 308, 501, 601 Imaging lenses 11, 111, 211, 311 Bulkhead 12A, 12B, 12C, 112A, 112B, 112C, 212A, 212B, 212C Light entrance end face 13A, 13B, 13C, 113A, 113B, 113C, 213A, 213B, 213C Light output end face 14A, 14B, 14C, 114A, 114B, 114C, 214A, 214B, 214C Optical transmission section 51, 52, 53, 151, 152, 153, 251, 252, 253 Optical Component Pair 351 Lens holder 352 Lens vertical movement mechanism a11, a12, a13, a21, a22, a23, a31, a32, a33, a41 Imaging lens diameter b11, b12, b13, b21, b22, b23, b31, b32, b33, b41 Imaging lens back focus c11, c12, c13, c21, c22, c23, c31, c32, c33, c41 Imaging range of the light input end face of the optical waveguide (diameter) P (optical axis) fulcrum P11, P12, P13, P21, P22, P23, P31, P32, P33 (common) optical axis

Claims

1. A wide-field image acquisition optical device characterized in that optical element pairs, each of which has an imaging lens and an optical waveguide arranged in this order from the incident side of light carrying subject information, are each provided on a common optical axis extending in multiple directions.

2. The optical waveguide is configured so that each of the light incident end faces into which light from the imaging lens is incident is perpendicular to the optical axis of the corresponding imaging lens, and so that the optical image formed on each of the light incident end faces is propagated internally to the light exit end face that emits light to the outside.

3. 2. The wide-field image acquiring optical device according to claim 1, wherein the optical waveguide has a structure in which a plurality of optical fibers are bundled together.

4. 3. The wide-field image acquisition optical device according to claim 2, wherein the optical waveguide is a reduction optical system in which the diameter of the core portion at the light exit end face is smaller than the diameter of the core portion at the light input end face.

5. The wide-field image acquisition optical device according to claim 1, characterized in that at least one of the imaging lenses constituting the optical member pair is directly or indirectly attached to the optical waveguide so that the movement of the imaging lens in the optical axis direction is adjustable.

6. 2. The wide-field image acquiring optical device according to claim 1, wherein the image carrying the subject information is displayed on the light exit end surface of the optical waveguide so as to be visually recognizable.

7. 2. The wide-field image acquiring optical device according to claim 1, further comprising a means for evaluating an image carrying the subject information, the image being displayed on the light exit end surface of the optical waveguide.

8. A wide-field image acquisition optical device according to claim 1, a flat-plate-shaped imaging section for acquiring the subject information, the flat-plate-shaped imaging section being disposed opposite the light-emitting end face of the optical waveguide;

9. 9. The wide-field imaging device according to claim 8, wherein the imaging section is composed of one or more imaging elements that perform photoelectric conversion.

10. 9. The wide-field imaging device according to claim 8, wherein the imaging unit is a camera equipped with an imaging lens.

Images