Wide-angle view video acquisition optical device and wide-angle view imaging device

Abstract

To provide a compact wide-angle view video acquisition optical device and a wide-angle view imaging device, capable of photographing an image which is reduced in image distortion and is inconspicuous in a joint in synthesizing, while the image has a super wide-angle view.SOLUTION: Optical member pairs 51, 52, and 53 in which imaging lenses 8, 9, and 10 and optical waveguides 5, 6, and 7 are arranged in order from an incident side of light carrying subject information are arranged on common optical axes P11, P12, and P13 extending in a plurality of directions respectively. At least one of the light incident end faces 12A, 12B, and 12C and light emission end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7 is configured so as to form a curved surface shape. An imaging element 2 forming the curved surface shape is arranged adjacent to the light emission end faces 13A, 13B, and 13C.SELECTED DRAWING: Figure 1A

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). In addition, there is known a device that captures an image of a wide field of view (all directions) by using a camera with a cylindrical lens arranged facing outward (see, for example, Patent Document 3 below).

[0004] Furthermore, in a camera using a double-image eye system known as TOMBO, a shooting technique using multiple lens groups has been proposed (see, for example, Patent Document 4 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 2004-61808 A [Patent Document 4] 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, multiple cameras are arranged, but as the number of cameras increases, restrictions imposed by the size of the camera bodies result in the fulcrum of the optical axes of the multiple cameras and lenses (support rod 10 in Patent Document 3) and the distance between the cameras becoming significantly longer. This causes parallax in the output images from each camera, and when a single wide-field (panoramic) image is formed, inconsistencies occur at the joints between each image.

[0009] Furthermore, Patent Document 4 employs a method of dividing a planar imaging element into multiple imaging regions and combining the images from each region. However, since the imaging element itself is planar and the difference in the shooting direction of each image (parallax) is extremely small, it is difficult to achieve wide-field shooting. In addition, the technology in Non-Patent Document 1 adds multiple prisms to the technology in Patent Document 4, but this has various problems, such as the system becoming larger, the seams being noticeable when the images formed by each compound lens are combined, and curved distortion caused by the lenses, and so on, and does not result in an improvement in image quality.

[0010] 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]

[0011] The wide-field image acquisition optical device of the present invention comprises: 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 provided on a common optical axis extending in multiple directions, and at least one of the light incident end face and the light exit end face of the optical waveguide has a curved shape. Here, the optical waveguide can be configured so that multiple stages are superimposed in series. In that case, the "light incident end face" refers to the light incident end face of the optical waveguide located closest to the light incident side, and the "light exit end face" refers to the light exit end face of the optical waveguide located closest to the light exit side (the same applies below). 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).

[0012] The curved surface of the optical waveguide is preferably either a concave or convex shape. 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 constituting the optical member pair is directly or indirectly attached to the optical waveguide so that movement of the imaging lens in the optical axis direction is adjustable. Furthermore, in this wide-field image acquisition optical device, the optical waveguide can be a reduction optical system that reduces the diameter of the core portion at the light exit end face compared to the diameter of the core portion at the light entrance end face, or an expansion optical system that expands the diameter.

[0013] Further, the wide-field imaging device of the present invention comprises: The above-mentioned wide-field image acquiring optical device is characterized in that an image acquiring section having a curved light incident end surface is disposed close to the light exit end surface of each of the optical waveguides. It is also preferable that the image acquisition unit is an image pickup element.

[0014] The imaging element may be configured to be composed of a plurality of imaging element portions, or may be configured to be composed of a plurality of regions that can be driven in a divided manner. It is also preferable that the light exit end face of the optical waveguide and the light entrance end face of the image sensor have the same curved shape. The light incident end face and the light exit end face of the optical waveguide and the light incident end face of the imaging element may be formed in a spherical shape, a hemispherical shape, a cylindrical shape, or a semi-cylindrical shape. In addition, in this wide-field imaging device, the optical waveguide can be a reduction optical system that reduces the diameter of the core portion at the light exit end face compared to the diameter of the core portion at the light entrance end face, or a magnification optical system that enlarges the diameter. Effect of the Invention

[0015] According to the wide-field image acquisition optical device of the present invention, optical component pairs each having 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, and at least one of the light incident end face and light exit end face of the optical waveguide is configured to have a curved shape.This makes it possible to construct a compact optical device that can capture an ultra-wide field of view image with reduced image distortion and inconspicuous seams when combined. Furthermore, according to the wide-field imaging device of the present invention, in the above-mentioned wide-field image acquisition optical device, an image acquisition section (e.g., an image sensor) having a curved light incident end face is arranged close to the light exit end face of each of the optical waveguides, so that, like the above-mentioned wide-field image acquisition optical device, it is possible to construct an optical device with excellent compactness that can capture an ultra-wide field of view image with reduced image distortion and inconspicuous seams when combined. Furthermore, according to the wide-field image acquisition optical device and wide-field imaging device of the present invention, at least one of the light input end face and the light output end face of the optical waveguide is curved in shape, which increases the degree of freedom in relation to the shape of devices such as an imaging element or measuring instrument to be positioned on the light output end face side, and enables the device to be made more compact. [Brief description of the drawings]

[0016] [Figure 1A] 1A and 1B are conceptual diagrams showing the structures of a wide-field image acquisition optical device and a wide-field imaging device according to a first embodiment of the present invention ((a) is a cross-sectional view, and (b) is a perspective view). [Figure 1B] 1A shows a cross-sectional view and a ray trajectory diagram of a wide-field imaging device according to an embodiment of the present invention, and FIG. 1B shows a conventional general imaging device. [Figure 2A] 1A and 1B are cross-sectional views showing the shape of an optical waveguide in a wide-field imaging device according to an embodiment of the present invention ((a) is a plano-concave shape, and (b) is a plano-convex shape). [Figure 2B] 5A and 5B are cross-sectional views showing the shape of an optical waveguide in a wide-field imaging device according to an embodiment of the present invention ((c) is a concave-convex shape, and (d) is a convex-concave shape). [Figure 2C] 4A and 4B are cross-sectional views showing the shapes of optical waveguides in a wide-field imaging device according to an embodiment of the present invention ((e) is a concave-flat shape, and (f) is a convex-flat shape). [Figure 2D] FIG. 13 is a cross-sectional view showing the shapes of the imaging lens, optical waveguide, and imaging element in a wide-field imaging device according to an embodiment of the present invention ((g) is a plano-convex imaging lens, a plano-concave optical waveguide, and an imaging element with a convex shape on the light incident side and a concave shape on the light exit side; (h) is a plano-convex imaging lens, an optical waveguide with a convex shape on the light incident side and a concave shape on the light exit side, and an imaging element with a convex shape on the light incident side and a concave shape on the light exit side). [Diagram 3] 5A to 5D are conceptual diagrams showing the structures of a wide-field image acquisition optical device and a wide-field imaging device according to a second embodiment of the present invention ((a) is a cross-sectional view, (b) is a partially enlarged view, (c) is a schematic bottom view, and (d) is a perspective view). [Figure 4] 10A to 10D are conceptual diagrams showing the structures of a wide-field image acquisition optical device and a wide-field imaging device according to a third embodiment of the present invention ((a) is a longitudinal sectional view, (b) is a partially enlarged view, (c) is a schematic bottom view, and (d) is a perspective view). [Diagram 5] 10A to 10D are conceptual diagrams showing the structures of a wide-field image acquisition optical device and a wide-field imaging device according to a fourth embodiment of the present invention ((a) is a cross-sectional view, (b) is a partially enlarged view, (c) is a schematic bottom view, and (d) is a schematic front view). [Figure 6] 5 is a conceptual diagram showing the structure of a wide-field image acquisition optical device and a wide-field imaging device according to embodiment 5 of the present invention ((a) is a cross-sectional view, (b) is a partially enlarged view, (c) is a schematic partial cross-sectional view seen from the front, and (d) is a schematic front view). [Figure 7] FIG. 2 is a schematic diagram showing an example of a mechanism for changing the back focus of the imaging lens according to each embodiment of the present invention. [Figure 8] 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

[0017] Below, we will explain the wide-field image acquisition optical device and wide-field imaging device according to the embodiments of the present invention. First, we will explain the overview and features of this embodiment, and then we will explain each embodiment (embodiments 1 to 5) in detail. 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.

[0018] (Outline of this embodiment) First, an overview of the wide-field image acquiring optical device according to this embodiment will be described with reference to FIG. 1A 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.

[0019] Furthermore, each optical waveguide 5, 6, 7 has 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 on a circumference (sphere) centered on fulcrum P of the optical axis, and which emit the light propagated by these light propagation sections 14A, 14B, 14C to the outside.

[0020] On the other hand, the wide-field imaging device of this embodiment is equipped with the above-mentioned wide-field image acquisition optical device, and is equipped with a curved imaging section (image sensor 2 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 each light output end face 13A, 13B, 13C in Figure 1).

[0021] It should be noted that the above-mentioned wide-field imaging device is used, for example, when outputting an electrical video signal related to the image of a subject captured by an imaging element, whereas the above-mentioned wide-field image acquisition optical device is used not only when an imaging element is added and such an electrical video signal is output, but also when the optical image displayed at the output portion of the optical waveguide can be directly viewed, and this image can be observed and evaluated, or this optical image can be connected to a measuring instrument such as a microscope for measurement and evaluation.

[0022] Here, the optical waveguides 5, 6, and 7, which are one of the components, are optical members that have the function of outputting incident light to the output side, and include a configuration in which optical waveguides consisting of one-dimensionally arranged cores and clad layers are stacked in multiple stages, and a configuration in which multiple optical fibers are bundled. A representative example of this optical waveguide is a Fiber Optics Plate (FOP), in which optical fibers are arranged in a fibrous form to form a plate. The function of the optical waveguide is, for example, as shown in FIG. 8(b), to optically propagate an optical image from an imaging lens 601 to the output side surface of the FOP 603 by forming the optical image on the input side surface of the FOP 603. In other words, since the optical image obtained by the lens is projected on the output side of the FOP 603, an image can be obtained by arranging (optically coupling) an imaging element 602, as well as visual confirmation. Based on this elemental technology, by appropriately arranging the number of imaging lenses, the focal length (angle of view) per lens, the turning angle based on the fulcrum of the optical axis (P: see Figure 1A), and the optical waveguide (such as FOP) according to the imaging area and the shapes of the input and output sides, it is possible to obtain a wide-field optical image without distortion and with no visible seams in the image.

[0023] Next, Fig. 1B(a) shows a cross-sectional view and a ray trace diagram of the wide-field imaging device according to this embodiment. For comparison with this embodiment, Fig. 1B(b) shows a cross-sectional view and a ray trace diagram of a conventional wide-field imaging device. 1B(a), from the light incident side, a subject 30, an imaging lens 8p, a curved optical waveguide 5p, and a curved imaging element 2p are arranged at appropriate positions. The curved optical waveguide 5p and the curved imaging element 2p are arranged so as to abut against each other. In particular, the curved optical waveguide 5p has a concave light incidence end surface, which is configured to obtain the effect of reducing the influence of field curvature distortion and chromatic aberration in the peripheral area of ​​the image that occurs between the pair of the imaging lens 8p and the optical waveguide 5p. In other words, if the light incidence surface of the optical waveguide 5p is set at the point where the light rays in the peripheral area of ​​the image converge, peripheral image distortion can be suppressed even if the angle of view per lens is increased, and as a result, the number of imaging lenses can be reduced to achieve miniaturization. In addition, when the shapes of the light input end face and the light output end face of the optical waveguide 5p are both curved (for example, the shapes shown in Figs. 2B(c) and (d)), or when only the light output end face is curved (for example, the shapes shown in Figs. 2A(a) and (b)), it is convenient to arrange the individual optical waveguides 5p in close proximity in combination with a curved imaging element 2p, and good images can be easily obtained. Furthermore, compared to the case of arranging a flat imaging element, an efficient arrangement can be realized even when the radius of curvature is small, and therefore miniaturization can be achieved. 1B(b), the image information of the subject 730 carried by the incident light is imaged on the flat image sensor 702 by the imaging lens 708p, but the effect of the present embodiment is not achieved. Specifically, the effect of increasing the degree of freedom of component arrangement for compactification of the device, or reducing curvature of field and chromatic aberration cannot be achieved.

[0024] (Features of this embodiment) 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).

[0025] (2) The light focused on the light incident end faces 12A, 12B, 12C of the optical waveguides 5, 6, 7 by the imaging lenses 8, 9, 10 directed in each direction (having mutually different optical axis directions) is adjusted so that the light emitted from the light exit end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7 is in the direction of the same fulcrum P. Here, at least one of the light incident end faces 12A, 12B, 12C and the light exit end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7 is curved. The combinations of the shapes of the light incident end faces 12A, 12B, and 12C and the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7 are shown in, for example, Figures 2A, 2B, and 2C, and the technical term "curved surface" is used as a concept that encompasses each of these shapes. Furthermore, this "curved surface" includes not only spherical surfaces, but also aspherical surfaces and free-form surfaces. Specifically, as shown in FIG. 2A, this includes the case of optical waveguide 13a (a) having a flat light incident side and a concave light exit side, and the case of optical waveguide 13b (b) having a flat light incident side and a convex light exit side. Also, as shown in FIG. 2B, this includes the case of optical waveguide 13c having a concave light incident side and a convex light exit side (c), and the case of optical waveguide 13d having a convex light incident side and a concave light exit side (d). Also, as shown in FIG. 2C, this includes the case (e) of optical waveguide 13e which has a concave light incident side and a flat light exit side, and the case (f) of optical waveguide 13f which has a convex light incident side and a flat light exit side. Note that Figure 2D shows cross-sectional views of the shapes of the imaging lens, optical waveguide, and imaging element in the wide-field imaging device of this embodiment ((g) shows imaging lens 8a with a plano-convex shape, optical waveguide 13a with a plano-concave shape, and imaging element 2a with a convex shape on the light incident side and a concave shape on the light exit side; (h) shows imaging lens 8d with a plano-convex shape, optical waveguide 13d with a convex shape on the light incident side and a concave shape on the light exit side, and imaging element 2d with a convex shape on the light incident side and a concave shape on the light exit side).

[0026] (3) Furthermore, a wide-field imaging device is constructed when a curved-surface type imaging element (including an imaging element group) 2 is provided on the same curved surface (circumferential surface) F11 (see FIG. 1A) as the light-emitting end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7. When the light-emitting end faces 13A, 13B, 13C of the optical waveguides 5, 6, 7 are flat (therefore, the light-incident end faces of the optical waveguides are curved), this wide-field imaging device is constructed by arranging a normal flat-surface type imaging element (including an imaging element group) along the light-emitting end faces 13A, 13B, 13C. (4) However, it is not necessary to provide an imaging element (group), and imaging is possible, for example, by re-imaging using a lens-equipped camera. In such a case, the imaging element (including the imaging element group) may be removed from the configuration of the wide-field imaging device, thereby forming a wide-field image acquisition optical device. In addition, in the above-mentioned wide-field imaging device, if the light-emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7 are observed visually or with a measuring instrument such as an optical microscope, it can be used as an evaluation device and optical measurements and evaluations of the imaging lenses 8, 9, and 10 and the optical waveguides 5, 6, and 7 can be performed.

[0027] (5) Furthermore, each of the optical waveguides 5, 6, and 7 having the above-mentioned characteristics may be in an integrated form, or in a form in which a plurality of separate waveguides are provided. (6) The curved imaging element 2 described above may be in an integrated form as shown in FIG. 1A, or in a multiple separate form. Furthermore, the imaging element 2 in an integrated form or in a multiple separate form may be configured to be divided and driven for each pixel or for each specified area. (7) If the light incident end faces 12A, 12B, and 12C of the optical waveguides 5, 6, and 7 are formed into concave curved surfaces, it is possible to reduce distortion, particularly peripheral distortion, that occurs in the imaging lens.

[0028] (8) 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.

[0029] 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. 1A, 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). If the output side of the optical waveguide is a curved surface, a compact wide-field imaging device can be constructed by arranging an imaging element having a curved shape (hereinafter referred to as a curved type) that fits along the curved surface. The wide-field image acquiring optical device and wide-field imaging device according to this embodiment are configured to realize a compound-eye imaging method using a plurality of imaging lenses 8, 9, and .

[0030] (9) Furthermore, by constructing the optical waveguides 5, 6, and 7 using the FOP of the reduction optical system, it is possible to arrange each optical component on the common optical axis P11, P12, and P13. This makes it possible to further suppress parallax (amount of occlusion). As a result, when images relating to each direction are synthesized, continuity is not broken at the joints of the images, and a good wide-field image with an angle of view of 180 degrees or more can be obtained. Moreover, it is of course possible for the optical waveguides 5, 6, and 7 to be constructed by FOPs of a magnifying optical system.

[0031] Hereinafter, specific configurations of the wide-field image acquiring optical device and the wide-field imaging device according to each of the first to fifth embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) 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 Fig. 1A ((a) is a cross-sectional view, and (b) is a schematic perspective view seen from two oblique directions). Here, an example is shown in which three optical member pairs 51, 52, and 53 having mutually different angles of a common optical axis are used. Also, in embodiment 1, as shown in Fig. 1A, the light incident end faces 12A, 12B, and 12C of each of the optical waveguides 5, 6, and 7 are flat, and the light exit end faces 13A, 13B, and 13C are curved.

[0032] The wide-field imaging device of this embodiment includes an optical element pair 51 set so that a common optical axis P11 coincides with the optical axes of the imaging lenses 8, 9, and 10, an optical element pair 52 set so that a common optical axis P12 coincides with the optical axes of the imaging lenses 8, 9, and 10, and an optical element pair 53 set so that a common optical axis P13 coincides with the optical axes of the imaging lenses 8, 9, and 10. That is, the optical waveguides 5, 6, and 7 constituting the optical member pairs 51, 52, and 53 include planar light incident end faces 12A, 12B, and 12C that are approximately perpendicular to the common optical axes P11, P12, and P13, light propagation sections 14A, 14B, and 14C formed by bundling a plurality of optical fibers, and curved light exit end faces 13A, 13B, and 13C that 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, as well as a curved imaging element 2 that is integrally arranged along each of the curved light exit end faces 13A, 13B, and 13C.

[0033] <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 sensor 2 from the basic configuration of the wide-field imaging device of this embodiment described above. In FIG. 1A, a11, a12, and a13 indicate the diameters of the imaging lenses 8, 9, and 10, b11, b12, and b13 indicate the back focal lengths 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.

[0034] <Other configurations> Incidentally, a general conventional imaging device has a schematic configuration as shown in FIG. 8(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 image data electrically. Also, FIG. 8(b) shows a conventional imaging device (e.g., Patent No. 6518038, etc.) in which a field optical path (FOP) 603 is inserted between an imaging lens 601 and an imaging element 602. The imaging lens 601 forms an optical image on the light incident end surface of the optical waveguide (FOP) 603, and the optical image is propagated inside the FOP 603, and the optical image is projected on the light exit end surface, so that the optical image is captured by the imaging element 602.

[0035] In contrast, the wide-field imaging device of embodiment 1 uses three optical element pairs 51, 52, and 53, as shown in FIG. 1A, and the field of view and turning angles are set as follows, which is a significant difference from the above-mentioned conventional technologies. 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. 1A. 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.

[0036] Furthermore, if the light receiving portion of the curved imaging element 2 is arranged close to each of the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7 within a range of 5 μm to 200 μm, a single imaging element 2 having a curved shape can realize wide-field imaging with an angle of view of 180 degrees. Here, by using a dedicated grease for both the light emitting end faces 13A, 13B, and 13C and the light receiving portion of the curved imaging element 2, the adhesion between them can be made good. The distance between the light emitting end faces 13A, 13B, and 13C and the light receiving portion of the imaging element 2 is set to 5 μm or more in order to facilitate manufacturing, and is set to 200 μm or less in order to achieve the effect of compacting the device without causing image blur. More preferably, the distance is set to a range of 10 μm to 100 μm, and by setting the distance in this range, manufacturing becomes easier and the effect of compacting the device can be achieved. A particularly preferred range is 30 μm or more and 50 μm or less (for example, 40 μm). By setting the thickness in this range, production becomes easier and the effect of making the device more compact can be achieved. As described above, the image sensor 2 may be composed of one image sensor as shown in Fig. 1A, or may be composed of multiple image sensors. The image sensor 2 may be divided into pixels or pixel regions, and the captured images may be combined before being output. As the curved imaging element 2, for example, in addition to the above-mentioned CMOS, a solid-state imaging element such as a CCD or a TFT is used. In this embodiment, the meaning of the technical term imaging element is broadly interpreted to include photosensitive materials such as silver halide film. Furthermore, in optically coupling the optical waveguides 5, 6, and 7 with the curved imaging element 2, an optical waveguide for optical imaging may be inserted into the gap between the two members. The coupling of these two optical waveguides (FOP) is already known to be able to improve the adhesion between the FOPs by using a dedicated grease, and this allows for good optical coupling between the optical waveguides 5, 6, and 7 and the curved imaging element 2.

[0037] Here, a supplementary explanation will be given regarding the optical waveguides 5, 6, and 7 described above. That is, the FOP constituting the optical waveguides 5, 6, and 7 used in embodiment 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-shielding portion, and coupling glass for preventing fiber crosstalk.

[0038] In the optical waveguides 5, 6, and 7 used in embodiment 1, the core glass portion that propagates light is a linear straight fiber, and the area and shape of each of the light incident end faces 12A, 12B, and 12C are similar, and the area and shape of each of the light emitting end faces 13A, 13B, and 13C are also similar, so that the emission ranges of the light emitted from the light emitting end faces 13A, 13B, and 13C of the optical waveguides 5, 6, and 7 after light propagation are also similar to one another. In other words, if the imaging ranges (diameters) c11, c12, and c13 on the corresponding light incident end faces 12A, 12B, and 12C of the imaging lenses 8, 9, and 10, respectively, are approximately the same, the ranges of the emitted light emitted from the light emitting end faces 13A, 13B, and 13C are also configured to be approximately the same.

[0039] 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 a gap between each of the optical member pairs 51, 52, 53. 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 as a ghost in the acquired image.

[0040] (Embodiment 2) Hereinafter, 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 with reference to Fig. 3 ((a) is a cross-sectional view, (b) is a partially enlarged view of (a), (c) is a schematic bottom view, and (d) is a schematic perspective view seen from diagonally above). Note that, among the components of the second embodiment, those corresponding to those of the first embodiment are indicated by adding 100 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 and wide-field imaging device according to the second embodiment show a case in which the numbers of imaging lenses 108 and optical waveguides 105 are increased compared to the above-mentioned embodiment 1. When the number of imaging lenses 108 is increased in this way, the shape of the optical waveguide approaches a cylindrical shape, and the imaging range covered by one imaging lens 108 becomes smaller.

[0041] Specifically, as shown in FIG. 3(a), the wide-field imaging device of embodiment 2 has 25 imaging lenses 108 arranged on the outer peripheral surface of the optical waveguide 105 in the circumferential direction of the large diameter, and the angle of view of the imaging range of each imaging lens 108 is 7.2 degrees. Here, the angle of view of the imaging range means the angle of view in the horizontal direction to be precise (this also applies to the "angle of view of the imaging range" described in the following paragraphs 0043, 0044, and 0045). That is, this shows a form in which the center of the imaging range is the center of the acquired image and the angle of view in the horizontal direction is 7.2 degrees or more. Furthermore, when the angle of view in the horizontal direction is larger than 7.2 degrees, it is possible to obtain an image with a wide field of view of 180 degrees by cutting out (trimming) the 7.2 degrees as the horizontal angle of view and performing image processing to continuously stitch the images together. Note that, for the angle of view in the vertical direction, since no image stitching processing is required to make it 180 degrees, it is sufficient to have an angle of view of 7.2 degrees or more and to satisfy the required angle of view of the imaging range (angle of view in the vertical direction) (this also applies to the "angle of view of the imaging range" described in the following paragraphs 0043, 0044, and 0045). In addition, the circle on which the imaging lenses 108 are arranged has a radius of curvature that takes into consideration the back focal length, and an optical waveguide 105, both of whose light entrance and exit ends are curved, is arranged on the inner circumference to correspond to each imaging lens 108, thereby forming a wide-field image acquisition optical device. Furthermore, by arranging a curved imaging element 102 integrally formed according to this radius of curvature close to the inner circumference side (light emitting end face side) of each optical waveguide 105, a wide-field imaging device that captures wide-field images can be constructed.

[0042] 3(b) is an enlarged structural diagram of one imaging lens in FIG. 3(a), showing the imaging lens 108, optical waveguide 105, and imaging element 102 arranged in that order from the light incidence direction. A partition 111 is provided to prevent interference (crosstalk) from light that has passed through adjacent lenses. The imaging lens 108 is shown held by a lens holder 115 supported by the partition 111. The lens holder 115 will be described later. 3(c) and 3(d), this wide-field imaging device has imaging lenses 108 regularly arranged on the outer circumferential surface of a cylindrical optical waveguide 105, and incident light from a direction 0 perpendicular to the axis of the cylindrical optical waveguide 105 is irradiated onto this circumferential surface, as shown in FIG. 3(c) and FIG. 3(d). It also shows that an imaging element 102 is disposed along the inner circumferential surface (light-emitting end surface) of the cylindrical optical waveguide 105. When the number of imaging lenses 108 increases, the imaging lenses 108 and a structure supporting them can be integrated into an array structure.

[0043] (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. 4 ((a) is a cross-sectional view, (b) is a partially enlarged view of (a), (c) is a schematic bottom view, and (d) is a schematic perspective view seen from diagonally above). Note that, among the components of the third embodiment, those corresponding to those of the second embodiment are indicated by adding 100 to the reference numerals of the components of the second embodiment, and detailed description thereof will be omitted. The wide-field image acquisition optical device and wide-field imaging device according to the third embodiment are different in that, whereas the overall shape of the second embodiment is semi-cylindrical, the overall shape of the third embodiment is cylindrical. 4(a), the wide-field image acquiring optical device and wide-field imaging device according to the third embodiment show a configuration in which 50 imaging lenses 208 arranged on the outer peripheral surface of the optical waveguide 205 are arranged in the major diameter circumferential direction, and the angle of view of the imaging range of each imaging lens 208 is 7.2 degrees. In other respects, they are similar to the wide-field image acquiring optical device and wide-field imaging device according to the second embodiment.

[0044] (Embodiment 4) A wide-field image acquisition optical device and a wide-field imaging device according to a fourth embodiment of the present invention will be described below with reference to Fig. 5 ((a) is a cross-sectional view, (b) is a partially enlarged view of (a), (c) is a schematic bottom view, and (d) is a schematic front view). Note that, among the components of the fourth embodiment, those corresponding to those of the second embodiment are indicated by adding 200 to the reference numerals of the components of the second embodiment, and detailed description thereof will be omitted. The wide-field image acquisition optical device and wide-field imaging device according to the fourth embodiment are different in that, whereas the overall shape of the second embodiment is semicylindrical, the overall shape of the fourth embodiment is hemispherical. 5(a), the wide-field image acquiring optical device and wide-field imaging device according to the fourth embodiment show a configuration in which the number of imaging lenses 308 arranged in the major diameter circumferential direction on the outer peripheral surface of the optical waveguide 305 is 25, and the angle of view of the imaging range of each imaging lens 308 is 7.2 degrees. In other respects, they are similar to the wide-field image acquiring optical device and wide-field imaging device according to the second embodiment.

[0045] (Embodiment 5) A wide-field image acquisition optical device and a wide-field imaging device according to a fifth embodiment of the present invention will be described below with reference to Fig. 6 ((a) is a cross-sectional view, (b) is a partial enlarged view of (a), (c) is a schematic partial cross-sectional view seen from the front, and (d) is a schematic front view). Note that, among the components of the fifth embodiment, those corresponding to those of the fourth embodiment are indicated by adding 100 to the reference numerals of the components of the fourth embodiment, and detailed description thereof will be omitted. The wide-field image acquisition optical device and wide-field imaging device according to the fifth embodiment are different in that the overall shape is spherical, whereas the overall shape of the fourth embodiment is hemispherical. 6(a), the wide-field image acquiring optical device and wide-field imaging device according to the fifth embodiment show a configuration in which 50 imaging lenses 408 arranged on the outer peripheral surface of the optical waveguide 405 are arranged in the major diameter circumferential direction, and the angle of view of the imaging range of each imaging lens 408 is 7.2 degrees. In other respects, they are similar to the wide-field image acquiring optical device and wide-field imaging device according to the fourth embodiment.

[0046] (Adjusting the position of parts) 7 shows the back focus adjustment mechanism 817 for the imaging lens 808. The imaging lens 808, the optical waveguide 805, and the imaging element 802 are arranged in this order from the light incidence direction (direction 0). The partition wall 811 is configured to hold a structure in which a lens holding part 851 that holds the imaging lens 808 and a lens vertical movement mechanism 852 that adjusts the back focus distance of the imaging lens 808 by moving the lens holding part 851 up and down are integrated together. Both side surfaces of the lens holding part 851 and the lens vertical movement mechanism 852 are screwed together like a screw, which makes it easy to change the back focus and realizes a mechanism for movably holding the imaging lens 808.

[0047] 7 is provided with a lens insertion section 861 into which a correction lens 801 is inserted and held for the purpose of improving image quality in the peripheral areas of an image. The outer surface of the lens insertion section 861 is structured to be screwed into the inner surface of the lens vertical movement mechanism section 852, and by combining the lens 801 as required with the imaging lens 808, the imaging lens 808 can be realized as a combination lens. Since an adjustment mechanism is provided independently for each imaging lens 808 with a different light incidence direction, back focus adjustment is possible for each imaging lens, and even if there is variation in characteristics during the manufacturing process, this does not pose a problem in acquiring a wide-field image. Also, even if the focal lengths of the imaging lenses 808 are different, the focus of the entire device can be easily adjusted.

[0048] However, when a configuration is made up of more imaging lenses, the light incident from the imaging lenses 108, 208, 308, 408 whose optical axes are tilted by ±70 degrees or more will have a large angle with respect to the 0 direction, which is the light incident direction, in the configurations shown in the above embodiments 2 to 5, for example. However, since the optical axes of the imaging lenses 108, 208, 308, 408 and the core glass portions of the corresponding optical waveguides 105, 205, 305, 405 are aligned, even if the imaging lenses 108, 208, 308, 408 are angled from the center 0 degrees (0 direction in Figures 3(a), 4(a), 5(a), and 6(a)), they can receive light in the designed direction, thereby achieving imaging with a wide viewing angle.

[0049] (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. Furthermore, when the specifications of the imaging lens are changed, it is necessary to change the back focus of the imaging lens (for example, b11, b12, and b13 shown in FIG. 1 in the first embodiment). Therefore, when there is a possibility of changing such lens specifications, it is preferable to use, for example, the method described with reference to FIG. 7 to indirectly or directly engage the imaging lens with the optical waveguide and to provide a configuration that allows the imaging lens to be moved perpendicularly to the light incident end face of the optical waveguide as necessary.

[0050] In addition, in the above embodiment, an imaging element is used close to the light output end face of the optical waveguide as the image acquisition 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.

[0051] 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. In addition, in the above embodiment, a function of emitting an ultra-wide field of view image onto the light receiving surface of the imaging element is used, but instead of this, 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]

[0052] 2, 2a, 2d, 2p, 102, 202, 302, 402, 502, 602, 702, 802 Image sensor 5, 6, 7, 5p, 13a, 13b, 13c, 13d, 13e, 13f, 105, 205, 305, 405, 603, 805 optical waveguide 8, 9, 10, 8a, 8d, 8p, 108, 208, 308, 408, 501, 601, 708p, 808 Imaging Lens 11, 111, 211, 311, 411, 811 Bulkhead 12A, 12B, 12C Light incidence end face 13A, 13B, 13C Light output end face 14A, 14B, 14C Optical transmission section 30, 730 Subject 51, 52, 53 Optical component pair 115, 215, 315, 415, 851 Lens holder 801 Lens 817 Back focus adjustment mechanism 852 Lens vertical movement mechanism 861 Lens insertion part a11, a12, a13 Diameter of imaging lens b11, b12, b13 Back focus of imaging lens c11, c12, c13 Imaging range of the light input end face of the optical waveguide (diameter) P (optical axis) fulcrum P11, P12, P13 (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 provided on a common optical axis extending in multiple directions, and at least one of the light incident end face and light exit end face of the optical waveguide has a curved shape.

2. 2. The wide-field image acquiring optical device according to claim 1, wherein the curved surface of the optical waveguide is either concave or convex.

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. 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.

5. The wide-field image acquisition optical device of any one of claims 1 to 4, characterized in that the optical waveguide is a reduction optical system that reduces the diameter of the core portion of the light emitting end face to be smaller than the diameter of the core portion of the light incident end face, or an expansion optical system that expands the diameter.

6. 2. A wide-field imaging device comprising the wide-field image acquisition optical device according to claim 1, and an image acquisition section having a curved light input end surface disposed close to the light output end surface of each of the optical waveguides of the wide-field image acquisition optical device.

7. The wide-field imaging device according to claim 6 , wherein the image acquisition unit is an image sensor.

8. 8. The wide-field imaging device according to claim 7, wherein the imaging element is configured to be composed of a plurality of imaging element portions or a plurality of regions that can be driven separately.

9. 8. The wide-field imaging device according to claim 7, wherein the light exit end face of the optical waveguide and the light entrance end face of the imaging element have the same curved shape.

10. 8. The wide-field imaging device according to claim 7, characterized in that the light incident end face and the light exit end face of the optical waveguide and the light incident end face of the imaging element are either spherical, hemispherical, cylindrical or semi-cylindrical in shape.

11. A wide-field imaging device as described in any one of claims 6 to 10, characterized in that the optical waveguide is a reduction optical system that reduces the diameter of the core portion at the light emitting end face to be smaller than the diameter of the core portion at the light incident end face, or an expansion optical system that expands the diameter.

Images