Optical system, imaging device, and projection device

Abstract

An optical system 10 comprises an imaging element 11 that converts light into an electrical signal, a lens 12 that refracts and converges the light, and a prism 13 that is arranged in an optical path between the imaging element 11 and the lens 12, wherein a virtual image 15 of the light receiving surface of the imaging element 11 is formed in the prism 13, and a focal plane 16 is positioned conjugate with the virtual image 15 with the lens 12 interposed therebetween.

Description

[Technical field]

[0001] The present invention relates to an optical system used for focusing, and an imaging device and a projection device that use the optical system. [Background technology]

[0002] 2. Description of the Related Art In an imaging device used for object recognition such as face recognition and iris recognition, which captures an image of an object having a depth difference, an image in which the entire surface of the object is in focus is required to improve the accuracy of the authentication and recognition.

[0003] Also, in a projection device that projects and displays an image on a projection surface such as a screen having a depth difference, it is necessary to display an image that is in focus over the entire projection surface.

[0004] However, conventional imaging devices are manufactured to focus on a plane perpendicular to the optical axis of the imaging lens, and conventional projection devices are manufactured to focus on a plane perpendicular to the optical axis of the projection lens. Therefore, it is difficult for the above-mentioned imaging devices and projection devices to focus on multiple points on a plane.

[0005] Patent Document 1 discloses a method for focusing on an oblique surface with a depth difference. According to the technology disclosed in Patent Document 1, a reflecting mirror with a special curved surface is disposed between the document surface (imaging surface) and the imaging element.

[0006] Patent Document 2 discloses a method for focusing on an oblique surface with a depth difference. According to the technology disclosed in Patent Document 2, a reflecting mirror with a special curved surface is placed between a spatial light modulator such as a liquid crystal or a DMD (Digital Mirror Device) and the projection surface. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2018-174362 A [Patent Document 2] JP 2008-225455 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in a system used for object recognition such as face recognition and iris recognition as shown in A of Fig. 1, the imaging device 1 may be located at an angle to the person to be photographed 2. As a result, the image is focused on a position different from the face of the person to be photographed 2, which is parallel to the imaging plane 4, that is, on the focusing plane 3 (dashed line) that perpendicularly intersects with the optical axis 5 (dashed line). In this case, an image focused on only a part of the face of the person to be photographed 2 can be obtained, making it difficult to perform face recognition and iris recognition with high accuracy.

[0009] Furthermore, in the technology disclosed in Patent Document 1, the reflecting mirror having a special curved surface is generally a free-form mirror, which requires high manufacturing costs, and therefore the optical system becomes expensive.

[0010] Furthermore, it is difficult to manufacture a reflector that generates multiple focal planes 3 that are focused on the faces of subjects 2a and 2b in different directions as shown in Fig. 1B, and the degree of freedom in design is low. Also, the above-mentioned reflector has a size equivalent to the angle of view of the image, so the optical system becomes large.

[0011] Next, in a system used for projection as shown in A of Fig. 2, the projection device 6 is located in a diagonal direction relative to the projection surface 7. Therefore, the image is focused on a focal plane 9 (dashed line) that perpendicularly intersects with the optical axis 8 (dashed line). In other words, the image is focused on a position different from the projection surface 7.

[0012] Furthermore, in the technology disclosed in Patent Document 2, the reflecting mirror having a special curved surface generally uses a free-form mirror, which is very costly to manufacture, and therefore the optical system becomes expensive.

[0013] Furthermore, when focusing on projection surface 7 where the change in depth is discontinuous as in B of Fig. 2, it is difficult to manufacture a reflecting mirror, and there is little freedom in design. Also, the reflecting mirror has a size equivalent to the projection angle of view, so the optical system becomes large.

[0014] One aspect of the present invention is to provide an optical system that is capable of multiple focusing and is small and inexpensive, and an imaging device and a projection device that use the optical system. [Means for solving the problem]

[0015] In order to achieve the above object, an optical system according to one aspect comprises: An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. It is characterized by:

[0016] In order to achieve the above object, an imaging device according to one aspect comprises: An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. It is characterized by:

[0017] In order to achieve the above object, an optical system according to one aspect comprises: A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. It is characterized by:

[0018] In order to achieve the above object, a projection device according to one aspect comprises: A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. It is characterized by: Effect of the Invention

[0019] On the one hand, it can provide multiple focal points and, furthermore, it can be made small and inexpensive. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram for explaining a conventional imaging device. [Diagram 2] FIG. 2 is a diagram for explaining a conventional projection device. [Diagram 3] FIG. 3 is a diagram for explaining an example of the optical system of the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining an example of a prism according to the first embodiment. [Diagram 5] FIG. 5 is a diagram for explaining a method for designing a prism. [Figure 6] FIG. 6 is a diagram showing the relationship between the position of the focal plane and the object distance. [Figure 7] FIG. 7 is a diagram showing the relationship between the position of an image plane that is in an image-forming relationship with the focal plane and the image distance. [Figure 8] FIG. 8 is a diagram for explaining a method of designing the prism of the first embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of a system including the imaging device of the first embodiment. [Figure 10] FIG. 10 is a diagram for explaining face authentication and iris authentication. [Figure 11] FIG. 11 is a diagram for explaining face authentication and iris authentication. [Figure 12] FIG. 12 is a diagram for explaining another example of a prism according to the first embodiment. In FIG. [Figure 13] FIG. 13 is a diagram illustrating an example of a system including the imaging device of the second embodiment. [Figure 14] FIG. 14 is a diagram for explaining the optical system of the second embodiment. [Figure 15] FIG. 15 is a diagram for explaining the optical system of the second embodiment. [Figure 16] FIG. 16 is a diagram illustrating an example of a system including the imaging device of the third embodiment. [Figure 17] FIG. 17 is a diagram for explaining the optical system of the third embodiment. [Figure 18] FIG. 18 is a diagram for explaining an example of the structure of a hollow rotating shaft. [Figure 19] FIG. 19 is a diagram for explaining the focusing plane in the third embodiment. [Figure 20] FIG. 20 is a diagram illustrating an example of an optical system included in a projection device. [Figure 21] FIG. 21 is a diagram for explaining another example of a prism according to the fourth embodiment. In FIG. [Figure 22] FIG. 22 is a diagram for explaining another example of a prism according to the fourth embodiment. In FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings described below, elements having the same or corresponding functions are denoted by the same reference numerals, and repeated description thereof may be omitted.

[0022] (Embodiment 1) The configuration of the optical system 10 in the first embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram for explaining an example of the optical system in the first embodiment.

[0023] [Device configuration] The optical system 10 shown in Fig. 3 has a structure capable of performing multiple focusing operations. As shown in Fig. 3, the optical system 10 includes an image sensor 11, a lens 12, and a prism 13.

[0024] The imaging element 11 is a device that converts light incident through the lens 12 into an electrical signal. The imaging element 11 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, an InGaAs (Indium gallium arsenide) sensor, etc. However, the imaging element 11 is not limited to the above-mentioned image sensors.

[0025] The resolution of the image sensor 11 may be a CMOS sensor with 1920 pixels horizontally × 1080 pixels vertically, a pixel pitch of 5 μm, and a frame rate of 60 fps. However, the resolution, pixel pitch, and frame rate are not limited to those described above.

[0026] The lens 12 is an optical element that refracts and focuses light, and is a transparent body with spherical surfaces on both sides. The lens 12 may be, for example, a convex lens.

[0027] The prism 13 is an optical element for dispersing, refracting, totally reflecting, and birefringing light, and is a polyhedron made of a transparent medium. Specifically, the prism 13 is disposed between the image sensor 11 and the lens 12 in the optical path as shown in FIG.

[0028] The material of the prism 13 is, for example, glass, plastic, etc. However, the material of the prism 13 is not limited to glass or plastic, and may be any transparent material that has the same effect as glass or plastic.

[0029] In the example of Fig. 3, a virtual image 15 of the light receiving surface 14 of the image sensor 11 is formed inside the prism 13. Also, the focal plane 16 in Fig. 3 is located at a position conjugate to the virtual image 15 and the lens 12 in the optical system 10. That is, the focal plane 16 and the virtual image 15 are in an imaging relationship (conjugate relationship).

[0030] Since it is necessary to focus the subject on the focal plane 16, the shape of the prism 13 is set so that a virtual image 15 of the light receiving surface 14 of the image sensor 11 can be formed in the prism 13 that has an imaging relationship (conjugate relationship) with the focal plane 16. In other words, a conjugate image distance distribution that has an imaging relationship with the focal plane 16 (predetermined object distance distribution) is obtained, and the shape of the prism 13, which is a transmissive optical member, is set so that this image distance distribution and the virtual image 15 on the light receiving surface 14 coincide with each other.

[0031] Fig. 4 is a diagram for explaining an example of the prism of the embodiment 1. In A of Fig. 4, a focal plane (not shown) is parallel to the light receiving surface 14. Therefore, the virtual image 15a of the light receiving surface 14 is generated parallel to the light receiving surface 14. As a result, the shape of the prism 13a is a rectangular parallelepiped.

[0032] Furthermore, in the case of a shape like prism 13a in FIG. 4A, the position where virtual image 15a is generated can be expressed using thickness t1 and refractive index n of prism 13a.

[0033] Specifically, the position of virtual image 15a can be expressed by distance d1 as shown in Equation 1. That is, distance d1 is the distance from the surface of prism 13a on the light receiving surface 14 side of imaging element 11 to virtual image 15a in the Z direction (the same direction as the optical axis).

[0034]

number

[0035] Next, in Fig. 4B, a focal plane (not shown), like the focal plane 16 in Fig. 3, is oblique to the light receiving surface 14. Therefore, a virtual image 15b of the light receiving surface 14 is generated obliquely to the light receiving surface 14. For this reason, the shape of the prism 13b in Fig. 4B is a wedge shape. A wedge shape is a shape that is wide at one end and gradually narrows toward the other end.

[0036] For example, when prism 13b has a shape as shown in Fig. 4B, the position where virtual image 15b is generated can be expressed by using thickness t2 and refractive index n of prism 13b. Thickness t2 is the distance upward in the Z direction from the surface of prism 13b on the light receiving surface 14 side.

[0037] Specifically, the position of virtual image 15b can be expressed by distance d1 (=d2) as shown in equation 1. However, in the case of B in Fig. 4, distance d2 is the distance in the Z direction from the surface of prism 13b on the light receiving surface 14 side, and equation 1 shows that the surface of virtual image 15b exists at a position that maintains the ratio of thickness t2 of prism 13b to distance d2.

[0038] A method for designing a prism will now be described. Fig. 5 is a diagram for explaining a method of designing a prism. Fig. 5 is a side view showing the relationship between the optical system 10 and the subject 31. In the example of Fig. 5, the focal plane 16 is parallel to the face of the subject (person to be photographed) 31. The length of the focal plane 16 (from point P1 to point P2) is set to 200 [mm]. The object distance from point P0 of the optical system 10 to point P1 of the focal plane 16 is set to 1800 [mm], and the object distance from point P0 of the optical system 10 to point P2 of the focal plane 16 is set to 1500 [mm].

[0039] Fig. 6 is a diagram showing the relationship between the position of the focal plane and the object distance. Fig. 6 is a graph showing the relationship between the position of the focal plane 16 in Fig. 5 and the focal distance P0-P1 (from point P0 to point P1) and the object distance P0-P2 (from point P0 to point P2).

[0040] Fig. 7 is a diagram showing the relationship between the position of the image plane in an image-forming relationship with the focal plane and the image distance. Fig. 7 is a graph showing the relationship between the position of the image plane in an image-forming relationship with the focal plane 16 in Fig. 5 and the image distance when the focal length of the lens is 75 [mm].

[0041] The imaging relationship can be expressed by equation 2 using object distance s, image distance s', and lens focal length f.

[0042]

number

[0043] Fig. 8 is a diagram for explaining a method for designing a prism according to the first embodiment. In order to form a virtual image 15 of the image sensor 11 in the prism 13 of the optical system 10 shown in Fig. 8 at the position of the image distance in the graph shown in Fig. 7, the focal length f of the lens 12 should be set to 75 [mm], the refractive index n of the prism 13 should be set to 1.5, and the apex angle Ang of the prism 13 should be set to 10 [°]. In this way, the prism 13 can be designed.

[0044] In this example, since the thickness t2 of the prism is three times the distance d2 from equation 1, the apex angle Ang can be calculated as 10[°] from the inverse function of three times the slope (tangent) of the image distance in the graph shown in Figure 7. Generalizing this, the apex angle Ang can be calculated from equation 3, where yi is the position of the image plane in the Y direction.

[0045]

number

[0046] We will explain face recognition and iris recognition. Fig. 9 is a diagram for explaining an example of a system including the imaging device of embodiment 1. The system shown in Fig. 9 is a device used for object recognition such as face recognition and iris recognition. The system shown in Fig. 9 includes an imaging device 100, an information processing device 200, and a network 300.

[0047] The imaging device 100 includes the above-described optical system 10 and a control unit 20. The imaging device 100 is, for example, a camera.

[0048] The control unit 20 acquires imaging data (or imaging signals) output from the imaging element 11 provided in the optical system 10, and transmits the acquired imaging data to the information processing device 200 via the network 300. The control unit 20 is, for example, a central processing unit (CPU), a programmable device such as a field-programmable gate array (FPGA), a graphics processing unit (GPU), or a circuit equipped with any one or more of them.

[0049] The information processing device 200 executes face recognition processing, iris recognition processing, or both processing, based on the received imaging data. The information processing device 200 may execute object recognition processing other than face recognition processing and iris recognition processing. The information processing device 200 is, for example, a CPU, a programmable device such as an FPGA, a GPU, or a circuit equipped with any one or more of them, a server computer, a personal computer, a mobile terminal, or the like.

[0050] In the example of FIG. 9, the information processing device 200 is configured to execute face authentication processing, iris authentication processing, or both of the processing, but the control unit 20 may execute the above-mentioned processing.

[0051] Network 300 is a general network constructed using communication lines such as the Internet, a LAN (Local Area Network), a dedicated line, a telephone line, an in-house network, a mobile communication network, Bluetooth (registered trademark), or WiFi (Wireless Fidelity).

[0052] 10 and 11 are diagrams for explaining face authentication and iris authentication. As described above, in a conventional imaging device, when the face of a person to be photographed is at an angle to the imaging plane, for example, as shown in A of Fig. 10, the right eye part of the face (solid line) can be focused, but the left eye part (dashed line) cannot be focused. Therefore, it is not possible to perform face authentication and iris authentication with high accuracy.

[0053] However, if an imaging device having the optical system 10 of the first embodiment is used, it is possible to focus on the right eye portion and the left eye portion as shown in FIG. 10B, so that face authentication and iris authentication can be performed with high accuracy.

[0054] Furthermore, in the conventional imaging device described above, when there are multiple subjects, for example, of the two faces shown in A of FIG. 11, only the right face (solid line) is focused on, but the left face (dashed line) cannot be focused on.

[0055] However, in an imaging device having the optical system 10 of embodiment 1, it is possible to focus on the faces of two subjects as shown in B of FIG. 11, and therefore it is possible to perform face authentication and iris authentication with high accuracy for each face of the subject.

[0056] Other prisms will now be described. Fig. 12 is a diagram for explaining another example of a prism according to the embodiment 1. Fig. 12A, B, and C show an optical system having a plurality of focusing surfaces and a focusing surface having a curved shape.

[0057] The optical system of A in Fig. 12 has two focusing surfaces 16a and 16b. That is, the prism 13c as shown in A in Fig. 12 focuses on the subject at the focusing surfaces 16a and 16b (L-shaped focusing surfaces) that are oblique to the light receiving surface 14. For this reason, the shape of the prism 13c in A in Fig. 12 is designed so that a virtual image 15c of the light receiving surface 14 of the image sensor 11 as shown in A in Fig. 12 can be formed in a L-shape in the prism 13c that is in an imaging relationship with the L-shaped focusing surfaces 16a and 16b.

[0058] The optical system of B in Fig. 12 has a plurality of discontinuous focal planes 16c, 16d, and 16e. That is, the prism 13d shown in B in Fig. 12 focuses on the subject at the focal plane 16c parallel to the light receiving surface 14, the focal plane 16d having a different depth from the focal plane 16c, and the focal plane 16e oblique to the light receiving surface 14. For this reason, the shape of the prism 13d in B in Fig. 12 is designed so that a virtual image 15d of the light receiving surface 14 of the image sensor 11 as shown in B in Fig. 12 can be formed in the prism 13d that is in an image-forming relationship with the focal planes 16c, 16d, and 16e.

[0059] The optical system of Fig. 12C has multiple focal planes 16f, 16g. That is, the prism 13e shown in Fig. 12C focuses on the subject at the focal plane 16f parallel to the light receiving surface 14 and the curved focal plane 16g. Therefore, the shape of the prism 13e in Fig. 12C is designed so that a virtual image 15e of the light receiving surface 14 of the image sensor 11 as shown in Fig. 12C can be formed in the prism 13e that is in an imaging relationship with the focal planes 16f, 16g.

[0060] [Effects of the First Embodiment] As described above, according to the first embodiment, a prism capable of forming a virtual image 15 of the light receiving surface 14 of the image sensor 11 is used in the prism 13 that is in an image-forming relationship with the focal plane, so that the optical system can be made compact.

[0061] Moreover, the shape of the prism 13 only needs to be a shape that creates a virtual image on the surface that is in an imaging relationship with the focal plane 16, and therefore can be designed using only the above-mentioned formulas 1 and 2. This simplifies the design and further reduces costs.

[0062] In addition, since the optical system can be made compact, the imaging device used for object recognition such as face recognition, iris recognition, etc. can be made compact. The present invention may be applied to imaging devices used for purposes other than object recognition such as face recognition, iris recognition, etc. Furthermore, a plurality of prisms with different shapes for each purpose may be prepared in advance, and the prisms may be replaced depending on the positional relationship between the optical system and the subject.

[0063] In addition, since the optical system can be made compact, the projection device that projects and displays an image on the projection surface can also be made compact. Furthermore, a plurality of prisms with different shapes for different applications may be prepared in advance, and the prisms may be replaced depending on the positional relationship between the optical system and the projection surface.

[0064] (Embodiment 2) The second embodiment will be described with reference to Fig. 13. The difference between the first and second embodiments is a prism. Fig. 13 is a diagram for explaining an example of a system having the imaging device of the second embodiment.

[0065] [Device configuration] 13 includes an imaging device 100a, an information processing device 200, and a network 300. Note that the information processing device 200 and the network 300 have been described in the first embodiment, and therefore description thereof will be omitted.

[0066] The imaging device 100a includes an optical system 101 and a control unit 102. The imaging device 100a is, for example, a camera.

[0067] The optical system 101 has the same configuration as that of the first embodiment, but the shape of the prism portion of the optical system 101 of the second embodiment can be changed. The details of the optical system 101 will be described later.

[0068] The control unit 102 has the same configuration as in the first embodiment. However, the control unit 102 in the second embodiment further performs control for changing the shape of the prism. The control unit 102 will be described in detail later.

[0069] The optical system of the second embodiment will be described. 14 is a diagram for explaining the optical system of embodiment 2. The optical system 101 has an image sensor 11, a lens 12, and a prism portion 402. Note that the image sensor 11 and the lens 12 have been explained in embodiment 1, and therefore explanation thereof will be omitted.

[0070] Prism portion 402 has flat plate portion 403a, flat plate portion 403b, expandable portion 404, actuator 405a, and actuator 405b. Prism portion 402 can change the position of the focusing plane by changing the shape.

[0071] The flat plate portion 403a is provided and fixed on the imaging element 11 side (side opposite to the Z direction) of the expandable portion 404 in parallel to the light receiving surface 14. In addition, the surface of the flat plate portion 403a on the lens 12 side (Z direction side) is bonded to the imaging element 11 side (side opposite to the Z direction) of the expandable portion 404.

[0072] The flat plate portion 403b is provided on the lens 12 side (Z direction side) of the expandable portion 404. In addition, a surface of the flat plate portion 403b on the imaging element 11 side (side opposite to the Z direction) is bonded to the lens 12 side (Z direction side) of the expandable portion 404.

[0073] The material of the flat plate portions 403a and 403b is, for example, glass, plastic, etc. However, the material of the flat plate portions 403a and 403b is not limited to glass and plastic, and may be various transparent materials having the same effect as glass and plastic.

[0074] The stretchable portion 404 is provided between the flat plate portion 403a and the flat plate portion 403b, and is bonded to the flat plate portion 403a and the flat plate portion 403b at a predetermined position. The stretchable portion 404 is a stretchable bag-shaped transparent medium (stretchable material) filled with liquid.

[0075] The elastic material is, for example, silicone rubber, etc. However, the elastic material is not limited to silicone rubber, and any elastic material having the same effect as silicone rubber, etc. may be used.

[0076] The liquid is, for example, water, oil, etc. However, the liquid is not limited to water and oil, and may be any liquid that has a similar effect to water and oil.

[0077] Further, the stretchable portion 404 has a refractive index. The refractive indexes of the flat plate portion 403a, the flat plate portion 403b, and the stretchable portion 404 may be the same or may be different from each other.

[0078] The actuator 405a is provided at one end (predetermined position) of the flat plate portion 403b on the lens 12 side (Z direction side). The actuator 405a is driven under the control of the control unit 102 to move the one end of the flat plate portion 403b on the lens 12 side (Z direction side) in the Z direction or in the direction opposite to the Z direction. However, the position of the actuator 405a is not limited to the position shown in FIG.

[0079] The actuator 405b is provided at the other end (predetermined position) of the flat plate portion 403b on the lens 12 side (Z direction side). The actuator 405b is driven under the control of the control unit 102 to move the other end of the flat plate portion 403b on the lens 12 side (Z direction side) in the Z direction or in the direction opposite to the Z direction. However, the position of the actuator 405b is not limited to the position shown in FIG.

[0080] In the second embodiment, the actuators 405a and 405b are controlled to tilt the flat plate portion 403b, thereby deforming the shape of the expandable portion 404. For example, the expandable portion 404 is deformed into a shape as shown in Fig. 15. Fig. 15 is a diagram for explaining the optical system of the second embodiment.

[0081] In the example of FIG. 15, the other end of the flat plate portion 403b is pushed in the direction opposite to the Z direction by using the actuator 405b, thereby tilting the flat plate portion 403b, and the shape of the expandable portion 404 is changed into a wedge shape.

[0082] Specifically, the control unit 102 controls the actuators 405a and 405b to tilt the surface of the flat plate portion 403b based on a preset condition. In the example of Fig. 15, the condition is a condition that the angle between the flat plate portion 403a and the flat plate portion 403b becomes a preset apex angle Ang.

[0083] Also, the expandable portion 404 may be deformed according to the installation conditions of the imaging device 100a. Furthermore, the focus state of the subject may be detected by image processing, and the expandable portion 404 may be dynamically deformed according to the detected state.

[0084] In the second embodiment, the actuators 405a and 405b are controlled to change the shape of the expandable portion 404. However, the flat plate portions 403a and 403b may be moved manually using screws or the like instead of the actuators 405a and 405b.

[0085] [Effects of the second embodiment] As described above, according to the second embodiment, the effects of the first embodiment can be obtained, and further, the expandable portion 404 can be automatically deformed.

[0086] (Embodiment 3) The third embodiment will be described with reference to Fig. 16. The difference between the first and third embodiments is a prism. Fig. 16 is a diagram for explaining an example of a system having the imaging device of the third embodiment.

[0087] [Device configuration] 16 includes an imaging device 100b, an information processing device 200, and a network 300. Note that the information processing device 200 and the network 300 have been described in the first embodiment, and therefore description thereof will be omitted.

[0088] The imaging device 100b includes an optical system 111 and a control unit 112. The imaging device 100b is, for example, a camera.

[0089] The optical system 111 has the same configuration as in the first embodiment, but the position of the focal plane can be changed by rotating a prism included in the optical system 111 in the third embodiment. The optical system 111 will be described in detail later.

[0090] The control unit 112 has the same configuration as in the embodiment 1. However, the control unit 112 in the embodiment 3 further performs control for rotating the prism. The control unit 112 will be described in detail later.

[0091] The optical system of the third embodiment will be described. 17 is a diagram for explaining the optical system of embodiment 3. The optical system 111 has an image sensor 11, a lens 12, and a prism portion 502. Note that the image sensor 11 and the lens 12 have been explained in embodiment 1, and therefore explanation thereof will be omitted.

[0092] The prism unit 502 has a hollow shaft motor 503 and a prism 13f. The prism unit 502 can change the position of the focal plane by rotating the prism 13f using the hollow shaft motor 503.

[0093] Under the control of the control unit 112, the hollow shaft motor 503 rotates a cylindrical rotating hollow shaft 504 about the rotation axis of the rotating hollow shaft 504, thereby rotating the prism 13f.

[0094] A prism 13f is attached to the hollow interior of the rotating hollow shaft 504 as shown in Fig. 18. Fig. 18 is a diagram for explaining an example of the structure of the rotating hollow shaft.

[0095] For example, by setting the rotation speed of the rotating hollow shaft 504 to 60 rotations per second (3600 rpm) and the frame rate of the image sensor 11 to 600 fps, it is possible to capture 10 images of different in-focus planes every 1 / 60 seconds.

[0096] 17 and 18 may coincide with the optical axis of the lens 12, or may be different from the optical axis of the lens 12. In FIG.

[0097] Fig. 19 is a diagram for explaining the focal plane in embodiment 3. As shown in Fig. 19, the focal plane moves (changes) over time in response to the rotation of prism 13f. Focus plane 16h shown in Fig. 19A moves to focal plane 16i shown in Fig. 19B after a predetermined time has elapsed.

[0098] [Effects of the third embodiment] As described above, according to the third embodiment, the effects of the first embodiment can be obtained, and further, multiple focusing can be performed automatically.

[0099] In fact, when face recognition and iris recognition were performed using an imaging device having the optical system 111 of the third embodiment, the face of each person to be photographed and either an image focused on the left eye or the right eye of each person to be photographed were included in the 10 images. In other words, since images focused on the left eye or the right eye of each person to be photographed could be obtained, face recognition and iris recognition could be performed with high accuracy.

[0100] In the third embodiment, the prism 13f may be rotated or translated depending on the installation conditions of the imaging device 100b. Also, the focus state of the subject may be detected by image processing, and the prism 13f may be dynamically rotated or translated depending on the detected state. Furthermore, the prism 13f may be translated or reciprocated in addition to rotating.

[0101] (Embodiment 4) The fourth embodiment will be described with reference to Fig. 20. Fig. 20 is a diagram for explaining an example of an optical system included in a projection device.

[0102] [Device configuration] The optical system 600 shown in Fig. 20 has a structure capable of performing multiple focusing. As shown in Fig. 20, the optical system 600 also includes a display element 601, a lens 12, and a prism 13g.

[0103] The display element 601 is a device that displays an image. The display element 601 is, for example, a liquid crystal panel, a DMD, or any of various spatial light modulators. However, the display element 601 is not limited to the liquid crystal panel and DMD described above.

[0104] It is possible to use a liquid crystal panel with a resolution of 1920 pixels horizontally × 1080 pixels vertically, a pixel pitch of 10 [μm], and a frame rate of 60 [fps] as the resolution of the display element 601. However, the resolution, pixel pitch, and frame rate are not limited to those described above.

[0105] It should be noted that the lens 12 and the prism 13g have been described in the first embodiment, and therefore detailed description thereof will be omitted.

[0106] 20, prism 13g is disposed between the optical path of display element 601 and lens 12. A virtual image 602 of the surface of display element 601 is formed inside prism 13g. Projected surface 603 is located in a position conjugate with virtual image 602 via lens 12 in optical system 600. That is, projection surface 603 and virtual image 602 are in an imaging relationship.

[0107] The shape of the prism 13 g is such that in order to focus the projection object on the projection surface 603 , a virtual image 602 of the surface of the display element 601 is formed in the prism 13 g that is in an imaging relationship with the projection surface 603 .

[0108] Other prisms will now be described. 21 and 22 are diagrams for explaining other examples of prisms in embodiment 4. When a projection surface 603a is located obliquely with respect to an optical system 600a provided in a projection device as shown in A of Fig. 21, a wedge-shaped prism 13h as shown in A of Fig. 22 is used.

[0109] That is, prism 13h as shown in A of Fig. 22 focuses display element 601, which is a projection object, on projection surface 603a. Therefore, the shape of prism 13h in A of Fig. 22 is designed so that a virtual image 602a of display element 601 as shown in A of Fig. 22 can be formed in prism 13h that is in an imaging relationship with projection surface 603a.

[0110] As shown in FIG. 21B, the projection surface onto which optical system 600b provided in the projection device projects is discontinuous projection surfaces 603b, 603c, and 603d with different depths, so a prism 13i having a discontinuous surface as shown in FIG. 22B is used.

[0111] That is, prism 13i as shown in B of Fig. 22 focuses display element 601, which is a projection object, on projection surfaces 603b, 603c, and 603d. Therefore, the shape of prism 13i in B of Fig. 22 is designed so that a virtual image 602b of display element 601 as shown in B of Fig. 22 can be formed in prism 13i, which is in an imaging relationship with projection surfaces 603b, 603c, and 603d.

[0112] As shown in FIG. 21C, the projection surface onto which optical system 600c provided in the projection device projects is made up of curved projection surface 603e and projection surface 603f, so a prism 13j having a curved surface as shown in FIG. 22C is used.

[0113] That is, prism 13j as shown in Fig. 22C focuses display element 601, which is a projection object, on projection surfaces 603e and 603f. Therefore, the shape of prism 13j in Fig. 22C is designed so that virtual image 602c of display element 601 as shown in Fig. 22C can be formed in prism 13j that is in an imaging relationship with projection surfaces 603e and 603f.

[0114] In addition, when the projection device according to embodiment 4 was used to project images onto a range of projection surfaces, including oblique projection surfaces, discontinuous projection surfaces, and curved surfaces, a corresponding prism 13 was placed on the display surface of the display element, and a sharp, focused image could be observed on any projection surface.

[0115] When three display elements, one for red, one for green and one for blue, are used, a prism corresponding to each liquid crystal panel is disposed.

[0116] Furthermore, the optical system 600 of the fourth embodiment may employ the optical systems described in the second and third embodiments.

[0117] [Effects of the fourth embodiment] As described above, according to the fourth embodiment, a prism capable of forming a virtual image 602 of the display element 601 is used in the prism 13 that is in an image-forming relationship with the projection surface, so that the optical system can be made compact.

[0118] Moreover, the shape of prism 13 only needs to be a shape that creates a virtual image on the surface that has an imaging relationship with projection surface 603, and therefore can be designed using only the above-mentioned formulas 1 and 2. Therefore, the design is simple and the cost can be further reduced.

[0119] In addition, since the optical system can be made compact, the projection device that projects and displays an image on the projection surface can also be made compact. Furthermore, a plurality of prisms with different shapes for different applications may be prepared in advance, and the prisms may be replaced depending on the positional relationship between the optical system and the projection surface.

[0120] [Note] The following supplementary notes are further disclosed regarding the above-described embodiments. A part or all of the above-described embodiments can be expressed by (Supplementary Note 1) to (Supplementary Note 12) described below, but are not limited to the following descriptions.

[0121] (Appendix 1) An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. optical system.

[0122] (Appendix 2) 2. The optical system according to claim 1, The prism is A transparent first flat plate portion fixed to the imaging element side; A transparent second flat plate portion disposed on the lens side; An expandable portion is disposed between the first flat plate portion and the second flat plate portion, and a liquid is filled in a transparent medium in the shape of a bag that expands and contracts; An actuator that tilts the second flat plate portion to change the shape of the expandable portion; An optical system having

[0123] (Appendix 3) 2. The optical system according to claim 1, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. optical system.

[0124] (Appendix 4) An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. Imaging device.

[0125] (Appendix 5) 5. The imaging device according to claim 4, The prism is A transparent first flat plate portion fixed to the imaging element side; A transparent second flat plate portion disposed on the lens side; An expandable portion is disposed between the first flat plate portion and the second flat plate portion, and a liquid is filled in a transparent medium in the shape of a bag that expands and contracts; An actuator that tilts the second flat plate portion to change the shape of the expandable portion; An imaging device having the above configuration.

[0126] (Appendix 6) 5. The imaging device according to claim 4, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. Imaging device.

[0127] (Appendix 7) A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. optical system.

[0128] (Appendix 8) 8. The optical system according to claim 7, The prism is A transparent first flat plate portion fixed to the display element side; A transparent second flat plate portion disposed on the lens side; An expandable portion is disposed between the first flat plate portion and the second flat plate portion, and a liquid is filled in a transparent medium in the shape of a bag that expands and contracts; An actuator that tilts the second flat plate portion to change the shape of the expandable portion; An optical system having

[0129] (Appendix 9) 8. The optical system according to claim 7, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. optical system.

[0130] (Appendix 10) A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. Projection device.

[0131] (Appendix 11) 11. The projection device of claim 10, The prism is A transparent first flat plate portion fixed to the display element side; A transparent second flat plate portion disposed on the lens side; An expandable portion is disposed between the first flat plate portion and the second flat plate portion, and a liquid is filled in a transparent medium in the shape of a bag that expands and contracts; An actuator that tilts the second flat plate portion to change the shape of the expandable portion; A projection device having the above structure.

[0132] (Appendix 12) 11. The projection device of claim 10, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. Projection device.

[0133] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. [Industrial Applicability]

[0134] As described above, the present invention provides a small, inexpensive optical system capable of multiple focusing, and an imaging device and a projection device using the optical system. The present invention is useful in fields requiring object recognition such as face recognition and iris recognition, and image projection. [Explanation of symbols]

[0135] 10, 101, 111, 600 optical system 11 Image sensor 12 Lenses 13 Prism 14 Photosensitive surface 15, 602 Virtual Image 16 Focus plane 20, 102, 112 Control unit 100 Imaging device 200 Information processing device 300 Network 402, 502 Prism part 403 Flat plate part 404 Telescopic part 405 Actuator 503 Hollow shaft motor 504 Rotating hollow shaft 601 Display element 603 Projection surface

Claims

1. An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. optical system.

2. 2. The optical system according to claim 1, The prism is A transparent first flat plate portion fixed to the imaging element side; A transparent second flat plate portion disposed on the lens side; an expandable portion, the expandable portion being disposed between the first flat plate portion and the second flat plate portion, and including a transparent medium in the form of a bag that expands and contracts and is filled with a liquid; an actuator that tilts the second flat plate portion to change the shape of the expandable portion; An optical system having

3. 2. The optical system according to claim 1, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. optical system.

4. An image sensor that converts light into an electrical signal; A lens that refracts and focuses light, a prism disposed between the image sensor and the lens in an optical path; A virtual image of the light receiving surface of the image sensor is formed in the prism, and a focal plane is located at a position conjugate with the virtual image via the lens. Imaging device.

5. 5. The imaging device according to claim 4, The prism is A transparent first flat plate portion fixed to the imaging element side; A transparent second flat plate portion disposed on the lens side; an expandable portion, the expandable portion being disposed between the first flat plate portion and the second flat plate portion, and including a transparent medium in the form of a bag that expands and contracts and is filled with a liquid; an actuator that tilts the second flat plate portion to change the shape of the expandable portion; An imaging device having the above configuration.

6. 5. The imaging device according to claim 4, A hollow shaft motor is provided to rotate a cylindrical rotating hollow shaft. The hollow shaft motor rotates the prism inside the rotating hollow shaft. Imaging device.

7. A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. optical system.

8. A display element for displaying an image; A lens that refracts and focuses light, a prism disposed between the display element and the lens in an optical path; A virtual image of the surface of the display element is formed in the prism, and a projection surface is located in a position conjugate with the virtual image via the lens. Projection device.

Images