Imaging device, optical member, and measuring system

Abstract

An imaging device is provided with: a first optical element that splits a light beam from a subject into a first light beam and a second light beam having optical characteristics different from those of the first light beam; an imaging optical system into which the first light beam and the second light beam are incident at mutually different angles, and which forms a first image by imaging the first light beam and forms a second image by imaging the second light beam; and an image sensor having an imaging surface. The first image and the second image are formed at different positions on the imaging surface. The first image and the second image are symmetrically imaged on the imaging surface with a plane intersecting with the imaging surface as a reference.

Description

Technical Field

[0001] The present disclosure relates to an imaging device, an optical component, and a measurement system. Background Art

[0002] Acquiring two images of a subject with different optical properties is useful for evaluating the subject. For example, acquiring two images of a subject with wavelengths contained in different wavelength ranges is useful in two-color thermography for estimating the subject's temperature. The principle of two-color thermography is as follows: the intensity of thermal radiation from an object depends on the object's temperature and emissivity. Therefore, if only the intensity of thermal radiation from an object is measured without knowing the emissivity, the object's temperature cannot be determined. However, if the emissivities of two different wavelength ranges are treated as equal, the ratio of the radiation intensities of the two wavelength ranges depends on the temperature, not the emissivity. In this case, the object's temperature can be estimated by measuring the radiation intensities from the same point within the subject in the two wavelength ranges and calculating their intensity ratio.

[0003] Acquiring two images of a subject in different wavelength ranges is also useful for fluorescence imaging. In fluorescence imaging, fluorescence intensity is proportional to both the excitation light intensity and the luminous efficiency. Therefore, by capturing both the fluorescence intensity and the excitation light intensity separately and calculating their intensity ratio, the distribution of luminous efficiency can be visualized.

[0004] Patent Documents 1 and 2 disclose examples of imaging devices that acquire two images in different wavelength ranges from a subject.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-214048

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 55-124379 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The present disclosure provides an imaging device capable of acquiring two images having different optical characteristics suitable for evaluating a subject with a simple configuration.

[0011] Means used to solve problems

[0012] An imaging device according to one embodiment of the present disclosure includes: a first optical element that separates a light beam from a subject into a first light beam and a second light beam, the second light beam having optical characteristics different from those of the first light beam; an imaging optical system that is incident at different angles and images the first light beam to form a first image and the second light beam to form a second image; and an image sensor having an imaging plane. The first image and the second image are formed at different positions on the imaging plane. The first image and the second image are formed symmetrically on the imaging plane with respect to a plane intersecting the imaging plane.

[0013] The generalization or specific scheme of the present disclosure can be implemented in a system, device, method, integrated circuit, computer program or recording medium such as a computer readable recording disk, or in any combination of a system, device, method, integrated circuit, computer program and recording medium. The computer readable recording medium may include, for example, a non-volatile recording medium, such as a CD-ROM (read-only compact disc memory). The device may be composed of more than one device. When the device is composed of more than two devices, the two or more devices may be configured in one device or may be separately configured in two or more separated devices. In this specification and claims, "device" refers not only to one device, but also to a system composed of multiple devices.

[0014] Effects of the Invention

[0015] According to the technology disclosed in the present invention, it is possible to realize an imaging device capable of acquiring two images having different optical characteristics suitable for evaluating a subject with a simple configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram schematically showing the configuration of an imaging device according to the exemplary embodiment 1 of the present disclosure.

[0017] Figure 2 This is a diagram schematically showing how a light beam is reflected by a mirror surface.

[0018] Figure 3 This is a diagram schematically showing the configuration of an imaging device according to the exemplary embodiment 1 of the present disclosure.

[0019] Figure 4 It is a diagram schematically showing an example of a dichroic prism.

[0020] Figure 5 This is a diagram schematically showing an example of the optical path of a light beam in a dichroic prism.

[0021] Figure 6 It is a diagram schematically showing an example of an optical path adjustment element.

[0022] Figure 7 This is a diagram schematically showing an example of the path of a light beam in an optical path adjusting element.

[0023] Figure 8 A diagram schematically showing the path of a light beam within an optical component.

[0024] Figure 9 A diagram for explaining general characteristics of an imaging optical system.

[0025] Figure 10 This is a diagram schematically showing an example of a path of a light beam in an imaging device.

[0026] Figure 11 Schematically illustrates how principal light emitted from a certain point forms an image on an image sensor in the absence of a dichroic prism.

[0027] Figure 12A It is a diagram for explaining the position of the apparent subject in the middle of the first image.

[0028] Figure 12B It is a diagram for explaining the position of the actual subject in the first image.

[0029] Figure 13 It is a diagram for explaining the position of the actual subject in the second image.

[0030] Figure 14 This is a diagram schematically showing how the first light beam travels within the first right-angle prism.

[0031] Figure 15A Schematically illustrates how light from a first light beam emitted from a certain point forms an image on an image sensor.

[0032] Figure 15B is another diagram schematically showing how light from a certain point of the first light beam forms an image on the image sensor.

[0033] Figure 16 It is a diagram schematically showing how the second light beam travels in the second right-angle prism.

[0034] Figure 17A Schematically illustrates how light from a certain point of the second light beam forms an image on an image sensor.

[0035] Figure 17B is another diagram schematically showing how light from a certain point of the second light beam forms an image on the image sensor.

[0036] Figure 18FIG. 1 is a diagram schematically showing a range in which images of the first light beam and the second light beam are formed on the image sensor.

[0037] Figure 19 A diagram for explaining the positional relationship between an apparent subject and an actual subject.

[0038] Figure 20 Schematic diagram of an example of a first image and a second image formed on an image sensor.

[0039] Figure 21 FIG. 1 is a diagram schematically showing how light rays of a first light beam and a second light beam emitted from a certain point form images on an image sensor.

[0040] Figure 22 Schematically shows the positional relationship between an apparent light-blocking body, an actual light-blocking body, and a dichroic prism.

[0041] Figure 23 Schematically illustrates a range in which the optical paths of both the first and second light beams forming images on the image sensor are blocked.

[0042] Figure 24 It is a diagram schematically showing an example of a filter array.

[0043] Figure 25A This is a diagram schematically showing an example of connecting optical components and a lens device.

[0044] Figure 25B This is a diagram schematically showing another example of connecting optical components and lens devices.

[0045] Figure 25C This is a diagram schematically showing another example of connecting optical components and lens devices.

[0046] Figure 26 This is a diagram schematically showing a specific configuration of optical components in Modification 1 of the imaging device according to Embodiment 1.

[0047] Figure 27 This is a diagram schematically showing an optical element group in Modification 1 of the imaging device according to Embodiment 1.

[0048] Figure 28 This is a diagram schematically showing an example of the path of a light beam within the optical element group in Modification 1 of the imaging device of Embodiment 1.

[0049] Figure 29 This is a diagram schematically showing an optical path adjustment element in Modification 1 of the imaging device according to Embodiment 1.

[0050] Figure 30This is a diagram schematically showing an example of the path of a light beam within the optical path adjusting element in Modification 1 of the imaging device of Embodiment 1.

[0051] Figure 31 This is a diagram schematically showing an example of a path of a light beam within an optical component in Modification 1 of the imaging device of Embodiment 1.

[0052] Figure 32 This is a diagram schematically showing an example of the path of a light beam in Modification 1 of the imaging device of Embodiment 1.

[0053] Figure 33 This is a diagram schematically showing a specific configuration of optical components in a second modification of the imaging device according to the first embodiment.

[0054] Figure 34 This is a diagram schematically showing a dichroic prism in Modification 2 of the imaging device according to Embodiment 1.

[0055] Figure 35 This is a diagram schematically showing an example of the path of a light beam within a dichroic prism in Modification 2 of the imaging device of Embodiment 1.

[0056] Figure 36 This is a diagram schematically showing an example of a path of a light beam within an optical component in a second modification of the imaging device according to the first embodiment.

[0057] Figure 37 This is a diagram schematically showing an example of the path of a light beam in Modification 2 of the imaging device according to Embodiment 1.

[0058] Figure 38 This is a diagram schematically showing a specific configuration of an imaging device according to an exemplary embodiment 2 of the present disclosure.

[0059] Figure 39 This is a diagram schematically showing the structure of a first modification of the imaging device according to the second embodiment.

[0060] Figure 40 This is a diagram schematically showing the structure of a second modification of the imaging device according to the second embodiment.

[0061] Figure 41 This is a diagram schematically showing the structure of a third modification of the imaging device according to the second embodiment.

[0062] Figure 42A This is a diagram schematically showing an example of a measurement system including the imaging device according to the first embodiment.

[0063] Figure 42B Schematically shows an example of the spectrum of thermal radiation from a subject.

[0064] Figure 43A This is a diagram schematically showing another example of a measurement system including the imaging device according to the first embodiment.

[0065] Figure 43B It is a diagram schematically showing examples of spectra of excitation light and fluorescence.

[0066] Figure 44A This is a diagram schematically showing another example of a measurement system including the imaging device according to the first embodiment.

[0067] Figure 44B This is a diagram schematically showing an example of the absorption spectrum of water.

[0068] Figure 44C It is a diagram schematically showing an example of the spectrum of illumination light.

[0069] Figure 45 This is a diagram schematically showing Example 1 of a conventional imaging device based on Patent Document 1.

[0070] Figure 46 Schematic diagram of an example of images of the first wavelength range and the second wavelength range formed on the image sensor.

[0071] Figure 47A It is a diagram schematically showing an example of curvature aberration.

[0072] Figure 47B This is a diagram schematically showing another example of curvature aberration.

[0073] Figure 48 This is a diagram schematically showing Example 2 of a conventional imaging device based on Patent Document 2. DETAILED DESCRIPTION

[0074] In the present disclosure, all or part of a circuit, unit, device, component or part, or all or part of a functional block in a block diagram may be implemented by one or more electronic circuits including, for example, a semiconductor device, a semiconductor integrated circuit (IC) or an LSI (large scale integration). An LSI or an IC may be integrated on a single chip or may be constructed by combining multiple chips. For example, functional blocks other than storage elements may be integrated into a single chip. Although referred to here as LSI or IC, the name may vary depending on the degree of integration and may also be referred to as system LSI, VLSI (very large scale integration) or ULSI (ultra large scale integration). For the same purpose, a field programmable gate array (FPGA) that is programmed after manufacturing the LSI, or a reconfigurable logic device that can reconstruct the internal connection relationship of the LSI or can set the circuit partitioning within the LSI can also be used.

[0075] In addition, all or part of the functions or operations of a circuit, unit, device, component or part can be executed by software processing. In this case, the software is recorded on one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, and when the software is executed by a processing device (processor), the functions determined by the software are executed by the processing device (processor) and peripheral devices. The system or device may have one or more non-transitory recording media, a processing device (processor) and required hardware devices, such as interfaces, in which the software is recorded.

[0076] In the present disclosure, “light” refers to electromagnetic waves, which include not only visible light with a wavelength of about 400 nm to 700 nm, but also ultraviolet light with a wavelength of about 10 nm to 400 nm and infrared light with a wavelength of about 700 nm to 1 mm.

[0077] Hereinafter, exemplary embodiments of the present disclosure will be described. In addition, the embodiments described below all represent general or specific examples. The numerical values, shapes, constituent elements, configuration positions and connection methods of constituent elements, steps, the order of steps, etc. shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, among the constituent elements in the following embodiments, the constituent elements that are not recorded in the independent technical solutions representing the highest concepts are described as arbitrary constituent elements. In addition, each figure is a schematic diagram and is not necessarily a strict diagram. In addition, in each figure, the same figure mark is attached to substantially the same constituent elements, and repeated descriptions are sometimes omitted or simplified.

[0078] Before describing the embodiments of the present disclosure, the underlying findings of the present disclosure will be described. Hereinafter, Examples 1 and 2 of conventional imaging devices are described for acquiring two images of a subject in different wavelength ranges. These two images in different wavelength ranges are examples of two images having different optical characteristics.

[0079] [Example 1 of Conventional Image Capture Device]

[0080] Figure 45 FIG. 1 is a diagram schematically showing Example 1 of a conventional imaging device according to Patent Document 1. Figure 45 In the illustrated imaging device 90A, a light beam from a subject 91 is split into two light beams by a half-mirror 92a. One light beam is reflected by a reflective mirror 92b and passes through a bandpass filter 93a, which selectively transmits light having wavelengths within a first wavelength range. The other light beam is reflected by a reflective mirror 92c and passes through a bandpass filter 93b, which selectively transmits light having wavelengths within a second wavelength range. Figure 45 The dashed arrow shown represents a light beam having a wavelength included in the first wavelength range, Figure 45 The dotted arrows shown represent light beams having wavelengths included in the second wavelength range. The half mirror 92d causes these two light beams to enter the imaging optical system 94. The imaging optical system 94 forms an image of the light beams having wavelengths included in the first wavelength range or the second wavelength range on the image sensor 95.

[0081] The half mirror 92a and the half mirror 92d are arranged at a 45° angle relative to the optical axis of the imaging optical system 94. In contrast, the reflecting mirrors 92b and 92c are arranged so that images formed by imaging the two light beams in the first wavelength range and the second wavelength range are formed at different positions on the imaging surface of the image sensor 95. When the images in the first wavelength range and the second wavelength range do not overlap, the intensity of each image can be easily determined.

[0082] Figure 46 Schematic diagram showing examples of images of the first wavelength range and the second wavelength range formed on the image sensor 95. Figure 45 The illustrated subject 91 has a portion that emits light against a background that emits little light. The portion that emits light has a shape of the letter F and emits light having a wavelength included in the first wavelength range or the second wavelength range.

[0083] In addition, the image formed by the imaging optical system 94 is rotated 180 degrees with the subject. However, in order to make it easier to understand the relationship with the subject, Figure 46 The image is shown rotated so as to face the same direction as the subject.

[0084] like Figure 46 As shown, the range of the image formed on the image sensor 95 by the imaging optical system 94 is a circular range called an image circle 95-1. The image circle 95-1 is set to be wider than the imaging range 95-2 of the image sensor 95. By forming a first image 91a of the first wavelength range and a second image 91b of the second wavelength range within the imaging range 95-2, the radiation intensities of the first wavelength range and the second wavelength range can be measured simultaneously.

[0085] like Figure 46 As shown, point 91b1 in the second image 91b corresponds to point 91a1 in the first image 91a. Similarly, point 91b2 in the second image 91b corresponds to point 91a2 in the first image 91a. Point 91b3 in the second image 91b corresponds to point 91a3 in the first image 91a. Point 91b4 in the second image 91b corresponds to point 91a4 in the first image 91a.

[0086] like Figure 46 As shown, the first image 91a and the second image 91b formed on the image sensor 95 have the same direction. This is because the light beams having wavelengths included in the first wavelength range or the second wavelength range are reflected twice, that is, an even number of times.

[0087] First image 91a and second image 91b are in a translational relationship. For this reason, it is impossible for points corresponding to the same position within subject 91 to have the same distance from reference position 95-3. Reference position 95-3 is the position where the optical axis of imaging optical system 94 passes through imaging range 95-2.

[0088] The characteristics of the image formed by the imaging optical system 94 differ depending on the distance from the reference position 95 - 3 , resulting in the following problems.

[0089] The first issue is curvature aberration: the image formed by the imaging optical system 94 generally does not have a correct similarity relationship with the subject 91 . Figure 47A and Figure 47B : is a diagram schematically showing an example of curvature aberration. Even if the square is photographed as the subject 91, the photographed square may be distorted as shown in FIG. Figure 47A The pillow shape shown or Figure 47B The barrel shape shown. The amount of distortion depends on the relative position to the reference position 95-3.

[0090] like Figure 46 As shown, the line connecting points 91a1, 91a2, and 91a3 in the first image 91a is substantially straight, but the line connecting points 91b1, 91b2, and 91b3 corresponding to the same range in the second image 91b is curved. Here, barrel-shaped distortion is used as an example.

[0091] When curvature aberration occurs in this manner, the corresponding positional relationship between first image 91a and second image 91b is expressed by a complex function. Furthermore, the curvature aberration characteristics of each imaging optical system 94 differ. Therefore, it is difficult to determine the first position in first image 91a and the second position in second image 91b corresponding to the same position in subject 91, and it is also difficult to calculate the intensity ratio between them.

[0092] The second issue is edge vignetting. Generally speaking, the farther away from reference position 95-3, the darker the image becomes. This phenomenon is called edge vignetting. Due to edge vignetting, the ratio of the intensity at the first position in first image 91a to the intensity at the second position in second image 91b is the ratio of the radiation intensity in the first wavelength range to the radiation intensity in the second wavelength range multiplied by the ratio of the degree of edge vignetting. For example, point 91b2 is farther from reference position 95-3 than point 91a2, so the ratio of the degree of edge vignetting at point 91b2 to the degree of edge vignetting at point 91a2 is relatively large. On the other hand, point 91a4 is the same distance from reference position 95-3 as point 91b4, so the ratio of the degree of edge vignetting at point 91b4 to the degree of edge vignetting at point 91a4 is approximately 1.

[0093] Determining the temperature of subject 91 requires calculating the ratio of the intensity of thermal radiation within the first wavelength range to the intensity of thermal radiation within the second wavelength range. However, in imaging device 90A of Patent Document 1, the intensity ratio between first image 91a and second image 91b formed on image sensor 95 depends not only on the intensity ratio of the thermal radiation but also on the ratio of the degree of edge vignetting. Furthermore, the ratio of the degree of edge vignetting varies depending on the position within first image 91a and second image 91b. The ratio of the degree of edge vignetting also depends on, for example, the aperture of the lens.

[0094] Therefore, even if, for example, a position in first image 91a and a position in second image 91b corresponding to the same position in subject 91 can be determined, it is still difficult to easily determine the intensities of thermal radiation in the first wavelength range and the second wavelength range based on the imaging results. As a result, it is difficult to accurately measure the temperature of subject 91. The ratio of the intensities in the first wavelength range and the second wavelength range depends on the thermal radiation and should not be dependent on the imaging optical system 94. The above-mentioned problem arises in all applications that require measuring the ratio of the intensities in the first wavelength range and the second wavelength range.

[0095] [Example 2 of Conventional Image Capture Device]

[0096] Figure 48 FIG2 is a diagram schematically showing Example 2 of a conventional imaging device based on Patent Document 2. Figure 48 In the illustrated imaging device 90B, a light beam from a subject 91 enters an imaging optical system 94. A dichroic prism 96 separates the light beam that has passed through the imaging optical system 94 into a light beam having a wavelength within a first wavelength range and a light beam having a wavelength within a second wavelength range. The light beam having a wavelength within the first wavelength range is caused to enter a first image sensor 95a, while the light beam having a wavelength within the second wavelength range is caused to enter a second image sensor 95b. In other words, the light beam having a wavelength within the first wavelength range passes through the imaging optical system 94 and is imaged on the first image sensor 95a via the dichroic prism 96. The light beam having a wavelength within the second wavelength range passes through the imaging optical system 94 and is imaged on the second image sensor 95b via the dichroic prism 96.

[0097] In imaging device 90B, first image sensor 95a and second image sensor 95b must be positioned behind dichroic prism 96. Furthermore, two control circuits are required to control these two image sensors 95a and 95b, respectively. The need for two image sensors and two control circuits is costly. Furthermore, imaging device 90B cannot capture images using a conventional camera equipped with a single image sensor 95. Consequently, developing a dedicated camera for imaging device 90B is both time-consuming and expensive.

[0098] The camera device 90B is also limited in the selection of the imaging optical system 94. Generally speaking, the lens device including the imaging optical system 94 and the camera including the image sensor 95 are designed and manufactured based on standards. The lens device and the camera can be freely combined and used within the scope of the same standard. In general standards, the shape of the joint between the lens device and the camera is specified. In addition, the distance from the joint to the image sensor 95 in the camera, that is, the flange back, is also specified. For example, in the C-mount standard widely used in industrial applications, the inner diameter of the joint is specified to be 25.4 mm, the pitch is 0.794 mm, and the flange back is 17.526 mm.

[0099] Although the distance from the joint to the rearmost lens surface of the imaging optical system 94 is not usually specified in the standard, it is generally allowed to be zero. Therefore, the minimum value of the back focus (back focus) from the rearmost lens surface of the imaging optical system 94 to the image sensor 95 is generally equal to the flange focal length.

[0100] In the imaging device 90B, dichroic prisms 96 are disposed between the imaging optical system 94 and the first image sensor 95a, and between the imaging optical system 94 and the second image sensor 95b. Therefore, the back focus of the imaging optical system 94 cannot be set smaller than the size of the dichroic prisms 96. Restricting the size of the dichroic prisms 96 limits, for example, the thickness and field angle of the light beam passing through the dichroic prisms 96. Consequently, the brightness of the acquired image and the imaging range are restricted. Since the back focus value of the imaging optical system 94 is insufficient for conventional camera standards, the dichroic prism 96 cannot be disposed when using such an imaging optical system 94.

[0101] Conventional camera standards stipulate that a lens assembly and a camera be joined such that the optical axis of the imaging optical system 94 is perpendicular to the imaging surface of the image sensor 95. However, in the imaging device 90B, the optical axis of the imaging optical system 94 and the imaging surface of the first image sensor 95a are at an angle. The same applies to the optical axis of the imaging optical system 94 and the imaging surface of the second image sensor 95b. This arrangement makes it difficult to easily combine a lens assembly and a camera that conform to conventional camera standards.

[0102] Furthermore, in the imaging device 90B, a dichroic prism 96 is disposed on the first image sensor 95a and the second image sensor 95b side with respect to the imaging optical system 94. The convergent light beam that converges from the imaging optical system 94 toward the first image sensor 95a passes through the dichroic prism 96. The same applies to the convergent light beam that converges from the imaging optical system 94 toward the second image sensor 95b.

[0103] Since dichroic prism 96 is formed of a dielectric material, refraction occurs when the converging light beam enters and exits dichroic prism 96. This refraction causes spherical aberration when the converging light beam passes through dichroic prism 96. Chromatic aberration also occurs because the refractive index of dielectric materials is wavelength-dependent.

[0104] As the angular divergence of the converging light beam increases, both spherical aberration and chromatic aberration increase. In order to suppress these aberrations in the imaging device 90B, it is necessary to increase the distance between the imaging optical system 94 and the first image sensor 95a, and the distance between the imaging optical system 94 and the second image sensor 95b. Therefore, miniaturization of the imaging device 90B is not easy.

[0105] The inventors have discovered the above-mentioned problem and devised imaging devices according to embodiments of the present disclosure to solve this problem. The following describes imaging devices according to Embodiments 1 and 2. The imaging device according to Embodiment 1 captures two images of a subject in different wavelength ranges as an example of two images having different optical properties. The imaging device according to Embodiment 2 captures two images of a subject having different polarization states as another example of two images having different optical properties.

[0106] (Implementation 1)

[0107] [Camera]

[0108] Below, refer to Figure 1 , a structural example of the camera device according to the first embodiment of the present disclosure is described. Figure 1 This is a diagram schematically showing the configuration of an imaging device according to the exemplary embodiment 1 of the present disclosure. Figure 1 A subject 110 is also shown in FIG. Figure 1 The imaging device 100 shown in FIG. 1 obtains two images in different wavelength ranges from a subject 110. Figure 1 As shown, the imaging device 100 includes an optical component 10A comprising a first subcomponent 10A1 and a second subcomponent 10A2; a lens assembly 20A comprising an imaging optical system 20; and a camera 30A comprising an image sensor 30. However, the second subcomponent 10A2 is not necessarily an essential component of the optical component 10A. The imaging device 100 has a simple structure consisting of the optical component 10A in addition to the lens assembly 20A and the camera 30A.

[0109] The first sub-assembly 10A1 includes at least one optical element, and the same is true for the second sub-assembly 10A2. Figure 1 The first subassembly 10A1 , the second subassembly 10A2 , and the imaging optical system 20 are abstractly shown.

[0110] The first subassembly 10A1 includes a dichroic surface that separates the light beam L from the subject 110 into a first light beam La having a wavelength within a first wavelength range and a second light beam Lb having a wavelength within a second wavelength range. The dichroic surface is arranged in a plane including the optical axis of the imaging optical system 20 . Figure 1 The solid arrow shown represents the light beam L from the subject 110 . Figure 1 The dashed arrow shown represents a first light beam La having a wavelength included in the first wavelength range, Figure 1 The dotted arrow shown represents the second light beam Lb having a wavelength included in the second wavelength range. The first wavelength range and the second wavelength range are wavelength ranges different from each other.

[0111] The first subassembly 10A1 further converts the directions of the first and second light beams La and Lb, which move away from each other as they move away from the dichroic surface. The first light beam La has a wavelength within the first wavelength range, and the second light beam Lb has a wavelength within the second wavelength range, and emits them toward the imaging optical system 20. By making the angle between the two light beams after conversion smaller than the angle between the two light beams before conversion, the two light beams are more easily incident on the imaging optical system 20.

[0112] The imaging optical system 20 forms images of the first light beam La and the second light beam Lb incident upon it on the image sensor 30, forming images of the first wavelength range and images of the second wavelength range at different positions on the image sensor 30. The images of the first wavelength range and the images of the second wavelength range formed on the image sensor 30 are mirror-symmetrical.

[0113] However, since the dichroic surface in the first subassembly 10A1 is arranged on a plane including the optical axis of the imaging optical system 20 , the direction of the light beam L incident on the dichroic surface cannot be parallel to the optical axis of the imaging optical system 20 .

[0114] Therefore, the second subassembly 10A2 can be positioned between the subject 110 and the first subassembly 10A1. The second subassembly 10A2 emits the light beam L from the subject 110 in a direction different from the incident direction, and causes the light beam L from the subject 110 to be incident on the dichroic surface. Therefore, even when the subject 110 is located approximately on an extension of the optical axis of the imaging optical system 20, the light beam L from the subject 110 can be incident on the dichroic surface. As a result, the direction in which the subject 110 is located can be made substantially aligned with the direction of the optical axis of the imaging optical system 20, enabling imaging in a natural orientation.

[0115] The specific structures of the first sub-component 10A1 and the second sub-component 10A2 will be described later.

[0116] In this specification, a light beam having a wavelength included in the first wavelength range is also referred to as a "first light beam," and a light beam having a wavelength included in the second wavelength range is also referred to as a "second light beam." An image in the first wavelength range is also referred to as a "first image," and an image in the second wavelength range is also referred to as a "second image."

[0117] In addition, the change in the direction of travel of a light beam in an actual optical element is caused by refraction or reflection. The change in the direction of travel of the light beam caused by refraction may depend on, for example, the refractive index of the optical element, the angle of incidence of the light beam entering the incident surface of the optical element, and the angle of exit of the light beam from the exit surface of the optical element. The closer the incident angle is to perpendicular to the incident surface and the closer the exit angle is to perpendicular to the exit surface, the smaller the change in the direction of travel of the light caused by refraction. If the incident angle and the exit angle are completely perpendicular, the change in the direction of travel of the light caused by refraction is zero. In the following description, for simplicity, the change in the direction of travel of the light beam caused by refraction is ignored.

[0118] Light reflection is caused by metal, dielectric multilayer films, or total internal reflection. For reflection to occur due to dielectric multilayer films other than metal or total internal reflection, certain conditions must be met in terms of angle range or wavelength range. These conditions are well known and readily understood by those skilled in the art, so their explanation is omitted. In this specification, situations where reflection is described as occurring are assumed to satisfy these conditions.

[0119] The method of defining the traveling directions of the light beam L, the first light beam La, and the second light beam Lb is as follows. Here, the traveling direction of the light beam L is taken as an example. Figure 2 Schematically shows the situation where the light beam L is reflected by a mirror. Figure 2 As shown in the figure, when light beam L is reflected by a mirror, its direction changes to a direction that is mirror-inverted with respect to a plane perpendicular to the mirror. The direction of light beam L is defined by the angle measured counterclockwise from the reference direction, which is the reference direction within the paper. Figure 2 The curved arrows shown indicate clockwise or counterclockwise rotation. In the case of mirror reflection, the direction of the reflected light beam L changes to or π is the ratio of the circumference of a circle to its circumference. The unit of angle containing π is radians.

[0120] Below, based on the above general principles, the changes in the traveling directions of the light beam L, the first light beam La, and the second light beam Lb are described. In addition, the angles representing the traveling directions of the light beam L, the first light beam La, and the second light beam Lb can have both positive and negative values. Figure 2 As shown, two angles with a difference of 2nπ (n is an integer) indicate the same direction of travel. Angles other than this are generally positive. This angle can be, for example, the angle between two faces in a prism.

[0121] [Specific Configuration Example of the Imaging Device]

[0122] Below, refer to Figure 3 A specific configuration example of the imaging device according to the first embodiment of the present disclosure will be described. Figure 3 This is a diagram schematically showing a specific configuration of an imaging device according to the exemplary embodiment 1 of the present disclosure. Figure 3 A subject 110 is also shown in FIG. Figure 3 The imaging device 100 shown in FIG. 1 obtains two images in different wavelength ranges from a subject 110. Figure 3 As shown, the imaging apparatus 100 includes an optical component 10A, a lens device 20A, and a camera 30A.

[0123] The optical component 10A includes a dichroic prism 10, an optical path adjusting element 10-1, a light shielding body 10-2, and a frame 12 for accommodating them. However, the optical path adjusting element 10-1, the light shielding body 10-2, and the frame 12 are not essential components. The dichroic prism 10 corresponds to Figure 1 The first subcomponent 10A1 shown, the optical path adjustment element 10-1 corresponds to Figure 1 The second subassembly 10A2 is shown.

[0124] In this specification, the dichroic prism 10 is also referred to as a “first optical element”, and the optical path adjustment element 10 - 1 is also referred to as a “second optical element”.

[0125] The lens unit 20A includes an imaging optical system 20 and a lens housing 22 that houses the imaging optical system 20. The camera 30A includes an image sensor 30 and a camera housing 32 that houses the image sensor 30. However, the lens housing 22 and the camera housing 32 are not essential components. The lens unit 20A and the camera 30A may be, for example, a typical commercially available lens unit and camera, respectively.

[0126] The imaging device 100 includes at least a dichroic prism 10, an imaging optical system 20, and an image sensor 30. The imaging device 100 may further include other components as necessary.

[0127] In addition, although the imaging optical system 20 can be composed of multiple lenses, for the sake of simplicity, it may be shown as a single lens or two lenses. The shape of the lens shown has nothing to do with the actual shape of the lens. The direction and divergence of the light beam may also be exaggerated in the illustration.

[0128] It will be described in detail later. In the imaging device 100, as shown in FIG. Figure 3 As shown, the dichroic prism 10 separates the light beam L from the subject 110 into a first light beam La and a second light beam Lb. The first light beam La and the second light beam Lb are emitted symmetrically with respect to a plane. This plane includes the optical axis of the imaging optical system 20. The imaging optical system 20 forms images of the first light beam La and the second light beam Lb, which enter the imaging optical system at different angles, on the imaging surface of the image sensor 30, forming the first image and the second image at different positions on the imaging surface.

[0129] The first and second images on the imaging plane are not shifted but rather mirror-symmetrical, which reduces the effects of aberrations. Therefore, the first and second images are suitable for evaluating the subject 110 using methods such as two-color thermal imaging and fluorescence imaging. Furthermore, the aforementioned structure in which the optical component 10A is added to the lens device 20A and the camera 30A is simple.

[0130] Thus, the imaging device 100 of the first embodiment can acquire two images in different wavelength ranges suitable for evaluating the subject 110 with a simple configuration. Furthermore, the imaging device 100 of the first embodiment can also include an optical path adjustment element 10-1 between the subject 110 and the dichroic prism 10. The optical path adjustment element 10-1 changes the direction of the light beam L from the subject 110 before it enters the dichroic prism 10. Therefore, the subject 110 can be imaged with the subject 110 positioned along the optical axis of the imaging optical system 20 and in a natural orientation relative to the image sensor 30.

[0131] Hereinafter, the components of the imaging device 100 will be described in detail.

[0132] [Components of the Imaging Device 100]

[0133] <Dichroic Prism 10>

[0134] Figure 4 1 is a diagram schematically showing an example of a dichroic prism 10. Figure 4 As shown, the dichroic prism 10 includes a first right-angle prism 10a and a second right-angle prism 10b. The first right-angle prism 10a has a surface 10a1, a surface 10a2, and a surface 10a3. The second right-angle prism 10b has a surface 10b1, a surface 10b2, and a surface 10b3.

[0135] The first right-angle prism 10a has a triangular prism shape and, in addition to surfaces 10a1 to 10a3, has two bottom surfaces located on opposite sides of each other. However, since these two bottom surfaces do not contribute to the operation, their description will be omitted. The two bottom surfaces of the first right-angle prism 10a can be painted black to prevent reflection. The same applies to the two bottom surfaces of the second right-angle prism 10b. It is assumed that the first right-angle prism 10a and the second right-angle prism 10b have sufficient thickness to allow the light beam L from the subject to be imaged on the image sensor 30.

[0136] In the first right-angle prism 10a, the surface 10a1 and the surface 10a2 form an angle α, and the surface 10a1 and the surface 10a3 form an angle α'. In the second right-angle prism 10b, the surface 10b1 and the surface 10b2 form an angle β, and the surface 10b1 and the surface 10b3 form an angle β'. These angles have positive values. Since it is a right-angle prism, the angle α and the angle β are each 30°, and the angle α' and the angle β' are each 60°. However, it is not necessary to use a right-angle prism, and the values ​​of the three internal angles of the prism are arbitrary. Angle α and angle β can be equal to each other or different. Angle α' and angle β' can be equal to each other or different. In the following, for the sake of convenience, it is assumed that angle α and angle β are equal to each other, and angle α' and angle β' are equal to each other.

[0137] Surface 10a2 and surface 10b2 are bonded together by an adhesive layer. The adhesive layer is translucent in the second wavelength range. Surface 10a2 and surface 10b2 can be, for example, parallel to each other. As a result of bonding surface 10a2 and surface 10b2, first right-angle prism 10a and second right-angle prism 10b are configured to be mirror-symmetrical to each other.

[0138] One or both of surfaces 10a2 and 10b2 may be, for example, a dichroic surface that reflects the first light beam La and transmits the second light beam Lb in the light beam L incident from a specific range of directions. The dichroic surface performs the aforementioned function when the first right-angle prism 10a and the second right-angle prism 10b are bonded together. Here, the specific range of directions refers to the range of directions from which the light beam L from the subject 110 is incident. Thus, the dichroic prism 10 has at least one such dichroic surface.

[0139] In the following description, it is assumed that surface 10a2 is a dichroic surface, the direction in the specific range is the direction close to the normal of surface 10a1, and surface 10a2 and surface 10b2 are parallel to each other. Surface 10b1 is a reflective surface that reflects the second light beam Lb. Surface 10b1 can have a metal film such as gold, silver, or aluminum, or a dielectric multilayer film. The metal film and the dielectric multilayer film have a high reflectivity of 60% or 80% or more with respect to the second light beam Lb. The reflection of the second light beam Lb by surface 10b1 can be caused by the metal film or the dielectric multilayer film. Alternatively, the reflection can be caused by total internal reflection caused by the difference between the refractive index of the material constituting the second right-angle prism 10b and the refractive index of the outside.

[0140] The paths of the light beam L, the first light beam La, and the second light beam Lb in the dichroic prism 10 will be described. Figure 5 1 is a diagram schematically showing an example of the paths of the light beams L, La, and Lb in the dichroic prism 10 . Figure 5 The illustrated beam L, first beam La, and second beam Lb merely represent the optical path of the principal ray. In practice, the dichroic prism 10 allows the beam L, first beam La, and second beam Lb to pass through beams having different widths and angular ranges. In this case, the required symmetry and positional relationship between surfaces 10a1 to 10a3 and surfaces 10b1 to 10b3 are also as described above. The size of the dichroic prism 10 is appropriately designed based on the widths of the beam L, first beam La, and second beam Lb, as well as the specifications of the imaging optical system 20.

[0141] like Figure 5 As shown, in the first right-angle prism 10a, a light beam L incident from the outside on surface 10a1 reaches surface 10a2. Within light beam L, the component in the first wavelength range is reflected by surface 10a2, which functions as a dichroic surface, becoming a first light beam La. First light beam La is reflected by surface 10a1 and emitted to the outside from surface 10a3. The reflection of first light beam La by surface 10a1 is total internal reflection, and the angle of incidence of first light beam La on surface 10a1 is greater than the critical angle.

[0142] The component within the second wavelength range of light beam L passes through surface 10a2, which functions as a dichroic surface, and the adhesive layer, and becomes second light beam Lb in second right-angle prism 10b. Second light beam Lb is reflected by surface 10b1 and emitted to the outside through surface 10b3. The reflection of second light beam Lb by surface 10b1 is either total internal reflection or reflection caused by a metal film or a dielectric multilayer film.

[0143] In the second right-angle prism 10b, when the light beam L is incident on the surface 10b1 from the outside, the first light beam La can be emitted from the surface 10b3 and the second light beam Lb can be emitted from the surface 10a3 in symmetry with the above-mentioned light beam L. However, due to Figure 3In the light-shielding member 10 - 2 shown, the light beam L does not enter the surface 10 b 1 from the outside. Therefore, the first light beam La is emitted from the surface 10 a 3 of the dichroic prism 10 , and the second light beam Lb is emitted from the surface 10 b 3 of the dichroic prism 10 .

[0144] As described above, the dichroic prism 10 separates the light beam L into the first light beam La and the second light beam Lb through the surface 10a2. The dichroic prism 10 also converts the directions of the first light beam La and the second light beam Lb through the surfaces 10a1 and 10b1 and emits them.

[0145] In the dichroic prism 10 , the angle α and the angle β are equal to each other, and the angle α′ and the angle β′ are equal to each other. Therefore, the optical paths of the first light beam La and the second light beam Lb are substantially symmetrical with respect to the surface 10 a 2 .

[0146] Here, "substantially symmetrical about surface 10a2" means that differences due to the wavelength dependence of the refraction of light beam L, first light beam La, and second light beam Lb are negligible in the following situations: when second light beam Lb in light beam L is incident on second right-angle prism 10b from first right-angle prism 10a, when first light beam La is emitted from first right-angle prism 10a, and when second light beam Lb is emitted from second right-angle prism 10b. The refraction of light beam L, first light beam La, and second light beam Lb depends on the angle of incidence of light beam L on surface 10a2, the angle of incidence of first light beam La on surface 10a3, and the angle of incidence of second light beam Lb on surface 10b3. The closer these angles of incidence are to right angles, the less refraction occurs.

[0147] The first and second right-angle prisms 10a, 10b can be designed so that the angle of emergence of the first light beam La from surface 10a3 and the angle of emergence of the second light beam Lb from surface 10b3 are close to right angles. Alternatively, a glass material having a small difference in refractive index between the first and second wavelength ranges can be selected for the first and second right-angle prisms 10a, 10b. By selecting such a glass material, the possibility of asymmetry between the first and second light beams La, Lb can be reduced.

[0148] The propagation directions of the first and second light beams La and Lb are as follows. Surface 10a2 is used as the angle reference, and the propagation direction of the light beam L incident on surface 10a1 is θ. In this case, the propagation direction of the first light beam La reflected by surface 10a2 is θ + 2α. The propagation direction of the second light beam Lb reflected by surface 10b1 is -θ - 2α.

[0149] In particular, when the incident direction of the light beam L is θ = -2α, the traveling direction of the first light beam La becomes θ + 2α = 0, and the traveling direction of the second light beam Lb becomes -θ - 2α = 0. Therefore, both the first light beam La and the second light beam Lb emitted from the dichroic prism 10 are parallel to the surface 10a2.

[0150] When the incident direction of the light beam L satisfies θ>-2α, the traveling direction of the first light beam La satisfies θ+2α>0, and the traveling direction of the second light beam Lb satisfies -θ-2α<0. Therefore, the first light beam La and the second light beam Lb travel away from each other.

[0151] When the incident direction of the light beam L satisfies θ<-2α, the traveling direction of the first light beam La satisfies θ+2α<0, and the traveling direction of the second light beam Lb satisfies -θ-2α>0. Therefore, the first light beam La and the second light beam Lb approach each other while traveling.

[0152] like Figure 3 As shown, the first light beam La and the second light beam Lb are both incident on the imaging optical system 20. The dichroic prism 10 and the imaging optical system 20 are configured to satisfy the following conditions. Figure 5 As shown, the first and second beams La and Lb enter the imaging optical system 20 so as to be substantially symmetrical with respect to a plane 24 including the optical axis of the imaging optical system 20. This condition is satisfied when the plane 24 includes the surface 10a2.

[0153] <Imaging Optical System 20>

[0154] The imaging optical system 20 is substantially symmetrical about plane 24 and has optical symmetry with respect to its optical axis. The first light beam La and the second light beam Lb enter the imaging optical system 20 at different angles and symmetrically about plane 24. The optical axes of the first light beam La and the second light beam Lb are not parallel to each other. The imaging optical system 20 has a refractive power and forms a first image by imaging the first light beam La and a second image by imaging the second light beam Lb. Due to the symmetrical entry of the first light beam La and the second light beam Lb, the first and second images are mirror-symmetrical, as described later.

[0155] Here, "imaging optical system 20 is substantially symmetrical with respect to plane 24" means that the elements of imaging optical system 20 that significantly affect the symmetry of the shapes and brightness of the first and second images are substantially symmetrical with respect to plane 24. Due to manufacturing tolerances, shape distortion, decentration, and slight positional deviations may occur.

[0156] It goes without saying that the arrangement of elements such as the housing 12, lens housing 22, camera housing 32, and circuitry that do not affect the symmetry between the first and second images is not critical. Furthermore, even if the aperture has a polygonal shape and does not strictly satisfy symmetry, strict symmetry need not be satisfied if the effect on the symmetry of the image shape and brightness is essentially negligible.

[0157] The imaging optical system 20 is arranged so that the plane 24 includes the normal vector of the imaging surface of the image sensor 30. This is because, in addition to the case where the optical axis of the imaging optical system 20 and the normal vector of the imaging surface of the image sensor 30 are parallel, this also includes the case of so-called oblique imaging, in which the optical axis of the imaging optical system 20 and the normal vector of the imaging surface of the image sensor 30 are not parallel. Even in oblique imaging, the symmetry between the first light beam La and the second light beam Lb is maintained.

[0158] When the imaging range of the image sensor 30 has a symmetrical shape, the plane 24 may include the axis of symmetry or the point of symmetry of the imaging range. For example, when the imaging range has a rectangular shape, the plane 24 may be located parallel to the short side of the imaging range and passing through the midpoint of the long side.

[0159] The imaging optical system 20 may have substantially the same optical characteristics in the first wavelength range and the second wavelength range, for example. The optical characteristics may be, for example, chromatic aberration of magnification, axial chromatic aberration, field curvature, and edge vignetting.

[0160] If both the chromatic aberration of magnification and the axial chromatic aberration are small in the first and second wavelength ranges, it is easy to determine the corresponding positions within the first and second images. Regarding chromatic aberration of magnification, when using an imaging optical system 20 whose characteristics are known, the corresponding positions within the first and second images can be determined based on known information.

[0161] If the field curvatures in the first wavelength range and the second wavelength range are the same, it is easy to determine the corresponding positions in the first image and the second image. The same applies to the edge vignetting in the first wavelength range and the second wavelength range.

[0162] <Image Sensor 30>

[0163] The image sensor 30 has an imaging surface. A first image and a second image are formed at different positions on the imaging surface. The first image and the second image are mirror-symmetrical to each other. Even if the image sensor 30 is a single unit, the first image and the second image formed in this way can be obtained.

[0164] Image sensor 30 includes a plurality of photoelectric conversion elements arranged one-dimensionally or two-dimensionally. The plurality of photoelectric conversion elements form an imaging surface. The photoelectric conversion elements are sensitive to a first wavelength range and a second wavelength range, respectively. The photoelectric conversion elements convert the light intensity at each point in the first image and the second image into an electrical signal.

[0165] The sensitivity of the photoelectric conversion element in the first wavelength range and the second wavelength range can be the same or different. When imaging thermal radiation in the first wavelength range and the second wavelength range, the intensity of the thermal radiation emitted from the subject 110 in the first wavelength range and the second wavelength range is often relatively high in one case and relatively low in the other. In this case, the sensitivity can be lower in the wavelength range with relatively high intensity and higher in the wavelength range with relatively low intensity. By adjusting the sensitivity in this way, the signal intensities of the two are brought closer together. As a result, the possibility of saturation of one case due to excessive signal intensity or the possibility of the other case being buried in noise due to insufficient signal intensity can be reduced.

[0166] When the image sensor 30 includes a plurality of photoelectric conversion elements arranged one-dimensionally, the camera 30A may further include a scanning device for acquiring a two-dimensional image. The camera 30A may further include a filter array having a specific optical function as described later.

[0167] The camera 30A includes a control circuit that controls the operation of the image sensor 30. The control circuit acquires the electrical signals output from the photoelectric conversion elements and outputs image data.

[0168] In the imaging apparatus 100, the lens unit 20A and the camera 30A do not require any special elements or structures other than those used for general imaging. Therefore, any combination of general lens units and cameras can be used in the imaging apparatus 100. Since the lens unit 20A and the camera 30A are detachable, any such combination is possible.

[0169] The lens unit 20A and camera 30A can be those that conform to standards such as C-mount and F-mount. In this case, one or both of the lens unit 20A and camera 30A can be replaced within the range that conforms to the standard. This replacement is effective when changing the focal length of the lens to adjust the imaging range according to the size of the subject 110, or when switching to a high-frame-rate camera for high-speed shooting.

[0170] <Optical Path Adjustment Element 10-1>

[0171] The optical path adjustment element 10-1 is provided as an auxiliary device as needed. Figure 3As shown, the optical path adjusting element 10-1 changes the direction of the light beam L from the subject 110 and makes the light beam L enter the dichroic prism 10. The optical path adjusting element can be composed of a reflecting prism or a reflecting mirror such as a right angle prism or a half pentaprism.

[0172] In the case where the optical path adjustment element 10-1 is not configured, Figure 3 In the example shown, the subject 110 is positioned obliquely above the imaging optical system 20, in a direction that is not parallel to the optical axis of the imaging optical system 20. In a typical lens assembly and camera combination, the subject 110 is generally always positioned in the direction of the optical axis of the imaging optical system 20. Therefore, positioning the subject 110 obliquely above the imaging optical system 20 is counterintuitive. This issue can be addressed by placing an optical path adjustment element 10-1 between the subject 110 and the dichroic prism 10.

[0173] The optical path adjustment element 10-1 reflects or totally reflects the light beam L incident in a direction substantially parallel to the optical axis of the imaging optical system 20, and then emits it in a direction different from its original direction. By appropriately designing the optical path adjustment element 10-1, the first light beam La and the second light beam Lb separated from the light beam L by the dichroic prism 10 are emitted from the dichroic prism 10 at appropriate angles. As a result, the first light beam La and the second light beam Lb can be imaged by the imaging optical system 20, forming a first image and a second image, respectively, at desired positions on the image sensor 30. The design of the optical path adjustment element 10-1 can be achieved, for example, by adjusting the angle of the surface where the reflection or total reflection occurs.

[0174] Figure 6 1 is a diagram schematically showing an example of the optical path adjustment element 10-1. Figure 6 In the example shown, the optical path adjustment element 10-1 is a right-angle prism having the shape of a triangular prism. The optical path adjustment element 10-1 has a surface 10-1a1, a surface 10-1a2, and a surface 10-1a3 as side surfaces. In addition to the surfaces 10-1a1 to 10-1a3, the optical path adjustment element 10-1 also has two bottom surfaces located on opposite sides of each other. However, since the two bottom surfaces do not contribute to the action, their description is omitted. Surface 10-1a2 and surface 10-1a3 form an angle γ. Since it is a right-angle prism, the angle γ is π / 6. However, it is not necessarily necessary to use a right-angle prism, and the values ​​of the three internal angles of the optical path adjustment element 10-1 are arbitrary. Surface 10-1a3 can have a metal film or a dielectric multilayer film to achieve high light reflectivity.

[0175] Figure 7 10 - 1 is a diagram schematically showing an example of the path of the light beam L in the optical path adjustment element 10 - 1 . Figure 7 As shown, surface 10-1a3 is Figure 5The surface 10a2 is shown as having a reference inclination angle η.

[0176] Direction of travel After the light beam L enters the surface 10-1a1, it is totally reflected by the surface 10-1a2. Since the surface 10-1a2 is inclined at an angle η+γ relative to the surface 10a2, the direction of the light beam L totally reflected by the surface 10-1a2 is The light beam L totally reflected by the surface 10-1a2 is totally reflected by the surface 10-1a3. The traveling direction of the light beam L totally reflected by the surface 10-1a3 becomes That is, the traveling direction of the light beam L totally reflected by the surface 10-1a3 is rotated by an angle of -2γ from the traveling direction of the light beam L incident on the surface 10-1a1 and is independent of the angle η. This is because the influence of the angle η is offset by the reflections from the surfaces 10-1a2 and 10-1a3.

[0177] This phenomenon occurs in all prisms where the light beam L, the first light beam La, and the second light beam Lb are reflected twice by the inner surface. Therefore, hereinafter, in the case where the light beam L, the first light beam La, and the second light beam Lb are reflected twice by the inner surface of the prism, the configuration angle of the prism will not be specifically mentioned.

[0178] In the imaging device 100, at least one of the following may be provided, for example, in place of or in addition to the optical path adjustment element 10-1: an optical filter, an optical system, and a light shield. The optical filter blocks or attenuates light beams in wavelength ranges other than the first and second wavelength ranges. The optical system corrects spherical aberration caused by the prism. The light shield limits the imaging range of the subject 110.

[0179] <Light-shielding body 10-2>

[0180] The light shielding body 10-2 is configured as an auxiliary as needed. The light shielding body 10-2 blocks the unexpected light beam from entering the dichroic prism 10. As a result, stray light can be reduced. Figure 3 As shown, the light shielding body 10-2 is configured so that the light beam L is incident from the outside into the dichroic prism 10. Figure 5 The specific surface of the first right angle prism 10a is not incident on other surfaces. Figure 5 The light shielding body 10-2 blocks the light beam L from entering the dichroic prism 10 from the outside. Figure 5 The light shielding body 10-2 also blocks the light beam L from entering the two bottom surfaces of the first right angle prism 10a and the two bottom surfaces of the second right angle prism 10b.

[0181] like Figure 3As shown, the light shielding member 10-2 may be, for example, a light-shielding object disposed separately from the dichroic prism 10. Alternatively, the light shielding member 10-2 may be, for example, a light-shielding layer formed on a surface of the dichroic prism 10 that the light beam is not intended to enter. The metal film or dielectric multilayer film on the surface 10b1 that reflects the second light beam Lb may also be configured to function as the light shielding member 10-2.

[0182] [Paths of the Light Beam L, the First Light Beam La, and the Second Light Beam Lb in the Optical Component 10A]

[0183] Figure 8 Schematically shows the paths of the light beam L, the first light beam La, and the second light beam Lb in the optical component 10A. Figure 8 In, omitted Figure 3 The light shielding body 10-2 and the frame 12 are shown. The light beam L incident on the optical path adjustment element 10-1 is reflected by the inner surface and finally moves in the direction Emitted from the optical path adjustment element 10-1.

[0184] The light beam L enters the dichroic prism 10 from the surface 10a1 and is separated into the first light beam La and the second light beam Lb by the surface 10a2. The second light beam Lb is emitted from the dichroic prism 10 in the direction The light beam L is emitted from the dichroic prism 10. That is, the optical component 10A emits the incident light beam L as a first light beam La and a second light beam Lb that are mirror-symmetrical with respect to the surface 10a2.

[0185] In particular, in meeting In the case of , the traveling directions of the first light beam La and the second light beam Lb emitted from the dichroic prism 10 are both zero. If the angle γ is made substantially equal to the angle α, the direction Therefore, when the traveling direction of the light beam L incident on the optical path adjustment element 10 - 1 is approximately parallel to the optical axis of the imaging optical system 20 , the traveling directions of the first light beam La and the second light beam Lb emitted from the dichroic prism 10 become approximately parallel to the optical axis of the imaging optical system 20 .

[0186] In addition, in this specification, "the traveling directions of the light beam L, the first light beam La and the second light beam Lb are substantially parallel to the optical axis direction of the imaging optical system 20" not only means that the traveling directions of the light beam L, the first light beam La and the second light beam Lb are strictly parallel to the optical axis direction of the imaging optical system 20, but also means that the angle formed by the traveling directions of the light beam L, the first light beam La and the second light beam Lb and the optical axis direction of the imaging optical system 20 is less than π / 36.

[0187] [General Characteristics of the Imaging Optical System 20]

[0188] Figure 9 2 is a diagram for explaining general characteristics of the imaging optical system 20. The imaging optical system 20 has a front principal point 26a and a rear principal point 26b on its optical axis.

[0189] Among the light rays incident in a direction of -θ relative to the optical axis of the imaging optical system 20, the light rays that pass through the front principal point 26a become the light rays emitted in a direction of -θ from the rear principal point 26b. Similarly, among the light rays incident in a direction of θ relative to the optical axis of the imaging optical system, the light rays that pass through the front principal point 26a become the light rays emitted in a direction of θ from the rear principal point 26b. Here, the light rays that pass through the front principal point 26a are referred to as principal rays.

[0190] If the distance from the rear principal point 26b to the image sensor 30 is D, then the subject 110, imaged at a position Dtanθ on the image sensor 30 with respect to the plane 24, is located in the direction θ+π with respect to the front principal point 26a. Similarly, the subject 110, imaged at a position -Dtanθ on the image sensor 30 with respect to the plane 24, is located in the direction -θ-π with respect to the front principal point 26a. The relationship between the direction of the subject 110 and the image position on the image sensor 30 can be understood from the principal rays described above.

[0191] [Paths of the Light Beam L, the First Light Beam La, and the Second Light Beam Lb in the Imaging Device 100]

[0192] Figure 10 1 is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the imaging device 100. Figure 10 In, omitted Figure 3 The light shield 10-2, frame 12, lens frame 22 and camera frame 32 are shown. The relationship between the direction of the subject 110 and the imaging position can be determined by the relationship between the incident direction of the light beam L and the emission directions of the first and second light beams La and Lb.

[0193] like Figure 10 As shown, the light beam L is in the direction When incident on the optical path adjustment element 10-1, the first light beam La enters the imaging optical system 20 in the direction -θ and passes through the front principal point 26a. The second light beam Lb enters the imaging optical system 20 in the direction θ and passes through the front principal point 26a. In this case, the first light beam La forms an image at a position -Dtanθ on the image sensor 30, and the second light beam Lb forms an image at a position Dtanθ on the image sensor 30. In other words, the first and second images on the image sensor 30 are mirror-symmetrical with respect to the plane including the surface 10a2.

[0194] The first light beam La is emitted from the surface 10a3 of the first right-angle prism 10a. Therefore, when the direction -θ of the first light beam La is negative, the first light beam La can include a principal ray passing through the front principal point 26a. In contrast, when the direction -θ of the first light beam La is positive, the first light beam La does not include such a principal ray. With plane 24 as a reference, a first image is formed on the image sensor 30 on the second right-angle prism 10b side. While the first image may sometimes be formed on the image sensor 30 on the first right-angle prism 10a side, it is generally darkened due to vignetting.

[0195] Second light beam Lb is emitted from surface 10b3 of second rectangular prism 10b. Therefore, when the direction θ of travel of second light beam Lb is positive, second light beam Lb can include a principal ray passing through front principal point 26a. When the direction θ of travel of second light beam Lb is negative, second light beam Lb does not include such a principal ray. With plane 24 as a reference, a second image is formed on the image sensor 30 on the side of first rectangular prism 10a. While the second image may sometimes be formed on the side of second rectangular prism 10b on image sensor 30, it is generally darkened due to the effects of vignetting.

[0196] Therefore, on the image sensor 30 , the main formation areas of the first image and the second image are different.

[0197] When the direction θ is zero, the first image and the second image formed at the position where the optical axis of the imaging optical system 20 intersects the image sensor 30 are located in the direction That is, the subject 110 is located in the direction The subject 110 is imaged at the center of the image sensor 30 .

[0198] Here, when α=γ, the direction in which the subject 110 is located is Therefore, the light beam L from the subject 110 located in the optical axis direction of the imaging optical system 20 forms a first image and a second image at the intersection of the optical axis of the imaging optical system 20 and the image sensor 30. The centers of the regions where the first and second images are formed are located in the direction of θ=0.

[0199] In contrast, when α≠γ, the direction in which the subject 110 is located is On the other hand, the direction The incident light beam L becomes a first light beam La emitted in the direction of -θ = -2γ + 2α, and a second light beam Lb emitted in the direction of θ = 2γ - 2α. With this structure, when the subject 110 is located on the optical axis of the imaging optical system 20, the first light beam La and the second light beam Lb can be imaged at different positions on the image sensor 30.

[0200] For example, the center of the range where the first light beam La forms an image on the image sensor 30 is located at -Dtan(2γ-2α), and the center of the range where the second light beam Lb forms an image on the image sensor 30 is located at Dtan(2γ-2α). By selecting α and γ to achieve this, the center of the subject 110 corresponding to the center of the first image and the center of the second image can be located in the direction of the optical axis of the imaging optical system 20. As a result, the imaging optical system 20 can be oriented in a natural direction to obtain the first and second images.

[0201] like Figure 10 As shown, the structure of combining the dichroic prism 10 and the optical path adjustment element 10-1 is compact because the distance between the two can be narrowed. In addition, the shape of the prism used in this structure is simple.

[0202] [Principles of obtaining the first and second images]

[0203] Next, the principle of obtaining the first image and the second image by the imaging device 100 of the first embodiment will be described. Figure 3 The positional relationship of each part in the subject 110 is shown as it is formed on the image sensor 30. Here, for simplicity of description, the optical path adjustment element 10-1 is not considered.

[0204] Figure 11 1 is a diagram schematically showing how a principal ray emitted from a certain point forms an image on the image sensor 30 in the absence of the dichroic prism 10. Figure 11 As shown, in the absence of the dichroic prism 10 , if the imaging optical system 20 sets a surface conjugate with the image sensor 30 as the subject surface 112 , an image on the subject surface 112 is formed on the image sensor 30 .

[0205] The imaging range of the image sensor 30 when viewed from the imaging optical system 20 is determined based on the focal length of the imaging optical system 20, the range where vignetting occurs, and the size of the image sensor 30. Hereinafter, it is assumed that the imaging range has a rectangular shape and is symmetrical with respect to the plane 24.

[0206] When no reflective mirror is disposed in the optical path, a position on the subject surface 112 that is conjugate with point a on the image sensor 30 is defined as point A, a position on the subject surface 112 that is conjugate with point b on the image sensor 30 is defined as point B, and a position on the subject surface 112 that is conjugate with point c on the image sensor 30 is defined as point C. Point b is located on the optical axis of the imaging optical system 20, and points a and c are located at the ends of the imaging range.

[0207] That is, the image sensor 30 acquires an image of the subject 110 in a range on the line segment AC on the subject surface 112. The lengths of the line segment ab and the line segment bc are equal, and the lengths of the line segment AB and the line segment BC are equal.

[0208] By arranging the reflector at the following position, the subject surface 112 is moved to the destination of the reflection by the reflector. This position is on the opposite side of the imaging optical system 20 from the image sensor 30. This position is closer to the imaging optical system 20 than the subject surface 112. This position is also on the optical path that the image sensor 30 can capture.

[0209] The subject 110 actually being imaged is located on the moved subject plane, but if the reflector is ignored, the subject 110 appears to be located on the subject plane 112. In this specification, this is referred to as the apparent subject position.

[0210] The following description will focus on an example in which the subject 110 has a planar shape and is located on a single plane perpendicular to the surface 10a2 of the dichroic prism 10 and perpendicular to the optical axis of the imaging optical system 20. For subjects 110 that are not located on this single plane, the imaging result can be calculated using elementary geometry, and therefore description thereof will be omitted.

[0211] <First Image>

[0212] The positional relationship between the apparent subject and the actual subject 110 will be described with respect to the first image. As will be described later, the entire range of the actual subject 110 is not imaged within the imaging range of the image sensor 30.

[0213] like Figure 5 As shown, when the light beam L from the subject 110 is incident from the outside on the surface 10a1 of the first right-angle prism 10a, the surface 10a1 and the surface 10a2 function as mirror surfaces that reflect the first light beam La separated from the light beam L. On the other hand, when the light beam L from the subject 110 is incident from the outside on the surface 10b1 of the second right-angle prism 10b, the surface 10b1 and the surface 10b2 function as mirror surfaces that reflect the first light beam La separated from the light beam L. However, since the light beam incident from the outside on the surface 10b1 is Figure 3The light shielding body 10-2 shown blocks the light, so that the latter first light beam La does not form an image on the image sensor 30. Therefore, regarding the first light beam La, only the first light beam La separated from the light beam L incident on the surface 10a1 is considered.

[0214] After being reflected by surface 10a2, the first light beam La is reflected again by surface 10a1 and enters the imaging optical system 20. By tracing the optical path of the first light beam La in reverse, the position of the actual subject 110 can be determined from the position of the apparent subject. In other words, after determining the position of the intermediate apparent subject resulting from reflection at surface 10a1, the position of the actual subject 110 resulting from reflection at surface 10a2 is determined.

[0215] Figure 12A 10a1 is a diagram for explaining the position of the intermediate apparent subject generated by the reflection of the first image. Figure 12A As shown, the plane containing surface 10a1 is plane 10a4. The intersection of plane 10a4 and plane 24 with the plane containing points A to C and the optical axis of imaging optical system 20 is point O. ∠BOA is γ. γ has a negative value. Since the lengths of line segments BA and BC are equal, ∠BOC is -γ. Here, angles are assumed to increase counterclockwise on paper with the optical axis of imaging optical system 20 as zero.

[0216] When the optical path is viewed from the image sensor 30 side, the first reflection surface is the surface 10a1. Figure 11 When at least a portion of the light beams at points a, b, and c shown in FIG. 1 are reflected by surface 10a1, the conjugate positions move to symmetrical positions with respect to surface 10a1. As a result, Figure 12A As shown, point A1, point B1, and point C1 are conjugate to point a, point b, and point c, respectively.

[0217] ∠BOA1 is 2α - γ, ∠BOB1 is 2α, and ∠BOC1 is 2α + γ. Line segments AO and A1O are equal in length. Similarly, line segments BO and B1O are equal in length. Line segments CO and C1O are equal in length. The positions of points A1, B1, and C1 are intermediate positions of the apparent subject with respect to the first light beam La.

[0218] Figure 12B 10a2 is a diagram for explaining the position of the actual subject caused by the reflection of the first image. Figure 12BAs shown, due to reflection from surface 10a2, points A1, B1, and C1 move to points A2, B2, and C2, respectively. Points A2, B2, and C2 are symmetrical with respect to points A1, B1, and C1, respectively, with respect to plane 24. Subject 110 located at points A2, B2, and C2 appears to be located at apparent points A1, B1, and C1. Points A2, B2, and C2 actually exist on subject surface 114.

[0219] Line segments A10 and A20 are equal in length. Similarly, line segments B10 and B20 are equal in length. Line segments C10 and C20 are equal in length. Therefore, line segments A0 and A20 are equal in length. Similarly, line segments B0 and B20 are equal in length. Line segments C0 and C20 are equal in length.

[0220] ∠BOA2 becomes γ-2α, ∠BOB2 becomes -2α, and ∠BOC2 becomes -γ-2α. That is, the positions of points A2, B2, and C2 are respectively the positions of points A, B, and C rotated by -2α around point O.

[0221] In summary, for the first light beam La, the subject 110 actually located at point A2, point B2, and point C2 appears to be located at apparent points A, B, and C.

[0222] After being reflected by the reflective surface, the subject 110 becomes a mirror-inverted image at each reflection. Therefore, an image that has been reflected an odd number of times becomes a mirror-inverted image relative to an image that has not been reflected. An image that has been reflected an even number of times becomes a mirror-inverted image relative to an image that has not been reflected.

[0223] Mathematically, two mirror inversions are equivalent to one rotation. The first light beam La is reflected twice by surfaces 10a1 and 10a2 of the dichroic prism 10. Therefore, the first image formed on the image sensor 30 is not mirror-inverted relative to the unreflected image. The actual position of the imaged subject 110 is at a position rotated -2α from the apparent subject position, with point O as the rotation axis.

[0224] <Second Image>

[0225] The positional relationship between the apparent subject of the second image and the actual subject 110 will be described. Similar to the first light beam La, the light beam incident from the surface 10b1 side is blocked. Therefore, for the second light beam Lb, only the optical path of the second light beam Lb separated from the light beam L incident on the surface 10a1 of the first right-angle prism 10a will be considered.

[0226] Figure 1310b1 is a diagram for explaining the position of the actual subject 110 in the second image due to the reflection of the surface 10b1. When the optical path is viewed from the image sensor 30 side, the only reflecting surface is the surface 10b1. Figure 13 As shown, the plane containing plane 10b1 is plane 10b4. Points A3, B3, and C3 are symmetrical to points A, B, and C, respectively, with respect to plane 10b4. Subject 110 located at points A3, B3, and C3 appears to be located at apparent points A, B, and C. Points A3, B3, and C3 exist on actual subject plane 116.

[0227] ∠BOA3 becomes -γ-2β, ∠BOB3 becomes -2β, and ∠BOC3 becomes γ-2β. When α = β, ∠BOA3 becomes -γ-2α, ∠BOB3 becomes -2α, and ∠BOC3 becomes γ-2α. Line segment AO and line segment A3O are equal in length. Similarly, line segment BO and line segment B3O are equal in length. Line segment CO and line segment C3O are equal in length.

[0228] In the case where the refractive power of the imaging optical system 20 is equal in the first wavelength range and the second wavelength range, as shown in FIG. Figure 13 The subject surface 116 shown is Figure 12B The subject plane 114 shown is identical. That is, point A3 is identical to point C2, point B3 is identical to point B2, and point C3 is identical to point A2.

[0229] The apparent objects in the first wavelength range and the second wavelength range observed from the actual object 110 are in a mirror-inverted relationship with each other. In other words, the first image and the second image formed on the image sensor 30 are in a mirror-inverted relationship with each other.

[0230] This is because the first light beam La is reflected twice by surfaces 10a1 and 10a2, an even number of times, while the second light beam Lb is reflected once by surface 10b1, an odd number of times. In other words, when one of the two light beams is reflected an even number of times and the other an odd number of times, the two images are mirror-inverted.

[0231] In the above example, the optical paths of the first light beam La and the second light beam Lb are described separately. In reality, the first light beam La and the second light beam Lb form images simultaneously. As a result, the first image and the second image are simultaneously acquired by the image sensor 30. This is because the optical path lengths of the first light beam La and the second light beam Lb are equal.

[0232] [Range in which the First Light Beam La and the Second Light Beam Lb are Imaged]

[0233] The correspondence between the subject 110 and the first and second images on the image sensor 30 is as described above. In practice, the first and second images formed on the image sensor 30 differ depending on, for example, the relative positions of the dichroic prism 10, the imaging optical system 20, the image sensor 30, the optical path adjustment element 10-1, and the light shielding member 10-2. The first and second images also differ depending on the size of their components, the focal length, and the aperture settings.

[0234] Light emitted in a certain direction from a certain point within the subject 110 passes through the optical path adjustment element 10-1, the dichroic prism 10, and the imaging optical system 20, and reaches the imaging range of the image sensor 30. As a result, an image of the certain point within the subject 110 is acquired by the image sensor 30. If light emitted in any direction from a certain part within the subject does not reach the imaging range of the image sensor 30, no image is formed of that part within the subject 110.

[0235] The following describes the range of the subject 110 actually imaged on the image sensor 30. The imaging device 100 is configured so that only light beams that pass through the dichroic prism 10 and the imaging optical system 20 reach the imaging range on the image sensor 30. This configuration can be achieved by appropriately adjusting the size of the dichroic prism 10, the positional relationship between the dichroic prism 10 and the imaging optical system 20, the focal length of the imaging optical system 20, and the size and position of the light shield 10-2. The following description assumes this configuration. That is, there are no light beams that enter the imaging optical system 20 without passing through the dichroic prism 10.

[0236] First, the range in which the first light beam La actually forms an image on the image sensor 30 will be described. Figure 14 1 is a diagram schematically showing a state in which the first light beam La travels within the first right-angle prism 10a. The light beam L from the subject 110 includes the first light beam La as a part thereof. Figure 14 As shown, the first light beam La passes through the surface 10a1 of the first right-angle prism 10a from the outside, is reflected by the surfaces 10a2 and 10a1 in that order, and passes through the surface 10a3. Therefore, the light beam that does not pass through the surfaces 10a1 to 10a3 and is not reflected by the surfaces 10a1 to 10a3 does not form an image on the image sensor 30.

[0237] As the first light beam La travels along the optical path from the imaging optical system 20 side, it passes through surface 10a3, is reflected by surfaces 10a1 and 10a2 in that order, and then passes through surface 10a1. Due to the reflection from surface 10a1, first right-angle prism 10a appears as prism 11a. Prism 11a is symmetrical to first right-angle prism 10a with respect to the plane including surface 10a1. Surface 10a2 appears as the corresponding surface 11a2 of prism 11a.

[0238] Furthermore, due to reflection at surface 10a2, prism 11a appears as prism 13a. Prism 13a is symmetrical to prism 11a with respect to a plane including surface 11a2. Surface 10a1, which is a passing surface, appears as surface 13a1 corresponding to prism 13a.

[0239] Therefore, the first light beam La corresponds to an apparent light beam Lc that passes from the apparent object through the thick plate composed of the actual first right-angle prism 10a and the two apparent prisms 11a and 13a. Figure 14 The dashed arrows shown represent the light beam Lc. If the actual first light beam La passing through the first right-angle prism 10a exists, the apparent light beam Lc can be considered. Conversely, if the apparent light beam Lc is not considered, the actual first light beam La does not exist.

[0240] The existence of a light beam that passes through the surface 13a1 of the apparent prism 13a and the surface 10a3 of the first right-angle prism 10a is a necessary condition for imaging the first light beam La.

[0241] Figure 15A and Figure 15B 1 is a diagram schematically showing how light emitted from a certain point of the first light beam La is imaged on the image sensor 30 when apparent prisms 11 a and 13 a are present in addition to the dichroic prism 10 .

[0242] like Figure 15A As shown, line segment AB is located on the side of surface 13a1 and surface 10a3 through which the first light beam La should pass, relative to plane 24. Therefore, by appropriately designing the size and position of first right-angle prism 10a, it is possible to image the points on line segment AB on the apparent object within the imaging range of image sensor 30.

[0243] In contrast, line segment BC is located on the opposite side of surface 13a1 and surface 10a3 relative to plane 24. Therefore, regardless of the size and position of first right-angle prism 10a, the principal ray emitted from a point on line segment BC does not pass through surface 13a1 or surface 10a3. However, even for light emitted from a point on line segment BC, light that passes through an optical path other than the principal ray may form an image within the imaging range of image sensor 30.

[0244] like Figure 15B As shown, the light rays that have passed through the surface 13a1 and the surface 10a3 are imaged by the imaging optical system 20 within the imaging range on the image sensor 30, and the apparent position of the boundary of the imaging range is set to F. The position where the light rays that appear to have been emitted from point F are imaged on the image sensor 30 is set to point f.

[0245] A point on the line segment BF on the apparent subject is imaged by the imaging optical system 20 on the line segment bf in the imaging range of the image sensor 30. A point on the line segment FC on the apparent subject is not imaged in the imaging range of the image sensor 30 because the principal ray emitted from this point does not pass through the imaging optical system 20.

[0246] When the dichroic prism 10 is not provided, the range of line segment AC on the apparent subject forms an image within the imaging range of the image sensor 30. In contrast, when the dichroic prism 10 is actually provided, for the first light beam La, only the range of line segment AB and line segment BF on the apparent subject forms an image within the imaging range of the image sensor 30. The range of line segment FC on the apparent subject does not form an image because the light does not reach the image sensor 30.

[0247] Next, the range in which the second light beam Lb actually forms an image on the image sensor 30 will be described. Figure 16 1 is a diagram schematically showing a state in which the second light beam Lb travels within the second right-angle prism 10b. The light beam L from the subject 110 includes the second light beam Lb as a part thereof. Figure 16 As shown, second light beam Lb passes from the outside through faces 10a1, 10a2, and 10b2 of first right-angle prism 10a, is reflected by face 10b1 of second right-angle prism 10b, and passes through face 10b3. Therefore, light beams that neither pass through faces 10a1, 10a2, and faces 10b1 to 10b3 nor are reflected by them are not formed on image sensor 30.

[0248] If traveling along the optical path from the imaging optical system 20 side, the second light beam Lb passes through the surface 10b3, is reflected by the surface 10b1, and sequentially passes through the surface 10b2, the surface 10a2, and the surface 10a1.

[0249] Due to the reflection from surface 10b1, second rectangular prism 10b appears as prism 11b, while first rectangular prism 10a appears as prism 15a. Prism 11b is symmetrical to second rectangular prism 10b about the plane including surface 10b1. Prism 15a is symmetrical to first rectangular prism 10a about the plane including surface 10b1. Surface 10a1, acting as a passing surface, appears as corresponding surface 15a1 of prism 15a.

[0250] Therefore, the second light beam Lb corresponds to an apparent light beam Ld that passes from the apparent object through the thick plate formed by the actual second right-angle prism 10b and the two apparent prisms 11b and 15a. Figure 16The double-dashed arrow indicates the apparent light beam Ld. If the actual second light beam Lb passing through the second right-angle prism 10b exists, the apparent light beam Ld can be considered. Conversely, if the apparent light beam Ld is not considered, the actual second light beam Lb does not exist.

[0251] The existence of a light beam that passes through the surface 15a1 of the apparent prism 15a and the surface 10b3 of the second right-angle prism 10b is a necessary condition for forming an image of the second light beam Lb.

[0252] Figure 17A and Figure 17B 15 a is a diagram schematically showing how light emitted from a certain point forms an image on the image sensor 30 when, in addition to the dichroic prism 10 , apparent prisms 11 b and 15 a are present regarding the second light beam Lb.

[0253] like Figure 17A As shown, line segment BC is located on one side of surface 15a1 and surface 10b3, through which second light beam Lb is to pass, with reference to plane 24. Therefore, by appropriately designing the size and position of first and second right-angle prisms 10a, 10b, it is possible to image a point on line segment BC on the apparent object within the imaging range of image sensor 30.

[0254] In contrast, line segment AB is located on the side opposite to surface 15a1 and surface 10b3 relative to plane 24. Therefore, regardless of the size and position of first and second right-angle prisms 10a, 10b, the principal ray emitted from a point on line segment AB does not pass through surface 15a1 or surface 10b3. However, even for light emitted from a point on line segment AB, light that follows an optical path other than the principal ray may form an image within the imaging range of image sensor 30.

[0255] like Figure 17B As shown, the light rays that have passed through the surface 15a1 and the surface 10b3 are imaged by the imaging optical system 20 within the imaging range on the image sensor 30, and the apparent position constituting the boundary of the imaging range is defined as point G. The position where the light rays that appear to have been emitted from point G are imaged on the image sensor 30 is defined as point g.

[0256] A point on the line segment GB on the apparent subject is formed on a line segment gb on the imaging range of the image sensor 30 by the imaging optical system 20. A point on the line segment AG on the apparent subject is not formed in the imaging range of the image sensor 30 because the principal ray emitted from this point does not pass through the imaging optical system 20.

[0257] When the dichroic prism 10 is not provided, the range of line segment AC on the subject is imaged within the imaging range of the image sensor 30. In contrast, when the dichroic prism 10 is actually provided, for the second light beam Lb, only the range of line segment BC and line segment GB on the apparent subject is imaged within the imaging range of the image sensor 30. Within the range of line segment AG on the apparent subject, no light reaches the image sensor 30, and therefore no image is formed.

[0258] Figure 18 Schematically shows the range in which the first light beam La and the second light beam Lb are imaged on the image sensor 30. Figure 18 As shown, the range 30a of line segment af on image sensor 30 forms a first image, and the range 30b of line segment gc forms a second image. In this case, the range 32a of line segment ag forms only the first image, the range 32b of line segment fc forms only the second image, and the range 32c of line segment gf forms the first and second images in a superimposed manner.

[0259] [Positional relationship between apparent subject and actual subject]

[0260] Figure 19 is a diagram for explaining the positional relationship between the apparent subject and the actual subject. Figure 19 As shown, for the first image, points A, B, and F of the apparent subject correspond to points A2, B2, and F2 of the actual subject, respectively. Similarly, for the second image, points B, C, and G of the apparent subject correspond to points B3, C3, and G3 of the actual subject, respectively. As previously mentioned, points A2 and C3 are identical, and points B2 and B3 are identical. Similarly, points F2 and G3 are identical.

[0261] [Positional relationship between the first image and the second image]

[0262] Figure 20 Schematic diagram of an example of a first image and a second image formed on the image sensor 30 . Figure 3 The subject 110 shown is referenced Figure 45 Description.

[0263] The imaging range 36 of the image sensor 30 exists within the image circle 34 formed on the image sensor 30 by the imaging optical system 20. A first image 110a and a second image 110b are formed within the imaging range 36. The first image 110a and the second image 110b are mirror-symmetrical with respect to the plane 24. The first image 110a and the second image 110b are formed on Figure 18 The range 32a and the range 32b are shown so as not to overlap with each other. The range 32a corresponds to Figure 19 The range of the line segment A2-F2 shown. The range 32b corresponds to Figure 19 The range of line segment G3-C3 is shown.

[0264] The first light beam La and the second light beam Lb, which are emitted from a certain point in the subject 110 and formed on the image sensor 30, travel along the same optical path until reaching the surface 10a2. After reaching the surface 10a2, the first light beam La and the second light beam Lb travel along different optical paths that are symmetrical with respect to the plane 24. These different optical paths pass through the dichroic prism 10 and the imaging optical system 20.

[0265] In the first light beam La and the second light beam Lb, which travel along such symmetrical optical paths, the degree of vignetting caused by the dichroic prism 10 and the imaging optical system 20 is the same. The degree of edge vignetting caused by the dichroic prism 10 and the imaging optical system 20 is also the same. Therefore, in the first image 110a and the second image 110b, the ratio of light loss caused by vignetting and edge vignetting for light emitted from the same point within the subject 110 and having a wavelength included in the first wavelength range or the second wavelength range is the same. By calculating these intensity ratios, the effects of vignetting and edge vignetting can be ignored.

[0266] Both first image 110a and second image 110b may be distorted due to curvature aberration. However, curvature aberration occurs symmetrically with respect to plane 24. Regardless of the form of curvature aberration, the corresponding positions within first image 110a and second image 110b are symmetrical with respect to plane 24. Therefore, it is extremely easy to determine the corresponding positions.

[0267] like Figure 20 As shown, point 110b1 within the second image 110b corresponds to point 110a1 within the first image 110a. Similarly, point 110b2 within the second image 110b corresponds to point 110a2 within the first image 110a. Point 110b3 within the second image 110b corresponds to point 110a3 within the first image 110a. Point 110b4 within the second image 110b corresponds to point 110a4 within the first image 110a. Points 110b1 to 110b4 within the second image 110b are symmetrical to points 110a1 to 110a4 within the first image 110a, respectively, with plane 24 as a reference. For each point corresponding to the same position within the subject 110, the distance from the reference position 38 is the same. The reference position 38 is the position where the optical axis of the imaging optical system 20 passes through the imaging range 36.

[0268] As described above, the first image 110a and the second image 110b are mirror-symmetrical with respect to the plane 24. The ratio of the radiation intensities at corresponding points within the first image 110a and the second image 110b is calculated, and the sensitivity of the image sensor 30 is corrected as necessary. As a result, the ratio of the radiation intensities within the first wavelength range and the second wavelength range from corresponding points within the subject 110 can be accurately determined.

[0269] [Measures for reducing the range of overlap between the first image and the second image]

[0270] Figure 19 The range of the line segment FG shown corresponds to the range of overlap between the first image 110a and the second image 110b on the image sensor 30. If a mathematical separation operation is performed, it is possible to obtain the first image 110a and the second image 110b separately. However, it is practical to obtain the first image 110a and the second image 110b separately without performing such an operation.

[0271] A first method for narrowing the range where the first image 110a and the second image 110b overlap will be described. The first method is to use a light-blocking body. Figure 21 1 is a diagram schematically showing how light emitted from a certain point forms an image on the image sensor 30 when, in addition to the dichroic prism 10, there are apparent prisms 11a, 13a, 15a, and 11b for the first light beam La and the second light beam Lb. Figure 21 As shown, light rays passing through point Z, surface 13a1, and surface 10a3 are imaged by imaging optical system 20 within the imaging range of image sensor 30, with the apparent position of this image being referred to as point F'. Similarly, light rays passing through point Z, surface 15a1, and surface 10b3 are imaged by imaging optical system 20 within the imaging range of image sensor 30, with the apparent position of this image being referred to as point G'. Point Z is located on line segment OB.

[0272] like Figure 21 As shown, the apparent light shield indicated by the thick line is located between point O and point Z. The light that crosses the light shield is not formed on the image sensor 30. Figure 19 The light emitted from the line segment AB shown and formed on the image sensor 30 does not cross the apparent light-blocking body. Therefore, the apparent light-blocking body does not affect the range formed on the image sensor 30 by the main light having a wavelength included in the first wavelength range.

[0273] In contrast, the apparent light-blocking body blocks light rays having wavelengths included in the first wavelength range that are emitted from points on the apparent line segment F-F' and imaged on the image sensor 30. Similarly, the apparent light-blocking body blocks light rays having wavelengths included in the second wavelength range that are emitted from points on the apparent line segment G-G' and imaged on the image sensor 30.

[0274] The point on the image sensor 30 that is conjugate to the apparent position F' is f', and the point on the image sensor 30 that is conjugate to the apparent position G' is g'. Point f' is located at Figure 18 Point g' is located between points b and f shown in the figure. Figure 18 In this case, the range where the first image 110a and the second image 110b overlap on the image sensor 30 is the range of the line segment f'-g'. Therefore, the range where the first image 110a and the second image 110b overlap is narrowed.

[0275] Figure 22 1 is a diagram schematically showing the positional relationship between the apparent light shielding body, the actual light shielding body and the dichroic prism 10. If the actual point corresponding to the apparent point Z is set as Z', then Figure 22 As shown, the actual light shielding body 10-3 is located between point O and point Z'. Point Z' is located Figure 19 On the line segment O-B2 or line segment O-B3 shown.

[0276] Figure 23 Schematically shows the range in which the first light beam La and the second light beam Lb block the optical path of both of them forming an image on the image sensor 30. Figure 23 The range within the shaded triangle OB2C2 can reduce the overlapping range of the first image 110 a and the second image 110 b on the image sensor 30 .

[0277] In such Figure 3 In the case where the optical path adjusting element 10 - 1 is configured as shown, the light shielding body 10 - 3 is arranged between the optical path adjusting element 10 - 1 and the object 110 at a position that blocks the optical paths of both the first light beam La and the second light beam Lb forming images on the image sensor 30 .

[0278] Next, a second method for narrowing the overlap range between the first image 110a and the second image 110b will be described. The second method uses a filter array. Figure 24 3 is a diagram schematically showing an example of the filter array 31. Figure 24 As shown, the filter array 31 is arranged between the imaging optical system 20 and the image sensor 30. The filter array 31 includes a first filter portion 31a and a second filter portion 31b. The first filter portion 31a transmits the first light beam La and blocks the second light beam Lb by reflection or absorption. The second filter portion 31b transmits the second light beam Lb and blocks the first light beam La by reflection or absorption.

[0279] The direction perpendicular to and away from the imaging plane of the image sensor 30 is defined as upward. The first filter portion 31a is positioned above the first region corresponding to line segment ab on the image sensor 30. The second filter portion 31b is positioned above the second region corresponding to line segment bc on the image sensor 30. Therefore, the image sensor 30 can acquire a first image 110a in the first region and a second image 110b in the second region. When the filter array 31 is positioned directly above the image sensor 30, all of the multiple photoelectric conversion elements included in the image sensor 30 receive light having a wavelength within either the first wavelength range or the second wavelength range.

[0280] When the filter array 31 is located away from the image sensor 30, due to the influence of light obliquely passing through the first filter portion 31a or the second filter portion 31b, some of the multiple photoelectric conversion elements included in the image sensor 30 may receive both light having wavelengths within the first wavelength range and light having wavelengths within the second wavelength range. The number of these photoelectric conversion elements can be reduced, for example, by limiting the distance between the filter array 31 and the image sensor 30 to the size of the image sensor 30. Alternatively, the telecentricity of the imaging optical system 20 can be increased.

[0281] In addition, the filter array 31 includes a single first filter portion 31a and a single second filter portion 31b. Therefore, compared to a structure in which multiple filters are formed to correspond to multiple photoelectric conversion elements, the filter array 31 is easier to manufacture. In a structure in which multiple filters are formed to correspond to multiple photoelectric conversion elements, the positional relationship between each photoelectric conversion element and its corresponding filter is designed so that the positional deviation between the two is sufficiently small compared to the size of each photoelectric conversion element. In contrast, the positional relationship between the first region and the first filter portion 31a does not need to be designed very strictly, as the impact of the positional misalignment between the two is very small. The same applies to the positional relationship between the second region and the second filter portion 31b.

[0282] [Supplementary Explanation of Optical Path Adjustment Element 10-1]

[0283] like Figure 19 As shown, unlike the apparent subject, the actual subject 110 is not located on an extension of the optical axis of the imaging optical system 20. Therefore, the orientation of the imaging optical system 20 differs significantly when the dichroic prism 10 is installed and when it is not. This problem can be solved by placing an optical path adjustment element 10-1 between the subject 110 and the dichroic prism 10. The optical path adjustment element 10-1 can orient the imaging optical system 20 in a natural direction.

[0284] The natural direction of the imaging optical system 20 is, for example, a direction in which the first image 110a and the second image 110b are formed on the image sensor 30 without overlapping each other, and a direction in which the central axis of the region between the first image 110a and the second image 110b intersects the subject 110. When this direction coincides with the optical axis of the imaging optical system 20, the subject 110 is located in the optical axis direction of the imaging optical system 20 and faces the image sensor 30. In this case, the first image 110a and the second image 110b of the subject 110 located in this direction can be formed so as not to overlap each other on the image sensor 30.

[0285] When the apparent object is within the range of the line segment AB, the optical path adjustment element 10 - 1 may be designed, for example, so that the light beam from the midpoint of the line segment AB is parallel to the optical axis of the imaging optical system 20 .

[0286] The imaging device 100 may further include an adjustment device for adjusting the position and orientation of the optical path adjustment element 10-1 and the dichroic prism 10. Alternatively, when the optical path adjustment element 10-1 is composed of a plurality of mirrors or prisms, the imaging device 100 may further include an adjustment device for adjusting the position and orientation of the plurality of components included in the optical path adjustment element 10-1.

[0287] Lens replacement and zoom lens operation may change the focal length of the imaging optical system 20, potentially changing the range of the subject image on the image sensor 30. Consequently, the center of the imaging range on the imaging plane of the image sensor 30 may shift. Even in such cases, the optical axis of the imaging optical system 20 can be adjusted using the aforementioned adjustment tool so that it passes through the center in a direction perpendicular to the imaging plane of the image sensor 30.

[0288] [Configuration of the Dichroic Prism 10]

[0289] The size of the image sensor 30 is typically several millimeters to several tens of millimeters. Therefore, the area of ​​the subject 110 is often larger than the imaging surface of the image sensor 30. Consequently, on the image sensor 30, more specifically, the first image and the second image formed on the imaging surface are each smaller than the subject 110. When imaging an area of ​​the subject 110 that is larger than the imaging surface of the image sensor 30, the divergence angle of the light beam formed by the imaging optical system 20 is smaller on the subject 110 side and larger on the image sensor 30 side.

[0290] In the imaging device 100, the dichroic prism 10 is arranged on the subject 110 side with respect to the imaging optical system 20. As a result, compared with a configuration in which the dichroic prism 10 is arranged on the image sensor 30 side, aberrations generated when a light beam having a divergence angle passes through the dichroic prism 10 can be reduced.

[0291] [Connection between Optical Component 10A and Lens Device 20A]

[0292] In the imaging device 100, a commonly used commercially available lens assembly and camera can be used as the lens assembly 20A and the camera 30A. Hereinafter, an example of connecting the optical component 10A and the lens assembly 20A, which can be easily used with a commercially available lens assembly and camera, will be described. The optical component 10A is attachable to and detachable from the lens assembly 20A and can be connected to a commercially available lens assembly.

[0293] Figure 25A This figure schematically shows an example of connecting an optical component 10A and a lens device 20A. The optical component 10A includes a dichroic prism 10, an optical path adjustment element 10-1, and a frame 12 that accommodates them. The frame 12 includes side walls 12a and a light-transmitting window 12b. The side walls 12a surround and support the dichroic prism 10 and the optical path adjustment element 10-1. The side walls 12a have light-shielding properties and can serve as Figure 3 The light shield 10-2 shown functions as shown. The light transmission window 12b transmits the light beam L from the subject 110. The light transmission window 12b is located near the front end of the side wall 12a. The light transmission window 12b may be, for example, an optical filter that transmits light within the first wavelength range and the second wavelength range, and blocks or attenuates light beams having wavelengths outside the first wavelength range or the second wavelength range. Alternatively, the light transmission window 12b may be omitted.

[0294] The housing 12 further includes a connection structure 12c located near the rear end of the side wall 12a. The connection structure 12c is a structure for connecting the optical component 10A and the lens device 20A. The connection structure 12c may be, for example, an external thread.

[0295] The lens device 20A includes an imaging optical system 20 and a lens frame 22 that houses the imaging optical system 20. The lens frame 22 may include a sidewall 22a, a light-transmitting window 22b1, and a light-transmitting window 22b2. The sidewall 22a surrounds and supports the imaging optical system 20. The light-transmitting window 22b1 and the light-transmitting window 22b2 transmit the first light beam La and the second light beam Lb. The light-transmitting window 22b1 is located near the front end of the sidewall 22a, and the light-transmitting window 22b2 is located near the rear end of the sidewall 22a. The light-transmitting windows 22b1 and 22b2 may be formed of a light-transmitting member such as glass, or may be simply hollow.

[0296] The lens housing 22 further includes a connecting structure 22c1 located near the front end of the side wall 22a, and a connecting structure 22c2 located near the rear end of the side wall 22a. The connecting structure 22c1 is used to attach a filter to the camera lens. The connecting structure 22c2 is used to connect the lens unit 20A and the camera 30A. The connecting structures 22c1 and 22c2 may be, for example, internal threads.

[0297] The optical component 10A and the lens unit 20A can be connected by the connection structure 12c of the optical component 10A and the connection structure 22c1 of the lens unit 20A. The central axis of the connection structure 12c in the optical component 10A is located on the optical axis of the imaging optical system 20. The dichroic prism 10 can be fixed in the housing 12 such that the central axis is included in the surface 10a2 of the dichroic prism 10. In this case, by connecting the optical component 10A and the lens unit 20A, the plane including the surface 10a2 can include the optical axis of the imaging optical system 20.

[0298] Figure 25B 10A is a diagram schematically showing another example of connecting the optical component 10A and the lens device 20A. Figure 3 The camera device 100 shown may further include Figure 25B The adjustment tool 40 is shown. The adjustment tool 40 adjusts the positional relationship between the dichroic prism 10 and the imaging optical system 20. The positional relationship between the two can be, for example, a relative angle between them. The optical component 10A and the imaging optical system 20 are connected via the adjustment tool 40. The connection structure 12c of the optical component 10A can be, for example, an internal thread. For example, the relative angle can be adjusted by adjusting the screwing depth of the internal thread.

[0299] The adjustment tool 40 has a roughly cylindrical shape. The adjustment tool 40 may include, for example, a full thread 40a and a fastening ring 40b. The front end of the full thread 40a is connected to the internal thread near the rear end of the optical component 10A, and the rear end of the full thread 40a is connected to the internal thread near the front end of the lens device 20A. After the front end of the full thread 40a is screwed into the position of the internal thread near the rear end of the optical component 10A, the optical component 10A and the lens device 20A are fixed by the fastening ring 40b. As a result, the positional relationship between the dichroic prism 10 and the imaging optical system 20 can be adjusted to a desired positional relationship, more specifically, to a desired angular relationship.

[0300] Figure 25C 1 is a diagram schematically showing another example of connecting the optical component 10A and the lens device 20A. Figure 25C As shown, the connection structure 12c of the optical component 10A and the connection structure 22c1 of the lens device 20A may have, for example, a flange structure similar to an ISO-KF flange. Figure 3The camera device 100 shown may further include Figure 25C The fixture 42 shown in FIG. Fixture 42 may include, for example, a centering ring 42a and a clamping ring 42b. Centering ring 42a facilitates alignment of the flange-structured connection structure 12c of optical component 10A and the connection structure 22c1 of lens unit 20A. Clamping ring 42b enables connection of the flange-structured connection structure 12c of optical component 10A and the connection structure 22c1 of lens unit 20A. As a result, the positional relationship between dichroic prism 10 and imaging optical system 20 becomes a desired positional relationship, more specifically, a desired angular relationship.

[0301] As described above, by connecting the optical component 10A and the lens device 20A, the dichroic prism 10 and the imaging optical system 20 can be fixed at a desired angular relationship. In addition, by connecting the lens device 20A and the camera 30A, the imaging optical system 20 and the image sensor 30 can be fixed at a desired angular relationship. Therefore, by connecting the optical component 10A, the lens device 20A and the camera 30A, the dichroic prism 10 and the image sensor 30 can be fixed at a desired angular relationship. As a result, as Figure 20 As shown, the plane 24 can be parallel to the short side of the rectangular imaging range and pass through the midpoint of the long side.

[0302] When not in use Figures 25A to 25C In the case of the components shown, the phase of the screws provided in the internal threads of the commercially available lens unit varies from lens unit to lens unit, making it difficult to fix the dichroic prism 10 and the image sensor 30 at a desired angular relationship.

[0303] As described above, according to the imaging device 100 of Embodiment 1, the first image 110a and the second image 110b are mirror-symmetrical to each other. This relationship makes it easy to determine corresponding positions within the two images. Because the first light beam La and the second light beam Lb travel symmetrically with respect to the plane 24 containing the optical axis of the imaging optical system 20, curvature aberration and edge vignetting occur approximately equally in the first wavelength range and the second wavelength range. Therefore, the intensity ratio at corresponding positions within the first image 110a and the second image 110b is largely unaffected by curvature aberration and edge vignetting. Thus, the first image 110a and the second image 110b are suitable for evaluating the subject 110 using methods such as two-color thermography and fluorescence imaging.

[0304] Furthermore, according to the imaging apparatus 100 of Embodiment 1, commercially available lens devices and cameras can be used as the lens device 20A and the camera 30A, respectively. In the imaging apparatus 100, the optical component 10A is added to such lens device 20A and camera 30A. Therefore, the imaging apparatus 100 has a simple structure.

[0305] Therefore, the imaging device 100 of the first embodiment can obtain two images in different wavelength ranges suitable for evaluating the subject 110 with a simple configuration. Furthermore, the imaging device 100 of the first embodiment can dispose the optical path adjustment element 10-1 between the subject 110 and the dichroic prism 10. With the optical path adjustment element 10-1, the subject 110 is positioned in the optical axis direction of the imaging optical system 20, and an image of the subject 110 can be captured in a natural orientation relative to the image sensor 30.

[0306] (Modification of the imaging device 100 according to the first embodiment)

[0307] Hereinafter, Modifications 1 and 2 of the imaging device 100 according to the first embodiment will be described. Figure 1 The first sub-component 10A1 and the second sub-component 10A2 shown are not limited to Figure 3 The dichroic prism 10 and the optical path adjustment element 10-1 are shown.

[0308] [Variation 1]

[0309] Figure 26 This is a diagram schematically showing a specific configuration of an optical component 10A in Modification 1 of the imaging device 100 according to the first embodiment. Figure 26 The optical component 10A shown includes an optical element group 14 and an optical path adjustment element 11 - 1 . Figure 26 The optical component 10A shown may also include Figure 3 The light shielding body 10-2 and the frame 12 are shown. The optical element group 14 includes a dichroic mirror 16 having a dichroic surface 16a, two mirrors 17a and 17b, and a prism 18. The optical path adjustment element 11-1 is a half pentaprism. The optical element group 14 corresponds to Figure 1 The first subcomponent 10A1 shown, the optical path adjustment element 11-1 corresponds to Figure 1 In this specification, the optical element group 14 is also referred to as the "first optical element" and the optical path adjustment element 11-1 is also referred to as the "second optical element".

[0310] Figure 27 Schematically shows the optical element group 14 in Modification 1. Figure 27 As shown in FIG. 27 , dichroic mirror 16 is a flat optical element having a dichroic surface 16a. Dichroic surface 16a is disposed within plane 24. Two mirrors 17a and 17b are symmetrically disposed with respect to plane 24. Mirror 17a forms an angle ε with plane 24. Mirror 17b forms the same angle with plane 24. However, mirrors 17a and 17b are tilted in opposite directions.

[0311] Triangular prism 18 has a triangular prism shape, with surface 18a1, surface 18a2, and surface 18a3 as side faces. Surface 18a1 and surface 18a2 are symmetrically arranged with respect to plane 24. Surface 18a1 and plane 24 form an angle δ. The same applies to the angle formed between surface 18a2 and plane 24. However, surface 18a1 and surface 18a2 are inclined in opposite directions.

[0312] Figure 28 : is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the optical element group 14 in Modification 1. Figure 28 As shown, the dichroic surface 16a of the dichroic mirror 16 reflects the first beam La of the light beam L incident in the direction θ toward the direction -θ and transmits the second beam Lb toward the direction θ. In this way, the dichroic surface 16a separates the light beam L into the first beam La and the second beam Lb.

[0313] Mirror 17a reflects the first beam La and makes it incident on prism 18, while mirror 17b reflects the second beam Lb and makes it incident on prism 18. The first beam La reflected by mirror 17a travels in a direction of θ-2ε, while the second beam Lb reflected by mirror 17b travels in a direction of -θ+2ε.

[0314] Prism 18 emits the incident first light beam La and second light beam Lb out of prism 18. First light beam La enters surface 18a1, is totally reflected by surface 18a2, and is emitted from surface 18a3 out of prism 18. The direction of the first light beam La emitted to the outside is -θ + 2ε - 2δ. Second light beam Lb enters surface 18a2, is totally reflected by surface 18a1, and is emitted from surface 18a3 out of prism 18. The direction of the second light beam Lb emitted to the outside is θ - 2ε + 2δ. The first light beam La and the second light beam Lb are symmetrical about plane 24.

[0315] As described above, the optical element group 14 separates the light beam L into the first light beam La and the second light beam Lb by the dichroic surface 16a. The optical element group 14 also converts the directions of the first light beam La and the second light beam Lb by the two mirrors 17a and 17b and the prism 18 and emits them.

[0316] Assume that light beam L enters dichroic surface 16a in direction θ = -π / 4. When angle ε is π / 24, first light beam La enters surface 18a1 in direction -π / 3, and second light beam Lb enters surface 18a2 in direction π / 3. Furthermore, when angle δ is approximately π / 6, the directions of travel of first light beam La and second light beam Lb emitted to the outside are approximately zero.

[0317] Figure 29Schematically shows the optical path adjustment element 11-1 in Modification 1. Figure 29 As shown, the optical path adjusting element 11-1 has a surface 11-1a1, a surface 11-1a2, and a surface 11-1a3. The optical path adjusting element 11-1 also has a surface 11-1a4 and a surface 11-1a5. The surfaces 11-1a4 and 11-1a5 are surfaces through which the light beam L does not pass and can be omitted.

[0318] The surface 11-1a1 and the surface 11-1a2 form an angle ρ. The surface 11-1a1 and the surface 11-1a3 form an angle μ. The surface 11-1a3 may have a metal film or a dielectric multilayer film to achieve high light reflectivity.

[0319] Figure 30 Schematically shows an example of the path of the light beam L in the optical path adjustment element 11-1 in Modification 1. Figure 30 In the example shown, it is assumed that the surface 11-1a1 is perpendicular to Figure 27 The plane 24 shown. In the optical path adjusting element 11-1, the light beam L is reflected twice internally. Therefore, as long as the light beam L passes through the incident surface and the reflective surface in the order described below, the direction of the optical path adjusting element 11-1 will not affect the change in the path of the light beam L.

[0320] The light beam L enters the surface 11-1a1. The direction of travel of the light beam L entering the surface 11-1a1 is The light beam L incident on the surface 11-1a1 is totally reflected by the surface 11-1a2. The direction of the light beam L totally reflected by the surface 11-1a2 is The light beam L totally reflected by the surface 11-1a2 is totally reflected by the surface 11-1a3 and emitted from the surface 11-1a2 to the outside. The direction of the light beam L emitted from the surface 11-1a2 to the outside is However, the fact that the angle is the same regardless of the difference of ±2π is used.

[0321] When ρ is approximately π / 4 and μ is approximately 5π / 8, 2ρ+2μ is approximately -π / 4. Therefore, the optical path adjusting element 11-1 has a function of changing the traveling direction of the light beam L by approximately -π / 4.

[0322] Figure 31 1 is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the optical component 10A in Modification 1. Figure 31 As shown, along the direction The light beam L incident on the optical path adjusting element 11-1 is reflected inside and then emitted to the outside. The direction of the light beam L emitted from the optical path adjusting element 11-1 to the outside is

[0323] The light beam L emitted from the optical path adjustment element 11-1 is separated by the dichroic mirror 16 into a first light beam La and a second light beam Lb. The first light beam La is reflected by the mirror 17a and the surface 18a2 and emitted from the surface 18a3. The second light beam Lb is reflected by the mirror 17b and the surface 18a1 and emitted from the surface 18a3.

[0324] The traveling direction of the first light beam La emitted from the surface 18a3 to the outside is The traveling direction of the second light beam Lb emitted from the surface 18a3 to the outside is Therefore, the first light beam La and the second light beam Lb are in a mirror-symmetric relationship with respect to the plane 24 .

[0325] The direction of the surface of the optical path adjustment element 11-1, the directions of the two mirrors 17a and 17b, and the direction of the surface of the prism 18 can be set so that 2ρ+2μ-2ε+2δ is approximately zero. With such a setting, when the traveling direction of the light beam L incident on the optical path adjustment element 11-1 is zero, the traveling directions of the first light beam La and the second light beam Lb are also approximately zero. However, as in the first embodiment, the traveling directions of the first light beam La and the second light beam Lb do not necessarily have to be completely zero. As in the first embodiment, even if the traveling direction of the light beam L incident on the optical path adjustment element 11-1 is substantially zero, an angular difference can be given to the traveling directions of the first light beam La and the second light beam Lb. When the first light beam La and the second light beam Lb travel close to each other, a first image and a second image can be formed at different positions on the image sensor 30 in a mirror-symmetrical relationship with respect to the plane 24.

[0326] In 2ρ+2μ-2ε+2δ, ρ, μ, and δ are fixed by the shapes of the optical path adjustment element 11-1 and the prism 18, while ε depends on the directions of the two mirrors 17a and 17b. Therefore, ε can be easily adjusted.

[0327] By changing ε, the positions of the first and second images on the image sensor 30 can be moved. Therefore, the positions of the first and second images on the image sensor 30 can be set to desired positions according to the size of the subject 110, the focal length of the imaging optical system 20, and the size of the image sensor 30.

[0328] Figure 32 Schematically shows an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the first modification of the imaging device. Figure 32 As shown, by combining the optical element group 14 and the optical path adjustment element 11 - 1 in Modification 1 with the imaging optical system 20 , a first image and a second image can be formed on the image sensor 30 .

[0329] In Modification 1, the dichroic mirror 16 is commercially available and easily available. By replacing the dichroic mirror 16 , the first wavelength range and the second wavelength range can be easily changed.

[0330] In Modification 1, the angle between the light beam L and the dichroic surface 16a is defined as the incident angle, and the incident angle of the light beam L on the dichroic surface 16a can be, for example, π / 4. Therefore, compared to Embodiment 1, which has a steeper incident angle of π / 3, the dielectric multilayer film constituting the dichroic surface 16a is easier to design and manufacture.

[0331] Furthermore, in Modification 1, the positions of the first image and the second image on the image sensor 30 can be adjusted by changing the directions of the two mirrors 17 a and 17 b .

[0332] [Variation 2]

[0333] Figure 33 This is a diagram schematically showing a specific configuration of an optical component 10A in a second modification of the imaging device 100 according to the first embodiment. Figure 33 The optical component 10A shown includes a dichroic prism 19 and an optical path adjusting element 11 - 1 . Figure 33 The optical component 10A shown may also include Figure 3 The light shielding body 10-2 and the frame 12 are shown. The dichroic prism 19 corresponds to Figure 1 The first subcomponent 10A1 shown, the optical path adjustment element 11-1 corresponds to Figure 2 The second subassembly 10A2 is shown. In this specification, the dichroic prism 19 is also referred to as the "first optical element".

[0334] Figure 34 Schematically shows the dichroic prism 19 in Modification 2. Figure 34 As shown, the dichroic prism 19 includes a first prism 19a and a second prism 19b. The first prism 19a has a surface 19a1, a surface 19a2, a surface 19a3, and a surface 19a4. The second prism 19b has a surface 19b1, a surface 19b2, a surface 19b3, and a surface 19b4.

[0335] In first prism 19a, surface 19a1 and surface 19a2 form an angle ξ, surface 19a2 and surface 19a3 form an angle τ, and surface 19a2 and surface 19a4 form an angle π / 2. In second prism 19b, surface 19b1 and surface 19b2 form an angle ξ, surface 19b2 and surface 19b3 form an angle τ, and surface 19b2 and surface 19b4 form an angle π / 2.

[0336] Surface 19a2 and surface 19b2 are bonded together by an adhesive layer. The adhesive layer is translucent with respect to the second wavelength range. Surface 19a2 and surface 19b2 can be, for example, parallel to each other. As a result of bonding surface 19a2 and surface 19b2, first prism 19a and second prism 19b are arranged to be mirror-symmetrical to each other.

[0337] One or both of surfaces 19a2 and 19b2 can be, for example, dichroic surfaces that reflect the first light beam La of the light beam L incident from a specific range of directions and transmit the second light beam Lb. The dichroic surfaces perform the aforementioned function when the first prism 19a and the second prism 19b are bonded together. Here, the specific range of directions refers to the range of directions from which the light beam L from the subject 110 is incident. Thus, the dichroic prism 19 includes at least one such dichroic surface. Surfaces 19a3 and 19b3 can be formed with a metal film or a dielectric multilayer film to achieve high light reflectivity.

[0338] Figure 35 : is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the dichroic prism 19 in Modification 2. Figure 35 As shown, surface 19a2 of dichroic prism 19 reflects the first light beam La of light beam L incident in direction θ toward -θ, and transmits the second light beam Lb toward direction θ. In first prism 19a, first light beam La is totally reflected by surface 19a3 and emitted from surface 19a4. The direction of the first light beam La emitted is θ + 2ξ + 2τ. In second prism 19b, second light beam Lb is totally reflected by surface 19b3 and emitted from surface 19b4. The direction of the second light beam Lb emitted is -θ - 2ξ - 2τ.

[0339] As described above, the dichroic prism 19 separates the light beam L into the first light beam La and the second light beam Lb via the surface 19a2. The dichroic prism 19 further changes the directions of the first light beam La and the second light beam Lb via the surfaces 19a3 and 19b3 and emits them.

[0340] When θ is approximately -π / 4, ξ is approximately π / 4, and τ is approximately (7 / 8)π, the directions of travel of the first light beam La and the second light beam Lb emitted to the outside are approximately zero. Since θ is approximately -π / 4 and ξ is approximately π / 4, the light beam L can be incident on the surface 19a1 approximately vertically, and the influence of wavelength dispersion caused by refraction can be reduced.

[0341] Figure 36 : is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the optical component 10A in Modification 2. Figure 36 As shown, in the direction The light beam L incident on the optical path adjusting element 11-1 is reflected internally and then emitted to the outside. The direction of the light beam L emitted from the optical path adjusting element 11-1 to the outside is

[0342] Light beam L enters surface 19a1 and is separated by surface 19a2 into first light beam La and second light beam Lb. First light beam La is totally reflected by surface 19a3 and emitted from surface 19a4. Second light beam Lb is totally reflected by surface 19b3 and emitted from surface 19b4.

[0343] The traveling direction of the first light beam La emitted from the surface 19a4 to the outside is The traveling direction of the second light beam Lb emitted from the surface 19b4 to the outside is Therefore, similarly to the first embodiment and the first modification thereof, the first light beam La and the second light beam Lb are in a mirror-symmetrical relationship with respect to the plane 24 .

[0344] When ρ is approximately π / 4 and μ is approximately 5π / 8, if is approximately zero, is approximately -π / 4. In addition, when ξ is approximately π / 4 and τ is approximately (7 / 8)π, the directions of travel of the first light beam La and the second light beam Lb are approximately zero. However, as in the first embodiment and its modified example 1, the directions of travel of the first light beam La and the second light beam Lb do not necessarily need to be completely zero. By adjusting any one of ρ, μ, ξ, and τ, even if Even if the angle difference is substantially zero, the traveling directions of the first light beam La and the second light beam Lb can be given. When the first light beam La and the second light beam Lb travel close to each other, the first image and the second image can be formed at different positions on the image sensor 30 in a mirror-symmetrical relationship with respect to the plane 24.

[0345] Figure 37 : is a diagram schematically showing an example of the paths of the light beam L, the first light beam La, and the second light beam Lb in the modified example 2 of the imaging device. Figure 37 As shown, similarly to the first embodiment and the first modification thereof, by combining the dichroic prism 19 and the optical path adjustment element 11 - 1 with the imaging optical system 20 , a first image and a second image can be formed on the image sensor 30 .

[0346] In Modification 2, the incident angle of the light beam L on the surface 19a2 is π / 4. Therefore, compared with Embodiment 1 where the incident angle is steep, such as π / 3, the dielectric multilayer film constituting the surface 19a2 is easier to design and manufacture.

[0347] Furthermore, in Modification 2, surface 19a1, which serves as the incident surface into which the light beam L is incident, and surface 19a3, which serves as the reflecting surface for reflecting the first light beam La and emitting it to the outside of the dichroic prism 19, are separated. Therefore, with respect to surface 19a1, there is no need to consider the total reflection condition of the first light beam La, and restrictions on the material of the dichroic prism 19 are relaxed.

[0348] Furthermore, in Modification 2, the dichroic prism 19 is formed of a single optical element. Therefore, compared with Modification 1 in which the optical element group 14 includes a plurality of optical elements, assembly and adjustment of the dichroic prism 19 are easier.

[0349] (Implementation Method 2)

[0350] In Embodiment 1 and its Modifications 1 and 2, the imaging device acquires two images from a subject in different wavelength ranges as an example of two images having different optical characteristics. As another example of two images having different optical characteristics, the imaging device can acquire two images from a subject having different polarization states.

[0351] Figure 38 This is a diagram schematically showing a specific configuration of an imaging device according to an exemplary embodiment 2 of the present disclosure. Figure 38 The imaging device 100-1 shown in FIG. 1 obtains two images having different polarization states from the subject 110. Figure 38 As shown, the imaging apparatus 100 - 1 includes an optical component 10A, a lens device 20A, and a camera 30A.

[0352] The optical component 10A includes an optical path adjustment element 11-1, a prism 19-1, and a phase plate 19c. However, the phase plate 19c is not an essential component. The lens device 20A includes an imaging optical system 20. The camera 30A includes an image sensor 30. The optical path adjustment element 11-1, the imaging optical system 20, and the image sensor 30 are as described above. Figure 3 As shown in FIG. 2 , the lens device 20A may further include a lens frame 22 that houses the imaging optical system 20. Figure 3 As shown, the camera 30A may further include a camera housing 32 that houses the image sensor 30. In this specification, the prism 19-1 is also referred to as a "first optical element."

[0353] Figure 38 The prism 19-1 shown is Figure 34The difference of the dichroic prism 19 shown is that one or both of the surfaces 19a2 and 19b2 are polarizing beam splitter surfaces, which reflect the first light beam La of the first polarization state in the light beam L incident from a specific range of directions, and transmit the second light beam Lb of the second polarization state. The first polarization state and the second polarization state are polarization states different from each other. The polarizing beam splitter surface reflects light having an electric field vector parallel to itself and transmits light having an electric field vector perpendicular to itself. Figure 38 In the example shown, the first polarization state is S polarization, and the second polarization state is P polarization. The polarization beam splitter surface is arranged on the plane 24 .

[0354] When light enters the polarization beam splitter surface from a direction of about -π / 4, it is easy to design a film having the above-mentioned function. Figure 38 The shape shown allows the light beam L to enter one or both of the surfaces 19a2 and 19b2 from a direction of approximately -π / 4, and the light beam L to enter the surface 19a1 approximately perpendicularly.

[0355] However, the polarization states of the incident and outgoing light may change due to the passage through the optical path adjustment element 11-1. For example, linearly polarized light entering the optical path adjustment element 11-1 may be converted to elliptically polarized light before being emitted. This is because reflection within the optical path adjustment element 11-1 can cause the polarization state to change.

[0356] The phase plate 19c compensates for the change in polarization state caused by the optical path adjusting element 11-1. As a result, the linearly polarized light incident on the optical path adjusting element 11-1 can be incident on the prism 19-1 as linearly polarized light.

[0357] The first light beam La and the second light beam Lb emitted from prism 19-1 are symmetrical with respect to plane 24. Therefore, two images with different polarization states can be formed simultaneously and mirror-symmetrically on the imaging plane of image sensor 30. As a result, even image sensor 30, whose pixel sensitivity is not polarization-dependent, can capture two images with different polarization states. Image sensor 30 can be, for example, a conventional image sensor or a hyperspectral image sensor capable of acquiring spectral information of light.

[0358] Furthermore, even if the light beam L entering the prism 19-1 is linearly polarized, the first light beam La and the second light beam Lb emitted from the prism 19-1 may be elliptically polarized due to the light beam passing through the prism 19-1. Even in this case, in the image sensor 30, in which the sensitivity of each pixel is not polarization-dependent, the polarization state of the image captured is determined solely by the position of the image on the image sensor 30, and therefore, there is no need to compensate for changes in the polarization state caused by the prism 19-1.

[0359] As described above, the imaging device 100-1 of the second embodiment can obtain two images having different polarization states suitable for evaluating the subject 110. How to obtain the two images with a simple structure and a natural orientation can be as described in the first embodiment.

[0360] (Modification of Imaging Device 100-1 of Embodiment 2)

[0361] Hereinafter, Modifications 1 to 3 of the imaging device 100 - 1 according to the second embodiment will be described.

[0362] [Variation 1]

[0363] Figure 39 This is a diagram schematically showing the configuration of a first modification of the imaging device 100 - 1 according to the second embodiment. Figure 39 The camera 110-1 shown is Figure 38 The illustrated imaging device 100 - 1 is different in the structure of the optical component 10A. Figure 39 The optical component 10A shown includes an optical path adjustment element 11-1, an optical path adjustment element 11-2, an optical path adjustment element 11-3, a beam splitter cube 19-2, and a phase plate 19c. However, the phase plate 19c is not an essential component. Commercially available half-pentaprisms can be used as the optical path adjustment elements 11-1, 11-2, and 11-3, and a commercially available polarizing beam splitter cube can be used as the beam splitter cube 19-2. In this specification, the beam splitter cube 19-2, the optical path adjustment element 11-2, and the optical path adjustment element 11-3 are collectively referred to as the "first optical element."

[0364] The beam splitting cube 19-2 includes a prism 19-2a and a prism 19-2b, and a cube is formed by combining these two prisms, each of which is a rectangular prism.

[0365] The prism 19-2a has a surface 19-2a1, a surface 19-2a2, and a surface 19-2a3. The surface 19-2a1 forms a right angle with the surface 19-2a3. The surface 19-2a2 forms an acute angle with the surface 19-2a1 and also forms an acute angle with the surface 19-2a3.

[0366] Similarly, prism 19-2b has surface 19-2b1, surface 19-2b2, and surface 19-2b3. Surface 19-2b1 forms a right angle with surface 19-2b3. Surface 19-2b2 forms an acute angle with surface 19-2b1 and an acute angle with surface 19-2b3.

[0367] The beam splitter cube 19-2 has a polarizing beam splitter surface at the interface between surface 19-2a2 and surface 19-2b2. The polarizing beam splitter surface is described above. Of the light beam L from the subject 110, the first light beam La enters surface 19-2a1, is reflected by surface 19-2a2, and is emitted from surface 19-2a3. Of the light beam L from the subject 110, the second light beam Lb enters surface 19-2a1, passes through surfaces 19-2a2 and 19-2b2, and is emitted from surface 19-2b3. A phase plate 19c may be disposed between the optical path adjustment element 11-1 and the beam splitter cube 19-2 to compensate for changes in the polarization state caused by the optical path adjustment element 11-1.

[0368] The optical path adjusting element 11-1 changes the direction of travel of the light beam L from the subject 110, which enters from a direction substantially parallel to the optical axis of the imaging optical system 20, by approximately -π / 4, and directs the beam into the beam splitting cube 19-2. The beam splitting cube 19-2 outputs the first light beam La from the light beam L from the subject 110 in a direction reversed relative to the polarizing beam splitter surface, and directs the beam into the optical path adjusting element 11-2. The beam splitting cube 19-2 outputs the second light beam Lb from the light beam L from the subject 110 in the same direction as the direction of travel when the beam was incident, and directs the beam into the optical path adjusting element 11-3.

[0369] The optical path adjusting element 11-2 changes the direction of travel of the incident first light beam La by approximately -π / 4 and causes it to enter the imaging optical system 20. The optical path adjusting element 11-3 changes the direction of travel of the incident second light beam Lb by approximately π / 4 and causes it to enter the imaging optical system 20. By arranging the polarization beam splitter surface on the plane 24, the first light beam La emitted from the optical path adjusting element 11-2 and the second light beam Lb emitted from the optical path adjusting element 11-3 are symmetrical with respect to the plane 24. Therefore, two images having different optical states can be formed in mirror-symmetrical fashion. Even in an image sensor 30 in which the sensitivity of each pixel is not polarization-dependent, two images having different polarization states can be obtained.

[0370] [Variation 2]

[0371] Figure 40 This is a diagram schematically showing the configuration of a second modification of the imaging device 100 - 1 according to the second embodiment. Figure 40 The illustrated imaging device 120 - 1 is capable of full-Stokes imaging. Figure 40 The camera device 120-1 shown is Figure 39 The illustrated imaging apparatus 110 - 1 differs in the structure of the optical component 10A and the structure of the camera 30A.

[0372] Figure 40The optical component 10A shown includes a beam splitter cube 19-3 which is a beam splitter cube independent of polarization, instead of Figure 39 Beamsplitter cube 19-2 is shown. Figure 40 The optical component 10A shown further includes a phase plate 19c1 disposed on the light exit side of the optical path adjustment element 11-2 and a phase plate 19c2 disposed on the light exit side of the optical path adjustment element 11-3, instead of Figure 39 Phase plate 19c is shown. Figure 40 The camera 30A shown in FIG. 1 includes a polarization image sensor 30 capable of measuring a linear polarization component, instead of Figure 39 In this specification, the beam splitting cube 19-3, the optical path adjusting element 11-2, the optical path adjusting element 11-3, the phase plate 19c1 and the phase plate 19c2 are collectively referred to as "first optical element".

[0373] Beam splitting cube 19-3 is identical to beam splitting cube 19-2, except that one or both of surfaces 19-2a2 and 19-2b2 are semi-transparent membranes. Regardless of the polarization state, the semi-transparent membrane reflects half of the incident light beam L from a direction of approximately π / 4 as the first light beam La and transmits the remaining half as the second light beam Lb. The semi-transparent membrane is disposed on plane 24.

[0374] The optical path adjusting element 11-1 changes the direction of travel of the light beam L from the subject 110, which enters from a direction substantially parallel to the optical axis of the imaging optical system 20, by approximately -π / 4, and then causes the light beam to enter the beam splitting cube 19-3. The beam splitting cube 19-3 causes the first light beam La of the light beam L from the subject 110 to be emitted in a direction reversed relative to the polarizing beam splitter surface, and causes the light beam to enter the optical path adjusting element 11-2. The beam splitting cube 19-3 causes the second light beam Lb of the light beam L from the subject 110 to be emitted in the same direction as the direction of travel when the light beam entered, and causes the light beam to enter the optical path adjusting element 11-3.

[0375] The optical path adjusting element 11-2 changes the direction of the incident first light beam La by approximately -π / 4 and allows it to enter the imaging optical system 20 via the phase plate 19c1. The optical path adjusting element 11-3 changes the direction of the incident second light beam Lb by approximately π / 4 and allows it to enter the imaging optical system 20 via the phase plate 19c2.

[0376] The first light beam La entering the imaging optical system 20 via the phase plate 19c1 undergoes a change in polarization state due to passing through the optical path adjustment element 11-1, being reflected by the beam splitting cube 19-3, and passing through the optical path adjustment element 11-2 before entering the phase plate 19c1. The second light beam Lb entering the imaging optical system 20 via the phase plate 19c2 undergoes a change in polarization state due to passing through the optical path adjustment element 11-1, passing through the beam splitting cube 19-3, and passing through the optical path adjustment element 11-3 before entering the phase plate 19c2.

[0377] Therefore, the phase plate 19c1 compensates for the aforementioned change in the polarization state of the first light beam La and restores the polarization state of the first light beam La to the polarization state at the object 110. In contrast, the phase plate 19c2 compensates for the aforementioned change in the polarization state of the second light beam Lb and restores the polarization state of the second light beam Lb to the polarization state at the object 110, and further imparts a polarization phase of π / 4 to the second light beam Lb.

[0378] In this case, the image of the first light beam La formed by the imaging optical system 20 maintains the polarization state at the subject 110. The image of the second light beam Lb formed by the imaging optical system 20 is an image with a phase shift of π / 4 from the polarization state at the subject 110. By capturing these two images with the polarization image sensor 30-1, all components of the Stokes parameters can be acquired in a single image capture. Information related to the elliptical polarization of the subject 110 can be obtained from all components of the Stokes parameters. Acquiring all components of the Stokes parameters is effective for, for example, product inspection and material analysis.

[0379] [Variation 3]

[0380] Figure 41 This is a diagram schematically showing the configuration of a third modification of the imaging device 100 - 1 according to the second embodiment. Figure 41 The camera 130-1 shown is Figure 40 The illustrated imaging device 120 - 1 is different in the structure of the optical component 10A.

[0381] Figure 41 The optical component 10A shown in the figure has optical path adjustment elements 11-4, 11-5, and 11-6 as metal mirrors, instead of Figure 40 The optical path adjustment elements 11-1, 11-2, and 11-3 shown as half pentaprisms. The change of polarization state occurs due to reflection at the dielectric interface, not due to reflection at the metal interface. Figure 41 In the illustrated optical component 10A, there is no need to compensate for changes in polarization state.

[0382] Figure 41 The optical component 10A shown further includes a phase plate 19c3 on the light emitting side of the optical path adjusting element 11-6. The phase plate 19c3 imparts a change in polarization phase of π / 4 to the second light beam Lb.

[0383] In this specification, the beam splitting cube 19-3, the optical path adjustment element 11-5, the optical path adjustment element 11-6, and the phase plate 19c3 are collectively referred to as the "first optical element", and the optical path adjustment element 11-4 is also referred to as the "second optical element".

[0384] In the third modification, similarly to the second modification, all components of the Stokes parameters can be acquired in one imaging operation.

[0385] (Application Example)

[0386] Hereinafter, application examples 1 to 3 of the imaging device 100 according to the first embodiment will be described.

[0387] [Application Example 1: Temperature Measurement]

[0388] Reference Figure 42A and Figure 42B , temperature measurement using the imaging device 100 according to the first embodiment will be described. Figure 42A This is a diagram schematically showing an example of a measurement system including the imaging device 100 according to the first embodiment. Figure 42A The illustrated measurement system 200A measures the temperature of the subject 110 .

[0389] like Figure 42A As shown, the measurement system 200A includes an imaging device 100 for capturing an image of a subject 110 and a heating device 120 for heating the subject 110. The heating device 120 can locally heat a portion of the subject 110 or heat the entire subject 110. The heating device 120 can be, for example, Figure 42A The laser device shown may be a laser device that locally heats the object 110 using laser light indicated by a bold line. Alternatively, the heating device 120 may be a heating lamp or a resistance heater that heats the entire object 110.

[0390] As the first and second wavelength ranges, wavelength ranges that provide sufficiently high thermal radiation intensity within the temperature range to be monitored for the subject 110 are selected. If the temperature range to be monitored is between 200°C and 500°C, and the image sensor 30 is formed of InGaAs or quantum dots, two different wavelength ranges can be selected as the first and second wavelength ranges within the wavelength range of 1.3 μm to 1.6 μm.

[0391] For example, two different wavelength ranges with roughly equal emissivity of the subject 110 can be selected as the first wavelength range and the second wavelength range. When the subject 110 is formed of a metal material or ceramic, the subject 110 often does not have characteristic absorption in the wavelength range of 1.3 μm to 1.6 μm. When the subject 110 is formed of an organic material such as resin, the subject 110 may have resonant absorption in the wavelength range of 1.3 μm to 1.6 μm. The wavelength range in which resonant absorption occurs is different from the wavelength range around it, and the emissivity is greatly different. Therefore, the wavelength range that produces strong resonant absorption can be avoided as the first wavelength range and the second wavelength range.

[0392] The measurement system 200A may further include an optical element as an auxiliary optical element that attenuates or blocks light of wavelengths other than the first wavelength range and the second wavelength range. For example, if the subject 110 is illuminated by visible light and the image sensor 30 is sensitive to visible light, the measurement system 200A may further include an optical element that blocks the visible light.

[0393] When the object 110 is heated by the heating device 120 , the temperature of the object 110 rises, and heat radiation is generated according to its temperature and emissivity. Figure 42B Schematically shows an example of the spectrum of thermal radiation from the subject 110 . Figure 42B The solid line shown represents the spectrum in the high temperature region of the object 110. Figure 42B The dashed line shows the spectrum in the low-temperature region of subject 110. The high-temperature region radiates heat at higher intensities at all wavelengths compared to the low-temperature region. However, this intensity ratio increases toward shorter wavelengths and decreases toward longer wavelengths. When two different wavelength ranges with approximately equal emissivity are selected as first wavelength range 118a and second wavelength range 118b, the ratio of the radiation intensities in the first and second wavelength ranges depends on temperature but not on emissivity.

[0394] Therefore, two different wavelength ranges are selected to obtain sufficient radiation intensity for imaging and have substantially equal emissivity as the first wavelength range 118a and the second wavelength range 118b. The widths of the first wavelength range 118a and the second wavelength range 118b are substantially equal to each other.

[0395] The measurement system 200A simultaneously acquires the first image 110a and the second image 110b of the object 110 and calculates the ratio of the radiation intensity in the first wavelength range 118a to the second wavelength range 118b. As a result, the temperature distribution of the object 110 can be determined regardless of the emissivity.

[0396] Measurement system 200A captures images of light with wavelengths within the first wavelength range and light with wavelengths within the second wavelength range, both of which are generated by thermal radiation. Measurement system 200A does not include an illumination device that emits light with wavelengths within these wavelength ranges. Alternatively, such an illumination device is not used during temperature measurement. In the presence of ambient light such as sunlight, which includes both wavelengths within the first wavelength range and wavelengths within the second wavelength range, subject 110 and imaging device 100 may be surrounded by a light shield to prevent such ambient light from entering subject 110.

[0397] [Application Example 2: Measurement of Fluorescence Efficiency]

[0398] Reference Figure 43A and Figure 43B , the measurement of the fluorescence luminous efficiency using the imaging device 100 according to the first embodiment is described. Figure 43A This is a diagram schematically showing another example of a measurement system including the imaging device 100 according to the first embodiment. Figure 43A Measurement system 200B shown measures the fluorescence emission efficiency of subject 110. Subject 110 contains a fluorescent dye that absorbs light having wavelengths within a first wavelength range and emits light having wavelengths within a second wavelength range. In this case, the second wavelength range is on the longer wavelength side of the first wavelength range.

[0399] The measurement system 200B includes an imaging device 100 for capturing an image of a subject 110 and an illumination device 130 for emitting excitation light Le as illumination light for illuminating the subject 110. When the subject 110 is illuminated with the excitation light Le, fluorescence Lf is emitted from a region of the subject 110 having non-zero luminous efficiency.

[0400] As the first wavelength range, a wavelength range that includes the wavelength range of the excitation light Le and substantially excludes the wavelength range of the fluorescence Lf is selected, and as the second wavelength range, a wavelength range that includes the wavelength range of the fluorescence Lf and substantially excludes the wavelength range of the excitation light Le is selected. The excitation light Le includes light having a wavelength included in the first wavelength range and does not include light having a wavelength included in the second wavelength range.

[0401] Figure 43B Schematically shows examples of spectra of excitation light Le and fluorescence Lf. Figure 43B The solid line shown represents the spectrum of the excitation light Le, Figure 43BThe dashed line shows the spectrum of the fluorescent light Lf. The spectrum of the excitation light Le is relatively narrow, while the spectrum of the fluorescent light Lf is relatively wide. Therefore, the width of the first wavelength range 118a corresponding to the excitation light Le is relatively narrow, while the width of the second wavelength range 118b corresponding to the fluorescent light Lf is relatively wide.

[0402] The intensity of the excitation light Le on the object 110 is two-dimensionally distributed according to the optical characteristics of the lighting device 130 and the shape of the object 110. The intensity of the fluorescent light Lf is proportional to the intensity of the excitation light Le and the luminous efficiency.

[0403] When subject 110 is excited by excitation light Le emitted from illumination device 130, the intensity of the excitation light Le is obtained as a first image 110a, the intensity of the fluorescence Lf is obtained as a second image 110b, and the intensity ratio is calculated. As a result, the distribution of luminous efficiency of subject 110 can be visualized regardless of the intensity distribution of the excitation light Le.

[0404] The distribution of luminous efficiency can be correlated with, for example, the staining concentration when the object 110 is stained with a fluorescent substance. If fluorescent staining is performed using a so-called antigen-antibody staining method, the concentration of the antigen can be visualized.

[0405] Alternatively, the distribution of luminous efficiency can be correlated with the distribution of the quencher, for example. The more concentrated the quencher distribution is, the lower the luminous efficiency is. In this way, information related to the concentration of the quencher can be obtained by the measurement system 200B.

[0406] [Application Example 3: Visualization of Material Distribution]

[0407] Reference Figures 44A to 44C , visualization of material distribution using the imaging device 100 according to the first embodiment is described. Figure 44A This is a diagram schematically showing another example of a measurement system including the imaging device 100 according to the first embodiment. Figure 44A The illustrated measurement system 200C visualizes the distribution of a specific substance in the subject 110 .

[0408] Measurement system 200C includes an imaging device 100 for capturing an image of a subject 110, and an illumination device 140 for emitting illumination light Li for illuminating subject 110. Illumination light Li includes light having wavelengths within a first wavelength range and light having wavelengths within a second wavelength range. If ambient light includes light having wavelengths within the first wavelength range and light having wavelengths within the second wavelength range, illumination device 140 may be omitted.

[0409] The subject 110 contains at least two substances. The two substances are referred to as a first substance and a second substance. Assume that the first substance has approximately equal reflectivity in the first wavelength range and the second wavelength range, while the second substance has a significantly different reflectivity in the first wavelength range and the second wavelength range. The absolute value of the difference between the reflectivity of the first substance in the first wavelength range and the second wavelength range can be, for example, 5% or less. The absolute value of the difference between the reflectivity of the second substance in the first wavelength range and the second wavelength range can be, for example, 10% or more. The ratio of the reflectivity of the first substance in the first wavelength range and the second wavelength range is different from the ratio of the reflectivity of the second substance in the first wavelength range and the second wavelength range.

[0410] The imaging device 100 acquires a first image 110a and a second image 110b of the object 110 illuminated by the illumination light Li, and calculates the intensity ratio between the two. In areas of the object 110 where only the first substance is distributed, the intensity ratio is close to 1, while in areas where a large amount of the second substance is distributed, the intensity ratio deviates from 1. Therefore, the distribution of the second substance within the object 110 can be visualized based on the intensity ratio between the two.

[0411] An example of the effectiveness of visualization of this substance is the visualization of wet clothes. Figure 44B This is a diagram schematically showing an example of the absorption spectrum of water. The absorption and reflection spectra of substances vary depending on the substance. In the case of water, Figure 44B As shown, the absorption coefficient is low in the wavelength range of 1.35 μm or less. In contrast, the absorption coefficient is high in the wavelength range of 1.4 μm to 1.5 μm. In these wavelength ranges, the absorption coefficient of many fibers used in clothing does not depend as strongly on wavelength as water.

[0412] Therefore, when the garment includes a first region that is wetted by water and a second region that is not wetted by water, there is no significant difference in reflectivity between the first region and the second region within the wavelength range of 1.35 μm or less, where the water absorption coefficient is relatively low. In contrast, within the wavelength range of 1.4 μm to 1.5 μm, where the water absorption coefficient is relatively high, the reflectivity of the first region is intentionally lower than that of the second region.

[0413] Therefore, a wavelength range with a low water absorption coefficient is selected as the first wavelength range, and a range with a high water absorption coefficient is selected as the second wavelength range. In addition, an illumination device 140 is used that emits light in the first and second wavelength ranges as illumination light Li. Figure 44C : is a diagram schematically showing an example of the spectrum of the illumination light Li. Figure 44CAs shown, the intensities of the illumination light Li in the first wavelength range 118a and the second wavelength range 118b are substantially equal to each other. The widths of the first wavelength range 118a and the second wavelength range 118b are substantially equal to each other.

[0414] The intensity of the illumination light Li on the subject 110 is two-dimensionally distributed according to the optical characteristics of the illumination device 140 and the shape of the subject 110. By adjusting the illumination light Li, the intensity distribution of light having wavelengths included in the first wavelength range 118a and the second wavelength range 118b included in the illumination light Li can be made uniform on the subject 110.

[0415] The imaging device 100 captures a first image 110a and a second image 110b of a subject 110 illuminated by illumination light Li, and calculates their intensity ratio. This intensity ratio does not depend on the intensity distribution of the illumination light Li, but rather on the ratio of the reflectance of the subject 110 in the first wavelength range 118a and the second wavelength range 118b. This allows visualization of wet areas within the subject 110, where the water absorption coefficient is high.

[0416] [Note]

[0417] The following techniques are disclosed through the description of the above embodiments.

[0418] [Technology 1]

[0419] A camera device, comprising:

[0420] a first optical element that separates a light beam from a subject into a first light beam and a second light beam, the second light beam having optical characteristics different from those of the first light beam;

[0421] an imaging optical system into which the first light beam and the second light beam are incident at different angles, and into which the first light beam is imaged to form a first image and into which the second light beam is imaged to form a second image; and

[0422] An image sensor having an imaging surface,

[0423] The first image and the second image are formed at different positions on the imaging plane.

[0424] The first image and the second image are formed symmetrically on the imaging plane with reference to a plane intersecting the imaging plane.

[0425] This imaging device can acquire two images having different optical characteristics suitable for evaluating a subject with a simple configuration.

[0426] [Technique 2]

[0427] The imaging device according to technique 1, wherein:

[0428] The optical system further includes a connection structure for fixing the positional relationship between the first optical element and the imaging optical system.

[0429] In this imaging device, the dichroic prism and the imaging optical system can be fixed in a desired positional relationship, more specifically, in a desired angular relationship.

[0430] [Technique 3]

[0431] The imaging device according to technique 1 or 2, wherein:

[0432] It also has a lens frame and a camera frame.

[0433] The lens frame includes the imaging optical system,

[0434] The camera frame includes the image sensor,

[0435] The lens housing and the camera housing are detachable.

[0436] In this imaging device, general lens housings and camera housings can be arbitrarily combined.

[0437] [Technique 4]

[0438] The imaging device according to any one of techniques 1 to 3, wherein:

[0439] The first image and the second image formed on the imaging plane are each smaller than the object.

[0440] In this imaging device, even in the above-mentioned case, it is possible to reduce aberrations generated when a light beam having a diverging angle passes through an optical element.

[0441] [Technique 5]

[0442] The imaging device according to any one of techniques 1 to 4, wherein:

[0443] A second optical element is further provided for changing the direction of the light beam from the subject and causing the light beam to enter the first optical element.

[0444] In this imaging device, the imaging optical system can be directed in a natural direction.

[0445] [Technique 6]

[0446] The imaging device according to any one of techniques 1 to 5, wherein:

[0447] A light-blocking body is further provided to block an unintended light beam from entering the first optical element.

[0448] In this imaging device, stray light can be reduced.

[0449] [Technique 7]

[0450] The imaging device according to any one of techniques 1 to 6, wherein:

[0451] the first light beam having a wavelength included in a first wavelength range,

[0452] the second light beam has a wavelength included in a second wavelength range,

[0453] The first optical element has a dichroic surface, the dichroic surface reflects the first light beam and transmits the second light beam,

[0454] The dichroic surface is arranged on the plane.

[0455] In this imaging device, two images in different wavelength ranges can be acquired as two images having different optical characteristics.

[0456] [Technology 8]

[0457] The imaging device according to technique 7, wherein:

[0458] The first optical element is a dichroic prism having the dichroic surface.

[0459] In this imaging device, a first light beam and a second light beam in mutually different wavelength ranges can be separated from a light beam of an object by a single dichroic prism.

[0460] [Technique 9]

[0461] The imaging device according to technique 7, wherein:

[0462] The first optical element includes a dichroic mirror having the dichroic surface, a first mirror, a second mirror, and a prism.

[0463] The first mirror reflects the first light beam and makes it enter the prism.

[0464] The second mirror reflects the second light beam and makes it enter the prism.

[0465] The triangular prism emits the first light beam and the second light beam to the outside of the triangular prism.

[0466] In this imaging device, by changing the directions of the two mirrors, the positions of two images in different wavelength ranges on the image sensor can be adjusted.

[0467] [Technique 10]

[0468] The imaging device according to any one of techniques 1 to 6, wherein:

[0469] The first light beam has a first polarization state,

[0470] The second light beam has a second polarization state,

[0471] The first optical element has a polarizing beam splitter surface, the polarizing beam splitter surface reflects the first light beam and transmits the second light beam,

[0472] The polarizing beam splitter surface is arranged on the plane.

[0473] In this imaging device, two images having different polarization states can be acquired as two images having different optical characteristics.

[0474] [Technology 11]

[0475] The imaging device according to technique 10, wherein:

[0476] The first optical element is a prism having the polarizing beam splitter surface.

[0477] In this imaging device, a first light beam and a second light beam having different polarization states from each other can be separated from a light beam of an object by a single dichroic prism.

[0478] [Technology 12]

[0479] An optical component, in the sense of a camera device, includes an imaging optical system and an image sensor, wherein:

[0480] A first optical element is provided, the first optical element separates a light beam from a subject into a first light beam and a second light beam, and emits the first light beam and the second light beam symmetrically with respect to a certain plane, wherein the second light beam has optical characteristics different from those of the first light beam.

[0481] The first light beam and the second light beam enter the imaging optical system at different angles from each other.

[0482] The imaging optical system images the first light beam to form a first image, and images the second light beam to form a second image.

[0483] The image sensor has an imaging surface.

[0484] The first image and the second image are formed at different positions on the imaging plane.

[0485] This optical component makes it possible to obtain two images having different optical characteristics suitable for evaluating a subject with a simple configuration using a general lens device and a camera.

[0486] [Technology 13]

[0487] The optical component according to technique 12, wherein

[0488] A second optical element is further provided for changing the direction of the light beam from the subject and causing the light beam to enter the first optical element.

[0489] This optical component enables the imaging optical system to be oriented in a natural direction.

[0490] [Technology 14]

[0491] The optical component according to technique 12 or 13, wherein

[0492] A light-blocking body is further provided to block an unintended light beam from entering the first optical element.

[0493] This optical component can reduce stray light.

[0494] [Technology 15]

[0495] The optical component according to any one of Techniques 12 to 14, wherein:

[0496] The camera device further includes a lens frame,

[0497] The lens frame includes the imaging optical system,

[0498] The optical component is attachable to and detachable from the lens frame.

[0499] This optical component can be attached to or detached from a general lens frame.

[0500] [Technology 16]

[0501] The optical component according to any one of Techniques 12 to 15, wherein:

[0502] the first light beam having a wavelength included in a first wavelength range,

[0503] the second light beam has a wavelength included in a second wavelength range,

[0504] The first optical element has a dichroic surface, the dichroic surface reflects the first light beam and transmits the second light beam,

[0505] The dichroic surface is arranged on the plane.

[0506] This optical component enables acquisition of two images in different wavelength ranges as two images having different optical characteristics.

[0507] [Technology 17]

[0508] The optical component according to technique 16, wherein

[0509] The first optical element is a dichroic prism having the dichroic surface.

[0510] With this optical component, it is possible to separate a first light beam and a second light beam in mutually different wavelength ranges from a light beam of an object using a single dichroic prism.

[0511] [Technology 18]

[0512] The optical component according to any one of Techniques 12 to 15, wherein:

[0513] The first light beam has a first polarization state,

[0514] The second light beam has a second polarization state,

[0515] The first optical element has a polarizing beam splitter surface that reflects the first light beam and transmits the second light beam.

[0516] The polarizing beam splitter surface is arranged on the plane.

[0517] This optical component enables acquisition of two images having different polarization states as two images having different optical characteristics.

[0518] [Technology 19]

[0519] A measurement system comprising:

[0520] The imaging device according to any one of techniques 1 to 9; and

[0521] A heating device heats the object.

[0522] This measurement system can measure the temperature of a subject.

[0523] [Technology 20]

[0524] A measurement system comprising:

[0525] The imaging device according to any one of techniques 1 to 9; and

[0526] The lighting device emits lighting light for illuminating the subject.

[0527] In this measurement system, when the subject contains a fluorescent dye, the fluorescence emission efficiency of the subject can be measured.

[0528] Industrial applicability

[0529] The imaging device of the present disclosure is particularly effective for two-color thermal imaging and fluorescence imaging. Furthermore, the imaging device of the present disclosure is also effective for visualizing the distribution of substances.

[0530] Description of Reference Numerals

[0531] 10.19 Dichroic prism

[0532] 10-1, 11-1, 11-2, 11-3, 11-4, 11-5, 11-6 Optical path adjustment elements

[0533] 10-2, 10-3 Light shielding body

[0534] 10A Optical components

[0535] 10A1 First subassembly

[0536] 10A2 Second subassembly

[0537] 10a First right-angle prism

[0538] 10b Second right-angle prism

[0539] 10a1, 10a2, 10a3, 10b1, 10b2, 10b3, 10-1a1, 10-1a2, 10-1a3, 11a2, 11-1a1, 11-1a2, 11-1a3, 11-1a4, 11-1a5, 13a1, 15a1, 18a1, 18a2, 18a3, 19a1, 19a2, 19a3, 19a4, 19b1, 19b2, 19b3, 19b4, 19-2a1, 19-2a2, 19-2a3, 19-2b1, 19-2b2, 19-2b3

[0540] 10a4, 10b4 planes

[0541] Prisms 11a, 11b, 13a, 15a, 19a, 19b, 19-2a, 19-2b

[0542] 14 Optical Components

[0543] 16 Dichroic Mirror

[0544] 16a Dichroic surface

[0545] 17a, 17b reflectors

[0546] 18 Prism

[0547] 19-1 Prism

[0548] 19-2, 19-3 Beam Splitting Cube

[0549] 19c, 19c1, 19c2, 19c3 phase plates

[0550] 12 Frame

[0551] 12a, 22a side walls

[0552] 12b, 22b1, 22b2 light-transmitting windows

[0553] 12c, 22c1, 22c2 connection structure

[0554] 20 Imaging Optical System

[0555] 20A lens equipment

[0556] 22 Lens frame

[0557] 24 planes

[0558] 26a Front main point

[0559] 26b Rear main point

[0560] 30 Image Sensor

[0561] 30-1 Polarized Image Sensor

[0562] 30A Camera

[0563] 30a, 30b, 32a, 32b, 32c range

[0564] 31 filter array

[0565] 31a First filter section

[0566] 31b Second filter section

[0567] 32 Camera frame

[0568] 34 Image Circle

[0569] 36 Camera range

[0570] 38 Reference position

[0571] 40 Adjustment Equipment

[0572] 40a full thread

[0573] 40b Fastening ring

[0574] 42 Fixtures

[0575] 42a Centering ring

[0576] 42b Clamping ring

[0577] 90A, 90B camera device

[0578] 91 Subject

[0579] 91a First image 91a1, 91a2, 91a3, 91a4, 91b1, 91b2, 91b3, 91b4 points

[0580] 91b Second Image

[0581] 92a, 92d half-transparent half-reflective mirror

[0582] 92b, 92c reflectors

[0583] 93a, 93b Bandpass filters

[0584] 94 Imaging Optical System

[0585] 95 Image Sensor

[0586] 95a First image sensor

[0587] 95b Second image sensor

[0588] 95-1 Image Circle

[0589] 95-2 Camera Range

[0590] 95-3 Reference position

[0591] 96 Dichroic Prism

[0592] 100, 100-1, 110-1, 120-1, 130-1 Camera device

[0593] 110 Subject

[0594] 110a First Image

[0595] 110b Second image 110a1, 110a2, 110a3, 110a4, 110b1, 110b2, 110b3, 110b4 points

[0596] 112, 114, 116 Subject's face

[0597] 118a First wavelength range

[0598] 118b Second wavelength range

[0599] 120 Heating device

[0600] 130, 140 lighting device

[0601] 200A, 200B, 200C measurement systems

[0602] L beam

[0603] La First Beam

[0604] Lb Second beam

[0605] Lc, Ld apparent beam

[0606] Le excitation light

[0607] Lf fluorescence

[0608] Li lighting

Claims

1. A camera device, wherein: have: a first optical element that separates a light beam from a subject into a first light beam and a second light beam, the second light beam having optical characteristics different from those of the first light beam; an imaging optical system into which the first light beam and the second light beam are incident at different angles, and into which the first light beam is imaged to form a first image and into which the second light beam is imaged to form a second image; as well as An image sensor having an imaging surface, The first image and the second image are formed at different positions on the imaging plane. The first image and the second image are formed symmetrically on the imaging plane with reference to a plane intersecting the imaging plane.

2. The imaging device according to claim 1, wherein The optical system further includes a connection structure for fixing the positional relationship between the first optical element and the imaging optical system.

3. The imaging device according to claim 1, wherein It also has a lens frame and a camera frame. The lens frame includes the imaging optical system, The camera frame includes the image sensor, The lens housing and the camera housing are detachable.

4. The imaging device according to claim 1, wherein The first image and the second image formed on the imaging plane are each smaller than the object. The imaging device according to claim 1 , wherein: A second optical element is further provided for changing the direction of the light beam from the subject and causing the light beam to enter the first optical element. The imaging device according to claim 1 , wherein: A light blocking body is further provided to block an unintended light beam from entering the first optical element.

7. The imaging device according to claim 1, wherein: the first light beam having a wavelength included in a first wavelength range, the second light beam has a wavelength included in a second wavelength range, The first optical element has a dichroic surface, the dichroic surface reflects the first light beam and transmits the second light beam, The dichroic surface is arranged on the plane.

8. The imaging device according to claim 7, wherein: The first optical element is a dichroic prism having the dichroic surface.

9. The imaging device according to claim 7, wherein: The first optical element includes a dichroic mirror having the dichroic surface, a first mirror, a second mirror, and a prism. The first mirror reflects the first light beam and makes it enter the prism. The second mirror reflects the second light beam and makes it enter the prism. The triangular prism emits the first light beam and the second light beam to the outside of the triangular prism.

10. The imaging device according to claim 1, wherein The first light beam has a first polarization state, The second light beam has a second polarization state, The first optical element has a polarizing beam splitter surface, the polarizing beam splitter surface reflects the first light beam and transmits the second light beam, The polarizing beam splitter surface is arranged on the plane. The imaging device according to claim 10 , wherein: The first optical element is a prism having the polarizing beam splitter surface.

12. An optical component for use in an imaging device comprising an imaging optical system and an image sensor, wherein: A first optical element is provided, the first optical element separates a light beam from a subject into a first light beam and a second light beam, and emits the first light beam and the second light beam symmetrically with respect to a certain plane, wherein the second light beam has optical characteristics different from those of the first light beam. The first light beam and the second light beam enter the imaging optical system at different angles from each other. The imaging optical system images the first light beam to form a first image, and images the second light beam to form a second image. The image sensor has an imaging surface. The first image and the second image are formed at different positions on the imaging plane.

13. The optical component according to claim 12, wherein A second optical element is further provided for changing the direction of the light beam from the subject and causing the light beam to enter the first optical element.

14. The optical component according to claim 12, wherein A light blocking body is further provided to block an unintended light beam from entering the first optical element.

15. The optical component according to claim 12, wherein The camera device further includes a lens frame, The lens frame includes the imaging optical system, The optical component is attachable to and detachable from the lens frame.

16. The optical component according to claim 12, wherein the first light beam having a wavelength included in a first wavelength range, the second light beam has a wavelength included in a second wavelength range, The first optical element has a dichroic surface, the dichroic surface reflects the first light beam and transmits the second light beam, The dichroic surface is arranged on the plane.

17. The optical component according to claim 16, wherein The first optical element is a dichroic prism having the dichroic surface.

18. The optical component according to claim 12, wherein The first light beam has a first polarization state, The second light beam has a second polarization state, The first optical element has a polarizing beam splitter surface that reflects the first light beam and transmits the second light beam. The polarizing beam splitter surface is arranged on the plane.

19. A measurement system, wherein: have: The imaging device according to any one of claims 1 to 9; and A heating device heats the object.

20. A measurement system, wherein: have: The imaging device according to any one of claims 1 to 9; and The lighting device emits lighting light for illuminating the subject.

Images