Image pickup system

Abstract

The invention provides an imaging system capable of obtaining a captured image with reduced noise. An imaging system includes: a light source that emits infrared rays; an imaging device that captures an image of a subject irradiated with the infrared rays emitted from the light source; and a first polarization filter that is provided between the light source and the subject and polarizes the infrared rays emitted from the light source. The imaging device includes, from an incident side, a lens, a second polarization filter that polarizes infrared rays, and an image sensor.

Description

Technical Field

[0001] This invention relates to a camera system that uses infrared light to photograph a subject, and more particularly to a camera system having a polarizing filter that polarizes infrared light. Background Technology

[0002] In recent years, considering the multifunctionality and space-saving aspects of the device, devices that combine visible light-oriented devices such as display elements for displaying images and visible light imaging elements for capturing visible light with infrared light sensing systems have been developed.

[0003] For example, Patent Document 1 describes a camera system for capturing images of a scene, comprising: a camera having an image sensor for capturing images of the scene in both the visible wavelength range and the infrared wavelength range; at least one light source configured to emit light for selectively illuminating the scene with infrared radiation during image capture by the camera; and an electrically controlled filter configured to allow infrared wavelength light to be transmitted to the image sensor, while visible light is selectively transmitted or filtered based on a control signal so that it can be received by the image sensor. The electrically controlled filter includes a polarizing filter. Previous technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2022-123858 Summary of the Invention The technical problem to be solved by the invention

[0005] The imaging system of the aforementioned patent document 1 includes a polarizing filter, but noise exists in the captured image, and it is desirable to reduce the noise. The purpose of this invention is to provide a camera system that can obtain camera images with reduced noise. means for solving technical problems

[0006] In order to achieve the above objectives, the invention [1] is a camera system having: a light source that emits infrared light; a camera device that captures a subject irradiated by infrared light emitted from the light source; and a first polarizing filter disposed between the light source and the subject to polarize the infrared light emitted from the light source, wherein the camera device has a lens, a second polarizing filter that polarizes the infrared light and an image sensor on the incident side.

[0007] Invention [2] is the camera system described in Invention [1], wherein the first polarizing filter includes a first linear polarizer, the second polarizing filter includes a second linear polarizer, and the polarization axis of the first linear polarizer is orthogonal to the polarization axis of the second linear polarizer. Invention [3] is the camera system described in invention [1] or [2], wherein the second line polarizer is an absorption type line polarizer. Invention [4] is the camera system described in invention [2] or [3], wherein the average transmittance of the second line polarizer to visible light is 70% or more.

[0008] Invention [5] is the imaging system described in invention [1] or [4], wherein the second polarizing filter is an optical element having an absorption axis for infrared light in the in-plane direction, and when linearly polarized light of infrared light orthogonal to the absorption axis is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at a direction tilted 45° relative to the normal direction, the absorbance is greater when irradiated from the normal direction than when irradiated from the normal direction. Invention [6] is the camera system described in any one of inventions [1] to [5], wherein the haze of the second polarizing filter is 1 or less. Invention [7] is a camera system as described in any one of inventions [1] to [6], wherein the subject is at least one of the vehicle driver and the vehicle occupant, and the camera system is used for an in-vehicle occupant monitoring system.

[0009] The invention [8] is a camera system comprising: a light source emitting infrared light; a camera device for photographing a subject irradiated by infrared light emitted from the light source; and a first polarizing filter disposed between the light source and the subject to polarize the infrared light emitted from the light source. The camera device includes a second polarizing filter, a lens, and an image sensor on the incident side to polarize the infrared light. The second polarizing filter is an optical element having an absorption axis for infrared light in the in-plane direction. When linearly polarized light orthogonal to the absorption axis is irradiated from the normal direction of the optical element and from a direction inclined at 45° relative to the normal direction at an azimuth angle orthogonal to the absorption axis, the absorbance is greater when irradiated from the direction inclined at 45° relative to the normal direction than when irradiated from the normal direction. The invention [9] is a camera system comprising: a light source that emits infrared light; a camera device for photographing a subject irradiated by infrared light emitted from the light source; and a first circularly polarizing filter disposed between the light source and the subject to circularly polarize the infrared light emitted from the light source. The camera device, from the incident side, comprises a second circularly polarizing filter, a lens, and an image sensor to circularly polarize the infrared light. Invention

[10] is the camera system described in invention [9], wherein the second circular polarizing filter includes a linear polarizer and a λ / 4 plate, the Nz factor of the λ / 4 plate being greater than 0 and less than 1. Invention

[11] is the camera system described in invention

[10] , wherein the linear polarizer of the second circular polarizing filter is an absorption type linear polarizer. Invention

[12] is the camera system described in invention

[10] or

[11] , wherein the linear polarizer of the second circular polarizing filter has an average transmittance of more than 70% for visible light. Invention

[13] is the camera system described in invention [9], wherein the haze of the second polarizing filter is less than 1. Invention Effects

[0010] According to the present invention, a camera system is provided that can obtain camera images with reduced noise. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating a first example of a camera system according to an embodiment of the present invention. Figure 2 This is a schematic diagram showing the polarization axes of the first polarizing filter and the second polarizing filter in a first example of a camera system according to an embodiment of the present invention. Figure 3 This is a side view showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 4 This is a top view of the first layer, showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 5 This is a schematic cross-sectional view of the first layer of another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 6 This is a top view of the second layer of a camera system according to an embodiment of the present invention, showing another example of the second polarizing filter. Figure 7 This is a schematic cross-sectional view of the second layer of another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 8 This is a schematic perspective view illustrating, in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention, the situation where linearly polarized light, which is orthogonal to the absorption axis of infrared rays existing in the in-plane direction, is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at 45° relative to the normal direction. Figure 9 This is a schematic diagram illustrating the mechanism of S / N ratio improvement in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 10 This is a top view showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 11 This is a cross-sectional view showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 12 This is a schematic perspective view illustrating, in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention, the situation where linearly polarized light, which is orthogonal to the absorption axis of infrared rays existing in the in-plane direction, is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at 45° relative to the normal direction. Figure 13 This is a schematic diagram illustrating the mechanism of S / N ratio improvement in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 14 This is a schematic diagram illustrating a second example of a camera system according to an embodiment of the present invention. Figure 15 This is a schematic diagram illustrating an example of an in-vehicle occupant monitoring system using a camera system according to an embodiment of the present invention. Figure 16 This is a schematic diagram illustrating an example of the structure of an in-vehicle occupant monitoring system. Figure 17 This is a schematic diagram illustrating the camera system used in the embodiment. Detailed Implementation

[0012] Hereinafter, the camera system of the present invention will be described in detail with reference to the preferred embodiments shown in the accompanying drawings. Furthermore, the figures described below are merely illustrative of the invention, and the invention is not limited to the figures shown below. Additionally, the "~" sign indicating a numerical range includes the values ​​listed on either side. For example, ε represents the numerical value ε. α ~ numerical value ε β This means that the range of ε includes the value ε. α sum of values ​​ε β The range of , if expressed in mathematical notation, is ε. α ≤ε≤ε β . Unless otherwise specified, "parallelism" includes the range of errors typically allowed in the relevant technical field. Furthermore, unless otherwise specified, the angle, temperature, and time also include the error range that is generally permissible in the relevant technical field. Furthermore, "visible light" refers to light with a wavelength greater than 400 nm and less than 700 nm. Infrared light refers to light with a wavelength of 700nm or more and less than 2500nm. "Ultraviolet light" refers to light with a wavelength of 10 nm or more and less than 400 nm.

[0013] [Example 1 of a camera system] Figure 1This is a schematic diagram illustrating a first example of a camera system according to an embodiment of the present invention. Figure 1 The camera system 10 shown includes: a light source 12 that emits infrared light; a camera device 14 that captures a subject 13 irradiated by infrared light emitted from the light source 12; and a first polarizing filter 16 disposed between the light source 12 and the subject 13 to polarize the infrared light emitted from the light source 12. The imaging device 14 includes a lens 20, a second polarizing filter 24 for polarizing infrared light, a lens 22, and an image sensor 26 on the incident side. The lens 20, the second polarizing filter 24, the lens 22, and the image sensor 26 are arranged at intervals from each other in the optical axis direction. The optical system 27 consists of two lenses 20 and 22 and a second polarizing filter 24. The two lenses 20 and 22 are, for example, convex lenses. Therefore, light incident on lens 20 is converted into quasi-parallel light between lens 20 and lens 22 along the optical axis. Furthermore, lens 22 converges the light onto image sensor 26. That is, lens 22 images the light incident on lens 22 onto image sensor 26. Therefore, the light-receiving surface of image sensor 26 (not shown) is positioned at the focal point of lens 22.

[0014] The camera system 10 also includes a display control unit 17, a control unit 18, and a display unit 19 connected to the image sensor 26. The control unit 18 controls the light source 12, the image sensor 26, and the display control unit 17. The control unit 18 controls the light intensity of the light source 12 and its switching on / off state. Furthermore, the control unit 18 controls the switching on / off state of the image sensor 26. As described later, the image sensor 26 acquires an image signal carrying information about the subject 13, and this image signal constitutes a captured image. The display control unit 17 displays the captured image based on the image signal acquired by the image sensor 26 on the display unit 19. The display of the captured image from the display control unit 17 to the display unit 19 is controlled by the control unit 18.

[0015] Display unit 19 displays images captured by image sensor 26, using various known displays such as liquid crystal displays or organic EL (Electro Luminescence) displays.

[0016] Light source 12 emits infrared light as emitted light Lo. The structure of light source 12 is not particularly limited as long as it can emit infrared light. Light source 12 uses light-emitting elements such as LEDs (Light Emitting Diodes) and LDs (Laser Diodes).

[0017] A first polarizing filter 16 is disposed on the emission side of the light source 12. The surface of the first polarizing filter 16 on the light source 12 side is the back surface 16b, and the surface on the opposite side is the surface 16a. As described above, the first polarizing filter 16 can be positioned anywhere between the light source 12 and the subject 13, as long as it can polarize the infrared light emitted from the light source 12. In the case of diffusion of the emitted light Lo from the light source 12, it is preferable to position the first polarizing filter 16 between the light source 12 and the subject 13, on the side closer to the light source 12.

[0018] In the imaging device 14, for example, two lenses 20 and 22 are arranged at intervals along the optical axis, respectively aligned with the optical axis C. A second polarizing filter 24 is disposed between lenses 20 and 22. Furthermore, the optical axis direction refers to the direction in which the optical axis C extends. Polarized outgoing light Lo is incident on the subject 13, and reflected light Li, reflected by the subject 13, is incident on the lens 20 on the incident side. The reflected light Li is the light carrying the information of the subject 13. Between lens 20 and lens 22, the reflected light Li incident on lens 20 is converted into quasi-parallel light. After being polarized by the second polarizing filter 24, the reflected light Li is converged by lens 22 and imaged onto the light-receiving surface (not shown) of image sensor 26. An image signal carrying information about the subject 13 is obtained through image sensor 26, and this image signal constitutes a captured image.

[0019] In the image sensor 26, light carrying information about the subject 13 is received by, for example, the light-receiving surface, and converted into an electrical signal through photoelectric conversion, thereby obtaining an image signal carrying information about the subject 13. Thus, the subject 13 is captured. As described above, the image sensor 26 has a photoelectric conversion function, for example, it has a conventionally known photoelectric conversion element. The image sensor 26 can be, for example, a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Furthermore, the image sensor 26 preferably has sensitivity in the visible light region in addition to infrared light. Therefore, it is possible to obtain images based on both infrared light and the visible light region. As described above, the image signal carrying information about the subject 13 obtained by the image sensor 26 is output to the display control unit 17 and displayed on the display unit 19.

[0020] In the camera system 10, a lens 20, a second polarizing filter 24 for polarizing infrared light, and an image sensor 26 are provided on the incident side. The second polarizing filter 24 polarizes the reflected light Li that passes through the lens 20. Therefore, the probability that light obliquely incident on the lens 20 is refracted when passing through the lens 20 and obliquely incident on the second polarizing filter 24 is reduced, thereby reducing the noise in the acquired image and obtaining an image with reduced noise. On the other hand, when a second polarizing filter 24 is disposed between the lens 20 and the subject 13, for example at position Pj, light in the reflected light Li that deviates from the polarization axis of the second polarizing filter 24 (e.g., light obliquely incident on the second polarizing filter 24) will pass through the second polarizing filter 24. As a result, light that should be blocked by the second polarizing filter 24 obliquely incidents onto the lens 20. Due to the obliquely incident light, noise is generated in the captured image. On the other hand, in the camera system, as described above, the generation of noise generated when the second polarizing filter 24 is disposed at position Pj is suppressed. Furthermore, the position Pj where the second polarizing filter 24 is disposed is referred to as the subject-side position.

[0021] Furthermore, in the imaging system 10, the second polarizing filter 24 is positioned between the two lenses 20 and 22 along the optical axis, but it is not limited to this. For example, it can be positioned between the image sensor 26 and the lens 22 opposite to the image sensor 26. The position between the two lenses 20 and 22 along the optical axis is referred to as the pupil position. Furthermore, the position between the image sensor 26 and the lens 22 opposite to the image sensor 26 along the optical axis is referred to as the image-side position. The second polarizing filter 24 can be positioned between the pupil position and the image side position. The pupil position is closer to parallel light, so from the viewpoint of reducing noise, the pupil position is preferred. On the other hand, from the viewpoint of ease of placement of the second polarizing filter 24, the image side position is preferred over the pupil position.

[0022] Furthermore, in Figure 1 In the imaging system 10 shown, instead of the second polarizing filter 24 described above, the imaging device 14 may also have a structure that includes a second polarizing filter 30 for polarizing infrared light, a lens 20, and an image sensor 26 from the incident side. In this case, the second polarizing filter 24 is not provided, and the second polarizing filter 30 is disposed on the incident surface 20a side of the lens 20. The second polarizing filter 30 is an optical element having an absorption axis for infrared radiation in the in-plane direction. When linearly polarized infrared light orthogonal to the absorption axis is irradiated from both the normal direction of the optical element and from a direction tilted at 45° relative to the normal direction at an azimuth angle orthogonal to the normal direction, the absorbance is greater when irradiated from the direction tilted at 45° relative to the normal direction compared to the absorbance when irradiated from the normal direction. Further details regarding the second polarizing filter 30 will be provided later. Figure 8 Please provide an explanation.

[0023] Furthermore, the camera system 10 is configured with two lenses 20 and 22, but the number of lenses is not limited to two. Lens 20 and lens 22 are not limited to single lenses. For example, lens 20 and lens 22 can be configured as a lens group with multiple lenses or a combination lens with multiple lenses and optical elements, etc. When configured as a lens group or combination lens, the second polarizing filter 24 is positioned between the lens group or combination lens and the lens group or combination lens in the optical axis direction. Furthermore, the lenses 20 and 22 of the camera system 10 can also be configured as movable lenses that can move along the optical axis and have optical zoom or focusing functions.

[0024] Next, the first polarizing filter 16 and the second polarizing filter 24 will be described. Figure 2 This is a schematic diagram showing the polarization axes of the first polarizing filter and the second polarizing filter in a first example of a camera system according to an embodiment of the present invention. exist Figure 2 The first polarizing filter 16 and the second polarizing filter 24 are shown in the figure. The first polarizing filter 16 includes, for example, a first linear polarizer 28. The first linear polarizer 28 has a polarization axis D1. In this case, the first polarizing filter 16 is a linear polarizing filter. The second polarizing filter 24 includes a second linear polarizer 29. The second linear polarizer 29 has a polarization axis D2. In this case, the second polarizing filter 24 is a linear polarizing filter. The directions of the polarization axes D1 and D2 are the directions of the linearly polarized light. Although not illustrated, the first polarizing filter 16 may include a first linear polarizer 28 and the second polarizing filter 24 may include a second linear polarizer 29, but they may also have a structure with an optical compensation layer.

[0025] like Figure 2As shown, when the first linear polarizer 28 and the second linear polarizer 29 are observed from the back surface 16b of the first polarizing filter 16 on the light source 12 side and the back surface 24b of the second polarizing filter 24 on the image sensor 26 side, the polarization axis D1 of the first linear polarizer 28 is orthogonal to the polarization axis D2 of the second linear polarizer 29. In this case, the infrared light emitted from the light source 12 becomes linearly polarized infrared light through the first linear polarizer 28, and the linearly polarized infrared light, i.e., the emitted light Lo, illuminates the subject 13. The linearly polarized infrared light is reflected by the subject 13. The linearly polarized infrared light reflected by the subject 13, i.e., the reflected light Li, passes sequentially through the lens 20, the second linear polarizer 29, and the lens 22, and then enters the image sensor 26. At this time, in the second linear polarizer 29, the linearly polarized light that is aligned with the polarization axis D1 of the first linear polarizer 28 in the linearly polarized infrared light reflected by the subject 13 is blocked. Therefore, the reflected light that maintains a linear polarization state in the reflected light Li can be removed. As a result, the noise in the captured image is reduced. For example, in the case of capturing a human face, the reflected light caused by the unevenness of the face can be removed, thus obtaining a high-quality captured image of the human face. Therefore, the camera system is suitable for, for example, driver monitoring systems, eye tracking systems, and vein authentication systems. The unevenness of the face also includes things like glasses.

[0026] As mentioned above, when using linearly polarized light, in Figure 1 When the second polarizing filter 24 is positioned at location Pj, light that deviates from the polarization axis of the second polarizing filter 24 passes through it, thus allowing reflected light that remains linearly polarized to pass through. This results in noise in the captured image. On the other hand, in the imaging system, even when using linearly polarized light, the second polarizing filter 24 is positioned at the aforementioned pupil position or image side position. Therefore, even if reflected light Li is incident on the lens 20 from an oblique direction, light that deviates from the polarization axis of the second polarizing filter 24 can be suppressed from incident on the second polarizing filter 24. Thus, as described above, the generation of noise generated when the second polarizing filter 24 is positioned at position Pj can be suppressed, resulting in a captured image with reduced noise.

[0027] The second line polarizer 29 is preferably an absorptive line polarizer. As a result, since reflections in the imaging device 14 are suppressed, noise in the captured image can be further reduced. The average transmittance of the second-line polarizer 29 for visible light is preferably 70% or higher. This allows for the acquisition of clear images in the visible light region. The average transmittance of visible light is more preferably 80% or more, and even more preferably 90% or more. There is no particular upper limit, for example, it can be 99% or less. In addition, the average transmittance of visible light is the average transmittance of all wavelengths in the entire visible light region, and can be measured using a spectrophotometer. More specifically, the average transmittance of the second-line polarizer to visible light is obtained by measuring the transmittance of the second-line polarizer per 1 nm in the wavelength range of 400 nm to less than 700 nm using a UV-Vis-NIR spectrophotometer (e.g., a V-660 UV-Vis-NIR spectrophotometer (JASCO Corporation)), and then arithmetically averaging the transmittance at each wavelength. Furthermore, the haze of the second polarizing filter 24 is preferably 1 or less. This suppresses reflections in the imaging device 14, thereby further reducing noise in the captured image. Additionally, the lower limit for haze is 0.1. The haze of the second polarizing filter 24 can be measured using a haze meter.

[0028] As described above, the imaging system 10 is not limited to a structure that utilizes linearly polarized light, where the first polarizing filter 16 includes a first linear polarizer 28 and the second polarizing filter 24 includes a second linear polarizer 29. For example, circularly polarized light can also be used. In this case, the first polarizing filter 16 is a structure that includes a first linear polarizer 28 and a λ / 4 plate. The slow axis of the λ / 4 plate is tilted at 45° ± 10° relative to the polarization axis D1 of the first linear polarizer 28. This results in circularly polarized light. The second polarizing filter 24 is a structure that includes a second linear polarizer 29 and a λ / 4 plate. The slow axis of the λ / 4 plate is tilted at 45° ± 10° relative to the polarization axis D2 of the second linear polarizer 29. This produces circularly polarized light. The λ / 4 plate is the plate with respect to the wavelength λ of the incident light, and the emitted light becomes the plate with a wavelength of λ / 4. In the case of circularly polarized light, if reflection occurs, the rotation direction of the circularly polarized light is reversed. Therefore, if the circularly polarized light reflected by the subject 13 through the first polarizing filter 16 is right-handed circularly polarized infrared light, it becomes left-handed circularly polarized light, and the rotation direction is reversed. Therefore, in order to block left-handed circularly polarized light, the second polarizing filter 24 is designed with the same structure as the first polarizing filter 16.

[0029] [λ / 4 board] As a λ / 4 plate, any phase retardation element having a phase retardation amount equivalent to 1 / 4 wavelength in a specified wavelength region can be used without limitation. Examples include inorganic phase retardation plates, polymer-stretched phase retardation plates, liquid crystal phase retardation plates formed by fixing liquid crystal compounds or polymeric liquid crystal compounds in an oriented state, and metasurface phase retardation plates. Here, having a phase retardation amount equivalent to 1 / 4 wavelength means that Re(550) is in the range of 120 nm to 160 nm. When acting on a visible light beam, it is preferable to exhibit a 1 / 4 wavelength characteristic over a wide bandwidth, and its wavelength dispersion is preferably a so-called inverse wavelength dispersion that shows the relationship Re(450) < Re(550) ≤ Re(650). As a λ / 4 plate, it can be a single-layer thin film or sheet, or its properties can be achieved by stacking multiple thin films or sheets. Furthermore, it can be combined with a retardation plate using twisted-aligned liquid crystal or mixed-aligned liquid crystal to display the properties of the λ / 4 plate only for specific polarized light.

[0030] Furthermore, the λ / 4 plate is a phase retardation plate that functions to convert linearly polarized light of a specific wavelength into circularly polarized light (or vice versa). More specifically, it is a plate whose in-plane delay Re at a specified wavelength λ nm is expressed as λ / 4 (or an odd multiple thereof). In this example, the λ / 4 plate functions as a λ / 4 plate for infrared light of wavelength λ emitted from light source 12. Additionally, the in-plane delay Re(λ) of the λ / 4 plate can have an error of approximately 25 nm centered on the ideal value (λ / 4 nm).

[0031] The λ / 4 plate can be composed of a single retardation layer, or it can be constructed by laminating two or more retardation layers using methods such as bonding or sequential formation. The retardation layer referred to here is a layer that exhibits optical anisotropy. Examples of retardation layers include at least two different layers selected from nx, ny, and nz. Furthermore, nx represents the refractive index in the direction perpendicular to the thickness direction of the retardation layer (in-plane direction) and imparting the maximum refractive index. ny represents the refractive index in the direction perpendicular to the in-plane direction of the retardation layer and orthogonal to the nx direction. nz represents the refractive index in the thickness direction of the retardation layer. The λ / 4 plate can also have a support structure to support the retardation layer.

[0032] The materials constituting the retardation layer are not particularly limited, and examples include liquid crystal compounds and polymers. Liquid crystal compounds can form a retardation layer by aligning liquid crystal materials to exhibit refractive index anisotropy. Polymers can form a retardation layer by stretching or otherwise exhibiting refractive index anisotropy in polymer films obtained through casting and coating. From a thinning perspective, the retardation layer is preferably a layer formed using a liquid crystal compound, and more preferably a layer formed using a liquid crystal compound having polymerizable groups.

[0033] The type of liquid crystal compound is not particularly limited. Generally, liquid crystal compounds can be classified according to their shape into rod-shaped types (rod-shaped liquid crystal compounds) and disc-shaped types (disc-shaped liquid crystal compounds). Furthermore, liquid crystal compounds can be classified into low-molecular-weight types and high-molecular-weight types. High-molecular-weight compounds generally refer to molecules with a degree of polymerization of 100 or higher (Polymer Physics and Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992). In this invention, any liquid crystal compound can be used, but rod-shaped or disc-shaped liquid crystal compounds are preferred, and rod-shaped liquid crystal compounds are more preferred. Two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or mixtures of rod-shaped and disc-shaped liquid crystal compounds can be used.

[0034] Furthermore, examples of rod-shaped liquid crystal compounds include those described in claim 1 of Japanese Patent Application Publication No. 11-513019 and paragraphs 0026 to 0098 of Japanese Patent Application Publication No. 2005-289980. Examples of disc-shaped liquid crystal compounds include those described in paragraphs 0020 to 0067 of Japanese Patent Application Publication No. 2007-108732 and paragraphs 0013 to 0108 of Japanese Patent Application Publication No. 2010-244038.

[0035] The liquid crystal compound preferably has polymerizable groups. That is, the liquid crystal compound is preferably a polymerizable liquid crystal compound. When the liquid crystal compound has polymerizable groups, the orientation state of the liquid crystal compound can be easily fixed by the curing treatment described later. There is no particular limitation on the type of polymerizable groups contained in the liquid crystal compound, but functional groups capable of addition polymerization are preferred, polymerizable olefinic unsaturated groups or cyclic polymerizable groups are more preferred, and (meth)acryloyl, vinyl, styrene, or allyl are even more preferred. There is no particular limitation on the number of polymerizable groups contained in the liquid crystal compound, but two or more are preferred. There is no particular upper limit, but it is mostly 10 or less.

[0036] The liquid crystal compound forming the phase retardation layer preferably comprises a liquid crystal compound represented by the following general formula (1).

[0037] [Chemical Formula 1]

[0038] Here, in equation (1), D <link> independently represents a single bond or -CO-, -O-, -S-, -C(=S)-, -CR 1 R 2 -、-CR 3 =CR 4 -、-NR 5 - or a divalent linking group consisting of two or more of them, R1 ~R 5 Each can be an alkyl group, representing a hydrogen atom, a fluorine atom, or a carbon atom numbering 1 to 12, respectively.

[0039] A 1 and A 2 <Rigid ring> independently represents an aromatic hydrocarbon ring that may have substituents, an aromatic heterocycle that may have substituents, or a divalent alicyclic hydrocarbon group that may have substituents. Among them, one or more of the -CH2- constituting the alicyclic hydrocarbon group can be substituted by -O-, -S-, or NH-.

[0040] SP 1 and SP 2 <Flexible chain> independently represents a single bond or a divalent aliphatic hydrocarbon group with 1 to 20 carbon atoms that may have substituents. In this case, one or more methylene groups constituting the aliphatic hydrocarbon group may be substituted with -O-, -S-, -NH-, -N(Q)-, or CO-. Q represents a substituent.

[0041] L 1 and L 2 <Terminal group> independently represents a monovalent organic group, L 1 and L 2 At least one of them represents a polymerizable group. n represents an integer greater than or equal to 0.

[0042] Specific examples of thermotropic liquid crystals are shown in International Publication Nos. 2022 / 215757,

[0129] to

[0249] .

[0043] The liquid crystal compound can be either a liquid crystal compound exhibiting positive wavelength dispersion or negative wavelength dispersion. In the case of a phase retardation layer that utilizes the characteristics of a single-film display of a broadband λ / 4 plate, a liquid crystal compound exhibiting so-called negative wavelength dispersion, in which the phase difference increases with increasing wavelength, is preferred; more preferably, a liquid crystal compound having two or more polymerizable groups and exhibiting negative wavelength dispersion is preferred.

[0044] The λ / 4 plate preferably satisfies the following formula. 0.50<Re(450) / Re(550)<1.00

[0045] Furthermore, when the phase retardation layer is a layer formed using a liquid crystal composition containing a liquid crystal compound, the liquid crystal composition may contain surfactants, polymerization initiators, crosslinking agents, and other additives in addition to the aforementioned liquid crystal compound.

[0046] The surfactant is preferably a compound that can function as an orientation control agent, which helps to stabilize or rapidly orient the cholesterol-type liquid crystal phase. Examples of surfactants include silicone-based and fluorinated surfactants. Furthermore, non-fluorinated surfactants are also preferred.

[0047] As a non-fluorinated surfactant, it is preferred to contain siloxane units or long-chain alkyl groups.

[0048] As described above, the retardation layer is preferably a layer formed using a liquid crystal compound having polymerizable groups, and more preferably a layer formed by fixing the orientation state of the liquid crystal compound having polymerizable groups. There are no particular limitations on the preferred orientation state of the liquid crystal compound having polymerizable groups; examples include uniform orientation, vertical orientation, twisted orientation, cholesterol-type orientation, mixed orientation (an orientation in which the tilt angle of the liquid crystal compound changes continuously from one surface to another), and tilted orientation (an orientation in which the tilt angle of the liquid crystal compound is constant from one surface to another). Furthermore, twisted orientation refers to an orientation in which the liquid crystal compound is twisted about its thickness direction as a rotation axis. When the liquid crystal compound is twisted and has a predetermined tilt angle (tilt angle greater than 0°), it is considered a twisted mixed orientation. In this specification, twisted orientation corresponds to a liquid crystal compound with a twist angle less than 360°, and cholesterol-type orientation corresponds to a liquid crystal compound with a twist angle of 360° or more.

[0049] Furthermore, the "fixed" state is the most typical and preferred state in which the orientation of the liquid crystal compound is maintained. It is not limited to this. Specifically, it is more preferred that the liquid crystal compound has no fluidity in the layer and can stably maintain the fixed orientation without the orientation shape changing due to external fields or external forces within a temperature range of -30 to 70°C under more severe conditions.

[0050] A retardation layer formed using liquid crystal compounds can have multiple regions along its thickness direction with different orientation states of the liquid crystal compounds. For example, the retardation layer can have regions where the liquid crystal compounds are uniformly oriented along the thickness direction and regions where the liquid crystal compounds are twistedly oriented.

[0051] There is no particular limitation on the thickness of the phase retardation layer, but it is preferably 0.1 to 10.0 μm, more preferably 0.5 to 5.0 μm.

[0052] The λ / 4 plate can be composed of a single phase retardation layer or two or more phase retardation layers stacked together. For example, it can be a structure composed of a combination of λ / 4 and λ / 2 phase retardation layers. Furthermore, in order to compensate for the phase difference change of incident light relative to the tilt direction, other phase retardation layers such as positive C-plates and negative C-plates can be added.

[0053] Here, the Nz factor of the λ / 4 plate is preferably greater than 0 and less than 1, more preferably 0.2 to 0.7, even more preferably 0.3 to 0.6, and even more preferably 0.5. The Nz factor refers to the value given by Nz = (nx - nz) / (nx - ny) using the refractive index nx along the slow axis in the plane, the refractive index ny in the direction orthogonal to the slow axis in the plane, and the refractive index nz in the thickness direction. The refractive index nx along the slow axis in the plane, the refractive index ny in the direction orthogonal to the slow axis in the plane, and the refractive index nz in the thickness direction can be measured using an AxoScan or an Abbe refractometer, etc.

[0054] By setting the Nz factor of the λ / 4 plate to be greater than 0 and less than 1, it is possible to compensate for the phase difference variation relative to light incident from an oblique direction. For example, infrared light diverging from the lens and incident on the λ / 4 plate is incident from a direction approximately perpendicular to the λ / 4 plate near the center (the position through which the optical axis of the lens passes). Therefore, the λ / 4 plate produces an effect that appropriately imparts a λ / 4 phase difference to the incident infrared light. In contrast, at positions far from the center, the infrared light is incident at an oblique direction relative to the λ / 4 plate, i.e., the angle (polar angle) with respect to the perpendicular line to the surface of the λ / 4 plate exceeds 0°. Therefore, when the Nz factor is 0, the phase difference provided relative to the incident infrared light will deviate from λ / 4, and the converted infrared light may become elliptically polarized light. Therefore, by setting the Nz factor to be greater than 0 and less than 1, the phase difference imparted to the infrared light incident on the λ / 4 plate from an oblique direction can be set to λ / 4, and the incident infrared light can be appropriately converted into circularly polarized light.

[0055] Furthermore, both the first polarizing filter 16 and the second polarizing filter 24 can use polarizers having cholesterol-type liquid crystal layers. In this case, the first polarizing filter contains a first cholesterol-type liquid crystal layer, and the second polarizing filter contains a second cholesterol-type liquid crystal layer. The first and second cholesterol-type liquid crystal layers reflect light in the same direction of rotation.

[0056] Figure 3 This is a side view showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 4 This is a top view of the first layer, showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 5 This is a schematic cross-sectional view of the first layer, showing another example of the second polarizing filter in the imaging system according to an embodiment of the present invention. Additionally, Figure 5 yes Figure 4 A sectional view taken along line A-A. Figure 6 This is a top view of the second layer of a camera system according to an embodiment of the present invention, showing another example of the second polarizing filter. Figure 7 This is a schematic cross-sectional view of the second layer, showing another example of the second polarizing filter in the imaging system according to an embodiment of the present invention. Additionally, Figure 7 yes Figure 6 A sectional view taken along line A-A. Figure 8 This is a schematic perspective view illustrating, in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention, the situation where linearly polarized light, which is orthogonal to the absorption axis of infrared rays existing in the in-plane direction, is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at 45° relative to the normal direction. Figure 9 This is a schematic diagram illustrating the mechanism of improved S (signal) / N (noise) ratio in another example of the second polarizing filter of the camera system according to an embodiment of the present invention.

[0057] Furthermore, the second polarizing filter 30 is, for example, an optical element with a structure having a first layer 32 and a second layer 34 stacked together. As described later, the first layer 32 and the second layer 34 contain infrared-absorbing dichroic materials with different orientation states.

[0058] exist Figure 4 In this context, direction X and direction Y represent the directions of two coordinate axes that are orthogonal to each other on the observation plane. Figure 5 In the diagram, direction X and direction Z represent the directions of two coordinate axes orthogonal to each other on the observation plane. Direction Z is parallel to the thickness direction of layer 1, 32. like Figure 4 and Figure 5 As shown, the first layer 32 contains infrared-absorbing dichroic material N inside. And, as Figure 4 and Figure 5 As shown, in layer 1, 32, the long axis of the infrared-absorbing dichroic substance N is along the Y-axis direction ( Figure 4 Arranged vertically on the paper. Therefore, in the first layer 32, there is an absorption axis for infrared radiation in the Y-axis direction in the in-plane direction.

[0059] exist Figure 6 In this context, direction X and direction Y represent the directions of two coordinate axes that are orthogonal to each other on the observation plane. Figure 7In the diagram, direction X and direction Z represent the directions of two coordinate axes orthogonal to each other on the observation plane. Direction Z is parallel to the thickness direction of layer 34 in the second layer. like Figure 6 and Figure 7 As shown, the second layer 34 contains infrared-absorbing dichroic material N inside. And, as Figure 6 and Figure 7 As shown, in layer 2, 34, the long axis of the infrared-absorbing dichroic substance N is along the Z-axis direction ( Figure 7 (The paper is arranged vertically). Therefore, in the second layer 34, there is an absorption axis for infrared radiation in the Z-axis direction (i.e., the thickness direction) in the in-plane direction.

[0060] The second polarizing filter 30 includes a first layer 32 having an absorption axis for infrared radiation in the in-plane direction and a second layer 34 having an absorption axis for infrared radiation in the thickness direction. like Figure 8 As shown, the second polarizing filter 30 has an absorption axis originating from the first layer 32 along the Y-axis in the in-plane direction. That is, it has an absorption axis in the direction indicated by the thin black arrow. Next, the characteristics of linearly polarized infrared light orthogonal to the absorption axis when irradiating the second polarizing filter 30 will be explained. First, in the second polarizing filter 30, the orientation of the linearly polarized infrared light orthogonal to the absorption axis corresponds to the X-axis direction. In the second polarizing filter 30, light incident on... Figure 8 The second layer 34, shown on the surface 34a, exits from the back surface 32b of the first layer 32. like Figure 8 As indicated by the hollow arrow, when the linearly polarized light is irradiated from the normal direction of the second polarizing filter 30, the absorption axis of the second layer 34 is parallel to the thickness direction and orthogonal to the absorption axis of the first layer 32, so it is almost not absorbed and is transmitted. In contrast, at an azimuth angle orthogonal to the absorption axis of the second polarizing filter 30 ( Figure 8 The azimuth angle (represented by the dashed line) is tilted 45° relative to the normal direction from the direction of the azimuth. Figure 8 When linearly polarized infrared light (in the direction of the thick black arrow) is irradiated, the absorption axes of the first layer 32 and the second layer 34 are in a cross-Nicolasian cross state. Therefore, the light incident from the direction of the thick black arrow is almost absorbed and not transmitted in the second polarizing filter 30. In other words, the second polarizing filter 30 is an optical element whose absorbance of light incident from the normal direction is greater than that of light incident from a direction tilted at 45° relative to the normal direction. Therefore, this second polarizing filter 30 has the function of allowing light incident from the normal direction to pass through well, but not allowing light incident from the oblique direction to pass through.

[0061] Therefore, as described above, the effects caused by stray light are suppressed by using a second polarizing filter 30, which includes a first layer 32 having an absorption axis for infrared light in the in-plane direction and a second layer 34 having an absorption axis for infrared light in the thickness direction. The following uses Figure 9 Explain its mechanism. As described above, the second polarizing filter 30 has the function of allowing light incident from the normal direction to pass through well, but preventing light incident from the oblique direction from passing through. Therefore, in the second polarizing filter 30, light incident at an angle close to the normal direction on the surface 34a of the second layer 34 in the reflected light reflected by the subject 13 is transmitted from the back surface 32b of the first layer 32. However, stray light S incident on the surface 34a of the second layer 34 from the oblique direction is absorbed by the second polarizing filter 30. As a result, the S / N ratio of the second polarizing filter 30 is high.

[0062] Figure 10 This is a top view showing another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. Figure 11 This is a cross-sectional view showing another example of the second polarizing filter in the imaging system according to an embodiment of the present invention. Additionally, Figure 11 yes Figure 10 A sectional view taken along line B-B. Figure 12 This is a schematic perspective view illustrating, in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention, the situation where linearly polarized light, which is orthogonal to the absorption axis of infrared rays existing in the in-plane direction, is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at 45° relative to the normal direction. Figure 13 This is a schematic diagram illustrating the mechanism of S / N ratio improvement in another example of the second polarizing filter of the imaging system according to an embodiment of the present invention. The second polarizing filter 36 and Figure 3 Unlike the second polarizing filter 30 shown, it is a single-layer optical element, as described later, in which infrared-absorbing dichroic material is contained in a prescribed orientation state. exist Figure 10 In this context, direction X and direction Y represent the directions of two coordinate axes that are orthogonal to each other on the observation plane. Figure 11 In the diagram, directions Y and Z represent the directions of two coordinate axes orthogonal to each other on the observation plane. Direction Z is parallel to the thickness direction of the second polarizing filter 36. like Figure 10 and Figure 11As shown, the second polarizing filter 36 contains an infrared-absorbing dichroic substance N inside it. And, as Figure 10 As shown, in the in-plane direction of the second polarizing filter 36, the long axis of the infrared-absorbing dichroic substance N is along the Y-axis direction ( Figure 10 The filters are arranged in the plane of the paper (vertical direction). Therefore, the second polarizing filter 36 has an absorption axis for infrared radiation in the Y-axis direction, which is in the plane of the paper. And, as Figure 11 As shown, in the cross-section along the absorption axis, the infrared-absorbing dichroic material N is arranged in a disk shape. Therefore, in the cross-section along the infrared absorption axis in the in-plane direction of the second polarizing filter 36, there is no anisotropy in the absorption of infrared light.

[0063] As described above, the second polarizing filter 36 is composed of a single layer having an absorption axis for infrared light in the in-plane direction, and in the cross section along the absorption axis, it becomes an optical element that does not have anisotropy in the absorption of infrared light. like Figure 12 As shown, this second polarizing filter 36 has an absorption axis in the in-plane direction, specifically in the Y-axis direction, originating from the side surfaces of the infrared-absorbing dichroic material N arranged in a disk shape. In other words, it has an absorption axis in the direction indicated by the thin black arrow. Next, the characteristics of linearly polarized infrared light orthogonal to the absorption axis when irradiating the second polarizing filter 36 will be explained. First, in the second polarizing filter 36, the orientation of the linearly polarized infrared light orthogonal to the absorption axis corresponds to the X-axis direction. In the second polarizing filter 36, light incident on... Figure 12 The surface 36a is shown and it exits from the back side 36b.

[0064] like Figure 12 As indicated by the hollow arrow, when the linearly polarized light is irradiated from the normal direction of the second polarizing filter 36, it is orthogonal to the absorption axis and therefore is almost not absorbed and is transmitted. In contrast, at an azimuth angle orthogonal to the absorption axis of the second polarizing filter 36 ( Figure 5 The azimuth angle (represented by the dashed line) is tilted 45° relative to the normal direction from the direction of the azimuth. Figure 12 When linearly polarized infrared light (in the direction of the thick black arrow) is irradiated, there is no anisotropy in the absorption of infrared light on the cross section along the absorption axis. Therefore, the light incident from the direction of the thick black arrow is almost absorbed by the infrared-absorbing dichroic material N in the second polarizing filter 36 and is not transmitted. In other words, the second polarizing filter 36 is an optical element whose absorbance of light incident from the normal direction is greater than that of light incident from a direction tilted at 45° relative to the normal direction. Therefore, this second polarizing filter 36 has the function of allowing light incident from the normal direction to pass through well, but not allowing light incident from the oblique direction to pass through. Therefore, as Figure 13 As shown, in the second polarizing filter 36, light incident on surface 36a at an angle close to the normal direction from the reflected light reflected by the subject 13 is transmitted from the back surface 36b. However, stray light S incident on surface 36a from an oblique direction is absorbed by the second polarizing filter 36. As a result, the S / N ratio of the second polarizing filter 36 is high.

[0065] Furthermore, optical elements whose absorbance is greater when incident from the normal direction than when incident from a direction inclined at 45° relative to the normal direction are not limited to the above-described structure. For example, optical elements with limited viewing angles, such as venetian blinds or privacy films, can also be used. In this case, the venetian blinds or privacy films are not used alone, but are used, for example, on the incident side of the linear polarizer.

[0066] [Example 2 of a camera system] Figure 14 This is a schematic diagram illustrating a second example of a camera system according to an embodiment of the present invention. exist Figure 14 In the camera system 11 shown, for the... Figure 1 The same structures of the camera system 10 shown are labeled with the same symbols, and their detailed descriptions are omitted. and Figure 1 Compared to the imaging system 10 shown, the imaging system 11 differs in that it has a first circularly polarizing filter 60, disposed between the light source 12 and the subject 13, which circularly polarizes the infrared light emitted from the light source 12, instead of the first polarizing filter 16. Furthermore, compared to the second polarizing filter 24, the imaging device 14 differs in that it includes a second circularly polarizing filter 62, lenses 20 and 22, and an image sensor 26 on the incident side. In addition, the imaging system 11 is... Figure 1 The camera system 10 shown has the same structure. The first circularly polarizing filter 60 that circularly polarizes the aforementioned infrared light includes, for example, a linear polarizer 63 and a λ / 4 plate 64. In this case, similar to the first polarizing filter 16 described above, the slow axis of the λ / 4 plate 64 is tilted at 45° ± 10° relative to the polarization axis (not shown) of the linear polarizer 63. The linear polarizer 63 is positioned towards the light source 12. The surface 60a of the first circularly polarizing filter 60 is formed by the λ / 4 plate 64, and the back surface 60b is formed by the linear polarizer 63. In the first circularly polarized filter 60, the unpolarized infrared light incident on the linear polarizer 63 is converted into circularly polarized light and emitted from the surface 60a. The second circularly polarizing filter 62 that circularly polarizes the aforementioned infrared light preferably includes a linear polarizer 65 and a λ / 4 plate 66, and the Nz factor of the λ / 4 plate 66 is greater than 0 and less than 1. In this case, similar to the second polarizing filter 24 described above, the slow axis of the λ / 4 plate 66 is tilted at 45° ± 10° relative to the polarization axis (not shown) of the linear polarizer 65. The λ / 4 plate 66 of the second circularly polarizing filter 62 is positioned toward the incident surface 20a of the lens 20. The surface 62a of the second circularly polarizing filter 62 is formed by the linear polarizer 65, and the back surface 62b is formed by the λ / 4 plate 66. In the second circularly polarized filter 62, the unpolarized infrared light incident on the linear polarizer 65 is converted into circularly polarized light and emitted from the back side 62b. Furthermore, the phase difference imparted to infrared rays incident on the λ / 4 plate from the tilt direction can be set to λ / 4, thereby enabling the incident infrared rays to be appropriately converted into circularly polarized light.

[0067] In this case, the infrared light emitted from the light source 12 becomes circularly polarized infrared light after passing through the first circularly polarized filter 60, and the circularly polarized infrared light, i.e., the emitted light Lo, illuminates the subject 13. The circularly polarized infrared light is reflected by the subject 13. The circularly polarized infrared light reflected by the subject 13, i.e., the reflected light Li, passes sequentially through the second circularly polarized filter 62, lens 20, and lens 22 and is incident on the image sensor 26. At this time, in the second circularly polarized filter 62, the circularly polarized infrared light reflected by the subject 13 becomes linearly polarized light in the polarization axis direction of the linear polarizer 65 after passing through the linear polarizer 65. The linearly polarized light based on the linear polarizer 65 is converted into circularly polarized light by the λ / 4 plate 66. Therefore, the reflected light that retains the linear polarization state in the reflected light Li can be removed. As a result, the noise of the captured image is reduced. For example, in the case of capturing a human face, the reflected light caused by the unevenness of the face can be removed, and thus a high-quality captured image of the human face can be obtained. Therefore, the camera system 11 and Figure 1 Similarly, the camera system 10 shown is suitable for, for example, driver monitoring systems, eye-tracking systems, and vein authentication systems. Facial contours also include things like glasses.

[0068] Regarding the first circular polarizing filter 60 and the second circular polarizing filter 62, an example is shown that includes a linear polarizer and a λ / 4 plate, but it is not limited to this as long as it can make infrared light circularly polarized, and can also be composed of a single component. The linear polarizer 65 of the second circular polarizing filter 62 is disposed on the incident side, and is therefore preferably an absorption-type linear polarizer. This suppresses reflections on the surface 62a of the second circular polarizing filter 62, thereby further reducing noise in the captured image. The linear polarizer 65 of the second circular polarizing filter 62 preferably has an average visible light transmittance of 70% or more. This allows for the acquisition of a clear image in the visible light region. More preferably, the average visible light transmittance of the linear polarizer is 80% or more, and even more preferably 90% or more. There is no particular limitation on the upper limit; for example, it can be 99% or less. Furthermore, since the average visible light transmittance is as described above, its detailed description is omitted. Furthermore, the haze of the second circular polarizing filter 62 is preferably 1 or less. This suppresses reflections in the imaging device 14, thereby further reducing noise in the captured image. Additionally, the lower limit for haze is 0.1.

[0069] [Application Examples of Camera Systems] Figure 15 This is a schematic diagram illustrating an example of an in-vehicle occupant monitoring system using a camera system according to an embodiment of the present invention. Figure 16 This is a schematic diagram illustrating an example of the structure of an in-vehicle occupant monitoring system. exist Figure 15 and Figure 16 In the middle, to and Figure 1 The same structures of the camera system 10 shown are labeled with the same symbols, and their detailed descriptions are omitted. Figure 15 The interior of vehicle 40 is shown. Two seats 42 are arranged side-by-side in vehicle 40. The driver 43 sits in one seat 42, and the passenger sits in the other seat 42. For example, a camera system 46 is installed on the dashboard 45 at the front of the vehicle. The subject of the camera system 46 is at least one of the vehicle driver and vehicle occupants. Figure 15 In the example shown, the subject is driver 43. Monitoring only driver 43 is called a driver monitoring system. Alternatively, the camera system 46 can also be configured to bring the driver 43 and passenger 44 into the field of view.

[0070] and Figure 1 Compared to the camera system 10 shown, the camera system 46 has a processing unit 48, which is connected to the image sensor 26 and the display control unit 17 and is controlled by the control unit 18. As described above, the camera system 46 can remove reflected light caused by the unevenness of the face, thus obtaining a high-quality image of the driver's face 43. The processing unit 48 of the camera system 46 determines, for example, the facial orientation of the driver 43 based on the image signal representing the driver 43's face obtained by the image sensor 26. In determining the facial orientation of the driver 43, known image recognition techniques and AI (Artificial Intelligence) techniques such as machine learning or deep learning can be used, for example.

[0071] Furthermore, the arithmetic unit 48 stores judgment reference information that pre-associates states such as drowsiness and inattentiveness with facial orientation. The determined facial orientation of the driver 43 is compared with the aforementioned judgment reference information to determine the state of the driver 43. The determination result of the state can also be output to the display control unit 17 and displayed on the display unit 19. Thus, the state of the driver 43 can be visually monitored. When determining the state of driver 43, well-known image matching techniques and AI techniques such as machine learning or deep learning can be used, for example. Furthermore, the processing unit 48 can perform image analysis on the camera image of the driver 43, extract brightness information of the time sequence, and thus obtain pulse information. This allows the driver 43's physical condition to be assessed.

[0072] Furthermore, when the camera system is used for eye tracking, the pupil position can be detected in the calculation unit 48 based on the eye position in the facial camera image. In this case, the pupil reference position when observing from the front is predetermined. The calculation unit 48 estimates the gaze of the driver 43, etc., based on the difference between the pupil position and the pupil reference position. Additionally, pupil position refers to the position of the center of the pupil relative to the outer and inner corners of the eye in a facial camera image. As mentioned above, by estimating the driver's gaze 43, states such as drowsiness and inattentiveness can be estimated. When applied to eye tracking, the reflective components on the corneal surface become noise when detecting the pupil position. However, according to the above description, it is possible to obtain a facial camera image with the reflective components on the corneal surface blocked and less noise, thus enabling the driver's gaze to be estimated with high accuracy. When determining the position of the eyes and detecting the position of the pupils in a facial camera image, well-known image recognition techniques and AI techniques such as machine learning or deep learning can be used.

[0073] Furthermore, as described above, the camera system 10 can obtain images with low noise, and therefore can be used for vein authentication. In this case, the subject is, for example, the palm. In this case, the reflective components on the palm surface also constitute noise, but according to the above description, it is possible to obtain a vein image of the palm with low noise due to the blocking of reflective components on the palm surface. As described above, the camera system 10 used in the driver monitoring system, eye tracking, and vein authentication described above can be a structure where the second polarizing filter 30 is disposed on the incident surface 20a side of the lens 20 instead of the second polarizing filter 24. Furthermore, the driver monitoring system, eye tracking, and vein authentication described above can use... Figure 14 The camera system 11 shown.

[0074] [First polarizing filter and first circular polarizing filter] As described above, the structure of the first polarizing filter is not particularly limited as long as it can polarize the infrared light emitted from the light source 12, but the polarization patterns of the first and second polarizing filters are the same. For example, if the first polarizing filter is linearly polarized, the second polarizing filter is also linearly polarized. If the first polarizing filter is circularly polarized, i.e., if it is a first circularly polarized filter, the second polarizing filter is also circularly polarized. That is, it is a second circularly polarized filter. If the first polarizing filter has a cholesterol-type liquid crystal layer, the second polarizing filter also has a cholesterol-type liquid crystal layer.

[0075] [Second polarizing filter and second circular polarizing filter] As mentioned above, the structure of the second polarizing filter is not particularly limited as long as it can polarize the infrared light incident on the camera device. As mentioned above, the structure of the second circularly polarizing filter is not particularly limited as long as it can circularly polarize the infrared light incident on the camera device. The second polarizing filter and the second circular polarizing filter can be either reflective or absorptive, but from the viewpoint of suppressing reflections within the imaging device 14 and thus suppressing noise in the captured image, absorptive filters are preferred.

[0076] As described above, the first polarizing filter can be configured to include a first linear polarizer, and the second polarizing filter can be configured to include a second linear polarizer. Furthermore, as described above, the first circular polarizing filter can be configured to include a linear polarizer, and the second circular polarizing filter can also include a linear polarizer. Thus, both the first and second polarizing filters can be configured to include a linear polarizer. The linear polarizer will now be described.

[0077] (Linear polarizer) A linear polarizer has the function of converting unpolarized infrared light into linearly polarized light. Linear polarizers include reflective linear polarizers and absorptive linear polarizers. Examples of reflective linear polarizers include (i) multilayer linear polarizing reflectors, (ii) polarizers made by stacking thin films with different birefringences, (iii) linear grid polarizers, (iv) polarizing prisms, and (v) scattering anisotropic polarizers.

[0078] (i) As a multilayer linear polarizing reflector, a reflector formed by stacking multiple dielectric thin films with different refractive indices can be cited. In order to make a wavelength selective reflective film, it is preferable to stack multiple layers of dielectric thin films with high refractive index and dielectric thin films with low refractive index alternately, but it is not limited to two or more types. The number of layers is preferably 2 to 20, more preferably 2 to 12, even more preferably 4 to 10, and especially preferably 6 to 8. If the number of layers exceeds 20, production efficiency may sometimes decrease due to multiple layers of vapor deposition.

[0079] There are no restrictions on the stacking order of dielectric thin films; it can be selected appropriately according to the purpose. For example, when adjacent films have high refractive indices, the film with the lower refractive index is stacked first. Conversely, when adjacent layers have low refractive indices, the film with the higher refractive index is stacked first. The dividing point between high and low refractive indices is 1.8. Furthermore, high and low refractive indices are not absolute; within high-refractive-index materials, there can be materials with relatively high refractive indices and materials with relatively low refractive indices, and they can be used alternately.

[0080] Examples of high-refractive-index dielectric thin film materials include Sb₂O₃, Sb₂S₃, Bi₂O₃, CeO₂, CeF₃, HfO₂, La₂O₃, Nd₂O₃, and Pr₆O₃. 11 Examples of suitable materials include Sc2O3, SiO, Ta2O5, TiO2, TlCl, Y2O3, ZnSe, ZnS, and ZrO2. Among these, Bi2O3, CeO2, CeF3, HfO2, SiO, Ta2O5, TiO2, Y2O3, ZnSe, ZnS, and ZrO2 are preferred, and SiO, Ta2O5, TiO2, Y2O3, ZnSe, ZnS, and ZrO2 are particularly preferred.

[0081] Examples of low-refractive-index dielectric thin film materials include Al2O3, BiF3, CaF2, LaF3, PbCl2, PbF2, LiF, MgF2, MgO, NdF3, SiO2, Si2O3, NaF, ThO2, and ThF4. Among these, Al2O3, BiF3, CaF2, MgF2, MgO, SiO2, and Si2O3 are preferred examples, and Al2O3, CaF2, MgF2, MgO, SiO2, and Si2O3 are particularly preferred examples. Furthermore, in dielectric thin film materials, there are no particular restrictions on the atomic ratio, which can be appropriately selected according to the purpose. The atomic ratio can be adjusted by changing the concentration of ambient gas during film formation.

[0082] There are no limitations on the method for forming dielectric thin films, and an appropriate method can be selected according to the purpose. Examples of film formation methods include ion plating, vacuum evaporation such as ion beam deposition, physical vapor deposition (PVD) such as sputtering, and chemical vapor deposition (CVD). Among these, vacuum evaporation and sputtering are preferred, with sputtering being particularly preferred. As a sputtering method, DC (Direct Current) sputtering, which has a high film formation rate, is preferred. Furthermore, in DC sputtering, materials with high electrical conductivity are preferred. Furthermore, as methods for forming multilayer films by sputtering, there are, for example, (1) a single-chamber method in which films are formed alternately or sequentially from multiple targets in one chamber, and (2) a multi-chamber method in which films are formed continuously in multiple chambers. Among these, the multi-chamber method is particularly preferred from the viewpoint of productivity and prevention of material contamination. There is no limitation on the thickness of the dielectric thin film, but in terms of optical wavelength, a thickness of λ / 16 to λ is preferred, more preferably λ / 8 to 3λ / 4, and even more preferably λ / 6 to 3λ / 8.

[0083] In a dielectric vapor deposition layer, a portion of the light propagating within the layer is reflected in each dielectric film, resulting in multiple reflections. These reflected lights interfere, allowing only light of a wavelength determined by the product of the dielectric film thickness and its refractive index to be selectively transmitted. Furthermore, the central transmission wavelength of the dielectric vapor deposition layer is angle-dependent relative to the incident light; changing the incident light alters the transmission wavelength.

[0084] As a polarizer formed by stacking thin films of different birefringences (ii), for example, the polarizer described in Japanese Patent Application Publication No. 9-506837 can be used. Specifically, when processing under conditions selected to achieve the desired refractive index relationship, a wide variety of materials can be used to form the polarizer. Typically, one of the first materials needs to have a different refractive index than the second material in the selected direction. This difference in refractive index can be achieved through various methods, including stretching, extrusion molding, or coating during or after film formation. Furthermore, to enable the simultaneous extrusion of two materials, similar rheological properties (e.g., melt viscosity) are preferred. As a polarizer composed of stacked thin films of different birefringence, commercially available products can be used. Examples of commercially available products include, for instance, the product manufactured by 3M Company under the trade name DBEF.

[0085] (iii) A wire grid polarizer is a polarizer that allows one type of polarized light to be transmitted and another type of polarized light to be reflected through the birefringence of a thin metal wire. A wire grid polarizer is made by periodically arranging metal wires and is mainly used as a polarizer in the terahertz wave band. For the wire grid to function as a polarizer, the wire spacing needs to be sufficiently smaller than the wavelength of the incident electromagnetic wave. In an inline grid polarizer, metal lines are arranged at equal intervals. The polarization component parallel to the length direction of the metal lines is reflected in the inline grid polarizer, while the polarization component perpendicular to the length direction is transmitted through the inline grid polarizer. Commercially available products can be used as wire grid polarizers. Examples of commercially available wire grid polarizers include the 50×50 and NT46-636 wire grid polarizing filters manufactured by Edmund Optics, and the WGF (registered trademark) manufactured by Asahi Kasei Corporation. For example, when using a wire grid polarizer and a venetian blind in combination, the venetian blind is installed on the incident side of the wire grid polarizer. Then, the transmission axis of the wire grid polarizer is arranged orthogonally to the light-blocking axis of the venetian blind. Furthermore, the light-blocking axis of the venetian blind is arranged to cut off light incident from an oblique direction.

[0086] Examples of absorption-type line polarizers include (i) a polarizer that fixes the arrangement of metal nanoparticles with anisotropic shapes and (ii) a polarizer that fixes the arrangement of dichroic pigments. (i) A polarizer that fixes anisotropic metal nanoparticles is formed by orienting and fixing silver halide particles or silver particles with a large aspect ratio. This polarizer is an absorption-type linear polarizer that absorbs light with an electric field vibration surface in the particle alignment direction and transmits light in a direction orthogonal to it. As materials belonging to this category, materials described in Japanese Patent Application Publication No. 59-083951, Japanese Patent Application Publication No. 2-248341, and Japanese Patent Application Publication No. 2003-139951 can be used.

[0087] Examples of polarizers that fix the arrangement of dichroic dyes, as described in (ii), include polarizing films that adsorb iodine onto PVA (Polyvinyl alcohol) or dopant dichroic dyes and then stretch them. When used as a polarizer in the infrared region, it can be partially dehydrated to produce polyvinylidene ethylene (PVDE). This polarizer absorbs light with an electric field vibration surface during the stretching process and transmits light in a direction orthogonal to it. In this way, by dyeing the PVA layer by passing the PVA film through a dyeing composition bath such as iodine / iodide, and then stretching it at a ratio of 4 to 6, the orientation of dichroic pigments can be obtained. The conversion of PVA to polyvinylidene ethylene can be carried out by the hydrochloric acid vapor method as described in U.S. Patent No. 2,445,555. Furthermore, in order to improve the stability of this polarization material, borate treatment can also be performed using an aqueous borate bath containing boric acid and borate. A near-infrared linear polarizing film manufactured by Edmund Optics Japan is a commercially available product that is comparable to this.

[0088] There is no limitation on the thickness of the line polarizer, but it is preferably 0.05 to 300 μm, more preferably 0.2 to 150 μm, and even more preferably 0.5 to 100 μm.

[0089] [A second polarizing filter containing a dichroic substance that absorbs infrared light] As described above, the second polarizing filters 30 and 36 are specific second polarizing filters containing an infrared-absorbing dichroic material. Furthermore, the infrared-absorbing dichroic material will be described in detail as a component of the composition described later. The second polarizing filters 30 and 36 are equivalent to the LCF described later.

[0090] The thickness of the second polarizing filter is not particularly limited, but as shown in the formation method described later, it is not a venetian blind grating, but can be formed by coating, and therefore can be adjusted to less than 10 μm. The thickness of the second polarizing filter is preferably 0.5 to 8.0 μm, more preferably 0.5 to 6.0 μm. Furthermore, in this specification, the thickness of the second polarizing filter refers to the average thickness of the second polarizing filter. This average thickness is calculated by measuring the thickness of any five or more locations on the second polarizing filter and then taking their arithmetic average. Furthermore, the thickness of the second circular polarizing filter is the same as that of the second polarizing filter described above, so its detailed description is omitted.

[0091] In this invention, considering the reason that the absorption characteristics in the in-plane direction and the absorption characteristics in the thickness direction can be adjusted independently, as described above, the second polarizing filter preferably has a first layer and a second layer, the first layer containing an infrared-absorbing dichroic material and having an infrared absorption axis in the in-plane direction, and the second layer containing an infrared-absorbing dichroic material and having an infrared absorption axis in the thickness direction. Furthermore, the second layer is preferably free from anisotropy in infrared absorption in the in-plane direction. Additionally, "free from anisotropy in infrared absorption in the in-plane direction" means that when the azimuth angle is changed from the normal direction of the second polarizing filter while irradiating with linearly polarized infrared light at 360° intervals of 5°, the difference between the maximum and minimum absorbance values ​​is within 5% of the maximum value.

[0092] When a visible light image is captured by the image sensor 26, the average transmittance of the first layer and the second layer to visible light is preferably 70% or more.

[0093] In this invention, considering that the coating is completed in one layer and thin film formation is easily achieved, the second embodiment described above, namely the second polarizing filter described above, is preferably composed of a single layer containing an infrared-absorbing dichroic material and having an absorption axis for infrared radiation in the in-plane direction, and there is no anisotropy in the absorption of infrared radiation in the cross section along the absorption axis. Here, "there is no anisotropy in the absorption of infrared light" means that when the absorbance of infrared light along the absorption axis in the in-plane direction is set as kx, the absorbance of infrared light along the transmission axis in the in-plane direction is set as ky, and the absorbance in the thickness direction is set as kz, the following relationship is satisfied. kx=kz>ky Furthermore, the state of "no anisotropy in infrared absorption" can be evaluated by observing the cross-section along the transmission axis of infrared radiation in the in-plane direction using a polarizing microscope. If there is no phase difference, it is evaluated as the state of "no anisotropy in infrared absorption".

[0094] The second polarizing filter 36 (reference) Figure 10 In the image sensor 26, when capturing a visible light image, the infrared-absorbing dichroic material is preferably a material that does not substantially absorb visible light. Here, "substances that do not substantially absorb visible light" refers to substances that, when the transmittance of the substance itself is measured in the visible light region with wavelengths above 400 nm and below 700 nm, do not exhibit a specific peak in the aforementioned region and have a transmittance of 80% or more. The second polarizing filter 36 (reference) Figure 10 In this composition, the infrared-absorbing dichroic substance is preferably a disc-shaped pigment. Furthermore, the disc-shaped pigment will be described in detail as a component of the composition described later.

[0095] From the viewpoint of adjusting the orientation state of the aforementioned infrared-absorbing dichroic material, the layer structure of the second polarizing filter is preferably a layer formed of a composition containing the aforementioned infrared-absorbing dichroic material and a liquid crystal compound. The components contained in the composition will be described in detail below, and then the method for forming the layer in the second polarizing filter will be described in detail.

[0096] <Liquid Crystal Compounds> There are no particular restrictions on the types of liquid crystal compounds, but they can be classified into rod-shaped (rod-shaped liquid crystal compounds) and disc-shaped (disc-shaped liquid crystal compounds) types based on their shape. Furthermore, they are categorized into low-molecular-weight and high-molecular-weight types. High-molecular-weight compounds generally refer to molecules with a degree of polymerization of 100 or higher (Polymer Physics and Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992). Additionally, two or more rod-shaped liquid crystal compounds, two or more disc-shaped liquid crystal compounds, or mixtures of rod-shaped and disc-shaped liquid crystal compounds can be used. Liquid crystal compounds can be either thermotropic or lyotropic.

[0097] There are no particular restrictions on the location of the maximum absorption wavelength of liquid crystal compounds, but it is preferably located in the ultraviolet region.

[0098] Because it can reduce temperature and humidity changes in optical properties, liquid crystal compounds having polymerizable groups (rod-shaped or disc-shaped liquid crystal compounds) are preferred as liquid crystal compounds. The liquid crystal compound can be a mixture of two or more compounds; in this case, at least one compound having two or more polymerizable groups is preferred. In other words, the layer constituting the second polarizing filter is preferably a layer formed by polymerization or other fixation of a liquid crystal compound (rod-shaped liquid crystal compound or disk-shaped liquid crystal compound) having polymerizable groups. In this case, it is not necessary to exhibit liquid crystal properties after it becomes a layer. There are no particular restrictions on the types of polymerizable groups mentioned above, but polymerizable groups capable of free radical polymerization or cationic polymerization are preferred. As a free radical polymerizable group, known free radical polymerizable groups can be used, preferably acryloyl or methacryloyl. As the cationic polymerizable group, known cationic polymerizable groups can be used, specifically including alicyclic ether groups, cyclic acetal groups, cyclic lactone groups, cyclic thioether groups, spirocyclic orthoester groups, and ethyleneoxy groups. Among these, alicyclic ether groups or ethyleneoxy groups are preferred, and epoxy groups, oxetyl groups, or ethyleneoxy groups are more preferred. Examples of particularly preferred polymerizable groups include the following groups.

[0099] [Chemical Formula 2]

[0100] There is no particular limitation on the content of the liquid crystal compound in the composition, but it is preferably 50% by mass or more, more preferably 70% by mass or more, relative to the total solid content of the composition. There is no particular upper limit, but it is generally 90% by mass or less. In addition, the total solids content of the composition does not contain solvents.

[0101] <Infrared absorption dichroic substances> As a dichroic substance that absorbs infrared radiation, there are no particular restrictions as long as it is a dichroic substance that absorbs infrared radiation; however, dichroic pigments that absorb infrared radiation are preferred. Furthermore, dichroic pigments refer to pigments that have the property that the absorbance along the long axis of the molecule differs from the absorbance along the short axis. Examples of dichroic pigments that absorb infrared radiation include diketopyrrolopyrrole pigments, diimide pigments, phthalocyanine pigments, naphthylphthalocyanine pigments, azo pigments, polymethine pigments, anthraquinone pigments, pyranonium pigments, squaric acid pigments, triphenylmethane pigments, anthocyanin pigments, aminoonium pigments, metal complex pigments, boron complex pigments, oxacyanine pigments, perylene pigments, diphenylamine pigments, triphenylamine pigments, and quinone pigments. Infrared dichroic substances can be used alone or in combination of two or more.

[0102] Furthermore, dichroic pigments can be classified into dichroic pigments with rod-shaped molecules (hereinafter referred to as "rod-shaped pigments") and dichroic pigments with disc-shaped molecules (hereinafter referred to as "disc-shaped pigments"). However, in the first embodiment of the present invention, rod-shaped pigments are preferred, and in the second embodiment of the present invention, disc-shaped pigments are preferred. Here, the disc-shaped pigment has a disc-shaped partial structure in its nucleus, and the disc-shaped structure of the nucleus portion with the side chain removed can be defined by lengths a, b, and c obtained by (1) to (4) below or (1), (2), (3') to (5') below. (1) Regarding the disc-shaped structure of the disc-shaped pigment, a molecular structure that is as close to a planar shape as possible is constructed. As for the bonding distance and bonding angle, standard values ​​corresponding to the mixing of orbitals are preferred. The standard values ​​are recorded in Chapter 15 of Volume II of the Chemical Society of Japan, Chemical Handbook Revised 4th Edition (Maruzen, 1993). (2) Using the structure obtained in (1) above as the initial value, the structure is optimized by molecular orbital method or molecular force field method. As optimization methods, Gaussian92, MOPAC93, CHARMm / QUANTA and MM3 can be applied. Gaussian92 is particularly preferred. (3) Assign each atom in the optimized disk-shaped structure a sphere defined by van der Waals radius, thereby describing the shape of the molecule. (4) Let the three edges of the smallest cuboid that the disk-shaped structure obtained in (3) above can enter be a, b, and c.

[0103] To reduce arbitrariness, it is preferable to perform (3') to (5') below instead of (3) to (4) above. (3') Move the center of gravity of the structure obtained through structural optimization to the origin and set the coordinate axes as the principal axes of inertia (the principal axes of the inertial tensor ellipsoid). (4') Assign each atom a sphere defined by van der Waals radius, thereby describing the shape of the molecule. (5') Measure the lengths of each coordinate axis on the van der Waals surface and label them as a, b, and c respectively. If we use a, b, and c obtained through the above steps to define the structure, then in the preferred disk-shaped structure, the relationships a ≥ b > c and a ≥ b ≥ a / 2 are satisfied. A further preferred disk-shaped structure satisfies the relationships a ≥ b > c and a ≥ b ≥ 0.7a. Furthermore, b / 2 > c is also preferred.

[0104] As rod-shaped pigments, azo pigments, anthraquinone pigments, perylene pigments, and other anthocyanin pigments are preferred. For example, examples of azo pigments can be cited in Japanese Patent Application Publication No. 11-172252; examples of anthraquinone pigments can be cited in Japanese Patent Application Publication No. 8-067822; examples of perylene pigments can be cited in Japanese Patent Application Publication No. 62-129380, etc.; and examples of anthocyanin pigments can be cited in Japanese Patent Application Publication No. 2002-241758. These can be used alone or in combination with two or more. Furthermore, as a disc-shaped pigment, examples include polarizers using lyotropic liquid crystals, such as those from OPTIVA Inc., which are well-known as "E-Type polarizers." For instance, the material described in Japanese Patent Application Publication No. 2002-090547 can be cited. Similarly, there are examples of diazo-based dichroic pigments that utilize a rope-like micelle structure as the chemical structure for disc-shaped light absorption; the material described in Japanese Patent Application Publication No. 2002-090526 can be cited as an example. These can be used individually or in combination of two or more.

[0105] Furthermore, as a preferred choice for the second embodiment of the present invention, examples of disk-shaped pigments include compounds having a unique disk-shaped framework as pigments such as porphyrin, phthalocyanine, formazan, or triphenylmethane cores, and rod-shaped dichroic pigments such as azo pigments incorporated into the disk-shaped framework of disk-shaped liquid crystal molecules such as benzene rings or triphenylene rings as their radial side chains. Moreover, these pigments can be used in combination to enable polarization in desired wavelength regions. Regarding the aforementioned disc-shaped pigments, various literatures have reported on them (porphyrin core: NE Kagen et al., J. Amer. Chem. Soc., Vol. 99, p. 5484, 1977; phthalocyanine core: “Samples from the 28th Organic Devices Conference: New Developments in Organic Phthalocyanines” (Nagao Kobayashi, p. 1) and PA Stuzhin et al., Inog. Chem., Vol. 37, p. 2655, 1988; formazan core: Chemistry and application of leuco dyes, Plenium Press, New York, 1997, Chapter 7, Danel S. Daniel, p. 207; and triphenylmethane core: Chemistry and application of leuco dyes, Plenium Press, New York, 1997, Chapter 4, IJ Fletcher, p. 97).

[0106] In this invention, the infrared-absorbing dichroic material preferably has mesocrystalline groups. Because the infrared-absorbing dichroic material has mesocrystalline groups, it is easily oriented together with the aforementioned liquid crystal compound, thereby facilitating the control of the specified absorption characteristics. Mesocrystalline groups are functional groups that are rigid and oriented. Examples of structures that can be described as mesocrystalline groups include those composed of multiple groups selected from the group consisting of aromatic cyclic groups (aromatic hydrocarbon cyclic groups and aromatic heterocyclic groups) and alicyclic groups, either directly or via linking groups (e.g., -CO-, -O-, -NR- (R represents a hydrogen atom or an alkyl group) or groups composed of combinations thereof).

[0107] Furthermore, in this invention, as a preferred method for infrared-absorbing dichroic substances, the compound represented by the following formula (1) can be cited. Compounds having the structure represented by formula (1) exhibit low absorption in the visible light region, further suppressing coloration of the obtained anisotropic light absorption film. Furthermore, since the compound contains groups with mesocrystalline groups, it is easily aligned with liquid crystal compounds. In this case, the groups with mesocrystalline groups are arranged in a manner extending laterally from the fused ring portion containing the nitrogen atom located at the center of the compound, thus easily aligning them in a direction orthogonal to the aforementioned fused ring portion relative to the slow axis of the formed anisotropic light absorption film. In other words, absorption in the infrared region (especially wavelengths 700–900 nm) originating from the fused ring portion is easily obtained in a direction orthogonal to the slow axis of the anisotropic light absorption film, thereby easily obtaining an anisotropic light absorption film exhibiting the desired characteristics.

[0108] [Chemical Formula 3]

[0109] R 11 and R 12 Each of the following independently represents a hydrogen atom or a substituent, at least one of which is an electron-withdrawing group, R 11 and R 12 They can bond together to form a ring. Examples of substituents include alkyl, alkenyl, alkynyl, aryl, amino, alkoxy, aryloxy, aromatic heterocyclic, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, aromatic heterocyclic thio, sulfonyl, sulfinyl, ureyl, phosphoramidyl, hydroxyl, mercapto, halogen atom, cyano, sulfonyl, carboxyl, nitro, hydroxamic acid, sulfinyl, hydrazine, imino, heterocyclic, and silyl.

[0110] As an electron-withdrawing group, Hammett's σp value (sigma constant) indicates a positive substituent, such as cyano, acyl, alkoxycarbonyl, aryloxycarbonyl, aminosulfonyl, sulfinyl, and heterocyclic groups. These electron-withdrawing groups can be further replaced. The Hammett substituent constant σ value is explained. Hammett's rule, an empirical rule proposed by L.P. Hammett in 1935 to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives, is now widely accepted for its validity. The substituent constants determined by Hammett's rule have σp and σm values, which can be found in many general books. For example, they are detailed in *Lange's Handbook of Chemistry*, 12th edition, 1979 (McGraw-Hill), or *Chemical Fields* Supplement, No. 122, pp. 96-103, 1979 (Nankodo), *Chem. Rev.*, 1991, Vol. 91, pp. 165-195, etc. In this invention, substituents with a Hammett substituent constant σp value of 0.20 or higher are preferred as electron-withdrawing groups. As for the σp value, 0.25 or higher is preferred, 0.30 or higher is more preferred, and 0.35 or higher is even more preferred. There is no particular limit to the upper limit, but it is preferred to be below 0.80. Specific examples include cyano (0.66), carboxyl (-COOH: 0.45), alkoxycarbonyl (-COOMe: 0.45), aryloxycarbonyl (-COOPh: 0.44), carbamoyl (-CONH2: 0.36), alkylcarbonyl (-COMe: 0.50), arylcarbonyl (-COPh: 0.43), alkylsulfonyl (-SO2Me: 0.72), and arylsulfonyl (-SO2Ph: 0.68). In this specification, Me represents methyl and Ph represents phenyl. Additionally, the values ​​in parentheses are σp values ​​of representative substituents extracted from Chem. Rev., 1991, Vol. 91, pp. 165–195.

[0111] In R 11 and R 12 When a ring is formed by bonding, a 5- to 7-membered ring (preferably a 5- to 6-membered ring) is formed. As the formed ring, anthocyanin is preferably used as an acidic nucleus. As R 11 and R 12 The bonded ring is preferably a 1,3-dicarbonyl core, a pyrazolone core, a 2,4,6-trionehexahydropyrimidine core (also including thionone forms), a 2-thio-2,4-thiazolidinedione core, a 2-thio-2,4-oxazolone core, a 2-thio-2,5-thiazolidinedione core, a 2,4-thiazolidinedione core, a 2,4-imidazolidinedione core, a 2-thio-2,4-imidazolidinedione core, a 2-imidazolin-5-one core, a 3,5-pyrazolone core, a benzothiophene-3-one core, or an indanone core.

[0112] R 11Heterocyclic groups are preferred. Among heterocyclic groups, pyrazole, thiazole, oxazole, imidazole, oxadiazole, thiadiazole, triazole, pyridine, pyridazine, pyrimidine, pyrazine, these benzo[a]-fused-ring groups or naph[a]-fused-ring groups, or complexes of these fused rings are preferred.

[0113] R 13 Each can independently represent a hydrogen atom, alkyl group, aryl group, heteroaryl group, substituted boron atom, or metal atom, and can be associated with R. 11 Covalent bonding or coordination bonding. R 13 The substituents representing substituted boron are related to R. 11 and R 12 The substituents mentioned above have the same meaning, and alkyl, aryl, or heteroaryl groups are preferred. Furthermore, R 13 The metal atoms represented are preferably transition metal atoms, magnesium atoms, aluminum atoms, calcium atoms, barium atoms, zinc atoms or tin atoms, and more preferably aluminum atoms, zinc atoms, tin atoms, vanadium atoms, iron atoms, cobalt atoms, nickel atoms, copper atoms, palladium atoms, iridium atoms or platinum atoms.

[0114] R 14 Each group is represented independently as having a mesocrystalline group. The definition of a mesocrystalline group is as described above. R 14 Preferably, the group is represented by the following formula (2). * indicates the bonding position. Equation (2) *-M 1 -(X) 1 -M 2 ) n -X 2 -P M 1 This indicates a substituted or unsubstituted arylene or a substituted or unsubstituted heteroarylene. Phenylene can be cited as an example of an arylene. X 1 and X 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CH2-, -CH=CH-, -C≡C-, and -NR. 0 - or combinations thereof (e.g., -O-CO- and -CH2-CH2-). R 0 It represents an alkyl group having 1 to 5 hydrogen atoms or carbon atoms. M 2 It indicates substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, or substituted or unsubstituted cycloalkylene. n represents 1 to 5. Among them, 2 to 4 are preferred. P represents a hydrogen atom or a polymeric group. The definition of a polymeric group is the same as the definition of polymeric groups that liquid crystal compounds can possess, as described above.

[0115] Oxycyanine pigments are a preferred method for absorbing dichroic substances in the infrared. As an oxacyanine pigment, the compound represented by formula (11) is preferred.

[0116] [Chemical Formula 4]

[0117] In equation (11), Y 1 and Y 2 Each group of nonmetallic atoms that forms an aliphatic ring or heterocycle is represented independently, M + L represents a proton, a monovalent alkali metal cation, or an organic cation. 1 This indicates a methine chain consisting of 5 or 7 methine groups, with the central methine group having a substituent represented by formula A. *-S A -T A Formula (A) In formula (A), S A Represents single bond, alkylene, alkenylene, ynylene, -O-, -S-, -NR L1 -, -C(=O)-, -C(=O)O-, -C(=O)NR L1 -、-S(=O)2-、-OR L2 - or groups formed by combining them, R L1 R represents a hydrogen atom, halogen atom, alkyl group, aryl group, or heteroaryl group. L2 Indicates alkylene, arylene, or divalent heterocyclic group, T A The following groups are represented: halogen atom, alkyl, cycloalkyl, aryl, heteroaryl, cyano, hydroxyl, formyl, carboxyl, amino, thiol, sulfonyl, phosphoryl, boroalkyl, vinyl, ethynyl, trialkylsilyl or trialkoxysilyl, S A Indicates a single bond or alkylene group, and T A When representing an alkyl group, S A and T A The total number of carbon atoms contained is 3 or more, and * indicates the bonding site with the central methylene group of the methylene chain.

[0118] As an oxacyanine pigment, the compound represented by formula (12) is more preferred.

[0119] [Chemical Formula 5]

[0120] In equation (12), M +and L 1 M in equation (11) + and L 1 same. R m1 R m2 R m3 and R m4 Each of the following can be independently represented by a hydrogen atom, alkyl group, aryl group, or heteroaryl group, and X can be independently represented by an oxygen atom, sulfur atom, or selenium atom.

[0121] As an oxacyanine pigment, the compound represented by formula (13) is further preferred.

[0122] [Chemical Formula 6]

[0123] In equation (13), M + L 1 and X and M in equation (11) + L 1 And X is the same. R n1 and R n3 Each of the following can independently represent a hydrogen atom, alkyl group, aryl group, or heteroaryl group, R n2 and R n4 Each can be independently represented by an alkyl group, halogen atom, alkenyl group, aryl group, heteroaryl group, nitro group, cyano group, or -OR group. L3 -C(=O)R L3 -C (=O) OR L3 -OC (=O)R L3 -N(R) L3 2. -NHC(=O)R L3 -C(=O)N(R) L3 2. -NHC (=O) OR L3 -OC(=O)N(R) L3 2. -NHC(=O)N(R) L3 2. -SR L3 -S(=O)2R L3 -S(=O)2OR L3 -NHS(=O)2R L3 or -S(=O)2N(R) L3 )2,R L3 Each of the following groups can be independently represented by a hydrogen atom, alkyl group, alkenyl group, aryl group, or heteroaryl group, and each of the following groups can be independently represented by an integer from 1 to 5.

[0124] Anthocyanin pigments are a preferred method for absorbing dichroic substances in the infrared field. As anthocyanin pigments, compounds represented by formula (3) or formula (4) are preferred.

[0125] [Chemical Formula 7]

[0126] [Chemical Formula 8]

[0127] In equation (3), Ar 3 ~Ar 4 Each can be independently represented by a heterocyclic group that may have substituents, R c1 It represents a hydrogen atom or a substituent. Ar 3 and Ar 4 At least one of them preferably represents a heterocyclic group having a substituent containing a hydrophilic group (hereinafter also referred to as "specific substituent"). Examples of hydrophilic groups include groups comprising an acid group or its salt, an onium salt group, a hydroxyl group or its salt, a sulfonamide group (H2N-SO2-) or its salt, and a polyoxyalkylene group, with an acid group or its salt being preferred. Examples of acid groups or their salts include, for instance, a sulfonyl group (-SO3H) or its salt (-SO3). - M + M + It represents a cation, and a carboxyl group (-COOH) or its salt (-COO). - M + M + (This indicates a cation.) Examples of heterocycles constituting the heterocyclic group include, for example, indolenine rings, benzo[a]-indolenine rings, imidazole rings, benzo[a]-imidazolium rings, naph[a]-imidazolium rings, thiazole rings, benzo[a]-thiazole rings, naph[a]-thiazole rings, thiazoline rings, oxazole rings, benzo[a]-oxazole rings, naph[a]-oxazole rings, oxazoline rings, selenazole rings, benzo[a]-selenoazole rings, naph[a]-selenoazole rings, and quinoline rings, with preferred examples being indolenine rings, benzo[a]-indolenine rings, benzo[a]-thiazole rings, or naph[a]-thiazole rings. Specific substituents can substitute on heteroatoms in heterocycles or on carbon atoms. Heterocyclic groups may have one or more (e.g., two to three, etc.) specific substituents.

[0128] r c1 It represents an integer from 1 to 7, preferably an integer from 3 to 5.

[0129] R c1 There is no particular limitation on the type of substituent represented. Known substituents can be cited, with alkyl groups, aryl groups, or heteroaryl groups that can have substituents being preferred. Examples of substituents that can be present in alkyl, aryl, and heteroaryl groups include, for example, alkyl, alkenyl, alkoxy, aryloxy, aromatic heterocyclic oxy, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, amide, alkoxycarbonylamino, aryloxycarbonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, aromatic heterocyclic thio, ureyl, halogen atom, cyano, nitro, heterocyclic (e.g., heteroaryl), silyl, and groups formed by combining them (hereinafter, these groups are also collectively referred to as "substituent W"). Furthermore, the above-mentioned substituents can be further replaced by substituent W.

[0130] In equation (4), Ar 5 ~Ar 6 Each can be independently represented as a heterocyclic group that may have substituents, Ar 7 It represents a cyclic skeleton with 5 to 7 carbon atoms, and W represents a hydrogen atom, a halogen atom, a methyl group, a phenyl group that may have substituents, a benzyl group that may have substituents, a pyridyl group, a morpholinyl group, a piperidinyl group, a pyrrolidinyl group, a phenylamino group that may have substituents, a phenoxy group that may have substituents, an alkylthio group that may have substituents, or a phenylthio group that may have substituents. Ar 5 and Ar 6 At least one of them preferably represents a heterocyclic group having a specific substituent. Examples of heterocycles constituting the heterocyclic group include, for example, indolenine rings, benzo[a]-indolenine rings, imidazole rings, benzo[a]-imidazolium rings, naph[a]-imidazolium rings, thiazole rings, benzo[a]-thiazole rings, naph[a]-thiazole rings, thiazoline rings, oxazole rings, benzo[a]-oxazole rings, naph[a]-oxazole rings, oxazoline rings, selenazole rings, benzo[a]-selenoazole rings, naph[a]-selenoazole rings, and quinoline rings, with preferred examples being indolenine rings, benzo[a]-indolenine rings, benzo[a]-thiazole rings, or naph[a]-thiazole rings. As substituents that can be present in phenyl, benzyl, phenylamino, phenoxy, alkylthio, and phenylthio groups represented by W, examples of groups, hydrophilic groups, and specific substituents exemplified in the above-mentioned substituents W can be cited. There is no particular limitation on the number of carbon atoms in the alkylthio group represented by W, but it is preferred to be 1 to 5, and more preferably 1 to 3.

[0131] The compound represented by formula (4) is preferably an intramolecular salt or intermolecular salt with cations and anions in one molecule. In the case of intermolecular salt, examples include halosalts, perchlorates, antimony fluoride salts, fluorinated phosphate salts, boron fluoride salts, trifluoromethanesulfonates, bis(trifluoromethane)sulfonyl imide salts and naphthalenesulfonic acid, etc. Specifically, examples include indocyanine green and water-soluble pigments described in Japanese Patent Application Publication No. 63-033477.

[0132] As the compound represented by formula (4), the compound represented by formula (4-1) is preferred.

[0133] [Chemical Formula 9]

[0134] In equation (4-1), R c2 ~R c5 Each can be used independently to represent a hydrogen atom or a substituent. R c2 ~R c5 At least one of the preferred representations in the formula represents -SO3 - Substituents (e.g., those with -SO3) - Alkyl groups. The alkyl group preferably has 1 to 10 carbon atoms. (Alkyl groups containing -COO) - Substituents (e.g., those with -COO) - Alkyl groups. The alkyl group preferably has 1 to 10 carbon atoms. ( ), -SO3 - or -COO - . R c Each can be used independently to represent a hydrogen atom or a substituent. As R c The substituents represented can be the groups exemplified in substituent W, preferably alkyl groups. The alkyl group preferably has 1 to 5 carbon atoms. Ar c1 and Ar c2 Ar represents aromatic hydrocarbon rings (e.g., benzene ring and naphthalene ring) independently. 7 The symbol represents a cyclic skeleton with 5 to 7 carbon atoms; W represents a hydrogen atom, a halogen atom, a methyl group, a phenyl group that may have substituents, a benzyl group that may have substituents, a pyridyl group, a morpholinyl group, a piperidinyl group, a pyrrolidinyl group, a phenylamino group that may have substituents, a phenoxy group that may have substituents, an alkylthio group that may have substituents, or a phenylthio group that may have substituents; r c2 r represents an integer from 1 to 3. c3 Represents integers from 1 to 3. As R c2 ~R c5 The substituents represented can be the groups exemplified in substituent W and specific substituents. As substituents that can be present in phenyl, benzyl, phenylamino, phenoxy, alkylthio, and phenylthio groups represented by W, examples of groups and specific substituents exemplified in substituent W can be given.

[0135] There is no particular limitation on the content of the infrared-absorbing dichroic substance in the composition. From the viewpoint of better effect of the present invention, it is preferably 5 to 70% by mass relative to the total mass of the liquid crystal compound, and more preferably 10 to 50% by mass.

[0136] <Other Ingredients> The above composition may contain components other than the liquid crystal compound and the infrared-absorbing dichroic substance. The composition may also contain a polymerization initiator. The polymerization initiator used is selected according to the form of polymerization reaction; for example, thermal polymerization initiators and photopolymerization initiators can be mentioned. For example, as photopolymerization initiators, α-carbonyl compounds, azobin ethers, α-hydrocarbon-substituted aromatic azobin compounds, polynuclear quinone compounds, and combinations of triarylimidazolium dimers and p-aminophenyl ketones can be mentioned. The content of polymerization initiator in the composition is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, relative to the total solid content of the composition.

[0137] Furthermore, the composition may contain polymerizable monomers. Examples of polymerizable monomers include free radical polymerizable compounds and cationic polymerizable compounds. Among these, multifunctional free radical polymerizable monomers are preferred. Furthermore, monomers copolymerized with liquid crystal compounds having the aforementioned polymerizable groups are preferred. For example, the polymerizable monomers described in paragraphs

[0018] to

[0020] of Japanese Patent Application Publication No. 2002-296423 can be cited. The content of polymerizable monomers in the composition is preferably 1 to 50% by mass relative to the total mass of the liquid crystal compound, more preferably 2 to 30% by mass.

[0138] Furthermore, the composition may contain a surfactant. As surfactants, conventionally known compounds can be cited, but fluorinated compounds are preferred. For example, compounds described in paragraphs

[0028] to

[0056] of Japanese Patent Application Publication No. 2001-330725 and compounds described in paragraphs

[0069] to

[0126] of Japanese Patent Application No. 2003-295212 can be cited.

[0139] Furthermore, the composition may contain a solvent. Preferably, an organic solvent is preferred. Examples of organic solvents include amides (e.g., N,N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), haloalkanes (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1,2-dimethoxyethane). Additionally, two or more organic solvents may be used simultaneously.

[0140] Furthermore, the composition may contain various orientation control agents, such as vertical orientation agents and horizontal orientation agents. These orientation control agents are compounds that can control the liquid crystal compound to be oriented horizontally or vertically on the surface side. In addition to the above-mentioned components, the composition may also contain a sealant modifier, a plasticizer, and a polymer.

[0141] <Forming Method> There are no particular limitations on the method for forming the second polarizing filter using the above composition, and known methods can be cited. From the viewpoint of easily controlling in-plane delay, it is preferable to form a coating film by coating a composition containing a liquid crystal compound having polymeric groups (hereinafter also simply referred to as "polymeric liquid crystal compound") and an infrared-absorbing dichroic substance, to perform an orientation treatment on the coating film to orient the polymeric liquid crystal compound, and to perform a curing treatment (ultraviolet irradiation (light irradiation treatment) or heat treatment) on the obtained coating film to form a light-absorbing anisotropic film. The steps of the above method are explained in detail below.

[0142] First, a composition is coated onto a support to form a coating film, and the coating film is oriented to orient the polymeric liquid crystal compound. The composition used contains a polymerizable liquid crystal compound. The definition of a polymerizable liquid crystal compound is as described above.

[0143] The support used is a component that functions as a substrate for coating the composition. The support can be a temporary support that is peeled off after the composition has been coated and cured. In addition to plastic films, glass substrates can also be used as supports (temporary supports). Examples of materials constituting plastic films include polyester resins such as polyethylene terephthalate (PET), polycarbonate resins, (meth)acrylic resins, epoxy resins, polyurethane resins, polyamide resins, polyolefin resins, cellulose derivatives, silicone resins, and polyvinyl alcohol (PVA). The thickness of the support can be about 5 to 1000 μm, preferably 10 to 250 μm, and more preferably 15 to 90 μm.

[0144] Additionally, an orientation layer can be configured on the support as needed. Orientation layers are typically composed primarily of polymers. Polymers for orientation layers are documented in numerous publications, and many commercially available products are readily available. Polyvinyl alcohol, polyimide, or derivatives thereof are preferred polymers for orientation layers. In addition, it is preferable to apply a known friction treatment to the orientation layer. The thickness of the orientation layer is preferably 0.01 to 10 μm, more preferably 0.01 to 1 μm.

[0145] Examples of coating methods for the composition include curtain coating, dip coating, spin coating, printing coating, spray coating, slot coating, roller coating, glide coating, doctor blade coating, gravure coating, and wire rod coating. Regardless of the coating method, single-layer coating is preferred.

[0146] An orientation treatment is performed on the coating film formed on the support to orient the polymeric liquid crystal compound in the coating film. Orientation processing can be performed by drying the coating at room temperature or by heating the coating. In the case of thermotropic liquid crystal compounds, the liquid crystal phase formed by orientation processing can generally be transferred according to changes in temperature or pressure. In the case of lyotropic liquid crystal compounds, transfer can also be achieved through compositional ratios such as solvent volume. In addition, there are no particular restrictions on the conditions for heating the coating. The heating temperature is preferably 50 to 250°C, more preferably 50 to 150°C, and the heating time is preferably 10 seconds to 10 minutes. Furthermore, after heating the coating and before the curing process (light irradiation treatment) described later, the coating can be cooled as needed. The cooling temperature is preferably 20 to 200°C, more preferably 30 to 150°C. Furthermore, there is no particular limitation on the difference between the heating temperature and the cooling temperature of the coating, but it is preferably 40°C or higher. There is no particular upper limit, but 150°C or lower can be cited as an example. Specifically, when the coating is heated and cooled before the curing process, the heating temperature T of the coating is... A Preferably, the temperature is 50–250°C, and the cooling temperature T B Preferably at heating temperature T A ×0.4~Heating temperature T A Within the range of ×0.7.

[0147] Next, the coating film after the polymeric liquid crystal compound has been oriented is subjected to a curing process. There are no particular limitations on the method of curing the coating film after the polymeric liquid crystal compound has been oriented; for example, light irradiation and heat treatment can be cited. From the viewpoint of manufacturing adaptability, light irradiation is preferred, and ultraviolet irradiation is more preferred. There are no particular restrictions on the irradiation conditions for light treatment, but 50–1000 mJ / cm² is preferred. 2 The amount of radiation.

[0148] In the above-described formation method, by adjusting various conditions, the configuration state of the infrared-absorbing dichroic material can be adjusted, and as a result, the optical properties of the light-absorbing anisotropic film can be adjusted. For example, by adjusting the heating temperature during the alignment of the liquid crystal compound after forming a coating film by coating the composition on the support, and the cooling temperature during the subsequent cooling, the configuration state of the infrared-absorbing dichroic material can be adjusted. As a result, the optical properties of the light-absorbing anisotropic film can be adjusted. Furthermore, the second circularly polarizing filter can be formed using the same method as the second polarizing filter described above, therefore its detailed description is omitted.

[0149] The present invention is basically constructed as described above. The camera system of the present invention has been described in detail above, but the present invention is not limited to the above embodiments. Various improvements or modifications can be made without departing from the spirit of the present invention. Example

[0150] The following examples further illustrate the features of the present invention. The materials, reagents, quantities, proportions, and operations shown in the following examples can be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the present invention is not limited to the following examples. In this embodiment, the noise of the captured images was evaluated for the camera systems of Examples 1 to 11 and Comparative Examples 1 and 2. The results are shown in Table 1 below.

[0151] The camera systems of Examples 1-11 and Comparative Examples 1 and 2 used Figure 1 The camera system 10 shown has a different type and position of the second polarizing filter. Light source 12 uses an 850nm wavelength LED (WindFire Mini IR Lamp Zoomable 5W 850nm / 940nm LED Infrared Flashlight Night Vision). The camera device 14 uses a lens mounted on the camera. The lens is a Lensation B5M6018 (manufactured by iDS), 6mm, 1 / 2.5". The camera is a daA3840-45uc (manufactured by Basler). The camera systems of Examples 1 to 11 and Comparative Examples 1 and 2 will be described.

[0152] (Example 1) Example 1 is set in Figure 1 The camera system 10 shown has a structure in which a second polarizing filter 24 is configured at the pupil position. The following LCF was used in the second polarizing filter 24. The haze of the LCF is 0.8. The following is an explanation of LCF. LCF stands for Absorption Linear Polarizer.

[0153] (LCF) The cellulose acylated membrane T1 (“TD40UL”, manufactured by Fujifilm Corporation) is passed through a dielectric heating roller at a temperature of 60°C, raising the membrane surface temperature to 40°C. Then, using a bar coater, coat one side of the membrane at 14 ml / m 2 The film is coated with an alkaline solution of the following composition and heated to 110°C. Next, the obtained membrane was conveyed for 10 seconds using a steam-type far-infrared heater manufactured by Noritake Company Limited. Next, using the same bar coater, 3 ml / m² of pure water was coated onto the surface of the membrane. 2 . Next, the obtained membrane was repeatedly washed with water using a spray coating machine and dehydrated using an air knife three times. Then, the membrane was transported to a drying zone at 70°C for 10 seconds to dry, thereby producing an alkali-saponified cellulose acylate membrane as a support.

[0154] ─────────────────────────────── (Alkaline solution) ─────────────────────────────── 4.7 parts by weight of potassium hydroxide 15.8 parts by weight of water · Isopropanol 63.7 parts by weight Surfactants (C) 14 H 29 O(CH2CH2O) 20 H) 1.0 parts by weight ·Propylene glycol 14.8 parts by weight ───────────────────────────────

[0155] The following orientation layer coating liquid was continuously applied to the support using a #14 wire bar. Next, the support with the coating film is dried with warm air at 60°C for 60 seconds, and then further dried with warm air at 100°C for 120 seconds. Next, the dried coating is continuously subjected to friction treatment to form an orientation layer. At this time, the length direction of the strip film is parallel to the conveying direction, and the rotation axis of the friction roller is set to a 45° clockwise direction relative to the length direction of the film.

[0156] ─────────────────────────────── (Orientation layer coating liquid) ─────────────────────────────── • 10.0 parts by weight of the following modified polyvinyl alcohol ·Water 371.0 parts by weight ·Methanol 119.0 parts by weight 0.5 parts by weight of glutaraldehyde • Polymerization initiator (IRGACURE 2959, manufactured by BASF) 0.3 parts by weight ───────────────────────────────

[0157] Modified polyvinyl alcohol (in the following structural formulas, the proportions are molar ratios) [Chemical Formula 10]

[0158] The following coating solution for anisotropic light absorption films was prepared. ─────────────────────────────── (Coating solution for anisotropic light absorption films) ─────────────────────────────── • 80 parts by weight of the following liquid crystal compound L-1 • 20 parts by weight of infrared absorbing pigment IR-2 Photopolymerization initiator 1 (IRGACURE OXE01, manufactured by BASF) 3.0 parts by weight • Photopolymerization initiator 2 (IRGACURE 184, manufactured by BASF) 3.0 parts by weight • 0.2 parts by weight of the following fluorinated compound F-1 · Cyclopentanone 227.1 parts by weight ───────────────────────────────

[0159] Liquid crystal compound L-1 (a mixture of the following three compounds. The mixing ratio is shown in the upper left corner of the compound.) [Chemical Formula 11]

[0160] Infrared Absorbing Pigment IR-2 [Chemical Formula 12]

[0161] Fluorine compound F-1 [Chemical Formula 13]

[0162] The above-mentioned light-absorbing anisotropic film is coated onto the above-mentioned alignment layer with a coating liquid using a wire rod to form a coating film. The coating film is heated at 100°C for 5 minutes and then cooled to 60°C. Then, nitrogen purging was performed using an ambient gas with an oxygen concentration of less than 1.0% by volume, and the coating was irradiated with a high-pressure mercury lamp at a dose of 500 mJ / cm². 2 LCF was fabricated using ultraviolet light. The thickness of the obtained LCF (excluding the support and orientation layer) was 5 μm.

[0163] (Example 2) Compared to Example 1, Example 2 uses a light-absorbing anisotropic film 1 instead of an LCF; otherwise, it is the same as in Example 1. The haze of the light-absorbing anisotropic film 1 is 0.8. The light-absorbing anisotropic film 1 is an absorption-type linear polarizer. The following describes the light-absorbing anisotropic film 1.

[0164] (Light absorption anisotropic film 1) Composition 1 with the following composition was prepared. ─────────────────────────────── Composition 1 ─────────────────────────────── 10 parts by mass of rod-shaped compound I-1 Infrared Absorbing Pigment IR-1 1 part by weight 89 parts by weight of water ───────────────────────────────

[0165] Rod-shaped compound I-1 (refer to the structural formula below)

[0166] [Chemical Formula 14]

[0167] Infrared absorbing pigment IR-1 (refer to the following structural formula)

[0168] [Chemical Formula 15]

[0169] The above-prepared composition 1 (5g) and zirconia microspheres with an average particle size of 2mm (20g) were filled into a zirconia 45mL container and ground for 50 minutes at 300rpm using a FRISCH P-7 classic line planetary ball mill. On a glass substrate, the above-mentioned polished composition 1 was coated with a wire rod (moving speed: 100 cm / s) and then allowed to dry naturally. Next, the obtained composite layer was immersed in a 1 mol / L calcium chloride aqueous solution for 5 seconds, then washed with deionized water and dried by air to fix the orientation state, thereby producing a light-absorbing anisotropic film 1 with a thickness of 1.2 μm.

[0170] (Example 3) Compared with Example 1, in Example 3 the second polarizing filter is positioned on the image side, otherwise it is the same as in Example 1. (Example 4) Compared with Example 2, in Example 4 the second polarizing filter is positioned on the image side, otherwise it is the same as in Example 2.

[0171] (Example 5) Compared to Example 1, Example 5 uses a wire grid polarizer and louvers to replace the LCF of the second polarizing filter. Otherwise, it is the same as Example 1. The wire grid polarizer is a reflective wire polarizer. The wire grid polarizer uses WGF (registered trademark) manufactured by Asahi Kasei Corporation. The venetian blinds use 3M Company venetian blinds. In Table 1, the wire grid type deflector is recorded as "WG". Furthermore, in Table 1, the combination of the wire grid type deflector and the louver is recorded as "WG+louver". In embodiment 5, a lens 20, a venetian blind, a wire grid polarizer, and a lens 22 are arranged sequentially. Furthermore, the transmission axis of the wire grid polarizer is orthogonal to the light-blocking axis of the venetian blind. The light-blocking axis of the venetian blind is positioned to cut off light incident from an oblique direction.

[0172] (Example 6) Compared with Example 5, Example 6 does not have blinds, but otherwise it is the same as Example 5. (Example 7) Compared to Example 6, in Example 7 the second polarizing filter is positioned on the image side; otherwise, it is the same as in Example 6. (Example 8) Compared with Example 2, Example 8 uses an anisotropic light absorption film 2 instead of the anisotropic light absorption film 1 of the second polarizing filter. Otherwise, it is the same as Example 2. The following describes the light absorption anisotropic film 2. The haze of the light absorption anisotropic film 2 is 3.

[0173] (Light absorption anisotropic film 2) The light-absorbing anisotropic film 2 is manufactured in the same manner as the light-absorbing anisotropic film 1, except that the polishing time of the light-absorbing anisotropic film 1 is changed to 5 minutes. Like the light-absorbing anisotropic film 1, the light-absorbing anisotropic film 2 is an absorption-type linear polarizer.

[0174] (Example 9) Compared to Example 1, in Example 9, the second polarizing filter is located on the subject side. Figure 1 The subject 13 side of the lens 20 shown is otherwise the same as in Embodiment 1. (Example 10) Compared to Example 1, Example 10 uses a circular polarizer instead of the LCF of the second polarizing filter, and the circular polarizer is positioned on the subject side. Figure 1 The subject 13 side of the lens 20 shown is otherwise the same as in Example 1. The circular polarizer corresponds to the second circular polarizing filter. The following is an explanation of circular polarizers. A circular polarizer is a combination of a linear polarizer and a λ / 4 plate.

[0175] <Fabrication of Circular Polarizers> <<Making of a Wire Polarizer>> Composition 1, with the following composition, was prepared. Composition 1 is a composition exhibiting lyotropic liquid crystal properties.

[0176] ─────────────────────────────── Composition 1 ─────────────────────────────── Dichroic pigment III-2 5 parts by weight 95 parts by weight of water ───────────────────────────────

[0177] Dichroic pigment III-2

[0178] [Chemical Formula 16]

[0179] The above-prepared composition 1 (5g) and zirconia microspheres with an average particle size of 2mm (20g) were filled into a zirconia 45mL container and ground for 50 minutes at 300rpm using a FRISCH planetary ball mill P-7 classic line.

[0180] On a glass substrate, the above-mentioned polished composition 1 was coated using a wire rod (moving speed: 100 cm / s) and allowed to air dry. Next, the obtained composition layer was immersed in a 1 mol / L calcium chloride aqueous solution for 5 seconds, rinsed with deionized water, and air-dried to fix the orientation state, thereby fabricating a 200 nm thick anisotropic light-absorbing film 1 (wire polarizer).

[0181] The fabricated anisotropic light-absorbing film 1 functions as an absorption-type linear polarizer for light with a wavelength of 940nm.

[0182] <<Fabrication of λ / 4 board>> [Fabrication of the Optical Anisotropic Layer] Composition H1 for forming optical anisotropic layers was prepared with the following composition: it was heated and dissolved at 50°C for 3 hours while stirring, and then filtered through a 0.45 μm filter.

[0183] ─────────────────────────────── Composition H1 for forming optical anisotropic layers ─────────────────────────────── • 75.5 parts by weight of the following liquid crystal compound H1 • Polymerization initiator IRGACURE 819 (manufactured by BASF) 0.8 parts by weight • 0.6 parts by weight of the above surfactant F-1 · Cyclopentanone 274.5 parts by weight ───────────────────────────────

[0184] Liquid crystal compound H1 (a mixture of the following three compounds. The mixing ratio (mass ratio) is shown in the upper left corner of the compound.) [Chemical Formula 17]

[0185] (Fabrication of the transparent support) -Preparation of core layer cellulose acylate concentrate- The following composition was added to a mixing tank and stirred to dissolve the components, thereby preparing a cellulose acetate solution for use as a core layer cellulose acylate concentrate.

[0186] ─────────────────────────────── Core layer cellulose acylate concentrate ─────────────────────────────── 100 parts by weight of cellulose acetate with a degree of acetyl substitution of 2.88 • Polyester compound B described in the examples of Japanese Patent Application Publication No. 2015-227955 12 portions by weight • 2 parts by mass of the following compound F • Dichloromethane (primary solvent) 430 parts by weight • Methanol (second solvent) 64 parts by weight ───────────────────────────────

[0187] Compound F [Chemical Formula 18]

[0188] -Preparation of outer cellulose acylate concentrate- A cellulose acetate solution was prepared by adding 10 parts by mass of the following matting agent solution to 90 parts by mass of the above core cellulose acylate concentrate.

[0189] ─────────────────────────────── Matting solution ─────────────────────────────── • Silica particles with an average particle size of 20 nm (AEROSIL R972, manufactured by NIPPON AEROSIL CO., LTD.) 2 parts by weight • Dichloromethane (primary solvent) 76 parts by mass • Methanol (second solvent) 11 parts by weight · 1 part by mass of the above-mentioned core layer cellulose acylated concentrate ───────────────────────────────

[0190] -Preparation of cellulose acylated membrane 1- After filtering the core cellulose acylate concentrate and the outer cellulose acylate concentrate using filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm, the three layers of the core cellulose acylate concentrate and the outer cellulose acylate concentrate on both sides were simultaneously cast from the casting port onto a roller at 20°C (ring-belt casting machine). Next, the film was peeled off with a solvent content of approximately 20% by mass, and the two ends in the width direction of the film were fixed using a tenter frame clamp. It was then stretched laterally at a stretch ratio of 1.1 and dried. Further drying was then performed by conveying the film between rollers in a heat treatment apparatus to produce an optical film (transparent support) with a thickness of 40 μm, which was then used as cellulose acylate film 1. The in-plane retardation of the obtained cellulose acylate film 1 was 0 nm.

[0191] (Formation of photo-aligned film PA1) The coating solution PA1 for forming a photo-aligned film (described later) was continuously coated onto the cellulose acylated film 1 using a wire rod. The support with the coated film was dried with warm air at 140°C for 120 seconds, followed by polarized ultraviolet irradiation of the coating film (10 mJ / cm²). 2 Using an ultra-high pressure mercury lamp, a photo-aligned film PA1 was formed, and a TAC (triacetyl cellulose) membrane with the photo-aligned film was obtained. The thickness of the photo-aligned film PA1 was 0.5 μm.

[0192] ─────────────────────────────── Photo-aligned film forming coating solution PA1 ─────────────────────────────── • 100.00 parts by weight of the following polymer PA-1 • 8.25 parts by weight of the following acid-producing agent PAG-1 • 0.6 parts by weight of the following stabilizer DIPEA ·Xylene 1126.60 parts by weight 125.18 parts by weight of methyl isobutyl ketone ───────────────────────────────

[0193] Polymer PA-1 [Chemical Formula 19]

[0194] Acid-producing agent PAG-1 [Chemical Formula 20]

[0195] stabilizer DIPEA [Chemical Formula 21]

[0196] The optically anisotropic layer forming composition H1 described above was continuously coated onto the obtained photoalignment film PA1 using a wire rod to form a coating layer H1. Next, the coating layer H1 was heated at 100°C for 5 minutes and cooled to 60°C to form a dried coating. In the dried coating, the liquid crystal compound is a nematic phase. Then, using an LED lamp (center wavelength 365nm) at an illuminance of 200mW / cm², [the process was completed]. 2 An optically anisotropic layer H1 was fabricated on the photo-alignment film PA1 by irradiating it for 2 seconds under the specified irradiation conditions. The thickness of the optically anisotropic layer H1 was 1.9 μm.

[0197] The fabricated optical anisotropic layer H1 functions as a λ / 4 phase difference layer for light with a wavelength of 940 nm.

[0198] [Making of the C-plate] The aforementioned cellulose acylated membrane 1 was used as a temporary support. The cellulose acylated membrane 1 was passed through a dielectric heating roller at 60°C, and the membrane surface temperature was raised to 40°C. Then, a bar coater was used at a rate of 14 ml / m². 2 The coating amount was determined by applying an alkaline solution of the composition shown below to one side of the membrane and heating it to 110°C, then conveying it for 10 seconds using a steam-type far-infrared heater manufactured by Noritake Company Limited. Next, 3 ml / m² of pure water was coated onto the membrane using a bar coater. 2 Next, after repeating the water washing based on the spray coating machine and the dehydration based on the air knife three times, the membrane was conveyed in the drying zone at 70°C for 10 seconds to dry, thereby producing the alkali-saponified cellulose acylated membrane 1.

[0199] ─────────────────────────────── (Alkaline solution) ─────────────────────────────── 4.7 parts by weight of potassium hydroxide 15.8 parts by weight of water · Isopropanol 63.7 parts by weight Fluorinated surfactant SF-1 (C 14 H 29 O(CH2CH) 2O ) 20 H) 1.0 parts by weight ·Propylene glycol 14.8 parts by weight ───────────────────────────────

[0200] Using a #16 wire rod, the following orientation layer forming coating liquid 2 is continuously applied to the alkali-saponified cellulose acylate film 1. The cellulose acylate film 1 with the coating is dried with warm air at 60°C for 60 seconds, and then further dried with warm air at 100°C for 120 seconds, thereby forming the orientation layer.

[0201] ─────────────────────────────── (Coating liquid 2 for forming orientation layer) ─────────────────────────────── • Polyvinyl alcohol (manufactured by KURARAY CO.,LTD., PVA103) 2.4 parts by weight 1.6 parts by weight of isopropanol ·Methanol 36 parts by weight · 60 parts by weight of water ───────────────────────────────

[0202] The coating solution C1 used for forming the positive C-plate (described later) is applied onto the alignment layer. The resulting coating is cured at 60°C for 60 seconds, and then subjected to air treatment using 70 mW / cm². 2 Irradiation with a gas-cooled metal halide lamp (manufactured by EYE GRAPHICS Co., Ltd.) at 1000 mJ / cm 2 Ultraviolet light was used to fix its orientation state, thereby vertically aligning the liquid crystal compound and fabricating a TAC film with a positive C-plate C1. The obtained positive C-plate C1 has an Rth (550) of -130 nm.

[0203] ─────────────────────────────── (Coating liquid C1 for forming positive C-plate) ─────────────────────────────── • 80 parts by weight of the following liquid crystal compound L-11 • 20 parts by weight of the following liquid crystal compound L-12 • 1 part by weight of the following liquid crystal compound vertical alignment agent (S01) Ethylene oxide modified trimethylolpropane triacrylate (V#360, manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD.) 8 parts by weight • IRGACURE 907 (manufactured by BASF) 3 parts by weight ·KAYACURE DETX (manufactured by Nippon Kayaku Co., Ltd.) 1 part by weight • 0.4 parts by mass of the following compound B03 170 parts by weight of methyl ethyl ketone · 30 parts by weight of cyclohexanone ───────────────────────────────

[0204] Liquid crystal compound L-11 and liquid crystal compound L-12 [Chemical Formula 22]

[0205] Liquid crystal compound vertical alignment agent (S01) [Chemical Formula 23]

[0206] Compound B03 [Chemical Formula 24]

[0207] Using the UV adhesive composition described below, the positive C-plate C1 side of the TAC film having the positive C-plate C1 prepared above is attached to the optical anisotropic layer side of the TAC film having the optical anisotropic layer H1 described above, and the orientation layer and cellulose acylate film 1 on the optical anisotropic layer H1 side are removed to obtain a laminate (λ / 4 plate) containing a phase difference layer (optical anisotropic layer H1 and positive C-plate C1).

[0208] (Preparation of UV adhesive composition) The following UV adhesive composition was prepared. ─────────────────────────────── UV adhesive composition ─────────────────────────────── • CEL2021P (manufactured by Daicel Corporation) 70 parts by weight · 20 parts by weight of 1,4-Butanediol diglycidyl ether 10 parts by weight of 2-ethylhexyl glycidyl ether • The following CPI-100P 2.25 parts by weight ───────────────────────────────

[0209] CPI-100P [Chemical Formula 25]

[0210] The refractive indices nx, ny, and nz of the fabricated λ / 4 plate were measured using an Abbe refractometer (NAR-4T, manufactured by ATAGO CO.,LTD.) and a sodium lamp (λ=589nm) as the light source. Based on the measured values ​​of nx, ny, and nz, the Nz factor was calculated: Nz = (nx - nz) / (nx - ny). Furthermore, the refractive indices nx, ny, and nz were used to represent the refractive indices at a wavelength of 550nm. The Nz factor was 0.5.

[0211] After conditioning the fabricated λ / 4 plate at 20°C and 65% RH for 24 hours, it was cut into pieces with a flow direction (MD) × width direction (TD) of 200 mm × 15 mm (as per composition H1 used for coating the optical anisotropic layer). These pieces were then mounted on a testing machine (Shimadzu Corporation's "AG-IS" tensile testing machine) with a clamping interval of 100 mm and subjected to tensile testing at 1000 mm / min under 20°C and 65% RH conditions. The tensile modulus of elasticity was calculated based on the ratio of initial stress to initial strain. The tensile modulus of elasticity was 2.0 × 10⁻⁶. 3 MPa.

[0212] <<Layering of Linear Polarizer and λ / 4 Plate>> An adhesive layer (SK-2057, manufactured by Soken Chemical & Engineering Co., Ltd.) is applied to the surface of the optical anisotropic layer H1 on the λ / 4 plate to form an adhesive layer. This adhesive layer is then bonded to the surface opposite to the glass substrate of the aforementioned linear polarizer (light absorption anisotropic film 1) in a way that ensures close adhesion between the adhesive layer and the surface. A circular polarizer is thus obtained. Furthermore, the slow axis of the optical anisotropic layer H1 is oriented at 45° to the absorption axis of the light absorption anisotropic film 1. A circular polarizer was fabricated using this method.

[0213] (Example 11) Compared to Example 1, Example 11 uses a circular polarizer (cholesterol reflective type) instead of the LCF of the second polarizing filter, and the second polarizing filter is positioned on the subject side. Figure 1 The subject 13 side of the lens 20 shown is otherwise the same as in Embodiment 1. The following is an explanation of circular polarizers.

[0214] (Formation of the orientation film) A glass substrate was prepared as a support. An alignment film forming coating liquid P-1 was spin-coated onto the support. The support coated with the alignment film forming coating liquid P-1 was dried on a hot plate at 60°C for 60 seconds to form a coating film.

[0215] Coating solution P-1 for oriented film formation ─────────────────────────────── • 1.00 parts by weight of the following raw materials for photoorientation · 16.00 parts by weight of water 42.00 parts by weight of butoxyethanol 42.00 parts by weight of propylene glycol monomethyl ether ───────────────────────────────

[0216] Raw materials for photoorientation [Chemical Formula 26]

[0217] (Fabrication of photo-alignment film) The obtained coating was exposed to form a photo-aligned film P-1 with a thickness of 5 μm. Next, an optically anisotropic layer was formed by coating composition B-3 once onto the photo-alignment film P-1.

[0218] Composition B-3 (coating solution for forming cholesterol-type liquid crystal layers) ─────────────────────────────── · 100.00 parts by weight of the above-mentioned rod-shaped liquid crystal compound L-13 • Polymerization initiator (BASF, Irgacure OXE01) 1.00 parts by weight • 4.2 parts by weight of the following chiral reagent Ch-1 · 115.72 parts by weight of methyl ethyl ketone ───────────────────────────────

[0219] Rod-shaped liquid crystal compound L-13 (containing the following structure in the mass ratio shown on the right) [Chemical Formula 27]

[0220] Chiral reagent Ch-1 [Chemical Formula 28]

[0221] An optical anisotropic layer was fabricated as follows. First, a layer of composition B-1 is coated onto the photoalignment film P-1, and the coating is heated to 80°C on a hot plate. Then, at 80°C, a high-pressure mercury lamp at 300 mJ / cm² is used in a nitrogen atmosphere. 2 The coating was irradiated with ultraviolet light at a wavelength of 365 nm to fix the orientation of the liquid crystal compound, thereby creating an optically anisotropic layer. Regarding the optical anisotropy layer, Δn was confirmed using polarizing microscopy. 940 The film thickness d = Re (940) eventually becomes 470 nm. The fabricated laminate containing the optical anisotropic layer is a circular polarizer with a reflective cholesterol-type liquid crystal layer. The circular polarizer is reflective and reflects and diffracts right-handed circularly polarized light with a wavelength of 940 nm. When light is incident perpendicularly on the surface of the optical anisotropic layer, it reflects the right-handed circularly polarized light in the direction of a polar angle of 30° and does not diffract left-handed circularly polarized light (0° direction).

[0222] (Comparative Example 1) Compared to Example 2, in Comparative Example 1, the position of the second polarizing filter is on the subject side. Figure 1 The subject 13 side of the lens 20 shown is otherwise the same as in Embodiment 2. (Comparative Example 2) Compared to Example 6, in Comparative Example 2, the position of the second polarizing filter is on the subject side. Figure 1 The subject 13 side of the lens 20 shown is otherwise the same as in Example 6.

[0223] (Measurement of haze) The absorption anisotropy of light-absorbing anisotropic films 1 and 2, which are fabricated as the second polarizing filter, was measured using a haze meter (NDH2000 (manufactured by NIPPON DENSHOKU INDUSTRIES CO.,LTD.)).

[0224] (Evaluation of noise in the camera image) The noise level in the camera image is evaluated below. For the camera systems of Examples 1-11 and Comparative Examples 1 and 2, respectively, as follows: Figure 17 As shown, a reflector 50 is positioned directly opposite, and a reflector 52 is positioned at an angle, capturing reflected light from the mirror surface, which becomes noise. The reflector 50 is configured as lenses 20 and 22 (see reference). Figure 1 The optical axis C (reference) Figure 1 The mirror 52 is perpendicular to the surface 50a. The optical axis C of the lenses 20 and 22 is tilted relative to the surface 52a. by Figure 17 The mirrors 50 and 52 shown were used in the imaging systems of Examples 1-11 and Comparative Examples 1 and 2. The shutter speed was adjusted to keep the maximum brightness value within the image constant, thereby obtaining an image. The average brightness of the image was evaluated, and the noise of the image from the imaging system was evaluated relative to the evaluation value (average brightness value) in Example 1. The results are shown in the "Relative Average Brightness Value" column of Table 1 below. Note that the relative average brightness value for Example 1 is "1". A smaller relative average brightness value indicates less noise. Furthermore, the camera images were evaluated according to the following evaluation criteria, and the noise level of the camera images from the camera system was also evaluated. The results are also shown. Specifically, 10 testers evaluated each camera image using the following A to D ratings. The evaluations made by at least 8 of the 10 testers were taken as the overall evaluation of the camera image. Evaluation Criteria A: No noise was detected in the camera image. B: Slight noise was detected in the camera image. C: Noise was detected in the camera image, but the noise was not obvious. D: Noise was clearly detected in the camera image.

[0225] In Examples 1-11 and Comparative Examples 1 and 2, the average transmittance of the second polarizing filter was measured. The results are shown in Table 1 below. The second polarizing filters were all linear polarizers or had linear polarizers, so they are referred to as "average transmittance of the second linear polarizer" in Table 1 below. The average transmittance of the second polarizing filter (second linear polarizer) was measured as follows. First, the transmittance at wavelengths above 400 nm and below 700 nm was measured using a V-660 UV-Vis-NIR spectrophotometer (JASCO Corporation). Then, the average transmittance (in %) of the second polarizing filter (second linear polarizer) was calculated by arithmetically averaging the transmittance at each wavelength.

[0226] [Table 1]

[0227] As shown in Table 1, compared with Comparative Examples 1 and 2, Examples 1-11 yielded video images with lower relative average brightness values ​​and reduced noise. The relative average brightness value corresponds to the sensory evaluation of noise. As can be seen from Examples 1 to 11, regardless of the position of the second polarizing filter, among the light absorption anisotropic film 1, the light absorption anisotropic film 2, the wire grid polarizer, the combination of the wire grid polarizer and the venetian blind, and the LCF, the LCF can minimize noise. As can be seen from Examples 1 to 11, the absorptive type of the second polarizing filter is more effective at reducing noise than the reflective type. As can be seen from Examples 4 and 8, the lower the haze of the second polarizing filter, the more noise it can reduce. Furthermore, as can be seen from Examples 1 to 7, the second line polarizer can reduce noise when the average transmittance of visible light is 70% or more. In addition, when a second polarizing filter is arranged on the subject side as in Example 9, the oblique incidence component increases, but the relative average brightness value and noise are the average values ​​of Examples 1 to 11. Furthermore, by configuring the second polarizing filter as having a linear polarizer and a λ / 4 plate (the second circular polarizing filter) as in Example 10, the same results as in Examples 1 and 3 were obtained even when the filter was positioned on the subject side. Furthermore, by setting the second polarizing filter to a structure having a cholesterol-type liquid crystal layer (the second circular polarizing filter) as in Example 11, the same results as in Examples 1 and 3 were obtained even when the filter was placed on the subject side. Symbol Explanation

[0228] 10, 46 - Camera system; 12 - Light source; 13 - Subject; 14 - Camera device; 16 - First polarizing filter; 16a, 34a, 36a, 50a, 52a, 60a, 62a - Surface; 16b, 24b, 32b, 36b, 60b, 62b - Back surface; 17 - Display control unit; 18 - Control unit; 19 - Display unit; 20, 22 - Lens; 24 - Second polarizing filter; 26 - Image sensor; 27 - Optical system; 28 - First linear polarizer; 29 - 2nd linear polarizer, 30-2nd polarizing filter, 32-1st layer, 34-2nd layer, 36-2nd polarizing filter, 40-vehicle, 42-seat, 43-driver, 44-occupant, 48-operation unit, 50, 52-mirrors, 60-1st circular polarizing filter, 62-2nd circular polarizing filter, 63, 65-linear polarizer, 64, 66-λ / 4 plate, C-optical axis, D1, D2-polarization axes, Li-reflected light, Lo-outgoing light, S-stray light, X, Y, Z-directions.

Claims

1. A camera system, comprising: Light source, emitting infrared rays; A camera device for capturing images of a subject illuminated by infrared light emitted from the light source; and A first polarizing filter is disposed between the light source and the subject to polarize the infrared light emitted from the light source. The camera device includes a lens, a second polarizing filter that polarizes the infrared light, and an image sensor, starting from the incident side.

2. The camera system according to claim 1, wherein, The first polarizing filter includes a first linear polarizer. The second polarizing filter includes a second linear polarizer. The polarization axis of the first linear polarizer is orthogonal to the polarization axis of the second linear polarizer.

3. The camera system according to claim 2, wherein, The second line polarizer is an absorption-type line polarizer.

4. The camera system according to claim 2 or 3, wherein, The second polarizer has an average transmittance of over 70% for visible light.

5. The camera system according to claim 1, wherein, The second polarizing filter is an optical element having an absorption axis for infrared light in the in-plane direction, and when linearly polarized light of infrared light orthogonal to the absorption axis is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at a direction tilted 45° relative to the normal direction, the absorbance is greater when irradiated from the direction tilted 45° relative to the normal direction than when irradiated from the normal direction.

6. The camera system according to any one of claims 1, 2, and 5, wherein, The haze of the second polarizing filter is below 1.

7. The camera system according to any one of claims 1 to 3, wherein, The subject being filmed is at least one of the vehicle driver and the occupants of the vehicle, and the camera system is used for an in-vehicle occupant monitoring system.

8. A camera system, comprising: Light source, emitting infrared rays; A camera device for capturing images of a subject illuminated by infrared light emitted from the light source; and A first polarizing filter is disposed between the light source and the subject to polarize the infrared light emitted from the light source. The imaging device includes, starting from the incident side, a second polarizing filter, a lens, and an image sensor to polarize the infrared light. The second polarizing filter is an optical element having an absorption axis for infrared light in the in-plane direction, and when linearly polarized infrared light orthogonal to the absorption axis is irradiated from the normal direction of the optical element and from an azimuth angle orthogonal to the absorption axis at a direction tilted 45° relative to the normal direction, the absorbance is greater when irradiated from the direction tilted 45° relative to the normal direction than when irradiated from the normal direction.

9. A camera system, comprising: Light source, emitting infrared rays; A camera device for capturing images of a subject illuminated by infrared light emitted from the light source; and A first circularly polarizing filter is disposed between the light source and the subject to cause the infrared light emitted from the light source to be circularly polarized. The imaging device includes, starting from the incident side, a second circularly polarizing filter, a lens, and an image sensor to circularly polarize the infrared light.

10. The camera system according to claim 9, wherein, The second circular polarizing filter includes a linear polarizer and a λ / 4 plate. The Nz factor of the λ / 4 plate is greater than 0 and less than 1.

11. The camera system according to claim 10, wherein, The linear polarizer of the second circular polarizing filter is an absorption-type linear polarizer.

12. The camera system according to claim 10 or 11, wherein, The linear polarizer of the second circular polarizing filter has an average transmittance of more than 70% for visible light.

13. The camera system according to claim 9, wherein, The haze of the second circular polarizing filter is below 1.

Images