Polarization image measurement device

Abstract

Provided is a polarization image measurement device that can be further reduced in size. This polarization image measurement device comprises: an infrared light source (12) that emits infrared light to an inspection target; a lens (14) that causes the infrared light emitted from the infrared light source (12) to diverge; a circular polarizer (16) with a thickness of 1 mm or less that converts the divergent infrared light from the lens (14) into circularly polarized light; a first image sensor (18) that receives reflected light obtained when the circularly polarized light obtained by the conversion by the circular polarizer (16) is reflected off an inspection target (P); and a polarization separation filter (20) that is disposed on an optical path between the inspection target (P) and the first image sensor (18) and that separates the reflected light into a plurality of polarized rays of light.

Description

Polarized image measurement device

[0001] The present invention relates to a polarization image measurement device.

[0002] BACKGROUND ART In various fields such as the medical field and the semiconductor field, polarized light is irradiated onto an object to be inspected, and the internal condition of the object is inspected from the polarization state of the reflected light.

[0003] For example, Patent Document 1 discloses a polarization image measurement device that measures a polarization image of the surface layer of a predetermined part of a living organism, and that includes: a polarized irradiation means that irradiates the predetermined part with irradiation light of a plurality of polarization states from the surface layer of the predetermined part; an imaging means that captures the reflected light of a plurality of polarization states from the surface layer of the predetermined part of the irradiation light of the plurality of polarization states irradiated by the polarized irradiation means; and a polarization conversion processing means that performs polarization conversion processing on the plurality of light intensity image information of the reflected light of the plurality of polarization states each captured by the imaging means, converting it into polarization characteristic image information with predetermined polarization characteristics in order to distinguish superficial tissue that appears on the surface layer of the predetermined part from superficial tissue, and obtains a polarization characteristic image with polarization characteristics based on the polarization characteristic image information.

[0004] Furthermore, Patent Document 2 describes an optical inspection device for inspecting an object to be inspected, the optical inspection device including a light source that outputs coherent light, a light splitting unit that splits the coherent light from the light source into inspection light and reference light, a first arm that irradiates one side of the object to be inspected with the inspection light and transmits it therethrough, a second arm through which the reference light propagates, a multiplexing interference unit that multiplexes the inspection light from the first arm that has transmitted through the object to be inspected with the reference light from the second arm to generate interference light, a light detection unit that detects the light intensity of the interference light, and a scanning mechanism that moves the object to be inspected relatively to the inspection light. Patent Document 2 describes that the optical inspection device described in Patent Document 2 is used as an inspection device for internal defects of semiconductor substrates.

[0005] Furthermore, Patent Document 3 describes an endoscope tip device that includes a circularly polarized light-emitting diode for illumination and a circularly polarized light-emitting diode for detection of scattered light, in which the circularly polarized light-emitting diode includes a pair of magnetic metal electrodes whose magnetization directions are antiparallel to each other, and the circularly polarized light-emitting diode for detection is positioned so as to detect scattered light at a predetermined angle determined according to the measurement depth with respect to the illumination axis of the circularly polarized light-emitting diode for illumination.

[0006] JP 2012-010757 A JP 2023-113092 A JP 2020-130816 A

[0007] There is a demand for further miniaturization of polarization image measurement devices, which irradiate polarized light onto an object to be inspected, detect the polarization state of the reflected light, and inspect the internal condition of the object to be inspected, so that they can be installed, for example, at the tip of an endoscope.

[0008] However, in conventional polarization image measurement devices, as described in Patent Document 1, for example, the polarized light irradiation means has a rotation drive mechanism that rotates the retardation plate in order to irradiate irradiation light of multiple polarization states, which makes it difficult to reduce the size.

[0009] Furthermore, the endoscope tip device described in Patent Document 3 irradiates circularly polarized light using a circularly polarized light-emitting diode equipped with a pair of magnetic metal electrodes whose magnetization directions are antiparallel to each other. However, such circularly polarized light-emitting diodes have many issues to be resolved before they can be put into practical use.

[0010] An object of the present invention is to solve the problems of the conventional technology and to provide a polarization image measurement device that can be made smaller.

[0011] In order to solve this problem, the present invention has the following configuration. [1] A polarization image measurement device comprising: an infrared light source that emits infrared light onto an inspection object; a lens that diverges the infrared light emitted from the infrared light source; a circular polarizer having a thickness of 1 mm or less that converts the infrared light diverged by the lens into circularly polarized light; a first image sensor that receives light that is reflected by the inspection object and the circularly polarized light converted by the circular polarizer; and a polarization separation filter that is disposed on an optical path between the inspection object and the first image sensor and separates the reflected light into light of a plurality of polarization states. [2] The polarization image measurement device according to [1], wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the Nz factor of the λ / 4 plate is greater than 0 and less than 1. [3] The polarization image measurement device according to [1] or [2], wherein the circular polarizer has a curved structure. [4] The polarized image measurement device according to any one of [1] to [3], wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the tensile modulus of the λ / 4 plate is 1 MPa to 10 GPa. [5] The polarized image measurement device according to any one of [1] to [4], wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the λ / 4 plate is formed using a liquid crystal compound. [6] The polarized image measurement device according to any one of [1] to [5], wherein the circular polarizer includes an absorptive linear polarizer. [7] The polarized image measurement device according to any one of [1] to [5], wherein the circular polarizer includes a cholesteric liquid crystal layer. [8] The polarized image measurement device according to any one of [1] to [7], wherein the polarization separation filter is a patterned wire grid polarizer, and wherein the polarization separation filter is adjacent to the first image sensor. [9] The polarized image measurement device according to any one of [1] to [7], wherein the polarization separation filter is a liquid crystal diffractive film that selectively diffracts right-handed circularly polarized light and left-handed circularly polarized light.

[10] The polarized image measurement device according to [9], wherein the polarization separation filter selectively diffracts light of wavelengths in the infrared light range.

[11] The polarized image measurement device according to [9] or

[10] , wherein the polarization separation filter is a reflective liquid crystal diffractive film.

[12] The polarized image measurement device according to any of [1] to

[11] , further comprising a second light source that emits light of a wavelength different from the infrared light source, and wherein the light emitted from the second light source is converted into circularly polarized light by a circular polarizer.

[13] The polarized image measurement device according to

[12] , wherein the light emitted from the second light source is infrared light.

[14] The polarized image measurement device according to

[12] , further comprising a white light source having multiple luminance peaks, and wherein the wavelength of the light emitted from the second light source is a wavelength between the multiple luminance peaks.

[15] The polarized image measurement device according to any one of [1] to

[14] , further comprising a white light source having multiple luminance peaks and a second image sensor that captures light reflected from the light emitted from the white light source by an object under inspection, and wherein information obtained by the first image sensor is superimposed on an image obtained by the second image sensor for display.

[16] The polarized image measurement device according to any one of [1] to

[15] , wherein the first image sensor is sensitive to both the visible light region and the infrared light region.

[17] The polarized image measurement device according to any one of [1] to

[16] , for use in an endoscope system.

[18] A polarization image measurement device comprising: an infrared light source that emits infrared light onto an object to be inspected; a circular polarizer having a thickness of 1 mm or less that converts the infrared light emitted from the infrared light source into circularly polarized light; a first image sensor that receives light that is reflected by the object to be inspected and is the circularly polarized light converted by the circular polarizer; and a polarization separation filter that is arranged on an optical path between the object to be inspected and the first image sensor and separates the reflected light into light of a plurality of polarization states.

[0012] According to the present invention, it is possible to provide a polarization image measurement device that can be made even more compact.

[0013] FIG. 1 is a diagram conceptually illustrating an example of a polarization image measurement device of the present invention. FIG. 2 is a diagram conceptually illustrating an example of a light irradiation system included in the polarization image measurement device shown in FIG. 1. FIG. 3 is a diagram conceptually illustrating another example of a light irradiation system included in the polarization image measurement device shown in FIG. 1. FIG. 4 is a diagram conceptually illustrating an example of a light receiving system included in the polarization image measurement device of the present invention. FIG. 5 is a plan view conceptually illustrating the patterned wire grid polarizer shown in FIG. 4. FIG. 6 is a diagram conceptually illustrating another example of a light receiving system included in the polarization image measurement device of the present invention. FIG. 7 is a diagram conceptually illustrating another example of a light receiving system included in the polarization image measurement device of the present invention. FIG. 8 is a diagram conceptually illustrating another example of a light irradiation system included in the polarization image measurement device of the present invention. FIG. 9 is a graph conceptually illustrating the relationship between wavelength and luminance. FIG. 10 is a graph conceptually illustrating the relationship between wavelength and luminance. FIG. 11 is a diagram conceptually illustrating an example of an endoscopic system including the polarization image measurement device of the present invention. FIG. 12 is a diagram for explaining the evaluation method of the examples. Fig. 13 is a diagram for explaining the evaluation method of the examples. Fig. 14 is a diagram for explaining the evaluation method of the examples. Fig. 15 is a diagram for explaining the evaluation method of the examples.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The polarized light image measuring device of the present invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings.

[0015] It should be noted that the drawings shown below are conceptual diagrams for explaining the present invention, and the shapes, sizes (size ratios), positional relationships, etc. of the components differ from the actual ones.

[0016] In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0017] In this specification, "orthogonal" does not mean an angle of 90° exactly, but means 90°±10°, preferably 90°±5°. Furthermore, "parallel" does not mean an angle of 0° exactly, but means 0°±10°, preferably 0°±5°. Furthermore, "45°" does not mean an angle of 45° exactly, but means 45°±10°, preferably 45°±5°. In addition, when referring to angles, it does not mean an exact angle, but means a range of ±10°, preferably a range of ±5°.

[0018] In this specification, "absorption axis" refers to the polarization direction in which absorbance is maximized in a plane when linearly polarized light is incident. "Reflection axis" refers to the polarization direction in which reflectance is maximized in a plane when linearly polarized light is incident. "Transmission axis" refers to the direction perpendicular to the absorption axis or reflection axis in a plane. "Slow axis" refers to the direction in which refractive index is maximized in a plane.

[0019] In this specification, unless otherwise specified, phase difference refers to in-plane retardation and is referred to as Re(λ). Here, Re(λ) represents in-plane retardation at wavelength λ. In this specification, unless the wavelength at which retardation is measured is specified, the measurement wavelength is 550 nm. In addition, in this specification, retardation in the thickness direction at wavelength λ is referred to as Rth(λ). Re(λ) and Rth(λ) can be values ​​measured at wavelength λ using an AxoScan OPMF-1 (manufactured by Optoscience). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the slow axis direction (°) Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d can be calculated. Note that R0(λ) is expressed as a numerical value calculated by AxoScan, but it means Re(λ). Furthermore, nx represents the refractive index in the in-plane slow axis direction, ny represents the refractive index in the in-plane direction perpendicular to the in-plane slow axis, and nz represents the refractive index in the thickness direction.

[0020] In this specification, the refractive indices nx, ny, and nz can also be measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ=589 nm) as a light source. When measuring wavelength dependency, measurements can be made using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter.

[0021] Alternatively, values ​​from the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Examples of average refractive index values ​​for major optical films are listed below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0022] [Polarized Image Measurement Device] The polarized image measurement device of the present invention is a polarized image measurement device comprising: an infrared light source that emits infrared light onto an object to be inspected; a lens that diverges the infrared light emitted from the infrared light source; a circular polarizer with a thickness of 1 mm or less that converts the infrared light diverged by the lens into circularly polarized light; a first image sensor that receives light that is reflected by the object to be inspected and is the circularly polarized light converted by the circular polarizer; and a polarization separation filter that is arranged on the optical path between the object to be inspected and the first image sensor and separates the reflected light into light of a plurality of polarization states.

[0023] FIG. 1 is a diagram conceptually showing an example of a polarization image measurement device according to the present invention.

[0024] 1 includes an infrared light source 12, a lens 14, a circular polarizer 16, a first image sensor, and a polarization separation filter 20. In the following description, the part for irradiating the inspection object P with infrared light, including the infrared light source 12, the lens 14, and the circular polarizer 16, is also referred to as a light irradiation system, and the part for receiving reflected light from the inspection object P, including the first image sensor and the polarization separation filter 20, is also referred to as a light receiving system.

[0025] In the light irradiation system of the polarization image measurement device 10, a lens 14 and a circular polarizer 16 are arranged in this order on the optical path of light emitted by an infrared light source 12. In the light irradiation system, infrared light is emitted from the infrared light source 12, the lens 14 diverges the infrared light emitted by the infrared light source 12, and the circular polarizer converts the infrared light diverged by the lens 14 into circularly polarized light, and the circularly polarized infrared light is irradiated onto the inspection object P.

[0026] The circularly polarized infrared light irradiated by the light irradiation system is reflected from the surface and / or scattered internally by the inspection object P. Hereinafter, the light reflected from the surface of the inspection object P and the light scattered internally are collectively referred to as reflected light.

[0027] The light receiving system receives and detects the circularly polarized infrared light irradiated by the light irradiation system and reflected by the inspection object P. In the light receiving system of the polarization image measurement device 10, a polarization separation filter 20 is disposed in front of the light receiving surface of the first image sensor 18, i.e., between the inspection object P and the first image sensor 18.

[0028] Here, the polarization state of the scattered light inside the test object P varies depending on the internal structure of the test object P. For example, the size and density of cell nuclei in normal tissues in a living body differ from the size and density of cell nuclei in tumor tissues (abnormal tissues) such as cancer. Furthermore, the shape of cell nuclei in tumor tissues tends to be irregular. Therefore, when circularly polarized infrared light is irradiated, the polarization state of the scattered light from normal tissues differs from the polarization state of the scattered light from tumor tissues, and the polarization state of the scattered light from tumor tissues tends to be more distorted than that of the scattered light from normal tissues. In other words, when circularly polarized light irradiated onto the test object P is scattered at a tumor tissue, the degree of circular polarization is lower than that of the scattered light from normal tissues.

[0029] In the light receiving system of the polarization image measurement device 10, the reflected light from the object P is separated into light of multiple polarization states by the polarization separation filter 20, and each separated light of each polarization state is received by the first image sensor 18. The data obtained by the first image sensor 18 is transmitted to, for example, a polarization image processing unit (not shown). The polarization image processing unit can calculate the polarization state of the reflected light from the amount of light of each polarization state received by the first image sensor. For example, normal tissue can be distinguished from abnormal tissue, particularly cancerous tissue, based on the detected degree of circular polarization of the reflected light. Furthermore, the size and density of cell nuclei in abnormal tissue can be determined from the degree of circular polarization of the reflected light.

[0030] Here, in the polarized image measurement device of the present invention, the light irradiation system has a lens 14 that diverges infrared light emitted from an infrared light source 12, and a circular polarizer 16 that converts the infrared light diverged by the lens 14 into circularly polarized light, and the thickness of the circular polarizer is 1 mm or less.

[0031] As described above, there has been a demand for further miniaturization of polarization image measurement devices, for example, in order to provide the polarization image measurement device at the tip of an endoscope.

[0032] If the infrared light source (the light irradiation port of the infrared light source) is made smaller in order to make the polarization image measurement device smaller, the range over which the light is irradiated will become narrower, and the range over which a polarization image can be acquired, i.e., the inspection range, will become narrower.

[0033] In contrast, the polarized image measurement device of the present invention has a lens 14 that diverges the infrared light emitted from the infrared light source 12, so that the range irradiated with light, i.e., the inspection range, can be widened using a small infrared light source 12.

[0034] Here, if the circular polarizer 16 that converts the infrared light emitted by the infrared light source 12 into circularly polarized light is placed between the infrared light source 12 and the lens 14, the circularly polarized light converted by the circular polarizer 16 will be disturbed when it is diverged by the lens 14, resulting in a decrease in measurement accuracy. For this reason, in the present invention, the circular polarizer 16 is placed on the opposite side of the lens 14 from the infrared light source 12, i.e., downstream of the lens 14 in the optical path of the infrared light emitted by the infrared light source 12.

[0035] Furthermore, when the circular polarizer 16 is positioned downstream of the lens 14, the infrared light enters the circular polarizer 16 after being diverged by the lens 14, resulting in amplified infrared light entering the circular polarizer 16. As will be described later, the preferable divergence angle of light by the lens 14 is very large, approximately 140° to 170°, and therefore the required size (in-plane size) of the circular polarizer 16 changes significantly with changes in the thickness of the circular polarizer 16 (see FIG. 2 ). Therefore, if the thickness of the circular polarizer 16 is large, the required size of the circular polarizer 16 becomes very large, resulting in a large polarization image measurement device. In contrast, in the polarization image measurement device of the present invention, the thickness of the circular polarizer 16 is set to 1 mm or less, thereby reducing the required size of the circular polarizer 16 and enabling the polarization image measurement device to be miniaturized.

[0036] From the viewpoint of reducing the required size of the circular polarizer 16, the thickness of the circular polarizer 16 is 1 mm or less, preferably 0.5 mm or less, and more preferably 0.3 mm or less. On the other hand, from the viewpoint of sufficiently converting incident light into circularly polarized light, the thickness of the circular polarizer 16 is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more.

[0037] The thickness of the circular polarizer 16 may be determined by cutting the circular polarizer 16 into 100 mm pieces in any one direction, measuring the thickness of 10 of the cut-out films every 0.48 mm in the width direction of the film using a contact web thickness meter (manufactured by Meisan Co., Ltd., product name "RC-101"), and calculating the arithmetic mean value of the measured values.

[0038] From the viewpoints of reducing the required size of the circular polarizer 16 and increasing the light utilization efficiency, the shortest distance between the circular polarizer 16 and the lens 14 is preferably 2 mm or less, more preferably 0.05 mm to 1 mm, and even more preferably 0.1 mm to 0.5 mm. Furthermore, the circular polarizer 16 and the lens 14 may be at least partially in contact with each other.

[0039] <Infrared Light Source> The infrared light source 12 is not particularly limited as long as it can emit infrared light of a predetermined wavelength. For example, a laser that emits a laser beam of a predetermined narrow wavelength band, an LED (Light Emitting Diode), a xenon lamp, a fluorescent lamp, a mercury lamp, or the like can be used. Note that when using a xenon lamp, a fluorescent lamp, a mercury lamp, or the like, a color filter that transmits the predetermined narrow wavelength band or a so-called bandpass filter must be used. A laser, an LED, or the like may be combined with a filter. Here, the wavelength (peak wavelength) of the infrared light emitted by the infrared light source 12 is not particularly limited, but is preferably 700 nm to 1300 nm, and more preferably 800 nm to 1000 nm. The half-width is preferably, for example, 5 nm to 50 nm, and more preferably 10 nm to 20 nm.

[0040] Furthermore, the infrared light emitted by the infrared light source 12 may be guided by a light guide such as an optical fiber and incident on the lens 14. In other words, the polarization image measurement device 10 may have a light guide between the infrared light source 12 and the lens. This point will be described later.

[0041] <Lens> The lens 14 is a member having a lens effect of diverging the infrared light emitted by the infrared light source 12. The lens 14 is not limited as long as it can diverge incident light, and a conventionally known concave lens, a pair of lenses having the effect of a concave lens, or the like can be used. As the concave lens, any of a plano-concave lens, a biconcave lens, and a concave meniscus lens can be used, but from the viewpoint of arranging the circular polarizer 16 in contact with the lens 14 as described below, a plano-concave lens or a concave meniscus lens is preferable. Furthermore, a flat lens such as a Fresnel lens or a liquid crystal diffractive lens can also be used.

[0042] The divergence angle (spread angle) of the infrared light diverged by the lens 14 is preferably 90° to 180°, more preferably 120° to 175°, and even more preferably 140° to 170°.

[0043] Furthermore, from the viewpoint of reducing the required size of the circular polarizer 16, it is preferable that the distance between the lens 14 and the circular polarizer 16 is short. In order to reduce the distance between the lens 14 and the circular polarizer 16, it is preferable that the thickness of the lens 16 is thin. Specifically, the center thickness of the lens 16 is preferably 0.01 mm to 2 mm, more preferably 0.05 mm to 1 mm, and even more preferably 0.1 mm to 0.5 mm.

[0044] <Circular Polarizer> The circular polarizer 16 is a member that converts incident infrared light into circularly polarized light. Since the infrared light emitted from the infrared light source 12 is basically unpolarized light, the circular polarizer 16 converts the unpolarized light into circularly polarized light.

[0045] The circular polarizer 16 may be a combination of a linear polarizer and a λ / 4 plate, or may be a cholesteric liquid crystal layer.

[0046] 2 is a conceptual diagram illustrating an example of a light irradiation system in the polarization image measurement device of the present invention. The light irradiation system shown in Fig. 2 includes a light guide 30, a lens 14 disposed on the light-emitting end face side of the light guide 30, and a circular polarizer 16a disposed downstream of the lens 14.

[0047] The circular polarizer 16a has a linear polarizer 22 and a λ / 4 plate 24. The circular polarizer 16a is laminated so that the angle between the transmission axis of the linear polarizer 22 and the slow layer axis of the λ / 4 plate 24 is approximately 45°, and converts unpolarized light incident from the linear polarizer 22 side into circularly polarized light.

[0048] In the circular polarizer 16a, the total thickness of the linear polarizer 22 and the λ / 4 plate 24 is 1 mm or less.

[0049] Furthermore, as in the example shown in Fig. 3, the circular polarizer 16b may have a curved structure. Fig. 3 is a conceptual diagram showing a portion of another example of a light irradiation system in the polarization image measurement device of the present invention. The light irradiation system shown in Fig. 3 has a lens 14 and a circular polarizer 16b laminated on one surface of the lens 14. In the example shown in Fig. 3, the circular polarizer 16b has a linear polarizer 22b and a λ / 4 plate 24b.

[0050] In the example shown in FIG. 3, the lens 14 is a concave meniscus lens, and the circular polarizer 16b is disposed in contact with the convex surface of the lens 14 and curved along this curved surface.

[0051] Infrared light diverged by a lens and incident on a circular polarizer (λ / 4 plate) is incident from a direction approximately perpendicular to the circular polarizer near the center (the position where the optical axis of the lens passes through) (see Figure 2). Therefore, the λ / 4 plate acts to impart an appropriate λ / 4 phase difference to the incident infrared light. In contrast, at positions away from the center, the infrared light is incident on the circular polarizer from an oblique direction (the angle (polar angle) relative to the normal to the surface of the circular polarizer is greater than 0°). Therefore, the phase difference imparted by the λ / 4 plate to the incident infrared light deviates from λ / 4, and the converted infrared light may become elliptically polarized.

[0052] In contrast, by configuring the circular polarizer to have a curved structure, infrared light can be incident on the circular polarizer from a direction close to perpendicular to the direction of incidence, even at a position away from the center. This allows the phase difference given to the incident infrared light to approach λ / 4, and the incident infrared light can be appropriately converted into circularly polarized light.

[0053] 3, the circular polarizer 16b includes a linear polarizer 22b and a λ / 4 plate 24b, but this is not limiting, and even when the circular polarizer includes a cholesteric liquid crystal layer, it is preferable to configure the circular polarizer to have a curved structure. Furthermore, in the example shown in Fig. 3, the circular polarizer 16b is configured to be curved by being placed in contact with the curved surface of the lens 14, but this is not limiting, and the circular polarizer 16b may be configured to be curved by being placed at a distance from the lens 14.

[0054] [Linear Polarizer] The linear polarizer 22 is not particularly limited as long as it acts as a linear polarizer for infrared light of the wavelength emitted by the infrared light source 12 .

[0055] The linear polarizer 22 may be a reflective linear polarizer, but an absorptive linear polarizer is preferable. An absorptive linear polarizer absorbs incident light linearly polarized in the absorption axis direction and transmits light linearly polarized in the transmission axis direction. The use of an absorptive linear polarizer allows for miniaturization and suppresses stray light. A typical polarizer can be used as the linear polarizer. For example, it may be a polarizer obtained by dyeing a dichroic material onto polyvinyl alcohol or other polymer resin and then stretching the material to orient the material, or a polarizer obtained by utilizing the orientation of a liquid crystal compound to orient the dichroic material. From the viewpoints of availability and increasing the degree of polarization, a polarizer obtained by dyeing polyvinyl alcohol with iodine and stretching the material is preferable.

[0056] The thickness of the linear polarizer 22 is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. If the linear polarizer 22 is thin, the circular polarizer can be made 1 mm or less, and as will be described later, when the circular polarizer is curved, cracks, breakage, and the like can be prevented.

[0057] The single plate transmittance of the linear polarizer 22 is preferably 40% or more, and more preferably 42% or more. The degree of polarization is preferably 90% or more, more preferably 95% or more, and even more preferably 99% or more. In this specification, the single plate transmittance and degree of polarization of the linear polarizer can be measured using an automatic polarizing film measuring device: VAP-7070 (manufactured by JASCO Corporation).

[0058] The linear polarizer 22 is also preferably a light-absorption anisotropic layer containing a liquid crystal compound and a dichroic material. A linear polarizer containing a liquid crystal compound and a dichroic material is preferred because it can be made thin and is less likely to crack or break even when stretched, molded, etc. The thickness of the light-absorption anisotropic layer is not particularly limited, but from the viewpoint of thinning, it is preferably 0.1 to 8 μm, and more preferably 0.3 to 5 μm.

[0059] A linear polarizer containing a liquid crystal compound and a dichroic material can be produced by referring to, for example, JP 2020-023153 A. From the viewpoint of improving the polarization degree of the linear polarizer, the light absorption anisotropic layer preferably has a degree of orientation of the dichroic material of 0.95 or more, more preferably 0.97 or more.

[0060] As the liquid crystal compound, either a low molecular weight liquid crystal compound or a polymeric liquid crystal compound can be used. Here, "low molecular weight liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. Furthermore, "polymeric liquid crystal compound" refers to a liquid crystal compound that has a repeating unit in its chemical structure. Examples of polymeric liquid crystal compounds include the thermotropic liquid crystal polymers described in JP 2011-237513 A. Furthermore, polymeric liquid crystal compounds preferably have a crosslinkable group (e.g., an acryloyl group or a methacryloyl group) at their terminals. The liquid crystal compounds may be used alone or in combination of two or more. It is also preferable to use a polymeric liquid crystal compound and a low molecular weight liquid crystal compound in combination.

[0061] The content of the liquid crystal compound is preferably 25 to 2,000 parts by mass, more preferably 33 to 1,000 parts by mass, and even more preferably 50 to 500 parts by mass, relative to 100 parts by mass of the content of the dichroic substance in the composition. When the content of the liquid crystal compound is within the above range, the degree of orientation of the linear polarizer is further improved.

[0062] The dichroic substance contained in the composition for forming an optically absorptive anisotropic layer for forming the optically absorptive anisotropic layer can be any conventionally known dichroic substance (dichroic dye) as long as it is an infrared absorbing substance.

[0063] In the present invention, two or more dichroic substances may be used in combination, and for example, from the viewpoint of obtaining a high degree of polarization over a wider wavelength range, it is preferable to use two or more dichroic substances having different maximum absorption wavelengths in combination. Dichroic substances having a maximum absorption wavelength in the infrared light region are described in WO 2022 / 215752, Japanese Patent No. 4148548, JP 2009-109774 A, JP 2008-255323 A, etc.

[0064] When the linear polarizer is made of a light-absorbing anisotropic layer containing a liquid crystal compound and a dichroic substance, the linear polarizer may include a support, an alignment layer, etc., but the support and alignment layer may be temporary supports that are peeled off and removed when producing a circular polarizer. When a temporary support is used, the circular polarizer can be made thinner by peeling off and removing the temporary support after transferring the light-absorbing anisotropic layer to a λ / 4 plate, and further, the adverse effect of the retardation of the temporary support on the polarization degree of transmitted light can be eliminated, which is preferable.

[0065] The type of support is not particularly limited, but it is preferable that the support be transparent to the infrared light of the wavelength emitted by the infrared light source 12 .

[0066] As the reflective linear polarizer, a conventionally known linear polarizer such as a wire grid polarizer can be used.

[0067] A wire-grid polarizer transmits one polarized light and reflects the other polarized light by utilizing the birefringence of thin metal wires. Wire-grid polarizers consist of metal wires arranged periodically and are primarily used as polarizers in the terahertz wave band. For a wire grid to function as a polarizer, the wire spacing must be sufficiently smaller than the wavelength of the incident electromagnetic wave. In wire-grid polarizers, the metal wires are arranged at equal intervals. Polarized light components polarized parallel to the longitudinal direction of the metal wires are reflected by the wire-grid polarizer, while polarized light components polarized perpendicular to the longitudinal direction are transmitted through the wire-grid polarizer.

[0068] Commercially available wire grid polarizers can be used, such as wire grid polarizer filters 50x50 and NT46-636 manufactured by Edmund Optics, and WGF (registered trademark) manufactured by Asahi Kasei Corporation.

[0069] The wire grid polarizer is not limited to those using metal wires, and a wire grid polarizer based on a resin film may also be used, such as MLP-WG manufactured by Mitate Imaging Co., Ltd.

[0070] [λ / 4 Plate] The λ / 4 plate 24 is a phase difference plate that has the function of converting linearly polarized light of a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). More specifically, it is a plate that exhibits an in-plane retardation Re of λ / 4 (or an odd multiple thereof) at a specific wavelength λ nm. In this example, the λ / 4 plate 24 acts as a λ / 4 plate with respect to the infrared light of wavelength λ emitted by the infrared light source 12. Note that the in-plane retardation Re(λ) of the λ / 4 plate 24 may have an error of about 25 nm around the ideal value (λ / 4 nm).

[0071] The λ / 4 plate 24 used in the present invention may be composed of a single retardation layer, or may be composed of two or more retardation layers laminated by lamination, sequential formation, or other techniques. The retardation layer referred to here is a layer that exhibits optical anisotropy. Examples of retardation layers include layers in which at least two of nx, ny, and nz are different. nx represents the refractive index in the direction perpendicular to the thickness direction of the retardation layer (in-plane direction) and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the retardation layer and perpendicular to the nx direction. nz represents the refractive index in the thickness direction of the retardation layer. The λ / 4 plate 24 may also have a support or the like that supports the retardation layer.

[0072] The material constituting the retardation layer is not particularly limited, and examples thereof include a liquid crystal compound and a polymer. A liquid crystal compound can form a retardation layer by orienting a liquid crystal material to exhibit refractive index anisotropy. A polymer can form a retardation layer by exhibiting refractive index anisotropy through stretching a polymer film obtained by casting, coating, or the like. In terms of thinness, 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 a polymerizable group.

[0073] The type of liquid crystal compound is not particularly limited. Generally, liquid crystal compounds can be classified into rod-shaped (rod-shaped liquid crystal compounds) and discotic (discotic liquid crystal compounds) based on their shape. Liquid crystal compounds can also be classified into low-molecular-weight and high-molecular-weight compounds. High-molecular-weight compounds generally refer to compounds with a degree of polymerization of 100 or more (see "Polymer Physics: Phase Transition Dynamics," by Masao Doi, p. 2, Iwanami Shoten, 1992). In the present invention, any liquid crystal compound can be used, but rod-shaped or discotic 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 discotic liquid crystal compounds, or a mixture of rod-shaped and discotic liquid crystal compounds may also be used.

[0074] Examples of rod-shaped liquid crystal compounds include those described in claim 1 of JP-A No. 11-513019 and paragraphs 0026 to 0098 of JP-A No. 2005-289980. Examples of discotic liquid crystal compounds include those described in paragraphs 0020 to 0067 of JP-A No. 2007-108732 and paragraphs 0013 to 0108 of JP-A No. 2010-244038.

[0075] The liquid crystal compound preferably has a polymerizable group. In other words, the liquid crystal compound is preferably a polymerizable liquid crystal compound. When the liquid crystal compound has a polymerizable group, the alignment state of the liquid crystal compound can be easily fixed by a curing treatment described later. The type of polymerizable group possessed by the liquid crystal compound is not particularly limited, and a functional group capable of an addition polymerization reaction is preferred, a polymerizable ethylenically unsaturated group or a ring-polymerizable group is more preferred, and a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group is even more preferred. The number of polymerizable groups possessed by the liquid crystal compound is not particularly limited, but is preferably 2 or more. The upper limit is not particularly limited, but is often 10 or less.

[0076] The liquid crystal compound forming the retardation layer preferably contains a liquid crystal compound represented by the following general formula (I).

[0077]

[0078] In the formula (1), D<linking bond> is independently a single bond, or —CO—, —O—, —S—, —C(═S)—, or —CR 1 R 2 -, -CR 3 =CR 4 -, -NR 5 -, or a divalent linking group formed by a combination of two or more thereof, R 1 ~R 5 each independently represents a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 12 carbon atoms.

[0079] A 1 and A 2 Each <rigid ring> independently represents an aromatic hydrocarbon ring which may have a substituent, an aromatic heterocycle which may have a substituent, or a divalent alicyclic hydrocarbon group which may have a substituent, provided that one or more -CH2- constituting the alicyclic hydrocarbon group may be substituted with -O-, -S-, or -NH-.

[0080] SP 1 and SP 2 Each <flexible chain> independently represents a single bond or a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms which may have a substituent, provided that one or more of the methylene groups which may have a substituent and which constitute the aliphatic hydrocarbon group may be substituted with -O-, -S-, -NH-, -N(Q)- or -CO-. Q represents a substituent.

[0081] L 1 and L 2 Each of the <terminal group> independently represents a monovalent organic group, 1 and L 2 At least one of the groups represents a polymerizable group, and n represents an integer of 0 or more.

[0082] Specific examples of thermotropic liquid crystals are given in paragraphs

[0129] to

[0249] of International Publication No. 2022 / 215757.

[0083] The liquid crystal compound may be a liquid crystal compound that exhibits either normal wavelength dispersion or reverse wavelength dispersion. When a retardation layer that exhibits the characteristics of a wideband λ / 4 plate as a single film is used, a liquid crystal compound that exhibits so-called reverse wavelength dispersion, in which the retardation increases with increasing wavelength, is preferred, and a liquid crystal compound that has two or more polymerizable groups and exhibits reverse wavelength dispersion is more preferred.

[0084] In the present invention, the λ / 4 plate preferably satisfies the following formula: 0.50<Re(450) / Re(550)<1.00

[0085] In addition, when the retardation layer is a layer formed using a liquid crystal composition containing a liquid crystal compound, the liquid crystal composition may contain a surfactant, a polymerization initiator, a crosslinking agent, and other additives in addition to the above-mentioned liquid crystal compound.

[0086] The surfactant is preferably a compound that can function as an alignment control agent that contributes to the stable or rapid alignment of the cholesteric liquid crystal phase. Examples of the surfactant include silicone surfactants and fluorine surfactants. It is also preferable to use a non-fluorine surfactant as the surfactant.

[0087] The non-fluorine-based surfactant preferably contains a siloxane unit or a long-chain alkyl group.

[0088] As described above, the retardation layer is preferably a layer formed using a liquid crystal compound having a polymerizable group, and more preferably a layer formed by fixing the orientation state of a liquid crystal compound having a polymerizable group. The orientation state that a liquid crystal compound having a polymerizable group can assume is not particularly limited, and examples thereof include homogeneous orientation, homeotropic orientation, twisted orientation, cholesteric orientation, hybrid orientation (orientation in which the tilt angle of the liquid crystal compound changes continuously from one surface to the other), and tilted orientation (orientation in which the tilt angle of the liquid crystal compound is constant from one surface to the other). Note that twisted orientation refers to an orientation state in which the liquid crystal compound is twisted around the thickness direction as the rotation axis, and when the liquid crystal compound is twisted and has a predetermined tilt angle (tilt angle greater than 0°), it corresponds to twist hybrid orientation. Note that, in this specification, twisted orientation refers to an embodiment in which the twist angle of the liquid crystal compound is less than 360°, and cholesteric orientation refers to an embodiment in which the twist angle of the liquid crystal compound is 360° or more.

[0089] The "fixed" state is a state in which the alignment of the liquid crystal compound is maintained, which is the most typical and preferred embodiment. However, it is not limited thereto, and specifically, it is more preferred that the layer has no fluidity and the alignment state is not changed by an external field or external force, and the fixed alignment state can be stably maintained, usually in a temperature range of 0 to 50°C, or under more severe conditions in a temperature range of −30 to 70°C.

[0090] The retardation layer formed using a liquid crystal compound may have a plurality of regions in the thickness direction where the liquid crystal compound has different alignment states. For example, the retardation layer may have a region in which the liquid crystal compound is fixed in a homogeneously aligned state and a region in which the liquid crystal compound is fixed in a twisted aligned state, along the thickness direction.

[0091] The thickness of the retardation layer is not particularly limited, but is preferably 0.1 to 10.0 μm, more preferably 0.5 to 5.0 μm.

[0092] The λ / 4 plate 24 may be composed of a single retardation layer, or may be composed of a laminate of two or more retardation layers, such as a combination of a λ / 4 retardation layer and a λ / 2 retardation layer. Furthermore, other retardation layers, such as a positive C plate and a negative C plate, may be added to compensate for the change in retardation due to obliquely incident light.

[0093] Here, the λ / 4 plate 24 preferably has an Nz factor greater than 0 and less than 1, more preferably 0.2 to 0.7, and even more preferably 0.3 to 0.6. The Nz factor is a value given by Nz = (nx - nz) / (nx - ny), where nx is the refractive index in the in-plane slow axis direction, ny is the refractive index in the direction perpendicular to the in-plane slow axis, and nz is the refractive index in the thickness direction. The refractive index nx in the in-plane slow axis direction, ny is the refractive index in the direction perpendicular to the in-plane slow axis, and nz is the refractive index in the thickness direction, and can be measured using an AxoScan or an Abbe refractometer, for example.

[0094] By setting the Nz factor of the λ / 4 plate 24 to be greater than 0 and less than 1, it is possible to compensate for the change in phase difference for light incident from an oblique direction. That is, as shown in FIG. 2 , infrared light diverged by the lens 14 and incident on the circular polarizer 16a (λ / 4 plate 24) is incident from a direction approximately perpendicular to the circular polarizer 16a near the center (the position where the optical axis of the lens 14 passes). Therefore, the λ / 4 plate 24 acts to impart an appropriate λ / 4 phase difference to the incident infrared light. In contrast, at positions away from the center, the infrared light is incident on the circular polarizer 16a from an oblique direction (the angle (polar angle) relative to the perpendicular to the surface of the circular polarizer 16a is greater than 0°). Therefore, if the Nz factor is 0, the phase difference imparted to the incident infrared light deviates from λ / 4, and the converted infrared light may become elliptically polarized. Therefore, by setting the Nz factor to be greater than 0 and less than 1, the phase difference given to infrared light incident from an oblique direction can be set to λ / 4, and the incident infrared light can be appropriately converted into circularly polarized light.

[0095] The λ / 4 plate preferably has a tensile modulus of 1 MPa to 10 GPa, more preferably 100 MPa to 6 GPa, and even more preferably 500 MPa to 4 GPa. As shown in Fig. 3 above, the circular polarizer preferably has a curved structure. In order to make it possible to easily curve the circular polarizer, it is preferable that the tensile modulus of the λ / 4 plate be within the above range.

[0096] The tensile modulus (Young's modulus) can be measured by a known method, for example, as described in JIS K 7161-1:2014. Unless otherwise specified, the tensile modulus is the modulus at room temperature (20°C). The tensile modulus (Young's modulus) can be measured, for example, using a tensile testing machine "AG-IS" manufactured by Shimadzu Corporation.

[0097] [Cholesteric Liquid Crystal Layer] The circular polarizer 16 may have a cholesteric liquid crystal layer. As is well known, a cholesteric liquid crystal layer has a helical structure in which liquid crystal compounds are stacked in a helical spiral, and the helical spiral structure is defined as one pitch in which liquid crystal compounds are stacked in a helical spiral through one rotation (360° rotation).

[0098] The cholesteric liquid crystal layer has wavelength-selective reflectivity. The selective reflection wavelength range of the cholesteric liquid crystal layer follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. Therefore, the selective reflection central wavelength can be adjusted by adjusting the pitch P. The longer the pitch P, the longer the selective reflection central wavelength of the cholesteric liquid crystal layer. Therefore, the length of the helical pitch of the cholesteric liquid crystal layer used as a circular polarizer can be designed so that the selective reflection wavelength includes the wavelength of the infrared light emitted by the infrared light source 12.

[0099] The helical pitch of a cholesteric liquid crystal layer depends on the type of chiral agent used together with the liquid crystal compound when forming the cholesteric liquid crystal layer and the concentration of the chiral agent added. Therefore, the desired helical pitch can be obtained by adjusting these factors. Details on pitch adjustment are provided in Fujifilm Research Report No. 50 (2005), pp. 60-63. Methods for measuring the helical sense and pitch can be found in "Introduction to Liquid Crystal Chemistry Experiments," edited by the Japanese Liquid Crystal Society, published by Sigma Publishing in 2007, p. 46, and "Liquid Crystal Handbook," published by the Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196.

[0100] Furthermore, cholesteric liquid crystal layers exhibit selective reflection for either left- or right-handed circularly polarized light at a specific wavelength. Whether the reflected light is right-handed or left-handed circularly polarized light depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. When the helix of the cholesteric liquid crystal layer is twisted to the right, right-handed circularly polarized light is reflected, and when the helix is ​​twisted to the left, left-handed circularly polarized light is reflected. The twist direction of the helix of the cholesteric liquid crystal layer can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and / or the type of chiral agent added.

[0101] Furthermore, the half-value width Δλ (nm) of the selective reflection wavelength range (circularly polarized light reflection wavelength range) in which the cholesteric liquid crystal layer exhibits selective reflection depends on the Δn of the cholesteric liquid crystal layer and the helical pitch P, and follows the relationship Δλ = Δn × P. Therefore, the width of the selective reflection wavelength range (selective reflection wavelength range) can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compounds forming the cholesteric liquid crystal layer, as well as the temperature at which the orientation is fixed. The half-value width of the reflection wavelength range may be, for example, 10 to 500 nm, preferably 20 to 300 nm, and more preferably 30 to 100 nm.

[0102] In addition, when the circular polarizer includes a cholesteric liquid crystal layer, the circular polarizer may have a support, an alignment film, and the like.

[0103] <First image sensor> The first image sensor 18 receives infrared light of each polarization state that is reflected by the object to be inspected P and separated into light of multiple polarization states by the polarization separation filter 20, converts the received infrared light into an electrical signal, and outputs the electrical signal.

[0104] As the first image sensor 18, a conventionally known imaging element such as a charge-coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor can be appropriately used.

[0105] The electrical signal output from the first image sensor 18 is subjected to predetermined processing in a polarization image processing unit (not shown) to calculate the polarization state of the reflected light. The generated data is converted into an image and displayed on a display unit (not shown), or superimposed on a visible image (described later), or stored in a known storage medium, as necessary.

[0106] Furthermore, an optical system may be provided between the first image sensor 18 and the inspection object P to form an image of the reflected light from the inspection object P on the light receiving surface of the first image sensor 18 .

[0107] <Polarization separation filter> The polarization separation filter 20 separates the infrared light (reflected light) reflected by the inspection object P into light of a plurality of polarization states. The polarization separation filter 20 may separate the reflected light into a plurality of linearly polarized light beams, or may separate the reflected light into right-handed circularly polarized light beams and left-handed circularly polarized light beams.

[0108] An example of a light receiving system included in the polarization image measurement device of the present invention is conceptually shown in Figure 4. The light receiving system shown in Figure 4 includes a first image sensor 18 and a polarization separation filter 20a disposed adjacent to the light receiving surface of the first image sensor 18.

[0109] FIG. 5 is a top view conceptually illustrating the polarization separation filter 20a included in the light receiving system shown in FIG. 4. The polarization separation filter 20a is a linear polarizer, a patterned polarizer having a pattern of multiple regions with different transmission axis directions. In FIG. 5, the directions of the transmission axes are indicated by arrows. In the example shown in FIG. 5, the following are regularly arranged: a region 21a having a transmission axis in the vertical direction in the figure; a region 21b having a transmission axis in a direction perpendicular to the vertical direction (horizontal direction in the figure); a region 21c having a transmission axis in a direction at 45° clockwise to the transmission axis of region 21a (from the upper right to the lower left in the figure); and a region 21d having a transmission axis in a direction at 45° counterclockwise to the transmission axis of region 21a (from the upper left to the lower right in the figure).

[0110] Each of the regions 21a to 21d corresponds to one or several pixels of the first image sensor 18. Reflected light passing through the region 21a is converted into linearly polarized light in a direction corresponding to the direction of the transmission axis of the region 21a and enters a certain pixel of the first image sensor 18. Similarly, reflected light passing through the region 21b is converted into linearly polarized light in a direction corresponding to the direction of the transmission axis of the region 21b and enters another pixel of the first image sensor 18. Reflected light passing through the region 21c is converted into linearly polarized light in a direction corresponding to the direction of the transmission axis of the region 21c and enters yet another pixel of the first image sensor 18. Reflected light passing through the region 21d is converted into linearly polarized light in a direction corresponding to the direction of the transmission axis of the region 21d and enters yet another pixel of the first image sensor 18. That is, each pixel of the first image sensor 18 receives linearly polarized light corresponding to the transmission axis of the corresponding region of the patterned polarizer 20a (polarization separation filter).

[0111] As shown by the thick dashed line in Figure 5, adjacent regions 21a to 21d are considered as one group, and the polarization state of the reflected light at the position on the object P to be inspected corresponding to this group can be determined from the amount of linearly polarized light detected by each of the groups of regions 21a to 21d.

[0112] A patterned wire-grid polarizer can be suitably used as such a patterned polarizer 20a. A wire-grid polarizer transmits one polarized light and reflects the other polarized light by utilizing the birefringence of thin metal wires. A wire-grid polarizer has metal wires arranged periodically and is primarily used as a polarizer in the terahertz wave band. In order for a wire grid to function as a polarizer, the wire spacing must be sufficiently smaller than the wavelength of the incident electromagnetic wave.

[0113] In a wire grid polarizer, metal wires are arranged at equal intervals. Polarized light components polarized parallel to the longitudinal direction of the metal wires are reflected by the wire grid polarizer, while polarized light components polarized perpendicular to the longitudinal direction of the metal wires are transmitted through the wire grid polarizer.

[0114] As a patterned wire grid polarizer arranged on an image sensor, Sony Corporation's IMX250MZR / MYR, IMX264MZR / MYR, IMX253MZR / MYR, etc. can be used.

[0115] FIG. 6 conceptually illustrates another example of a light receiving system included in the polarization image measurement device of the present invention. The light receiving system shown in FIG. 6 includes a first image sensor 18a, a first image sensor 18b, and a polarization separation filter 20c. In the example shown in FIG. 6, the polarization separation filter 20c is a liquid crystal diffraction film that selectively diffracts right-handed circularly polarized light and left-handed circularly polarized light. The first image sensor 18a and the first image sensor 18b correspond to the first image sensor of the present invention. As with the first image sensor 18 described above, conventionally known imaging elements such as CCD image sensors and CMOS image sensors can be used as appropriate for the first image sensor 18a and the first image sensor 18b.

[0116] The liquid crystal diffraction film 20c is a reflective liquid crystal diffraction element (reflective liquid crystal diffraction film) that reflects and diffracts circularly polarized light in one rotation direction and transmits circularly polarized light in the other rotation direction. In the example shown in Figure 6, the liquid crystal diffraction film 20c transmits right-handed circularly polarized light and reflects and diffracts left-handed circularly polarized light.

[0117] The 1-1 image sensor 18a is disposed at the position where the right-handed circularly polarized light passes through the liquid crystal diffraction film 20c. That is, the 1-1 image sensor 18a receives the right-handed circularly polarized component of the light reflected from the inspection object P. On the other hand, the 1-2 image sensor 18b is disposed at the position where the left-handed circularly polarized light is reflected and diffracted by the liquid crystal diffraction film 20c. That is, the 1-2 image sensor 18b receives the left-handed circularly polarized component of the light reflected from the inspection object P.

[0118] Light reflected from a position on the object under inspection P is incident on a position on the liquid crystal diffraction film 20c, where, for example, the right-handed circularly polarized light component is transmitted and the left-handed circularly polarized light component is reflected. A pixel on the first-first image sensor 18a receives the right-handed circularly polarized light that has transmitted through the liquid crystal diffraction film 20c and detects the amount of right-handed circularly polarized light. A pixel on the first-second image sensor 18b receives the left-handed circularly polarized light that has been reflected and diffracted by the liquid crystal diffraction film 20c and detects the amount of left-handed circularly polarized light. A polarization image processing unit (not shown) can calculate the degree of circular polarization of the reflected light at a position on the object under inspection P from the amount of right-handed circularly polarized light detected by a pixel on the first-first image sensor 18a and the amount of left-handed circularly polarized light detected by the corresponding pixel on the first-second image sensor 18b.

[0119] An example of such a liquid crystal diffraction film 20c is a reflective liquid crystal diffraction element that has a cholesteric liquid crystal layer, which has a liquid crystal orientation pattern in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

[0120] The cholesteric liquid crystal layer of a reflective liquid crystal diffraction element selectively reflects light of a specific wavelength, and reflects light in a direction different from regular reflection (specular reflection). In this application, reflecting light in a direction different from regular reflection is referred to as diffracting (bending) the reflected light.

[0121] The reflective liquid crystal diffraction element may have a support, an alignment film, and the like.

[0122] Such reflective liquid crystal diffraction elements (cholesteric liquid crystal layers having liquid crystal orientation patterns) are described in WO 2019 / 131950, WO 2019 / 131966, WO 2019 / 189852, WO 2020 / 071169, etc.

[0123] The cholesteric liquid crystal layer serving as the liquid crystal diffraction film 20c selectively diffracts light with wavelengths in the infrared light range, and the length of the helical pitch can be designed so that the selective reflection wavelengths include the wavelength of the infrared light emitted by the infrared light source 12.

[0124] In addition, in the illustrated example, the liquid crystal diffraction film 20c transmits right-handed circularly polarized light and reflects and diffracts left-handed circularly polarized light, but this is not limited to this and the film may transmit left-handed circularly polarized light and reflect and diffract right-handed circularly polarized light.

[0125] FIG. 7 conceptually illustrates another example of a light receiving system included in the polarization image measurement device of the present invention. The light receiving system shown in FIG. 7 includes a first image sensor 18a, a second image sensor 18b, and a polarization separation filter 20d. In the example shown in FIG. 7, the polarization separation filter 20d is a liquid crystal diffraction film that selectively diffracts right-handed circularly polarized light and left-handed circularly polarized light. The first image sensor 18a and the second image sensor 18b are similar to the first image sensor 18a and the second image sensor 18b shown in FIG. 6.

[0126] The liquid crystal diffraction film 20d is a transmissive liquid crystal diffraction element that transmits and diffracts circularly polarized light having one rotation direction and circularly polarized light having the other rotation direction in different directions. In the example shown in Figure 7, the liquid crystal diffraction film 20d transmits and diffracts right-handed circularly polarized light incident from above in the figure in a direction toward the bottom right, and transmits and diffracts left-handed circularly polarized light in a direction toward the bottom left. Note that the circularly polarized light that passes through the liquid crystal diffraction film 20d is converted into circularly polarized light having the opposite rotation direction.

[0127] The 1-1 image sensor 18a is disposed at the position where the right-handed circularly polarized light is transmitted through and diffracted by the liquid crystal diffraction film 20d. That is, the 1-1 image sensor 18a receives the right-handed circularly polarized component of the light reflected from the inspection object P. On the other hand, the 1-2 image sensor 18b is disposed at the position where the left-handed circularly polarized light is transmitted through and diffracted by the liquid crystal diffraction film 20c. That is, the 1-2 image sensor 18b receives the left-handed circularly polarized component of the light reflected from the inspection object P. As described above, the liquid crystal diffraction film 20d converts the circularly polarized light that passes through it into circularly polarized light of the opposite rotation direction, so that the circularly polarized light that enters the 1-1 image sensor 18a is left-handed circularly polarized light, and the circularly polarized light that enters the 1-2 image sensor 18b is right-handed circularly polarized light.

[0128] Reflected light from a position on the inspection object P is incident on a position on the liquid crystal diffraction film 20d. For example, the right-handed circularly polarized light component is diffracted in one direction and transmitted, while the left-handed circularly polarized light component is diffracted in a different direction and transmitted. A pixel on the first-first image sensor 18a receives the left-handed circularly polarized light that has passed through the liquid crystal diffraction film 20d and detects the amount of the right-handed circularly polarized light component of the reflected light. A pixel on the first-second image sensor 18b receives the right-handed circularly polarized light that has passed through the liquid crystal diffraction film 20d and detects the amount of the left-handed circularly polarized light component of the reflected light. A polarization image processing unit (not shown) can calculate the degree of circular polarization of the reflected light at a position on the inspection object P from the amount of the right-handed circularly polarized light component detected by a pixel on the first-first image sensor 18a and the amount of the left-handed circularly polarized light component detected by the corresponding pixel on the first-second image sensor 18b.

[0129] Such a transmissive liquid crystal diffraction element has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound is continuously rotated along at least one direction in the plane, and is a liquid crystal diffraction element having an optically anisotropic layer in which the liquid crystal compound does not form a cholesteric liquid crystal phase in the thickness direction. Note that the optically anisotropic layer may have a configuration in which the liquid crystal compound is twisted and rotated in the thickness direction to such an extent that it does not form a cholesteric liquid crystal phase. Such a transmissive liquid crystal diffraction element is described in WO 2020 / 226078, WO 2020 / 122128, etc.

[0130] The transmissive liquid crystal diffraction element may have a support, an alignment film, and the like.

[0131] The polarization image measurement device of the present invention may further include a second light source that emits light of a wavelength different from that of the infrared light source, and may further include a white light source that has multiple luminance peaks.

[0132] FIG. 8 is a diagram conceptually showing another example of the light irradiation system of the polarization image measurement device of the present invention.

[0133] 8 includes an infrared light source 12, a white light source 32, a second light source 34, a light guide 30, a lens 14, and a circular polarizer 16. The infrared light source 12, the lens 14, and the circular polarizer 16 are as described above, and therefore will not be described again.

[0134] The white light source 32 emits visible light (white light) for capturing a visible image, and emits light having multiple luminance peaks. For example, the white light source 32 may have luminance peaks in each of the blue light region, the green light region, and the red light region, or may have luminance peaks in the blue light region and the yellow light region. Furthermore, the white light source 32 may have a luminance peak in the ultraviolet light region.

[0135] Furthermore, the white light source 32 may be a single light source that emits light of each brightness peak, or may be made up of multiple light sources including a light source that emits light of wavelengths that include two or more of the light of each brightness peak, or may be configured to have multiple semiconductor light sources that respectively emit light of each brightness peak. When the white light source 32 has multiple light sources, it is sufficient that it has a multiplexing member that multiplexes the light emitted by the multiple light sources.

[0136] Any conventionally known white light source can be used as the white light source 32. For example, when the polarization image measurement device of the present invention is used in an endoscope system, the light source device described in Japanese Patent Application Laid-Open No. 2023-109319 can be used as the white light source.

[0137] The second light source 34 is a light source for emitting light for acquiring a polarization image using light of a wavelength different from that of the infrared light emitted by the infrared light source 12. As shown by I2 in Fig. 9, the light emitted by the second light source 34 may be infrared light of a wavelength different from that of the infrared light emitted by the infrared light source 12 (shown by I1 in Fig. 9). Alternatively, as shown by I3 in Fig. 10, the light emitted by the second light source 34 may be infrared light of a wavelength different from that of the infrared light emitted by the white light source 32 (shown by I1 in Fig. 10). v When the light emitted by the second light source 34 has a wavelength between the peaks of the luminance emitted by the white light source 32, it is preferable that the luminance of the white light source 32 at the wavelength of the light emitted by the second light source 34 is 20% or less of the luminance of the lowest peak of the luminance peaks of the white light source 32.

[0138] As the second light source 34, a light source similar to the above-described infrared light source 12 can be used as long as it emits light of the above wavelength.

[0139] 8, the light emitted from the infrared light source 12, the white light source 32, and the second light source 34 is each incident on the light guide 30. There are no particular limitations on the configuration for making the light from multiple light sources incident on one light guide 30, and any conventionally known configuration can be used as appropriate. For example, a configuration using an optical member such as a dichroic filter, as described in JP 2023-109319 A, can be used.

[0140] The light emitted by the infrared light source 12, the white light source 32, and the second light source 34 is guided through the light guide 30 and emitted from the tip (the end on the lens 14 side) of the light guide 30. The light emitted from the light guide 30 is diverged by the lens 14, passes through the circular polarizer 16, and is irradiated onto the inspection object P.

[0141] In this case, it is preferable that the lens 14 has the function of diverging light for all of the infrared light emitted by the infrared light source 12, the white light emitted by the white light source 32, and the light of the wavelength emitted by the second light source 34.

[0142] Furthermore, the circular polarizer 16 preferably converts the infrared light emitted by the infrared light source 12 and the light emitted by the second light source 34 into circularly polarized light. This allows the polarization state of the reflected light to be acquired using the light emitted by the second light source 34, and then, for example, normal and abnormal areas can be identified based on the degree of circular polarization of the detected reflected light. Furthermore, analyzing the polarization state of the reflected light from the test object P at multiple wavelengths facilitates quantitative analysis of the curved surface and depth direction. Specifically, performing depth quantitative analysis at a single wavelength requires separately acquiring the angle φ between the test object and the detector (because the degree of circular polarization is angle φ dependent). However, detecting at two wavelengths and calculating the difference can cancel out the angle dependency, eliminating the need to acquire the angle φ. When measuring at a single wavelength, acquiring the angle φ requires separate ranging or estimation by image analysis. However, performing detection at two wavelengths eliminates this need, making analysis easier.

[0143] On the other hand, it is preferable that the circular polarizer 16 transmits the white light emitted by the white light source 32 without converting the light into circularly polarized light, thereby preventing a decrease in the amount of light when a visible image is obtained using the white light.

[0144] The light of the wavelength emitted by the second light source 34 is converted into circularly polarized light and irradiated onto the inspection object P, and is reflected by the inspection object P. The light reflected from the inspection object P is separated by the polarization separation filter 20 into light of a plurality of polarization states, and the separated light of each polarization state is received by the first image sensor 18. In other words, it is preferable that the polarization separation filter 20 also functions as the polarization separation filter 20 for the light of the wavelength emitted by the second light source 34.

[0145] When the polarization separation filter 20 is a patterned polarizer, the patterned polarizer may act as a linear polarizer for the light of the wavelength emitted by the second light source 34 .

[0146] Furthermore, when the polarization separation filter 20 is a reflective liquid crystal diffraction element, the reflective liquid crystal diffraction element may reflect circularly polarized light in one rotation direction and transmit circularly polarized light in the other rotation direction for light of the wavelength emitted by the second light source 34. For example, the reflective liquid crystal diffraction element may be configured by stacking a cholesteric liquid crystal layer that reflects circularly polarized light in one rotation direction and transmits circularly polarized light in the other rotation direction for infrared light emitted by the infrared light source 12, and a cholesteric liquid crystal layer that reflects circularly polarized light in one rotation direction and transmits circularly polarized light in the other rotation direction for light of the wavelength emitted by the second light source 34. Alternatively, one cholesteric liquid crystal layer may reflect circularly polarized light in one rotation direction and transmit circularly polarized light in the other rotation direction for infrared light emitted by the infrared light source 12 and light of the wavelength emitted by the second light source 34.

[0147] Furthermore, when the polarization separation filter 20 is a transmissive liquid crystal diffraction element, the transmissive liquid crystal diffraction element may transmit and diffract circularly polarized light in one rotation direction and circularly polarized light in the other rotation direction in different directions for light of the wavelength emitted by the second light source 34. In this case, too, a configuration may be used in which an optically anisotropic layer that acts on the infrared light emitted by the infrared light source 12 and an optically anisotropic layer that acts on the light of the wavelength emitted by the second light source 34 are laminated. Alternatively, one optically anisotropic layer may have the effect of transmitting and transmitting circularly polarized light in one rotation direction and circularly polarized light in the other rotation direction in different directions for the infrared light emitted by the infrared light source 12 and the light of the wavelength emitted by the second light source 34.

[0148] In addition, in the case of a configuration in which a visible image is captured using white light emitted by the white light source 32, it is preferable to configure the device to have a second image sensor (not shown) that captures the reflected light of the light emitted from the white light source 32 reflected by the object P to be inspected.

[0149] As the second image sensor, a conventionally known image sensor capable of capturing visible images, which is a combination of an imaging element such as a CCD image sensor or a CMOS image sensor and a color filter, can be appropriately used.

[0150] Furthermore, in the case of a configuration in which white light is emitted from the white light source 32 and the reflected light from the object under inspection P is received by the second image sensor to capture a visible image, it is preferable to superimpose on the obtained visible image the information obtained by the first image sensor, i.e., information on the polarization state (degree of circular polarization) of the scattered light for each position on the object under inspection P, or information on identifying normal and abnormal areas obtained based on the degree of circular polarization of the reflected light, and display the information on a display unit not shown.

[0151] There are no particular limitations on the method for superimposing and displaying the information obtained by the first image sensor on the visible image, and examples include a method of applying a color with a different intensity depending on the degree of circular polarization, a method of assigning a numerical value of the degree of circular polarization to the corresponding area, and a method of displaying an area identified as an abnormal area by surrounding it with a line.

[0152] Furthermore, in the case of a configuration including the white light source 32, the first image sensor 18 preferably has a filter that blocks light in the visible light range and transmits infrared light. This prevents the light emitted by the white light source 32 from being reflected by the inspection target P from entering the first image sensor 18, thereby preventing a decrease in the accuracy of detecting the polarization state of the reflected infrared light.

[0153] In the above example, the configuration includes a second image sensor for capturing a visible image when the white light source 32 is used, but the present invention is not limited to this. The first image sensor 18 may be sensitive to both the visible light region and the infrared light region and detect both infrared light and visible light. In this case, the first image sensor 18 may be configured to have color filters in which regions that transmit RGB and infrared light (IR) are formed in a pattern corresponding to the pixels.

[0154] The first image sensor 18 is sensitive to both the visible light region and the infrared light region, and is configured to detect both infrared light and visible light. This allows for coaxial capture of a visible image and detection of the circularly polarized infrared light. Furthermore, capture of a visible image and detection of infrared light can be performed simultaneously. This allows for highly accurate alignment of a position on the captured visible image with a position where the polarization state of reflected infrared light is detected.

[0155] 8, the configuration includes the infrared light source 12, the white light source 32, and the second light source 34, but the configuration is not limited to this, and the polarization image measurement device of the present invention may be configured to include only the infrared light source 12 and the white light source 32, or may be configured to include only the infrared light source 12 and the second light source 34. Alternatively, the configuration may include a plurality of second light sources with different wavelengths, or may include an ultraviolet light source.

[0156] Furthermore, in the case of a configuration having a plurality of light sources, the light source that emits light may be switched to emit light sequentially (alternately) from each light source, or the light may be emitted simultaneously from each light source. For example, in the case of a configuration having the infrared light source 12 and the second light source 34, it is desirable to switch between the infrared light source 12 and the second light source 34 to emit light sequentially (alternately). On the other hand, in the case of a configuration having the infrared light source 12 and the white light source 32, the infrared light source 12 and the white light source 32 may be configured to emit light simultaneously or to emit light sequentially (alternately).

[0157] 8, the light from each light source is guided by the light guide 30 and then emitted, but this is not limiting, and a configuration without a light guide may be used in which the light from the light source is directly incident on the lens 14. In a configuration with multiple light sources without a light guide, it is sufficient that a lens and a circular polarizer are provided corresponding to each light source. That is, the configuration may be such that the lens 14 and the circular polarizer 16 are provided near the exit of the infrared light source 12, a second lens and a second circular polarizer that diverge light are provided near the exit of the second light source 34, and a third lens that diverges light is provided near the exit of the white light source 32.

[0158] Furthermore, in the polarization image measurement device of the present invention, it is preferable to detect the polarization state of light reflected by the inspection object P under two or more conditions where the angle formed between the infrared light source 12, the inspection object P, and the first image sensor (hereinafter also referred to as the polarization imaging angle) is different. The angle formed between the infrared light source 12, the inspection object P, and the first image sensor is the angle formed between the optical axis of the infrared light source 12 (a line parallel to the optical axis) and a line connecting the point where the optical axis of the infrared light source 12 intersects with the surface of the inspection object P and the center point of the imaging surface of the first image sensor.

[0159] Quantitative analysis on curved surfaces and in the depth direction can be easily performed by detecting the polarization state of reflected light under two or more conditions with different polarization imaging angles.

[0160] Examples of methods for detecting the polarization state of reflected light under two or more conditions with different polarization imaging angles include a method in which the infrared light source 12 and / or the first image sensor 18 are movable and the polarization state of reflected light is detected in each of a plurality of arrangements where the relative positions of the infrared light source 12 and the first image sensor 18 are different, and a method in which a configuration has a plurality of infrared light sources 12 and / or a plurality of first image sensors 18 and the polarization state of reflected light is detected in each of a plurality of combinations where the relative positions of the infrared light source 12 and the first image sensor 18 are different.

[0161] The polarization image measurement device of the present invention is applicable to devices used in various fields, such as endoscope systems, semiconductor inspection devices, and biometric authentication systems, which irradiate polarized light onto an object to be inspected, detect the reflected light, and inspect the internal condition of the object from the polarization state of the reflected light.

[0162] As an example, a case where the polarization image measurement device of the present invention is used in an endoscope system will be described.

[0163] An example of an endoscope system is conceptually shown in Fig. 11. The endoscope system 70 shown in Fig. 11 is basically a conventionally known endoscope system, except that it includes the polarization image measurement device of the present invention inside.

[0164] An endoscopic system including the polarization image measurement device of the present invention can be constructed by adding an infrared light source 12 to the light source device of a conventionally known endoscopic system, adding a circular polarizer 16 near the light exit port at the tip of the endoscope, and adding a first image sensor 18 and a polarization separation filter 20 at the tip of the endoscope.

[0165] An endoscope system 70 shown in FIG. 11 includes an endoscope 71 , a light source device 76 , a processor device 72 , a display 73 , an operation input unit 74 , and a universal cord 75 .

[0166] The endoscope 71 captures images of an object to be observed inside a living body. The light source device 76 has a white light source 32 and an infrared light source 12, and supplies the endoscope 71 with illumination light (white light) and infrared light for illuminating the object to be observed. The processor device 72 functions as a central control unit that controls the image capture and illumination light, etc., and also processes image signals obtained by the image capture to generate a display image. The processor device 72 also processes data obtained when the infrared light source 12 emits light and the first image sensor 18 receives light reflected from the object to be examined P, and calculates the polarization state (degree of circular polarization). The processor device 72 is electrically connected to a display 73 and an operation input unit 74. The display 73 displays images captured by the endoscope 71 or image information associated with the images. The display 73 may also display information about the polarization state (degree of circular polarization) of the light reflected from the object to be examined P. The operation input unit 74 functions as a user interface that accepts input operations such as function settings. The universal cord 75 is a cord through which the communication cable extending from the insertion portion 71a, the light guide 30, etc. are inserted, and connects the endoscope 71 with the processor device 72 and the light source device 76. Therefore, the endoscope 71 has the light guide 30 that guides the illumination light and infrared light. Note that an external recording unit (not shown) may be connected to the processor device 72 to record images and / or image information, as well as information on the polarization state (degree of circular polarization) of the light reflected from the inspection object P, etc.

[0167] The endoscope 71 is optically connected to the light source device 76 and electrically connected to the processor device 72. The endoscope 71 has an insertion section 71a to be inserted into the subject, an operation section 71b provided at the base end of the insertion section 71a, and a bending section 71c and a tip section 71d provided at the tip end of the insertion section 71a. The bending section 71c is bent by operating an angle knob 71e of the operation section 71b. This bending operation allows the tip section 71d to be directed in a desired direction. In addition to the angle knob 71e, the operation section 71b is also provided with a zoom operation section 71f and the like.

[0168] The light source device 76 is a device that supplies illumination light to the object to be inspected P and infrared light to the light guide 30 of the endoscope 71, and is equipped with a white light source 32, an infrared light source 12, a light source control unit that controls each light source, and a combining unit that combines the optical paths of the light emitted by each light source.

[0169] A connector is attached to one end of the processor device 72 and the light source device 76. The connector is a composite type connector consisting of a communication connector and a light source connector. The communication connector and the light source connector are detachably connected to the processor device 72 and the light source device 76, respectively. One end of a communication cable is disposed in the communication connector, and the entrance end of a light guide is disposed in the light source connector.

[0170] The endoscope 71 includes a light guide 30, a second image sensor, etc. The endoscope 71 also has a forceps channel.

[0171] An illumination lens is disposed at the endoscope tip 71d, and light supplied from the light source device 76 is guided to the illumination lens by the light guide 30 and is then irradiated through the illumination window towards the inspection object P. In other words, the illumination lens corresponds to the lens 14 in the present invention. In addition, a circular polarizer 16 is disposed between the illumination lens and the illumination window.

[0172] An objective optical system and a second image sensor are disposed at the distal end 71d of the endoscope. An image of the inspection object P (reflected white light) is incident on the objective optical system and is formed on the imaging surface of the second image sensor by the objective optical system.

[0173] In addition, it is preferable that a unit having a first image sensor 18 and a polarization separation filter 20 is inserted into the forceps channel up to the endoscope tip 71 d, and the first image sensor 18 and the polarization separation filter 20 are disposed at the forceps port of the endoscope tip 71 d. A communication cable is connected to the first image sensor 18, which is then connected to the processor device 72. Infrared light reflected from the inspection object P is incident on the polarization separation filter 20 and separated into different polarized light beams which then enter the first image sensor 18.

[0174] The processor device 72 includes conventionally known components such as a central control unit, a DSP (Digital Signal Processor), an image processing unit, a frame memory, and a display control circuit. The processor device 72 stores programs related to image sensor or light source control, image processing, data processing, and other processes in a program memory (not shown). The processor device 72 realizes various functions, such as the DSP, central control unit, image processing unit, frame memory, and display control circuit, by a central control unit comprised of a processor, etc., running programs stored in the program memory. The central control unit also receives information from the endoscope 71 and the light source device 76, and controls the various components of the processor device 72, as well as the endoscope 71 or the light source device 76, based on the received information. The central control unit also receives information, such as instructions, from the operation input unit 74.

[0175] The processor device 72 also calculates the polarization state (degree of circular polarization) of the reflected light from data obtained by the first image sensor 18 receiving the light emitted by the infrared light source 12 and reflected by the inspection object P. Furthermore, the processor device 72 may distinguish between normal and abnormal areas from the obtained degree of circular polarization. The processor device 72 may also generate an image in which the polarization state (degree of circular polarization) of the obtained reflected light or the result of distinguishing between normal and abnormal areas is superimposed on a visible image of the inspection object P.

[0176] The image (data) obtained through processing by the processor device 72 may be stored in a recording unit or output to a display 73 .

[0177] In the above description, the unit consisting of the first image sensor 18 and the polarization separation filter 20 is configured to be inserted into the forceps channel of the endoscope 71 and placed in the forceps port of the endoscope tip 71d, but this is not limited to this, and the first image sensor 18 and the polarization separation filter 20 may be configured to be pre-installed in the endoscope tip 71d.

[0178] The above describes the polarization image measurement device of the present invention, but the present invention is not limited to this, and various improvements and modifications may be made without departing from the spirit of the present invention.

[0179] Furthermore, while the polarization image measurement device described above has a configuration including a lens that diverges infrared light emitted from the infrared light source, the configuration is not limited to this and may not include a lens that diverges infrared light. That is, the polarization image measurement device may have a configuration including an infrared light source that emits infrared light toward an inspection object, a circular polarizer having a thickness of 1 mm or less that converts the infrared light emitted from the infrared light source into circularly polarized light, a first image sensor that receives light that is reflected by the inspection object and the circularly polarized light converted by the circular polarizer, and a polarization separation filter that is arranged on an optical path between the inspection object and the first image sensor and separates the reflected light into light of a plurality of polarization states.

[0180] The present invention will be described in more detail below with reference to specific examples of the present invention.

[0181] Example 1 <Preparation of Circular Polarizer> <<Preparation of Linear Polarizer>> Composition 1 having the following composition was prepared: Composition 1 was a composition exhibiting lyotropic liquid crystal properties.

[0182] ────────────────────────────────── Composition 1 ────────────────────────────────── Dichroic dye III-2 5 parts by mass Water 95 parts by mass ────────────────────────────────

[0183] Dichroic dye III-2

[0184]

[0185] The above-prepared composition 1 (5 g) and zirconia beads (20 g) having an average particle size of 2 mm were packed into a 45 mL zirconia container, and milled for 50 minutes at a rotation speed of 300 rpm using a FRISCH planetary ball mill P-7 Classic Line.

[0186] The milled composition 1 was applied to a glass substrate using a wire bar (movement speed: 100 cm / s) and then air-dried. The resulting composition layer was then immersed in a 1 mol / L aqueous calcium chloride solution for 5 seconds, washed with ion-exchanged water, and air-dried to fix the orientation, thereby producing a 200 nm-thick light absorption anisotropic film 1 (linear polarizer).

[0187] The produced light absorption anisotropic film 1 acts as an absorptive linear polarizer for light with a wavelength of 940 nm.

[0188] <<Preparation of λ / 4 Plate>> [Preparation of Optically Anisotropic Layer] Composition H1 for forming an optically anisotropic layer was prepared according to the following formulation, heated and dissolved at 50° C. for 3 hours while stirring, and filtered through a 0.45 μm filter.

[0189] ─────────────────────────────────── Optically anisotropic layer forming composition H1 ───────────────────────────────── Liquid crystal compound H1 below: 75.5 parts by mass Polymerization initiator IRGACURE819 (manufactured by BASF) 0.8 parts by mass Surfactant F-1 above: 0.6 parts by mass Cyclopentanone 274.5 parts by mass ───────────────────────────────

[0190] Liquid crystal compound H1 (a mixture of the following three compounds. The mixing ratio (mass ratio) is shown in the upper left of the compound.)

[0191] (Preparation of Transparent Support) -Preparation of Core Layer Cellulose Acylate Dope- The following composition was charged into a mixing tank and stirred to dissolve each component, thereby preparing a cellulose acetate solution to be used as a core layer cellulose acylate dope.

[0192] ─────────────────────────────────── Core Layer Cellulose Acylate Dope ───────────────────────────────── Cellulose acetate having an acetyl substitution degree of 2.88: 100 parts by mass Polyester compound B described in the examples of JP-A No. 2015-227955: 12 parts by mass Compound F below: 2 parts by mass Methylene chloride (first solvent): 430 parts by mass Methanol (second solvent): 64 parts by mass ───────────────────────────────

[0193] Compound F

[0194] -Preparation of Outer Layer Cellulose Acylate Dope- 10 parts by mass of the following matting agent solution was added to 90 parts by mass of the above core layer cellulose acylate dope to prepare a cellulose acetate solution to be used as the outer layer cellulose acylate dope.

[0195] ───────────────────────────────────── Matting agent solution ───────────────────────────────── Silica particles having an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass The above-mentioned core layer cellulose acylate dope 1 part by mass ─────────────────────────────────

[0196] Preparation of Cellulose Acylate Film 1 The core layer cellulose acylate dope and the outer layer cellulose acylate dope were filtered through a filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm. The core layer cellulose acylate dope and the outer layer cellulose acylate dope on both sides of the core layer cellulose acylate dope were simultaneously cast onto a drum at 20°C through a casting nozzle (band caster). The film was then peeled off while still containing approximately 20% solvent by weight. Both ends of the film in the width direction were fixed with tenter clips, and the film was stretched transversely at a stretch ratio of 1.1 times while being dried. The film was then transported between the rolls of a heat treatment device and further dried to produce a 40 μm-thick optical film (transparent support), designated as Cellulose Acylate Film 1. The in-plane retardation of the resulting Cellulose Acylate Film 1 was 0 nm.

[0197] (Formation of Photo-Alignment Film PA1) A coating liquid PA1 for forming a photo-alignment film, which will be described later, was continuously applied onto the cellulose acylate film 1 using a wire bar. The support on which the coating film was formed was dried with hot air at 140° C. for 120 seconds, and then the coating film was irradiated with polarized ultraviolet light (10 mJ / cm ２ A photo-alignment film PA1 was formed by irradiating the substrate with a 0.5 μm-thick TAC (triacetyl cellulose) film.

[0198] ─────────────────────────────────── Coating liquid PA1 for forming photoalignment film ───────────────────────────────── Polymer PA-1 shown below: 100.00 parts by mass Acid generator PAG-1 shown below: 8.25 parts by mass Stabilizer DIPEA shown below: 0.6 parts by mass Xylene: 1126.60 parts by mass Methyl isobutyl ketone: 125.18 parts by mass ───────────────────────────────

[0199] Polymer PA-1

[0200] Acid generator PAG-1

[0201] Stabilizer DIPEA

[0202] The optically anisotropic layer-forming composition H1 was continuously applied onto the obtained photo-alignment film PA1 using a wire bar to form a coating layer H1. The coating layer H1 was then heated at 100°C for 5 minutes and cooled to 60°C to form a dry film. In the dry film, the liquid crystal compound was in a nematic phase. Then, an LED lamp (center wavelength 365 nm) was used to illuminate the film at an illuminance of 200 mW / cm. ２ The optically anisotropic layer H1 was formed on the photo-alignment film PA1 by irradiating the film with light for 2 seconds under the irradiation conditions of: The thickness of the optically anisotropic layer H1 was 1.9 μm.

[0203] The optically anisotropic layer H1 thus produced acts as a λ / 4 retardation layer for light with a wavelength of 940 nm.

[0204] [Preparation of Positive C Plate] The above-mentioned cellulose acylate film 1 was used as a temporary support. The cellulose acylate film 1 was passed through a dielectric heating roll at a temperature of 60°C to raise the film surface temperature to 40°C, and then an alkaline solution having the composition shown below was applied to one side of the film using a bar coater in an amount of 14 ml / m. ２ The film was heated to 110°C and transported for 10 seconds under a steam-type far-infrared heater manufactured by Noritake Co., Ltd. Next, pure water was applied to the film at a rate of 3 ml / m using the same bar coater. ２ Next, after repeating washing with water using a fountain coater and removing water with an air knife three times, the film was transported to a drying zone at 70° C. for 10 seconds and dried, thereby preparing an alkali-saponified cellulose acylate film 1.

[0205] ─────────────────────────────────── (Alkaline solution) ─────────────────────────────────── Potassium hydroxide 4.7 parts by mass Water 15.8 parts by mass Isopropanol 63.7 parts by mass Fluorine-containing surfactant SF-1 (C １４ H ２９ O (CH ２ CH ２Ｏ ) ２０ H) 1.0 part by mass Propylene glycol 14.8 parts by mass

[0206] An alignment layer-forming coating solution 2 having the following composition was continuously coated using a #16 wire bar onto the above-mentioned alkali-saponified cellulose acylate film 1. The cellulose acylate film 1 on which the coating film was formed was dried with hot air at 60°C for 60 seconds and then with hot air at 100°C for 120 seconds to form an alignment layer.

[0207] ─────────────────────────────────── (Coating liquid 2 for forming alignment layer) ───────────────────────────────── Polyvinyl alcohol (PVA103, manufactured by Kuraray) 2.4 parts by mass Isopropyl alcohol 1.6 parts by mass Methanol 36 parts by mass Water 60 parts by mass ─────────────────────────────────

[0208] The coating solution C1 for forming a positive C plate, which will be described later, was applied onto the alignment layer, and the resulting coating film was aged at 60° C. for 60 seconds, and then irradiated with 70 mW / cm 2 ２ An air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) was used, and the light output was 1000 mJ / cm ２The alignment state was fixed by irradiating the liquid crystal compound with ultraviolet light of 1000 nm to vertically align the liquid crystal compound, thereby producing a TAC film having a positive C-plate C1. The Rth(550) of the obtained positive C-plate C1 was −130 nm.

[0209] ─────────────────────────────────── (Coating liquid C1 for forming a positive C plate) ───────────────────────────────── 80 parts by mass of the following liquid crystal compound L-11 20 parts by mass of the following liquid crystal compound L-12 1 part by mass of the following vertically aligned liquid crystal compound promoter (S01) 8 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Co., Ltd.) 3 parts by mass of IRGACURE 907 (manufactured by BASF) 1 part by mass of Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 0.4 parts by mass of the following compound B03 170 parts by mass of methyl ethyl ketone 30 parts by mass of cyclohexanone ───────────────────────────────

[0210] Liquid crystal compound L-11 and liquid crystal compound L-12

[0211] Vertically aligned liquid crystal compound promoter (S01)

[0212] Compound B03

[0213] The positive C plate C1 side of the TAC film having the positive C plate C1 prepared above was bonded to the optically anisotropic layer side of the TAC film having the optically anisotropic layer H1 using the UV adhesive composition below, and the alignment layer and cellulose acylate film 1 on the optically anisotropic layer H1 side were removed to obtain a laminate (λ / 4 plate) including a retardation layer (optically anisotropic layer H1 and positive C plate C1).

[0214] (Preparation of UV adhesive composition) The following UV adhesive composition was prepared. ----------------------------------- UV adhesive composition ----------------------------------- CEL2021P (manufactured by Daicel Corporation) 70 parts by mass 1,4-butanediol diglycidyl ether 20 parts by mass 2-ethylhexyl glycidyl ether 10 parts by mass CPI-100P below 2.25 parts by mass -----------------------------------

[0215] CPI-100P

[0216] The refractive indices nx, ny, and nz of the prepared λ / 4 plate were measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ=589 nm) as the light source. From the measured refractive indices nx, ny, and nz, the Nz factor: Nz=(nx-nz) / (nx-ny) was calculated. Note that the refractive indices nx, ny, and nz were substituted with the respective refractive indices at a wavelength of 550 nm. The Nz factor was 0.5.

[0217] The prepared λ / 4 plate was left to stand for 24 hours under conditions of 20°C and 65% RH to condition the humidity, and then cut into a size of 200 mm x 15 mm (machine direction (MD) x width direction (TD) when applying composition H1 for forming an optically anisotropic layer), and attached to a testing machine (tensile testing machine "AG-IS" manufactured by Shimadzu Corporation) with a chuck spacing of 100 mm, and subjected to a tensile test at a tensile speed of 1000 mm / min under conditions of 20°C and 65% RH, and the tensile modulus was calculated from the ratio of the obtained initial stress to the initial strain. The tensile modulus was 2.0 x 10 3 The pressure was MPa.

[0218] <<Lamination of Linear Polarizer and λ / 4 Plate>> An adhesive (SK-2057, manufactured by Soken Chemical & Engineering Co., Ltd.) was applied to the surface of the λ / 4 plate facing the optically anisotropic layer H1 to form an adhesive layer, and the surface of the linear polarizer (lightly absorptive anisotropic film 1) opposite the glass substrate was attached to the adhesive layer in close contact with the adhesive layer to obtain laminate 11. The slow axis of the optically anisotropic layer H1 and the absorption axis of the lightly absorptive anisotropic film 1 were oriented at 45°. In this manner, a circular polarizer was produced.

[0219] The produced circular polarizer was cut out in the longitudinal direction at intervals of 100 mm, and ten of the cut-out films were measured every 0.48 mm in the width direction of the film using a contact-type web thickness meter (manufactured by Meisan Co., Ltd., product name "RC-101"), and the arithmetic mean value of the measured values ​​was calculated. The thickness of the circular polarizer was 0.03 mm.

[0220] [Evaluation] <Required Size> The required diameter W of the light source window was measured as follows.

[0221] 12 , a lens 14 was placed on the output side of an infrared light source 12, a circular polarizer 16 was placed in contact with the lens 14, and an aperture window 44 with an adjustable opening diameter was placed in contact with the circular polarizer 16. The lens 14 was placed so that the central axis of the light beam emitted by the infrared light source 12 coincided with the optical axis of the lens 14, and the circular polarizer 16 was placed so that its center passed through the optical axis of the lens 14 and its main surface was perpendicular to the optical axis. The center of the aperture window 44 was also aligned with the center of the circular polarizer 16.

[0222] A diode-pumped solid-state laser (manufactured by Sanctity Laser Technology Co., Ltd.) with a wavelength of 914 nm and an output of 100 mW was used as the infrared light source 12. A microlens SLM-04B-04N (manufactured by Sigma Koki Co., Ltd.) was used as the lens 14. The aperture window 44 had a thickness d A The glass was made by cutting windows of different diameters (windows with varying opening diameters) in a black paper of 1 mm.

[0223] The infrared light source 12 was driven to emit a laser. The laser light was diverged and expanded by the lens 14, and then passed through the circular polarizer and the aperture window 44. Of the light that passed through the aperture window 44, light at an angle (polar angle) of 80°±3° with respect to the central axis of the light beam emitted by the infrared light source 12 was collected by a plano-convex lens 42 (focal length f=25 mm), and the intensity I of the incident light was measured by a photodiode 46. When the light intensity I was measured while increasing the aperture diameter A of the aperture window 44, as shown in the graph of FIG. 13, the light intensity I increased sharply when it exceeded the threshold value of the aperture diameter A, and became I １００ The light intensity reached a steady value at I １００ 90% of I ９０ Let A be the aperture diameter that reaches ９０ The light source window diameter W was calculated using the following formula (see FIG. 14), taking into account the shielding effect due to the thickness of the aperture window 44 itself. The light source window diameter W was 1.5 mm. W=A ９０ -2d A ×tan 80°

[0224] <Evaluation of Measurement Variation> The following biological samples were prepared as test subjects.

[0225] (Biological Sample) Liver metastasis slice tissue specimens were prepared from a mouse xenograft model containing human pancreatic cancer SUIT2 cells. To establish liver metastasis in mice, human pancreatic cancer SUIT2 cells were injected intraspleenically. Livers were harvested 47 days after cancer cell injection, and slice specimens containing liver metastatic lesions were prepared. Livers harvested from mice were immediately frozen in a frozen tissue matrix. The frozen livers were serially sectioned into specimens approximately 40 μm thick using a cryostat. The liver slices were placed on glass plates and adhered to the glass with moisture.

[0226] Liver sections were fixed with 4% paraformaldehyde for 10 minutes, washed with phosphate-buffered saline, and then stained with 10 μg / mL Hoechst 33342 for 5 minutes. The stained sections were sealed with a coverslip and observed under an inverted fluorescence microscope (BZ-X800, Keyence). Fluorescent images were acquired using a ×40 objective lens with a fixed exposure time on a CMOS camera. Cell nuclei in healthy areas were relatively small and dispersed, with an average nuclear diameter of approximately 6.4 μm. Relatively large, aggregated cell nuclei were observed in metastatic areas, and an increase in cell nuclei (average diameter of approximately 10.8 μm) due to canceration was observed in metastatic areas.

[0227] Using the biological sample as the test object P, an apparatus as shown in FIG. 15 was fabricated and the variation in the polarization state (degree of circular polarization) of the reflected light was evaluated.

[0228] 15 , a lens 14 was disposed on the emission side of an infrared light source 12, and a circular polarizer 16 was disposed on the opposite side of the lens 14 from the infrared light source 12. The lens 14 was disposed so that the central axis of the light beam emitted by the infrared light source 12 coincided with the optical axis of the lens 14, and the circular polarizer 16 was disposed so that its center passed through the optical axis of the lens 14 and its main surface was perpendicular to the optical axis.

[0229] A diode-pumped solid-state laser (manufactured by Sanctity Laser Technology Co., Ltd.) with a wavelength of 914 nm and an output of 100 mW was used as the infrared light source 12. Furthermore, a microlens SLM-04B-04N (manufactured by Sigma Koki Co., Ltd.) was used as the lens 14.

[0230] A polarimeter 48 was used as a sensor for receiving reflected light from the inspection object P. The polarimeter 48 was a high dynamic range polarimeter (PAX1000, manufactured by Thorlabs, Inc.) consisting of an aperture (φ3 mm), a rotating λ / 4 plate, a fixed linear polarizer, and a photodiode.

[0231] A measurement point P1 on the object to be inspected P was determined, and the angle (polar angle) formed between the line connecting this measurement point P1 and the center of the lens 14 and the optical axis of the lens 14 was defined as the exit angle γ. The angle formed between the line connecting the measurement point P1 and the center of the lens 14 and the perpendicular to the object to be inspected P was defined as the incident angle θ. The angle formed between the line connecting the measurement point P1 and the center of the light receiving port of the polarimeter 48 and the perpendicular to the object to be inspected P was defined as the detection angle φ (see Figure 15).

[0232] A plano-convex lens 40 (focal length f = 25 mm) was placed on the line connecting the center of the lens 14 and the measurement point P1, and was focused on the measurement point P1. The plano-convex lens 40 condenses light at an angle of γ ± 3° and makes it incident on the measurement point P1.

[0233] In addition, a plano-convex lens 50 (focal length f = 30 mm) was placed on the line connecting the measurement point P1 and the center of the light receiving port of the polarimeter 48. The plano-convex lens 50 condenses light with an angle of φ±5.7° and makes it incident on the polarimeter 48.

[0234] (Measurement) The components of the measuring device were arranged so that the emission angle γ = 80°, the incidence angle θ = 50°, and the detection angle φ = 0°, and the infrared light source 12 was driven to emit unpolarized laser light. The emitted laser light was diverged and expanded by the lens 14, its polarization state was converted by the circular polarizer, and it was incident on the inspection object P. The reflected light that was incident on the inspection object P at the measurement point P1, scattered, and reflected was detected by the polarimeter 48.

[0235] The polarimeter 48 continuously rotates the slow axis of the rotating λ / 4 plate, measures the intensity of light transmitted through a fixed linear polarizer with a photodiode, and calculates the Stokes parameters by analyzing the modulated light intensity. The degree of circular polarization (DOCP) was calculated from the total intensity (SO) of scattered light of the reflected light and the Stokes polarization parameter (S3), which indicates the dominance of right-handed circularly polarized light over left-handed circularly polarized light.

[0236] The above measurement was performed at 100 different points in the cancerous region of the biological sample, and the standard deviation σcancer was calculated as an index of the variation in DOCP in the cancerous region. A smaller σcancer is preferable because it indicates smaller measurement variation. As a result, σcancer was 1.6.

[0237] [Example 2] A circular polarizer was produced in the same manner as in Example 1, except that a TAC (triacetyl cellulose) film was used as a substrate when forming the linear polarizer, and the circular polarizer was curved into a partially spherical shape with a radius of 20 mm, and evaluated in the same manner as in Example 1.

[0238] Example 3 A circular polarizer was produced in the same manner as in Example 2, except that the thickness of the positive C plate of the λ / 4 plate was changed, and was evaluated in the same manner as in Example 1.

[0239] The Rth(550) of the positive C plate was −80 nm, and the Nz factor of the λ / 4 plate was 0.7.

[0240] Example 4 A circular polarizer was prepared in the same manner as in Example 1, except that a wire grid polarizer (MLP-WG manufactured by Mitate Imaging Co., Ltd.) was used as the linear polarizer, and evaluated in the same manner as in Example 1.

[0241] The thickness of the circular polarizer was 0.20 mm.

[0242] Example 5 A circular polarizer was prepared in the same manner as in Example 4, except that the circular polarizer was curved into a partial sphere with a radius of 20 mm, and evaluated in the same manner as in Example 1.

[0243] Example 6 A circular polarizer was prepared in the same manner as in Example 5 except that the λ / 4 plate did not have a positive C plate, and was evaluated in the same manner as in Example 1.

[0244] Example 7 A circular polarizer was prepared in the same manner as in Example 1 except that the λ / 4 plate did not have a positive C plate, and was evaluated in the same manner as in Example 1.

[0245] Comparative Example 1 A circular polarizer was prepared in the same manner as in Example 4, except that AQWP05M-980 manufactured by THORLAB was used as the λ / 4 plate, and was evaluated in the same manner as in Example 1.

[0246] The thickness of the circular polarizer was 1.6 mm.

[0247] The results are shown in Table 1. In Table 1, the "coating type" in the type of linear polarizer refers to a linear polarizer using a dichroic dye, and "WGP" refers to a wire grid polarizer. The "liquid crystal coating type" in the type of λ / 4 plate refers to a λ / 4 plate having an optically anisotropic layer prepared using a composition for forming an optically anisotropic layer, and "quartz / MgF2" refers to a λ / 4 plate made of an inorganic material.

[0248]

[0249] It can be seen from Table 1 that the embodiment of the present invention can reduce the light source window diameter W compared to the comparative example. In other words, it can be seen that the polarization image measurement device can be made smaller.

[0250] A comparison between Examples 1 to 3 and Examples 4 to 6 reveals that the thickness of the circular polarizer is more preferably 0.03 mm or less. This comparison also reveals that the use of a coating-type absorptive linear polarizer is preferable because it allows the circular polarizer to be made thinner.

[0251] Furthermore, comparison of Example 1 with Examples 2 and 3, and comparison of Example 4 with Examples 5 and 6 reveals that the circular polarizer can be made even more compact by curving it.

[0252] Furthermore, a comparison between Example 1 and Example 7, and a comparison between Example 6 and Example 7, shows that the measurement variation of σcancer, i.e., DOCP, is reduced by making the Nz factor of the circular polarizer less than 1 or by making the circular polarizer have a curved structure.

[0253] Example 8 (Formation of Alignment Film) A glass substrate was prepared as a support. The following alignment film forming coating liquid P-1 was applied onto the support by spin coating. The support coated with this alignment film forming coating liquid P-1 was dried on a hot plate at 60°C for 60 seconds to form a coating film.

[0254] Coating liquid P-1 for forming alignment film ────────────────────────────────── · Photoalignment material below 1.00 parts by mass · Water 16.00 parts by mass · Butoxyethanol 42.00 parts by mass · Propylene glycol monomethyl ether 42.00 parts by mass ────────────────────────────────

[0255] Material for photo alignment

[0256] (Preparation of photo-alignment film) The obtained coating film was subjected to interference exposure with reference to Figure 3 of Patent Document WO2021 / 256413 to form a photo-alignment film P-1 having an alignment pattern. The crossing angle (crossing angle α) of the two beams was adjusted so that one period Λ (the length of 180° rotation of the optical axis) of the alignment pattern formed by the interference of the two laser beams was 1.88 μm.

[0257] (Formation of Optically Anisotropic Layer 1) The following composition B-1 was prepared as a liquid crystal composition.

[0258] Composition B-1 ----------------------------------- Rod-like liquid crystal compound L-1 shown below: 100.00 parts by mass Polymerization initiator (Irgacure OXE01, manufactured by BASF) 1.00 part by mass Methyl ethyl ketone 3939.00 parts by mass -----------------------------------

[0259] Rod-shaped liquid crystal compound L-1 (containing the following structure in the mass ratio shown on the right)

[0260] The optically anisotropic layer 1 was formed by applying the composition B-1 in multiple layers on the photo-alignment film P-1. First, the composition B-1 was applied as a first layer on the photo-alignment film P-1, heated, cooled, and then cured with UV light to form a liquid crystal fixing layer. After that, the second and subsequent layers were repeatedly applied to the liquid crystal fixing layer, and then similarly heated, cooled, and cured with UV light.

[0261] First, the first layer was formed by applying the following composition B-1 onto the photo-alignment film P-1, heating the coating to 80°C on a hot plate, and then irradiating the coating with ultraviolet light having a wavelength of 365 nm at 300 mJ / cm using a high-pressure mercury lamp in a nitrogen atmosphere at 80°C. 2 The coating film was irradiated with an irradiation dose of 1000 .mu.m to fix the alignment of the liquid crystal compound.

[0262] The second and subsequent layers were coated on top of the liquid crystal fixing layer, heated and cooled under the same conditions as above, and then cured with ultraviolet light to form a liquid crystal fixing layer. In this manner, coating was repeated until the desired total thickness was reached, thereby forming an optically anisotropic layer 1.

[0263] The refractive index difference Δn of the cured layer of the liquid crystal composition B-1 was determined by measuring the retardation Re(λ) and film thickness of the liquid crystal fixed layer obtained by applying the liquid crystal composition B-1 onto a separately prepared support with an alignment film for retardation measurement, aligning the liquid crystal compound so that its director was horizontal to the substrate, and then irradiating the liquid crystal with ultraviolet light to fix the liquid crystal. The retardation Re(λ) was divided by the film thickness to obtain Δn λ The retardation Re(λ) was measured at the target wavelength using an Axometrix Axoscan, and the film thickness was measured using an SEM. In the notation of Re(λ), λ is the wavelength of the incident light.

[0264] The optically anisotropic layer 1 finally has a Δn 940 × Film Thickness d = Re(940) was 470 nm, and it was confirmed by a polarizing microscope that a periodic orientation was observed.

[0265] The laminate including the optically anisotropic layer 1 thus prepared is a transmissive liquid crystal diffractive film that diffracts light (infrared light) with a wavelength of 940 nm, and when light is incident perpendicularly on the surface of the optically anisotropic layer 1, it diffracts right-handed circularly polarized light and left-handed circularly polarized light in directions that differ by 180°, with diffraction angles of approximately 30° for each.

[0266] The first image sensor for right- and left-circularly polarized light imaging was placed on the opposite side of the liquid crystal diffraction film from the incident side, in the direction in which right- and left-circularly polarized light is diffracted. The image sensors used were Sony XCG-CG510.

[0267] A polarization image measurement device was fabricated by combining it with the light irradiation system of Example 1, and the above-mentioned inspection object P (biological sample) was inspected. At that time, the light irradiation system and the light receiving system were arranged so that the emission angle γ = 0°, the incidence angle θ = 50°, and the detection angle φ = 0°.

[0268] The infrared light source 12 was driven to emit unpolarized laser light. The emitted laser light was diverged and expanded by the lens 14, its polarization state was converted by the circular polarizer, and it was incident on the inspection object P. The reflected light, which was incident on the measurement point P1 of the inspection object P and scattered and reflected, was polarized and separated by the transmission type liquid crystal diffraction film of the light receiving system prepared above, and the right-handed circularly polarized light and the left-handed circularly polarized light were detected by the image sensor for right-handed circular polarization imaging and the image sensor for left-handed circular polarization imaging, respectively.

[0269] By calculating the degree of circular polarization for each pixel from the signal intensity output from each pixel of the image sensor for right-handed circular polarization imaging and the image sensor for left-handed circular polarization imaging, it was possible to determine the degree of circular polarization for each region and detect cancerous regions.

[0270] [Example 9] An optically anisotropic layer 3 was prepared in the same manner as in Example 8, except that in Example 1, composition B-1 was changed to the following composition B-3, and composition B-3 was applied to the photo-alignment film P-1 in a single application.

[0271] Composition B-3 ───────────────────────────────── · 100.00 parts by mass of the above rod-shaped liquid crystal compound L-1 · 1.00 parts by mass of polymerization initiator (Irgacure OXE01, manufactured by BASF) · 3.7 parts by mass of the following chiral agent Ch-1 · 115.72 parts by mass of methyl ethyl ketone ───────────────────────────────

[0272] Chiral agent Ch-1

[0273] The optically anisotropic layer 3 finally has a Δn 940 × Film Thickness d = Re(940) was 470 nm, and it was confirmed by a polarizing microscope that a periodic orientation was observed.

[0274] The prepared laminate including the optically anisotropic layer 3 is a reflective liquid crystal diffractive film. This reflective liquid crystal diffractive film reflects and diffracts right-handed circularly polarized light with a wavelength of 940 nm, and when light is incident perpendicularly on the surface of the optically anisotropic layer 3, it reflects right-handed circularly polarized light in a direction at a polar angle of 30° and transmits left-handed circularly polarized light without diffracting it (0° direction).

[0275] The first image sensor for imaging right-handed circularly polarized light was placed on the incident side of the liquid crystal diffraction film, in the direction in which right-handed circularly polarized light was reflected and diffracted, and the second image sensor for imaging left-handed circularly polarized light was placed on the opposite side of the incident side of the liquid crystal diffraction film. The image sensors used were Sony XCG-CG510.

[0276] A polarization image measurement device was fabricated by combining it with the light irradiation system of Example 1, and the above-mentioned inspection object P (biological sample) was inspected. At that time, the light irradiation system and the light receiving system were arranged so that the emission angle γ = 0°, the incidence angle θ = 50°, and the detection angle φ = 0°.

[0277] The infrared light source 12 was driven to emit unpolarized laser light. The emitted laser light was diverged and expanded by the lens 14, its polarization state was converted by the circular polarizer, and it was incident on the inspection object P. The reflected light that was incident on the measurement point P1 of the inspection object P and scattered and reflected was polarized and separated by the reflective liquid crystal diffraction film of the light receiving system prepared above, and the right-handed circularly polarized light and left-handed circularly polarized light were detected by the image sensor for right-handed circular polarization imaging and the image sensor for left-handed circular polarization imaging, respectively.

[0278] By calculating the degree of circular polarization for each pixel from the signal intensity output from each pixel of the image sensor for right-handed circular polarization imaging and the image sensor for left-handed circular polarization imaging, it was possible to determine the degree of circular polarization for each region and detect cancerous regions.

[0279] The above results clearly demonstrate the effectiveness of the present invention.

[0280] 10 Polarized image measurement device 12 Infrared light source 14 Lens 16, 16a, 16b Circular polarizer 18 First image sensor 18a 1-1st image sensor 18b 1-2nd image sensor 20 Polarization separation filter 20a Patterned wire grid polarizer 20c, 20d Liquid crystal diffraction film 21a to 21d Region 22, 22b Linear polarizer 24, 24b λ / 4 plate 30 Light guide 32 White light source 34 Second light source 40, 42, 50 Plano-convex lens 44 Aperture window 46 Photodiode 48 Polarimeter 70 Endoscope system 71 Endoscope 71a Insertion section 71b Scanning section 71c Bending section 71d Tip 71e Angle knob 71f Zoom operation section 72 Processor device 73 Display 74 Operation input unit 75 Universal cord 76 Light source device

Claims

1. A polarization image measurement device comprising: an infrared light source that emits infrared light onto an object to be inspected; a lens that diverges the infrared light emitted from the infrared light source; a circular polarizer with a thickness of 1 mm or less that converts the infrared light diverged by the lens into circularly polarized light; a first image sensor that receives light that is reflected by the object to be inspected and is the circularly polarized light converted by the circular polarizer; and a polarization separation filter that is positioned on the optical path between the object to be inspected and the first image sensor and separates the reflected light into light of a plurality of polarization states.

2. The polarization image measurement device according to claim 1, wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the Nz factor of the λ / 4 plate is greater than 0 and less than 1.

3. The polarization image measurement device according to claim 1, wherein the circular polarizer has a curved structure.

4. The polarized image measurement device according to claim 1, wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the tensile modulus of the λ / 4 plate is 1 MPa to 10 GPa.

5. The polarization image measurement device according to claim 1, wherein the circular polarizer includes a linear polarizer and a λ / 4 plate, and the λ / 4 plate is formed using a liquid crystal compound.

6. The polarization image measurement device according to claim 1, wherein the circular polarizer comprises an absorptive linear polarizer.

7. The polarization image measurement device of claim 1, wherein the circular polarizer includes a cholesteric liquid crystal layer.

8. The polarization image measurement device according to claim 1, wherein the polarization separation filter is a patterned wire grid polarizer, and the polarization separation filter is adjacent to the first image sensor.

9. The polarized image measurement device according to claim 1, wherein the polarization separation filter is a liquid crystal diffractive film that selectively diffracts right-handed circularly polarized light and left-handed circularly polarized light.

10. The polarized light image measurement device according to claim 9, wherein the polarization separation filter selectively diffracts light with wavelengths in the infrared light range.

11. The polarized image measurement device according to claim 9, wherein the polarized light separation filter is a reflective liquid crystal diffractive film.

12. The polarization image measurement device according to claim 1, further comprising a second light source that emits light of a wavelength different from that of the infrared light source, and the light emitted from the second light source is converted into circularly polarized light by the circular polarizer.

13. The polarized image measurement device according to claim 12, wherein the light emitted from the second light source is infrared light.

14. A polarized image measurement device according to claim 12, further comprising a white light source having a plurality of luminance peaks, wherein the wavelength of the light emitted from said second light source is a wavelength between said plurality of luminance peaks.

15. The polarized image measuring device according to claim 1, further comprising: a white light source having multiple brightness peaks; and a second image sensor that captures the light emitted from the white light source reflected by the object under inspection, and displays the information obtained by the first image sensor superimposed on the image obtained by the second image sensor.

16. The polarized light image measurement device according to claim 1, wherein the first image sensor is sensitive to both the visible light region and the infrared light region.

17. The polarization image measurement device according to any one of claims 1 to 16, which is used in an endoscope system.

18. A polarization image measurement device comprising: an infrared light source that emits infrared light onto an object to be inspected; a circular polarizer having a thickness of 1 mm or less that converts the infrared light emitted from the infrared light source into circularly polarized light; a first image sensor that receives light that is reflected by the object to be inspected and is the circularly polarized light converted by the circular polarizer; and a polarization separation filter that is positioned on the optical path between the object to be inspected and the first image sensor and separates the reflected light into light of a plurality of polarization states.

Images