Lighting receiver

Abstract

To provide an illumination light receiving device that can improve a SN ratio in a light receiving element.SOLUTION: An illumination light receiving device D of the present invention comprises a specific polarized light element PMC, a polarized light selection optical element PS, a light receiving element IS, a light source and an illumination optical system of an illumination unit IL, and imaging optical systems Gr1, Gr2. The specific polarized light element PMC is arranged on a side of a first position where the light source is arranged and on a side of a second position where the light receiving element IS is arranged, with respect to an object WK, and is arranged inclined so that reflected light generated inside the specific polarized light element PMC passes through the outside of a light receiving surface of the light receiving element IS. The polarized light selection optical element PS is arranged closer to the second position than the first position with respect to the specific polarized light element PMC. A first optical axis AX1 of the illumination optical system and a second optical axis AX2 of the imaging optical system are coaxial with each other.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The present invention relates to an illumination and light-receiving device that illuminates a predetermined target object and receives reflected light thereof.

BACKGROUND ART

[0002] As an example of an illumination and light-receiving device that illuminates a predetermined target object and receives reflected light thereof, there is a sample measurement apparatus disclosed in Patent Document 1, for example. The sample measurement apparatus disclosed in Patent Document 1 includes a light source, a light-receiving element that receives light emitted from the light source, and an optical element that is disposed closer to the light source than the light-receiving element and selectively extracts light of a polarization component in a specific direction from incident light, the sample measurement apparatus including both a specific polarizing element that is disposed closer to the light source than a measurement target sample and transmits or reflects the light emitted from the light source, and a specific polarizing element that is disposed closer to the light-receiving element than the measurement target sample and transmits or reflects light that has been transmitted through or reflected by the measurement target sample. The specific polarizing element is a transmissive or reflective polarizing element that has an in-plane x-axis direction and a y-axis direction orthogonal thereto, and has a Jones matrix that varies depending on the in-plane position.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Since the specific polarizing element has a structure in which, for example, a liquid crystal is sandwiched between glass plates, reflection occurs due to the glass plates and the liquid crystal. The reflected light generated inside this specific polarizing element has a changed polarization state, so it is difficult to remove before the light-receiving element, and becomes stray light (noise), which reduces the SN ratio at the light-receiving element.

[0005] This invention was made in view of the above circumstances, and its purpose is to provide an illumination light receiving device that can improve the signal-to-noise ratio of the light receiving element. [Means for solving the problem]

[0006] As a result of various studies, the inventors have found that the above objective can be achieved by the present invention as described below. That is, an illumination and light receiving device according to one aspect of the present invention comprises a specific polarizing element which is a polarizing element whose Jones matrix differs depending on its position in the plane, a polarization-selective optical element which selectively extracts and emits polarization components in a specific direction, a light receiving element which receives light on a predetermined light receiving surface, a light source which emits light, an illumination optical system which uses the light emitted from the light source as illumination light to illuminate a predetermined object, and an imaging optical system which forms an image of the object on the light receiving surface of the light receiving element, wherein the specific polarizing element is positioned on the first position side where the light source is positioned and on the second position side where the light receiving element is positioned with respect to the object, and is tilted so that reflected light generated inside the specific polarizing element passes outside the light receiving surface of the light receiving element, the polarization-selective optical element is positioned on the second position side from the first position with respect to the specific polarizing element, and the first optical axis of the illumination optical system and the second optical axis of the imaging optical system are coaxial with each other. Preferably, in the above-described illumination light receiving device, the light-receiving surface of the light-receiving element has a rectangular shape with a relatively short side and a relatively long side, and the specific polarizing element is positioned at an angle such that the reflected light passes outside the long side. Preferably, in the above-described illumination light receiving device, the light-receiving surface of the light-receiving element has a rectangular shape with a relatively short side and a relatively long side, and the specific polarizing element is positioned with its third optical axis tilted in the direction of the short side along the short side from the normal to the light-receiving surface of the light-receiving element, such that the reflected light passes outside the long side.

[0007] In such an illumination light receiving device, the specific polarizing element is positioned at an angle such that the reflected light generated inside it passes outside the light-receiving surface of the light-receiving element. Therefore, the reflected light is not received by the light-receiving surface, and thus the signal-to-noise ratio of the light-receiving element can be improved.

[0008] In another aspect, in the illumination and light-receiving device described above, the light-receiving surface of the light-receiving element has a rectangular shape with an aspect ratio of 3:4, the imaging optical system includes a first optical system disposed closer to a fourth position where an object is placed than a third position where the specific polarizing element is disposed, and when the allowable incident angle of the specific polarizing element is α, the tilt angle of the specific polarizing element is β, the angle formed by the principal ray at the maximum image height of the imaging optical system and the second optical axis of the imaging optical system in the vicinity of the specific polarizer is θ, the field of view of the imaging optical system is FoV, and the focal length of the first optical system is EFL, the relation FoV / (2×EFL)<Sin(α / 1.8) is satisfied.

[0009] Such an illumination and light-receiving device can suitably improve the SN ratio at the light-receiving element for a light-receiving element having a rectangular light-receiving surface with a general aspect ratio of 3:4. The EFL, the focal length of the first optical system, refers to the focal length of the lens when the first optical system is composed of a single lens, and refers to the combined focal length of the plurality of lenses when the first optical system is composed of a plurality of lenses. [Effects of the Invention]

[0010] The illumination and light-receiving device according to the present invention can improve the SN ratio at the light-receiving element. [Brief Description of the Drawings]

[0011] [Figure 1] It is a schematic diagram for explaining the configuration of the illumination and light-receiving device in the embodiment. [Figure 2] It is a diagram for explaining the light-receiving element in the illumination and light-receiving device. [Figure 3] It is a diagram for explaining the conditions satisfied by the illumination and light-receiving device with respect to the tilt angle. [Figure 4] By way of example, it is a diagram for explaining the incident angle dependency of the specific polarizing element. [Figure 5] By way of example, it is a diagram for explaining the application of the illumination and light-receiving device to a tilt measurement device. [Mode for Carrying Out the Invention]

[0012] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In each figure, components denoted by the same reference numerals are identified as identical components, and their descriptions are omitted where appropriate. In this specification, general reference numerals are used without subscripts, while individual components are indicated by subscripts.

[0013] Figure 1 is a schematic diagram illustrating the configuration of the illumination light receiving device in an embodiment. Figure 1 shows the illumination light receiving device D viewed from a direction perpendicular to the diagonal of the light-receiving surface of the light-receiving element and the optical axis of the imaging optical system. Figure 2 is a diagram illustrating the light-receiving element in the illumination light receiving device. Figure 3 is a diagram illustrating the conditions that the illumination light receiving device must satisfy with respect to the tilt angle. Figure 4 is a diagram illustrating the incident angle dependence of a specific polarizing element as an example. Figure 4A shows a graph of the phase difference with respect to incident angles φh and φp, where the horizontal axis is the incident angle φh and φp [deg] and the vertical axis is the phase difference [deg]. The dashed line is the graph of the phase difference with respect to the first incident angle (e.g., the horizontal incident angle) φh, and the solid line is the graph of the phase difference with respect to the second incident angle (e.g., the vertical incident angle) φp. Figure 4B shows the first angle of incidence (e.g., the horizontal angle of incidence) φh, and Figure 4C shows the second angle of incidence (e.g., the vertical angle of incidence) φ.

[0014] In this embodiment, the illumination and light receiving device D is a device that illuminates a predetermined object (workpiece) WK and receives the reflected light. For example, as shown in Figure 1, it comprises an illumination unit IL, a beam splitter BS, a specific polarizing element PMC, a first optical system Gr1, a polarization-selective optical element PS, a second optical system Gr2, and a light receiving element IS. The predetermined object WK is arbitrary and not limited.

[0015] The illumination unit IL is a device that irradiates illumination light onto a predetermined object WK placed on a predetermined surface, and comprises, for example, a light source, a bandpass filter, and an optical system. The light source is powered by a predetermined power source and emits predetermined light, and is configured to include, for example, a laser light source that emits polarization components in a specific direction. Alternatively, for example, the light source may comprise a light-emitting diode (LED) that emits randomly polarized light, and a polarizer that receives the light emitted from the LED, selectively extracts polarization components in a specific direction, and emits them as emitted light. The bandpass filter is an optical element that transmits light in a predetermined wavelength range in the incident light and emits it as emitted light, and blocks light in the incident light that is not in the wavelength range. The wavelength range is preferably narrower, and it is preferable that monochromatic light is emitted from the bandpass filter. The optical system is configured to direct the focused light into a beam splitter BS, and for example, it comprises two lenses: a first lens that converts the incident light into parallel light and emits it as exit light, and a second lens that focuses the incident light and emits it as exit light.

[0016] A beam splitter BS is an optical element that splits incident light into two beams of light at a predetermined splitting ratio at the wavelength of illumination light and emits them. A beam splitter BS can be a so-called plate type or a thin film type, but in the example shown in Figure 1, a so-called cube type is used. This cube-type beam splitter BS is formed by bonding two right-angle prisms together at their inclined surfaces to form a roughly cubic shape, and the inclined surface of one of the right-angle prisms is coated with a dielectric multilayer film for splitting incident light.

[0017] The specific polarizing element PMC is a polarizing element that has an x-axis direction and a y-axis direction orthogonal thereto in its plane, and whose Jones matrix varies depending on the position within the plane, which is disclosed, for example, in the aforementioned Patent Document 1. In an example, the specific polarizing element PMC has M regions in the xy plane, including a region Ri, a region Rj located at a position symmetrical about the central axis of the specific polarizing element PMC with respect to the region Ri, and a region Rk adjacent to the region Rj, and satisfies the following Condition A and Condition B. Condition A is that when light whose Jones vector is Jxy is incident on the region Ri, and the transmitted light is further incident on the region Rj, the Jones vector of the light transmitted through the region Rj is the same as Jxy. Condition B is that the Jones matrix of the region Rk is different from the Jones matrix of the region Rj. The specific polarizing element PMC will be further described later.

[0018] The first optical system Gr1 is an objective lens that irradiates the incident light onto the object WK arranged on the arrangement surface.

[0019] The polarization selective optical element PS is a polarizer that selectively extracts a polarization component in a specific direction from incident light and emits it as outgoing light. The polarization selective optical element PS selectively extracts, for example, a polarization component in a predetermined direction (e.g., Z-polarized component) that has passed through the specific polarizing element PMC, been reflected by the object WK, and passed through the specific polarizing element PMC and the beam splitter BS, and emits it as outgoing light.

[0020] The light receiving element IS is a device that receives incident light on a predetermined light receiving surface and performs photoelectric conversion to output an electrical signal corresponding to the incident light. The light receiving element IS is configured to include a two-dimensional image sensor having a rectangular light receiving surface with relatively short short sides and relatively long long sides, for example, a rectangular light receiving surface with a common 3:4 aspect ratio as shown in Figure 2.

[0021] The second optical system Gr2 is an optical system for forming an optical image of the object WK illuminated by the illumination light on the light receiving surface of the light receiving element IS together with the first optical system Gr1, and is configured to include one or a plurality of lenses.

[0022] The light source, the band-pass filter, and the optical system are sequentially arranged in this order along the first optical axis AX1, with their respective optical axes aligned to the optical axis (first optical axis) AX1. The band-pass filter and the optical system constitute an illumination optical system, and the first optical axis AX1 is the optical axis of this illumination optical system (the optical axis of the illumination unit IL). Light emitted from the light source (the Y-polarized component in the present embodiment) enters the band-pass filter, becomes light of a predetermined wavelength range, enters the optical system, and is emitted from the optical system as illumination light of the illumination unit IL.

[0023] The illumination unit IL including the light source, the band-pass filter, and the optical system is arranged relative to the beam splitter BS such that the first optical axis AX1 intersects the inclined surface of the beam splitter BS at 45°. The intersection point of the first optical axis AX1 on the inclined surface of the beam splitter BS is preferably the central position of the inclined surface (for example, the intersection point of the two diagonals when the inclined surface is rectangular). Accordingly, the illumination light emitted from the illumination unit IL propagates (travels) along the first optical axis AX1, enters the beam splitter BS, and its propagation direction (travel direction) is bent by 90° at the inclined surface. That is, the first optical axis AX1 in the light source, the band-pass filter, and the optical system is bent by 90°. The illumination light is reflected by the inclined surface, becomes illumination light of a polarized component in a predetermined direction (Y-polarized component), and propagates along the first optical axis AX1 that is bent by 90° at the inclined surface.

[0024] The specific polarizing element PMC is positioned relative to the object WK on the first position side where the light source is positioned and on the second position side where the light receiving element IS is positioned. As shown in Figure 1, the specific polarizing element PMC is positioned at an angle such that reflected light (second reflected light) generated inside the specific polarizing element PMC passes outside the light-receiving surface of the light-receiving element IS. More specifically, the specific polarizing element PMC is positioned at an angle such that the second reflected light passes outside the long side. More precisely, the specific polarizing element PMC is positioned with its third optical axis tilted in the direction of the short side, along the short side, from the normal to the light-receiving surface of the light-receiving element IS, so that the second reflected light passes outside the long side. Illumination light with a polarization component in the predetermined direction, emitted from the beam splitter BS, is incident on the specific polarizing element PMC and emitted from the specific polarizing element PMC as a polarization component according to the Jones matrix corresponding to the incident position of the specific polarizing element PMC.

[0025] The first optical system Gr1 is positioned on the fourth position side of the third position where the specific polarizing element PMC is positioned, towards the fourth position where the object WK is positioned. Illumination light with a polarization component according to the Jones matrix corresponding to its incident position, emitted from the specific polarizing element PMC, is incident on the first optical system Gr1 and illuminates the object WK. The reflected light from the object WK (first reflected light) is incident on the first optical system Gr1, incident on the specific polarizing element PMC via the first optical system Gr1, and is emitted from the specific polarizing element PMC as a polarization component according to the Jones matrix corresponding to the incident position of the specific polarizing element PMC. The first reflected light with a polarization component according to the Jones matrix corresponding to its incident position, emitted from the specific polarizing element PMC, is incident on the beam splitter BS, and only the transmitted component separated by a predetermined splitting ratio is emitted.

[0026] The polarization-selective optical element PS is positioned on the second position side where the photodetector IS is positioned, relative to the specific polarizing element PMC, from the first position where the light source is positioned. More specifically, in the example shown in Figure 1, the polarization-selective optical element PS is positioned on the emission side of the beam splitter BS, where the first reflected light of the illumination light transmitted through the inclined surface is emitted, and on the object side (object WK side) of the second optical system Gr2. The first reflected light emitted from the beam splitter BS is incident on the second optical system Gr2, and an optical image of the object WK (an optical image of the object WK composed of the first reflected light of polarization components orthogonal to the predetermined direction) is imaged onto the photodetector surface of the photodetector IS. The photodetector IS performs photoelectric conversion and outputs an electrical signal corresponding to the optical image of the object WK received on the photodetector surface. This electrical signal output from the photodetector IS is output to an appropriate device (for example, an information processing device such as a computer) that processes this electrical signal.

[0027] In this embodiment, the first optical system Gr1, the specific polarizing element PMC, the beam splitter BS, the polarization-selective optical element PS, the second optical system Gr2, and the photodetector IS are arranged sequentially along the second optical axis AX2, from the object side to the image side (the photodetector IS side), with their respective optical axes aligned with the optical axis (second optical axis) AX2. The first optical system Gr1 and the second optical system Gr2 constitute an imaging optical system that forms an optical image of the object WK illuminated by the illumination light, and the second optical axis AX2 is the optical axis of this imaging optical system. The imaging optical system and the illumination optical system are arranged such that the first optical axis AX1 of the illumination optical system and the second optical axis AX2 of the imaging optical system are orthogonal to each other on the inclined surface of the beam splitter BS, and since the first optical axis AX1 of the illumination optical system is bent by 90° on the inclined surface of the beam splitter BS, the first optical axis AX1 of the illumination optical system and the second optical axis AX2 of the imaging optical system are coaxial with each other. Here, the first position of the light source can be considered as the position on the inclined surface where the first optical axis AX1 of the illumination optical system and the second optical axis AX2 of the imaging optical system intersect.

[0028] Here, the specific polarizing element PMC has an incident angle dependence, and therefore, the specific polarizing element PMC has an allowable incident angle at which it can emit incident light as emitted light with a polarization component according to the Jones matrix corresponding to the incident position of the specific polarizing element PMC. For this reason, the first optical system Gr1 satisfies the condition of equation 1 below. When the allowable incident angle of the specific polarizing element PMC is α, the tilt angle of the specific polarizing element PMC is β, the angle between the principal ray of the maximum image height of the imaging optical system and the second optical axis AX2 is θ, the field of view of the imaging optical system is FoV, and the focal length of the first optical system Gr1 is EFL, then from Figure 3, α > (θ + β), so β ​​< α - θ. The required tilt angle β in the specific polarizing element PMC is β > (0.6 × θ + θ) / 2, which is obtained from the aspect ratio on the light-receiving surface of the photodetector IS. From the above, we find that θ < α / 1.8 and sinθ = FoV / (2 × EFL), and from these, we can derive the inequality in equation 1 below. Equation 1; FoV / (2×EFL) <Sin(α / 1.8)

[0029] Furthermore, in a specific polarizing element PMC, the dependence of the phase difference on the incidence angle with respect to the first incidence angle φh in the first direction (e.g., horizontal direction, see Figure 4B) and the dependence of the phase difference on the incidence angle with respect to the second incidence angle φp in the second direction orthogonal to the first direction (e.g., vertical direction, see Figure 4C) are different, as shown in Figure 4A, for example. In the case of the phase difference's dependence on the incidence angle with respect to the first incidence angle φh, the phase difference changes relatively large with respect to the change in the first incidence angle φh, while in the case of the phase difference's dependence on the incidence angle with respect to the second incidence angle φp, the phase difference changes relatively small with respect to the change in the second incidence angle φp. That is, the incidence angle dependence of the phase difference with respect to the second incidence angle φp is small. For this reason, in the above embodiment, it is preferable to arrange the specific polarizing element PMC such that the tilt angle β shown in Figure 3 is the second incidence angle φp shown in Figure 4C. In other words, in the above embodiment, it is preferable to arrange the specific polarizing element PMC such that the tilt angle is the incidence angle at which the phase difference has little incidence angle dependence.

[0030] In this embodiment, the bandpass filter and the optical system correspond to an example of an illumination optical system that uses light emitted from the light source as illumination light to illuminate a predetermined object. The first optical system Gr1 and the second optical system Gr2 correspond to an example of an imaging optical system that forms an image of the object on the light-receiving surface of the light-receiving element.

[0031] As described above, in this embodiment, the illumination light receiving device D is positioned with the specific polarizing element PMC tilted so that the second reflected light generated inside it passes outside the light-receiving surface of the light-receiving element IS. Therefore, the second reflected light is not received by the light-receiving surface, and thus the signal-to-noise ratio of the light-receiving element IS can be improved.

[0032] The above-described illumination light receiving device D can suitably improve the signal-to-noise ratio (SNR) of a light receiving element IS having a rectangular light-receiving surface with a typical 3:4 aspect ratio, when the first optical system Gr1 satisfies the conditions of Equation 1 described above.

[0033] Furthermore, the illumination and light receiving device D in the above-described embodiment can be applied to various purposes. For example, as disclosed in Patent Document 1, it can be applied to surface observation and bulk defect observation. In surface observation, the illumination and light receiving device D can be applied to measuring tilt and waviness, measuring contamination such as defects and particles, measuring minute steps formed by micropatterning, and measuring roughness. In bulk defect observation, the illumination and light receiving device D can be applied to observing bubbles in glass and detecting non-uniform refractive index areas due to distortion, etc.

[0034] As an example, the measurement of the inclination of an object WK will be described. Figure 5 is a diagram illustrating the application of the illumination receiving device to an inclination measuring device as an example. Figure 5 shows the polarization-selective optical element PS, beam splitter BS, specific polarizing element PMC, first optical system Gr1, and object WK, with the remaining components omitted from the diagram.

[0035] When measuring the inclination of an object WK, the specific polarizing element PMC is configured to include, for example, a first region AR1 that generates a phase difference of half a wavelength λ / 2 between incident light and emitted light, and a second region AR2 that does not generate the phase difference, wherein the first region AR1 and the second region AR2 are concentric with each other, and at least one first boundary in the first region is shared with a second boundary in the second region. The wavelength λ of the half-wavelength λ / 2 is the wavelength λ of the illumination light that illuminates the object WK. More specifically, the second region AR2 is formed in a circular shape with a predetermined diameter, and the first region AR1 is formed in a ring shape (ring-shaped, donut-shaped) so as to surround the outer circumference of the second region AR2.

[0036] In Figure 5, if the object WK is a plate-like body with a flat front and back surface, as shown by the solid line, if the object WK is placed horizontally on the placement surface and is not tilted, the Y-polarized illumination light and the reflected illumination light reflected by the object WK cannot pass through the polarization-selective optical element PS, and therefore do not reach the photodetector IS, and are not received at the photodetector IS. On the other hand, as shown by the dashed line, if the object WK is tilted, a portion of the Y-polarized illumination light and the reflected illumination light reflected by the object WK become Z-polarized components, pass through the polarization-selective optical element PS, and reach the photodetector IS, and are received at the photodetector IS. For example, illumination light LB1 emitted from the illumination unit IL is reflected by the beam splitter BS, passes through the second region AR2 of the specific polarizing element PMC, and is incident on the tilted object WK via the first optical system Gr1 and reflected. The first reflected light of the illumination light LB1 is incident on the first region AR1 of the specific polarizing element PMC via the first optical system Gr1, creating a phase difference of half a wavelength λ / 2, which becomes a Z-polarized component and is incident from the specific polarizing element PMC to the beam splitter BS. This first reflected light of the Z-polarized component passes through the beam splitter BS and is incident on the polarization-selective optical element PS. Since the polarization-selective optical element PS is set to transmit the Z-polarized component, it passes through it and reaches the light-receiving surface of the photodetector IS via the second optical system Gr2. For example, illumination light LB2 emitted from the illumination unit IL is reflected by the beam splitter BS and incident on the first region AR1 of the specific polarizing element PMC, creating a phase difference of half a wavelength λ / 2, which becomes a Z-polarized component, which is then incident on the tilted object WK via the first optical system Gr1 from the first region AR1 and reflected. The first reflected light of the illumination light LB2 is incident on the second region AR2 of the specific polarizing element PMC via the first optical system Gr1, and then incident on the beam splitter BS from the specific polarizing element PMC. This first reflected light of the Z polarization component passes through the beam splitter BS and is incident on the polarization-selective optical element PS, and passes through this to reach the light-receiving surface of the photodetector IS via the second optical system Gr2. In this way, when the object WK is tilted, a portion of the Z polarization component of the first reflected light reaches the light-receiving surface of the photodetector IS, and an electrical signal corresponding to the Z polarization component is output from the photodetector IS. By detecting this electrical signal with the information processing device, the tilt of the object WK can be detected.By pre-associating the magnitude of the electrical signal with the tilt angle, the tilt angle of the object WK can be measured.

[0037] To illustrate the present invention, the embodiments have been adequately and fully described above with reference to the drawings. However, those skilled in the art should recognize that it is easy to modify and / or improve upon the embodiments described above. Therefore, unless such modifications or improvements implemented by those skilled in the art fall outside the scope of the claims, such modifications or improvements shall be considered to be included within the scope of the claims. [Explanation of Symbols]

[0038] D: Illumination light receiving device, WK: Object, IL: Illumination unit, AX1: First optical axis of illumination optical system, BS: Beam splitter, PMC: Polarizing element, Gr1: First optical system, Gr2: Second optical system, PS: Polarization-selective optical element, IS: Light receiving element

Claims

1. A specific polarizing element is a polarizing element in which the Jones matrix differs depending on the position in the plane, A polarization-selective optical element that selectively extracts and emits polarization components in a specific direction, A light-receiving element that receives light at a predetermined light-receiving surface, A light source that emits light, An illumination optical system that uses the light emitted from the aforementioned light source as illumination light to illuminate a predetermined object, The system comprises an imaging optical system that forms an image of the object onto the light-receiving surface of the light-receiving element, The specified polarizing element is positioned relative to the object on the first position side where the light source is located and on the second position side where the light-receiving element is located, and is positioned at an angle such that reflected light generated inside the specified polarizing element passes outside the light-receiving surface of the light-receiving element. The polarization-selective optical element is positioned on the second position side of the first position relative to the specific polarization element. The first optical axis of the illumination optical system and the second optical axis of the imaging optical system are coaxial with each other. The light-receiving surface of the light-receiving element has a rectangular shape with an aspect ratio of 3:

4. The imaging optical system includes a first optical system positioned on the fourth position side of the object being positioned, from the third position where the specific polarizing element is positioned. The first optical system satisfies the following condition: when the allowable incident angle of the specific polarizing element is α, the tilt angle of the specific polarizing element is β, the angle between the principal ray of the maximum image height of the imaging optical system and the second optical axis of the imaging optical system near the specific polarizing element is θ, the field of view of the imaging optical system is FoV, and the focal length of the first optical system is EFL, FoV / (2×EFL) < sin(α / 1.8). Light receiving device.

Images