Illumination light receiving device

Abstract

The illumination light receiving device of the present invention comprises: a wavelength plate; a polarization selection optics; a light receiving device; a light source; an illumination optical system; and an imaging optical system. In the wavelength plate, a first region in which a half-wavelength phase difference occurs and a second region not having a polarization change function are concentric with each other, and at least one first boundary in the first region and a second boundary in the second region are shared. The wavelength plate is disposed on the side of a first position of the light source and on the side of a second position of the light receiving device with respect to an object, and the polarization selection optical device is disposed on the side of the second position with respect to the wavelength plate with respect to the first position. The optical axes of the illumination optical system and the imaging optical system are coaxial with each other.

Description

Technical Field

[0001] The present invention relates to an illumination light receiving device that illuminates a specified object and receives the reflected light thereof. Background Art

[0002] As an example of an illumination light receiving device that illuminates a specified object and receives the reflected light thereof, for example, there is a sample measuring device disclosed in Patent Document 1. The sample measuring device disclosed in Patent Document 1 includes: a light source; a light receiving device that receives the light emitted from the light source; and an optical device that is disposed on one side of the light source with respect to the light receiving device and selectively extracts light having a polarization component in a specific direction in the incident light. The sample measuring device includes: a specific polarization element that is disposed on one side of the light source with respect to the measurement object sample and transmits or reflects the light emitted from the light source; and a specific polarization element that is disposed on one side of the light receiving device with respect to the measurement object sample and transmits or reflects the light that has been transmitted or reflected by the measurement object sample, both of which. The specific polarization element is a transmissive or reflective polarization element that has an x-axis direction and a y-axis direction orthogonal to the direction in a plane and whose Jones matrix varies depending on the position in the plane.

[0003] Since the specific polarization element has a structure in which, for example, liquid crystal is sandwiched between glass plates, reflection occurs based on the glass plates and the liquid crystal. The reflected light generated inside the specific polarization element is difficult to be removed in front of the light receiving device due to polarization change, and thus the reflected light becomes stray light (noise), resulting in a decrease in the SN ratio (signal-to-noise ratio) in the light receiving device.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: International Publication Gazette No. 2021 / 039900 Summary of the Invention

[0007] In view of the above circumstances, the present invention is made, and an object thereof is to provide an illumination light receiving device capable of improving the SN ratio in a light receiving device.

[0008] The lighting light receiving device involved in the present invention includes: a wavelength plate; a polarization selection optical device; a light receiving device; a light source; a lighting optical system; and a camera optical system. The wavelength plate has one or more first regions and one or more second regions. The first region generates a phase difference of half a wavelength, and the second region does not have a function of changing polarization. The wavelength plate is disposed on one side of an object with respect to a first position where the light source is disposed and on one side of the object with respect to a second position where the light receiving device is disposed. The first region and the second region are formed in a concentric circle shape with respect to each other, and at least one first boundary in the first region and a second boundary of the second region are shared. The polarization selection optical device is disposed at a position on one side of the second position with respect to the wavelength plate compared to the first position. The first optical axis of the lighting optical system and the second optical axis of the camera optical system are coaxial with each other.

[0009] The above objects, features, and other objects, features, and advantages of the present invention will become clearer through the following detailed description and the illustration of the drawings. Description of the Drawings

[0010] Figure 1 It is a schematic diagram for explaining the configuration of the lighting light receiving device in the embodiment.

[0011] Figure 2 It is a diagram for explaining the wavelength plate of the lighting light receiving device.

[0012] Figure 3 It is a diagram for explaining the operation and effect of the lighting light receiving device.

[0013] Figure 4 It is a diagram for explaining the comparative example.

[0014] Figure 5 It is a diagram for explaining the modified embodiment of the lighting light receiving device.

[0015] Figure 6 It is a diagram for explaining an example in which the lighting light receiving device is applied to an inclination measuring device. Detailed Embodiment

[0016] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In addition, components denoted by the same reference numerals in each figure represent the same components, and the description thereof will be omitted accordingly. In this specification, when representing a general component, the component is represented by a reference numeral omitting the suffix, and when representing an individual component, the component is represented by a reference numeral with a suffix added.

[0017] Figure 1 It is a schematic diagram for explaining the configuration of the illumination light receiving device in the embodiment. Figure 1 It is a cross-sectional view when the illumination light receiving device D is cut along a plane including each optical axis. Figure 2 It is a diagram for explaining the wave plate of the illumination light receiving device. Figure 2 A in it is the front view of the wave plate. Figure 2 B in it is a diagram for explaining the function and effect of the wave plate. Figure 2 C in it is a diagram for explaining the modified embodiment of the wave plate.

[0018] The illumination light receiving device D in the embodiment is a device that illuminates a specified object (workpiece) WK and receives the reflected light therefrom. For example, as Figure 1 shown, it includes: an illumination unit IL; a beam splitter BS; a wave plate WP; a first optical system Gr21; a polarization selection optical device PS; a second optical system Gr22; and a light receiving device IS. The specified object WK is an arbitrary object and is not limited.

[0019] The illumination unit IL is a device that irradiates illumination light onto a specified object WK disposed on a specified placement surface. For example, it includes: a light source LS; a polarizer PL; a band-pass filter BPF; and an optical system Gr11.

[0020] The light source LS is a device that is powered by a specified power supply and emits specified light. For example, it is configured to include a light emitting diode (LED) or the like that emits randomly polarized light.

[0021] The polarizer PL is an optical device that selectively extracts the polarization component in a specified direction and uses it as the emitted light.

[0022] The band-pass filter BPF is an optical device that transmits light in a specified wavelength range in the incident light and emits it as the emitted light and blocks light outside the wavelength range in the incident light. The narrower the wavelength range, the better. Preferably, monochromatic light is emitted from the band-pass filter BPF.

[0023] The optical system Gr11 allows the converged light to enter the beam splitter BS. For example, it is configured to include two lenses, a first lens L11 and a second lens L12. The first lens L11 changes the incident light into parallel light and emits it as the emitted light, and the second lens L12 converges the incident light and emits it as the emitted light.

[0024] The beam splitter BS is an optical device that divides incident light into two beams at a specified division ratio at the wavelength of the illumination light and emits these beams. The beam splitter BS can be of the so-called plate type or thin film type, and in Figure 1 the example shown, a cubic type is adopted. The cubic beam splitter BS is a beam splitter in the shape of a roughly cube formed by gluing two right-angled prisms to each other through their inclined surfaces, and a dielectric multilayer film for dividing incident light is formed by covering (coating) the inclined surface of one of the right-angled prisms.

[0025] The wavelength plate WP is an optical device having one or more first regions and one or more second regions. The first region generates a phase difference of half a wavelength λ / 2 between the incident light and the emitted light, and the second region does not have a function of changing polarization. The wavelength plate WP is formed such that the first region and the second region are concentric with each other and at least one first boundary in the first region and a second boundary of the second region are shared. The wavelength λ of the half wavelength λ / 2 is the wavelength λ of the light emitted from the band-pass filter BPF and is also the wavelength λ of the illumination light for the illumination object WK.

[0026] For example, as Figure 2As shown in FIG. A, the wave plate WP includes: a first second region AR2-1, which is circular with a specified diameter and does not change the polarization between the incident light and the emitted light; a first region AR1, which is annular (ring-shaped or donut-shaped) and is formed so as to surround the outer periphery of the second region AR2-1, and generates a phase difference of half wavelength λ / 2 between the incident light and the emitted light; a second second region AR2-2, which is annular (ring-shaped or donut-shaped) and is formed so as to surround the outer periphery of the first region AR1, and does not change the polarization between the incident light and the emitted light. The boundary of the outer periphery of the second region AR2-1 and the boundary of the inner periphery of the first region AR1 are shared, and the boundary of the outer periphery of the first region AR1 and the boundary of the inner periphery of the second region AR2-2 are shared. The first region AR1 has a specified width (first width) in the radial direction. The second region AR2-2 has a specified width (second width) in the radial direction. The first width of the first region AR1, the diameter of the second region AR2-1, and the second width of the second region AR2-2 are designed accordingly according to the specifications of the illumination light receiving device D, etc. The above-mentioned second regions AR2-1 and AR2-2 are formed of a suitable material (such as an adhesive or glass, etc.) that does not have the function of changing polarization. For example, the wave plate WP is made in the following way: a phase difference film of half wavelength λ / 2 is processed into a circular ring as the first region AR1, and adhesive layers as the second regions AR2-1 and AR2-2 are formed inside and outside it. The second region AR2-1 can be an air layer formed of air. Or, for example, the wave plate WP is made in the following way: a phase difference film of half wavelength λ / 2 is processed into a circular ring as the first region AR1, and it is pasted on a circular glass substrate. Such a wave plate WP is, for example, as Figure 2 As shown in FIG. B, after light of the Y polarization component is incident as the incident light, a phase difference of half wavelength λ / 2 is generated in the first region AR1, so that light of the Z polarization component is emitted as the emitted light, and in the second region AR2-1, no such phase difference is generated and light of the Y polarization component is directly emitted as the emitted light.

[0027] In Figure 2 In the example shown in FIG. A, the wave plate is the wave plate WP having the second region AR2 formed in the central part and the first region AR1 formed in its outer periphery. However, as Figure 2 shown in FIG. C, it can also be a wave plate WPa having the first region AR1 formed in the central part and the second region AR2 formed in its outer periphery. In Figure 2 the wave plate Wpa shown in FIG. C, although not shown, a second first region can also be formed in the outer periphery of the second region AR2. In addition, in Figure 2In the wavelength plate WP shown in A, although not shown, a second first region may be formed on the outer periphery of the second region AR2-2. In the above examples, the number of first regions AR1 that generate a phase difference of half wavelength λ / 2 is one or two, but it can be any number, and it is designed accordingly according to the specifications of the illumination light receiving device D and the like. Similarly, in the above examples, the number of second regions AR2 that do not cause polarization change is one or two, but it can be any number, and it is designed accordingly according to the specifications of the illumination light receiving device D and the like.

[0028] The first optical system Gr21 is an objective lens that irradiates incident light onto the object WK disposed on the placement surface. The first optical system Gr21 will be further described later.

[0029] The polarization selection optical device PS is a polarizer that selectively extracts a polarization component in a specific direction from the incident light and emits it as the output light. For example, the polarization selection optical device PS selectively extracts the following polarization component: after passing through the second region AR2, being reflected by the object WK, and then passing through the first region AR1 to generate a phase difference of half wavelength λ / 2, and the polarization selection optical device PS emits this polarization component as the output light. More specifically, the polarization selection optical device PS only allows the Z polarization component to pass through and emits the Z polarization component as the output light, and blocks other polarization components.

[0030] The light receiving device IS is a device that receives light through a specified light receiving surface and outputs an electrical signal corresponding to the incident light based on photoelectric conversion. For example, it is configured to include a photodiode, a PDS (position detection sensor), a line sensor, or a two-dimensional image sensor, etc. In the light receiving device IS, a corresponding type of sensor can be adopted according to the specifications of the illumination light receiving device D and the like.

[0031] The second optical system Gr22 is an optical system for imaging the optical image of the object WK illuminated by the illumination light together with the first optical system Gr21 on the light receiving surface of the light receiving device IS, and it is configured to include one or more lenses.

[0032] The above-described light source LS, the first lens L11 of the optical system Gr11, the polarizer PL, the band-pass filter BPF, and the second lens L12 of the optical system Gr11 are arranged such that their respective optical axes are aligned with the optical axis (the first optical axis) AX1 and are sequentially arranged along the first optical axis AX1. The band-pass filter BPF and the optical system Gr11 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). The light emitted from the light source LS, after being incident on the first lens L11 of the optical system Gr11, is changed to parallel light by the first lens L11 and is incident on the polarizer PL from the first lens L11. Then, it is changed to a polarized component in a specified direction (Y polarized component in the present embodiment) by the polarizer PL and is incident on the band-pass filter BPF from the polarizer PL. Then, it is changed to light within a specified wavelength range by the band-pass filter BPF and is incident on the second lens L12 of the optical system Gr11. Then, it is condensed by the second lens L12 and is emitted from the second lens L12 of the optical system Gr11 as the illumination light of the illumination unit IL.

[0033] In addition, the illumination unit IL may include a laser light source that emits a polarized component in a specified direction as the light source LS, instead of the light source LS and the polarizer PL. Thus, the illumination unit IL can be configured to include the light source LS, the band-pass filter BPF, and the optical system Gr11.

[0034] The illumination unit IL having the above-described light source LS, polarizer PL, band-pass filter BPF, and optical system Gr11 is arranged with respect to the beam splitter BS such that the first optical axis AX1 intersects the inclined surface of the beam splitter BS at 45°. Preferably, the intersection point of the first optical axis AX1 on the inclined surface of the beam splitter BS is the central position of the inclined surface (for example, the intersection position of the two diagonals in the case where the inclined surface is rectangular). Therefore, the illumination light emitted from the illumination unit IL propagates (travels) along the first optical axis AX1 and is incident on the beam splitter BS, and the propagation direction (travel direction) is bent by 90° on the inclined surface. That is, the first optical axis AX1 on the light source LS, polarizer PL, band-pass filter BPF, and optical system Gr11 is bent by 90°. The illumination light is reflected on the inclined surface and is changed to illumination light with a polarized component in a specified direction (Y polarized component), and then propagates along the first optical axis AX1 bent by 90° by the inclined surface.

[0035] The wavelength plate WP is arranged on one side of the first position where the light source LS is arranged with respect to the object WK, and is arranged on one side of the second position where the light receiving device IS is arranged with respect to the object WK. More specifically, Figure 1In the example shown, the wavelength plate WP is disposed on the emission side where the illumination light (the illumination light of the polarization component in the specified direction) reflected by the inclined surface in the beam splitter BS is emitted and on the image side of the first optical system Gr21 (the light receiving device IS side). The illumination light of the polarization component in the specified direction emitted from the beam splitter BS, after being incident on the wavelength plate WP, generates a phase difference of half wavelength λ / 2 in the first region AR1 and is changed to a polarization component orthogonal to the specified direction (Z polarization component in the above example) and is emitted. Then, in the second region AR2-1, no such phase difference is generated and it is directly emitted as the polarization component in the specified direction (Y polarization component in the above example).

[0036] The first optical system Gr21 is disposed on one side of the fourth position where the object WK is disposed with respect to the third position where the wavelength plate WP is disposed. The illumination light of each polarization component emitted from the wavelength plate WP, after being incident on the first optical system Gr21, illuminates the object WK. The reflected light (first reflected light) of the object WK, after being incident on the first optical system Gr21, is incident on the wavelength plate WP via the first optical system Gr21. Then, a phase difference of half wavelength λ / 2 is generated in the first region AR1 and it is emitted. Then, in the second region AR2-1, no such phase difference is generated and it is directly emitted. Therefore, if the first reflected light of the illumination light incident on the first region AR1 is incident on the first region AR1, the first reflected light is changed to the same polarization component as the polarization component of the illumination light incident on the first region AR1 (Y polarization component in the above example) and is emitted from the wavelength plate WP. If the first reflected light of the illumination light incident on the first region AR1 is incident on the second region AR2-1, the first reflected light is changed to a polarization component orthogonal to the polarization component of the illumination light incident on the first region AR1 (Z polarization component in the above example) and is emitted from the wavelength plate WP. If the first reflected light of the illumination light incident on the second region AR2-1 is incident on the second region AR2-1, since no such phase difference is generated even once (once), the first reflected light is emitted from the wavelength plate WP as the same polarization component as the polarization component of the illumination light incident on the first region AR1 (Y polarization component in the above example). The first reflected light of the illumination light transmitted through the wavelength plate WP, after being incident on the beam splitter BS, only the transmitted component divided by the specified division ratio is emitted.

[0037] The polarization selection optical device PS is disposed on a position on one side of the second position where the light receiving device IS is disposed with respect to the first position where the light source LS is disposed with respect to the wavelength plate WP. More specifically, in Figure 1In the example shown, the polarization-selective optical device PS is arranged on the emission side where the first reflected light of the illumination light transmitted through the inclined surface in the beam splitter BS is emitted and on the object side (the object WK side) of the second optical system Gr22. After the first reflected light emitted from the beam splitter BS is incident on the second optical system Gr22, based on the first and second optical systems Gr21 and Gr22, the optical image of the object WK (the optical image of the object WK formed by the first reflected light of the polarization component orthogonal to the specified direction) is formed on the light-receiving surface of the light-receiving device IS. The light-receiving device IS performs photoelectric conversion and outputs an electrical signal corresponding to the optical image of the object WK received by the light-receiving surface. The electrical signal output from the light-receiving device IS is output to the corresponding device (such as an information processing device such as a computer, etc.) that processes the electrical signal.

[0038] In the present embodiment, the first optical system Gr21, the wavelength plate WP, the beam splitter BS, the polarization-selective optical device PS, the second optical system Gr22, and the light-receiving device IS are arranged such that their respective optical axes are aligned with the optical axis (the second optical axis) AX2 and are sequentially arranged in order from the object side to the image side along the second optical axis AX2. The first optical system Gr21 and the second optical system Gr22 constitute an imaging optical system for forming the 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 at the inclined surface of the beam splitter BS, and the first optical axis AX1 of the illumination optical system is bent by 90° at the inclined surface of the beam splitter BS. Therefore, 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 LS can be regarded 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.

[0039] Here, in the present embodiment, the first optical system Gr21 includes one or more lenses formed with a curvature radius (= 1 / curvature) of an air interface that is a boundary with air and causes the reflected light (the second reflected light) based on this air interface to be imaged at a position shifted from the imaging position of the imaging optical system. More specifically, the first optical system Gr21 includes one or more lenses formed with a curvature radius smaller than that of an air interface that causes the second reflected light based on this air interface to be imaged at the imaging position of the imaging optical system at the wavelength of the illumination light. More specifically, for example, the first optical system Gr21 is as Figure 3is configured to include one or more lenses formed with a radius of curvature of an air interface that, at the wavelength of the illumination light, places a virtual image of the second reflected light based on the air interface between the object WK and the first optical system Gr21. In Figure 3 the example shown, the air interface of the first optical system Gr21 has two surfaces. In other words, the first optical system Gr21 is configured to include one lens. In the one lens, as Figure 1 shown, a cemented lens is included that is formed by cementing together two lenses, the first and second lenses L21 and L22.

[0040] Figure 3 is a diagram for explaining the operation and effect of the illumination light receiving device. Figure 4 is a diagram for explaining a comparative example.

[0041] Figure 4 The illumination light receiving device D' of the comparative example shown, in addition to including a first optical system Gr21' that includes one lens' having a relatively large radius of curvature of the air interface, in order to replace the first optical system Gr21, has the same configuration as the illumination light receiving device D in the above-described embodiment. In such a comparative example illumination light receiving device D', at the wavelength of the illumination light, a virtual image of the image-side air interface SF2' in the lens of the first optical system Gr21' is formed at a position P1' outside the object WK (on the side farther from the first optical system Gr21' than the object WK). At the light receiving surface of the light receiving device IS, the imaging position of the imaging optical system including the first optical system Gr21' and the second optical system Gr22 and the imaging position of the second reflected light based on the air interface SF2' become closer. Therefore, in the illumination light receiving device D' of this comparative example, a relatively bright region (hot spot) of the second reflected light based on the air interface SF2' is generated on the light receiving surface of the light receiving device IS, resulting in noise. As a result, the signal-to-noise ratio of the light receiving device IS decreases.

[0042] On the other hand, in the illumination light receiving device D of the present embodiment, the first optical system Gr21 includes one or more lenses formed with a radius of curvature of an air interface that, at the wavelength of the illumination light, places a virtual image of the second reflected light based on the air interface between the object WK and the first optical system Gr21. In Figure 3In the example shown, the first optical system Gr21 includes: one lens formed with a radius of curvature of an air interface SF2 on the image side such that, at the wavelength of the illumination light, a virtual image of the second reflected light based on the air interface SF2 on the image side is located between the object WK and the first optical system Gr21. In such an illumination light receiving device D, at the wavelength of the illumination light, a virtual image of the air interface SF2 on the image side in the lens of the first optical system Gr21 is formed at a position P1 between the object WK and the first optical system Gr21, and at the light receiving surface of the light receiving device IS, the imaging position of the second reflected light based on the air interface SF2 becomes a position P2 outside the light receiving surface of the light receiving device IS (on the side farther from the first optical system Gr21 than the light receiving surface of the light receiving device IS). Therefore, in the illumination light receiving device D of the embodiment, the second reflected light based on the air interface SF2 is out of focus and blurred at the light receiving surface of the light receiving device IS, and the hot spot is reduced. As a result, the signal-to-noise ratio in the light receiving device IS can be improved.

[0043] In addition, as can be seen from the above, an optical system located on the object side with respect to the polarization selection optical device PS has a great influence on the generation of the hot spot; an optical system located on the image side with respect to the polarization selection optical device PS has almost no influence on the generation of the hot spot. In the present embodiment, the first optical system Gr21 has a great influence on the generation of the hot spot, and the second optical system Gr22 has almost no influence on the generation of the hot spot.

[0044] In addition, in the present embodiment, the above-described band-pass filter BPF and the optical system Gr11 are an example of an illumination optical system that uses the light emitted from the light source as illumination light and illuminates a specified object. The first optical system Gr21 and the second optical system Gr22 are an example of an imaging optical system that images the optical image of the object on the light receiving surface of the light receiving device.

[0045] As described above, the illumination light receiving device D in the present embodiment does not need to use the specific polarization element and instead uses the wavelength plate WP having the first region AR1 and the second region AR2. Therefore, the reflected light generated in the specific polarization element is not generated, and the signal-to-noise ratio in the light receiving device IS can be improved.

[0046] Since the first optical system Gr21 includes one or more lenses formed with a radius of curvature of an air interface that images the second reflected light based on the air interface at a position offset from the imaging position of the imaging optical system, the second reflected light does not image on the light receiving surface of the light receiving device IS. Therefore, the above-described illumination light receiving device D can improve the signal-to-noise ratio in the light receiving device IS.

[0047] In the case where the illumination light receiving device D has two air interfaces of the first optical system Gr21, since the number of the air interfaces of the first optical system Gr21 is the minimum, the second reflected light based on the air interface can be minimized, and the signal-to-noise ratio in the light receiving device IS can be improved. Since the optical power is concentrated on the two air interfaces, it is easy to reduce the radius of curvature of the air interface and easy to increase the blur of the second reflected light on the light receiving surface.

[0048] The above-described illumination light receiving device D includes first and second optical systems Gr21 and Gr22. The second reflected light is blurred on the light receiving surface of the light receiving device IS by the first optical system Gr21. On the other hand, the light image of the object WK is imaged on the light receiving surface of the light receiving device IS by eliminating the aberration of the first and second optical systems Gr21 and Gr22 through the first and second optical systems Gr21 and Gr22. Therefore, the signal-to-noise ratio in the light receiving device IS can be improved.

[0049] In addition, in the above-described embodiment, if the magnification of the imaging optical system is 0.5 times or less, a more significant improvement effect is obtained. For example, when the magnification is 1 time, the irradiance is 1 [W / mm 2 , the object WK is a perfect diffuser with a reflectance of 100 [%], and the effective F-number of the imaging optical system is 2.0 (i.e., the numerical aperture NA = 0.25), the energy that the imaging optical system can capture is 0.25 2= 0.0625, only about 6 [%] of the first reflected light (the optical image of the object WK) of the object WK reaches the light-receiving surface of the light-receiving device IS. Further, if the magnification is changed to a low magnification (e.g., 0.5 times), the irradiance decreases in proportion to the square of the magnification. Therefore, only about 2 [%] of the first reflected light (the optical image of the object WK) of the object WK reaches the light-receiving surface of the light-receiving device IS. Assuming that the stray light generated by the first optical system Gr21 and the wavelength plate WP is 1 [%], this is equivalent to half of the above-mentioned about 2 [%], resulting in a significant decrease in the SN ratio in the light-receiving device IS. In the case of the above-described embodiment, since the stray light component can be reduced, the SN ratio can be improved. In particular, if the magnification is 0.5 times or less, a more significant improvement effect is obtained.

[0050] Further, in the above-described embodiment, it is preferable that the second optical system Gr22 includes a plurality of lenses so as to have four or more air interfaces. Figure 5 This is a diagram for explaining a modified embodiment of the illumination light-receiving device. For example, as Figure 5 shown, the second optical system Gr22 includes two lenses L24 and L25 and has four air interfaces. Since such an illumination light-receiving device D has a large number of air interfaces, it is easy to perform aberration correction and the like, and it is easy to improve the resolution. Therefore, the optical performance of the illumination light-receiving device D can be improved.

[0051] Further, in the above-described embodiment, the second optical system Gr22 may be a zoom optical system with a variable focal length. Alternatively, the second optical system Gr22 may be any one of a plurality of imaging optical systems prepared in advance with different focal lengths. Since such an illumination light-receiving device D can change the magnification by the second optical system Gr22, on the one hand, the effect of blurring the second reflected light on the light-receiving surface of the light-receiving device IS can be maintained by the first optical system Gr21, and on the other hand, light can be received in a zoom manner.

[0052] Further, the illumination light-receiving device D in the above-described embodiment can be variously applied. For example, as disclosed in the above-mentioned Patent Document 1, it can be applied to surface observation or defect observation in a block. In the surface observation, the above-described illumination light-receiving device D can be applied to measurement of inclination or curvature, measurement of contamination such as defects or particles, measurement of minute level differences formed by micro-patterns, and measurement of roughness, etc. In the defect observation in the block, the above-described illumination light-receiving device D can be applied to observation of bubbles in glass and detection of refractive index inhomogeneous portions due to strain, etc.

[0053] As an example, the measurement of the inclination of the object WK will be described. Figure 6This is a diagram for explaining an example in which the illumination light receiving device is applied to an inclination measuring device. In Figure 6 it, a polarization selection optical device PS, a beam splitter BS, a wavelength plate WP, a first optical system Gr21, and an object WK are illustrated, and the illustration of the remaining components is omitted.

[0054] In Figure 6In the case where the object WK is a plate-like body having flat front and back surfaces, as shown by the solid line, the object WK is horizontally disposed on the placement surface. If not tilted, the illumination light of the Y polarization component and the reflected light of the illumination light reflected by the object WK cannot transmit through the polarization selection optical device PS, and thus do not reach the light receiving device IS, so that the light receiving surface of the light receiving device IS does not receive light. On the other hand, as shown by the dashed line, if the object WK is tilted, a part of the illumination light of the Y polarization component and the reflected light of the illumination light reflected by the object WK becomes the Z polarization component and transmits through the polarization selection optical device PS and reaches the light receiving device IS. Therefore, the light receiving surface of the light receiving device IS receives light. For example, the illumination light LB1 emitted from the illumination unit IL is reflected by the beam splitter BS, transmits through the second region AR2-1 of the wavelength plate WP, and is incident on the tilted object WK via the first optical system Gr21 and is reflected. The first reflected light of the illumination light LB1 is incident on the first region AR1 of the wavelength plate WP via the first optical system Gr21, generates a phase difference of half wavelength λ / 2 and becomes the Z polarization component and is incident on the beam splitter BS from the wavelength plate WP. The first reflected light of the Z polarization component transmits through the beam splitter BS and is incident on the polarization selection optical device PS. Since the polarization selection optical device PS is set to transmit the Z polarization component, it transmits through the polarization selection optical device PS and reaches the light receiving surface of the light receiving device IS via the second optical system Gr22. For example, the illumination light LB2 emitted from the illumination unit IL is reflected by the beam splitter BS, is incident on the first region AR1 of the wavelength plate WP, generates a phase difference of half wavelength λ / 2 and becomes the Z polarization component and is incident on the tilted object WK from the wavelength plate WP via the first optical system Gr21 and is reflected. The first reflected light of the illumination light LB2 is incident on the second region AR2-1 of the wavelength plate WP via the first optical system Gr21 and is incident on the beam splitter BS from the wavelength plate WP. The first reflected light of the Z polarization component transmits through the beam splitter BS and is incident on the polarization selection optical device SP, and transmits through the polarization selection optical device SP and reaches the light receiving surface of the light receiving device IS via the second optical system Gr22. If the object WK is tilted in this way, a part of the Z polarization component of the first reflected light reaches the light receiving surface of the light receiving device IS, and an electric signal corresponding to the Z polarization component is output from the light receiving device IS. By detecting this electric signal by using the information processing device or the like, the tilt of the object WK can be detected. By previously correlating the magnitude of the electric signal with the tilt angle, the tilt angle of the object WK can be measured.

[0055] This specification discloses the technologies of various embodiments as described above, and the main technical summaries are as follows.

[0056] One of the technical solutions involves a lighting light receiving device, which includes: a wavelength plate having one or more first regions and one or more second regions, where the first regions generate a phase difference of half a wavelength and the second regions do not have the function of changing polarization; a polarization selection optical device that selectively extracts and emits polarization components in a specific direction; a light receiving device that receives light on a specified light receiving surface; a light source that emits light; an illumination optical system that illuminates a specified object with the light emitted from the light source as illumination light; and an imaging optical system that forms an optical image of the object on the light receiving surface of the light receiving device. Among them, the first regions and the second regions in the wavelength plate are formed in a concentric circle with each other, and at least one first boundary in the first regions and a second boundary of the second regions are shared. The wavelength plate is arranged on one side of the first position where the light source is arranged with respect to the object and on one side of the second position where the light receiving device is arranged with respect to the object. The polarization selection optical device is arranged at a position on one side of the second position compared to the first position with respect to the wavelength plate. The first optical axis of the illumination optical system and the second optical axis of the imaging optical system are coaxial with each other.

[0057] This lighting light receiving device does not need to use the specific polarization element, and adopts a wavelength plate with the first regions and the second regions, which can replace the specific polarization element. Therefore, the reflected light generated in the specific polarization element will not be produced, and thus the signal-to-noise ratio in the light receiving device can be improved.

[0058] As another technical solution, in the above lighting light receiving device, the magnification of the imaging optical system is 0.5 times or less.

[0059] Since this lighting light receiving device adopts an imaging optical system with a magnification of 0.5 times or less, the signal-to-noise ratio in the light receiving device can be improved well.

[0060] As another technical solution, in these above lighting light receiving devices, the imaging optical system includes a first optical system, and the first optical system is arranged on one side of the fourth position where the object is arranged with respect to the third position where the wavelength plate is arranged. The first optical system includes: one or more lenses formed with a curvature radius of an air interface, which is a boundary with air and makes the reflected light based on this air interface image at a position offset from the imaging position of the imaging optical system. Preferably: in the above lighting light receiving device, the first optical system includes: one or more lenses formed with a curvature radius of an air interface, which makes the virtual image of the reflected light based on this air interface located between the object and the first optical system.

[0061] Since the first optical system of the illumination light receiving device includes one or more lenses formed with a radius of curvature of an air interface that images the reflected light based on the air interface at a position offset from the imaging position with respect to the imaging optical system, the reflected light is not imaged on the light receiving surface of the light receiving device, thereby improving the signal-to-noise ratio in the light receiving device.

[0062] As another technical solution, in the above illumination light receiving device, there are two air interfaces of the first optical system. Preferably: in the above illumination light receiving device, the first optical system includes one lens (including a cemented lens) formed with a radius of curvature of an air interface on the image side, and the virtual image of the reflected light based on the air interface on the image side is located between the object and the first optical system at the wavelength of the illumination light.

[0063] Since the number of the air interfaces of the first optical system is minimized in the illumination light receiving device, the reflected light based on the air interface can be minimized, thereby improving the signal-to-noise ratio in the light receiving device.

[0064] As another technical solution, in the above illumination light receiving device, the imaging optical system includes a second optical system, the second optical system is disposed on one side of the second position with respect to the third position, and the imaging optical system uses the first and second optical systems to image the optical image of the object on the light receiving surface of the light receiving device. Preferably: in the above illumination light receiving device, the second optical system includes a plurality of lenses so as to have more than four air interfaces.

[0065] The illumination light receiving device includes the first and second optical systems, and the reflected light is blurred on the light receiving surface of the light receiving device by the first optical system. On the other hand, the optical image of the object is imaged on the light receiving surface of the light receiving device by the first and second optical systems while eliminating the aberration of the first and second optical systems, thereby improving the signal-to-noise ratio in the light receiving device.

[0066] As another technical solution, in the above illumination light receiving device, the imaging optical system includes a second optical system, the second optical system is disposed on one side of the second position with respect to the third position, and the second optical system is a zoom optical system with a variable focal length or any one of a plurality of imaging optical systems with different focal lengths prepared in advance.

[0067] Since the illumination light receiving device includes the first and second optical systems and the magnification can be changed by the second optical system, the effect of blurring the reflected light on the light receiving surface of the light receiving device can be maintained by the first optical system. On the other hand, light can be received by changing the magnification.

[0068] This application is based on Japanese Patent Application No. 2022-189415 filed on November 28, 2022, the content of which is incorporated herein.

[0069] To describe the present invention, the present invention has been appropriately and fully described above with reference to the drawings and through embodiments. However, it should be recognized that those skilled in the art can easily make changes and / or improvements to the above embodiments. Therefore, as long as the changed or improved embodiments implemented by those skilled in the art do not exceed the scope of protection of the claims recited in the claims, the changed or improved embodiments can be interpreted as being included within the scope of protection of the claims.

[0070] Industrial Applicability

[0071] According to the present invention, it is possible to provide an illumination light receiving device that illuminates a specified object and receives the reflected light thereof.

Claims

1. A lighting light receiving device, characterized in that Comprising: A wavelength plate having one or more first regions and one or more second regions, wherein the first regions generate a phase difference of half a wavelength and the second regions do not have a function of changing polarization; A polarization-selective optical device that selectively extracts and emits polarization components in a specific direction; An optical receiving device that receives light on a specified light-receiving surface; A light source that emits light; An illumination optical system that illuminates a specified object with the light emitted from the light source as illumination light; and An imaging optical system that forms an optical image of the object on the light-receiving surface of the optical receiving device; wherein the first regions and the second regions in the wavelength plate are formed in a concentric circle pattern with respect to each other, and at least one first boundary in the first regions and a second boundary of the second regions are shared; the wavelength plate is disposed on one side of the first position where the light source is disposed with respect to the object and on one side of the second position where the optical receiving device is disposed with respect to the object; the polarization-selective optical device is disposed on a position on one side of the second position with respect to the first position with respect to the wavelength plate; a first optical axis of the illumination optical system and a second optical axis of the imaging optical system are coaxial with each other.

2. The illumination light receiving device according to claim 1, wherein the magnification of the imaging optical system is 0.5 times or less.

3. The illumination light receiving device according to claim 1 or 2, wherein the imaging optical system includes a first optical system, and the first optical system is disposed on one side of the fourth position where the object is disposed with respect to the third position where the wavelength plate is disposed; the first optical system includes: one or more lenses formed with a curvature radius of an air interface that is a boundary with air and causes reflected light based on the air interface to be imaged at a position shifted from the imaging position with respect to the imaging optical system.

4. The illumination light receiving device according to claim 3, wherein the air interface of the first optical system is two.

5. The illumination light receiving device according to claim 3, wherein the imaging optical system includes a second optical system, and the second optical system is disposed on one side of the second position with respect to the third position; the imaging optical system forms an optical image of the object on the light-receiving surface of the optical receiving device using the first and second optical systems.

6. The illumination light receiving device according to claim 3, wherein the imaging optical system includes a second optical system, and the second optical system is disposed on one side of the second position with respect to the third position; the second optical system is a variable magnification optical system with a variable focal length or any one of a plurality of imaging optical systems with different pre-prepared focal lengths.

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