Optical device and inspection method

Abstract

This optical device inspects a surface to be inspected, the surface having a riblet structure in which a plurality of convex sections lying in a first direction are provided in a second direction intersecting the first direction. The optical device comprises: a condensing optical system for projecting light from a light source onto an irradiation region on the surface to be inspected and condensing light reflected by the irradiation region; a light-receiving element for detecting the light condensed by the condensing optical system; and a light amount-modifying member capable of modifying a ratio between a light amount of first reflected light which is reflected by a section of the irradiation region where the convex sections are not provided and which is oriented toward the light-receiving element, and a light amount of second reflected light which is reflected by the convex sections in the irradiation region and oriented toward the light-receiving element.

Description

Optical device and inspection method

[0001] The present disclosure relates to an optical apparatus and inspection method used to inspect object surfaces having riblet structures.

[0002] Conventionally, the configuration of an inspection device for inspecting the quality of a microstructure has been proposed (see, for example, Patent Document 1).

[0003] U.S. Patent No. 8,842,271

[0004] The optical device disclosed herein is an optical device for inspecting a surface to be inspected that has a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction that intersects the first direction, and is equipped with a focusing optical system that irradiates light from a light source onto an irradiation area on the surface to be inspected and collects the light reflected by the irradiation area, a light receiving element that detects the light collected by the focusing optical system, and a light amount changing member that can change the ratio between the amount of first reflected light that is reflected by a portion of the irradiation area where no convex portions are provided and heads toward the light receiving element, and the amount of second reflected light that is reflected by the convex portions in the irradiation area and heads toward the light receiving element.

[0005] The inspection method disclosed herein is an inspection method for inspecting a surface to be inspected that has a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction that intersects the first direction, and includes irradiating light onto an irradiation area on the surface to be inspected, collecting light reflected from the irradiation area by the light irradiation using a focusing optical system, changing the ratio between the amount of first reflected light reflected from a portion of the irradiation area that does not have convex portions and the amount of second reflected light reflected from the convex portions in the irradiation area, detecting the light collected by the focusing optical system, and inspecting the riblet structure based on the detection results.

[0006] 1 is a schematic diagram explaining irradiation of light onto an object surface having a riblet structure; FIG. 2 is a diagram explaining a riblet structure; FIG. 3 is a diagram explaining reflection of light on an object surface having a riblet structure; FIG. 4 is a schematic diagram showing the configuration of an optical device; FIG. 5 is a schematic diagram explaining light collection by an optical element arranged closest to the object surface in a collecting optical system; FIG. 6 is a diagram showing a projection relationship in a collecting optical system; FIG. 7 is a schematic diagram showing first light reception data; FIG. 8 is a schematic diagram showing the general configuration of a computer; FIG. 9 is a functional block diagram of a processor possessed by the computer; FIG. 10 is a diagram showing the ratio of the light intensity of the first reflected light to the second reflected light in the first light reception data; FIG. 11 is a schematic diagram showing second light reception data; FIG. 12 is a flowchart of an inspection process for a riblet structure; FIG. 13 is a flowchart of a measurement process for a riblet structure; FIG. 14 is a schematic diagram showing the configuration of an optical device according to a modified example.

[0007] The optical device and inspection method of the present application will be described in detail below with reference to the drawings.

[0008] FIG. 1 is a schematic diagram illustrating an outline of light irradiation onto an object surface having a riblet structure, and FIG. 2 is a diagram illustrating the riblet structure.

[0009] In this embodiment, the optical device 1 is located at a predetermined distance from an object surface OS on which a riblet structure is formed, and inspects the object surface OS by irradiating light onto an irradiation area IR on the object surface OS. For ease of explanation, the following description will be directed to a case in which the optical device 1 is used to inspect a riblet structure (object surface OS). However, the optical device 1 can also be applied to measuring a riblet structure (object surface OS). For the sake of explanation, FIG. 1 shows a state in which the optical device 1 is positioned at a predetermined distance from the object surface OS. The object surface OS may be an envelope surface including the ridgelines of multiple riblets, or may be the surface of an object before the riblet structure is formed. The object surface OS may also be referred to as a workpiece surface.

[0010] Forming a riblet structure on the object surface OS can reduce the frictional resistance between the object surface OS and a fluid in contact with the object surface OS. However, if the shape of the riblet structure changes, the effect of reducing the frictional resistance between the object surface OS and the fluid may decrease. Therefore, there is a need for an optical device that can easily inspect the shape of the riblet structure on the object surface OS. At least a portion of the object surface OS can be considered to be the surface to be inspected. Note that at least a portion of the riblet structure formed on the object surface OS can also be considered to be the surface to be inspected. Note that the fluid in contact with the object surface OS may be a gas or a liquid.

[0011] The object surface OS has a plurality of convex portions C in the second direction D2, which protrude convexly toward the outside of the object and are continuous in the first direction D1. The second direction D2 is a direction that intersects with the first direction D1, for example, a direction perpendicular to the first direction D1 along the object surface OS. No convex portions C are provided in region R of the object surface OS. Region R can also be said to be a region on the object surface OS between adjacent convex portions C that are spaced apart in the second direction D2. The riblet structure can also be said to be a structure including convex portions C and region R. Note that the riblet structure can also be said to be a structure consisting only of convex portions C. Note that adjacent convex portions C along the second direction D2 may be adjacent to each other. In other words, region R may not be required.

[0012] The riblet structure (object surface OS) may be formed by removing portions other than the convex portions C from the surface of a workpiece (e.g., metal), for example, by laser processing. Alternatively, the riblet structure (object surface OS) may be formed by fixing (e.g., adhering) a resin film (e.g., UV-curable resin) on which the riblet structure is formed to the surface of the workpiece. The riblet structure may be formed by applying a curable material (e.g., UV-curable resin) to the surface of the workpiece and pressing a mold having a shape corresponding to the riblet structure against a material layer on the workpiece. While FIG. 1 shows an example of an object surface OS on which a riblet structure is formed on a flat workpiece surface, the surface of the workpiece may also be curved. When forming a riblet structure by pressing a mold against a material layer on the workpiece, the optical device 1 may be used to inspect and / or measure the mold pressed against the material layer (e.g., the shape of the side of the mold pressing against the material layer).

[0013] The convex portion C has a pair of inclined surfaces T1 and T2 (hereinafter collectively referred to as "inclined surfaces T") inclined with respect to the third direction D3. The third direction D3 is a direction perpendicular to the first direction D1 and the second direction D2, e.g., a normal direction to the object surface OS. Here, in design, the inclined surfaces T1 and T2 are symmetrical with respect to the third direction D3. That is, the angle between one inclined surface T1 and the region R and the angle between the other inclined surface T2 and the region R are equal in design. Note that the inclined surfaces T1 and T2 in design can also be said to be symmetrical with respect to the third direction D3. Note that the inclined surfaces T1 and T2 in design may be asymmetric with respect to the third direction D3. Note that the third direction D3 may be a direction intersecting the first direction D1 and the second direction D2.

[0014] The spacing P between the multiple convex portions C provided in the second direction D2 may be, for example, 100 μm. The size (height H) of the convex portions C in the third direction D3 may be, for example, 50 μm. The pair of inclined surfaces T1, T2 may be inclined at, for example, ±22.5° with respect to the third direction D3, and the apex angle A of the convex portions C may be, for example, 45°. Note that the spacing P between the convex portions C, the size (height H) of the convex portions C in the third direction D3, the inclination angles of the inclined surfaces T1, T2 with respect to the third direction D3, and the apex angle A of the convex portions C are not limited to the above values.

[0015] Surfaces of objects on which such riblet structures are formed are described, for example, in U.S. Pat. No. 8,444,092, U.S. Pat. No. 9,656,743, U.S. Pat. No. 8,876,052, U.S. Pat. No. 9,751,618, U.S. Pat. No. 10,877,377, U.S. Patent Application Publication No. 2013 / 0146217, U.S. Patent Application Publication No. 2016 / 0271930, U.S. Patent Application Publication No. 2020 / 0263704, and U.S. Patent Application Publication No. 2021 / 0054859.

[0016] FIG. 3 is a diagram illustrating the reflection of light on an object surface OS.

[0017] The incident light beams IL1, IL2-1, and IL2-2, which are incident parallel to the normal direction of the object surface OS, illuminate an illumination area IR on the object surface OS and are reflected by the illumination area IR.

[0018] The first reflected light RL1 is the incident light IL1 reflected once by the region R of the object surface OS. In the example of Fig. 3, the first reflection direction in which the first reflected light RL1 is reflected from the irradiation region IR is a direction perpendicular to the region R of the object surface OS. Note that the first reflected light RL1 may include reflected light that is incident on the irradiation region IR at a position different from that of the incident light IL1 and is reflected once by the region R.

[0019] The second reflected light RL2-1, RL2-2 (hereinafter collectively referred to as "second reflected light RL2") are incident light IL2-1, IL2-2, which are incident at different positions on the irradiation region IR, reflected at least once by the region R and the convex portion C.

[0020] For example, the second reflected light RL2-1 is incident light IL2-1 reflected at least once by each of region R and inclined surface T1 of convex portion C, i.e., at least twice or more in the irradiation region IR. The second reflected light RL2-2 is incident light IL2-2, which has entered a position different from that of incident light IL2-1, reflected at least once by each of region R and inclined surface T2 of convex portion C, i.e., at least twice or more in the irradiation region IR.

[0021] The reflection direction of the second reflected light RL2-1 reflected by the inclined surface T1 of the convex portion C having the apex angle A and the region R (hereinafter also referred to as the "second reflection direction") is a direction inclined from the normal direction of the region R of the object surface OS by the same angle as the apex angle A. Note that the apex angle A may be an angle different from the design apex angle of the riblet structure. In other words, the second reflection direction may be a direction inclined from the normal direction of the region R by an angle different from the design apex angle.

[0022] The reflection direction of the second reflected light RL2-2 reflected by the inclined surface T2 of the convex portion C having an apex angle A and the region R (hereinafter also referred to as the "third reflection direction") is a direction inclined by the same angle as the apex angle A in the direction opposite to the second reflection direction with respect to the normal direction of the region R of the object surface OS. Note that the apex angle A may be an angle different from the design apex angle of the riblet structure. In other words, the third reflection direction may be a direction inclined by an angle different from the design apex angle in the direction opposite to the second reflection direction with respect to the normal direction of the region R.

[0023] The second reflected light RL2-1, RL2-2 may be reflected light that has been reflected three or more times in total by the region R and the convex portion C, for example, reflected once by the region R and twice by the convex portion C. Note that the second reflected light RL2 may include, in addition to the second reflected light RL2-1, RL2-2, reflected light that has been incident on the irradiation region IR at a position different from that of the incident light IL2-1 and IL2-2 and has been reflected at least two or more times by the irradiation region IR.

[0024] The convex portion C may have a height H (for example, 50 μm), and the pair of inclined surfaces T1 and T2 may form an apex angle A (for example, 45°).

[0025] FIG. 4 is a schematic diagram showing the configuration of the optical device 1. The optical device 1 includes a focusing optical system 2 and a light receiving element 3 housed in a housing 4, and is electrically connected to a computer 5. The connection between the optical device 1 and the computer 5 may be wired or wireless. The optical device 1 irradiates light from a light source LS onto an object surface OS and detects reflected light from the object surface OS. FIG. 4 shows a cross section of the focusing optical system 2, the light receiving element 3, the housing 4, and the object surface OS taken along a plane including the optical axis AX of the focusing optical system 2. The optical device 1 may also include a computer 5.

[0026] The light source LS supplies light to the optical device 1. The light source LS includes, as a light-emitting element, an LED (Light Emitting Diode) that emits incoherent light and / or a laser diode that emits coherent light. The light emitted by the light source LS is guided to the light-collecting optical system 2 via a light-transmitting optical system including, for example, an optical fiber. For example, by using an LED with a short coherence length as the light source LS, interference (speckle) of light returned from the surface of an optical member (e.g., the surface of a lens member) that constitutes the light-collecting optical system 2 is suppressed. The light source LS may be an SLD (Super Luminescent Diode). The light source LS may also be mounted on the optical device 1.

[0027] The light collecting optical system 2 irradiates the light from the light source LS onto an irradiation area IR on the object surface OS, and collects the light reflected by the irradiation area IR.

[0028] The light irradiated onto the irradiation region IR by the focusing optical system 2 may be polarized light. For example, the light source LS may supply light that is linearly polarized in a predetermined direction using a polarizing plate. The optical device 1 may further include a polarizing plate that transmits only the polarized component of the light supplied from the light source LS in a predetermined direction.

[0029] The light-collecting optical system 2 has a lens group 21 having one or more lens members, and a light-splitting member 22 arranged closer to the light-receiving element 3 than the lens group 21. A filter FL for protecting the light-receiving element 3 is arranged between the light-splitting member 22 and the light-receiving element 3.

[0030] The lens group 21 includes, in order from the side closest to the object surface OS, a positive meniscus lens L1 having a convex surface facing the light receiving element 3 and positive power, a positive biconvex lens L2 having positive power, and a positive meniscus lens L3 having a concave surface facing the light receiving element 3 and positive power.

[0031] The positive meniscus lens L1 is the lens element disposed closest to the object surface OS, and has a convex surface facing the light receiving element 3 and a concave surface facing the object surface OS.

[0032] The positive meniscus lens L3 is the lens element disposed closest to the light splitting member 22. The positive meniscus lens L3 has a concave surface facing the light splitting member 22. Since the lens element disposed closest to the light splitting member 22 has a concave surface facing the light splitting member 22, it becomes easy to ensure space for disposing the light splitting member 22.

[0033] Table 1 below lists the specifications of the focusing optical system 2 of this embodiment.

[0034] In Table 1, m is the order of the optical surface counted from the object surface OS side, r is the radius of curvature, d is the surface spacing, and ne is the refractive index for the e-line (wavelength 546 nm). A radius of curvature r=∞ indicates a flat surface.

[0035] The unit of length for the radius of curvature r and the surface spacing d listed in Table 1 is "mm." However, the focusing optical system 2 is not limited to those shown in this table.

[0036] (Table 1) mrdne 0) ∞ 1.60 (Object surface OS) 1) 11.70 12.90 1.839322 (Positive meniscus lens L1) 2) -19.47 0.20 3) 60.85 8.50 1.791918 (Positive lens L2) 4) -60.85 0.20 5) 26.00 7.00 1.839322 (Positive meniscus lens L3) 6) 66.10 3.00 7) ∞ 10.00 1.518251 (Light splitting member 22) 8) ∞ 7.50 9) ∞ 0.70 1.518251 (Filter FL) 10) ∞ 0.75

[0037] As described above, for example, the reflection direction of the second reflected light is a direction inclined by apex angle A with respect to the normal direction of region R. In order to set the lower limit of apex angle A of convex portion C, which is one of the inspection targets of object surface OS (riblet structure), to 45°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be set to sin 45° (0.7) or more so as to be able to properly focus light rays inclined by 45° with respect to the normal direction of region R. Furthermore, in order to set the upper limit of apex angle A of convex portion C, which is one of the inspection targets of object surface OS (riblet structure), to 50°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be set to sin 50° (0.8) or less so as to be able to properly focus light rays inclined by 50° with respect to the normal direction of region R.

[0038] In this case, the numerical aperture on the object surface OS side of the focusing optical system 2 may be determined taking into account a predetermined tolerance. For example, the upper limit of the numerical aperture on the object surface OS side of the focusing optical system 2 may be set to 0.9. The numerical aperture on the object surface OS side of the focusing optical system 2 may be determined according to the upper and lower limits of the apex angle A of the convex portion C to be inspected. In other words, the numerical aperture on the object surface OS side of the focusing optical system 2 may be determined based on the apex angle A of the convex portion C (riblet structure) to be inspected.

[0039] The lower limit of the apex angle A of the convex portion C to be inspected may be 40° or 30°. When the lower limit of the apex angle A of the convex portion C to be inspected is 40°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be equal to or greater than sin 40° (0.6). When the lower limit of the apex angle A of the convex portion C to be inspected is 30°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be equal to or greater than sin 30° (0.5).

[0040] The upper limit of the apex angle A of the convex portion C to be inspected may be 55° or 65°. When the upper limit of the apex angle A of the convex portion C to be inspected is 55°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be equal to or less than sin55° (0.8). When the upper limit of the apex angle A of the convex portion C to be inspected is 65°, the numerical aperture of the focusing optical system 2 on the object surface OS side may be equal to or less than sin65° (0.9).

[0041] Let β be the angle formed between the normal to the end of the effective range of the surface of the optical element closest to the object surface OS in the focusing optical system 2 (e.g., the surface of a lens element closest to the object surface OS) on the object surface OS side and the optical axis AX of the focusing optical system 2. Let γ be the maximum angle formed between the optical axis AX of the focusing optical system 2 and the light rays received by the light receiving element 3 among the light rays incident on the optical element closest to the object surface OS in the focusing optical system 2. Note that γ can also be considered the maximum angle formed between the light rays received by the light receiving element 3 among the light rays incident on the optical element closest to the object surface OS in the focusing optical system 2 and the chief ray of light incident on the object surface OS from the focusing optical system 2.

[0042] In this case, by making γ > β, the focusing optical system 2 suppresses the spread of the light beam of reflected light at the surface of the optical element located closest to the object surface OS in the focusing optical system 2, which is closest to the object surface OS, and can appropriately focus the reflected light onto the light receiving element 3 using a simple optical system.

[0043] FIG. 5 is a schematic diagram illustrating the optical members arranged closest to the object surface OS in the focusing optical system 2. As shown in FIG.

[0044] The positive meniscus lens L1 included in the lens group 21 of the focusing optical system 2 corresponds to the optical element arranged closest to the object surface OS in the focusing optical system 2. The radius of curvature of the lens surface (hereinafter referred to as the first surface) of the positive meniscus lens L1 on the object surface OS side is defined as r, and the diameter of the effective range of the first surface is defined as φ. ｅｆｆ The intersection of the normal to the end of the effective range of the first surface and the optical axis AX of the focusing optical system 2 is defined as the origin (0,0), and the angle formed by the normal to the end of the effective range of the first surface and the optical axis AX of the focusing optical system 2 is defined as β.

[0045] 5 shows a cross section of the positive meniscus lens L1 taken along a plane including the optical axis AX of the focusing optical system 2. Since the first surface is a spherical surface, a point (x, y) on the first surface satisfies the following equation:

[0046]

[0047] Point P at the top end of the effective range of the first surface ｅｆｆ The coordinates of can be expressed as follows:

[0048]

[0049] The distance on the optical axis of the focusing optical system 2 from the object surface OS to the first surface is defined as d, and the diameter of the irradiation area IR is defined as φ ｆｉｅｌｄ The point P at the top end of the irradiation area IR ｆｉｅｌｄ The coordinates of can be expressed as follows:

[0050]

[0051] β is the point P ｅｆｆ and the origin. Also, γ is the slope of the line passing through point P ｅｆｆ and point P ｆｉｅｌｄ Therefore, for the first surface which is a spherical surface, the condition γ>β can be expressed as follows:

[0052]

[0053] FIG. 6 is a diagram showing the projection relationship in the light-collecting optical system 2. As shown in FIG.

[0054] In graph GR1, the horizontal axis θ represents the angle between the light reflected by the irradiation region IR and the optical axis AX of the focusing optical system 2, and the vertical axis y represents the radius of a circle circumscribing the range of light focused on the light receiving element 3 by the focusing optical system 2. Furthermore, f represents the focal length of the focusing optical system 2.

[0055] The light-collecting optical system 2 may satisfy the conditional expression y < f sin θ. By satisfying this conditional expression, the range of light collected on the light-receiving element 3 does not become too large, and the size of the light-receiving element 3 can be reduced. The size of the light-receiving element 3 can be said to be the size of the light-receiving surface of the light-receiving element 3. If the size of the light-receiving surface of the light-receiving element 3 is reduced, the size of the light-receiving element 3 also becomes smaller. The size of the light-receiving element 3 can also be said to be the area occupied by multiple pixels arranged on the light-receiving element 3.

[0056] 4 , the light splitting member 22 reflects at least a portion of the light emitted from the light source LS via the optical fiber toward the object surface OS. The light from the light source LS reflected by the light splitting member 22 is collimated along the optical axis AX by the lens group 21 and is then irradiated onto the illumination region IR of the object surface OS.

[0057] The first reflected light RL1 and the second reflected light RL2 reflected by the irradiation of the irradiation region IR with parallel light from the light-collecting optical system 2 (lens group 21 ) enter the lens group 21 and are guided to the light splitting member 22 .

[0058] An optical thin film TF is provided in a region of the light dividing member 22 through which the first reflected light RL1 passes, in order to transmit a part of the first reflected light RL1 toward the light receiving element 3 and to prevent the other part of the first reflected light RL1 from entering the light receiving element 3. For example, the optical thin film TF is provided on the optical path of the first reflected light RL1 in the light dividing member 22 and outside the optical path of the second reflected light RL2 in the light dividing member 22. For example, the optical thin film TF is provided in a region of the light dividing member 22 that includes the optical axis AX in a plane that intersects with the optical axis AX.

[0059] The optical thin film TF of the light splitting member 22 reflects the other part of the first reflected light RL1 in a direction different from that of the light receiving element 3. For example, the optical thin film TF is disposed at an angle of 45° with respect to the optical axis AX of the light collecting optical system 2, and reflects the other part of the first reflected light RL1 in a direction opposite to the direction in which the light from the light source LS is incident on the optical thin film TF. In other words, the first reflected light RL1 does not enter the light receiving element 3. It can also be said that the optical thin film TF reflects the other part of the first reflected light RL1 in the direction of the exit end of the optical fiber from which the light from the light source LS is emitted.

[0060] The optical thin film TF transmits a portion of the first reflected light RL1. The portion of the first reflected light RL1 that has transmitted through the optical thin film TF is incident on the light-receiving element 3. The amount of first reflected light RL1 incident on the light-receiving element 3 when the optical thin film TF is present can be reduced compared to the amount of first reflected light RL1 that would be incident on the light-receiving element 3 when the optical thin film TF is not present. Furthermore, the second reflected light RL2 is incident on the light-receiving element 3 via the light splitting member 22 without being incident on the optical thin film TF. Therefore, the light splitting member 22 (optical thin film TF) described above can reduce the difference in the amount of light between the first reflected light RL1 and the second reflected light RL2 that are incident on the light-receiving element 3.

[0061] As described above, the first reflected light RL1 is reflected light that has been reflected once by the irradiation region IR, whereas the second reflected light RL2 is reflected light that has been reflected multiple times (for example, twice) by the irradiation region IR, and the amount of light of the first reflected light RL1 is greater than the amount of light of the second reflected light RL2. If the difference in light amount between the first reflected light RL1 and the second reflected light RL2 exceeds the dynamic range of the light receiving element 3, it may become impossible to detect at least one of the first reflected light RL1 and the second reflected light RL2.

[0062] Therefore, by using the above-mentioned light dividing member 22 (optical thin film TF) to reduce the difference between the amount of light of the first reflected light RL1 and the amount of light of the second reflected light RL2 incident on the light receiving element 3, the first reflected light RL1 and the second reflected light RL2 can be reliably detected.

[0063] For example, the optical thin film TF may be a half mirror or a reflective film whose reflectance of the first reflected light RL1 is different from 50%. The optical thin film TF may be a film that reflects or transmits incident light depending on the polarization state of the incident light. For example, the optical thin film TF may be a film that reflects the s-polarized component of the incident light and transmits the p-polarized component.

[0064] The optical thin film TF of the light splitting member 22 may be configured to transmit a part of the first reflected light RL1 toward the light receiving element 3 and absorb the other part of the first reflected light RL1.

[0065] The optical thin film TF does not have to be provided along the entire optical path of the first reflected light RL1 in the light splitting member 22. For example, the optical thin film TF may be provided along at least a part of the optical path of the first reflected light RL1 in the light splitting member 22 so that at least a part of the light beam of the first reflected light RL1 that has entered the light splitting member 22 is incident on the optical thin film TF.

[0066] The optical thin film TF does not have to be provided outside the optical path of the second reflected light RL2 in the light splitting member 22. The optical thin film TF may be provided in part of the optical path of the second reflected light RL2 in the light splitting member 22 so that a part of the light beam of the second reflected light RL2 incident on the light splitting member 22 is incident on the optical thin film TF.

[0067] The light splitting member 22 may be configured so that the amount of light in the portion of the first reflected light RL1 is less than the amount of light in the other portion. For example, the optical thin film TF of the light splitting member 22 may be configured to transmit 10% of the incident first reflected light RL1 and reflect 90%. Furthermore, the light splitting member 22 may be configured so that the incident light is not substantially reflected, scattered, or absorbed in the region where the second reflected light RL2 is mainly incident.

[0068] The light dividing member 22 may not have an optical thin film TF in the region through which the first reflected light RL1 passes, for transmitting part of the first reflected light RL1 toward the light receiving element 3 and preventing the other part of the first reflected light RL1 from entering the light receiving element 3. For example, the light dividing member 22 may be configured so that the transmittance of the first reflected light RL1 on the optical path of the light dividing member 22 is lower than the transmittance of the second reflected light RL2 on the optical path of the light dividing member 22. For example, the light splitting member 22 may be configured such that at least a portion of the optical path of the first reflected light RL1 in the light splitting member 22 (e.g., at least a portion of the area of ​​the light splitting member 22 along the optical axis AX) is made of a glass material whose transmittance for the first reflected light RL1 is lower than that for the second reflected light RL2, and at least a portion of the optical path of the second reflected light RL2 in the light splitting member 22 is made of a glass material whose transmittance for the second reflected light RL2 is equal to or greater than that of the first reflected light RL1.

[0069] 4, the light receiving element 3 is an element such as a CMOS having pixels arranged two-dimensionally. The light receiving element 3 is disposed on a surface where the light is collected so that the areas corresponding to the first reflected light RL1 and the second reflected light RL2 can be distinguished as different areas in space.

[0070] The light receiving element 3 detects light (e.g., at least one of the first reflected light RL1 and the second reflected light) that is reflected from the irradiation region IR and collected by the collecting optical system 2 when the light from the collecting optical system 2 is irradiated onto the irradiation region IR, and outputs data representing the detection result. The data representing the detection result is, for example, data representing the intensity distribution of the light (e.g., at least one of the first reflected light RL1 and the second reflected light) that is collected by the collecting optical system 2. Note that the data representing the intensity distribution may be two-dimensional image data.

[0071] That is, the light receiving element 3 can detect the intensity distribution of the light collected by the collecting optical system 2. Note that the data representing the intensity distribution output from the light receiving element 3 can also be said to be data based on the light reflected from the riblet structure of the inspection target. Note that the light receiving element 3 may be an element such as a line sensor having pixels arranged one-dimensionally. Even in this case, it is possible to output data representing the intensity distribution of the light collected by the collecting optical system 2.

[0072] The light receiving element 3 may be arranged on a plane other than the plane conjugate with the object surface OS with respect to the focusing optical system 2. Furthermore, the light receiving element 3 may have a light receiving surface 3a that receives light focused by the focusing optical system 2, and the light receiving surface 3a may be arranged on a plane other than the plane conjugate with the object surface OS with respect to the focusing optical system 2. The light receiving element 3 detects the light received by the light receiving surface 3a. Therefore, the light receiving surface 3a can also be said to be the detection surface of the light receiving element 3.

[0073] The surface conjugate to the object surface OS with respect to the focusing optical system 2 corresponds to the image plane of the focusing optical system 2 when the object surface OS is the object plane, or a surface conjugate to the image plane with respect to another optical system such as a relay optical system. Light incident on the focusing optical system 2 from a point on the object surface OS is focused to a single point on the image plane of the focusing optical system 2. In other words, the first reflected light RL1 and the second reflected light RL2 overlap on the image plane of the focusing optical system 2 or a surface conjugate to the image plane. Therefore, if the light-receiving element 3 (light-receiving surface 3 a of the light-receiving element 3) is disposed on the image plane of the focusing optical system 2 or a surface conjugate to the image plane, the first reflected light RL1 and the second reflected light RL2 are not separated on the image plane of the focusing optical system 2 or a surface conjugate to the image plane, and therefore, they cannot be properly distinguished from each other on the intensity distribution of light detected by a single light-receiving element 3.

[0074] By arranging the light receiving element 3 (light receiving surface 3 a) on a plane other than the plane conjugate with the object surface OS with respect to the focusing optical system 2, it is possible to distinguish and detect the first reflected light RL1 and the second reflected light RL2 with a single light receiving element 3. Therefore, the optical device 1 does not require multiple light receiving elements (for example, three light receiving elements) for individually detecting the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2, or an optical system for directing the reflected light to each of the multiple light receiving elements, and therefore it is possible to inspect the riblet structure with a small and inexpensive configuration (simple configuration).

[0075] Furthermore, the light receiving surface 3 a may be arranged closer to the exit pupil plane of the focusing optical system 2 than an optical element arranged closest to the light receiving element 3 among the optical elements constituting the focusing optical system 2. In this case, the exit pupil of the focusing optical system 2 may be on the opposite side of the object surface OS with respect to the focusing optical system 2. In this embodiment, the optical element arranged closest to the light receiving element 3 among the optical elements constituting the focusing optical system 2 is the light splitting member 22. In this case, the light receiving surface 3 a may be arranged at a position closer to the exit pupil plane of the focusing optical system 2 than the distance between the light splitting member 22 and the exit pupil plane of the focusing optical system 2. Note that the position closer to the exit pupil plane of the focusing optical system 2 than the distance between the light splitting member 22 and the exit pupil plane of the focusing optical system 2 may be closer to the exit pupil plane as viewed from the object surface OS, or may be farther from the exit pupil plane.

[0076] With the above arrangement, the light receiving surface 3a is positioned at a position different from the plane conjugate with the object surface OS with respect to the focusing optical system 2 (a position different from the image plane of the focusing optical system 2 or a plane conjugate with the image plane), and is positioned at or near the exit pupil plane of the focusing optical system 2, so that the first reflected light RL1 and the second reflected light RL2 can be properly distinguished on the light intensity distribution detected by one light receiving element 3.

[0077] Furthermore, the size of the area on the light-receiving surface 3a occupied by a light beam that enters the light-receiving optical system 2 from a point on the object surface OS at the maximum numerical aperture on the object surface OS side of the light-receiving optical system 2 and reaches the light-receiving element 3 may be greater than 0 times the size of the light-receiving surface 3a. In other words, a light beam that enters the light-receiving optical system 2 from a point on the object surface OS at the maximum numerical aperture on the object surface OS side of the light-receiving optical system 2 and reaches the light-receiving element 3 does not have to be focused to a single point on the light-receiving surface 3a of the light-receiving element 3 (a focusing point does not have to be created on the light-receiving surface 3a). In other words, an image of the object surface OS does not have to be created on the light-receiving surface 3a of the light-receiving element 3. The size of this area may be, for example, 0.1 times or more the size of the light-receiving surface 3a. In this case, it is possible to properly distinguish between an area corresponding to the first reflected light RL1 and an area corresponding to the second reflected light RL2 on the intensity distribution of light detected by one light-receiving element 3.

[0078] It is assumed that the area of ​​a point on the object surface OS is 0. For example, if the size of the area on the light-receiving surface 3a occupied by a light beam that enters the light-receiving optical system 2 from a point on the object surface OS and reaches the light-receiving element 3 with the maximum numerical aperture on the object surface OS side of the light-receiving optical system 2 is 0 times the size of the light-receiving surface 3a, the light-receiving surface 3a is disposed on a plane conjugate to the object surface OS with respect to the light-receiving optical system 2 (the image plane of the light-receiving optical system 2 or a plane conjugate to the image plane). If the size of the area is 0 times the size of the light-receiving surface 3a, i.e., if the light is focused at a single point on the light-receiving surface 3a, the first reflected light RL1 and the second reflected light RL2 will overlap on the light-receiving surface 3a, and therefore it will be impossible to properly distinguish between the area corresponding to the first reflected light RL1 and the area corresponding to the second reflected light RL2 on the intensity distribution of light detected by one light-receiving element 3.

[0079] Furthermore, the size of the region does not have to be 0.1 times or more the size of the light receiving surface 3a, and may be, for example, 0.001 times or more, 0.01 times or more, 1 time or more, or 10 times or more.

[0080] The light receiving surface 3 a may be arranged on a plane that has an optical Fourier transform relationship with the object surface OS by the focusing optical system 2. The plane that has an optical Fourier transform relationship with the object surface OS by the focusing optical system 2 may be referred to as the pupil plane of the focusing optical system 2. Alternatively, the light receiving surface 3 a may be arranged in a pupil space defined by the pupil plane of the focusing optical system 2 and an optical surface on the entrance side that is adjacent to the pupil plane.

[0081] In the focusing optical system 2, the diameter of the light beam supplied from the light source LS to the light splitting member 22 corresponds to the diameter of the aperture stop. For example, the exit pupil plane of the focusing optical system 2 is a plane conjugate with a position where the diameter of the light beam emitted from the light source LS is limited (for example, the end face of the optical fiber connecting the light source LS and the light splitting member 22 on the light splitting member 22 side).

[0082] In the optical device 1 of this embodiment, as an example, the light receiving surface 3 a is arranged on the exit pupil plane of the focusing optical system 2. Note that the light receiving surface 3 a may be arranged on a plane that is conjugate with the exit pupil plane of the focusing optical system 2 with respect to another optical system, such as a relay optical system, via the other optical system.

[0083] In addition, the optical device 1 may be provided with a plurality of light receiving elements for individually detecting the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2, or may be provided with an optical system for directing the reflected light into each of the plurality of light receiving elements.

[0084] The light source LS may have an aperture stop on the surface from which the light beam emerges or on a surface conjugate with the surface from which the light beam emerges with respect to the light-transmitting optical system into which the light emitted from the light source LS is incident. Such an aperture stop makes it possible to appropriately set the opening angle of the light beam directed toward the irradiation area IR illuminated by the light-collecting optical system 2. It can also be said that the aperture stop makes it possible to appropriately adjust the numerical aperture of the light-collecting optical system 2 on the object surface OS side (the irradiation area IR side).

[0085] The light-sending optical system may include a relay optical system. The light-sending optical system may include a field stop. For example, if the light-sending optical system includes a relay optical system, the relay optical system may include a field stop. The field stop allows the range of the irradiation region IR onto which light is irradiated by the focusing optical system 2 to be appropriately set.

[0086] A light intensity measuring device may be provided to measure the intensity of light emitted from the light source LS. The light intensity measuring device may be disposed on an optical path split by a beam splitter such as a half mirror disposed on the optical path of light from when it is emitted from the light source LS until it is irradiated onto the irradiation region IR. The light intensity measuring device may measure the intensity of the light split by the beam splitter. The output of the light source LS may be adjusted based on the intensity of the light emitted from the light source LS measured by the light intensity measuring device.

[0087] FIG. 7 is a schematic diagram showing the first light reception data (an example of an image indicated by the first light reception data).

[0088] In the first light reception data RD1, which is an example of light reception data representing the result of light reception, the amount of light corresponding to the first reflected light RL1 is represented in a central region around the optical axis AX of the focusing optical system 2, and the amount of light corresponding to the second reflected light RL2 is represented in a region other than the central region. For the sake of explanation, in Figure 7, a virtual line HL1 is shown corresponding to a direction perpendicular to the first direction D1 in which the convex portions C are continuous on the object surface OS.

[0089] When the inclined surfaces T1 and T2 of the convex portion C are symmetrical with respect to the third direction D3, a pair of second reflected light beams RL2-1 and RL2-2 included in the second reflected light beam RL2 are represented along the imaginary line HL at positions symmetrical with respect to the position corresponding to the optical axis AX of the focusing optical system 2. In the first received light data RD1, the first reflected light beam RL1 is represented at a position along the imaginary line HL1.

[0090] The light reception data representing the result of light reception may be data representing the intensity distribution of light collected on the light receiving surface 3a by the light collecting optical system 2. The data representing the intensity distribution of light collected on the light receiving surface 3a by the light collecting optical system 2 is not limited to a two-dimensional image such as the first light reception data RD1 shown in FIG. 7 , but may be data representing the intensity distribution of the amount of light along the virtual line HL1, for example. The light reception data representing the result of light reception may not represent either the second reflected light RL2-1 or RL2-2 of the second reflected light RL2. For example, the light receiving element 3 may detect at least one of the second reflected light RL2-1 and the second reflected light RL2-2 of the second reflected light RL2 collected on the light receiving surface 3a by the light collecting optical system 2.

[0091] 4 again, the housing 4 is a housing that houses the condensing optical system 2 and the light receiving element 3, and is made of a plastic material such as polypropylene or ABS resin. The housing 4 may also be made of a metal material such as an aluminum alloy.

[0092] The housing 4 has an abutting member 4a. The abutting member 4a protrudes toward the object surface OS further than the positive meniscus lens L1, which is arranged closest to the object surface OS among the optical members constituting the light-collecting optical system 2, and is capable of abutting against the object surface OS. The abutting member 4a is capable of abutting against at least a portion of the object surface OS excluding the irradiation region IR.

[0093] The abutment member 4a and the focusing optical system 2 are arranged so that when the abutment member 4a abuts against the object surface OS, the distance between the focusing optical system 2 and the object surface OS in the direction of the optical axis AX of the focusing optical system 2 is equal to the working distance WD on the object surface OS side of the focusing optical system 2. The optical device 1 in which the abutment member 4a and the focusing optical system 2 are arranged in this manner can easily inspect the object surface OS because, by abutting the abutment member 4a against the object surface OS, the distance between the focusing optical system 2 and the object surface OS is equal to the working distance WD on the object surface OS side of the focusing optical system 2.

[0094] The abutting member 4a has a support member 4b. For example, the support member 4b may support the positive meniscus lens L1 of the focusing optical system 2. The support member 4b may support the positive meniscus lens L1 so that the position of the positive meniscus lens L1 relative to the housing 4 does not change. The support member 4b may support the positive meniscus lens L1 arranged closest to the object surface OS so that the distance between the focusing optical system 2 and the object surface OS in the direction of the optical axis AX of the focusing optical system 2 becomes the working distance WD of the focusing optical system 2 on the object surface OS side when the abutting member 4a abuts against the object surface OS. Note that the support member 4b may support at least one of the other optical members of the focusing optical system 2 (at least one of the positive lens L2, the positive meniscus lens L3, and the light splitting member 22) and the light receiving element 3, in addition to the positive meniscus lens L1.

[0095] The contact member 4a may be made of a material that is less hard than the material that makes up the convex portion C of the object surface OS, in order to prevent deformation of the object surface OS due to contact with the object surface OS.

[0096] The contact member 4 a may be formed integrally with the housing 4. Furthermore, the contact member 4 a does not have to directly support the optical members and the light receiving element 3 included in the light collecting optical system 2, and other members may support them.

[0097] The optical device 1 does not have to be in contact with the object surface OS. Also, the housing 4 does not have to include the contact member 4a.

[0098] The computer 5 is an information processing device that acquires the light reception data from the light receiving element 3 and inspects the object surface OS.

[0099] The computer 5 is communicably connected to the optical device 1 according to an existing communication standard such as USB (Universal Serial Bus, registered trademark) or Bluetooth (registered trademark).

[0100] FIG. 8 is a schematic diagram showing the general configuration of the computer 5.

[0101] The computer 5 includes an input / output interface 51 , a memory 52 , and a processor 53 .

[0102] The input / output interface 51 is an example of a communication unit, and has an interface circuit for receiving data to be processed by the computer 5 or outputting data processed by the computer 5. The input / output interface 51 includes, for example, a peripheral interface circuit for connecting the computer 5 to various peripheral devices such as the optical device 1, a keyboard, and a display, or a communication interface circuit for connecting the computer 5 to a communication network.

[0103] The memory 52 is an example of a storage unit and includes a volatile semiconductor memory and a non-volatile semiconductor memory. The memory 52 stores various data used in processing by the processor 53, such as light-receiving data acquired from the light-receiving element 3, and reference data and threshold values ​​for inspecting the riblet structure. The memory 52 also stores various application programs, such as inspection programs that execute inspection processes. The reference data for inspecting the riblet structure can also be referred to as reference data for inspecting the riblet structure.

[0104] The processor 53 is an example of a control unit and includes one or more processors and their peripheral circuits. The processor 53 may further include other arithmetic circuits such as a logic unit, a numerical calculation unit, or a graphics processing unit.

[0105] FIG. 9 is a functional block diagram of the processor 53 of the computer 5.

[0106] The processor 53 of the computer 5 has, as functional blocks, a calculation unit 531, a detection unit 532, and a measurement unit 533. Each of these units in the processor 53 is a functional module implemented by a program executed on the processor 53. A computer program that realizes the functions of each unit in the processor 53 may be provided in a form recorded on a computer-readable portable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, each of these units in the processor 53 may be implemented in the computer 5 as an independent integrated circuit, microprocessor, or firmware.

[0107] The calculation unit 531 performs calculations including inspection of the riblet structure on the object surface OS based on the light reception data RD acquired from the light receiving element 3. The object surface OS is an example of an inspected surface that is the target of inspection in the calculations by the calculation unit 531. As described above, the light reception data RD acquired from the light receiving element 3 may be data, such as image data, that represents the intensity distribution of light focused on the light receiving surface 3 a by the focusing optical system 2. Note that the calculation unit 531 can also be referred to as an inspection unit because it inspects the riblet structure.

[0108] The calculation unit 531 inspects at least one of the convex portion C, the region R, and the convex portion C and the region R when inspecting the object surface OS.

[0109] The calculation unit 531 may determine whether the shape of the convex portion C is good or bad as an inspection of the riblet structure based on data representing the intensity distribution.

[0110] The calculation unit 531 may inspect the riblet structure based on a comparison result between the intensity of the first reflected light RL1 incident on the light-receiving surface 3 a and the intensity of the second reflected light RL2 incident on the light-receiving surface 3 a. For example, the calculation unit 531 may determine whether the shape of the riblet structure is acceptable as an inspection of the riblet structure based on a comparison result between the intensity of the first reflected light RL1 incident on the light-receiving surface 3 a and the intensity of the second reflected light RL2 incident on the light-receiving surface 3 a. For example, the calculation unit 531 may determine whether the shape of the convex portion C is acceptable as the quality of the shape of the riblet structure.

[0111] The intensity of the reflected light incident on the light-receiving surface 3 a corresponds to the luminance of a region corresponding to the reflected light in data (on the image represented by the intensity distribution data) representing the intensity distribution detected by the light-receiving element 3. The calculation unit 531 identifies a region (on the image represented by the intensity distribution data) corresponding to the first reflected light RL1 and a region corresponding to the second reflected light RL2 from the data representing the intensity distribution. For example, the calculation unit 531 extracts pixels on the image represented by the intensity distribution data whose luminance values ​​are equal to or greater than a predetermined threshold, and clusters and groups the extracted pixels to identify a region on the image represented by the intensity distribution data corresponding to the first reflected light RL1 and the second reflected light RL2.

[0112] The calculation unit 531 calculates statistical representative values ​​such as the maximum (peak), average, mode, and median luminance values ​​of each identified region. The representative luminance value of the region corresponding to the first reflected light RL1 calculated by the calculation unit 531 represents the intensity of the first reflected light RL1 incident on the light-receiving surface 3a. The representative luminance value of the region corresponding to the second reflected light RL2 calculated by the calculation unit 531 represents the intensity of the second reflected light RL2 incident on the light-receiving surface 3a. The calculation unit 531 then compares the representative luminance value of the region corresponding to the first reflected light RL1 with the representative luminance value of the region corresponding to the second reflected light RL2 in the data representing the intensity distribution (on the image represented by the intensity distribution data), thereby comparing the intensity of the first reflected light RL1 with the intensity of the second reflected light RL2.

[0113] The calculation unit 531 may calculate at least one of the statistical representative values ​​described above. That is, the calculation unit 531 may calculate at least one of the maximum value (peak), average value, mode, and median value of the luminance of each identified region. The calculation unit 531 may use methods other than clustering to identify the region corresponding to the first reflected light RL1 and the region corresponding to the second reflected light RL2 (on the image represented by the intensity distribution data) from the data representing the intensity distribution.

[0114] For example, the calculation unit 531 may use template matching to identify an area on the image represented by the intensity distribution data that corresponds to the first reflected light RL1 and an area on the image represented by the intensity distribution data that corresponds to the second reflected light RL2. In this case, the calculation unit 531 may use reference data that represents the reference intensity distribution of the first reflected light RL1 and the second reflected light RL2 as a template, and compare the template with data that represents the intensity distribution output from the light receiving element 3, thereby identifying an area on the image represented by the intensity distribution data that corresponds to the first reflected light RL1 and the second reflected light RL2.

[0115] In comparing the intensities of the first reflected light RL1 and the second reflected light RL2, the calculation unit 531 determines the ratio between the intensities of the first reflected light RL1 and the second reflected light RL2. In addition, in comparing the intensities of the first reflected light RL1 and the second reflected light RL2, the calculation unit 531 may determine the difference between the intensities of the first reflected light RL1 and the second reflected light RL2.

[0116] For example, on an object surface OS where the apex of the convex portion C has been chipped (worn) and rounded due to friction with the fluid, the riblet structure may not sufficiently reduce fluid resistance. Because the intensity of the second reflected light RL2 reflected in the reflection direction of the second reflected light RL2 (i.e., the second reflection direction and the third reflection direction) is reduced, the intensity of the second reflected light RL2 reflected by an object surface OS where the apex of the convex portion C is chipped is reduced compared to the intensity of the second reflected light RL2 reflected by an object surface OS where the apex is not chipped. Therefore, the statistical representative value of the luminance of the region on the image represented by the intensity distribution data, which corresponds to the second reflected light RL2 reflected by an object surface OS where the apex of the convex portion C is chipped, changes (e.g., decreases) from the statistical representative value of the luminance of the region on the image represented by the intensity distribution data, which corresponds to the second reflected light RL2 reflected by an object surface OS where the apex is not chipped.

[0117] In more detail, the area of ​​the inclined surfaces (inclined surfaces T1 and T2) defined by a predetermined apex angle A (e.g., 45°) is reduced on the object surface OS where the apex of the convex portion C is missing, compared to the object surface OS where the apex of the convex portion C is not missing. Therefore, the amount of light incident on the object surface OS that is reflected by the inclined surfaces of the convex portion C is reduced, and the amount of second reflected light RL2 is reduced.

[0118] It can also be said that the second reflected light RL2 reflected by the object surface OS where the apex of the convex portion C is missing is dispersed over a wider area of ​​the light-receiving surface 3 a compared to the second reflected light RL2 reflected by the object surface OS where the apex is not missing. Therefore, it can also be said that the statistical representative value of the luminance of the area corresponding to the second reflected light RL2 reflected by the object surface OS where the apex is missing varies from the statistical representative value of the luminance of the area corresponding to the second reflected light RL2 reflected by the object surface OS where the apex is not missing.

[0119] Furthermore, even if the apex of the convex portion C is missing, as long as the state of the region R does not change, the statistical representative value of the brightness of the region on the image represented by the intensity distribution data corresponding to the first reflected light RL1 reflected by the region R will not change substantially compared to when the apex of the convex portion C is not missing.

[0120] From the above, the ratio of the intensity of the first reflected light RL1 to the intensity of the second reflected light RL2 reflected by the object surface OS where the apex of the convex portion C is missing changes from the ratio of the intensity of the first reflected light RL1 to the intensity of the second reflected light RL2 reflected by the object surface OS where the apex of the convex portion C is not missing.

[0121] For example, if the difference between the ratio of the intensity of the second reflected light RL2 to the intensity of the first reflected light RL1 calculated based on the received light data RD (i.e., the ratio of the representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the first reflected light RL1 to the representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the second reflected light RL2) and a reference ratio value exceeds a predetermined threshold, the calculation unit 531 may determine that the rounding of the vertex of the convex portion C in terms of the shape of the convex portion C on the object surface OS is poor.

[0122] Note that the poor rounding of the apex of the convex portion C may refer to a state in which the apex of the convex portion C is relatively significantly chipped (worn) due to friction with the fluid or the like. Note that the poor rounding of the apex of the convex portion C can also be said to refer to deterioration of the convex portion C. Note that the rounding of the apex of the convex portion C as the shape of the convex portion C can also be said to be the curvature of the apex of the convex portion C or the radius of curvature of the apex of the convex portion C.

[0123] The above-mentioned reference ratio value can also be considered reference data for inspecting the quality of the riblet structure (the convex portion of the object surface OS). This reference ratio value may be the ratio of the intensity of the second reflected light RL2 to the intensity of the first reflected light RL1 when light is actually irradiated onto the object surface OS on which the convex portion C and region R of a non-defective product are formed, when the convex portion C has a shape that can be considered a non-defective product (for example, a state in which the apex of the convex portion C is not missing). This reference ratio value may also be the ratio of the intensity of the second reflected light RL2 to the intensity of the first reflected light RL1 calculated by a simulation using a ray tracing method or the like, assuming that light is irradiated onto a surface on which the convex portion C and region R of a non-defective product are formed.

[0124] Note that the calculation unit 531 may determine that the rounding of the apex of the convex portion C is defective when the calculated ratio of the intensity of the second reflected light RL2 to the intensity of the first reflected light RL1 differs from a reference ratio. For example, the calculation unit 531 may determine that the rounding of the apex of the convex portion C is defective when the calculated ratio of the intensity of the second reflected light RL2 to the intensity of the first reflected light RL1 is lower than the reference ratio.

[0125] FIG. 10 is a diagram illustrating the ratio of the luminance of the first reflected light RL1 to the second reflected light RL2 in the first received light data RD1.

[0126] For example, in graph GR2 corresponding to first light reception data RD1, the horizontal axis indicates the position on virtual line HL1, and the vertical axis indicates the brightness ratio when the brightness of the peak corresponding to first reflected light RL1 is set to 1. The peak corresponding to first reflected light RL1 appears on virtual line HL1 between the peaks corresponding to second reflected light RL2-1 and RL2-2. The brightness ratio value of the peaks corresponding to the pair of second reflected light beams RL2-1 and RL2-2 appearing on virtual line HL1 is 0.3.

[0127] For example, if the reference data (e.g., the above-mentioned reference ratio value) for inspecting the quality of the riblet structure (the convex portion of the object surface OS) is 0.2 and the predetermined threshold value is ±0.2, the difference between the brightness ratio of 0.3 at the peak corresponding to the second reflected light RL2-1 and RL2-2 and the reference ratio value of 0.2 is 0.1, which does not exceed the predetermined threshold value ±0.2, so the calculation unit 531 determines that the rounding of the apex of the convex portion C as the shape of the convex portion C of the object surface OS is good.

[0128] It should be noted that the objects for which the calculation unit 531 determines whether they are good or bad are not limited to the rounding of the apexes of the convex portions C. For example, the calculation unit 531 may use the above-described processing to determine whether the shape of the riblet structure (the shape of the convex portions C) is good or bad at least one of the apex angle A of the convex portions C, the height H of the convex portions C, the symmetry of the convex portions C, and the spacing P of the convex portions C in the second direction D2.

[0129] In addition, the calculation unit 531 may also use the intensity of light emitted from the light source LS, which is output from the above-mentioned light intensity measuring device, to determine whether the riblet structure is good or bad.

[0130] The calculation unit 531 does not need to use the second reflected light RL2-1 or the second reflected light RL2-2 of the second reflected light RL2 to inspect the quality of the riblet structure described above. In this case, the calculation unit 531 does not need to calculate the intensity of the second reflected light RL2-1 (that is, the statistical representative value of the luminance of the region on the image represented by the intensity distribution data that corresponds to the second reflected light RL2-1) or the intensity of the second reflected light RL2-2 (that is, the statistical representative value of the luminance of the region on the image represented by the intensity distribution data that corresponds to the second reflected light RL2-2).

[0131] For example, the calculation unit 531 may calculate the ratio between the intensity of the first reflected light RL1 and the intensity of the second reflected light RL2-1 (i.e., the ratio of the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the first reflected light RL1 to the representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the second reflected light RL2-1 to the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the first reflected light RL1), or the ratio between the intensity of the first reflected light RL1 and the intensity of the second reflected light RL2-2 (i.e., the ratio of the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the first reflected light RL1 to the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the second reflected light RL2-2), and compare this with standard data for inspecting the quality of the above-mentioned riblet structure to determine the quality of the shape of the riblet structure (e.g., the quality of the rounding of the apex of the convex portion C).

[0132] The calculation unit 531 does not have to use the first reflected light RL1 to inspect the quality of the riblet structure described above. In this case, the calculation unit 531 does not have to calculate the intensity of the first reflected light RL1 (i.e., the statistical representative value of the luminance of the region on the image represented by the intensity distribution data and corresponding to the first reflected light RL1). For example, the calculation unit 531 may calculate the intensity of the second reflected light RL2 (i.e., the statistical representative value of the luminance of the region on the image represented by the intensity distribution data and corresponding to the second reflected light RL2) and compare it with reference data for inspecting the quality of the riblet structure to determine the quality of the shape of the riblet structure (e.g., the quality of the rounding of the apexes of the convex portions C).

[0133] In this case, the reference data for inspecting the quality of the riblet structure may be the reference intensity of the second reflected light RL2 reflected when light is actually irradiated onto the object surface OS on which the convex portion C and region R of the good product are formed, when the convex portion C has a shape that can be considered to be a good product, or it may be the reference intensity of the second reflected light RL2 calculated by simulation.

[0134] The calculation unit 531 may calculate the intensity of the second reflected light RL2-1 (i.e., the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the second reflected light RL2-1) or the intensity of the second reflected light RL2-2 (i.e., the statistical representative value of the brightness of the area on the image represented by the intensity distribution data corresponding to the second reflected light RL2-2) of the second reflected light RL2, and determine the quality of the shape of the riblet structure by comparing it with standard data for inspecting the quality of the above-mentioned riblet structure.

[0135] For example, the calculation unit 531 may determine the acceptability of the shape of the riblet structure by comparing the difference between the calculated intensity of the second reflected light RL2-1 and a reference intensity of the second reflected light RL2-1 with a predetermined threshold. The calculation unit 531 may determine the acceptability of the shape of the riblet structure by comparing the difference between the calculated intensity of the second reflected light RL2-2 and a reference intensity of the second reflected light RL2-2 with a predetermined threshold.

[0136] For example, the calculation unit 531 may determine that the shape of the riblet structure is defective when the calculated intensity of the second reflected light RL2-1 differs from a reference intensity of the second reflected light RL2-1. The calculation unit 531 may determine that the shape of the riblet structure is defective when the calculated intensity of the second reflected light RL2-2 differs from a reference intensity of the second reflected light RL2-2.

[0137] For example, the calculation unit 531 may determine that the shape of the riblet structure is defective when the calculated intensity of the second reflected light RL2-1 is lower than a reference intensity of the second reflected light RL2-1. The calculation unit 531 may determine that the shape of the riblet structure is defective when the calculated intensity of the second reflected light RL2-2 is lower than a reference intensity of the second reflected light RL2-2.

[0138] The calculation unit 531 may inspect the riblet structure based on the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 on the light-receiving surface 3a and the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2. For example, the calculation unit 531 may determine whether the shape of the riblet structure is acceptable as an inspection of the riblet structure based on the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 on the light-receiving surface 3a and the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2. For example, the calculation unit 531 may determine whether the shape of the convex portion C is acceptable as the shape of the riblet structure.

[0139] The position of incidence of the reflected light on the light-receiving surface 3a corresponds to the position of the region corresponding to the reflected light in the data representing the intensity distribution detected by the light-receiving element 3 (on the image represented by the intensity distribution data). Similarly to the above, the calculation unit 531 identifies the region corresponding to the first reflected light RL1 and the region corresponding to the second reflected light RL2 (on the image represented by the intensity distribution data) from the data representing the intensity distribution. For example, the calculation unit 531 extracts pixels whose luminance values ​​are equal to or greater than a predetermined threshold on the image represented by the intensity distribution data, and clusters the extracted pixels into groups. The calculation unit 531 may also use template matching to identify the region corresponding to the first reflected light RL1 and the region corresponding to the second reflected light RL2 on the image represented by the intensity distribution data.

[0140] The calculation unit 531 calculates, for each of the identified regions corresponding to the first reflected light RL1 and the second reflected light RL2 on the image represented by the intensity distribution data, at least one of the position of the pixel having the maximum brightness and the position of the geometric center of gravity of the region as the representative position of the reflected light.

[0141] Note that the position calculated by the calculation unit 531 on the image represented by the intensity distribution data corresponding to the first reflected light RL1 (representative position of the first reflected light RL1) represents the incident position of the first reflected light RL1 on the light-receiving surface 3 a. Also, the position calculated by the calculation unit 531 on the image represented by the intensity distribution data corresponding to the second reflected light RL2 (representative position of the second reflected light RL2) represents the incident position of the second reflected light RL2 on the light-receiving surface 3 a.

[0142] Then, based on the identified position corresponding to the first reflected light RL1 (representative position of the first reflected light RL1) and the positions corresponding to the second reflected light RL2-1 and RL2-2 (representative positions of the second reflected light RL2) on the image represented by the intensity distribution data, the calculation unit 531 calculates the distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-1, and the distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution.

[0143] The distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-1 on the image represented by the intensity distribution represents the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1. Also, the distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution represents the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2.

[0144] For example, the second reflected light RL2-1 is light reflected by the inclined surface T1 and region R of the convex portion C, and the second reflected light RL2-2 is light reflected by the inclined surface T2 and region R of the convex portion C. If the inclination of the inclined surface T1 and the inclination of the inclined surface T2 are not symmetrical with respect to the third direction D3, the reflection direction of the second reflected light RL2-1 and the reflection direction of the second reflected light RL2-2 will not be symmetrical. As a result, the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 differs from the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2. If the difference between the ratio or difference between the calculated distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 and the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2 and the standard ratio value or standard difference value exceeds a predetermined threshold, the calculation unit 531 can determine that the symmetry of the convex portion C as a shape of the convex portion C is poor.

[0145] The calculation unit 531 can determine that the symmetry of the convex portion C as a shape of the convex portion C is good if the difference between the ratio or difference between the calculated distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 and the distance between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2 and the standard ratio value or standard difference value does not exceed a predetermined threshold value.

[0146] The above-mentioned reference value can also be considered reference data for inspecting the quality of the riblet structure. This reference value may be the ratio or difference between the distance between the incident position on the light-receiving surface 3a of the first reflected light RL1 and the incident position on the light-receiving surface 3a of the second reflected light RL2-1, which are actually reflected when light is irradiated onto the object surface OS on which the convex portion C and region R of the good product are formed, and the distance between the incident position on the light-receiving surface 3a of the first reflected light RL1 and the incident position on the light-receiving surface 3a of the second reflected light RL2-2.

[0147] In addition, this reference value may be the ratio or difference between the distance between the incident position of the first reflected light RL1 on the light-receiving surface 3a and the incident position of the second reflected light RL2-1 on the light-receiving surface 3a, and the distance between the incident position of the first reflected light RL1 on the light-receiving surface 3a and the incident position of the second reflected light RL2-2 on the light-receiving surface 3a, calculated by assuming that light is irradiated onto a surface on which the convex portion C and region R of the non-defective shape are formed, using a simulation such as ray tracing.

[0148] The calculation unit 531 may determine that the symmetry of the convex portion C is poor if the ratio or difference between the calculated interval between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 and the interval between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2 is different from a reference ratio or reference difference. The calculation unit 531 may determine that the symmetry of the convex portion C is poor if the calculated interval between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-1 is different from the interval between the incident position of the first reflected light RL1 and the incident position of the second reflected light RL2-2.

[0149] In addition, the calculation unit 531 may determine whether the symmetry of the convex portion C as a shape of the convex portion C is good or bad based on the incident position of the first reflected light RL1 on the light receiving surface 3a, the incident position of the second reflected light RL2-1 on the light receiving surface 3a, and the incident position of the second reflected light RL2-2 on the light receiving surface 3a.

[0150] In this case, as described above, the calculation unit 531 calculates the position corresponding to the first reflected light RL1 (representative position of the first reflected light RL1) and the positions corresponding to the second reflected light RL2-1 and RL2-2 (representative positions of the second reflected light RL2) on the image represented by the intensity distribution data as the incident positions of each reflected light.

[0151] The calculation unit 531 may then determine the quality of the shape of the riblet structure (for example, the quality of the symmetry of the convex portion C) based on the difference (interval) between the calculated incident position of the first reflected light RL1 on the light receiving surface 3a and the reference incident position of the first reflected light RL1, the difference (interval) between the calculated incident position of the second reflected light RL2-1 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-1, and the difference (interval) between the calculated incident position of the second reflected light RL2-2 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-2.

[0152] For example, the calculation unit 531 may determine that the shape of the riblet structure (e.g., the symmetry of the convex portion C) is defective if at least one of the differences between the incident position of the first reflected light RL1 and the reference incident position of the first reflected light RL1, the difference between the incident position of the second reflected light RL2-1 and the reference incident position of the second reflected light RL2-1, and the difference between the incident position of the second reflected light RL2-2 and the reference incident position of the second reflected light RL2-2 exceeds a predetermined threshold.

[0153] The reference incident position can also be considered reference data for inspecting the quality of the riblet structure. The reference incident position may be the reference incident position on the light-receiving surface 3a of the second reflected light RL2-1 and the reference incident position on the light-receiving surface 3a of the second reflected light RL2-2, which are actually reflected when light is irradiated onto an object surface OS on which a good riblet structure is formed, when the riblet structure has a shape that can be considered good (for example, one inclined surface T1 and the other inclined surface T2 of the convex portion C are symmetrical with respect to the third direction D3).

[0154] The above-mentioned reference incident positions may be the reference incident position of the first reflected light RL1 on the light receiving surface 3a, the reference incident position of the second reflected light RL2-1 on the light receiving surface 3a, and the reference incident position of the second reflected light RL2-2 on the light receiving surface 3a, calculated by simulation.

[0155] In addition, comparing at least one of the differences between the incident position of the first reflected light RL1 and the reference incident position of the first reflected light RL1, the difference between the incident position of the second reflected light RL2-1 and the reference incident position of the second reflected light RL2-1, and the difference between the incident position of the second reflected light RL2-2 and the reference incident position of the second reflected light RL2-2 with a predetermined threshold can also be said to inspect the riblet structure by determining whether at least one of the positions of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2 in the image represented by the intensity distribution data (in other words, the intensity distribution) is included in a reference range of at least one of the positions of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2.

[0156] It should be noted that the object of determination of acceptability by the calculation unit 531 is not limited to the symmetry of the convex portions C. For example, the calculation unit 531 may use the above-described processing to determine the acceptability of at least one of the following as the shape of the riblet structure (the shape of the convex portions C): the rounding of the convex portions C, the apex angle A of the convex portions C, the height H of the convex portions C, and the spacing P of the convex portions C in the second direction D2.

[0157] In addition, the calculation unit 531 may determine the quality of the shape of the riblet structure (for example, the quality of the symmetry of the convex portion C as the shape of the convex portion C of the riblet structure) based on the incidence position of the second reflected light RL2-1 on the light receiving surface 3a and the incidence position of the second reflected light RL2-2 on the light receiving surface 3a, without using the incidence position of the first reflected light RL1 on the light receiving surface 3a.

[0158] In this case, the calculation unit 531 calculates the positions corresponding to the second reflected light RL2-1 and RL2-2 (representative positions of the second reflected light RL2) on the image represented by the intensity distribution data as the incident positions of the respective reflected lights, as described above.

[0159] The calculation unit 531 may then determine the quality of the shape of the riblet structure (for example, the quality of the symmetry of the convex portion C) by comparing the difference (spacing) between the calculated incident position of the second reflected light RL2-1 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-1 with the difference (spacing) between the calculated incident position of the second reflected light RL2-2 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-2.

[0160] For example, the calculation unit 531 may determine that the shape of the riblet structure is defective if the difference or ratio between the calculated incident position of the second reflected light RL2-1 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-1 and the difference between the calculated incident position of the second reflected light RL2-2 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-2 exceeds a predetermined threshold value.

[0161] The reference incident position can also be considered reference data for inspecting the quality of a riblet structure. When the riblet structure has a shape that can be considered to be good, the reference incident position may be determined by actually irradiating light onto an object surface OS on which a good riblet structure is formed, and determining the reference incident position of the reflected second reflected light RL2-1 on the light-receiving surface 3 a and the reference incident position of the second reflected light RL2-2 on the light-receiving surface 3 a.

[0162] The reference incident positions may be the reference incident positions of the second reflected light RL2-1 and the second reflected light RL2-2 on the light receiving surface 3a calculated by simulation.

[0163] In addition, the calculation unit 531 may determine that the shape of the riblet structure (for example, the symmetry of the convex portion C) is defective if the difference between the calculated incident position of the second reflected light RL2-1 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-1 is different from the difference between the calculated incident position of the second reflected light RL2-2 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-2.

[0164] Here, for example, the symmetry of the convex portion C can be said to be the symmetry of one inclined surface T1 and the other inclined surface T2 of the pair of inclined surfaces with respect to the third direction D3. For example, as described above, when the calculation unit 531 determines that the symmetry is poor, it can be said that the inclined surfaces T1 and T2 are asymmetric (the symmetry is broken) with respect to the third direction D3.

[0165] The symmetry of the convex portion C can also be said to be the relationship between the angle that one inclined surface T1 makes with the region R and the angle that the other inclined surface T2 makes with the region R. When these angles are different, the inclined surfaces T1 and T2 can be said to be asymmetric (their symmetry is broken) with respect to the third direction D3.

[0166] When a region R contacting one inclined surface T1 and a region R contacting the other inclined surface T2 are included in the same plane or two parallel planes, the direction of the second reflected light RL2-1 reflected by one inclined surface T1 and the direction of the second reflected light RL2-2 reflected by the other inclined surface T2 represent the inclination with respect to the normal direction of the plane containing region R. The distances between the position corresponding to the first reflected light RL1 and the positions corresponding to the second reflected lights RL2-1 and RL2-2 correspond to the directions of the second reflected lights RL2-1 and RL2-2, respectively.

[0167] The calculation unit 531 may determine the symmetry of one of the pair of inclined surfaces with the other inclined surface based on the distance between the position corresponding to the first reflected light RL1 and the positions corresponding to the second reflected light RL2-1 and RL2-2. For example, the calculation unit 531 may determine that the symmetry of the inclined surface in the convex portion C corresponding to the received light data is poor if the ratio or difference between the distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-1 and the distance between the position corresponding to the first reflected light RL1 and the position corresponding to the second reflected light RL2-2 exceeds a predetermined threshold.

[0168] In addition, the calculation unit 531 may inspect the riblet structure (for example, determine whether the symmetry of the convex portion C as the shape of the convex portion C is good or bad) based on the incident position of the second reflected light RL2-1 on the light receiving surface 3a and the incident position of the second reflected light RL2-2 on the light receiving surface 3a.

[0169] In this case, the calculation unit 531 calculates the positions corresponding to the second reflected light RL2-1 and RL2-2 (representative positions of the second reflected light RL2) on the image represented by the intensity distribution data as the incident positions of each reflected light, as described above.

[0170] The calculation unit 531 may then inspect the riblet structure based on the difference (distance) between the calculated incident position of the second reflected light RL2-1 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-1, and the difference (distance) between the calculated incident position of the second reflected light RL2-2 on the light receiving surface 3a and the reference incident position of the second reflected light RL2-2.

[0171] For example, the calculation unit 531 may determine that the shape of the riblet structure is defective if at least one of the differences between the incident position of the second reflected light RL2-1 and the reference incident position of the second reflected light RL2-1, and the difference between the incident position of the second reflected light RL2-2 and the reference incident position of the second reflected light RL2-2, exceeds a predetermined threshold.

[0172] The reference incident position can also be considered reference data for inspecting the quality of the riblet structure. When the riblet structure has a shape that can be considered to be good, the reference incident position may be the reference incident position on the light-receiving surface 3 a of the second reflected light RL2-1 and the reference incident position on the light-receiving surface 3 a of the second reflected light RL2-2, which are reflected when light is actually irradiated onto an object surface OS on which a good riblet structure is formed.

[0173] The reference incident position may be a reference incident position of the second reflected light RL2-1 on the light receiving surface 3a and a reference incident position of the second reflected light RL2-2 on the light receiving surface 3a calculated by simulation.

[0174] In addition, comparing the difference between the incident position of the second reflected light RL2-1 and the reference incident position of the second reflected light RL2-1, and the difference between the incident position of the second reflected light RL2-2 and the reference incident position of the second reflected light RL2-2 with a predetermined threshold can also be said to inspect the riblet structure by determining whether the position of the second reflected light RL2-1 and the position of the second reflected light RL2-2 in the image represented by the intensity distribution data (in other words, the intensity distribution) are included in the reference range of the position of the second reflected light RL2-1 and the position of the second reflected light RL2-2.

[0175] The region R may be scraped off due to friction with the fluid on the object surface OS or chipped off due to collision with a foreign object. The calculation unit 531 may inspect the quality of the shape of the region R as the shape of the riblet structure.

[0176] For example, the calculation unit 531 may inspect the quality of the shape of the region R based on data representing the intensity distribution of light collected by the collecting optical system 2 output from the light receiving element 3 (data based on reflected light from the riblet structure of the object to be inspected).

[0177] In this case, the calculation unit 531 may compare the data representing the intensity distribution with data representing a reference intensity distribution to determine whether the shape of the region R is good or bad. The data representing the reference intensity distribution can also be said to be reference data for inspecting the quality of the riblet structure.

[0178] When the region R has a shape that can be considered to be a non-defective product, the reference intensity distribution may be reference intensity distribution data of the reflected light that is actually irradiated onto the object surface OS on which the convex portion C of the non-defective product and the region R are formed. Note that this reference intensity distribution data may be calculated by a simulation such as a ray tracing method.

[0179] The calculation unit 531 may determine the acceptability of the shape of region R using any of the processes described above for determining the acceptability of the shape of the riblet structure (the acceptability of the shape of the convex portion C). The calculation unit 531 may determine the acceptability of the shape of the convex portion C and the acceptability of the shape of region R using any of the processes described above for determining the acceptability of the shape of the riblet structure (the acceptability of the shape of the convex portion C).

[0180] Note that foreign matter may become clogged in the region R. The shape of the region R may include a shape that has changed due to the clogging of foreign matter.

[0181] The calculation unit 531 may inspect the quality of the riblet structure by comparing data representing the intensity distribution output from the light receiving element 3 (data based on light reflected from the riblet structure to be inspected) with at least one of good product reference data and defective product reference data. The calculation unit 531 may determine the quality of the shape of the convex portion C of the object surface OS as an inspection of the quality of the riblet structure by comparing the data representing the intensity distribution output from the light receiving element 3 with at least one of good product reference data and defective product reference data.

[0182] The good-quality reference data is data that represents the intensity distribution of light (at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2) reflected by irradiating light onto an object surface OS having a riblet structure (convex portion C and region R) that has been determined to be good-quality. The defective-quality reference data is data that represents the intensity distribution of light (at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2) reflected by irradiating light onto an object surface OS having a riblet structure (convex portion C and region R) that has been determined to be defective.

[0183] At least one of the at least one good product reference data and the at least one defective product reference data can also be considered as reference data for inspecting the quality of the riblet structure. At least one of the at least one good product reference data and the at least one defective product reference data may be stored in advance in the memory 52.

[0184] For example, the non-defective reference data may include data representing the intensity distribution of light reflected by irradiating light onto an object surface OS having a convex portion C whose shape is determined to be non-defective due to the rounded apex of the convex portion C. For example, the non-defective reference data may include data representing the intensity distribution of light reflected by irradiating light onto an object surface OS having a convex portion C whose shape is determined to be non-defective due to the symmetry of the convex portion C (symmetry of the inclined surfaces T1 and T2 with respect to the third direction D3). For example, the non-defective reference data may include data representing the intensity distribution of light reflected by irradiating light onto an object surface OS having a convex portion C whose shape is determined to be non-defective due to the apex angle A. For example, the non-defective reference data may include data representing the intensity distribution of light reflected by irradiating light onto an object surface OS having a convex portion C whose shape is determined to be non-defective due to the height H of the convex portion C. For example, the good product reference data may include data representing the intensity distribution of light reflected by irradiating light onto an object surface OS having a convex portion C whose shape is judged to be good product, with a spacing P in the second direction D2 as the shape of the convex portion C.

[0185] The calculation unit 531 may compare the data representing the intensity distribution output from the light-receiving element 3 with the above-mentioned non-defective standard data to determine the acceptability of at least one of the following as the shape of the convex portions C: the rounding of the apexes of the convex portions C, the symmetry of the convex portions C, the apex angle A of the convex portions C, the height H of the convex portions C, and the spacing P of the convex portions C in the second direction D2. For example, when the data representing the intensity distribution output from the light-receiving element 3 differs from the above-mentioned non-defective standard data (i.e., when the intensity distribution output from the light-receiving element 3 differs from the intensity distribution represented by the non-defective standard data), the calculation unit 531 may determine that the shape of the convex portions C is defective.

[0186] In addition, similar to the good product reference data, the defective product reference data may include data representing the respective intensity distributions of light reflected by irradiating light onto an object surface OS having convex portions C that are judged to be defective in terms of the shape of the convex portions C, the rounding of the apexes of the convex portions C, the symmetry of the convex portions C, the apex angle A of the convex portions C, the height H of the convex portions C, and the spacing P of the convex portions C in the second direction D2.

[0187] The calculation unit 531 may compare the data representing the intensity distribution output from the light-receiving element 3 with the above-mentioned defective product reference data to determine the acceptability of at least one of the following as the shape of the convex portions C: the rounding of the apexes of the convex portions C, the symmetry of the convex portions C, the apex angle A of the convex portions C, the height H of the convex portions C, and the spacing P of the convex portions C in the second direction D2. For example, the calculation unit 531 may determine that the shape of the convex portions C is defective when the data representing the intensity distribution output from the light-receiving element 3 is the same as the above-mentioned defective product reference data (i.e., when the intensity distribution output from the light-receiving element 3 is the same as the intensity distribution represented by the defective product reference data).

[0188] The calculation unit 531 may identify a virtual line HL1 from the positions of the region corresponding to the first reflected light RL1 and the region corresponding to the second reflected light RL2 in the data representing the intensity distribution output from the light receiving element 3 (on the image represented by the intensity distribution data), and create a luminance profile representing the luminance of pixels along the virtual line HL1. The calculation unit 531 may then determine whether the shape of the convex portion C is good or bad by comparing the luminance profile created using the received light data with a luminance profile similarly created from non-defective reference data and / or a luminance profile similarly created from defective reference data.

[0189] The non-defective reference data and the defective reference data are data representing the intensity distribution output by the optical device 1 of this embodiment actually irradiating light onto an object surface OS having a riblet structure whose shape has been determined in advance. The non-defective reference data and the defective reference data may also be data calculated using a simulation such as a ray tracing method. For example, the non-defective reference data and the defective reference data may be simulation data representing the intensity distribution of reflected light that is collected when light is irradiated onto an object surface OS having a riblet structure whose shape has been determined in advance.

[0190] The calculation unit 531 may determine whether the shape of the riblet structure on the object surface OS is good or bad by inputting data representing the intensity distribution output from the light receiving element 3 (data based on reflected light from the riblet structure to be inspected) into an identifier that has been pre-trained to determine whether the shape of the riblet structure represented in the input data is good or bad.

[0191] The classifier can be, for example, a convolutional neural network (hereinafter referred to as "CNN") having multiple convolution layers connected in series from the input side to the output side. By inputting a large amount of non-defective reference data and a large amount of defective reference data into the CNN using training data to perform pre-learning, the CNN operates as a classifier that determines whether the shape of a riblet structure is good or bad.

[0192] In addition, the identifier may be pre-trained to input data representing the intensity distribution output from the light receiving element 3 (data based on reflected light from the riblet structure of the object to be inspected) and output a pass / fail judgment result for at least one of the shape of the convex portion C, the rounding of the apex of the convex portion C, the symmetry of the convex portion C, the apex angle A of the convex portion C, the height H of the convex portion C, and the spacing P of the convex portion C in the second direction D2.

[0193] The calculation unit 531 inputs data representing the intensity distribution output from the light receiving element 3 into the above-mentioned classifier, and obtains a pass / fail judgment result output from the classifier, the pass / fail judgment result being at least one of the rounding of the apexes of the convex portions C, the symmetry of the convex portions C, the apex angle A of the convex portions C, the height H of the convex portions C, and the spacing P of the convex portions C in the second direction D2. By obtaining the above-mentioned pass / fail judgment results, the calculation unit 531 can be said to judge the pass / fail of the shape of the convex portions C.

[0194] The classifier may be trained to judge the acceptability of the shape of region R by inputting data representing the intensity distribution output from the light receiving element 3 (data based on light reflected from the riblet structure of the inspection target). The calculation unit 531 may acquire a judgment result as to the acceptability of the shape of region R, which is output from the classifier, by inputting data representing the intensity distribution output from the light receiving element 3 (data based on light reflected from the riblet structure of the inspection target) into the above-mentioned classifier.

[0195] The detection unit 532 may detect the relative inclination of the optical axis AX of the focusing optical system 2 with respect to the object surface OS based on the distance between the position of the first reflected light RL1 (on the image represented by the intensity distribution data) in the data representing the intensity distribution output from the light receiving element 3 and the reference position RP.

[0196] The reference position RP represents the position on the light receiving surface 3a where light that is incident parallel to the optical axis AX of the focusing optical system 2 and is reflected once at the object surface OS (e.g., at region R) when the normal direction of the object surface OS (e.g., the normal direction of region R) is parallel to the optical axis AX of the focusing optical system 2 is focused by the focusing optical system 2.

[0197] The focusing optical system 2 is installed on a reference plane so that the optical axis AX is perpendicular to the reference plane. The reference position RP can be a position on the light-receiving surface 3a where light irradiated perpendicularly to the reference plane is focused by the focusing optical system 2. For example, the reference position RP can be set using a collimator.

[0198] FIG. 11 is a schematic diagram showing the second light reception data.

[0199] In the second light reception data RD2 (on the image represented by the intensity distribution data), which is another example of light reception data, the first reflected light RL1 and the second reflected lights RL2-1 and RL2-2 are represented at positions along a virtual line HL2. The virtual line HL2 is spaced apart from the reference position RP by a distance G1. That is, the first reflected light RL1 is represented at a position spaced apart from the reference position RP by the distance G1. Furthermore, the pair of second reflected lights RL2-1 and RL2-2 are represented at positions spaced apart from each other by a distance G2.

[0200] The detection unit 532 may detect that the greater the distance G1 between the position of the first reflected light RL1 and the reference position RP on the image represented by the intensity distribution data, the greater the inclination of the optical axis AX of the focusing optical system 2 with respect to the object surface OS.

[0201] The relationship between the distance G1 and the tilt of the optical axis AX of the focusing optical system 2 with respect to the object surface OS may be determined in advance. In this case, the detection unit 532 may calculate the tilt of the optical axis AX of the focusing optical system 2 with respect to the object surface OS based on the distance G1 between the position of the first reflected light RL1 and the reference position RP on the image represented by the intensity distribution data.

[0202] The detection unit 532 may also detect the tilt direction of the optical axis AX of the focusing optical system 2 relative to the object surface OS, depending on the position of the first reflected light RL1 relative to the reference position RP on the image represented by the intensity distribution data.

[0203] In the second received light data RD2 (on the image represented by the intensity distribution data), the first reflected light RL1 is spaced from the reference position RP in a direction perpendicular to a virtual line HL2 that is perpendicular to a first direction D1 along which the convex portions C are connected on the object surface OS. In this case, the detection unit 532 may detect that the optical axis of the focusing optical system 2 is tilted along the first direction D1 with respect to the object surface OS. In other words, the detection unit 532 may detect the direction in which the optical axis of the focusing optical system 2 is tilted with respect to the object surface OS.

[0204] The above-described processing of the detection unit 532 may be executed by the calculation unit 531. The optical device 1 may not necessarily include the detection unit 532.

[0205] The measurement unit 533 measures a measurement surface having a riblet structure. The object surface OS is an example of a measurement surface that is the target of measurement by the measurement unit 533. The measurement unit 533 outputs a value related to the shape of the riblet structure of the object surface OS based on the light reception data corresponding to the object surface OS.

[0206] The light reception data corresponding to the object surface OS is data that represents the result of receiving light (e.g., at least one of the first reflected light RL1 and the second reflected light) that is reflected in the irradiation area IR and collected by the focusing optical system 2 when light from the focusing optical system 2 is irradiated onto the irradiation area IR of the object surface OS.

[0207] The data representing the result of light reception can also be said to be data representing the intensity distribution of the light (for example, at least one of the first reflected light RL1 and the second reflected light) collected by the light collecting optical system 2. The data representing the intensity distribution may be two-dimensional image data.

[0208] The data representing the intensity distribution output from the light receiving element 3 can also be said to be data based on light reflected from the riblet structure of the measurement target. The light receiving element 3 may be an element such as a line sensor having pixels arranged one-dimensionally, and the data representing the intensity distribution may be one-dimensional image data.

[0209] That is, the measurement unit 533 measures the riblet structure based on the intensity distribution data output from the light receiving element 3.

[0210] The measuring unit 533 may calculate values ​​related to the shape of the riblet structure as measurements of the riblet structure based on the intensity distribution data output from the light receiving element 3. For example, the measuring unit 533 may calculate values ​​representing at least one of the apex angle A of the convex portion C, the height H of the convex portion C, the radius of curvature at the apex of the convex portion C, the curvature of the apex of the convex portion C, and the spacing P of the convex portions in the second direction as values ​​related to the shape of the riblet structure.

[0211] The measurement unit 533 may calculate the distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2 on the light receiving surface 3 a of the light receiving element 3, and may calculate a value related to the shape of the riblet structure based on the calculated distance. For example, the measurement unit 533 may calculate a value representing the apex angle A of the convex portion C as a value related to the shape of the riblet structure based on the calculated distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2.

[0212] The distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2 that are incident on the light-receiving surface 3a after being reflected by the irradiation region IR due to irradiation with light increases as the apex angle A of the convex portion C increases. Therefore, the apex angle A of the convex portion C can be calculated based on the distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2 that are incident on the light-receiving surface 3a.

[0213] Similar to the processing of the calculation unit 531 described above, the measurement unit 533 identifies an area corresponding to the second reflected light RL2-1 and an area corresponding to the second reflected light RL2-2 in the data representing the intensity distribution output from the light receiving element 3 (on the image represented by the intensity distribution data). For example, the measurement unit 533 may extract pixels whose luminance values ​​are equal to or greater than a predetermined threshold on the image represented by the intensity distribution data, and cluster and group the extracted pixel sets to identify an area corresponding to the second reflected light RL2-1 and an area corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution data. Note that the measurement unit 533 may also use template matching to identify an area corresponding to the second reflected light RL2-1 and an area corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution data.

[0214] Similar to the processing by the calculation unit 531 described above, the measurement unit 533 calculates, for each of the identified regions corresponding to the second reflected light RL2-1 and the second reflected light RL2-2 on the image represented by the intensity distribution data, at least one of the position of the pixel having the maximum brightness and the position of the geometric center of gravity of the region as a representative position of the reflected light. Note that the position corresponding to the second reflected light RL2-1 on the image represented by the intensity distribution data calculated by the measurement unit 533 (the representative position of the second reflected light RL2-1) represents the incident position of the second reflected light RL2-1 on the light-receiving surface 3a. Also, the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution data calculated by the measurement unit 533 (the representative position of the second reflected light RL2-2) represents the incident position of the second reflected light RL2-2 on the light-receiving surface 3a.

[0215] Then, similar to the processing of the calculation unit 531 described above, the measurement unit 533 calculates the distance between the position corresponding to the second reflected light RL2-1 and the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution, based on the identified position corresponding to the second reflected light RL2-1 (representative position of the second reflected light RL2-1) and the position corresponding to the second reflected light RL2-2 (representative position of the second reflected light RL2-2) on the image represented by the intensity distribution data.

[0216] The distance between the position corresponding to the second reflected light RL2-1 and the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution represents the distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2 on the light receiving surface 3a. The distance between the position corresponding to the second reflected light RL2-1 and the position corresponding to the second reflected light RL2-2 on the image represented by the intensity distribution is, for example, the distance represented by the distance G2 in FIG.

[0217] Furthermore, it is also possible to obtain in advance data relating to the distance between the incident position of the second reflected light RL2-1 and the incident position of the second reflected light RL2-2 incident on the light receiving surface 3a, and the apex angle A of the convex portion C. This data relating to the distance between the second reflected light RL2 and the apex angle A of the convex portion C may be function data or table data such as a look-up table.

[0218] The relationship data between the spacing of this second reflected light RL2 and the apex angle A of the convex portion C can also be considered reference data for measuring the riblet structure. The reference data for measuring the riblet structure may be stored in memory 52. ​​The reference data for measuring the riblet structure can also be considered standard data for measuring the riblet structure.

[0219] The measurement unit 533 may calculate a value representing the apex angle A of the convex portion C as a value related to the shape of the riblet structure, based on the calculated distance between the incident position of the second reflected light RL2-1 and the incident position of RL2-2 and the reference data for measuring the riblet structure. For example, the measurement unit 533 may calculate a value representing the apex angle A of the convex portion C corresponding to the distance between the incident position of the second reflected light RL2-1 and the incident position of RL2-2 by referring to the reference data for measuring the riblet structure.

[0220] It should be noted that the object to be measured by the measuring unit 533 (the object for calculating a value related to the shape) is not limited to the apex angle A of the convex portion C. For example, the measuring unit 533 may use the above-described processing to calculate at least one value of the shape of the riblet structure, including the height H of the convex portion C, the radius of curvature of the apex of the convex portion C, the curvature of the apex of the convex portion C, and the spacing P of the convex portion C in the second direction D2.

[0221] In addition, the measurement unit 533 may also measure the riblet structure using the intensity of light emitted from the light source LS, which is output from the above-mentioned light intensity measurement device.

[0222] In addition, the measurement unit 533 may calculate a value related to the shape of the riblet structure based on the distance between the incident position of one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2 on the light receiving surface 3a and the incident position of another of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2 on the light receiving surface 3a, rather than being limited to the distance between the second reflected light RL2-1 and the second reflected light RL2-2 on the light receiving surface 3a.

[0223] It is to be noted that reference data for measuring the riblet structure (data relating to the distance between the incident position of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2 on one light-receiving surface 3a and the incident position on another light-receiving surface 3a, and the shape of the riblet structure) may be obtained in advance using a method similar to that described above. In this case, the measurement unit 533 may calculate a value relating to the shape of the riblet structure based on the distance between the incident position of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2 on one light-receiving surface 3a and the incident position on another light-receiving surface 3a, and the reference data for measuring the riblet structure. It is to be noted that the process relating to the calculation of the distance between the incident positions of the reflected light can use the process of the calculation unit 531 or the measurement unit 533 described above.

[0224] In addition, the measurement unit 533 may calculate values ​​related to the shape of the riblet structure based on the incident position of at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2 on the light receiving surface 3a.

[0225] It is to be noted that reference data for measuring the riblet structure (data relating the relationship between the incident position of at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2 and the shape of the riblet structure) may be obtained in advance using a method similar to that described above. In this case, the measurement unit 533 may calculate a value relating to the shape of the riblet structure based on the incident position of at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2 and the reference data for measuring the riblet structure. It is to be noted that the processing related to the calculation of the incident position of the reflected light can use the processing of the calculation unit 531 or the measurement unit 533 described above.

[0226] In addition, the measurement unit 533 may calculate a value related to the shape of the riblet structure based on the intensity of the first reflected light RL1 and at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2.

[0227] It is to be noted that reference data for measuring the riblet structure (data relating to the relationship between the first reflected light RL1 and the intensity of at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2, and the shape of the riblet structure) may be obtained in advance using a method similar to that described above. In this case, the measurement unit 533 may calculate a value relating to the shape of the riblet structure based on the intensity of at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light 2-2, and the reference data for measuring the riblet structure. It is to be noted that the processing related to the calculation of the intensity of the reflected light can use the processing of the calculation unit 531 described above.

[0228] The measurement unit 533 may calculate a value related to the shape of the riblet structure by comparing data representing the intensity distribution output from the light receiving element 3 with a plurality of shape reference data. The plurality of shape reference data are a plurality of data representing the intensity distribution of light (for example, at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2) reflected by irradiating light onto an object surface OS having a plurality of riblet structures each having a different shape. The plurality of shape reference data are stored in advance in the memory 52.

[0229] For example, the measurement unit 533 may identify, from among multiple shape reference data, data (intensity distribution represented by the shape reference data) that is the same as or similar to the data representing the intensity distribution output from the light receiving element 3 (intensity distribution represented by the data output from the light receiving element 3), and calculate the shape value corresponding to the identified data.

[0230] The plurality of shape reference data can also be considered as reference data for measuring the riblet structure. For example, the plurality of shape reference data may be a plurality of data representing the intensity distribution of light (for example, at least one of the first reflected light RL1, the second reflected light RL2-1, and the second reflected light RL2-2) reflected by irradiating light onto an object surface OS having a plurality of riblet structures each having a different shape with respect to at least one of the following as the shape of the riblet structure: the apex angle A of the convex portion C, the height H of the convex portion C, the radius of curvature of the apex of the convex portion C, the curvature of the apex of the convex portion C, and the spacing P of the convex portion C in the second direction D2.

[0231] The measuring unit 533 may calculate values ​​for at least one of the following as the shape of the riblet structure: the apex angle A of the convex portion C, the height H of the convex portion C, the radius of curvature of the apex of the convex portion C, the curvature of the apex of the convex portion C, and the spacing P of the convex portion C in the second direction D2, by comparing the data representing the intensity distribution output from the light receiving element 3 with multiple shape reference data.

[0232] The above-mentioned shape reference data is data that represents the intensity distribution of light that is reflected from the object surface OS and collected by the collecting optical system 2 when light is actually irradiated onto the object surface OS having a riblet structure of a predetermined shape. The shape reference data may also be data calculated using a simulation such as a ray tracing method. For example, the shape reference data may be simulation data that represents the intensity distribution of the reflected light that is collected when light is irradiated onto the object surface OS having a riblet structure of a predetermined shape. Multiple shape reference data may be created by obtaining data that represents the intensity distribution when the shape of the riblet structure is changed through simulation.

[0233] The measurement unit 533 may output values ​​related to the shape of the riblet structure by inputting data representing the intensity distribution output from the light-receiving element 3 into a classifier that has been trained in advance to output values ​​related to the shape of the riblet structure of the object surface OS represented by the input data. The classifier may be, for example, a CNN. Shape reference data corresponding to various shapes of the riblet structure and values ​​related to the shape of the riblet structure corresponding to each shape reference data are input to the CNN as training data to perform training in advance, so that the CNN operates as a classifier that outputs values ​​related to the shape of the riblet structure.

[0234] For example, the classifier may be trained in advance to output a calculation result of at least one value of the shape of the riblet structure, which is the apex angle A of the convex portions C, the height H of the convex portions C, the radius of curvature of the apex of the convex portions C, the curvature of the apex of the convex portions C, and the spacing P of the convex portions C in the second direction D2, by inputting data representing the intensity distribution output from the light receiving element 3. The measurement unit 533 inputs data representing the intensity distribution output from the light receiving element 3 to the above-mentioned classifier, and acquires a calculation result of at least one value output from the classifier, which is the apex angle A of the convex portions C, the height H of the convex portions C, the radius of curvature of the apex of the convex portions C, the curvature of the apex of the convex portions C, and the spacing P of the convex portions C in the second direction D2. By acquiring the calculation result, it can be said that the measurement unit 533 has calculated a value related to the shape of the riblet structure.

[0235] The processing related to the measurement of the riblet structure by the measurement unit 533 may be executed by the calculation unit 531. For example, the measurement unit 533 may also have the function of the calculation unit 531. In this case, the calculation unit 531 may execute the processing related to the measurement of the riblet structure. For example, the calculation unit 531 may execute the processing related to the measurement of the riblet structure in addition to the processing related to the inspection of the riblet structure. For example, the calculation unit 531 may calculate a value related to the shape of the riblet structure in addition to the processing related to the inspection of the riblet structure or as part of the processing related to the measurement of the riblet structure. The calculation unit 531 may calculate the value related to the shape of the riblet structure as an inspection result of the riblet structure. The processing related to the detection of the tilt of the optical axis AX of the focusing optical system 2 with respect to the object surface OS by the detection unit 532 may be executed by the calculation unit 531.

[0236] The processing related to the inspection of the riblet structure by the calculation unit 531 may be executed by the measurement unit 533. The processing related to the detection of the tilt of the optical axis AX of the focusing optical system 2 with respect to the object surface OS by the detection unit 532 may be executed by the measurement unit 533.

[0237] 12 is a flowchart of the inspection process for the riblet structure. The optical device 1 executes the inspection process for the object surface OS on which the riblet structure is formed, in accordance with the following flowchart.

[0238] The optical device 1 irradiates light from the focusing optical system 2 onto an inspection surface (object surface OS) having a riblet structure (step S11).

[0239] Next, the optical device 1 uses the focusing optical system 2 to focus the first reflected light RL1 that has been reflected once at a region R where the convex portion C of the irradiation region IR is not provided, and the second reflected light RL2 that has been reflected at least once at the inclined surface T of the convex portion C and the region R (step S12).

[0240] Next, the optical device 1 receives the condensed light with the light receiving element 3, which is disposed on a plane other than the plane conjugate with the surface to be inspected with respect to the condensing optical system 2 (step S13).

[0241] Then, the computer 5, which is communicatively connected to the optical device 1, inspects the riblet structure (inspected surface) based on the light reception result (data representing the intensity distribution) (step S14), and ends the inspection process. For example, as described above, the computer 5 (calculation unit 531) determines whether the shape of the riblet structure is good or bad.

[0242] By performing the inspection process in this manner, the optical device 1 can easily inspect the riblet structure.

[0243] The processor 53 included in the computer 5 communicatively connected to the optical device 1 may not have some of the functional blocks of the calculation unit 531, the detection unit 532, and the measurement unit 533. For example, when the computer 5 includes a processor 53 having at least the measurement unit 533 as a functional block, the optical device 1 can operate as a device that measures a riblet structure formed on the surface of an object. For example, when the computer 5 includes a processor 53 having at least the calculation unit 531 as a functional block, the optical device 1 can operate as a device that inspects a riblet structure formed on the surface of an object.

[0244] 13 is a flowchart of the process of measuring the riblet structure. The optical device 1 executes the process of measuring the riblet structure formed on the object surface OS in accordance with the following flowchart.

[0245] In the flowchart of the riblet structure measurement process, steps S21-S23 are the same as steps S11-S13 of the riblet structure inspection process, so their explanation will be omitted.

[0246] Following step S23, the computer 5 communicatively connected to the optical device 1 measures the riblet structure based on the light reception result (data representing the intensity distribution) (step S24), and ends the measurement process. For example, as described above, the computer 5 (measurement unit 533) calculates values ​​related to the shape of the riblet structure.

[0247] By performing the measurement process in this manner, the optical device 1 can easily measure the riblet structure.

[0248] The optical device 1 described above may be attached to a movable body. Examples of movable bodies include robots such as vertical articulated robots, gimbals, manned / unmanned aerial vehicles, and manned / unmanned vehicles. In this case, the movable body to which the optical device 1 is attached may position the optical device 1 relative to the object surface OS, and perform at least one of the above-described inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 (the focusing optical system 2) relative to the object surface OS. For example, the movable body may abut (position) the abutting member 4a of the optical device 1 against the object surface OS, and perform at least one of the above-described inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 relative to the object surface OS.

[0249] The abutment member 4a of the optical device 1 does not have to abut against the object surface OS. For example, the optical device 1 may be positioned by a movable body so that the abutment member 4a is located at a position away from the object surface OS, and at least one of the above-described inspection of the riblet structure, measurement of the riblet structure, and detection of the tilt of the optical device 1 with respect to the object surface OS may be performed. In this case, the optical device 1 does not have to include the abutment member 4a.

[0250] In addition, while moving the optical device 1 on the object surface OS using a movable body, the optical device 1 may perform at least one of the above-mentioned inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 relative to the object surface OS.

[0251] The optical device 1 does not have to be attached to a movable body. For example, an operator may position the optical device 1 (e.g., the housing 4) held by hand with respect to the object surface OS, and use the optical device 1 to perform at least one of the above-described inspection of the riblet structure, measurement of the riblet structure, and detection of the tilt of the optical device 1 (the focusing optical system 2) with respect to the object surface OS.

[0252] For example, an operator may abut the abutment member 4a of the optical device 1 held in his / her hand against the object surface OS to perform at least one of the above-mentioned inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 relative to the object surface OS.

[0253] The abutment member 4a of the optical device 1 does not have to abut against the object surface OS. For example, an operator may position the optical device 1 held by hand so that the abutment member 4a is located at a position away from the object surface OS, and use the optical device 1 to perform at least one of the above-described inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 relative to the object surface OS. In this case, the optical device 1 does not need to be equipped with the abutment member 4a.

[0254] In addition, the operator may move the optical device 1 held in his / her hand over the object surface OS, and use the optical device 1 to perform at least one of the above-mentioned inspection of the riblet structure, measurement of the riblet structure, and detection of the inclination of the optical device 1 relative to the object surface OS.

[0255] At least one of inspection and measurement of the riblet structure may be performed using the optical device 1 described above and another optical device. For example, inspection and measurement of the riblet structure may be performed using the optical device 1 and a white light interference microscope as another optical device. In this case, the optical device 1 may perform at least one of inspection of the riblet structure (e.g., determining whether the symmetry of the convex portions C is good or bad) and measurement of the riblet structure (e.g., calculating the apex angle A of the convex portions C) as described above based on intensity distribution data from the second reflected light RL2-1 and / or the second reflected light RL2-2 acquired by the light receiving element 3. The white light interference microscope may perform at least one of inspection of the riblet structure (e.g., determining whether the spacing P of the convex portions C is good or bad) and measurement of the riblet structure (e.g., calculating the height H of the convex portions C) based on the results of detecting light from the object surface OS generated by irradiating the object surface OS with measurement light.

[0256] The other optical device is not limited to a white light interference microscope, but may be a confocal microscope or another existing device capable of at least one of inspecting and measuring an object.

[0257] In the above description, the optical device 1 inspects and / or measures the riblet structure formed on the surface of the workpiece. However, the optical device 1 may inspect and / or measure any structure having any shape formed on the surface of the workpiece.

[0258] An example of the arbitrary structure is a structure that generates vortices in the flow of a fluid on the surface of the workpiece. Another example of the arbitrary structure is a structure that imparts hydrophobicity to the surface of the workpiece. Another example of the arbitrary structure is a regularly or irregularly formed fine texture structure on the order of micrometers or nanometers (typically, a concave-convex structure including a ridge structure and a groove structure).

[0259] The fine texture structure may include at least one of a shark skin structure and a dimple structure that have a function of reducing resistance due to fluids (gas and / or liquids).The fine texture structure may include a lotus leaf surface structure that has at least one of a liquid repellent function and a self-cleaning function (for example, having a lotus effect).

[0260] The fine texture structure may include at least one of a micro-protrusion structure having a liquid transport function (see U.S. Patent Publication No. 2017 / 0044002), a concave-convex structure having a lyophilic function, a concave-convex structure having an anti-fouling function, a moth-eye structure having at least one of a reflectance reducing function and a liquid repellent function, a concave-convex structure that exhibits a structural color by intensifying only light of a specific wavelength through interference, a pillar array structure having an adhesive function utilizing van der Waals forces, a concave-convex structure having an aerodynamic noise reducing function, a honeycomb structure having a droplet collecting function, a concave-convex structure that improves adhesion with a layer formed on the surface, a concave-convex structure for reducing frictional resistance, a concave-convex structure for reducing icing, and the like.

[0261] Even in this case, the convex structures constituting the concave-convex structure may have a structure similar to the convex portions constituting the above-mentioned riblet structure. The groove structure constituting the concave-convex structure may have a structure similar to the region R constituting the above-mentioned riblet structure. The fine texture structure does not have to have a specific function.

[0262] FIG. 14 is a schematic diagram showing the configuration of an optical device according to a modified example.

[0263] The optical device 6 according to the modified example includes a light-collecting optical system 7 and a light-receiving element 8 housed in a housing 9, and is electrically connected to a computer 10. The light-receiving element 8, housing 9, and computer 10 have the same configurations as the light-receiving element 3, housing 4, and computer 10 in the optical device 1.

[0264] The focusing optical system 7 includes a lens group 71 having one or more lens elements, a light splitting member 72, and a quarter-wave plate 73. A filter FL for protecting the light receiving element 3 is disposed between the light splitting member 72 and the light receiving element 8. The lens group 71 is appropriately designed to have the same function as the lens group 21 in the focusing optical system 2 of the optical device 1, and includes, for example, a positive meniscus lens L4, a positive lens L5, and a positive meniscus lens L6.

[0265] The light splitting member 72 has an optical thin film TF' that reflects or transmits incident light depending on its polarization state (for example, reflecting the s-polarized component of the incident light and transmitting the p-polarized component). The optical thin film TF' is provided on the optical axis AX of the light collecting optical system 7 so that at least a portion of the light beam of the first reflected light RL1 that has entered the light splitting member 22 is incident on the optical thin film TF'. The light splitting member 72 may be included in the light collecting optical system 7.

[0266] The incident light IL1 incident on the irradiation region IR from the light splitting member 72 is linearly polarized by the optical thin film TF'. The optical thin film TF' may be provided in a region of the light splitting member 72 that does not correspond to the optical path of the second reflected light RL2. The light splitting member 72 having the optical thin film TF' may be configured as a polarizing beam splitter.

[0267] The quarter-wave plate 73 is disposed along the optical axis AX of the focusing optical system 7, closer to the irradiation region IR than the light splitting member 72, so as to transmit at least the incident light IL1 emitted from the light source LS, reflected by the light splitting member 72, and directed toward the irradiation region IR, and the first reflected light RL1 reflected by the irradiation region IR. Furthermore, the quarter-wave plate 73 may be sized to also transmit the second reflected light RL2 from the irradiation region IR. In the optical device 6, the quarter-wave plate 73 is disposed between the positive lens L5 and the positive meniscus lens L6 in the lens group 71 of the focusing optical system 7. In this case, it can be said that the focusing optical system 7 includes the quarter-wave plate 73. The quarter-wave plate 73 is supported by the housing 9 and disposed so that the slow axis of the quarter-wave plate 73 forms a predetermined angle with respect to the polarization direction of the linearly polarized incident light IL1. The position of the quarter-wave plate 73 is not limited to this example, and may be provided at any position between the light splitting member 72 and the irradiation region IR.

[0268] When the quarter-wave plate 73 is positioned so that the slow axis of the quarter-wave plate 73 is at 45 degrees with respect to the polarization direction of the incident light IL1, the incident light IL1 transmitted from the quarter-wave plate 73 toward the irradiation region IR becomes circularly polarized light. The circularly polarized incident light IL1 is reflected once by region R of the irradiation region IR to obtain first reflected light RL1, which becomes circularly polarized light with a rotation direction opposite to that of the incident light IL1 and enters the quarter-wave plate 73 again. The first reflected light RL1 transmitted through the quarter-wave plate 73 becomes linearly polarized light with a polarization direction that differs by 90 degrees from that of the linearly polarized light in the incident light IL1. The first reflected light RL1, which has transmitted through the quarter-wave plate 73 and become linearly polarized light, passes through the optical thin film TF′ of the light splitting member 72 and proceeds toward the light receiving element 8.

[0269] When the quarter-wave plate 73 is positioned so that the slow axis of the quarter-wave plate 73 forms an angle other than 45 degrees with respect to the polarization direction of the incident light IL1, the incident light IL1 transmitted from the quarter-wave plate 73 toward the irradiation region IR becomes elliptically polarized light. The elliptically polarized incident light IL1 is reflected once by region R of the irradiation region IR, resulting in first reflected light RL1, which becomes elliptically polarized light with an opposite rotation direction and re-enters the quarter-wave plate 73. The first reflected light RL1 transmitted through the quarter-wave plate 73 does not become linearly polarized light but becomes elliptically polarized light with a different polarization state. Therefore, a portion of the first reflected light RL1 incident on the optical thin film TF' is transmitted through the optical thin film TF', and the remainder is reflected by the optical thin film TF'. In this way, when the quarter-wave plate 73 is positioned so that the slow axis of the quarter-wave plate 73 is at an angle other than 45 degrees to the polarization direction of the incident light IL1, the amount of light of the first reflected light RL1 that enters the light receiving element 8 from the irradiation area IR via the optical thin film TF can be reduced.

[0270] The second reflected light RL2 that has been reflected at least twice by the irradiation region IR reaches the light receiving element 8 via the quarter-wave plate 73 and the light splitting member 72. At this time, at least a portion of the second reflected light RL2 passes through an area of ​​the light splitting member 72 where the optical thin film TF′ is not provided. Therefore, the amount of light of at least a portion of the second reflected light RL2 is not reduced by the light splitting member 72 and the quarter-wave plate 73.

[0271] In this way, when the quarter-wave plate 73 is positioned so that its slow axis forms an angle other than 45 degrees with respect to the polarization direction of the incident light IL1, the amount of the first reflected light RL1 reaching the light-receiving element 8 decreases along its path, while the amount of the second reflected light RL2 does not decrease, changing the ratio between the amount of the first reflected light RL1 and the amount of the second reflected light RL2. Therefore, the light splitting member 72 and the quarter-wave plate 73 are examples of a light amount change member. The light-collecting optical system 7 may include a light amount change member. By using the light amount change member to reduce the difference in the amount of light between the first reflected light RL1 and the second reflected light RL2 incident on the light-receiving element 3, the amount of light of each of the first reflected light RL1 and the second reflected light RL2 can be adjusted to fall within the dynamic range of the light-receiving element 3. Note that the light amount change member changes the polarization state of light from the light source LS, and therefore can also be considered a member that changes the polarization state of light heading toward the illumination region IR from the polarization state of the incident light.

[0272] Furthermore, the quarter-wave plate 73 may be supported at its outer periphery on the housing 9 so as to be rotatable about an axis (e.g., the optical axis AX) along the optical axis AX of the lens group 71. By rotating the quarter-wave plate 73 about the optical axis AX, the angle of the slow axis of the quarter-wave plate 73 relative to the polarization direction of the incident light IL1 is changed. As a result, the polarization states of the incident light IL1, the first reflected light RL1, and the second reflected light RL2 that have passed through the quarter-wave plate 73 are changed, and the amount of reduction in the amount of the first reflected light RL1 traveling from the irradiation region IR to the light receiving element 8 via the optical thin film TF is changed. This changes the ratio between the amount of the first reflected light RL1 traveling from the irradiation region IR to the light receiving element 8 and the amount of the second reflected light RL2 traveling from the irradiation region IR to the light receiving element 8. By changing the ratio between the light intensity of the first reflected light RL1 and the light intensity of the second reflected light RL2 in this way, it is possible to make the light intensity of each of the first reflected light RL1 and the second reflected light RL2 on the light receiving surface 8a of the light receiving element 8 fall within the dynamic range of the light receiving element 8, depending on the riblet structure formed on the object surface OS. Note that the light intensity change member can change the polarization state of the light emitted from the light intensity change member (incident light IL1 emitted from the light intensity change member toward the irradiation region IR) from one polarization state to another by rotating the quarter-wave plate 73, and therefore can also be said to be a member that changes the polarization state of the light heading toward the irradiation region IR.

[0273] The optical thin film TF' may be provided in a region through which at least the remainder of the second reflected light RL2 passes. In this case, the position of the optical thin film TF' is set so that the reduction in the amount of the second reflected light RL2 is smaller than the reduction in the amount of the first reflected light RL1. By arranging the optical thin film TF' in this manner, it is possible to ensure that the light amounts of the first reflected light RL1 and the second reflected light RL2 fall within the dynamic range of the light receiving element 8.

[0274] The optical device 6 may have an actuator (not shown) that rotates the quarter-wave plate 73 around an axis along the optical axis AX. In this case, the processor 53 of the computer 5 may drive the actuator to rotate the quarter-wave plate 73 based on the light-receiving data RD acquired from the light-receiving element 8 so that the light amounts of the first reflected light RL1 and the second reflected light RL2 fall within the dynamic range of the light-receiving element 8.

[0275] The light quantity changing member is not limited to the light splitting member 72 and the quarter-wave plate 73, and may be other existing optical members. For example, the light quantity changing member may be the light splitting member 72 and a neutral density filter (not shown).

[0276] In this case, the neutral density filter may be disposed on the optical path of the first reflected light RL1. The neutral density filter does not have to be disposed on the optical path of the second reflected light RL2. That is, the neutral density filter may be disposed only on the optical path of the first reflected light RL1. Furthermore, the neutral density filter may be disposed so that a portion of the neutral density filter overlaps a portion of the optical path of the second reflected light RL2. The neutral density filter may be disposed so that a portion of the neutral density filter overlaps a portion of the optical path of the incident light IL1, as long as it is possible to reduce the amount of first reflected light RL1.

[0277] The neutral density filter may be disposed between the light receiving element 8 and the light splitting member 72. The neutral density filter may be disposed in any space between the light splitting member 72 and the positive meniscus lens L4, or may be included in the light collecting optical system 7.

[0278] When the light quantity changing member is the light splitting member 72 and a neutral density filter (not shown), the light splitting member 72 may be a polarizing beam splitter or a half mirror. When the light quantity changing member is the light splitting member 72 and a neutral density filter (not shown), the optical device 6 does not need to have the quarter-wave plate 73.

[0279] Furthermore, a polarizing plate (not shown) or a polarizing beam splitter (not shown) may be disposed between the light source LS and the light splitting member 72 so that the light from the light source LS becomes linearly polarized light having a polarization plane in the direction reflected by the optical thin film TF′. By making such linearly polarized light incident on the light splitting member 72, the optical device 6 can suppress light that is incident on the optical thin film TF′ from the light source LS and passes through the optical thin film TF′ (so-called stray light), and can suppress noise included in the data output from the light receiving element 8.

[0280] In the above-described embodiment and modified examples, the light from the light source LS is introduced into the focusing optical system using an optical fiber, but the light from the light source LS may also be introduced into the focusing optical system using a relay optical system (reimaging optical system). In this case, the light source image may be formed by the relay optical system so that the light source image is formed near the light splitting member, in other words, so that the light source image is formed at the position where the exit end of the optical fiber near the light splitting member was located. In this case, the light enters the light splitting member in a divergent state from the position where the exit end of the optical fiber near the light splitting member was located.

[0281] Here, the tilt component of the telecentricity of the focusing optical system may be changed by moving the entire relay optical system or the light source LS relative to the relay optical system in a direction intersecting the light emission direction, or by moving some optical elements of the relay optical system to move the position of the light source image in the optical axis direction, thereby changing the magnification component of the telecentricity of the focusing optical system.

[0282] When a relay optical system is used, the light from the light source LS may be introduced into the relay optical system using an optical fiber. Also, an aperture stop for determining the divergence angle of the light from the relay optical system, a bandpass filter for setting the wavelength of the light from the relay optical system to a predetermined wavelength range, etc. may be provided inside the relay optical system.

[0283] The following additional notes are provided regarding the above-described embodiment.

[0284] [Appendix A1] An optical device for inspecting a surface to be inspected, the surface having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be inspected with light from a light source and collects light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; and a light quantity changing member that changes the polarization state of light from the light source, changes the polarization state of first reflected light that is reflected by a portion of the irradiation area where no convex portions are provided and heads toward the light receiving element, and transmits a portion of the first reflected light depending on the polarization state of the first reflected light.

[0285] [Appendix A2] The optical device according to Appendix A1, wherein the light amount change member changes the polarization state of the light directed toward the illumination region.

[0286] [Appendix A3] The optical device according to appendix A1 or A2, wherein the light amount change member reduces the amount of the first reflected light.

[0287] [Appendix A4] The optical device according to Appendix A3, wherein the light amount change member does not reduce the amount of second reflected light that is reflected by the convex portion in the irradiation region and travels toward the light receiving element.

[0288] [Appendix A5] The optical device according to Appendix A4, wherein the second reflected light is reflected by the convex portion in the irradiation area and a portion in the irradiation area where the convex portion is not provided, and is directed toward the light receiving element.

[0289] [Appendix A6] The optical device described in any one of Appendices A1 to A5, wherein the light amount change member includes: a first member that is arranged on the optical path of the first reflected light and that changes the polarization state of light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and second reflected light that is reflected by the convex portion in the irradiation area and proceeds toward the light receiving element, and that changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0290] [Appendix A7] An optical device for inspecting a surface to be inspected, the surface having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be inspected with light from a light source and collects light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; a first member that is arranged on an optical path of first reflected light that is reflected by a portion of the irradiation area where no convex portions are provided and proceeds toward the light receiving element, and that changes the polarization state of the light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and second reflected light that is reflected by the convex portions in the irradiation area and proceeds toward the light receiving element, and that changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0291] [Appendix A8] The optical device according to any one of Appendices A6 to A7, wherein the first member is not disposed on an optical path of the second reflected light.

[0292] [Appendix A9] The optical device according to Appendix A8, wherein the second reflected light is reflected by the convex portion in the irradiation region and a portion in the irradiation region where the convex portion is not provided, and is directed toward the light receiving element.

[0293] [Appendix A10] The optical device described in any one of Appendices A6 to A9, wherein the first polarization state is linear polarization, and the first member transmits a portion of the first reflected light emitted from the second member according to the polarization state of the first reflected light, and emits the portion toward the light receiving element.

[0294] [Appendix A11] The optical device according to Appendix A10, wherein the second polarization state is elliptically polarized light.

[0295] [Appendix A12] The optical device according to any one of Appendices A6 to A11, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0296] [Appendix A13] The optical device according to any one of Appendices A6 to A12, wherein the second member is supported rotatably about an axis along the optical axis of the focusing optical system.

[0297] [Appendix A14] The optical device according to any one of Appendices A6 to A13, wherein the focusing optical system has the first member and the second member.

[0298] [Appendix A15] The optical device according to any one of Appendices A1 to A14, wherein the detection surface of the light receiving element is arranged on a plane other than a plane conjugate with the inspected surface with respect to the light collecting optical system.

[0299] [Appendix A16] The optical device according to any one of Appendices A1 to A15, further comprising a calculation unit that inspects the riblet structure based on the detection result by the light receiving element.

[0300] [Appendix B1] An inspection method for inspecting a surface to be inspected that has a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction that intersects with the first direction, the inspection method comprising: irradiating light onto an irradiation area on the surface to be inspected; collecting light reflected from the irradiation area by the irradiation of light using a collecting optical system; changing the ratio between the amount of first reflected light reflected from a portion of the irradiation area where no convex portions are provided and the amount of second reflected light reflected from the convex portions in the irradiation area; and inspecting the riblet structure based on the detection results of the collected light.

[0301] [Appendix B2] The inspection method according to Appendix B1, wherein the change involves changing the polarization state of the light directed toward the illumination region.

[0302] [Appendix B3] The inspection method according to appendix B1 or B2, wherein the change comprises reducing the amount of the first reflected light.

[0303] [Appendix B4] The inspection method according to Appendix B3, wherein the change does not reduce the amount of the second reflected light.

[0304] [Appendix B5] An inspection method according to any one of Appendices B1 to B4, wherein, in the modification, a first member arranged on the optical path of the first reflected light modifies the polarization state of the light from the light source to a first polarization state, and a second member arranged on the optical paths of both the first reflected light and the second reflected light modifies the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0305] [Appendix B6] The inspection method according to Appendix B5, wherein the first member is not disposed on an optical path of the second reflected light.

[0306] [Appendix B7] The inspection method described in Appendix B5 or B6, wherein the first polarization state is linear polarization, and in the change, the first member transmits a portion of the first reflected light depending on the polarization state of the first reflected light emitted from the second member.

[0307] [Appendix B8] The inspection method according to Appendix B7, wherein the second polarization state is elliptically polarized light.

[0308] [Appendix B9] The inspection method according to any one of Appendices B5 to B8, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0309] [Appendix B10] The inspection method according to any one of Appendices B5 to B9, wherein the second member is supported rotatably about an axis along the optical axis of the focusing optical system.

[0310] [Appendix B11] The inspection method according to any one of Appendices B1 to B10, wherein the second reflected light is reflected by the convex portion in the irradiation area and by a portion in the irradiation area where the convex portion is not provided, and is then incident on the focusing optical system.

[0311] [Appendix B12] The inspection method according to any one of Appendices B1 to B11, wherein the light collected by the light receiving element has a detection surface that is arranged on a plane different from the conjugate plane.

[0312] [Appendix B13] A computer program for inspection that causes a computer to execute the inspection method according to any one of Appendices B1 to B12.

[0313] [Appendix C1] An inspection method for inspecting a surface to be inspected that has a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction that intersects with the first direction, the inspection method including: changing the polarization state of light from a light source and irradiating light onto an irradiation area on the surface to be inspected; changing the polarization state of first reflected light reflected at a portion of the irradiation area where no convex portions are arranged; transmitting a portion of the first reflected light according to the polarization state of the first reflected light; collecting the transmitted light using a collecting optical system; detecting the collected light; and inspecting the riblet structure based on the detection results.

[0314] [Appendix C2] The inspection method according to Appendix C1, wherein the amount of the second reflected light that is reflected by the convex portion in the irradiation area and detected is not reduced.

[0315] [Appendix C3] An inspection method described in Appendix C1 or C2, in which a first member arranged on the optical path of the first reflected light changes the polarization state of light from the light source to a first polarization state, and a second member arranged on the optical paths of both the first reflected light and second reflected light reflected by the convex portion in the irradiation area and detected changes the light of the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0316] [Appendix C4] The optical device according to Appendix C3, wherein the first member is not disposed on an optical path of the second reflected light.

[0317] [Appendix C5] The inspection method described in Appendix C3 or C4, wherein the first polarization state is linear polarization, and in transmitting a portion of the first reflected light, the first member transmits a portion of the first reflected light depending on the polarization state of the first reflected light emitted from the second member.

[0318] [Appendix C6] The inspection method according to Appendix C5, wherein the second polarization state is elliptically polarized light.

[0319] [Appendix C7] The inspection method according to any one of Appendices C3 to C6, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0320] [Appendix C8] An inspection method according to any one of Appendices C1 to C7, wherein the second reflected light is reflected by the convex portion in the irradiation area and by a portion in the irradiation area where the convex portion is not provided, and then enters the focusing optical system.

[0321] [Appendix C9] The inspection method according to any one of Appendices C1 to C8, wherein the collected light is detected by a light receiving element having a detection surface arranged on a plane different from the conjugate plane.

[0322] [Appendix C10] A computer program for inspection that causes a computer to execute the inspection method according to any one of Appendices C1 to C9.

[0323] [Appendix D1] An optical device for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be measured with light from a light source and collects light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; and a light amount change member that can change the ratio between the amount of first reflected light reflected by a portion of the irradiation area where no convex portions are provided and heading toward the light receiving element, and the amount of second reflected light reflected by the convex portions in the irradiation area and heading toward the light receiving element.

[0324] [Appendix D2] The optical device according to appendix D1, wherein the light amount change member changes the polarization state of the light directed toward the illumination region.

[0325] [Appendix D3] The optical device according to appendix D1 or D2, wherein the light amount change member reduces the amount of the first reflected light.

[0326] [Appendix D4] The optical device according to appendix D3, wherein the light amount change member does not reduce the amount of the second reflected light.

[0327] [Appendix D5] The optical device described in any one of Appendices D1 to D4, wherein the light quantity change member has: a first member that is arranged on the optical path of the first reflected light and changes the polarization state of the light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and the second reflected light and changes the light with the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0328] [Appendix D6] An optical device for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are provided in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be measured with light from a light source and focuses the light reflected by the irradiation area; a light receiving element that detects the light focused by the focusing optical system; a first member that is arranged on an optical path of first reflected light that is reflected by a portion of the irradiation area where no convex portions are provided and heads toward the light receiving element, and that changes the polarization state of the light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and second reflected light that is reflected by the convex portions in the irradiation area and heads toward the light receiving element, and that changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0329] [Appendix D7] The optical device according to appendix D5 or D6, wherein the first member is not disposed on an optical path of the second reflected light.

[0330] [Appendix D8] An optical device described in any one of Appendices D5 to D7, wherein the first polarization state is linear polarization, and the first member transmits a portion of the first reflected light according to the polarization state of the first reflected light emitted from the second member and emits the portion toward the light receiving element.

[0331] [Appendix D9] The optical device according to appendix D8, wherein the second polarization state is elliptically polarized light.

[0332] [Appendix D10] The optical device according to any one of Appendices D5 to D9, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0333] [Appendix D11] The optical device according to any one of Appendices D5 to D10, wherein the second member is supported rotatably about an axis along the optical axis of the focusing optical system.

[0334] [Appendix D12] The optical device according to any one of Appendices D5 to D11, wherein the focusing optical system has the first member and the second member.

[0335] [Appendix D13] The optical device described in any one of Appendices D1 to D12, wherein the second reflected light is reflected by each of the convex portion in the irradiation area and a portion in the irradiation area where the convex portion is not provided, and then heads toward the light receiving element.

[0336] [Appendix D14] The optical device according to any one of Appendices D1 to D13, wherein the detection surface of the light receiving element is arranged on a plane other than a plane conjugate with the measurement surface with respect to the light collecting optical system.

[0337] [Appendix D15] An optical device described in any one of Appendices D1 to D14, further comprising a calculation unit that measures the riblet structure based on the detection result by the light receiving element.

[0338] [Appendix E1] An optical device for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be measured with light from a light source and collects the light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; and a light quantity changing member that changes the polarization state of light from the light source, changes the polarization state of first reflected light that is reflected by a part of the irradiation area where no convex portions are provided and heads toward the light receiving element, and transmits a portion of the first reflected light depending on the polarization state of the first reflected light.

[0339] [Appendix E2] The optical device according to Appendix E1, wherein the light amount change member changes the polarization state of the light directed toward the illumination region.

[0340] [Appendix E3] The optical device according to appendix E1 or E2, wherein the light amount change member reduces the amount of the first reflected light.

[0341] [Appendix E4] The optical device according to Appendix E3, wherein the light amount change member does not reduce the amount of second reflected light that is reflected by the convex portion in the irradiation region and travels toward the light receiving element.

[0342] [Appendix E5] The optical device described in Appendix E4, wherein the second reflected light is reflected by the convex portion in the irradiation area and by a portion in the irradiation area where the convex portion is not provided, and then travels toward the light receiving element.

[0343] [Appendix E6] The optical device described in any one of Appendices E1 to E5, wherein the light quantity change member has: a first member that is arranged on the optical path of the first reflected light and changes the polarization state of light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and second reflected light that is reflected by the convex portion in the irradiation area and heads toward the light receiving element and changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0344] [Appendix E7] An optical device for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are provided in a second direction intersecting the first direction, the optical device comprising: a focusing optical system that irradiates an irradiation area on the surface to be measured with light from a light source and collects light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; a first member that is arranged on an optical path of first reflected light that is reflected by a portion of the irradiation area where no convex portions are provided and proceeds toward the light receiving element, and that changes the polarization state of the light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and second reflected light that is reflected by the convex portions in the irradiation area and proceeds toward the light receiving element, and that changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0345] [Appendix E8] The optical device according to appendix E6 or E7, wherein the first member is not disposed on an optical path of the second reflected light.

[0346] [Appendix E9] The optical device described in Appendix E8, wherein the second reflected light is reflected by the convex portion in the irradiation area and by a portion in the irradiation area where the convex portion is not provided, and then travels toward the light receiving element.

[0347] [Appendix E10] An optical device described in any one of Appendices E6 to E9, wherein the first polarization state is linear polarization, and the first member transmits a portion of the first reflected light according to the polarization state of the first reflected light emitted from the second member and emits the portion toward the light receiving element.

[0348] [Appendix E11] The optical device according to appendix E10, wherein the second polarization state is elliptically polarized.

[0349] [Appendix E12] The optical device according to any one of appendices E6 to E11, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0350] [Appendix E13] The optical device according to any one of Appendices E6 to E12, wherein the second member is supported rotatably about an axis along the optical axis of the focusing optical system.

[0351] [Appendix E14] The optical device according to any one of Appendices E6 to E13, wherein the focusing optical system has the first member and the second member.

[0352] [Appendix E15] The optical device according to any one of appendices E1 to E14, wherein the detection surface of the light receiving element is arranged on a plane other than a plane conjugate with the measurement target surface with respect to the focusing optical system.

[0353] [Appendix E16] An optical device described in any one of Appendices E1 to E15, further comprising a calculation unit that measures the riblet structure based on the detection result by the light receiving element.

[0354] [Appendix F1] A measurement method for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the measurement method comprising: irradiating an irradiation area on the surface to be measured with light; collecting light reflected from the irradiation area by the irradiation with a collecting optical system; changing the ratio between the amount of first reflected light reflected from a portion of the irradiation area where the convex portions are not provided and the amount of second reflected light reflected from the convex portions in the irradiation area; and measuring the riblet structure based on the detection result of the collected light.

[0355] [Appendix F2] The measurement method according to appendix F1, wherein the change comprises changing the polarization state of the light directed toward the illumination region.

[0356] [Appendix F3] The measurement method according to appendix F1 or F2, wherein the change comprises reducing the amount of the first reflected light.

[0357] [Appendix F4] The measurement method according to Appendix F3, wherein the change does not reduce the amount of the second reflected light.

[0358] [Appendix F5] The measurement method described in any one of Appendices F1 to F4, wherein, in the change, a first member arranged on the optical path of the first reflected light changes the polarization state of the light from the light source to a first polarization state, and a second member arranged on the optical paths of both the first reflected light and the second reflected light changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0359] [Appendix F6] The measurement method according to Appendix F5, wherein the first member is not disposed on an optical path of the second reflected light.

[0360] [Appendix F7] The measurement method described in Appendix F5 or F6, wherein the first polarization state is linear polarization, and in the change, the first member transmits a portion of the first reflected light depending on the polarization state of the first reflected light emitted from the second member.

[0361] [Appendix F8] The measurement method according to appendix F7, wherein the second polarization state is elliptically polarized light.

[0362] [Appendix F9] The measurement method according to any one of Appendices F5 to F8, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0363] [Appendix F10] The measurement method according to any one of Appendices F5 to F9, wherein the second member is supported rotatably about an axis along the optical axis of the focusing optical system.

[0364] [Appendix F11] The measurement method according to any one of Appendices F1 to F10, wherein the second reflected light is reflected by the convex portion in the irradiation area and a portion in the irradiation area where the convex portion is not provided, and is then incident on the focusing optical system.

[0365] [Appendix F12] The measurement method according to any one of Appendices F1 to F11, wherein the detection detects the collected light by a light-receiving element having a detection surface that is arranged on a plane different from the conjugate plane.

[0366] [Appendix F13] A measurement computer program that causes a computer to execute the measurement method according to any one of Appendices F1 to F12.

[0367] [Appendix G1] A measurement method for measuring a surface to be measured having a riblet structure in which a plurality of convex portions connected in a first direction are arranged in a second direction intersecting the first direction, the measurement method comprising: changing the polarization state of light from a light source and irradiating light onto an irradiation area on the surface to be measured; changing the polarization state of first reflected light reflected at a portion of the irradiation area where no convex portions are arranged; transmitting a portion of the first reflected light according to the polarization state of the first reflected light; collecting the transmitted light using a collecting optical system; detecting the collected light; and measuring the riblet structure based on the detection results.

[0368] [Appendix G2] The measurement method according to Appendix G1, wherein the amount of the second reflected light reflected by the convex portion in the irradiation area and detected is not reduced.

[0369] [Appendix G3] The measurement method described in Appendix G1 or G2, wherein a first member arranged on the optical path of the first reflected light changes the polarization state of light from the light source to a first polarization state, and a second member arranged on the optical paths of both the first reflected light and the second reflected light reflected by the convex portion in the irradiation area and detected changes the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

[0370] [Appendix G4] The measurement method according to Appendix G3, wherein the first member is not disposed on the optical path of the second reflected light.

[0371] [Appendix G5] The measurement method described in Appendix G3 or G4, wherein the first polarization state is linear polarization, and in transmitting a portion of the first reflected light, the first member transmits a portion of the first reflected light according to the polarization state of the first reflected light emitted from the second member.

[0372] [Appendix G6] The measurement method according to Appendix G5, wherein the second polarization state is elliptically polarized light.

[0373] [Appendix G7] The measurement method according to any one of Appendices G3 to G6, wherein the first member is a polarizing beam splitter, and the second member is a quarter-wave plate.

[0374] [Appendix G8] The measurement method according to any one of Appendices G1 to G7, wherein the second reflected light is reflected by the convex portion in the irradiation area and a portion in the irradiation area where the convex portion is not provided, and is then incident on the focusing optical system.

[0375] [Appendix G9] The measurement method according to any one of Appendices G1 to G8, wherein the collected light is detected by a light-receiving element having a detection surface arranged on a plane different from the conjugate plane.

[0376] [Appendix G10] A measurement computer program that causes a computer to execute the measurement method according to any one of Appendices G1 to G9.

[0377] It should be understood that those skilled in the art can make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure.

[0378] 1, 6 Optical device LS Light source 2, 7 Light-collecting optical system 21, 71 Lens group 22, 72 Light-splitting member 73 1 / 4 wavelength plate 3, 8 Light-receiving element 3a, 8a Light-receiving surface 4, 9 Housing 4a, 9a Contact member 5, 10 Computer 531 Calculation unit 532 Detection unit 533 Measurement unit

Claims

1. An optical device for inspecting a surface to be inspected having a riblet structure in which a plurality of convex portions continuing in a first direction are arranged in a second direction intersecting the first direction, comprising: a focusing optical system that irradiates light from a light source onto an irradiation area on the surface to be inspected and collects the light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; and a light amount changing member that can change the ratio between the amount of first reflected light reflected by a portion of the irradiation area where the convex portions are not provided and heading toward the light receiving element, and the amount of second reflected light reflected by the convex portions in the irradiation area and heading toward the light receiving element.

2. The optical device according to claim 1, wherein the light amount changing member changes the polarization state of the light directed toward the illumination area.

3. The optical device according to claim 1 or 2, wherein the light amount changing member reduces the amount of the first reflected light.

4. The optical device according to claim 3, wherein the light amount changing member does not reduce the amount of the second reflected light.

5. An optical device as described in any one of claims 1 to 4, wherein the light amount changing member comprises: a first member arranged on the optical path of the first reflected light, changing the polarization state of the light from the light source to a first polarization state; and a second member arranged on the optical paths of both the first reflected light and the second reflected light, changing the light in the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

6. An optical device for inspecting a surface to be inspected having a riblet structure in which a plurality of convex portions continuing in a first direction are provided in a second direction intersecting the first direction, comprising: a focusing optical system that irradiates light from a light source onto an irradiation area on the surface to be inspected and collects the light reflected by the irradiation area; a light receiving element that detects the light collected by the focusing optical system; a first member that is arranged on an optical path of a first reflected light that is reflected by a portion of the irradiation area where the convex portions are not provided and proceeds toward the light receiving element, and changes the polarization state of the light from the light source to a first polarization state; and a second member that is arranged on the optical paths of both the first reflected light and the second reflected light that is reflected by the convex portions in the irradiation area and proceeds toward the light receiving element, and changes the light of the first polarization state emitted from the first member to a second polarization state different from the first polarization state.

7. The optical device according to claim 5 or 6, wherein the first member is not disposed on the optical path of the second reflected light.

8. An optical device described in any one of claims 5 to 7, wherein the first polarization state is linearly polarized, and the first member transmits a portion of the first reflected light according to the polarization state of the first reflected light emitted from the second member, and emits the portion toward the light receiving element.

9. The optical device of claim 8, wherein said second polarization state is elliptical.

10. An optical device according to any one of claims 5 to 9, wherein the first member is a polarizing beam splitter and the second member is a quarter wave plate.

11. An optical device according to any one of claims 5 to 10, wherein the second member is supported rotatably about an axis aligned with the optical axis of the focusing optical system.

12. The optical device according to any one of claims 5 to 11, wherein the focusing optical system comprises the first member and the second member.

13. An optical device according to any one of claims 1 to 12, wherein the second reflected light is reflected by both the convex portion in the irradiation area and a portion of the irradiation area where the convex portion is not provided, and is directed toward the light receiving element.

14. An optical device according to any one of claims 1 to 13, wherein the detection surface of the light receiving element is arranged on a plane other than a plane conjugate with the inspected surface with respect to the focusing optical system.

15. An optical device according to any one of claims 1 to 14, further comprising a calculation unit that inspects the riblet structure based on the detection results by the light receiving element.

16. An inspection method for inspecting a riblet structure based on data representing the results of detection by an optical device according to any one of claims 1 to 15.

17. An inspection method for inspecting a surface to be inspected having a riblet structure in which a plurality of convex portions connected in a first direction are provided in a second direction intersecting the first direction, comprising: irradiating light onto an irradiation area on the surface to be inspected; collecting light reflected from the irradiation area by the irradiation of the light using a focusing optical system; changing the ratio between the amount of first reflected light reflected by a portion of the irradiation area where the convex portions are not provided and the amount of second reflected light reflected by the convex portions in the irradiation area; detecting the light collected by the focusing optical system; and inspecting the riblet structure based on the detection result.

18. An optical device for inspecting a surface to be inspected having a riblet structure in which a plurality of convex portions connected in a first direction are provided in a second direction intersecting the first direction, comprising: a focusing optical system that irradiates an irradiation area on the surface to be inspected with light from a light source and collects the light reflected from the irradiation area; a light receiving element that detects the light collected by the focusing optical system; and a light quantity changing member that changes the polarization state of light from the light source that is linearly polarized in a predetermined direction and heads toward the irradiation area, changes the polarization state of a first reflected light that is reflected from a portion of the irradiation area where the convex portions are not provided and heads toward the light receiving element, and transmits a portion of the first reflected light depending on the polarization state of the first reflected light.

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