Optical module and inspection device

Abstract

This optical module is disposed in a space surrounded by an inspection object, and is mounted on an inspection device for inspecting the inner peripheral surface of the inspection object by irradiating the inner peripheral surface with an annular beam. The optical module comprises: a collimated light output unit that outputs collimated light in an axial direction of the inspection object; a mirror that is disposed at a position where the collimated light output from the collimated light output unit is incident, that reflects the collimated light, and that converts the collimated light into an annular beam which spreads in a circumferential direction of the inner peripheral surface of the inspection object; and a mirror fixing member that fixes the position of the mirror relative to the collimated light output unit. The mirror fixing member is configured such that the light reflected by the mirror directly reaches the inner peripheral surface of the inspection object within at least a partial range of the circumferential direction.

Description

Optical module and inspection device

[0001] The present invention relates to an optical module and an inspection device.

[0002] An inspection device is known that inspects the inner surface of a tubular inspection object by irradiating the inner surface of the object with an annular laser beam while moving along the axial direction of the object and obtaining a light-section image from the resulting annular beam image (see Patent Document 1). This inspection device uses an annular beam that expands circumferentially in the radial direction from a point on the central axis of the object in the space inside the object. The annular beam is incident on the inner surface of the object, and an annular beam image is captured by a camera positioned on the central axis of the object. Analysis of this annular beam image provides information about the inner diameter, surface shape, and presence or absence of defects on the inner surface of the object.

[0003] Japanese Patent Application Laid-Open No. 2019-60722

[0004] A laser beam emitted from a laser light source is incident on the apex of a conical mirror with a conical reflective surface, and is reflected by the conical reflective surface to produce an annular beam. A cylindrical glass tube, for example, is used to fix the conical mirror to the laser light source. With this structure, the annular beam reflected by the conical mirror passes through the glass tube and strikes the inner surface of the object under inspection.

[0005] When an annular beam passes through a glass tube, phenomena such as misalignment of the incident point due to refraction, ghosting (reflection) due to reflection on the surface of the glass tube, and flare due to striae can occur. This can lead to a decrease in inspection accuracy. An object of the present invention is to provide an optical module and an inspection device that can suppress the decrease in inspection accuracy.

[0006] According to one aspect of the present invention, there is provided an optical module that is mounted on an inspection device that is arranged in a space surrounded by an object to be inspected and that inspects the inner circumferential surface by irradiating an annular beam onto the inner circumferential surface of the object to be inspected, the optical module comprising: a collimated light output unit that outputs collimated light in the axial direction of the object to be inspected; a mirror that is arranged at a position where the collimated light output from the collimated light output unit is incident and that reflects the collimated light into an annular beam that spreads in the circumferential direction of the inner circumferential surface; and a mirror fixing member that fixes the position of the mirror relative to the collimated light output unit, wherein the mirror fixing member is configured so that the light reflected by the mirror directly reaches the inner circumferential surface within at least a portion of the circumferential range.

[0007] According to another aspect of the present invention, there is provided an inspection device comprising: the optical module; an imaging device that receives reflected light from the annular beam emitted from the optical module and diffusely reflected on the inner circumferential surface, and generates image data; and an optical module fixing member that fixes the position of the optical module relative to the imaging device, wherein the optical module fixing member blocks reflected light from the reflection point on the inner circumferential surface to the imaging device in a certain range in the circumferential direction, and allows reflected light to reach the imaging device directly from the reflection point on the inner circumferential surface in another range.

[0008] According to yet another aspect of the present invention, there is provided an inspection device comprising: an optical module that is arranged in a space surrounded by an object to be inspected and that irradiates an annular beam that spreads circumferentially onto the inner circumferential surface of the object to be inspected; an imaging device that receives light that is diffusely reflected from the annular beam emitted from the optical module on the inner circumferential surface and generates image data; and an optical module fixing member that fixes the position of the optical module relative to the imaging device, wherein the optical module fixing member is arranged so as to intersect with the light path that the reflected light that is diffusely reflected on the inner circumferential surface takes before entering the imaging device, and is formed of a material that is transparent in the wavelength range of the annular beam emitted from the optical module, and has a shape that does not cause a problem with light refraction at the location where the reflected light that is diffusely reflected on the inner circumferential surface passes through the optical module fixing member.

[0009] Since the light reflected by the mirror reaches the inner peripheral surface of the inspection object directly within at least a portion of the circumferential range, it is possible to suppress a decrease in inspection accuracy due to the effects of refraction and reflection. Since the optical module fixing member has a shape that does not cause a problem of refraction of light at the portion where the reflected light that is diffusely reflected by the inner peripheral surface of the inspection object passes through the optical module fixing member, it is possible to suppress a decrease in inspection accuracy due to refraction.

[0010] FIG. 1 is a schematic cross-sectional view of an inspection device according to a first embodiment. FIG. 2 is a schematic perspective view (partially schematic) of an optical probe 30. FIG. 3A is a side view of an optical module 10, and FIG. 3B is a cross-sectional view taken along dashed dotted line 3B-3B in FIG. 3A. FIGS. 4A and 4B are schematic perspective views of an optical module fixing member 21. FIGS. 5A and 5B are side views of an optical module 10 according to a modified example of the first embodiment. FIG. 6 is a schematic cross-sectional view of an inspection device according to a second embodiment. FIG. 7 is a schematic cross-sectional view of an optical probe 30 of an inspection device according to a third embodiment.

[0011] 1 to 4B, an optical module and an inspection device according to a first embodiment will be described. Fig. 1 is a schematic cross-sectional view of the inspection device according to the first embodiment. The inspection device according to the first embodiment inspects the inner peripheral surface of an object to be inspected by irradiating the inner peripheral surface with an annular beam.

[0012] A support plate 51 is disposed inside the housing 50. The support plate 51 divides the space into two spaces, an upper space and an lower space. The lower space is referred to as the inspection chamber 50A, and the upper space is referred to as the waiting chamber 50B. In the first embodiment, the inspection chamber 50A and the waiting chamber 50B are positioned vertically, but this does not necessarily have to be the case. For example, they may be arranged side by side horizontally. Alternatively, the vertical relationship between the waiting chamber 50B and the inspection chamber 50A may be reversed. A workpiece placement section 52 is fixed on the support plate 51, and a tubular inspection object 60, for example, is held on the workpiece placement section 52. The inspection object 60 is fixed in a position such that its central axis is parallel to the vertical direction. An opening is provided directly below the internal space of the inspection object 60, penetrating the support plate 51 and the workpiece placement section 52 in the vertical direction. An optical probe 30 is supported above the inspection object 60 by a linear motion mechanism 24 so as to be movable up and down. During inspection, the optical probe 30 descends and enters the space inside the inspection object 60 along its central axis. When inspecting the vicinity of the lower end of the inspection object 60, the tip (lower end) of the optical probe 30 descends to the vicinity of the lower end of the inspection object 60. At this time, openings provided in the support plate 51 and the workpiece setting part 52 function as relief holes to avoid interference with the optical probe 30. Note that the support plate 51 and the workpiece setting part 52 are not limited to those provided with openings as long as they are capable of supporting the inspection object 60.

[0013] The optical probe 30 includes an optical module 10, an imaging device 20, and an optical module fixing member 21. The optical module 10 is supported directly below the imaging device 20 by the optical module fixing member 21, and its position relative to the imaging device 20 is fixed.

[0014] The housing 50 houses a laser light source 22 and a control unit 25. The laser light source 22 is, for example, a laser diode that outputs a laser beam with a wavelength in the range of 370 nm to 1100 nm. Laser light is introduced from the laser light source 22 to the optical module 10 via an optical fiber 23. The control unit 25 controls the laser light source 22 and the linear motion mechanism 24 in response to commands from a host controller 40. An image captured by the imaging device 20 is input to an analysis unit 41 of the host controller 40, and the analysis unit 41 analyzes the image. The inner diameter of the inspection object 60 can be measured based on the results of the image analysis.

[0015] The housing 50 can be moved on the floor by means of wheels 53 .

[0016] Next, the positional relationship between the optical module 10, the inspection target 60, and the imaging device 20, and the function of the optical probe 30 will be described with reference to FIG.

[0017] 2 is a schematic perspective view (partly a schematic view) of the optical probe 30. The optical probe 30 includes an optical module 10 and an imaging device 20. The optical module 10 includes a collimated light output section 11, a mirror 12, and a mirror fixing member 14.

[0018] The collimated light output unit 11 includes a collimating lens 11A. Laser light is guided from a laser light source 22 to the optical module 10 via an optical fiber 23. The laser light output from the output end of the optical fiber 23 is collimated by the collimating lens 11A.

[0019] The collimated light output unit 11 outputs collimated light in the axial direction of the inspection object 60. A mirror 12 is disposed at a position where the collimated light output from the collimated light output unit 11 is incident. The mirror 12 has a conical reflective surface. The rotation axis of this conical surface coincides with the optical axis of the collimated light (the optical axis of the collimating lens 11A). The mirror 12 reflects the collimated light to generate an annular beam 62 that spreads in the circumferential direction of the inner surface of the inspection object 60. A mirror fixing member 14 fixes the position of the mirror 12 relative to the collimated light output unit 11. The mirror fixing member 14 is configured so that the light reflected by the mirror 12 directly reaches the inner surface of the inspection object 60 within at least a portion of the circumferential range. The specific configuration of the mirror fixing member 14 will be described later with reference to FIGS. 3A and 3B.

[0020] When the apex angle of the mirror 12 is 90°, the annular beam 62 spreads in a disk shape (sheet shape). The inner peripheral surface of the inspection object 60 is a rough surface with irregularities having dimensions equal to or greater than the wavelength of the annular beam 62. When the annular beam 62 is incident on the inner peripheral surface of the inspection object 60, diffuse reflection occurs. The location where diffuse reflection occurs is referred to as the diffuse reflection location 63. The diffuse reflection location 63 is along the intersection between a plane perpendicular to the central axis of the inspection object 60 and the inner peripheral surface of the inspection object 60. If the inner peripheral surface is a cylindrical surface, the diffuse reflection location 63 will have a circumferential shape. A portion of the reflected light 64 diffusely reflected at the diffuse reflection location 63 enters the imaging device 20. The imaging device 20 receives the reflected light 64 and generates image data.

[0021] The optical module fixing member 21 fixes the position of the optical module 10 relative to the imaging device 20. The optical module fixing member 21 ( FIG. 1 ) includes multiple (e.g., four) support columns discretely arranged in the circumferential direction to surround the optical axis of the collimated light. The optical module fixing member 21 blocks reflected light 64 from a diffuse reflection area 63 ( FIG. 2 ) on the inner surface of the inspection object 60 to the imaging device 20 in a partial circumferential range. In other areas, the reflected light 64 reaches the imaging device 20 directly from the diffuse reflection area 63 on the inner surface of the inspection object 60. As used herein, "reaching directly" means that light travels in a straight line from its starting point to its end point without being reflected or refracted. Note that light passing through an area close to a blocking object is diffracted. However, by excluding images in the area affected by diffraction from image processing, image analysis can be performed while eliminating the effects of diffraction. Therefore, the term "reaching directly" also includes the case where light reaches its starting point from its end point while being affected by diffraction.

[0022] Next, the configuration of the optical module 10 will be described with reference to Figures 3A and 3B. Figure 3A is a side view of the optical module 10, and Figure 3B is a cross-sectional view taken along dashed line 3B-3B in Figure 3A. The collimating lens 11A of the collimated light output unit 11 is supported within the lens barrel 15. An optical fiber 23 is inserted from one end of the lens barrel 15, and its output end is fixed facing the collimated light output unit 11.

[0023] The mirror 12 is supported by a mirror support 13, which is fixed to the lens barrel 15 via a mirror fixing member 14. That is, the mirror fixing member 14 fixes the position of the mirror 12 with respect to the collimated light output unit 11. The mirror fixing member 14 intersects, over at least a portion of its circumferential range, with the path of an annular beam 62 ( FIG. 2 ) that is reflected by the mirror 12 and heads toward the inner circumferential surface of the inspection object 60 ( FIG. 2 ). The annular beam 62 that passes through the range that does not intersect with the mirror fixing member 14 reaches the inner circumferential surface of the inspection object 60 directly.

[0024] For example, the mirror fixing member 14 is composed of four support members arranged at equal intervals in the circumferential direction when viewed along the optical axis of the collimated light. Each of the four support members has a columnar shape extending parallel to the optical axis of the collimated light. The four support members intersect the path of the annular beam 62 reflected by the mirror 12 at a portion in the circumferential direction. The annular beam 62 propagating along a path that does not intersect with the four support members directly reaches the inner circumferential surface of the inspection object 60.

[0025] The circumferential dimension of each of the four support members is smaller than the radial dimension thereof, and the circumferential dimension of each of the four support members decreases as it approaches the mirror 12. By adopting such a shape, the area that blocks the annular beam 62 (FIG. 2) in the circumferential direction is reduced, and sufficient mechanical support force can be obtained.

[0026] Next, the structure of the optical module fixing member 21 will be described with reference to Figures 4A and 4B. Figures 4A and 4B are schematic perspective views of the optical module fixing member 21. As shown in Figure 4A, the imaging device 20 is supported by an imaging device support member 20A. The imaging device support member 20A has an opening facing the optical module 10. The optical module fixing member 21 is composed of four rod-shaped members arranged at equal intervals in the circumferential direction. Each of these rod-shaped members connects the edge of the opening of the imaging device support member 20A to the lens barrel 15 of the optical module 10.

[0027] The distance between the ends of the multiple rod-shaped members on the optical module 10 side is sufficiently narrower than the distance between the ends on the imaging device support member 20A side. Therefore, the optical module fixing member 21, which includes four rod-shaped members, and the imaging device support member 20A form a structure similar to a truss structure. Therefore, sufficient strength can be achieved even when the rod-shaped members are thin. A portion of the reflected light 64 (FIG. 2) incident on the imaging device 20 from the diffuse reflection area 63 (FIG. 2) is blocked by the rod-shaped members. By thinning the rod-shaped members, the range over which the reflected light 64 is blocked can be reduced. Furthermore, because the four rod-shaped members are not positioned near the aperture stop of the imaging device 20, the chief ray passing through the area not blocked by the rod-shaped members and the light rays passing nearby are not blocked by the rod-shaped members. This reduces the occurrence of misalignment (i.e., distortion) in the imaging position.

[0028] 4B , each of the four rod-shaped members constituting the optical module fixing member 21 may be bent or curved toward the central axis of the optical module 10. With such a shape, the optical module 10 can be inserted deep into the end of the inspection object 60 even if the inner diameter of the inspection object 60 is small.

[0029] Next, the advantageous effects of the first embodiment will be described. In a configuration in which the mirror 12 is fixed to the collimated light output unit 11 using a transparent member such as a glass tube, the annular beam 62 passes through the glass tube and reaches the inner surface of the inspection object 60. This can result in misalignment due to refraction, ghosting, and the like. In contrast, in the first embodiment, the annular beam 62 reflected by the mirror 12 reaches the inner surface of the inspection object 60 directly, so misalignment due to refraction, ghosting, and the like do not occur. This makes it possible to suppress a decrease in inspection accuracy.

[0030] Furthermore, in the first embodiment, in the range from the diffuse reflection point 63 ( FIG. 2 ) to the imaging device 20 where the optical module fixing member 21 is not disposed in the circumferential direction, the reflected light 64 reaches the imaging device 20 directly. Therefore, it is possible to suppress a decrease in inspection accuracy due to refraction or reflection of the reflected light 64.

[0031] In addition, in the circumferential direction, inspection result information cannot be obtained in the range where the annular beam 62 is blocked by the mirror fixing member 14. Similarly, inspection result information cannot be obtained in the range where the reflected light 64 (FIG. 2) is blocked by the optical module fixing member 21 (FIG. 1). In order to obtain inspection result information over as wide a range as possible, it is preferable to configure the range where the annular beam 62 is blocked by the mirror fixing member 14 and the range where the reflected light 64 is blocked by the optical module fixing member 21 so that they at least partially overlap, and it is more preferable to configure one range so that it is contained within the other range.

[0032] Next, an optical module according to a modification of the first embodiment will be described with reference to Figures 5A and 5B. Figures 5A and 5B are side views of the optical module 10 according to a modification of the first embodiment. In the first embodiment (Figures 3A and 3B), the mirror fixing member 14 is composed of multiple support members with a columnar shape extending parallel to the optical axis of the collimated light. In the modification shown in Figure 5A, the mirror fixing member 14 is composed of a single spiral member. The central axis of the spiral coincides with the optical axis of the collimated light. In the modification shown in Figure 5B, the mirror fixing member 14 has a double spiral structure.

[0033] The mirror fixing member 14 does not necessarily have to be configured as a member extending parallel to the optical axis of the collimated light. It may be spiral-shaped, as in the modified examples shown in Figures 5A and 5B. The number of turns of the spiral may be one or less, for example, about 0.5 turns.

[0034] Second Embodiment Next, an inspection device according to a second embodiment will be described with reference to FIG. 6. Hereinafter, a description of the components common to the inspection device according to the first embodiment (FIGS. 1 to 4B) will be omitted. FIG. 6 is a schematic cross-sectional view of the inspection device according to the second embodiment. In the first embodiment (FIG. 1), the optical probe 30 can be raised and lowered in a direction parallel to the optical axis of the collimated light, but in the second embodiment, the optical probe 30 can be raised and lowered and can also rotate around the optical axis of the collimated light.

[0035] The rotation mechanism 26 changes the position (posture) of the optical module 10 and the position (posture) of the imaging device 20 in a rotation direction around the optical axis of the collimated light output from the collimated light output unit 11 ( FIG. 2 ). Note that a configuration in which one of the position (posture) of the optical module 10 and the position (posture) of the imaging device 20 changes may also be used. The analysis unit 41 obtains inspection result information based on at least two sets of image data generated by the imaging device 20 when the optical module 10 is positioned at different positions in the rotation direction.

[0036] Next, the advantageous effects of the second embodiment will be described. In the first embodiment, it is not possible to obtain inspection result information for the range in which the annular beam 62 (FIG. 2) is blocked by the mirror fixing member 14 (FIGS. 3A and 3B). In contrast, in the second embodiment, by changing the position of the optical module 10 in the rotational direction, it is possible to obtain inspection result information after the position change for the range in which inspection result information was not obtained because the beam was blocked by the mirror fixing member 14 before the position change.

[0037] In addition, by changing the rotational position of the imaging device 20, it is possible to obtain inspection result information after the position change for areas that were blocked by the optical module fixing member 21 before the position change and therefore could not be obtained.

[0038] Furthermore, by changing the positions of both the optical module 10 and the imaging device 20 in the rotational direction, it becomes possible to obtain inspection result information over the entire circumferential area.

[0039] [Third Embodiment] Next, an inspection device according to a third embodiment will be described with reference to FIG. 7. Hereinafter, a description of components common to the inspection device according to the first embodiment (FIGS. 1 to 3B) will be omitted. FIG. 7 is a schematic cross-sectional view of an optical probe 30 of the inspection device according to the third embodiment. In the first embodiment (FIG. 1), the optical module fixing member 21 is composed of a plurality of support posts that are discretely arranged in the circumferential direction so as to surround the optical axis of the collimated light. In contrast, in the third embodiment, the optical module fixing member 21 is composed of a cylindrical member that surrounds the optical axis of the collimated light.

[0040] The imaging device 20 is supported by an imaging device support portion 27 , and the optical module fixing member 21 is fixed to the imaging device 20 via the imaging device support portion 27 .

[0041] The optical module fixing member 21 is disposed so as to intersect with the light path that a portion of the reflected light 64 diffusely reflected at the diffuse reflection portion 63 on the inner circumferential surface of the inspection object 60 takes before it enters the imaging device 20. The optical module fixing member 21 is formed of a material that is transparent in the wavelength range of the annular beam 62 emitted from the optical module 10. Furthermore, the portion 21A where the reflected light 64 passes through the optical module fixing member 21 has a shape that does not cause a problem with refraction of light.

[0042] Specifically, the optical module fixing member 21 is shaped so that the angle of incidence of the reflected light 64 at the incident surface and the exit surface is approximately 0° at the point 21A where the reflected light 64 passes through the optical module fixing member 21.

[0043] Next, the advantageous effects of the third embodiment will be described. In the third embodiment, the optical module fixing member 21 is made of a transparent material, so the reflected light 64 is not blocked over the entire circumferential range. Therefore, there is no loss of inspection result information due to the optical module fixing member 21.

[0044] Furthermore, the portion 21A where the reflected light 64 passes through the optical module fixing member 21 has a shape that does not cause light refraction to be a problem, thereby suppressing image misalignment and chromatic aberration due to refraction. This prevents a decrease in inspection accuracy. It can be said that light refraction is not a problem when the incident angle is approximately 0°±5°. Under the same glass member thickness, increasing the incident angle to 0° shortens the optical path length within the glass member. This also results in the excellent effect of reducing the influence of striae. Furthermore, increasing the incident angle to 0° reduces the reflectance on the surfaces of the glass member on the incident and exit sides. Reflected light may appear as ghost images in the image. Ghost images can be an obstacle during image analysis. In the third embodiment, the reduced reflectance reduces the excellent effect of reducing the occurrence of ghost images.

[0045] It is preferable that the portion 21A of the optical module fixing member 21 through which the reflected light 64 passes be shaped along a spherical surface centered on the center of the entrance pupil of the lens of the imaging device 20. With this shape, the angle of incidence of the reflected light 64 on the optical module fixing member 21 is approximately 0°. Note that if the angle between the traveling direction of the reflected light 64 and the optical axis of the lens of the imaging device 20 is small, the portion 21A of the optical module fixing member 21 through which the reflected light 64 passes may be shaped along a plane perpendicular to the optical axis of the lens of the imaging device 20. With this shape, the angle of incidence of the reflected light 64 can be made closer to 0° compared to when the optical module fixing member 21 is shaped simply cylindrical.

[0046] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible.

[0047] REFERENCE SIGNS LIST 10 Optical module 11 Collimated light output section 11A Collimated lens 12 Mirror 13 Mirror support section 14 Mirror fixing member 15 Lens barrel 20 Imaging device 20A Imaging device support member 21 Optical module fixing member 21A Reflected light transmitting section 22 Laser light source 23 Optical fiber 24 Linear motion mechanism 25 Control section 26 Rotation mechanism 27 Imaging device support section 30 Optical probe 40 Upper controller 41 Analysis section 50 Housing 51 Support plate 52 Workpiece placement section 53 Wheel 60 Inspection object 62 Annular beam 63 Diffuse reflection section 64 Reflected light

Claims

1. An optical module that is mounted on an inspection device that is placed in a space surrounded by an object to be inspected and that inspects the inner circumferential surface of the object to be inspected by irradiating the inner circumferential surface with an annular beam, comprising: a collimated light output unit that outputs collimated light in the axial direction of the object to be inspected; a mirror that is placed at a position where the collimated light output from the collimated light output unit is incident and that reflects the collimated light into an annular beam that spreads in the circumferential direction of the inner circumferential surface; and a mirror fixing member that fixes the position of the mirror relative to the collimated light output unit, wherein the mirror fixing member is configured so that the light reflected by the mirror directly reaches the inner circumferential surface within at least a portion of the circumferential range.

2. An optical module according to claim 1, wherein said mirror fixing member includes a support member that intersects with the path of said annular beam in a portion of said circumferential direction.

3. An inspection device comprising: an optical module according to claim 1 or 2; an imaging device that receives reflected light from the annular beam emitted from said optical module that is diffusely reflected on said inner circumferential surface and generates image data; and an optical module fixing member that fixes the position of said optical module relative to said imaging device, wherein said optical module fixing member blocks reflected light from the reflection point on said inner circumferential surface to said imaging device in a partial range in the circumferential direction, and allows reflected light from the reflection point on said inner circumferential surface to reach said imaging device directly in other ranges.

4. The inspection device according to claim 3, further comprising a rotation mechanism for changing the position of said optical module in a rotation direction around the optical axis of the collimated light output from said collimated light output section.

5. The inspection device according to claim 4, further comprising an analysis unit that obtains inspection result information based on at least two sets of image data generated by the imaging device when the optical module is positioned in different rotational directions.

6. An inspection device comprising: an optical module that is arranged in a space surrounded by an object to be inspected and that irradiates an annular beam that spreads circumferentially onto the inner circumferential surface of the object to be inspected; an imaging device that receives light that is diffusely reflected from the annular beam emitted from the optical module on the inner circumferential surface and generates image data; and an optical module fixing member that fixes the position of the optical module relative to the imaging device, wherein the optical module fixing member is arranged so as to intersect the light path that the reflected light that is diffusely reflected on the inner circumferential surface takes before entering the imaging device, and is made of a material that is transparent in the wavelength range of the annular beam emitted from the optical module, and has a shape that does not cause a problem with light refraction at the location where the reflected light that is diffusely reflected on the inner circumferential surface passes through the optical module fixing member.

Images