JP2014142564A - Ring illumination adapter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ring illumination adapter that is able to satisfactorily illuminate a close-distance subject.SOLUTION: A ring illumination adapter comprises: an incident face on which light emitted by a light source is incident; a ring-like exit face having an aperture part for allowing the light incident on the incident face to exit as ring-like illumination light; and a ring-like diffusion reflection face arranged opposite the exit face, having a slide surface and a fine projecting structure or fine recessed structure discretely arranged on the slide surface, and configured to guide the light incident on the incident face to the exit face. The exit face comprises: a ring illumination optical system having a slide face in the form of a toric surface in which the normal of the exit side face approaches the center of the aperture part as the exit face approaches the center of the aperture part; and a mount part configured to arrange the incident face of the ring illumination optical system in front of the light source, and enabling it to be attached to a photographing device such that the exit face is located in a place surrounding the optical path of the photographing optical system.

Description

  The present invention relates to a ring illumination adapter used in a photographing apparatus or the like.

  Conventionally, as a ring illumination adapter suitable for macro photography such as an imaging device, for example, an illumination device described in Patent Document 1 is known. The illumination device described in Patent Document 1 converts light from a light source into a ring-shaped light source.

JP 2005-258011 A

  However, the optical system disclosed in Patent Document 1 has a flat exit surface, and is not considered for short-distance shooting, for example, illumination of a subject surrounded by a ring-shaped optical system.

  In view of such a problem, the present invention is to provide a ring illumination adapter that can perform favorable illumination even for a subject at a short distance.

  In order to solve the above-described problems and achieve the object, the ring illumination adapter according to the present invention emits light incident on the incident surface on which light emitted from the light source is incident, and emits light incident on the incident surface as ring-shaped illumination light. A ring-shaped exit surface having a plurality of openings and a fine convex structure or a micro-concave structure that is arranged opposite to the exit surface and is discretely arranged on the smooth surface. Ring illumination having a ring-shaped diffuse reflecting surface that leads to the exit surface, and having a toric surface-like smooth surface in which the normal of the exit-side surface approaches the center of the aperture as the exit surface approaches the center of the aperture An optical system, and a mount portion that allows the incident surface of the ring illumination optical system to be disposed in front of the light source and that can be attached to the photographing apparatus so that the exit surface is located in a place surrounding the optical path of the photographing optical system. ing.

  ADVANTAGE OF THE INVENTION According to this invention, the ring illumination adapter which can perform favorable illumination with respect to the near object can be provided.

It is a front view of the ring illumination adapter which concerns on embodiment. It is sectional drawing cut | disconnected by the II-II 'line | wire of FIG. 1, Comprising: It is sectional drawing seen from the top of FIG. It is a perspective view which shows the ring illumination adapter which concerns on embodiment, the mount part of a camera, and a light source. It is a perspective view showing the state which mounted | wore the camera with the ring illumination adapter which concerns on embodiment. It is a perspective view of the ring illumination optical system of the ring illumination adapter according to the embodiment. It is a front view of the ring illumination optical system of the ring illumination adapter according to the embodiment. It is sectional drawing cut | disconnected by the VII-VII 'line | wire of FIG. 6, Comprising: It is sectional drawing of the ring illumination optical system of the ring illumination adapter which concerns on embodiment. It is a side view of the ring illumination optical system of the ring illumination adapter according to the embodiment. It is a rear view which shows the structure of the back surface of the ring illumination optical system of the ring illumination adapter which concerns on embodiment. It is a side view showing the fine convex structure of the back surface of the ring illumination optical system of the ring illumination adapter which concerns on embodiment. It is a top view showing arrangement | positioning of the fine convex structure of the back surface of the ring illumination optical system of the ring illumination adapter which concerns on embodiment. It is a top view showing the modification of arrangement | positioning of the fine convex structure of the back surface of a ring illumination optical system. It is a top view showing the modification of arrangement | positioning of the fine convex structure of the back surface of a ring illumination optical system.

Hereinafter, embodiments of a ring illumination adapter according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.
[First Embodiment]
FIG. 1 is a front view of the ring illumination adapter 2. FIG. 2 is a top view of the ring illumination adapter 2 in FIG. 1 taken along II-II ′ and viewed from above. FIG. 5 is a perspective view of the ring illumination optical system 5 of the ring illumination adapter 2. FIG. 6 is a front view of the ring illumination optical system 5 of the ring illumination adapter 2. FIG. 7 is a cross-sectional view taken along the line VII-VII ′ in FIG. 6, and is a cross-sectional view of the ring illumination optical system 5 of the ring illumination adapter 2. FIG. 8 is a side view of the ring illumination optical system 5 of the ring illumination adapter 2. FIG. 9 is a rear view showing the configuration of the back surface of the ring illumination optical system 5 of the ring illumination adapter 2.

The ring illumination adapter 2 of the present embodiment has a ring illumination optical system 5 (FIG. 1) and a mount portion 3a (FIG. 2).
The ring illumination optical system 5 has a ring shape having an incident surface 6 on which light emitted from the light source 4 (FIG. 3) is incident and an opening 7a for emitting the light incident on the incident surface 6 as ring-shaped illumination light. The incident surface 7 has a fine convex structure 9 (FIG. 9) or a fine concave structure that is arranged opposite to the emission surface 7 and is discretely arranged on the smooth surface 8, and is incident from the incident surface 6. And a ring-shaped diffuse reflection surface 10 that guides light to the exit surface 7. The closer the exit surface 7 is to the center 7c of the opening 7a, the closer the normal of the exit side surface is to the center 7c of the opening 7a. It has a toric surface-like smooth surface (FIGS. 6 and 7).
The mount unit 3a has the incident surface 6 of the ring illumination optical system 5 disposed in front of the light source 4, and the camera 1 so that the exit surface 7 is located at a place surrounding the optical path of the imaging optical system of the camera 1 (imaging device). It can be attached to.

The camera 1 and the ring illumination adapter 2 are configured to be connectable via a ring illumination adapter side mount portion 3a and a camera side mount portion 3b.
Here, the bayonet type mounting method is adopted. Of course, the present embodiment is not limited to this. For example, a screw-type mounting method may be used.
When the ring illumination adapter 2 is attached to the camera 1, it passes through the optical axis AX of the photographing optical system of the camera 1 and the center of gravity of the adapter opening 16 of the ring illumination adapter 2 and is a line perpendicular to the adapter opening 16. L2 is configured to match each other.
Thereby, the light beam that has passed through the adapter opening 16 is guided to the photographing optical system of the camera 1.

In the camera 1, an LED light source 4 is arranged next to the strobe light 21. The ring illumination adapter 2 is attached to the camera 1 so that the incident surface 6 of the ring illumination optical system 5 is positioned immediately before the light source 4 (FIGS. 3 and 4).
The ring illumination optical system 5 has a ring-shaped emission surface 7 having an opening 7a for emitting light incident on the incident surface 6 as ring-shaped illumination light.
The ring illumination optical system 5 includes a ring-shaped diffuse reflection surface 10 that is disposed to face the exit surface 7 and guides light incident from the entrance surface 6 to the exit surface 7. The diffuse reflection surface 10 includes a smooth surface 8 (diffuse reflection surface side smooth surface) and fine convex structures 9 discretely arranged on the smooth surface 8 (FIG. 9). The fine convex structure 9 has a spherical shape partially protruding from the smooth surface 8 of the diffuse reflection surface 10 (FIG. 10).
Here, instead of the fine convex structure 9 protruding outward from the smooth surface 8, a fine concave structure recessed inward may be used.

The exit surface 7 is a toric surface-like smooth surface in which the normal line of the exit side surface approaches the center 7c of the opening 7a as it approaches the center 7c of the opening 7a (FIG. 7).
Here, the ring illumination optical system 5 has an axis L5 that passes through the center 7c of the opening 7a and is perpendicular to the diffuse reflection surface 10. The ring illumination optical system 5 is provided in the ring illumination adapter 2 so that the axis L5 is on a line L2 that passes through the center of gravity of the adapter opening 16 of the ring illumination adapter 2 and is perpendicular to the adapter opening 16. ing.
By attaching the ring illumination adapter 2 to the camera 1 via the mount portions 3a and 3b, the incident surface 6 of the ring illumination optical system 5 is disposed in front of the light source 4, and the exit surface 7 is the photographing optical system of the camera 1. It is arranged at a place surrounding the optical path.

The incident angle of light is large on the smooth surface 8 in the diffuse reflection surface 10, and much light guided from the light source 4 to the smooth surface 8 repeats total reflection.
The light incident on the exit surface 7 which is a toric surface-like smooth surface immediately after being reflected by the smooth surface 8 in the diffuse reflection surface 10 has a large incident angle, so that a lot of light repeats total reflection.
The light incident on the fine convex structure 9 in the diffuse reflection surface 10 is diffusely reflected by the action of the concave inner surface reflection of the fine convex structure, and out of the diffusely reflected light, the light exits on the exit surface 7 which is a toric surface-like smooth surface. The light incident at a small incident angle is refracted and transmitted as illumination light by receiving a lens action on the toric surface.
Here, when a fine concave structure is used instead of the fine convex structure 9, light incident on the fine concave structure is diffusely reflected by the action of the convex inner surface reflection of the fine concave structure, and of the diffusely reflected light, toric Light incident at a small incident angle on the exit surface 7 which is a planar smooth surface is refracted and transmitted through the lens action on the toric surface and becomes illumination light.

The refraction at the toric surface-like smooth surface on the exit surface 7 refracts the diffusely reflected light from the fine convex structure 9 in a wider range.
In particular, the inner surface of the toric smooth surface refracts light so as to approach the center 7c of the opening 7a, so that an object near the ring illumination adapter 2 can be illuminated.
By attaching the ring illumination adapter 2 having such a configuration to the imaging device such as the camera 1 via the mount portions 3a and 3b, the ring-shaped illumination is used even in short-distance shooting where the light amount is insufficient due to the shadow of the imaging device. You can shoot with little unevenness in the amount of light.

The ring-shaped illumination means a state in which the illumination light is guided from around the photographing optical axis, and is not necessarily a continuous ring light.
Further, as in the above-described embodiment, the ring-shaped illumination includes a fine convex structure or a fine concave structure that behaves like a plurality of point light sources when viewed from the subject side.

  In the present embodiment, the smooth surface 8 in the diffuse reflection surface 10 is a smooth surface. The reflection on the smooth surface can ensure a sufficient light propagation function, and the ring illumination adapter 2 can be made thinner.

Moreover, the ratio of the area of the smooth surface 8 and the fine convex structure 9 (or fine concave structure) in the region having the diffusion function satisfies the following conditional expression (1).
0.1 <SS / (SF + SS) <0.5 (1)
here,
SF is the area of the smooth surface 8 in the region having the diffusion function,
SS is the area of the fine convex structure 9 or the fine concave structure in the region having the diffusion function,
It is.

By not falling below the lower limit of conditional expression (1), the area occupied by the fine convex structure and the fine concave structure is ensured, and the diffusion function is ensured.
The area occupied by the smooth surface is ensured so as not to exceed the upper limit of the conditional expression (1), the propagation function by light reflection on the smooth surface is ensured, and the unevenness of the light amount is reduced.

In addition, the ring illumination optical system 5 includes a first reflecting portion 11 (reflecting surface) that reflects light incident from the incident surface 6 and a second reflecting portion 12 that reflects the light reflected by the first reflecting portion 11 at an obtuse angle. (Reflective surface). A part of the light reflected by the first reflecting portion 11 is not reflected by the second reflecting portion 12 but is incident on the toric smooth surface of the exit surface 7. The other part of the light reflected by the first reflecting portion 11 is reflected by the reflecting surfaces 12a, 12b, 12c, and 12d of the second reflecting portion 12 and enters the toric surface-like smooth surface of the exit surface 7. .
With such a configuration, light loss from the light source 4 is reduced and light is guided to the ring-shaped exit surface 7 and the diffuse reflection surface 10.

The second reflecting portion 12 has two reflecting surfaces 12a and 12b that are arranged to face each other and reflect the reflected light from the first reflecting portion 11 at an obtuse angle, and the two reflecting surfaces 12a. , 12b are arranged so as to approach each other as the distance from the first reflecting portion 11 increases.
As a result, light loss from the light source 4 is reduced and light is guided to the ring-shaped exit surface 7 and the diffuse reflection surface 10.

In addition, the second reflecting portion 12 has two reflecting surfaces 12c and 12d that are arranged to face each other and reflect the reflected light from the first reflecting portion 11 at an obtuse angle, and the two reflecting surfaces 12c. , 12d are arranged so as to approach each other as the distance from the first reflecting portion 11 increases.
As a result, light loss from the light source 4 is reduced and light is guided to the ring-shaped exit surface 7 and the diffuse reflection surface 10.

The ring illumination adapter 2 of the present embodiment satisfies the following conditional expressions (2), (3), and (4).
1.1 <R _out / R _in <1.8 (2)
1 <(R _out −R _in ) / R _min <3 (3)
0.5 <D _max / R _min <2 (4)
here,
R _in is the radius of the opening of the ring-shaped exit surface 7,
_Rout is the radius of the outer periphery of the ring-shaped exit surface 7,
R _min is the radius of curvature at the top of the cross section where the radius of curvature is the smallest among the toric surfaces of the exit surface 7,
D _max is the maximum value of the distance from the smooth surface 8 to the smooth surface of the exit surface 7 in the normal direction of the smooth surface 8 of the diffuse reflection surface 10.

By making sure that the lower limit of conditional expression (2) is not exceeded, the area of the diffuse reflection surface 10 can be secured, and the number of fine convex structures 9 (or fine concave structures) can be sufficiently secured, so that the illumination light is uniform. And the unevenness of the illumination light of the photographed image is suppressed.
The upper limit of conditional expression (2) is not exceeded, the ring illumination adapter 2 itself is prevented from becoming thick, and the imaging device can be easily brought close to the object to be imaged.
The amount of refraction by the exit surface 7 which is a toric-shaped smooth surface is increased so as not to fall below the lower limits of the conditional expressions (3) and (4), and the amount of illumination light in the region close to the ring illumination adapter 2 is secured. .
The ring illumination adapter 2 itself is prevented from becoming thick so as not to exceed the upper limits of the conditional expressions (3) and (4).

Further, the number X of the fine convex structures 9 (or fine concave structures) formed on the diffuse reflection surface 10 satisfies the following conditional expression (5).
100 <X (5)

  By making sure that the lower limit of conditional expression (5) is not exceeded, the number of fine convex structures 9 that behave like a light source when viewed from the subject is secured, and the amount of illumination light is secured. Further, since the amount of illumination light can be secured even if the size of each fine convex structure 9 is reduced, the thickness of the fine convex structure 9 is reduced and made thinner.

Further, the number X of the fine convex structures 9 (or fine concave structures) satisfies the following conditional expression (5-1).
300 <X (5-1)

  Uniformity of illumination light is enhanced by sufficiently securing the number of fine convex structures 9 (or fine concave structures).

Further, the optical path from the incident surface 6 to the exit surface 7 is constituted by a solid medium, and light incident from the entrance surface 6 is guided to the exit surface 7 by internal reflection in the solid medium.
As a result, the number of components can be reduced and the manufacturing cost can be reduced.

  The ring illumination optical system 5 may be configured by, for example, press molding or injection molding of a plastic material.

The mount portion 3 a is configured by a light shielding member 13 that is a separate member from the ring illumination optical system 5. The light shielding member 13 is provided with a cylindrical outer light shielding wall 13a that is longer than the ring illumination optical system 5 in the direction along the axis L5 at a position surrounding the outer periphery of the ring illumination optical system 5 (FIG. 2). .
By providing the outer light shielding wall 13a, the amount of illumination light leaking to the outside is reduced, and damage to the ring illumination optical system 5 is reduced.

Further, the light shielding member 13 is provided with a cylindrical inner light shielding wall 13b shorter than the ring illumination optical system 5 in the direction along the axis L5 inside the inner periphery of the ring illumination optical system 5 (FIG. 2). ).
By providing the inner light shielding wall 13b, the illumination light emitted from the emission surface 7 and the leakage light from the tapered portion on the inner periphery of the ring illumination optical system 5 are prevented from directly entering the imaging optical system of the camera 1. It is possible to improve the image quality.

  Further, the light shielding member 13 is provided with a hole (not shown) for guiding the light beam from the light source 4 of the camera 1 to the incident surface 6 of the ring illumination optical system 5.

Further, the light shielding member 13 includes a light shielding lid 15 that shields unnecessary light transmitted through the first reflecting portion 11 and the second reflecting portion 12 (FIG. 1).
As a modified example, a configuration may be adopted in which light that has passed through the first reflecting portion 11 and the second reflecting portion 12 can illuminate a distant subject (for example, about 30 cm away) without using the light shielding lid 15.

FIG. 10 is a side view showing the fine convex structure 9 on the back surface of the ring illumination optical system 5 of the ring illumination adapter 2.
The fine structure of the diffuse reflection surface 10 is a fine convex structure 9 as shown in FIG. 10, and this fine convex structure 9 is spherical, and satisfies the following conditional expression (6).
0.3 <D _max2 / R _min2 <0.8 (6)
here,
R _min2 is the radius of curvature at the top of the fine convex structure 9,
D _max2 is the maximum value of the distance from the smooth surface 8 to the top of the fine convex structure 9 in the normal direction of the smooth surface 8 of the diffuse reflection surface 10.

By ensuring that the lower limit of conditional expression (6) is not exceeded, the diffusion function of the diffuse reflection surface 10 is sufficiently ensured.
Manufacturing is facilitated by avoiding exceeding the upper limit of conditional expression (6).

In this embodiment, the ring illumination optical system 5 is molded by pouring a transparent plastic into the mold. When the molded ring illumination optical system 5 is removed from the mold, it is easy to remove.
Further, the ring illumination optical system 5 has a positioning convex portion 14 on the outer peripheral surface for positioning with the light shielding member 13.

FIG. 11 is a plan view showing the arrangement (pattern) of the fine convex structures 9 on the back surface of the ring illumination optical system 5 of the ring illumination adapter 2 according to this embodiment. FIG. 12 is a plan view illustrating a modification of the arrangement of the fine convex structures on the back surface of the ring illumination optical system. FIG. 13 is a plan view illustrating a modification of the arrangement of the fine convex structures on the back surface of the ring illumination optical system. 11, 12, and 13 are drawings in which only a part of the back surface of the ring illumination optical system 5 is extracted, and the fine convex structure in each figure is formed in the same pattern even in a range not shown. Has been.
In the present embodiment, the tops of the fine convex structures 9 are in a hexagonal close-packed arrangement (FIG. 11). The ring illumination adapter of the present invention is not limited to this arrangement, and may have a fine convex structure with a rectangular array arranged for each distance D1, as shown in FIG. Moreover, as shown in FIG. 13, it is good also as a concentric arrangement lined up on two concentric circles C1 and C2.

  Numerical data and arrangement patterns of fine convex structures in specific numerical examples and modifications of the present embodiment are shown below.

[Example 1]
The ring illumination adapter of Example 1 has the following configuration in the first embodiment described above.
Radius R _in of opening of ring-shaped exit surface 7 = 15.0 mm
The outer radius R _{out of the} ring-shaped exit surface 7 = 22.0 mm
Of the toric surface of the exit surface 7, the radius of curvature R _min = 3.0 mm at the top of the cross section where the radius of curvature is the smallest.
Maximum value D _max = 3.0 mm of the distance from the smooth surface 8 to the smooth surface of the exit surface 7 in the normal direction of the smooth surface 8 of the ring-shaped diffuse reflection surface 10
Radius R _in2 of the opening of the ring-shaped diffuse reflection surface 10 = 16.0 mm
Radius of curvature R _min2 = 0.3 mm at the top of the fine convex structure 9 of the diffuse reflection surface 10
The maximum value D _max2 = 0.15 mm of the distance from the smooth surface 8 to the top of the fine convex structure 9 in the normal direction of the smooth surface 8 of the diffuse reflection surface 10
Distance between top surfaces of fine convex structure 9 = 1.0 mm
Arrangement: fine hexagon

The numerical values in each conditional expression are shown below.
SS / (SF + SS) ≈0.245
R _out / R _in ≒ 1.467
(R _out −R _in ) /Rmin≈2.333
D _max / R _min = 1.000
X ≒ 800
D _max2 / R _min2 = 0.5

[Modification]
Numerical examples of the modified examples are shown below.
R _min2 = Change in the range of 0.2 to 0.5 mm D _max2 = Change in the range of 0.1 to 0.3 mm The distance between the top surfaces of the fine convex structure = in the range of 0.2 to 2.0 mm Change Arrangement: Any of hexagonal close-packed, concentric circles, and rectangular array The present invention is not limited to the above-described embodiments and examples, and various modifications can be made.

  As described above, the ring illumination adapter according to the present invention is useful for macro photography of a subject at a short distance.

DESCRIPTION OF SYMBOLS 1 Camera 2 Ring illumination adapter 3a, 3b Mount part 4 Light source 5 Ring illumination optical system 6 Incident surface 7 Ejection surface 7a Opening part 7c Center 8 Smooth surface (smooth surface)
9 Fine convex structure 10 Diffuse reflection surface 11 First reflection portion 12 Second reflection portions 12a, 12b, 12c, 12d Reflection surface 13 of second reflection portion Light shielding member 13a Outer light shielding wall 13b Inner light shielding wall 14 Positioning convex portion 15 Shading cover 16 Adapter opening

Claims (13)

An incident surface on which light emitted from the light source is incident;
A ring-shaped emission surface having an opening for emitting light incident on the incident surface as ring-shaped illumination light; and
A ring-shaped diffuse reflection that is arranged facing the exit surface and has a smooth surface and a fine convex structure or a fine concave structure that is discretely arranged on the smooth surface and guides light incident from the entrance surface to the exit surface. surface,
Have
A ring illumination optical system having a toric surface-like smooth surface in which the normal of the exit-side surface approaches the center of the opening as the exit surface approaches the center of the opening;
A mount portion that allows the incident surface of the ring illumination optical system to be disposed in front of the light source, and that can be attached to the photographing apparatus so that the exit surface is located at a location that surrounds the optical path of the photographing optical system;
A ring illumination adapter characterized by comprising:   The ring illumination adapter according to claim 1, wherein the smooth surface in the diffuse reflection surface is a smooth surface. The ring illumination adapter according to claim 2, wherein the ratio of the area of the smooth surface and the fine convex structure or the fine concave structure in the region having a diffusion function satisfies the following conditional expression (1).
0.1 <SS / (SF + SS) <0.5 (1)
here,
SF is the area of the smooth surface in the region having a diffusion function,
SS is an area of the fine convex structure or the fine concave structure in a region having a diffusion function.   The ring illumination optical system includes a first reflection part that reflects light incident from the incident surface, and a second reflection part that reflects the light reflected by the first reflection part at an obtuse angle, and Some of the light reflected by the reflecting part is incident on the toric surface-like smooth surface without passing through the second reflecting part, and the other part of the light reflected by the first reflecting part is the second light. The ring illumination adapter according to any one of claims 1 to 3, wherein the ring illumination adapter is incident on the toric surface-like smooth surface through a reflective portion of the ring.   The second reflecting portion is disposed at least oppositely and has two reflecting surfaces that reflect the reflected light from the first reflecting portion at an obtuse angle, and the two reflecting surfaces are the first reflecting surface. It arrange | positions so that it may approach, so that it leaves | separates from the ring illumination adapter of Claim 4. The ring illumination adapter according to any one of claims 1 to 5, wherein the following conditional expressions (2), (3), and (4) are satisfied.
1.1 <R _out / R _in <1.8 (2)
1 <(R _out −R _in ) / R _min <3 (3)
0.5 <D _max / R _min <2 (4)
here,
R _in is the radius of the opening of the ring-shaped exit surface,
R _out is the radius of the outer periphery of the ring-shaped exit surface,
R _min is the radius of curvature at the top of the cross-section where the radius of curvature is the smallest among the toric surfaces of the exit surface,
D _max is the maximum value of the distance from the smooth surface to the smooth surface of the exit surface in the normal direction of the smooth surface of the diffuse reflection surface. The number X of the fine convex structures or the fine concave structures formed on the diffuse reflection surface satisfies the following conditional expression (5). Ring lighting adapter.
100 <X (5) The ring illumination adapter according to claim 7, wherein the following conditional expression (5-1) is satisfied.
300 <X (5-1)   The optical path from the entrance surface to the exit surface is formed of a solid medium, and light incident from the entrance surface is guided to the exit surface by internal reflection in the solid medium. The ring illumination adapter according to any one of 8.   The mount portion is constituted by a light shielding member that is a separate member from the ring illumination optical system, and the light shielding member is a cylindrical light shield having a longer length than the ring illumination optical system at a position surrounding the outer periphery of the ring illumination optical system. The ring illumination adapter according to claim 9, further comprising a wall.   The mount portion is constituted by a light shielding member that is a separate member from the ring illumination optical system, and the light shielding member is a cylindrical light shield having a shorter length than the ring illumination optical system inside the inner periphery of the ring illumination optical system. The ring illumination adapter according to claim 9 or 10, wherein a wall is provided.   The second reflecting portion is disposed to face each other and has two reflecting surfaces that obtusely reflect light reflected by the first reflecting surface, and the two reflecting surfaces are the first reflecting surface. The ring illumination adapter according to claim 4, wherein the ring illumination adapter has two sets arranged so as to approach each other. The fine structure of the diffuse reflection surface is the fine convex structure, and the fine convex structure is spherical.
The ring illumination adapter according to any one of claims 1 to 12, wherein the following conditional expression (6) is satisfied.
0.3 <D _max2 / R _min2 <0.8 (6)
here,
R _min2 is the radius of curvature at the top of the fine convex structure,
D _max2 is the maximum value of the distance from the smooth surface to the top of the fine convex structure in the normal direction of the smooth surface of the diffuse reflection surface.

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