JPH0961291A - Apparatus for testing optical parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for testing optical parts, wherein abnormality in a refractive index (refractive force) of an optical part and the defect on a surface of the optical part can be displayed simultaneously, while the defect of the optical part can be emphasized, and also the type and degree of the defect can be indicated. SOLUTION: White light emitted from a lamp 1 is transmitted through an optical fiber bundle 3 and radiated to a diffusion board 5. A light shielding board 6 with a light shielding pattern printed is pasted to a surface of the diffusion board 5. Therefore, the light shielding pattern is illuminated from backward. A position of the light shielding pattern coincides with a focal position of a convex lens A as an optical part to be inspected. Therefore, the white light incident to the convex lens A while being emitted from an edge of the light shielding pattern is made into parallel light by the convex lens A and incident to an image pickup device 7. Since the position of an image pickup lens 8 in the image pickup device 7 is appropriately adjusted, the image with uniform density can be picked up in this state. However, density of the image appears to vary at portions where abnormality in a refractive index occurs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member inspection device for detecting an optical defect such as an abnormal refractive index of an optical member such as a lens.

[0002]

2. Description of the Related Art An optical member such as a lens is designed such that an incident light beam is refracted regularly and travels in parallel, or converges or diverges at one point or linearly. However, if the optical member is processed imperfectly and the refractive power changes irregularly, or if dust or scratches occur on the inside or on the surface of the optical member, the incident light beam will be disturbed. However, the desired performance cannot be obtained. In particular, in optical members such as lenses and prisms created by injecting resin into a mold and molding, sink marks (depression caused by the resin separating from the mold surface), jetting (inside the optical member) due to molding abnormalities. In this case, a portion where the resin density is partially changed) and a flow mark (a W-shaped wrinkle generated on the surface of the optical member due to the contraction of the resin) are likely to occur, so that such a defect can be efficiently detected. Is needed.

Therefore, conventionally, a strain gauge has been used to detect these optical defects. In this strain gauge, polarization gratings are provided so as to intersect with each other, and a sample (optical member) is placed therein. Then, in accordance with the change (abnormality) in the refractive index of the sample, the transmittance of the light ray inside the optical member is polarized. Therefore, when viewed from the outside, the density of the portion is changed and it can be seen that the refractive index is abnormal.

[0004]

However, in the inspection by the strain gauge, it is necessary to identify whether the product is a good product or a defective product by the light and shade shape visible inside the optical member. There is a risk that it will happen. Moreover, in the strain gauge, the shape of the defect is not reflected as it is in the shading shape inside the optical member. Therefore, even if it can be identified as a defective product, the type of defect, the degree of the defect, etc. cannot be grasped.

Further, since the strain gauge can identify only the abnormality in the refractive index (refractive power), it is impossible to inspect the surface of the optical member for dust, scratches, dirt and the like. Therefore, in order to detect such defects as well, it is necessary to remove the optical member from the strain gauge and carry the optical member over a separate illumination system such as the light source of the slide projector for inspection. That is,
It is not possible to carry out an inspection for abnormal refractive index (refractive power) and an inspection for defects on the surface of an optical member in a single inspection work.

In view of the above problems, the present invention can display defects in the optical member surface as well as defects in the refractive index (refractive power) of the optical member in a single inspection operation, and emphasize defects in the optical member. Accurate pass / fail judgment is possible by showing
Another object of the present invention is to provide an optical member inspection device capable of indicating the type and degree of defects.

[0007]

The invention described in each claim is
This is done to solve the above problems. The invention according to claim 1 is an optical member inspection device for detecting an optical defect of an optical member, wherein a diffusion plate illuminated by illumination light and a light diffused by the diffusion plate are partially transmitted. And a light blocking means fixed to the diffusion plate for partially blocking light, and a focal position of an optical system including an optical member is matched with a position of the light blocking means.

The optical member includes a convex lens and a concave lens, a prism, a concave mirror and a convex mirror, and a plane-parallel plate. Further, it includes an optical member made of glass and an optical member formed by resin molding. The optical defect of the optical member refers to a partial abnormality of the refractive index or the refractive power, a defect on the surface of the optical member, or the like.
Examples of abnormalities in the refractive index and the refractive power include sink marks, jetting, and flow marks in resin-molded optical members, and poor surface processing in optical members made of glass. The surface defects of the optical member include surface scratches, dirt, dust, and the like.

The diffusion plate may be a translucent member illuminated from behind or a reflective member illuminated from the front side. The light-shielding means may be a light-shielding pattern directly printed on the surface of the diffuser plate, or may be one in which an opaque member is partially cut out and attached to the diffuser plate,
A light-shielding pattern may be printed on the surface of a transparent member that is separate from the diffusion plate. The boundary line between the part that partially transmits the light and the part that blocks the light in the light shielding means is
It may be linear or curved. In addition, only one boundary line may be provided, or a plurality of stripe lines may be provided. Furthermore, the boundary line may be oriented in a plurality of directions, or may be formed in a grid pattern.

The "optical system including an optical member" refers to an optical member itself that is a convex lens or a concave mirror, or a positive lens group including an optical member that is a concave lens, a convex mirror, a plane-parallel plate, or a prism. Each member is arranged such that the focal position of the entire optical system coincides with the position of the light shielding means.

The light transmitted through the optical system may be picked up by an image pickup device and displayed on a display device, or the same image effect can be obtained even when observed by the naked eye. in this case,
By focusing the image pickup device or the naked eye on the surface of the optical member, it is possible to detect defects such as scratches, dirt, and dust on the surface of the optical member.

The invention according to claim 2 specifies that the optical system according to claim 1 comprises only the optical member which is a convex lens. The invention described in claim 3 specifies that the optical system in claim 1 is a positive lens system as a whole, comprising the optical member which is a concave lens and a correction lens which is a convex lens.

The invention according to claim 4 specifies that the light-shielding member according to claim 1 is a transparent member having a light-shielding portion printed thereon. The invention according to claim 5 specifies that the shape of the light shielding portion according to claim 1 is a lattice shape.

The invention according to claim 6 is further provided with an image pickup device having an image pickup lens for converging the light transmitted through the optical system according to claim 1. In this way, the detection result can be evaluated without individual differences as compared with the case of observing with the naked eye.

The invention according to claim 7 specifies that the image pickup device according to claim 6 is arranged at a position optically equivalent to the surface of the optical member with respect to the image pickup lens. According to an eighth aspect of the present invention, the diffuser plate and the light shielding unit according to the first aspect are provided so as to be movable back and forth in the optical axis direction with respect to the optical system. By doing so, optical members having various focal lengths can be inspected by the same optical member inspection device.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[0017]

First Embodiment <Optical Configuration of Optical Member Inspection Apparatus> FIGS. 1 and 2 are optical configuration diagrams showing a first embodiment of an optical member inspection apparatus according to the present invention. As shown in FIG. 1 and FIG. 2, the illumination unit 4 and the image pickup device 7 forming the optical member inspection device are
They are arranged facing each other on the same optical axis l.

The image pickup device 7 is composed of an image pickup lens 8 which is a positive lens system as a whole, and an image pickup element 9 which is a CCD area sensor for picking up an image formed by the light converged by the image pickup lens 8. . This image sensor 9
The video imaged by is displayed by the display device 10 including a monitor television.

On the other hand, the illumination unit 4 as a whole can move back and forth on the optical axis 1 toward the image pickup device 7. Inside the illumination unit 4, its center is the optical axis l.
The disk-shaped diffuser plate 5 matched with is fixed orthogonally to the optical axis l. On the surface of the diffusion plate 5 on the imaging device 7 side,
The light shielding plate 6 is attached integrally. On the shading plate 6, a shading pattern 6a having a lattice pattern as shown in FIG.
Is printed with black paint. The light diffused by the diffusing plate 5 is partially shielded by the portion where the black paint is printed, and partially transmitted by the other portions.

On the back side of the diffusion plate 5, the tip 3a of the optical fiber bundle 3 is fixed to the illumination unit 4. At the base end 3b of the optical fiber bundle 3, a light source device including a white lamp 1 and a condenser lens 2 is arranged. Then, the white light emitted from the white lamp 1 is condensed by the condenser lens 2 and enters the optical fiber bundle 3 from the base end 3b thereof. This white light is transmitted through the optical fiber bundle 3 and is transmitted from the tip 3a thereof to the diffusion plate 5
It is irradiated toward. That is, the light blocking pattern 6 of the light blocking plate 6
a is illuminated from behind. Note that the length of the optical fiber bundle 3 is set sufficiently longer than the movable distance of the illumination unit 4. Therefore, even if the illumination unit 4 moves, the optical fiber bundle 3 can follow and constantly illuminate the light shielding pattern 6a of the light shielding plate 6.

The optical member to be inspected is coaxial with the optical axis l,
It is arranged between the imaging device 7 and the illumination unit 4. Specifically, when the optical member to be inspected is the convex lens A as shown in FIG. 1, the convex lens A is arranged at a position where the focal position of the convex lens A matches the light shielding pattern 6a of the light shielding plate 6. . Further, when the optical member to be inspected is the concave lens B as shown in FIG. 2, the power (absolute value) of the concave lens B is between the concave lens B and the illumination unit 4.
A correction lens C, which is a convex lens having a power (absolute value) larger than that, is arranged. The lens group including the concave lens B and the correction lens C is a positive lens group as a whole, and the concave lens B and the correction lens C are arranged so that the combined focal position thereof matches the light shielding pattern 6a of the light shielding plate 6. . That is, the focal position of the optical system including the optical member to be inspected is matched with the position of the light shielding means.

Although not shown, when the optical member to be inspected is a flat plate, the focal point of the correction lens C alone is aligned with the boundary surface between the diffusion plate 5 and the light shielding plate 6, The correction lens C is arranged, and the inspection target optical member is arranged between the correction lens C and the imaging device 7.
Further, when the optical member to be inspected is a reflection prism such as a Porro prism or a roof prism, the correction lens C is arranged so that the focal point of its own coincides with the boundary surface between the diffusion plate 5 and the light shielding plate 6. Then, the prism is arranged behind the correction lens C, and the image pickup device 7 is arranged on the emission optical axis of the light beam emitted from the prism. further,
When the optical member to be inspected is a reflection mirror, the positional relationship between the illumination optical system 4 and the reflection mirror (and the correction lens C) is the same as described above, and the illumination optical system 4 and the reflection mirror are A beam splitter or a half mirror is arranged between the two, and the image pickup device 7 is arranged in front of the reflected light optical path separated by the beam splitter or the half mirror.

When the optical member to be inspected (and the correction lens C) is arranged as described above, the light emitted from the optical member to be inspected becomes parallel light as long as the optical member to be inspected is a good product. Therefore, when viewed from the image pickup device 7 side, the light shielding plate 6
It is equivalent to that the light-shielding pattern 6a of is located at infinity.

If the focal position of the optical member A to be inspected (the combined focal position of the lens group consisting of the optical member B to be inspected and the correction lens C) deviates from the position of the light shielding pattern 6a toward the image pickup device 7 side. An inverted image (real image) of the light shielding pattern 6a is formed in the space between the inspection target optical member A (the inspection target optical member B) and the imaging lens 8 of the imaging device 7. The inverted image (real image) of the light-shielding pattern 6 a is relayed by the image pickup lens 8 and the image pickup element 9 of the image pickup lens 8 is relayed.
An erect image (real image) of the light shielding pattern 6a is formed in the space on the side. On the contrary, when the focus position of the inspection target optical member A (the combined focus position of the lens group including the inspection target optical member B and the correction lens C) shifts to the optical fiber bundle 3 side from the position of the light shielding pattern 6a, the light shielding plate 6 An erect image (virtual image) of the light shielding pattern 6a is formed in the space on the optical fiber bundle 8 side. The erect image (virtual image) of the light-shielding pattern 6a is relayed by the imaging lens 8 and an inverted image (real image) of the light-shielding pattern 6a is formed in the space of the imaging lens 8 on the image sensor 9 side. That is, the focus position of the inspection target optical member A (composite focus position of the lens group including the inspection target optical member B and the correction lens C) is the image of the object (light-shielding pattern 6a) present at this position. 8 is a boundary point of whether an image is formed as an erect image or an inverted image in the space on the side of the image pickup device 9 of 8, and is a position in which an optically unstable state occurs.

The distance between the optical member to be inspected and the imaging lens 8 is such that the focal position of the optical member to be inspected A (the combined focal position of the lens group consisting of the optical member to be inspected B and the correction lens C) is the light-shielding pattern 6a. Even if the position is slightly shifted to the image pickup device 7 side from the position, the inverted image (real image) of the light shielding pattern 6a is formed between them (to be exact, between the focal positions of both). , Taken as long as possible. Further, the image pickup element 9 and the image formation position (average position) of the upright image and the upright image are formed so that these images can be captured to some extent clearly even if an upright image is formed or an inverted image is formed by the imaging lens 8. It is arranged at an intermediate point with the formation position (average position). This position is a position that is optically equivalent to the surfaces of the inspection target optical members A and B with respect to the imaging lens 8.

Therefore, the real image (inverted image) α of the outer edges of the inspection target optical members A and B is always formed on the image pickup element 9, and the real image α of the outer edges of the inspection target optical members A and B is always formed. A real image (inverted image) β of the light-shielding pattern 6a that is directly visible without passing through the optical member to be inspected is formed around the periphery of the image with a slight blur (see FIGS. 4A to 4E).

Then, inside the real image α of the outer edges of the inspection target optical members A and B, the focal position of the inspection target optical member A (the combined focal position of the lens group consisting of the inspection target optical member B and the correction lens C). ) Is displaced toward the image pickup device 7 side from the position of the light shielding pattern 6a, the real image (erecting image) γ of the light shielding pattern 6a is slightly blurred (FIG. 4).
(D), see FIG. 4 (e)). In the real image (erecting image) γ of the light-shielding pattern 6a, the blur amount increases as the shift amount of the focus position decreases (see FIG. 4D), and the blur amount decreases as the shift amount increases. (See FIG. 4E).

On the contrary, the focal position of the optical member A to be inspected (the combined focal position of the lens group consisting of the optical member B to be inspected and the correction lens C) is closer to the optical fiber bundle 3 than the position of the light shielding pattern 6a. If they are deviated, the real image (inverted image) γ of the light-shielding pattern 6a is formed inside the real image α of the outer edges of the inspection target optical members A and B with a slight blurring (FIG. 4B, See FIG. 4A). The real image (inverted image) γ of the light-shielding pattern 6a has a larger blur amount as the focal position shift amount decreases (see FIG. 4B), and the blur amount decreases as the shift amount increases and becomes clear. (Fig. 4 (a)
reference).

When the focal position of the optical member A to be inspected (the combined focal position of the lens group consisting of the optical member B to be inspected and the correction lens C) coincides with the position of the light shielding pattern 6a, the optical members A and B to be inspected. The amount of blurring inside the real image α at the outer edge of is maximal, and the light rays are emitted with uniform brightness throughout (see FIG. 4C).

On the display device 10, the inside of the outer edge α of the optical members A and B to be inspected is located at the focal position of the optical member A to be inspected (the composite focus of the lens group consisting of the optical member B to be inspected and the correction lens C). When the (position) coincides with the position of the light-shielding pattern 6a, the black portion (the portion where the white light is blocked) and the white portion (the portion where the white light is transmitted) of the light-shielding pattern 6a are completely mixed to form a uniform pattern. It is displayed as a solid gray plane (in the case of a spherical lens, see FIG. 4C). When an aspherical lens is inspected as the inspection target optical members A and B, the focus position changes not only at one point but also gently, so that an image with a very gentle change in luminance is obtained. Then, as the focus position deviates from the position of the light shielding pattern 6a, the white portion and the black portion are separated (the separating direction follows the direction of the shift of the focus position), and finally the light shielding pattern 6a is formed. <Inspection Procedure by Optical Member Inspection Device> When inspecting an optical member by the optical member inspection device according to the first embodiment, the inspection target optical member A,
B is fixed to a holder (not shown) and arranged coaxially with the optical axis l. When the inspection target optical member is other than the convex lens A, the correction lens C is inserted between the inspection target optical member B and the illumination unit 4.

Next, the white lamp 1 is turned on to turn on the light shield plate 6.
The light-shielding pattern 6a is illuminated. Then, the display device 10
An image picked up by the image sensor 9 is displayed on the top. The inspector moves the illumination unit 4 while watching the image displayed on the display device 10. FIG. 4 is a photograph showing an image on the display device 10 when a resin-molded lens having a rectangular outer edge and spherically convex end faces as a lens to be inspected is seen from the front. And FIG. 4 (a) or (b)
, Inside the outer edge α of the optical member to be inspected,
When the light-shielding pattern γ is visible in the same direction as the light-shielding pattern β seen outside the outer edge α of the inspection target optical member, it means that the illumination unit 4 is too close to the inspection target optical member. keep away.
Conversely, as shown in FIG. 4D or 4E, inside the outer edge α of the inspection target optical member, the outer edge α of the inspection target optical member is inside.
When the light-shielding pattern γ is seen in the direction opposite to the light-shielding pattern β that is visible on the outside, it means that the illumination unit 4 is too far from the inspection target optical member, and therefore the illumination unit 4 is brought close to the inspection target optical member. As a result of such forward / backward adjustment of the illumination unit 4, when the light-shielding pattern γ disappears in most of the outer edge α of the inspection target optical member as shown in FIG. 4C, the illumination unit 4 moves to the proper position. In some cases, the adjustment is stopped.

As described above, the position of the illumination unit 4 is substantially equal to the focus position of the inspection target optical member A (the combined focus position of the lens group including the inspection target optical member B and the correction lens C). Therefore, when there is no defect in the inspection target optical members A and B, the density becomes uniform in the entire area within the outer edge α of the inspection target optical member, as shown in FIG.

On the other hand, if there is a portion in the optical members A and B to be inspected where the refractive index is abnormal or a portion where the refractive power is abnormal due to the shape defect of the surface thereof, only the abnormal portion. , Which is equivalent to having a focal length different from the focal length of the normal part. Therefore, as shown in FIG. 6, the light shielding pattern γ can be seen only in the abnormal portion. The degree of the refractive index (refractive power) abnormality of the abnormal portion (the amount of deviation of the focal length) can be identified by the appearance of the light shielding pattern γ. That is, as described with reference to FIG. 4, the more clearly the light-shielding pattern γ can be seen, the larger the degree of the refractive index (refractive power) abnormality (the amount of deviation of the focal length) becomes.

For example, a sink mark occurs in a circular shape and
Since the area where the sink mark occurs is thinner than other normal areas, the focal length becomes long. Therefore, a light-shielding pattern γ is formed in a circular shape on the image, and the light-shielding pattern γ of this abnormal portion appears in the same direction as the light-shielding pattern β outside the outer edge α of the inspection target optical member. Therefore, when the image is visible as shown in FIG. 6, it can be determined that a sink mark has occurred. Jetting occurs in an irregular shape, and its refractive index also changes irregularly. Therefore, the irregularly shaped portion on the image locally and suddenly changes in luminance. Therefore, it is possible to determine that a portion in which abrupt luminance change locally has an irregular shape is a portion in which jetting has occurred.

As described above, in the optical member inspection apparatus according to the present embodiment, a slight change in the refractive index (refractive power) of the optical members A and B to be inspected appears as a difference between light and dark, and the change in the refractive index (refractive power). It will be highlighted. Further, since the shape of the defect is reflected in the shaded shape of the image, the type and degree of the defect can be grasped.

When dust or dirt is attached to the surfaces of the optical members A and B to be inspected or scratched, a real image α of the outer edge of the optical members A and B to be inspected on the surface of the image pickup device 9 is obtained. An image of these dusts, dirts, or scratches is formed by the imaging lens 8 inside. That is, when light is blocked by dust or dirt, a shadow that is darker than the surroundings is formed, and when light rays are diverged due to scratches, a bright spot is formed.

In the optical member inspection apparatus according to this embodiment,
The illumination unit 4 is movable in the optical axis direction. Therefore, it is possible to inspect a plurality of types of optical members having different focal lengths. A correction lens C composed of a convex lens
By mounting, the inspection target optical member can be inspected even with the concave lens B, and when the convex lens A as the inspection target optical member has a long focal length, the distance between the convex lens A and the illumination unit 4 can be increased. Can be shortened.

Further, as a result of experiments conducted by the inventor, if the edge of the light-shielding pattern (the boundary line between the black portion and the transparent portion) is in only one direction, the optical abnormal component in the direction orthogonal to the edge can be detected. Was difficult. In this embodiment,
As shown in FIG. 3, since the light-shielding pattern 6a is printed so that the edges exist in the directions orthogonal to each other, it becomes possible to detect the optical abnormality in all directions.

[0039]

Second Embodiment FIG. 7 shows a light shielding pattern 6a used in the second embodiment of the present invention. As shown in FIG. 7, the light shielding pattern 6a of the light shielding plate 6 in the second embodiment is formed as a plurality of annular stripes printed concentrically around the optical axis l. Therefore, the edge of the light shielding pattern 6a in the second embodiment is oriented in all directions over 360 degrees. Therefore, the optical anomalous components in all directions can be detected to the same degree. Therefore, the shape and degree of the abnormality can be identified more accurately. Other configurations and operations in the present embodiment are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0040]

Third Embodiment FIG. 8 shows a light-shielding pattern 6a used in the third embodiment of the present invention. As shown in FIG. 8, the light-shielding pattern 6a of the light-shielding plate 6 in the third embodiment is formed as linear stripes radially extending at equal intervals around the optical axis l. Therefore, it is possible to detect the optical anomalous components in all directions to the same degree, and it is possible to accurately grasp the type of anomaly.

[0041]

According to the optical member inspection apparatus of the present invention configured as described above, even though the illumination optical system has a simple structure, the optical member surface is accompanied by an abnormality in the refractive index (refractive power) of the optical member to be inspected. The defect of can be inspected in one inspection operation. Further, since the defect of the optical member is emphasized and displayed clearly distinguished from the non-defective product, accurate pass / fail judgment can be made. Further, since the position and shape of the defect are displayed as they are as an image, the type and degree of the defect can be grasped, and appropriate feedback to the manufacturing process becomes possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical member inspection device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram when the optical member inspection device of FIG. 1 is applied to a concave lens.

FIG. 3 is a front view of the light shielding pattern in FIG.

FIG. 4 is a diagram showing an image on a display device during movement adjustment of the illumination unit in FIG.

FIG. 5 is a diagram showing an image on a display device when a normal optical member is inspected.

FIG. 6 is a diagram showing an image on a display device when an optical member having a sink mark is inspected.

FIG. 7 is a front view of a light shielding pattern of an optical member inspection device according to a second embodiment of the present invention.

FIG. 8 is a front view of a light shielding pattern of an optical member inspection device according to a third embodiment of the present invention.

[Explanation of symbols]

 1 White Lamp 3 Optical Fiber Bundle 4 Illumination Unit 5 Diffuser 6 Light Shield 7 Imaging Device 8 Imaging Lens 9 Imaging Device A Convex Lens B Concave Lens C Correction Lens

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Atsushi Kida 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Optical Co., Ltd.

Claims (8)

[Claims] 1. An optical member inspecting apparatus for detecting an optical defect of an optical member, comprising: a diffusion plate illuminated by illumination light; and a part of the light diffused by the diffusion plate while partially transmitting the light. An optical member inspection device, comprising: a light shielding unit fixed to the diffusion plate that shields light; and a focal position of an optical system including the optical member is made to coincide with a position of the light shielding unit. 2. The optical member inspection apparatus according to claim 1, wherein the optical system includes only the optical member that is a convex lens. 3. The optical member inspection apparatus according to claim 1, wherein the optical system comprises the optical member which is a concave lens and the correction lens which is a convex lens, and is a positive lens system as a whole. 4. The optical member inspection device according to claim 1, wherein the light shielding member is a transparent member having a light shielding portion printed thereon. 5. The optical member inspecting apparatus according to claim 1, wherein the light shielding portion has a lattice shape. 6. The optical member inspection device according to claim 1, further comprising an image pickup device having an image pickup lens that converges light that has passed through the optical system. 7. The optical member inspection device according to claim 6, wherein the imaging device is arranged at a position optically equivalent to the surface of the optical member with respect to the imaging lens. 8. The optical member inspection apparatus according to claim 1, wherein the diffusion plate and the light shielding means are provided so as to be movable back and forth in the optical axis direction with respect to the optical system.