JP3417737B2 - Optical member inspection device - Google Patents

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 so that an incident light beam is regularly refracted and travels in parallel, or converges or diverges into a single point or a line. 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 in addition to defects in the refractive index (refractive power) of the optical member in a single inspection operation, and the defects in all directions of the optical member can be displayed. It is an object of the present invention to provide an optical member inspection device that enables accurate pass / fail judgment by highlighting and also indicates the type and degree of a defect.

[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. A light blocking unit provided in contact with the diffusion plate that partially blocks light, and a rotation unit rotating the light blocking unit in a plane of a contact surface with the diffusion plate, and an optical system including the optical member. It is characterized in that the focal position is arranged so as to coincide with the position of the light shielding 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. It also includes an optical member made of glass and an optical member made of resin. The optical defect of the optical member refers to a partial abnormality in 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, defective surface processing in optical members made of glass, and the like. Further, as the surface defects of the optical member, surface scratches, dirt, dust, and the like are listed.

The diffusion plate may be a translucent member which is illuminated from behind or a reflecting member which is illuminated from the surface side. The light-shielding means may be a light-shielding pattern directly printed on the surface of the diffusion plate, or may be a plate-shaped opaque member that is appropriately cut and attached to the diffusion plate, or may be separate from the diffusion plate. The light-shielding pattern may be printed on the surface of the transparent member. The boundary line between the part that partially transmits the light and the part that blocks the light in the light blocking means may be linear or curved.
Further, the boundary line may be only one, or may be a plurality of stripes. Further, the boundary line may face in a plurality of directions.

The "optical system including an optical member" is an optical member itself which is a convex lens or a concave mirror, or a positive lens group including an optical member which is a concave lens, a convex mirror, a plane-parallel plate or a prism. The respective members are arranged so that the focal position of the optical system as a whole coincides with the position of the light shielding means.

The rotating means may rotate the light shielding means and the diffusing plate integrally, or when the light shielding means is formed as a plate-shaped member separate from the diffusing plate, only the light shielding means is rotated. May be. It is desirable that the center of rotation of the light shielding means by the rotating means is in contact with the boundary line between the portion that partially transmits light and the portion that shields light. Further, it is desirable that this rotation axis coincides with the optical axis of the optical system including the optical member. Further, the rotating means may be one that manually rotates the light shielding means, or one that is rotationally driven by a driving device such as a motor. When the light-shielding means is rotationally driven by the drive device, if it is rotated at a constant speed, the degree of abnormality can be quantitatively identified.

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.

According to a fourth aspect of the present invention, the light-shielding member according to the first aspect comprises a portion that partially transmits the light and a portion that partially shields the light, each of which is divided by a straight boundary line. It is specified that it will be.

According to a fifth aspect of the present invention, the light-shielding member according to the fourth aspect is an opaque member fixed to the diffusion plate so as to partially cover the diffusion plate.

According to a sixth aspect of the present invention, the rotating means in the fourth aspect rotates the light shielding member about a rotation axis in contact with the linear boundary line.

The invention according to claim 7 specifies that the optical axis of the optical system including the optical member according to claim 6 coincides with the rotation axis of the light shielding member. The invention according to claim 8 is further provided with an image pickup device having an image pickup lens for converging 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 9 specifies that the image pickup device according to claim 8 is arranged at a position optically equivalent to the surface of the optical member with respect to the image pickup lens.

According to a tenth aspect of the present invention, the diffuser plate and the light shielding means of 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.

[0020]

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

[0021]

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 forward and backward on the optical axis 1 toward the image pickup device 7. Inside the illumination unit 4, its center is the optical axis l.
A disk-shaped diffuser plate 5 coaxial with is held rotatably about the optical axis 1 in a plane orthogonal to the optical axis 1.
A light-shielding plate 6 is integrally attached to the surface of the diffusion plate 5 on the imaging device 7 side. As shown in FIG. 3 which is a plan view, the light shielding plate 6 is a semicircular plate made of an opaque member, and a straight line in the radial direction passing through the center of the diffusion plate 5 is a chord (knife edge) 6a. It has an arc with the same radius as the diffuser plate 5. As a result of having such a configuration, the diffusion plate 5
The light diffused by is partially shielded by the light shield plate 6 and partially transmitted by the portion not covered by the light shield plate 6.

An annular gear 11 coaxial with the diffusion plate 5 is fixed to the periphery of the diffusion plate 5. The annular gear 11 meshes with a pinion gear 12, and the pinion gear 12 is attached to a rotating shaft of a motor 13 fixed in the lighting unit 4. Therefore, when the motor 13 is rotationally driven by a drive circuit (not shown),
The light-shielding plate 6 and the diffusion plate 5 are rotationally driven via both gears 12 and 11, and as shown in FIG. 4, in a plane orthogonal to the optical axis 1 (that is, the contact between the diffusion plate 5 and the light-shielding plate 6). It is driven to rotate in the plane). As a result, the knife edge (string) 6a of the light shielding plate 6 also rotates around the optical axis l.
The rotation speeds of the light shielding plate 6 and the diffusion plate 5 are adjusted to 1 Hz (one rotation per second). That is, these motors 1
The rotating means is constituted by the gears 3, 12 and the gears 11, 12.

The tip 3a of the optical fiber bundle 3 is fixed to the illumination unit 4 on the back side of the diffusion plate 5. 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
It is condensed by the condenser lens 2 and enters the optical fiber bundle 3 from the base end 3b thereof. The white light is transmitted through the optical fiber bundle 3 and is emitted from the tip 3a thereof toward the diffuser plate 5. That is, the edge 6a of the light shielding plate 6 is illuminated from behind. The optical fiber bundle 3
Is set to be sufficiently longer than the movable distance of the lighting unit 4. Therefore, even if the lighting unit 4 moves,
The optical fiber bundle 3 follows and can constantly illuminate the knife edge 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. More 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 coincides with the knife edge 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 coincides with the edge 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 diffuser plate 5 and the light shield 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 members to be inspected (and the correction lens C) are arranged as described above, the lights emitted from the optical members to be inspected A and B are parallel as long as the optical members to be inspected A and B are good products. Become light. Therefore, when viewed from the image pickup device 7 side, it is equivalent to that the knife edge 6a of the light shielding plate 6 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 knife edge 6a toward the image pickup device 7 side. An inverted image (real image) of the knife edge 6a is formed in the space between the inspection target optical member A (inspection target optical member B) and the imaging lens 8 of the imaging device 7. The inverted image (real image) of the knife edge 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 knife edge 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 knife edge 6a, the light shielding plate 6 An erect image (virtual image) of the knife edge 6a is formed in the space on the optical fiber bundle 8 side. The erect image (virtual image) of the knife edge 6a is relayed by the imaging lens 8, and an inverted image (real image) of the knife edge 6a is formed in the space of the imaging lens 8 on the imaging element 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 (knife edge 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 members A and B to be inspected and the image pickup lens 8 is determined by 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). An inverted image (real image) of the knife edge 6a is formed between them (to be exact, between the focal positions of the two) even if it is slightly displaced from the position of the knife edge 6a toward the imaging device 7. So that it is as long as possible. Further, the image pickup device 9 forms an erect image at the formation position (average position) and the inverted image so that the erect image and the inverted image can be captured to some extent clearly regardless of whether the image pickup lens 8 forms the erect image or the inverted image. It is arranged at the midpoint between the formation position (average position). This position is a position that is optically equivalent to the surface of the inspection target optical member 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. Around the edge of, a real image (inverted image) of the knife edge 6a that is directly visible without passing through the inspection target optical members A and B is slightly blurred (see FIGS. 5A to 5E).

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 knife edge 6a, the real image (upright image) of the knife edge 6a is slightly blurred (FIG. 5).
(D), see FIG. 5 (e)). The real image (upright image) of the knife edge 6a becomes larger as the shift amount of the focus position becomes smaller (see FIG. 5D), and becomes smaller as the shift amount becomes larger and becomes clear. (See FIG. 5 (e)).

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 knife edge 6a. When they are deviated, the real image (inverted image) of the knife edge 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. 5 (b), FIG. 5 (a)). The real image (inverted image) of the knife edge 6a has a larger blur amount as the focal position shift amount decreases (see FIG. 5B), and becomes clear as the shift amount increases (see FIG. 5B). See FIG. 5 (a).

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) coincides with the position of the knife edge 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 light rays are emitted with uniform brightness throughout (see FIG. 5C).

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 combined 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 knife edge 6a, the black portion (the portion where white light is blocked) and the white portion (the portion where white light is transmitted) of the knife edge 6a are completely mixed to make a uniform mixture. 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 knife edge 6a, the white part and the black part are separated (the separating direction follows the direction of the shift of the focus position), and finally the shape of the knife edge 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 members A and B are fixed to a holder (not shown) and coaxial with the optical axis l. Deploy. When the inspection target optical member is other than the convex lens A, the inspection target optical member B
The correction lens C is inserted between the lighting unit 4 and the lighting unit 4.
As described above, in this embodiment, by mounting the correction lens C configured by a convex lens, it is possible to perform the inspection even when the optical member to be inspected is the concave lens B. If the focal length of the convex lens A as the inspection target optical member is long, the distance between the convex lens A and the illumination unit 4 can be shortened.

Next, the inspector turns on the white lamp 1 to illuminate the knife edge 6a of the light shielding plate 6. Then, the image captured by the image sensor 9 is displayed on the display device 10.

The inspector moves the illumination unit 4 while watching the image displayed on the display device 10. Figure 5
3 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 surfaces as viewed from the front is used as a lens to be inspected. Then, as shown in FIG. 5A or 5B, when the knife edge γ is seen in the same direction as the knife edge β seen outside the outer edge α of the inspection target optical member inside the outer edge α of the inspection target optical member, Since the illumination unit 4 is too close to the inspection target optical member, the illumination unit 4 is moved away from the inspection target optical member. On the contrary, as shown in FIG. 5D or 5E, inside the outer edge α of the inspection target optical member, the knife edge γ appears in the direction opposite to the knife edge β seen outside the outer edge α of the inspection target optical member. Since the illumination unit 4 is too far from the inspection target optical member when it is visible, the illumination unit 4 is brought close to the inspection target optical member. As a result of performing the forward / backward adjustment of the lighting unit 4 as described above, as shown in FIG.
When the knife edge γ disappears in most of the outer edge α of the optical member to be inspected, the illumination unit 4 is in the proper position, and the adjustment is stopped. As described above, in this embodiment, since the illumination unit 4 is movable in the optical axis direction, it is possible to inspect a plurality of types of optical members having different focal lengths.

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, as shown in FIG. 6, the density becomes uniform in the entire area within the outer edge α of the inspection target optical member.

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 in which the refractive power is abnormal due to the shape defect of the surface, 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. 7, the knife edge γ can be seen only in the abnormal portion. The degree of the refractive index (refractive power) abnormality of this abnormal portion (the amount of deviation of the focal length) can be identified by the appearance of the knife edge γ. That is, as described with reference to FIG. 5, the more clearly the knife edge γ can be seen, the greater the degree of the refractive index (refractive power) abnormality (the amount of deviation of the focal length).

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 knife edge γ is formed in a circular shape on the image, and the knife edge γ of this abnormal portion appears in the same direction as the knife edge β outside the outer edge α of the inspection target optical member. Therefore, when the image is visible as shown in FIG. 7, 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 device according to the present embodiment,
A slight change in the refractive index (refractive power) of the optical member to be inspected appears as a difference between bright and dark, and the change in the refractive index (refractive power) is emphasized. 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.

If dust or dirt is attached to the surfaces of the optical members A and B to be inspected, or if they are scratched, the inside of the real image α of the outer edge of the optical member to be inspected on the surface of the image pickup device 9 is detected. An image of these dust, dirt, or scratch is formed by the imaging lens 8. 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.

Next, the inspector operates a drive circuit (not shown) to rotate the motor 13. Then, the light shielding plate 6 together with the diffusion plate 5 starts to rotate at a rotation speed of 1 Hz, and the direction of the knife edge 6a gradually changes. When the knife edge 6a rotates, optical defects (locations where the image density changes abruptly) of the inspection target optical member are successively projected according to the direction of the knife edge 6a. That is, when the straight knife edge 6a is inserted into the optical path, the abnormal component in the direction parallel to the direction of the knife edge 6a is displayed with the greatest emphasis, but the abnormal component in the direction orthogonal to the direction of the knife edge 6a is displayed. The degree of emphasis will be the lowest. Therefore, in the present embodiment, the knife edge 6a itself is rotated in a plane orthogonal to the optical axis l so that anomalies in all directions can be emphasized to the same degree and displayed. In particular, when the aspherical lens is the optical member to be inspected, the area where the abnormality can be detected is limited, so the knife edge 6
By rotating a, the abnormality on the entire surface can be inspected.

Further, in the present embodiment, since the motor 13 rotates the knife edge 6a at a uniform speed (1 Hz), when the display device 10 is viewed, the abnormal parts are mutually (the directional components of the abnormal parts). It is also possible to know the relative difference in degree of anomalies. Further, even if the defect is a very subtle defect with little change in the refractive index (refractive power), the density pulsates with the rotation, so that it is easy to identify it.

[0044]

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. Further, by rotating the light shielding pattern, it is possible to detect an optical defect having an abnormal component in any direction.

[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 plate in FIG.

FIG. 4 is a perspective view showing a rotating state of the light shielding plate.

5 is a diagram showing an image on a display device at the time of adjusting movement of the illumination unit in FIG.

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

FIG. 7 is a diagram showing an image on a display device when an optical member having a sink mark is inspected.

[Explanation of symbols]

1 white lamp 3 Optical fiber bundle 4 lighting units 5 diffuser 6 light shield 7 Imaging device 8 Imaging lens 9 Image sensor A convex lens B concave lens C correction lens

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Kida 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Asahi Kogaku Kogyo Co., Ltd. (56) Reference JP-A-7-110302 (JP, A) JP Hei 8-304052 (JP, A) JP 5-346368 (JP, A) JP 6-109582 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 11 / 00-11/08 G01N 21/84-21/958

Claims (10)

(57) [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. The light-shielding means is provided in contact with the light-diffusing plate, and the rotating means rotates the light-shielding means in the plane of the contact surface with the light-diffusing plate. The focus position of the optical system including the optical member is adjusted. An optical member inspection device, which is arranged so as to coincide with the position of the light shielding means. 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 light-shielding member comprises a portion that partially transmits the light and a portion that partially shields the light, each of which is divided by a linear boundary line. The optical member inspection device described. 5. The optical member inspection device according to claim 4, wherein the light shielding member is an opaque member fixed to the diffusion plate so as to partially cover the diffusion plate. 6. The optical member inspection apparatus according to claim 4, wherein the rotating means rotates the light shielding member about a rotation axis that is in contact with the linear boundary line. 7. The optical member inspection apparatus according to claim 6, wherein an optical axis of an optical system including the optical member coincides with a rotation axis of the light shielding member. 8. The optical member inspection apparatus according to claim 1, further comprising an image pickup device having an image pickup lens that converges the light transmitted through the optical system. 9. The optical member inspection device according to claim 8, wherein the imaging device is arranged at a position optically equivalent to a surface of the optical member with respect to the imaging lens. 10. The optical member inspection apparatus according to claim 1, wherein the diffuser 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.