JP3417738B2 - 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 Optical members such as lenses and prisms are 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 refractive power changes irregularly due to abnormal molding of the optical member, or if dust or scratches are generated on the surface of the optical member due to human handling after formation, the incident light flux 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, in order to detect these optical defects, a sensory test by human eyes using a strain gauge, a light source for a slide projector, or the like has been performed. This strain gauge is one in which the polarization gratings are crossed,
This is an apparatus for observing a polarized light transmittance change according to a refractive index change (abnormality) of a sample (optical member) placed therein. In addition, the inspection using the light source for the slide projector means that the optical member is supported by the light emitted from the light source for the slide projector, the surface of the optical member is observed from the outside of the optical path, and the scratches raised by the light, It is to find dirt and dust.

[0004]

However, in these sensory tests by the human eyes, there is no objective criterion for judging good products and defective products. Therefore, when inspecting by multiple people, the quality judgment criteria will vary from person to person. It was lost, and good products were discarded as defective products, resulting in waste. In addition, even when the same person is inspecting, the judgment criteria tend to become stricter as the habit gets used,
In many cases, a good product was determined to be a defective product.

Therefore, in view of the above problems, it is an object of the present invention to provide an optical member inspecting apparatus capable of judging whether a good product is a good product or a defective product in accordance with an objective standard.

[0006]

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 the optical member inspection device is arranged at a focal position of a diffusion plate illuminated by illumination light and an optical system including the optical member. A light-shielding unit that is in contact with the diffuser plate so as to partially transmit the light diffused by the diffuser plate, an image capturing unit that captures the light transmitted through the optical system, and an image captured by the image capturing unit. A digitizing means for digitizing a portion showing an optical defect of the optical member, and a determining means for determining whether or not the numerical value digitized by the digitizing means exceeds a predetermined determination reference value. It is characterized by that.

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 diffusing 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. This shading means may be fixed when the boundary lines are oriented in a plurality of directions, but when there is only one boundary line or when all the boundary lines are oriented in the same direction, this boundary It is desirable to rotate around a rotation axis that is in contact with the line. When the light blocking means rotates, the diffusion plate may rotate integrally, or only the light blocking means may rotate with the diffusion plate fixed.

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 image pickup means may be a solid-state image pickup element or a pickup tube. The digitizing means may grasp the portion of the image showing the optical defect of the optical member by the magnitude of the luminance in the image or the portion having a large amount of change in light and shade (brightness). good. In the latter case, it is possible to extract a portion having a large amount of change in shading by performing a differential process on the image. Further, when the diffuser plate rotates, if all the images (or differentially processed images) obtained during one rotation of the diffuser plate are combined, regardless of the direction in which the optical defect occurs, It is possible to quantify all the parts showing optical defects. This numerical value may be the area of a portion showing an optical defect or the maximum width.

When there are plural kinds of numerical values numerically converted by the numerical converting means, the judging means may compare all of them with the judgment reference value, or a part of the kinds determined by the kind of the optical member. You may compare only the numerical value.

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, there is further provided an emphasizing means for emphasizing a portion of the image picked up by the image pickup means of the first aspect, which has a large change in shading, as a portion showing an optical defect of the optical member. is there. By doing so, the digitization by the digitizing means can be performed clearly.

According to a fifth aspect of the present invention, the light-shielding member of the fourth 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 has been specified that

According to a sixth aspect of the present invention, there is further provided rotating means for rotating the light shielding means according to the fifth aspect around a rotation axis that is in contact with the linear boundary line in the plane of the contact surface with the diffusion plate. It is a thing.

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. According to an eighth aspect of the present invention, the image pickup means of the fifth aspect performs the image pickup at each rotation position of the light shielding means rotated by the rotating means, and the image pickup means during one rotation of the light shielding member. It further comprises a synthesizing unit for synthesizing the images imaged by the image and enhanced by the enhancing unit. By doing so, as described above, since it is possible to quantify all the parts showing the optical defects irrespective of the direction in which the optical defects occur, it is possible to erroneously judge the non-defective product or the defective product. Absent.

According to a ninth aspect of the present invention, the emphasizing means according to the fourth or eighth aspect divides the image into a large number of pixels, compares the brightnesses of adjacent pixels, and differentiates the result. It is specified that the obtained image is the image on which the enhancement is performed.

The invention according to claim 10 is the invention according to claim 1, 4,
It is specified that the digitizing means of 8 or 9 measures the area of the portion showing the optical defect of the optical member to obtain the numerical value.

The invention according to claim 11 is the invention according to claim 1, 4,
It is specified that the digitizing means of 8 or 9 measures the maximum width of the portion showing the optical defect of the optical member to obtain the numerical value.

The invention as set forth in claim 12 is further provided with an extracting means for extracting only a portion corresponding to the optical member from the image picked up by the image pickup means of claim 1. With this configuration, it is possible to prevent the quality determination from being performed based on the image that is irrelevant to the performance of the optical member.

[0021]

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

[0022]

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 as the image pickup means comprises 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. It is configured. The image captured by the image sensor 9 is input to the display device 10 and the image processing unit 14.

The display device 10 is an image monitor device used at the time of initial adjustment of the optical member inspection device (that is, at the time of adjusting the position of the illumination unit 4 described later). Image processing unit 1
Reference numeral 4 denotes a processor that determines whether the inspection target optical member is a non-defective product or a defective product. Quantifying the degree of physical defects,
This numerical value is compared with a fixed judgment reference value (allowable value), and it is judged whether or not this numerical value is within or exceeds the judgment reference value. That is, the image processing unit 14 corresponds to an emphasizing unit, a synthesizing unit, a digitizing unit, and a determining unit. The image processing unit 14 also instructs the knife edge rotation control unit 15 to rotate the motor 13 in accordance with the determination process described above.

The knife edge rotation controller 15 rotates the motor 13 by 22.5 degrees in accordance with the rotation instruction from the image processor 14. On the other hand, the illumination unit 4 as a whole can move forward and backward on the optical axis 1 toward the imaging device 7. Inside the illumination unit 4, a disk-shaped diffuser plate 5 having its center coaxial with the optical axis 1 is rotatably held around the optical axis 1 in a plane orthogonal to the optical axis 1. A light-shielding plate 6 as a light-shielding unit is integrally attached to the surface of the diffusion plate 5 on the image pickup device 7 side. As shown in FIG. 3, which is a top view, the light shielding plate 6 is a semicircular plate made of an opaque member, and a radial straight line passing through the center of the diffusion plate 5 is a chord (knife edge) 6a, and It has an arc with the same radius as the diffuser plate 5. As a result of providing such a configuration, the light diffused by the diffusion plate 5 is partially shielded by the light shielding plate 6 and partially transmitted by the portion not covered by the light shielding plate 6.

An annular gear 11 coaxial with the diffusion plate 5 is fixed to the peripheral portion of the diffusion plate 5. This ring gear 11
Engages with the pinion gear 12, and the pinion gear 12 is fixed to the motor 1 fixed in the lighting unit 4.
It is attached to the rotating shaft of 3. Therefore, the motor 13
When the blade edge is rotated by the knife edge rotation control unit 15, the light shielding plate 6 and the diffusion plate 5 are rotationally driven through both gears 12 and 11, and as shown in FIG. 4, a surface orthogonal to the optical axis l. Inside (that is, within the contact surface between the diffusion plate 5 and the light shielding plate 6)
Is driven to rotate at. The rotation direction in this case is clockwise as viewed from the image pickup device 7 side, as shown in FIG. As a result of this rotation, the knife edge (string) 6a of the light shielding plate 6 also rotates around the optical axis 1. That is, these image processing unit 14 and knife edge rotation control unit 1
5, the motor 13 and the gears 11 and 12 constitute a rotating means.

On the rear surface 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 knife edge 6 of the light shielding plate 6
a is illuminated from behind. 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 follows and the knife edge 6a of the light shielding plate 6 can be illuminated at all times.

The optical member to be inspected is coaxial with the optical axis 1,
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 focus position 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 knife edge 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 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 inspection target optical member and the image pickup lens 8 is such that the focus position of the inspection target optical member A (the combined focus position of the lens group consisting of the inspection target optical member B and the correction lens C) is the knife edge 6a. Even if the position slightly shifts to the image pickup device 7 side from the position of, the inverted image (real image) of the knife edge 6a is formed between them (more accurately, between the focal positions of both). , Taken 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 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 edge of the optical member to be inspected is always formed on the image pickup element 9, and the inspection is performed around the real image α of the outer edge of the optical member to be inspected. A real image (inverted image) of the knife edge 6a that is directly visible without passing through the target optical member is slightly blurred (FIG. 5).
(See (a) to (e)).

Then, inside the real image α of the outer edge of the inspection target optical member, the focus position of the inspection target optical member A (the combined focus position of the lens group consisting of the inspection target optical member B and the correction lens C) is the knife. When the position of the edge 6a is displaced toward the imaging device 7 side, the real image (upright image) of the knife edge 6a is slightly blurred (see FIGS. 5D and 5E). . 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. If there is a deviation, the knife edge 6a is placed inside the real image α of the outer edge of the inspection target optical member.
The real image (inverted image) is slightly blurred (Fig. 5).
(B) and 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).

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 knife edge 6a, the outer edge of the optical member to be inspected is detected. The amount of blurring inside the real image α is maximized, and the light rays are uniformly illuminated over the entire image (see FIG. 5C).

In the image data input to the display device 10 and the image processing unit 14, the outer edge α of the optical member to be inspected.
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 knife edge 6a, the inner portion of the optical member A to be inspected, As long as B has no optical defects,
A black portion (a portion where white light is blocked) and a white portion (a portion where white light is transmitted) of the knife edge 6a are completely mixed and displayed as a gray plane of uniform density (in the case of a spherical lens). ). 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.

On the other hand, when 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, only the abnormal portion is present. , Which is equivalent to having a focal length different from the focal length of the normal part. Therefore, as shown in FIG. 6, the knife edge image γ appears 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) is reflected in the appearance of the image γ at the knife edge. That is, the more clearly the shade of the image of the knife edge appears, the greater the degree of the refractive index (refractive power) abnormality (the amount of deviation of the focal length).

If dust or dirt is attached to the surface of the optical member A to be inspected or is scratched, the dust or dirt on the inner portion of the outer edge α of the optical member to be inspected in the image data. , Or the image of scratches is the imaging lens 8
Formed by. 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. <Image Processing> Next, the content of the image processing executed in the image processing unit 14 to determine whether the optical member to be inspected is a good product or a defective product will be described with reference to the flowchart of FIG. 7. .

This image processing is started by pressing an inspection start button (not shown) connected to the image processing section 14. Then, the loop processing of S01 to S05 is executed.

In the first step S01 after entering this loop processing, the brightness of each pixel (pixel) forming the image data input from the image pickup device 9 is converted into numerical information of 256 gradations, which are respectively stored in the first memory 14a. Write.

In the next step S02, the numerical information written in the memory 14a is sequentially scanned to perform the differential processing. That is, the numerical value of each pixel is sequentially checked from the upper left pixel to the lower right pixel in the image. Then, the numerical value of the pixel to be checked is compared with the numerical value of the pixel to the left of it and the numerical value of the pixel adjacent to the upper side, and the absolute value of the difference between these numerical values is the differential value [0-255] of this pixel to be checked. And In the image data converted into the differential value obtained in this way, only the contour of the portion of the optical member to be inspected where there is an optical defect and the edge of the knife edge 6a become an image with high density (change in shade in the image). Corresponds to an emphasis means for emphasizing a large part as a part showing an optical defect of the optical member).

In the next S03, an image synthesizing process is executed. That is, each differential value obtained in S02 is written in the second memory 14b. At this time, as a result of S03 in the previous loop processing, the differential value of the previous image is the second memory 1
If it is written in 4b, the differential values already written in the second memory 14b are taken out, and the differential values obtained in S02 in the current loop processing are added, and then in the second memory 14b. Overwriting (corresponding to a synthesizing unit that synthesizes an image captured by the image capturing unit and emphasized by the enhancing unit while the light shielding unit makes one rotation).

At the next step S04, it is checked whether or not the knife edge 6a has rotated once after the processing is started. Then, if one revolution has not yet been made, in S05,
The knife edge 6a for the knife edge rotation controller 15
Command to rotate 22.5 degrees. If this rotated image data is input from the image sensor 9, the process proceeds to S
Returning to 01, the processing for this new image data is executed.

The reason why the knife edge 6a is rotated by a slight amount (S05) and the obtained image data is accumulated (S03) is as follows. 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 can be detected most, but the abnormal component in the direction orthogonal to the direction of the knife edge 6a is detected very well. Not done. Therefore, the knife edge 6a itself is rotated in a plane orthogonal to the optical axis 1 to detect all abnormal components in all directions and combine them on the same image. As a result, the following effects are also obtained. That is, knife edge 6a
As shown in FIG. 6, in the image when the image is stopped, in addition to the edge of the optical defect portion (the circular arc portion in the center of FIG. 6), the edge of the knife edge 6a (the black and white boundary line extending to the left and right in the center of FIG. 6). )
Is also displayed as a place where the shading changes rapidly. Since the edge of the knife edge 6a is not the edge itself of the optical defect portion which is originally required to be detected, it is desirable that the edge is not detected. Therefore, when the knife edge 6a is rotated, the position of the edge of the optical defect portion is immovable, whereas the edge of the knife edge 6a is rotated. Therefore, when the image synthesizing process is performed, the edge of the optical defect portion is more and more emphasized, while the edge of the knife edge 6a is planar in the closed region (the portion surrounded by the edge) of the optical defect portion. Since it is averaged to, it is no longer recognized as a boundary line.

As a result of repeating the loop processing as described above, when the knife edge makes one rotation (that is, the knife edge 6a).
Repeated 16 times each 22.5 degrees), S04
This loop processing is exited from, and the processing proceeds to S06.

FIG. 8 is a flow chart showing the contents of the inspection area extraction processing subroutine executed in S06. First S11 after entering this subroutine
Then, binarization processing is performed. This binarization processing is to replace the numerical value information with 255 (white) when the numerical value information corresponding to each pixel of the image data in the second memory exceeds a predetermined threshold value, and to 0 (black value) when the numerical value information does not exceed the predetermined threshold value. ). This threshold value is set to a value such that the outer edge α of the inspection target optical member can be left as a white (255) closed curve without interruption. Image data obtained as a result of this binarization processing is shown in FIG. In FIG. 9, δ is an image of a gate during resin molding of an optical member, ε is an image of a pattern on the gate, η is an abnormal refractive index portion such as jetting, and σ is attached to the surface of the optical member. It is an image of garbage. It should be noted that in FIG. 9, for convenience of drawing, white / black is reversed and drawn.

In the next step S12, a closed area extraction process is executed. The closed area extraction processing is processing for extracting only the area surrounded by the closed white line. Specifically, among the black pixels [0] forming the binarized image data in S11, the one surrounded by the white pixel [255] is regarded as the pixel in the closed region. And
The number of all pixels considered to be in this closed area is set to 255
And all the other pixels are set to 0. Image data obtained as a result of this closed region extraction processing is shown in FIG. As shown in FIG. 9B, as a result of this closed region extraction processing, the line δ having an open end is erased, but only white / black inversion occurs within the outer edge α of the optical member, which is a closed curve. Therefore, the closed curve η and the point σ inside remain.

In step S13, a filling process is executed. The filling process is a process for erasing the black pixel [0] left in the white pixel [255]. Specifically, the number of black pixels [0] included in the image data obtained in S12 and surrounded by white pixels [255] is set to 255. The image data obtained as a result of this filling processing is shown in FIG.
As shown in FIG. 9C, as a result of this hole filling process, the closed curve η and the point σ within the outer edge α of the optical member are erased, and only the large and small regions α and ε remain.

In the next step S14, a region selection process is executed. The region selection process is a process for validating only the originally required region and deleting the other closed regions extracted based on a part of the gate or the like.
Specifically, among the closed areas included in the image data obtained in S13, the closed area located in the center of the screen is left as it is, and the numerical values of all pixels forming the other closed areas are set to 0. The image data obtained as a result of this area selection processing is shown in FIG. As shown in FIG. 9D, the area of the white pixel [255] in this image corresponds to the area of the image of the optical member to be inspected. Therefore, this image is hereinafter referred to as “mask image”.

At the next step S15, the value of each pixel forming the mask image (8-bit parallel digital value) and the value of each pixel written in the second memory 14b (8-bit parallel digital value) are ANDed. Calculate As a result of this AND operation processing, of the image data written in the second memory 14b, only the portion corresponding to the area of the white pixel [255] of the mask image is left as it is, and the numerical values of the pixels of other portions are all 0. Becomes

As described above, the image data used for determining the non-defective product or the defective product can be obtained. Therefore, this subroutine is ended and the process is returned to the main routine of FIG. In S07 executed next to S06 in FIG. 7, the numerical value of each pixel constituting the image data extracted as a result of S06 is compared with a threshold value set to a level at which eye-catching noise is not extracted, and binarized ( 255: white or 0: black). That is, if the numerical value of each pixel forming the image data is larger than the threshold value (if it is bright), the numerical value is replaced with 255,
If the numerical value of each pixel forming the image data is smaller than the threshold value (if it is dark), the numerical value is replaced with 0. Then, the graphical features of the image after binarization (area of white part, maximum width,
Calculate center of gravity, fillet diameter, etc.). For example, white [25
5] The number of pixels is counted as an area amount (corresponding to a digitizing unit that digitizes a portion showing an optical defect of an optical member in an image captured by the image capturing unit).

In the next S08, a pass / fail judgment process is executed. That is, each graphical feature amount calculated in S07 is compared with each preset pass / fail judgment reference value.
Then, if there is at least one graphical feature amount that exceeds the corresponding acceptance / rejection determination reference value, it is determined as a failure (defective product), but all the graphical feature amounts are within the acceptance / rejection determination reference value corresponding to each. If it is within the range, it is determined as a pass (non-defective product) (corresponding to a determining unit that determines whether or not the numerical value digitized by the digitizing unit exceeds a predetermined determination reference value). Which of the graphic feature amounts used for the determination is used for the pass / fail determination depends on the type of the inspection target optical member. When this pass / fail judgment processing is completed, this image processing is ended.

As the image synthesizing process executed in S03 of the above-mentioned image processing, MAX calculation may be performed. In the above-mentioned addition processing, the numerical values (luminance) of the corresponding pixels between the combination target image data are added, whereas in the MAX calculation, the larger numerical value (luminance) of the corresponding pixels between the combination target image data is used. The other value is adopted as the calculation result. In such a MAX operation, the brightness of the combined image is not saturated even if the brightness of each image data to be combined is high. Therefore, there is an advantage that an accurate inspection can be performed even in such a case. <Inspection Procedure by Optical Member Inspection Device> When inspecting an optical member by the optical member inspection device according to the present embodiment,
The inspector fixes the inspection target optical members A and B to a holder (not shown) so as to be coaxial 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. 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. And
As shown in FIG. 5A or 5B, when the knife edge γ is visible inside the outer edge α of the inspection target optical member in the same direction as the knife edge β seen outside the outer edge α of the inspection target optical member, illumination is performed. Since the 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 such forward / backward adjustment of the lighting unit 4, FIG.
, The knife edge γ is the outer edge α of the optical member to be inspected.
When most of them disappear, it is because the lighting 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.

Next, the inspector presses an inspection start button (not shown) to start the image processing of FIG. Then, the knife edge rotation controller 15 rotationally drives the knife edge 6a by 22.5 degrees (S05), and an image formed by the light passing through the optical elements A and B to be inspected at each rotational position is captured. An image is taken by the device 7 (S01). The image processing unit 14 emphasizes the grayscale change portion of each captured image by differentiation processing (S02), and adds up over one rotation (S03, S04). As a result, regarding defect components (refractive index [refractive power] anomaly, surface defects) in any direction of the optical member to be inspected, regions having them are extracted, and they are put together into one image data. That is, this image data is an image in which a defective portion is highlighted in white regardless of the direction of the defect. Although the image data obtained in this manner includes data on a portion other than the portion that originally functions as an optical member, the data on the portion is not obtained by the inspection target region extraction processing in S06. To be deleted. Then, the area, maximum width, etc. of the abnormal portion are digitized and compared with a certain judgment reference value, and whether the product is a good product or a defective product is objectively judged according to the comparison result.

[0058]

According to the optical member inspection apparatus of the present invention configured as described above, it is possible to determine whether the non-defective product is defective or non-defective according to an objective standard. Therefore, it is possible to stabilize the quality of products used as non-defective products, and
It is possible to prevent waste such as discarding non-defective products due to erroneous determination.

[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 an optical member having a sink mark is inspected.

7 is a flowchart showing the contents of image processing executed in the image processing unit 14 of FIG.

8 is a flow chart showing the contents of an inspection target area extraction processing subroutine executed in S06 of FIG.

9 is an explanatory diagram of the inspection target area extraction processing of FIG.

[Explanation of symbols]

4 lighting units 5 diffuser 6 light shield 7 Imaging device 8 Imaging lens 9 Image sensor 13 motor 14 Image processing unit 15 Knife edge rotation controller 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 G11N 21/84-21/958

Claims (12)

(57) [Claims] 1. An optical member inspection device for detecting an optical defect of an optical member, comprising: a diffusion plate illuminated by illumination light; and a diffusion plate disposed at a focal position of an optical system including the optical member. A light-shielding unit that is in contact with the diffusion plate so as to partially transmit the light diffused by the plate, an image capturing unit that captures the light transmitted through the optical system, and the image capturing unit that captures the light captured by the image capturing unit. It is provided with a digitizing means for digitizing a portion showing an optical defect of the optical member, and a judging means for judging whether or not the numerical value digitized by the digitizing means exceeds a predetermined judgment reference value. Characteristic optical member inspection device. 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. A highlighting means for highlighting a portion of the image picked up by the image pickup means, which has a large change in shading, as a portion showing an optical defect of the optical member. Optical member inspection device. 5. The light-shielding member comprises a part that partially transmits the light and a part that partially shields the light, each part being separated by a linear boundary line. The optical member inspection device described. 6. The rotating device according to claim 5, further comprising rotating means for rotating the light shielding means about a rotation axis that is in contact with the linear boundary line in a surface of a contact surface with the diffusion plate. Optical member inspection device. 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 image pickup means performs the image pickup at each rotation position of the light shielding member rotated by the rotating means, and the image pickup means picks up the image while the light shielding means makes one rotation. The optical member inspection apparatus according to claim 5, further comprising a combining unit that combines the images emphasized by the unit. 9. The emphasizing means divides the image into a large number of pixels, compares the intensities of adjacent pixels with each other, and performs a differentiation process, and the image obtained as a result of the differentiation process is the enhanced image. The optical member inspection device according to claim 4, wherein: 10. The optical member inspection according to claim 1, 4, 8 or 9, wherein the digitizing means measures the area of a portion showing an optical defect of the optical member to obtain the numerical value. apparatus. 11. The optical member according to claim 1, 4, 8 or 9, wherein the digitizing means measures the maximum width of a portion of the optical member that exhibits an optical defect to obtain the numerical value. Inspection device. 12. The optical member inspection apparatus according to claim 1, further comprising an extracting unit that extracts only a portion corresponding to the optical member from the image captured by the image capturing unit.