JPH0949805A - Method and device for inspecting optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the inspection efficiency of parts to be inspected by controlling the supplying order of the parts to be inspected. SOLUTION: An optical member inspection device is provided with CCD cameras 30a, 30b, 30c which are provided at every inspection item, a picture processor 40 which processes selected picture signals, a discriminating means 42 which discriminates whether or not the defect detected at every inspection item exceeds a prescribed reference value based on the information extracted by the processor 40, a parts supplying device 60 which continuously supplies lenses to be inspected to the picture inputting positions of the cameras 30a, 30b, and 30c, and a supplying order control means 43 which controls the supplying order of the parts supplying device 60 based on the frequency of occurrence of defects at every inspection item statistically obtained from the discriminated results of the discriminating means 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for continuously inspecting optical members such as lenses.

[0002]

2. Description of the Related Art In a production line for optical members such as lenses,
An inspection process is required to check the completed optical member for defects. Inspection is usually visual inspection of multiple items,
Alternatively, it is performed using an image processing method. The conventional inspection method sequentially executes inspections on a plurality of inspection items based on a predetermined order.

[0003]

However, in the above-described conventional inspection method, since the order of inspection items is fixed, for example, the probability of occurrence of a defect of a predetermined inspection item is higher than the probability of occurrence of other defects. In this case, there is a problem that the inspection efficiency is poor when the order of the inspection items is later.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is an efficient inspection method and an apparatus therefor when inspecting an optical element continuously for a plurality of inspection items. The purpose is to provide.

[0005]

In order to achieve the above object, an optical member inspection apparatus according to the present invention is an optical member inspection method for continuously inspecting a plurality of optical members for a plurality of inspection items. It is characterized in that, based on the appearance frequency of defects for each inspection item, which is statistically obtained in, the inspection of the item in which the defect is frequently detected is executed before the inspection of the other items.

Further, when a defect having a value larger than a reference value is detected in an item previously inspected, it is determined that the optical element to be inspected is defective and the subsequent inspection item is not executed. Is characterized by.

When an optical member is inspected for a plurality of different inspection items, and when a defect of a reference value or more is detected in any one of the inspection items, the optical member is determined to be defective. It is possible to reduce the number of unnecessary inspections by executing the inspections that are most likely to be detected.
The inspection throughput can be improved.

When a plastic lens is to be inspected, parts that are continuously molded in the same cavity are
Since defects with the same property tend to occur continuously, which property is more likely to cause a defect?
It can be predicted by statistically judging the test result.

For example, in the case of inspecting two kinds of properties of ten optical members as inspection items, if three out of ten optical members have a defect in the second property, the first and second inspection items. However, if the inspection is performed in the reverse order, the inspection of the first inspection item is not necessary for the optical member determined to be defective in the second inspection item. Therefore, a total of 17 inspections will be required.

On the other hand, in the optical member inspection apparatus according to the present invention, a plurality of image input means provided for each of a plurality of inspection items and an optical member to be inspected are continuously provided at each input position of the image input apparatus. A defect is determined for each inspection item based on the component supply means for supplying and an image input from the image input means, and when a defect exceeding a reference value is detected for at least one inspection item, the optical member is defective. Based on the appearance frequency of the defect for each inspection item that is statistically obtained in the inspection process, the component supply unit is controlled, and the component is input to the image input unit of the inspection item where the defect is frequently detected. It is characterized in that it is provided with a supply order control means for preferentially supplying.

Further, each of the image inputting means diffuses the light flux from the light source by the diffusing means having a central region having a low diffused transmittance and a peripheral region having a high diffused transmittance, and enters the optical member as an object to be inspected. Then, the object to be inspected is imaged by the imaging means provided at a position where the light flux transmitted through the object to be inspected reaches.

By making the diffuse transmittance of the diffusing means have the above distribution, light from the central region and light oblique to the optical axis from the peripheral region are incident on the test object. The image of the object to be inspected is formed mainly by the light from the central region of low brightness, and the obliquely incident light from the peripheral region does not participate in the image formation.

When a defect such as black dust that absorbs light is present on the object to be inspected, the amount of light reaching the photographing means decreases in the portion corresponding to this defect, so that it is better than the surrounding parts area in the photographed image. Appears as a low brightness area. On the other hand, if there is a defect such as a scratch that scatters light on the test object, the low-brightness light from the central region is scattered and attenuated at the portion corresponding to this defect, but the high-brightness light from the peripheral region is present. Are scattered and reach the photographing means, and as a result, the light amount of the defective portion on the image plane increases, and appears in the photographed image as a region having higher brightness than the surrounding component region.

Therefore, it is possible to detect defects having different properties such as absorptive defects and scattering defects as a region having a lower luminance and a region having a higher luminance than the base luminance of the component region at the same time by one photographing.

It is desirable that the central area of the diffusing means is set so that the range of the light beam vertically emitted from the central area substantially coincides with the test object. Accordingly, in the captured image, the image of the component area is formed by the light flux from the low-brightness central area, and the image of the background area is formed by the light flux from the high-brightness peripheral area. Can be clearly distinguished as different areas of. Therefore, the boundary can be easily discriminated when the component area is separated from the background area.

Further, it is desirable that both the central region and the peripheral region of the diffusing means are similar to the planar shape of the object to be inspected. As described above, in order to make the range of the light beam vertically emitted from the central region substantially coincide with the test object, it is necessary to make the central region similar to the test object. In addition, by making the peripheral region similar to the inspection object, the intensity distribution of the light obliquely incident on the inspection object from the peripheral region can be made uniform, regardless of the defect directionality. The detection accuracy can be made uniform.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical member inspection method and apparatus according to the present invention will be described below. First, FIG.
A schematic configuration of the optical member inspection device will be described below.

The optical member inspection apparatus comprises CCD cameras 30a, 30b and 30c as image input means provided for each of the first, second and third inspection items, and the lens to be inspected 1 photographed by these cameras. , 1, 1 for selecting one of the images, an image processing device 40 for processing the selected image signal, and detection for each inspection item based on the information extracted by the image processing device 40. The judgment means 42 for judging whether or not the defect is a predetermined reference value or more, and the monitor display 50 for displaying the judgment result.

Light sources 10a, 10b, 10c and diffusing means 20a, 20b, are provided at positions facing the CCD cameras with the lens 1 under test located at the image input position interposed therebetween.
A light source device composed of 20c is provided. The inspection item can be specified by setting the light source device or the CCD camera.

Further, the inspection device is statistically obtained from the component supply device 60 for continuously supplying the lens 1 to be inspected, which is the object to be inspected, to the image input position of each CCD camera, and the determination result of the determination means 50. A supply order control unit 43 that controls the supply order of the component supply device 60 based on the appearance frequency of defects for each inspection item.

The component supplying device 60 sends each component to each image input position in order, but if a defect having a reference value or more is detected in the item previously inspected, it is transferred to the image input position for the later inspection item. The optical member is excluded without sending. Also,
The optical element in which no defect is detected is sequentially sent to all image input positions.

The supply order control means 43 is initially set to supply the optical members in the order of, for example, the CCD cameras 30a, 30b, 30c, and while the plurality of optical members are continuously inspected, The occurrence frequency of defects for each inspection item is determined based on the determination result of the determination unit 50, and the supply order is changed so that the inspection item with the higher frequency is preferentially executed.

The supply sequence control means 43 is provided with a counter for counting the total number of inspected lenses, the number of non-defective products, and the number of defective products for each inspection item.
The supply order is determined by statistically determining the defect occurrence frequency based on the count values of these counters. For example, when a predetermined number of optical members are inspected, the defect rate of the first inspection item determined by the image taken by the CCD camera 30a is 0%, and the defect rate of the second inspection item by the CCD camera 30b is 5%. %, The defect rate of the third inspection item by the CCD camera 30c is 30%, the CCD camera 30
The supply order of the optical members is set so that the inspection can be performed in the order of c, 30b, and 30a.

When a plastic lens is to be inspected, a mold defect may be transferred to the lens, and in this case, the same defect is likely to occur successively. Also, with respect to other optical elements, there is a high probability that the types of defects that occur in members manufactured by the same lot, the same raw material, and the same apparatus are the same. Therefore, by first performing the inspection of the inspection items where defects are frequently detected,
The number of inspections for defective parts can be reduced, and the overall efficiency of inspection can be improved.

Next, the structure of an optical system for forming an image photographed by each CCD camera will be described with reference to FIG. Since the configurations of the optical systems are all common, the description will be given here with common reference numerals.

The optical system of the apparatus includes a light source 10 (10a, 10a).
b, 10c) and the diffusing means 20 (20a, 20b, 20c) composed of the first and second diffusing plates 21 and 22 for diffusing the luminous flux emitted from the light source 10, and passing through the diffusing means 20. A CCD camera 30 (30a, 30b, 30c) that captures and captures the light flux that has passed through the positive lens 1 that is the test object and the light flux that has passed through the periphery of the test lens 1 is provided.

The light source 10 and the lens 1 to be inspected are arranged on the optical axis of the CCD camera 30. CCD camera 30
Is composed of a taking lens 31 and a CCD sensor 32, and is adjusted so that the vicinity of the center in the thickness direction of the lens 1 to be inspected is a focus plane P. That is, the focus plane P and CC
The image receiving surface of the D sensor 32 is optically conjugate with the image pickup lens 31, and the image of the lens 1 under test on the focus plane P is
It is formed in the range indicated by the symbol O on the CCD sensor.

In order to secure the amount of light taken in by the CCD camera 30, the diffusing means 20 and the CCD camera 30 are used.
It is desirable to provide a condenser lens between and to collect the diffused light flux. In this example, the positive lens 1 arranged as the test object functions as a condenser lens.

The first and second diffusion plates 21 and 22 are substantially similar to the planar shape of the lens 1 to be inspected, and the area of the second diffusion plate 22 is smaller than that of the first diffusion plate 21. . These diffuser plates 21 and 22 are provided perpendicular to the optical axis so that the optical axis passes through the respective centers. Also,
These diffusers have the same or different diffuse transmittances. Therefore, considering the diffuser 20 as a whole, the central region where the first and second diffusers overlap has a low diffuse transmittance, and The diffused transmittance is relatively high in the peripheral region that does not become.

The size of the second diffusing plate 22 is determined so that the range of the light vertically emitted from the second diffusing plate 22 is substantially the same as that of the lens 1 to be inspected. As a result, all the vertical emission components from the central region enter the lens 1 under test, and
The component that vertically passes through the diffusion plate 21 and does not pass through the second diffusion plate 22, that is, the vertical emission component from the peripheral region does not enter the lens 1 to be inspected. Further, the planar shape of the first diffusion plate 21 is formed to be similar to the shape of the object to be inspected so that the oblique emission component from the peripheral region is uniformly incident on the object from all directions.

FIG. 3 shows an example of the planar shapes of the lens to be inspected and the diffusion plates 21 and 22. As shown in FIG. 3 (A-1), when the lens under test is the finder lens 1a having a rectangular planar shape, the planar shapes of the first and second diffusion plates 21 and 22 are as shown in FIG. It is desirable to make the rectangle as shown in A-2). Further, as shown in FIG. 3 (B-1), when the test lens is a general circular lens 1b, each diffusion plate 2
It is desirable that the planar shapes of 1 and 22 be circular as shown in FIG. 2 (B-2).

Since the inspecting apparatus of the embodiment is constructed so as to inspect a plastic lens molded by a multi-cavity mold without cutting it off from the runner, the lens to be inspected has a gate as shown in FIG. The runner R is connected via G.

In the photographed image, as shown in FIG. 4, a high-brightness background area B mainly formed by high-brightness components in the peripheral area reaching without passing through the second diffusion plate 22, The image (component region) S of the lens to be inspected which is mainly formed by the low-luminance component of the central region that has passed through the two diffusion plates is included.

By making the shape of the second diffusing plate 22 similar to the planar shape of the lens 1 to be inspected, the component region where the lens to be inspected is arranged and the background region are clear in the image as described above. It is possible to divide into target areas, and the separation processing of the target area in the image processing described later becomes extremely easy.

Here, if there is a defect that absorbs light on the surface or inside of the lens 1 to be inspected, for example, black dust contained in the optical member, part of the transmitted light from the central region forming the lens image is absorbed. As a result, the light does not reach the CCD sensor 32, so that a defect image DL having a lower brightness than that of the component region is generated in the component region S of intermediate luminance as shown in FIG.

If there is a defect that scatters light on the surface of the lens 1 to be inspected, for example, if white dust or scratches are present on the surface of the optical member, the light scatters due to this defect, and if there is no defect, C
A part of the high-intensity oblique emission component from the peripheral region that does not reach the range O of the lens image on the CD sensor 32 is part of the range O of the lens image.
As shown in FIG. 6, a defect image DH having a brightness higher than that of the component region is generated in the component region S having an intermediate luminance.

For example, when a low-luminance image DL due to an absorptive defect and a high-luminance image DH due to a scattering defect are present on a scanning line in the X-axis direction, the output of the pixel row along this scanning line is present. Is as shown in FIG. 7 (A). The image processing device 40 binarizes using two threshold values SH1 and SH2, so that two different characteristics are obtained as shown in FIGS.
Each type of defect can be extracted independently.

The balance of the extraction force with respect to the absorptive defect and the scattering defect can be adjusted by changing the position of the light source unit in the optical axis direction. The extraction power for defects is higher as the difference between the luminance of the defect area and the base luminance is larger, and is smaller as the difference is smaller.

In the structure of the optical system described above, the larger the incident angle of the light beam incident on the object to be inspected from the peripheral area, the larger the intensity of the scattered light due to the defect. Therefore, if the incident angle is increased, the scattering property is increased. The extraction power for defects of 1 is high, and the smaller it is, the lower is the extraction power for scattering defects. In addition, since the intensity of scattered light due to defects becomes relatively larger as the proportion of the high-intensity component incident from the peripheral region in the total amount of light incident on the test object becomes relatively large, increasing this proportion makes the scattering property higher. The extraction power for defects becomes high, and if it is made small, the extraction power for scattering defects becomes low.

The CCD cameras 30a and 30b shown in FIG.
The light source unit 10 corresponding to is set at a position relatively close to the lens 1 to be inspected. Since the total amount of light incident on the lens 1 to be inspected is relatively large, the base luminance is high. At the same time, since the incident angle of the light beam entering the lens 1 to be inspected from the peripheral region becomes large, the high-luminance region D due to the scattering defect
Both the brightness of H and the brightness of the low brightness region DL due to the absorptive defect become high. In this case, the extraction power for the scattering defects becomes high and the detection capability for the absorbing defects becomes relatively low.

Further, the CCD cameras 30a and 30b are set so that the diaphragms are opened so that the depth of focus is shallow. One CCD camera 30a is focused on the upper surface of the lens 1 to be inspected, and the other one. CCD camera 30b
Are set so that the lower surface of the lens 1 to be inspected is in focus. And the image of the CCD camera 30a is
The CCD camera 3 is used to detect a scattering defect (first inspection item) such as a scratch on the upper surface of the lens to be inspected.
The image of 0b is used to detect a scattering defect (first inspection item) such as a scratch on the lower surface of the lens to be inspected.

Further, the light source section corresponding to the CCD camera 30c is set at a position relatively far from the lens 1 to be inspected. Since the total amount of light incident on the lens 1 under test decreases,
The base brightness becomes low. At the same time, the angle of incidence of the light flux from the peripheral region on the lens under test becomes smaller,
Both the brightness DH in the high brightness region due to the scattering defect and the brightness DL in the low brightness region due to the absorbing defect become low. In this case, the ability to detect absorptive defects is high, and the ability to detect scattering defects is relatively low.

The CCD camera 30c is set so that the depth of focus is increased by narrowing the diaphragm. Thereby, the image of the CCD camera 30c is used to detect an absorptive defect (third inspection item) such as dust mixed in the inside of the lens to be inspected.

Next, the procedure of the inspection using the above apparatus will be described with reference to the flow charts shown in FIGS.

In step A-1, a predetermined number of times n is set in the counter C which determines the inspection order setting interval. As a result, the inspection order is reset every n inspections in the order setting subroutine shown in step A-28.

In steps A-2 to A-10, the lens to be inspected placed at the relevant position is inspected for the inspection items in the third rank, and in steps A-11 to A-18, the inspection items in the second rank and steps In A-19 to A-26, the lens to be inspected is inspected for the first inspection item. If there is no defect of the reference value or more for each inspection item, each lens to be inspected is moved to the inspection item position of the next order, otherwise, it is ejected as a defective product.

In step A-27, if the lenses to be inspected are not arranged at all the inspection positions and there is no lens to be inspected next, it is judged that the inspection is completed and the processing is terminated. If the lens to be inspected exists at any stage, the subroutine for setting the order shown in FIG. 9 is executed (step A-28), and the uninspected lens is supplied to the inspection position of the first order (step A- 29) and repeat the process from step A-2.

The flow chart of FIG. 8 shows that, from the inspection apparatus side, a maximum of three lenses are inspected for different inspection items during steps A-2 to A-26, in order to form a flow of parts. The inspection, transfer, and discharge are performed in order from the inspection item with the lowest rank to the inspection item with the highest rank.

Focusing on a single lens to be inspected, by repeating the above flow chart three times, a maximum of three items will be inspected according to the inspection order determined based on the frequency of appearance of defects. That is, the lenses to be inspected that have no defects in all the inspection items are the first, second, and third lenses.
After the inspection items in the order are inspected in order, they are discharged as non-defective products. On the other hand, when any of the inspection items has a defect equal to or higher than the reference value, the inspection items in the subsequent orders are not inspected and are discharged as defective products.

The order setting subroutine shown in FIG. 9 sets the order of priority of inspection items based on the values of various counters set in FIG. The counters used include a defect counter CN1 of the first inspection item (counting the number of defects of the first inspection item (scratches on the upper surface) determined to be defective with a reference value or more and a second inspection item (lower surface)). Defect counter CN2 of the second inspection item that counts the number of defects that are judged to be defective with a reference value or more, and the defect of the third inspection item (internal dust) is judged to be defective with a reference value or more It is a defect counter CN3 of the third inspection item that counts the number of inspections. The symbol "++" in the flowchart
Indicates increment of the counter, and “−−” indicates decrement.

Further, in the flowchart of FIG. 8, the defect counters are specified in order, and it is not shown whether the target inspection item is the first inspection item, the second inspection item, or the third inspection item. These correspondences are determined by the order setting in FIG. For example, in step A-9, the defect counter of the inspection item of the third rank is incremented, but this does not indicate the defect counter of the third inspection item, but the defect counter of the third rank is ranked at the time when this inspection is executed. The defect counter of the set inspection item is shown. On the other hand, the defect counter in FIG. 9 matches the inspection item.

In step B-1 of FIG. 9, the interval setting counter C is decremented, and no processing is performed until the counter C becomes 0, and the process returns to the flowchart of FIG. 8 (step B-2). When the counter C reaches 0, the counter C is reset to n (step B-3), and the values of the defective counters of the respective inspection items are compared to set the order of the inspection items in descending order of the counter value (step B-3). -4 ~ B1
Four).

As a result, the set of three inspection items is n
Each time the inspection is repeated, the order of inspection items is reset in order of increasing frequency of defects occurring during the latest n inspections. When the order is reset, the value of each defect counter is reset to 0 (step B-15), and the process returns to the flowchart of FIG.

[0054]

As described above, according to the present invention, the inspection items having a high detection frequency are preferentially inspected, and therefore, when the defective defect is detected, the items in the subsequent order are detected. It is not necessary to perform the inspection, and the throughput of the entire inspection can be improved as compared with the case where the inspection is performed in a fixed order without considering the frequency.

[Brief description of drawings]

FIG. 1 is a block diagram showing a processing system of an optical member inspection device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an optical system of an optical member inspection device according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing the shape of a test object and the shape of a diffusing means in the apparatus of the embodiment in contrast with each other.

FIG. 4 is an explanatory diagram showing an image when there is no defect in the lens to be inspected, which is imaged by the apparatus of the embodiment.

FIG. 5 is an explanatory diagram showing an image when the lens to be inspected, which is imaged by the apparatus of the example, has an absorptive defect.

FIG. 6 is an explanatory diagram showing an image when a test lens photographed by the apparatus of the example has a scattering defect.

FIG. 7 shows an example of a luminance distribution on one scanning line of an image photographed by the apparatus of the embodiment, (A) is a signal of an original image, (B) is a signal obtained by binarizing a low luminance component, and (C) ) Is a signal obtained by binarizing the high luminance component.

FIG. 8 is a flowchart showing the entire inspection process of the apparatus of the embodiment.

FIG. 9 is a flowchart showing a subroutine of order setting in the inspection flow.

[Explanation of symbols]

 1 Test Lens 10 (10a, 10b, 10c) Light Source 20 (20a, 20b, 20c) Diffusing Means 21 First Diffusing Plate 22 Second Diffusing Plate 30 (30a, 30b, 30c) CCD Camera 40 Image Processing Device 42 Judging Means 43 supply order control means 50 monitor display 60 parts supply device

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

Claims (7)

[Claims] 1. An optical member inspection method for continuously inspecting a plurality of optical members for a plurality of inspection items, wherein defects are detected based on the appearance frequency of defects for each of the inspection items statistically obtained in the inspection process. A method for inspecting an optical member, characterized in that an inspection of an item having a high frequency is performed before an inspection of another item. 2. An optical element to be inspected is determined to be defective when a defect equal to or larger than a reference value is detected in an item previously inspected, and the subsequent inspection item is not executed. The optical member inspection method according to claim 1. 3. An optical member inspection device for inspecting optical members for a plurality of items, wherein inspection of inspection items having a high defect detection frequency is performed based on statistically obtained defect detection frequencies for each inspection item. The optical member inspection device is characterized in that the inspection is performed prior to the inspection of the inspection item having a low frequency. 4. A plurality of image input means provided for each of a plurality of inspection items, a component supply means for continuously supplying an optical member to be inspected to each input position of the image input device, and the image. A determination unit that determines a defect for each inspection item based on an image input from the input unit, and determines that the optical member is defective when a defect that exceeds a reference value for at least one inspection item is detected; The component supply means is controlled based on the appearance frequency of defects for each of the inspection items statistically obtained in the process, and the optical member is preferentially placed at the input position of the image input means of the inspection item for which the defect is frequently detected. An optical member inspection device comprising: 5. The image input means includes a light source, a peripheral region having a high diffuse transmittance and a central region having a low diffuse transmittance,
A diffusing means for diffusing the light flux emitted from the light source; and an imaging means for picking up the light flux transmitted through the diffusing means and for receiving the light flux passing through the optical member which is the test object. The optical member inspection apparatus according to claim 4, further comprising: 6. The optical system according to claim 5, wherein the central region of the diffusing means is set so that the range of a light beam vertically emitted from the central region substantially coincides with the object to be inspected. Material inspection device. 7. The optical member inspection apparatus according to claim 6, wherein each region of the diffusing means has a shape similar to a planar shape of the object to be inspected.