JPH095249A - Apparatus for inspecting optical member - Google Patents

Abstract

PURPOSE: To separate and detect a mold defect from other defects by recognizing a defect of a mold defect candidate as the mold defect when an appearance counter reaches a predetermined recognition count for the mold defect. CONSTITUTION: An object to be inspected is photographed by a CCD camera 30, and an input image from tone CCD camera 30 to an image-processing device 40 is binarized, whereby a defect of the object is extracted. The defect is displayed at 50 and moreover output to a control device 60. The device 60 controls an alarm device 70 and a part feed device 80, and at the same time, detects the generation of a mold defect with the use of a plurality of appearance, non-appearance counters set in a memory 90. In other words, a position and a size of a scattering defect as a mold defect candidate are judged from the defect extracted at 40. Defects appearing at the same points on optical elements molded by the same mold are set as mold defect candidates. An appearing number of times of the mold defect candidates is stored in tone appearance counter. When a value of the appearance counter reaches a predetermined recognition number of times for the mold defect, the device 60 recognizes the mold defect candidates as the true mold defect and instructs the device 70 to alarm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting a transparent optical member made of plastic, and more particularly to an apparatus for detecting scratches formed on a molding die by using an image processing technique.

[0002]

2. Description of the Related Art When a plastic optical member is taken out of a mold, plastic may adhere to and remain on the mold side if the molded product is not sufficiently cured. When the plastic adheres to the mold, a convex portion is formed in the mold. If molding is continued without removing the convex portion, an unnecessary concave portion is formed as a mold flaw in the molded product. Further, when the plastic piece adheres to the mold and is cured for a long time, a concave flaw may remain on the mold even after the plastic piece is detached. In addition, the mold is configured so that the lens molding part can be removed independently,
In some cases, the difference in assembling this part into the mold body may cause scratches. In this specification, the concave defects of the molded product caused by the plastic pieces remaining in the mold in this manner, or the convex defects generated in the molded product by scraping the mold itself are collectively referred to as mold scratches. And

When a mold flaw that is unacceptable as a product is found in a molded product, it must be immediately fed back to the production line to remove the plastic attached to the mold.

[0004]

However, conventionally,
Since the inspectors visually inspected the optical members,
There is a problem that it is difficult to discriminate between the mold defect and other defects, the feedback to the manufacturing line is delayed, and the product yield is deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and provides an optical member inspection apparatus capable of separating a mold flaw from other defects and detecting it by using image processing technology. The purpose is to provide.

[0006]

In the optical member inspection apparatus and inspection method according to the present invention, attention is paid to the fact that mold scratches are defects that continuously occur in the same position of an optical member in the same shape, and image processing technology Is used to determine a pattern flaw from a binarized image by a statistical method.

The input image obtained by photographing the optical member is
Defects that are valued and become mold scratch candidates are extracted, and defects that appear at the same location on an optical element molded with the same mold are used as mold scratch candidates, and the number of appearances is counted by an appearance counter. Since a plurality of pattern defect candidates may appear, a plurality of appearance counters are prepared so that the number of appearances of each type defect candidate can be independently counted. And
When the count value of the appearance counter reaches a predetermined number of die scratch recognition times, the defect of the die scratch candidate counted by the counter is recognized as a die scratch.

Further, even when the appearance of a defect at the same place is temporarily interrupted, if the defect reoccurs within a predetermined discontinuous allowable number of times, it is assumed that the interruption is due to detection failure, and the number of appearances before the interruption is determined. It can also be configured to be used to restart counting. In this case, a plurality of non-appearing counters are provided corresponding to the appearance counters, and the defect does not appear when the defect of the type defect candidate does not appear before the count of the corresponding appearance counter reaches the number of times of the pattern defect recognition. Count the number of times. The appearance counter is reset when the value of the non-appearing counter reaches a predetermined discontinuous allowable number of times, and the non-appearing counter is reset when a defect reappears at the same location before the value reaches the discontinuous allowable number of times. Will be reset.

[0009] It should be noted that it is desirable to provide a warning means for notifying an inspector or the like when a mold flaw is recognized. By issuing a warning using sound or light, the inspector can know that the mold flaw has occurred.

In the input image, the light flux from the light source is diffused by a diffusing means having a central region having a low diffuse transmittance and a peripheral region having a high diffuse transmittance and is incident on the test object, and the light beam transmitted through the test object. It is obtained by photographing the object with a photographing means provided at a position where is reached.

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 light from the central region of low brightness.

When a defect such as a scratch on the surface such as a scratch is present, low-luminance light from the central region is scattered and attenuated in the portion corresponding to this defect, but high from the peripheral region. Since the light of brightness is scattered and reaches the photographing means, as a result, the light quantity of the defective portion on the image plane increases, and appears in the photographed image as a region of higher brightness than the surrounding component region.

[0013]

Embodiments of the optical member inspection apparatus according to the present invention will be described below. The apparatus of the embodiment targets a plastic optical member for inspection. First, a schematic configuration of an optical member inspection device according to the present invention will be described with reference to FIG.

CCD as a photographing means for photographing an object to be inspected
The output signal from the camera 30 is input to the image processing device 40 as a defect extracting means. The image processing device 40 binarizes the input image to extract defects in the test object, displays the extracted information on the monitor display 50, and outputs the information to the control device 60 as a pattern flaw inspection device.

The control device 60 controls a warning means 70 for issuing a warning by light when a mold defect occurs and a component supply device 80 for supplying an optical component to an inspection position.
A plurality of appearance counters respectively provided in the memory 90,
The occurrence of mold scratches is detected using the non-appearance counter.

The control device 60 determines the position and size of the scattering defect, which is a candidate for mold flaw, from the defects extracted by the image processing device 40, and determines the same position on the optical element molded by the same mold. The defect appearing at is regarded as a pattern defect candidate, and the number of appearances thereof is stored in the appearance counter in the memory 90.

When the value of the appearance counter reaches a predetermined number of mold scratch recognition times, the control device 60 recognizes the defect as a mold scratch and outputs a signal to the warning device 70 to issue a warning. The value of the appearance counter is reset when the defect detection is completely interrupted, but if it occurs again after a relatively short interruption, it is assumed that it is due to detection failure and the value of the appearance counter is not reset. Use the previous count value for. Therefore, the control device 60 counts the number of times of non-appearance by the non-appearance counter provided corresponding to the appearance counter in the memory 90, and while the value of the non-appearance counter is equal to or less than the predetermined discontinuous allowable number of times. When a defect is found again in, the count is restarted without resetting the value of the appearance counter.

The appearance counter is reset when its value reaches a predetermined number of die scratch recognition times and when the value of the non-appearing counter reaches a predetermined discontinuous allowable number of times. The non-appearing counter is reset when the value reaches a predetermined allowable number of discontinuities and when a defect which is a candidate for a pattern defect is found before reaching this value.

For example, if the number of recognition of mold flaws is 20 and the allowable number of discontinuities is 5, defects appearing at the same place are judged as mold flaws not only when defects appear 20 times or more in succession, Even if the appearance is interrupted, it includes the case where the total number of occurrences is 20 sporadically unless the number of non-appearances reaches 5 consecutive times.

The control device 60 recognizes the defect of the mold scratch candidate as a mold scratch under the above conditions, a first resetting means for resetting the value of the appearance counter, and a first resetting means for resetting the value of the non-appearing counter. 2 and the function of the reset means.

Subsequently, the CCD camera 30 will be described with reference to FIG.
The configuration of the optical system for forming an image captured by will be described.

The optical system of the apparatus comprises a light source 10 and this light source 1.
First and second diffuser plates 2 for diffusing the light flux emitted from 0
And a diffusing means 20 composed of 1 and 22,
The CCD camera 30 takes in the light flux that has passed through the diffusing means 20 and the positive lens 1 that is the test object and the light flux that has passed through the circumference of the test lens 1 and takes an image.

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 diffusing plates 21 and 22 are substantially similar to the planar shape of the lens 1 to be inspected, and the area of the second diffusing plate 22 is smaller than that of the first diffusing 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 to be inspected is the finder lens 1a having a rectangular planar shape, the first and second diffusion plates 21a and 22
The plane shape of a is preferably a rectangle as shown in FIG. 3 (A-2). When the lens to be inspected is a general circular lens 1b as shown in FIG. 3 (B-1), the plane shapes of the diffusion plates 21b and 22b are shown in FIG. 3 (B-2). It is desirable to use a round street.

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, a lens to be inspected is gated 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 adjusting the range of the vertical emission component from the central region to the shape of the lens 1 under test, that is,
By making the shape of the second diffusion plate 22 similar to the planar shape of the lens 1 to be inspected, the component area where the lens to be inspected is arranged and the background area are clearly distinguished in the image as described above. Therefore, the separation process of the target area in the image processing described later becomes extremely easy.

When the second diffusion plate 22 is not provided, the component area has a somewhat lower brightness than the background area due to absorption and diffusion by the parts, but there is no clear difference in brightness as in the embodiment. Does not happen.

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.

Further, if there is a defect that scatters light on the surface of the lens 1 to be inspected, such as white dust or scratches (including mold scratches) on the surface of the optical member, the light scatters due to this defect,
If there is no defect, the range O of the lens image on the CCD sensor 32
A part of the high-intensity oblique emission component Lop from the peripheral region that does not reach the range reaches the range O of the lens image, and as shown in FIG. Occurs.

For example, when a low-brightness image DL due to an absorptive defect and a high-brightness image DH due to a scattering defect are present on a certain scanning line in the X-axis direction, the pixel row output along this scanning line is output. 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.

As described above, the two diffusers are used to set the light quantity distribution of the illumination light in two steps, so that in the case of an absorptive defect in the component area S whose brightness is lower than the background area B, Can recognize defects as an image DL having a brightness lower than that of the component region S and a high brightness image DH in the case of a scattering defect, so that defects having different properties can be simultaneously detected from one image data. it can.

Next, the procedure of measurement using the above apparatus will be described with reference to the flow chart. As a preparation before the inspection, information about parts corresponding to the optical member to be inspected is loaded as a data table. Also, according to the information, select the diffusion plate suitable for the shape of the part,
Set the shooting magnification.

The flow of the entire inspection is shown in the flow chart of FIG. Input the image from CCD camera (Step A-
1), the component area corresponding to the image of the lens to be inspected is separated based on the brightness distribution (step A-2).

When it is determined that the component is missing at a predetermined inspection position during the component area separation processing, a defect flag is set during the component area separation processing, and this defect flag is set in the inspection loop. Whether or not to continue the inspection is selected depending on whether or not (step A-3).

The image of the separated parts area is separated into a scattering defect having a higher brightness than the base brightness and an absorptive defect having a lower brightness by the dynamic binarization process (step A-4). A feature amount such as is extracted (step A-5).

In Steps A-6 and A-9, the occurrence and disappearance of mold scratches are inspected (subroutines shown in FIGS. 9 and 10). When the mold scratches occur or disappear, the inspector immediately uses an alarm device. Will be announced (Steps A-7, 8, 10, 11).

The image processing device 40 determines the quality of the lens to be inspected based on the extracted result (step A-12) and displays the determination result on the monitor display 50 (step A-13). In step A-14, it is determined whether or not there is a next part to be inspected, and if there is a part, the part is replaced (step A-15) and the processing from step A-1 is repeated,
If there are no parts, the inspection ends.

Next, the subroutines for detecting the scratches and managing the scratches included in the above inspection flow are shown in FIGS.
It will be described based on.

In the pattern flaw detection process shown in FIG. 9, the pattern flaws are extracted from the binarized image by a statistical method, and as a general rule, a figure scratch that appears consecutively at the same position for a predetermined number of times or more is recognized. Is detected. In addition, when the test object is molded by a multi-cavity mold, the data of the mold scratch candidate is saved for each cavity, and the test object to be inspected is stored in the molded cavity. The corresponding data is sequentially read and used.

The input is the barycentric coordinates of the figure in the binarized image,
Number M of figures, barycentric coordinates of candidate pattern flaws, number K of candidate pattern flaws, position error margin R when determining the difference between figures based on the coordinates of center of gravity, number S of recognition of pattern flaws considered as a pattern flaw, and allowable number of discontinuities C (Step B-1).

In the following processing, it is judged in Steps B-2 to 17 whether or not there is a matching figure with reference to the pattern defect candidate, and the existing pattern defect candidate is registered as a pattern defect or deleted from the candidate. After this is completed, in Steps B-18 to 26, a new type scratch candidate is added while avoiding duplication with the existing type scratch candidate based on the figure.
If both the pattern scratch candidate and the number of figures are “0”, after the processing and determination in steps B-1, 2, 3, 18, and 19, no substantial processing is performed and the inspection loop is executed. Return.

When there is a type defect candidate, it is determined whether or not a figure matching the type defect candidate exists based on the distance between the barycentric coordinates of the type defect candidate and the barycentric coordinate of the figure.
(Step B-2 to 8). If there is a figure that matches the pattern defect candidate, the number of consecutive appearances, which is an index of the appearance frequency, is incremented and the number of consecutive non-appearances is reset to 0 (steps B-9, 10).

When the number of consecutive appearances exceeds the predetermined number S of recognized pattern scratches, it is determined that a pattern defect has occurred, the pattern defect detection flag is set, and this candidate is registered as a pattern defect.
(Steps B-11-14). The data to be registered are the coordinates of the center of gravity of the mold flaw and the cavity number of the found part.

If there is no figure that matches the type scratch candidate even after checking all the figures, the continuous failure limit number of the pattern scratch candidates is incremented, and if this is larger than a predetermined discontinuous allowable number, the pattern Delete the scratch candidate, and if it is smaller, continue checking the next scratch candidate (step B-5, 1).
6,17,15).

When all the pattern defect candidates have been collated, it is next judged whether or not there is a matching pattern defect candidate for each figure (steps B-18 to 25). Is added as a new scratch candidate (step B-26).

By the above-mentioned processing, it is possible to detect defects that occur successively by statistically evaluating defects.

The mold defect management process shown in FIG. 10 is a process for detecting the disappearance of the mold defect that has occurred. Plastic that adheres to the mold, which causes mold scratches, may adhere to the molded product and peel off from the mold during the molding process.If mold scratches occur during the mold scratch detection process, the mold will be damaged immediately afterwards. If the flaw disappears, no feedback to the production line is needed.

The pattern defect management process is configured by simplifying the pattern defect detection process, and it is determined whether or not there is a matching figure for all the pattern defects (steps C-2 to 8). , The number of consecutive non-appearances is reset to 0, and the determination of the next mold flaw is continued (step C-9, 10).

If there is no matching figure, the number of consecutive non-appearances is incremented (step C-11), and if it is the predetermined allowable number C of discontinuities or more, the registration of the pattern flaw is deleted and the pattern flaw is deleted. Set the erase flag (step C-13,
14). When the matching for all the pattern flaws is completed, the process returns to the inspection loop and continues.

By the above-described mold flaw management processing, it is possible to monitor whether the mold flaws detected by the mold flaw detection processing are continuously appearing or disappeared. Statistical management of scratches is possible.

[0055]

As described above, according to the present invention, it is possible to statistically detect the mold flaw generated on the object to be inspected by the plastic piece adhering to the lower valley based on the image of the object to be photographed. Therefore, the feedback to the manufacturing line can be promptly performed to improve the product yield.

[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 for detecting a mold flaw in the inspection flow.

FIG. 10 is a flowchart showing a subroutine for mold flaw management in the inspection flow.

[Explanation of symbols]

 1 lens to be inspected 10 light source 20 diffusing means 30 CCD camera 40 image processing device 50 monitor display 60 control device 70 warning device 80 component supply device 90 memory

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

Claims (5)

[Claims] 1. An input image obtained by photographing an optical member.
Defect extraction means that digitizes defects that are candidates for mold scratches, and multiple appearances that count the number of appearances of defects that appear at the same location on an optical element molded by the same mold as mold scratch candidates An optical member inspection device comprising: a counter; and a certifying unit that certifies a defect of a candidate for a mold defect as a mold defect when the appearance counter reaches a predetermined number of times of recognition of a mold defect. 2. A plurality of appearance counters are provided so as to correspond to the appearance counters, and when a defect of the type flaw candidate does not appear before the count of the corresponding appearance counter reaches the number of die flaw recognition times, the number of times of occurrence of the defect does not appear. A non-appearing counter for counting, a first reset unit for resetting the value of the appearing counter when the value of the non-appearing counter reaches a predetermined discontinuous allowable number, and a discontinuity allowance for the value of the non-appearing counter. The optical member inspection apparatus according to claim 1, further comprising a second reset unit that resets the value of the non-appearance counter when a defect reappears at the same location before the number of times is reached. 3. The optical member inspection device according to claim 1, further comprising warning means for notifying a die scratch when it is certified. 4. The input image is obtained by diffusing a light flux from a light source by a diffusing means having a central region having a low diffuse transmittance and a peripheral region having a high diffuse transmittance and making the light incident on the object to be examined. The optical member inspection device according to claim 1, wherein the optical member inspection device is obtained by capturing an image of the object to be inspected by an image capturing unit provided at a position where a light flux that has passed through. 5. An input image obtained by photographing an optical member
Defect extraction means that digitizes defects that are candidates for mold scratches, and multiple appearances that count the number of appearances of defects that appear at the same location on an optical element molded by the same mold as mold scratch candidates A counter and a plurality of counters are provided corresponding to the appearance counter, and when the defect of the type scratch candidate does not appear before the count of the corresponding appearance counter reaches a predetermined number of times of recognition of the type scratch,
A non-appearance counter that counts the number of times that does not appear, the appearance counter when the value of the appearance counter reaches the number of mold scratch recognition times, and when the value of the non-appearance counter reaches a predetermined discontinuous allowable number A first resetting means for resetting the value of, and a case where a defect reappears at the same location before the value of the non-appearance counter reaches the discontinuous allowable number, and a case where the discontinuous allowable number is reached. A second reset means for resetting the value of the non-appearance counter; and a certifying means for certifying a defect of the mold scratch candidate as a mold scratch when the appearance counter reaches the number of times of recognition of the mold scratch. Optical member inspection device.