JPH0552766A - Surface defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To obtain a surface defect inspecting apparatus which can inspect highly accurately the presence/absence of the surface defect such as a scratch, a pin hole or the like on the curved surface of a work. CONSTITUTION:This apparatus is provided with a light source 1 for casting the light to the surface of a work A, a photographing device 2 for receiving the reflected light of the light cast by the light source 1, and a defect detecting part 4 which detects the presence/absence of a surface defect from the light and shade of the image photographed by the photographing device 2. A radiation controlling member 10 is set between the light source 1 and the work A which is alternately provided with thin strips of light permeating parts 11 and thin bands of light shielding parts 12. Accordingly, the detecting accuracy of defects is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus for inspecting the presence or absence of a surface defect on a work such as an aluminum (including its alloy) photosensitive drum substrate.

[0002]

2. Description of the Related Art For example, an aluminum photosensitive drum substrate is required to have a high surface accuracy of a mirror surface or a state close to it in terms of its quality, and it is also required to be locally free from surface defects such as scratches, pinholes and blisters. It Therefore, in the manufacturing process of the aluminum photosensitive drum substrate that is generally manufactured through each process such as precision cutting, polishing, plating, and polishing, the presence or absence of surface defects is inspected after the completion of a predetermined process or after the entire process. Things are being done.

Conventionally, the above-described surface defect inspection has mainly been a visual inspection by an inspector with the naked eye, but recently, a surface defect inspection method and apparatus for detecting a defect by an optical method instead of manually. Has been proposed (for example, Japanese Patent Laid-Open No. Sho 6).
2-269049, JP-A-63-42453 and the like).
However, such a conventional surface inspection method and the same device, not only the presence or absence of a defect, is to determine various types of defect information such as defect type, existing position, and size, although high-level defect information can be obtained. Each of them has a drawback that the structure is complicated and it takes a relatively long time to find out the inspection result.

Therefore, the applicant of the present application has previously proposed a surface defect inspection apparatus capable of rapidly inspecting the presence or absence of a surface defect of a work (Japanese Patent Application No. 3-38659). This surface defect inspection apparatus includes a light source that irradiates the surface of a workpiece with light, an imaging device that receives reflected light of the light emitted by the light source, and the presence or absence of surface defects based on the contrast of the image captured by the imaging device. And a surface detection device for detecting the surface defect, and the presence or absence of a surface defect can be quickly detected with a simple configuration.

[0005]

However, although there is no particular problem with a flat work surface such as a magnetic disk substrate, a work surface such as a photosensitive drum substrate having a curved surface is inspected. In this case, there were the following problems.

That is, as compared with the case of inspecting a work having a flat surface such as a magnetic disk substrate,
When inspecting a work surface having a curved surface, the probability that a good product is determined to be a defective product tends to be relatively high. Further, depending on the shape of the scratch, it may or may not be detected. That is, as shown in FIG. 6 (a), a scratch having a shape that is deeply and sharply scooped and the peripheral edge is raised can be detected almost certainly, but as shown in FIG. 6 (b), a gentle concave surface is formed. In the case of a scratch having a shape called a so-called indentation, it is difficult to detect it, and it may be overlooked.

The present invention has been made in view of the above-mentioned problems, and even a work having a curved surface such as an aluminum photosensitive drum substrate can increase the surface defect detection sensitivity. An object is to provide a defect detection device.

[0008]

However, as a result of intensive experiments and research conducted by the present inventors to solve the above-mentioned problems, in the conventional device, the work surface should be uniformly irradiated with the light from the light source. Focusing on the fact that a milky-white light-diffusing resin cover was placed on the light source, we have found a method that can improve detection accuracy by fundamentally reviewing this idea and conducting further experiments and research. Thus, the invention was completed.

According to the present invention, the light from the light source is applied to the surface of the work with a stripe-shaped light and dark.
An irradiation control member having a narrow width light-shielding portion and a light-transmitting portion alternately arranged is disposed between the light source and the work.

That is, according to the present invention, a light source for irradiating the surface of a work with light, an image pickup device for receiving the reflected light of the light emitted by the light source, and a surface defect depending on the density of the image picked up by the image pickup device. A surface defect detection device having a defect detection unit for detecting the presence or absence of, between the light source and the workpiece, having a narrow width light-transmitting section and a narrow width light-shielding section alternately arranged, It is a gist of a surface defect detecting device characterized in that an irradiation control member for irradiating a light from a light source with a stripe-shaped light and dark is arranged on a surface of a work.

[0011]

The operation of the present invention will be described with reference to FIG. The light source (1) intermittently emits light toward the aluminum photosensitive drum base (A), and in synchronization with the light emission, specularly reflected light from the base (A) is received by the image pickup device (2) to capture an image of the surface of the base. .. The specular reflection light received by the image pickup device (2) is incident on each pixel of the image pickup device (2), and grayscale information corresponding to the amount of incident light is output. Therefore, when a defect such as a scratch is present on the surface of the substrate (A), the irradiation light of the light source (1) is diffusely reflected by the defect, and as a result, the amount of specular reflection light incident on the corresponding pixel is reduced, and the specular reflection light is reduced. Is properly received, the output is different from the other pixels.

A signal from the image pickup device (2) is input to the defect detection section (4). The defect detection unit (4) compares the input gray level signal of each pixel with the gray level reference signal set to a predetermined level by the gray level setting unit (5), and if the input signal is smaller, the surface The presence / absence of a defect is detected by determining that there is a defect, and determining that there is no defect if the input signal is larger.

On the other hand, the light source (1) has narrow light-transmitting portions (11) and narrow light-shielding portions (12) arranged alternately.
Since the irradiation control member (10) for irradiating the work surface with light from the light source in a striped light-dark pattern is provided, the surface of the photosensitive drum substrate (A) is illuminated in a striped light-dark pattern. Therefore, the amount of specularly reflected light per unit area incident on each pixel of the image pickup device (2) is reduced as compared with the conventional case where the surface of the work is uniformly illuminated.

However, when the work surface has a defect such as a scratch, the reduction rate of the specular reflection light amount per unit area increases conversely. Therefore, the detection accuracy is improved as compared with the conventional uniform irradiation method.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment in which an aluminum photosensitive drum substrate is used as a work and an apparatus for inspecting its surface defect is applied.

In FIG. 1, (A) is an aluminum photosensitive drum base as a work, and a light source (1) for obliquely irradiating the surface of the aluminum photosensitive drum base outwardly and obliquely above the photosensitive drum base (A). Has a space of 320 m from the base (A)
It is set to m. The light source (1) is configured to intermittently emit light at a predetermined timing, and has a cover (10) as an irradiation control member having a narrow light-transmitting portion (11) and a narrow light-shielding portion (12) alternately arranged. ).

Above the photosensitive drum substrate (A), an image pickup device (2) for receiving the specularly reflected light of the light emitted from the light source (1) to the photosensitive drum substrate (A) is connected to the substrate (A). The distance is set to 345 mm. The image pickup device (2) receives regular reflection light from the substrate (A) and shoots an image on the surface of the photosensitive drum substrate. A CCD camera is a preferable example of the image pickup device (2) in this embodiment. Is used. The light source (1) and the imaging device (2) are
It is arranged so as to form an angle of 40 degrees when viewed from the base body (A).

The image pickup surface of the image pickup device (2) is composed of a plurality of pixels, and an electric signal corresponding to the amount of specularly reflected light from the substrate (A) received by these pixels is used as image grayscale information for each pixel. It is supposed to be output to. Therefore, if a defect such as a scratch is present on the surface of the substrate, the reflected light is scattered at the defect portion, so that the amount of specularly reflected light incident on a specific pixel is reduced as compared with the case where the defect is not present, which is an electrical defect. It is said that the difference in signal magnitude is output.

As described above, in this embodiment, the so-called bright field method in which the specularly reflected light from the substrate (A) is directly received by the image pickup device (2) is adopted, but this is for the following reason. That is,
In the bright-field method, when the irradiation light is diffusely reflected due to a defect on the surface of the substrate, the light that is diffusely reflected and does not enter the image pickup device (2) is directly reduced by the image pickup device, while the irregular reflection is caused. It is difficult for the dark field method to receive all of the diffusely reflected light, and trying to satisfy this makes the device complicated. Therefore, the sensitivity of the bright field method to the increase or decrease in the amount of light due to surface defects is better,
This is because the reliability of defect detection can be improved.

By the way, according to the present invention, FIG.
As shown in FIG. 5, the light source (1) is provided with a cover (10) as an irradiation control member having a narrow light-transmitting portion (11) and a narrow light-shielding portion (12) alternately arranged. .. The reason for providing such an irradiation control member (10) is as follows.

That is, when the irradiation control member (10) as described above is provided in the light source (1), the light of the light source (1) is applied to the surface of the photosensitive drum substrate (A) in a stripe-shaped light and dark. It When the light is illuminated in a striped light / dark pattern in this way, the amount of specularly reflected light per unit area incident on each pixel of the image pickup device (2) is reduced as compared with the conventional case where the work surface is uniformly illuminated. It will be. However, when the work surface has a defect such as a scratch, the rate of decrease in the amount of specularly reflected light per unit area is increased on the contrary, so that the detection accuracy is improved as compared with the conventional uniform irradiation method. ..

In this embodiment, as the cover (10), a transparent substrate (10a) made of a synthetic resin as shown in FIG. 4 is developed, and a width of 2 mm is shown as enlarged in FIG.
A thin light-shielding tape (12) (La) is attached at intervals of 3 mm (Lb). However, instead of such a tape, a light-shielding paint may be applied to a light-transmitting substrate, or a slit may be formed in the light-shielding substrate. In any case, as the cover (10), the narrow light-transmitting portion (1
It suffices to use the one having 1) and the narrow light-shielding portion (12) in an alternating arrangement.

The width of the thin strip-shaped transparent portion (11) is 2 to
It is desirable to set it in the range of 4 mm, and it is desirable to set the width dimension of the light shielding part (12) in the range of 1.5 to 2.5 mm. In any case, even if it is set below the lower limit value, the manufacturing of the cover becomes extremely troublesome and the inspection accuracy cannot be expected to improve. On the contrary, if the upper limit value is exceeded, the cover manufacturing becomes easy, but the inspection accuracy is remarkable. This is because improvement cannot be expected. Further, it is most desirable to set the dimensional ratio of the width of the light transmitting part (11) and the width of the light shielding part (12) to about 1: 1.5.

In this embodiment, the cover attached to the light source (1) is used as the irradiation control member (10), so that the cover can be prevented from being contaminated to a minimum and the work (A) can be easily moved. However, the irradiation control member (10) is not limited to this, and is disposed between the light source (1) and the work (A) with a distance from the light source (1). You may. In short, the light source (1)
It may be arranged between the work and the work (A). A red light emitting diode is preferably used as the light source (1).

The signal for each pixel output from the image pickup device (2) based on the light from the light source (1) is electrically processed thereafter.

An example of this processing circuit is also shown in FIG.

In FIG. 1, (3) is a video board as an input section for receiving a signal from the image pickup device (2),
(4) is a defect detection circuit. The defect detection circuit (4) receives an input signal for each pixel according to the density of the image sent through the video board (3) and the density set to a predetermined level by the level setting device (5). When the input signal is smaller than the reference signal, it is determined that there is a surface defect, and when the input signal is larger, it is determined that there is no defect, and thus the presence or absence of the defect is detected.

The density reference signal set by the density level setting unit (5) directly relates to the presence / absence of a defect, and the criterion for judging the presence / absence of a defect can be relaxed depending on the setting. It is said that the setting level can be arbitrarily changed according to the required quality.

Reference numeral (6) is a counting circuit for counting the number of pixels determined to be defective by the defect detection circuit (4).
Further, (7) is a comparison circuit for comparing the number of pixels with surface defects counted by the counting circuit (6) with the defect number setting value preset to an allowable value by the defect number setting device (8). If the number of pixels with surface defects is larger than the set value, it is judged as a defective product, and if it is small, it is judged as a good product. Thus, the defect number setting value preset to the allowable value by the defect number setting device (8) directly relates to the quality of the aluminum photosensitive drum substrate (A), and the quality standard is relaxed depending on the setting. It is said that the set number can be arbitrarily changed according to the required quality.

(9) is a display device for displaying the judgment result of the comparison circuit (7) by a lamp or the like.

Next, a method for inspecting a surface defect of the aluminum photosensitive drum substrate (A) using the apparatus shown in FIG. 1 will be described.

First, while intermittently emitting light from the light source (1) toward the photosensitive drum substrate (A), the specularly reflected light from the substrate (A) is received by the image pickup device (2) in synchronization with the emission, and the surface of the substrate is received. Take an image. The regular reflection light is made incident on each pixel of the image pickup device (2), and the grayscale information corresponding to the amount of incident light is output. Therefore, when a defect such as a scratch is present on the surface of the substrate (A), the irradiation light from the light source (1) is diffusely reflected by the defect, and as a result, the amount of light incident on the corresponding pixel is reduced and the specular reflection light is reduced. It produces a difference in output with respect to the other pixels that are properly received.

The signal from the image pickup device is a video board (3).
It is input to the defect detection circuit (4) via. The defect detection circuit (4) compares the input gray level signal of each pixel with the gray level reference signal set to a predetermined level by the gray level setting device (5), and if the input signal is smaller, the surface The presence / absence of a defect is detected by determining that there is a defect, and determining that there is no defect if the input signal is larger. This detection result is sent to the counting circuit (6) and the number of pixels determined to be defective by the counting circuit (6) is counted.

Next, the counting result of the counting circuit (6) is input to the comparison circuit (7), and the number of pixels with surface defects and the defect number setting value preset to an allowable value by the defect number setting device (8). And are compared. As a result, if the number of pixels with surface defects is larger than the set value, it is determined that the photosensitive drum is defective, and if it is small, it is determined that the photosensitive drum is good. Then, the determination result is displayed on the display device (9), and the quality of the substrate is determined.

As described above, according to the present invention, the presence or absence of a defect on the surface of the substrate is detected by the density of each pixel of the image pickup device. Therefore, the detection accuracy can be further improved by enlarging and photographing the inspection surface. .. Therefore, it is desirable to divide the surface of the aluminum photosensitive drum substrate (A) into a plurality of minute inspection areas, and magnify an image of each inspection area by an image pickup device to detect the presence or absence of surface defects.

As a more specific method, as shown in FIG. 2, three image pickup devices (2), (2) and (2) are arranged at predetermined intervals and the photosensitive drum substrate (A) is circumferentially arranged. By rotating, the surface of the substrate is first inspected continuously in a circumferential band. The number of rotations should be set so that an uninspected area is not formed in the circumferential direction in consideration of the photographing timing. In this embodiment, a photosensitive drum substrate (A) having an outer diameter of 30 mm and a length of 346 mm is inspected by dividing the substrate surface into three inspection areas in the longitudinal direction.

After rotating the substrate (A) once in this way,
A light source (1) and an imaging device (2) as shown by the arrow in FIG.
(2) (2) is simultaneously moved in the longitudinal direction of the drum substrate (A) by a predetermined width step to continuously inspect the next adjacent area in the circumferential direction.

The moving distance of the image pickup device (2) in the longitudinal direction of the drum substrate should be set so that an uninspected area is not formed in the longitudinal direction. In this embodiment, the substrate (A) is used.
On the other hand, each image pickup device (2) is in charge of each inspection area divided into three in the longitudinal direction, and each image pickup device (2) moves in steps in each inspection area. The number of divisions in the circumferential direction and the longitudinal direction is appropriately determined according to the size of the detected defect according to the purpose and quality.

The inspection time for one substrate is determined by the number of divided inspection areas, the light emission period of the light source (1), the idle time required for moving the image pickup device (2), and the like. For example, when the light emitting period of the light source (1) is 1/48 second, and the inspection area of the photosensitive drum substrate is divided into three in the longitudinal direction, the inspection can be performed in about 2 to 4 seconds.

By thus fixing the image pickup device and rotating the aluminum photosensitive drum substrate, the surface of the substrate is continuously inspected in a strip shape in the circumferential direction, and the image pickup device is moved in the longitudinal direction for each rotation of the substrate. When the structure in which the step movement is performed is adopted, the surface of the substrate can be divided into minute inspection areas and expanded inspection can be performed, and the defect detection can be smoothly performed with even higher accuracy. Further, by arranging a plurality of image pickup devices (2), the inspection time can be shortened.

In the above embodiment, the case of inspecting a work such as a photosensitive drum substrate having a curved surface for the presence of surface defects has been described as an example. However, the present invention has a flat surface. It is also suitably applied when inspecting a work such as the magnetic disk substrate.

[0042]

According to the present invention, as described above, the reflected light of the light radiated to the surface of the work such as the aluminum photosensitive drum base is received by the image pickup device and an image of the surface of the base is photographed. Since the presence / absence of the surface defect is detected from the light and shade, the presence / absence of the surface defect can be quickly detected with a simple configuration. Moreover, an irradiation control member is provided between the light source and the work, in which narrow-width light-transmitting portions and narrow-width light-shielding portions are alternately arranged, and the light from the light source is irradiated on the surface of the work in a stripe-shaped brightness. It is set up. Therefore, the work surface is illuminated with light and dark stripes, and the amount of specularly reflected light incident on each pixel of the image pickup device per unit area is reduced as compared with the conventional case where the work surface is uniformly illuminated. When the work surface has a defect such as a scratch, the reduction rate of the amount of specular reflection light per unit area increases conversely. Therefore, the detection accuracy is improved as compared with the conventional uniform irradiation method.

Incidentally, the surface defect inspection apparatus in which the cover shown in the above-mentioned embodiment is arranged in the light source (Example) and the surface defect inspection apparatus in which the conventional cover made of translucent synthetic resin of milky white is arranged (Comparative example). When the surface of the aluminum photosensitive drum substrate was inspected under the other conditions, the pass rate of non-defective products and the leak rate of defective products were as shown in Table 1.

[0044]

[Table 1]

From the results in Table 1 above, it was confirmed that the defect detection accuracy can be improved by disposing the cover having the narrow light-shielding portions and the light-transmitting portions alternately arranged in the light source. ..

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a surface defect detection device according to the present invention.

FIG. 2 is a schematic side view for explaining a state where the surface of the aluminum photosensitive drum substrate is inspected by using the surface defect detecting device according to the present invention.

FIG. 3 is a perspective view of a light source.

FIG. 4 is a plan view showing a cover of the light source in a developed state.

FIG. 5 is a plan view showing a part of FIG. 4 in an enlarged manner.

6A and 6B are cross-sectional views of a portion having a scratch on the work surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 1a ... Irradiation control member (cover) 2 ... Imaging device 4 ... Defect detection part A ... Aluminum photosensitive drum base (work) 11 ... Translucent part 12 ... Shading part

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G06F 15/62 400 9287-5L H04N 7/18 B 8626-5C

Claims (1)

[Claims] 1. A light source (1) for irradiating the surface of a work (A) with light, an imaging device (2) for receiving reflected light of the light emitted by the light source (1), and the imaging device (2). ) Is a surface defect detection device comprising a defect detection unit (4) for detecting the presence or absence of a surface defect from the grayscale of the image captured by the above (1), and between the light source (1) and the work (A), An irradiation control member (10) having narrow light-transmitting portions (11) and narrow light-shielding portions (12) alternately arranged, and irradiating the work surface with light from the light source (1) in stripes of light and dark. A surface defect detection device comprising: