JP4190636B2 - Surface inspection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inspection apparatus for inspecting defects such as scratches existing on the surface of a plate, strip or disk by capturing an image of the surface of the plate, strip or disk using an imaging device and analyzing the image. .
[0002]
[Prior art]
When manufacturing products such as plates, strips or discs, defects such as scratches may be formed on the surface of the product during the manufacturing process, and in-process products with defects such as these scratches are post-processed. In order to prevent it from being sent to, it is necessary to perform an inspection. Hereinafter, among products such as plates, strips, and disks, a disk will be described as an example.
[0003]
An aluminum substrate is often used as a disk substrate used in an information storage device such as a hard disk drive, and its manufacture is performed in the following steps. That is, the aluminum plate rolled in the rolling process is punched in the blank process, and after the inner and outer peripheral shape processing and the surface polishing are performed in the substrate process, nickel-phosphorus plating is performed on the surface, and the media layer is sputtered from above. An aluminum disk substrate is formed by film formation.
[0004]
In the blank process, the disk substrate punched to a predetermined inner and outer diameter is processed in the subsequent substrate process, and the inner and outer circumferences are processed and the surface is polished to maintain the flatness of the disk surface at 5 μm or less. However, if there are defects such as deep scratches or large rust on the surface of the aluminum disk punched in the blank process, there is a problem that it cannot be removed even by polishing work in the substrate process, resulting in a defective product. In order to prevent this, in the final process of the blank process, in addition to inspection of dimensions and shape, inspection of defects such as scratches on the disk substrate surface is performed.
[0005]
For example, as an inspection apparatus in the blank process, an optical inspection apparatus including an imaging device 11 and an illumination device 12 as shown in FIG. 8 is generally known. The illuminating device 12 illuminates the aluminum disk substrate D conveyed by the conveying device 7, and the image of the aluminum disk substrate D is captured by the imaging device 11 disposed above the aluminum disk, and the presence or absence of defects such as scratches on the disk surface is detected. Judgment is being made.
[0006]
However, there are many types of surface defects on the surface of the disk substrate, such as scratches, line marks, dents, deposits such as oil and dust, and other defects (hereinafter referred to as defects such as scratches on the disk surface). In the above inspection apparatus, the illumination means is only one illumination of the illumination apparatus 12, and therefore the type of surface defect that cannot be recognized depending on the projection direction to the disk substrate that is the object to be measured. There is a problem that there is. For example, when the illuminating device 12 is arranged so as to be a bright field region for the imaging device, if a surface defect of a type that cannot be recognized unless it is a dark field region exists on the disk surface, the surface defect is not detected in the inspection by the surface inspection device. There is a problem of not being aware of its existence.
[0007]
In addition, minute irregularities that affect the reflection of light are formed in a certain direction on the surface of the disk substrate D conveyed to the inspection device in the blank process (hereinafter, these irregularities are referred to as “hairlines”). Since the direction of is not always constant when the disk substrate D is sent to the inspection device, in the above optical inspection device, the reflected light from the illumination becomes scattered and reflected depending on the direction of the hairline of the aluminum disk, There is a problem that the contrast cannot be secured, and as a result, the presence of surface defects on the disk substrate cannot be confirmed.
[0008]
An area sensor (two-dimensional) or a line sensor (one-dimensional) is used as the imaging device of the imaging device 11 described above, but in the case of an imaging device using the area sensor as an imaging device, the disk substrate D is temporarily stopped to perform imaging. Therefore, the above problem can be solved by switching a plurality of illuminations and capturing a plurality of images. However, since it is necessary to stop the disk substrate D, there is a problem that the productivity is deteriorated. On the other hand, in the case of an imaging device using a line sensor as an imaging device, imaging is performed during continuous movement, so that productivity is not deteriorated, but in order to obtain a plurality of images, it is necessary to provide a plurality of inspection stations. There is a problem that there is.
[0009]
[Problems to be solved by the invention]
In view of the above problems, the present invention can capture an image that can reliably recognize a surface defect regardless of the type of surface defect, and can reduce the inspection time by inspecting without stopping the disk substrate. Another object of the present invention is to provide an inspection apparatus that has a simple configuration and requires less cost.
[0010]
It is another object of the present invention to provide a surface inspection system capable of determining the presence or absence of surface defects regardless of the hairline direction of the aluminum disk being conveyed.
[0011]
[Means for Solving the Problems]
The surface inspection apparatus of the present invention illuminates the surface of an object to be inspected by an illuminating means, images reflected light from the surface with an imaging means, and performs an arithmetic processing on an image output from the imaging means with an image processing apparatus. A surface inspection apparatus for inspecting the surface irregularity defect, wherein the illumination means is a light source for dark field that projects from a direction and angle that becomes a dark field and a light field that projects from a direction and angle that becomes a bright field a light source, and a plurality of light sources for projecting from different positions, provided with a single line sensor camera as the imaging means, during said movement of the object to be inspected, the scanning of the line sensor camera 1 line every attempted, to obtain an image captured by irradiation of the plurality of different light sources light source and the light source for the bright field in one line sensor camera by switching alternately the dark field It is characterized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.
[0016]
FIG. 1 is an explanatory diagram illustrating a configuration of an imaging apparatus in an imaging station of the apparatus according to the present exemplary embodiment. The disk substrate D is transported at a constant speed while being kept horizontal by the transport device 7, and the illumination lamps 2a and 2b are arranged so as to illuminate the surface of the disk substrate D from different directions. Further, a line sensor camera 1 for capturing an image of the disk substrate D is provided above the transport device, and the line sensor camera 1 captures an image of the surface of the disk substrate D illuminated by the illumination lamps 2a and 2b. To the control device 3. The control device 3 includes an image processing unit 4, and after image processing is performed on the image signal output from the line sensor camera 1, the presence or absence of a surface defect is determined based on a predetermined determination criterion. A monitor 6 is connected to the control device 3 so that the illumination conditions of the illumination lamps 2a and 2b and the state of the surface of the disk substrate D can be observed.
[0017]
The line sensor camera 1 is an image pickup apparatus incorporating a line sensor that is a one-dimensional image pickup element as an image pickup element, and is disposed at a predetermined position on the disk substrate transfer device 3 above the disk substrate transfer device 7 and passes through the disk substrate. An image of the surface is taken by repeating scanning in units of one line.
[0018]
The illumination lamps 2a and 2b are illumination devices that illuminate the disk substrate. The illumination lamps 2a and 2b are driven by the illumination power source 5 and are controlled to be turned on and off by the control device 3. Although two illumination lamps are shown in FIG. 1, the number of illumination lamps is not limited to two, and a large number of lamps may be arranged to illuminate the disk substrate from different directions. The illumination lamps 2a and 2b are arranged with their positions and directions adjusted so as to illuminate a predetermined position on the disk substrate transport apparatus from different directions. Further, the illumination lamps 2a and 2b are preferably those that illuminate the disk substrate at a predetermined position with as uniform illuminance as possible. Further, since it is necessary to repeatedly turn on and off at high speed and frequently, the rise and fall It is desirable to use a lamp with good falling characteristics.
[0019]
The control device 3 captures the output of the line sensor camera 1 in the built-in image processing unit 4 and performs image processing to form an image on the surface of the disk substrate. The surface defect is determined according to the determination criteria. Further, by controlling the switching of the illumination lamps 2a and 2b and the timing of image scanning of the line sensor camera 1, it becomes possible to capture images with different illuminations with one line sensor camera. A monitor 6 is connected to the control device 3, and it is helpful in checking the lighting conditions of the lighting lamps 2a and 2b and the state of the surface of the disk substrate D to adjust the lighting and the imaging.
[0020]
FIG. 2 is an explanatory diagram showing an example in which the surface inspection apparatus according to the present invention is used for simultaneously capturing a bright field image and a dark field image. The illumination lamp 2a is arranged so that one of the two illumination lamps 2a becomes a bright field light source, that is, the total reflected light of the light projected by the illumination lamp 2a reaches the line sensor camera 1. Yes. The other illumination lamp 2b is arranged as a dark field light source, that is, the illumination lamp 2b is arranged so that the total reflected light of the light projected by the illumination lamp 2b hardly reaches the line sensor camera 1.
[0021]
4 to 6 are explanatory views showing an example in which the surface inspection apparatus according to the present invention is used for the purpose of recognizing a disk surface defect regardless of the direction of a directional hairline. The illumination lamps 2a and 2b are arranged obliquely from above and in directions in which the horizontal directions are different from each other by about 90 degrees. That is, the illumination lamp 2a illuminates the disk substrate D from a direction 45 degrees to the right with respect to the conveyance direction of the conveyance apparatus, and the illumination lamp 2b illuminates the disk substrate D from a direction 45 degrees to the left.
[0022]
The above arrangement method is intended to obtain an image with less influence of striped shadows due to the hairline by arranging so that the direction of the illumination light is at different angles, Arrangement | positioning of a pair of illumination lamp 2a, 2b should just be suitable for said objective, and is not restricted to said arrangement | positioning.
[0023]
Next, the operation of this embodiment will be described. The disk substrate D sent from the blank punching station is transported at a constant speed by the disk substrate transport device 7, and when reaching the imaging position A, the line sensor camera 1 outputs an image of the disk substrate D to the image processing unit 4. .
[0024]
Since the line sensor built in the line sensor camera 1 is a one-dimensional image sensor, scanning is repeated line by line to form an image on the disk substrate. In the conventional surface defect inspection apparatus, one piece of illumination is used. However, in the inspection apparatus of this embodiment, the illumination lamps 2a and 2b are alternately turned on to scan the line sensor. That is, first, one illumination lamp, for example, the illumination lamp 2a is turned on to illuminate the surface of the disk substrate, one line scan is performed, and the illumination lamp 2a is turned off. Next, the illumination lamp 2b is turned on, the surface of the disk substrate is illuminated, one line scan is performed, and the illumination lamp 2b is turned off. By repeating this procedure, an image over the entire surface of the disk substrate D conveyed at a constant speed is output to the image processing unit, and an image by the illumination lamp 2a and an image by the illumination lamp 2b can be obtained by image processing. it can.
[0025]
In the embodiment shown in FIG. 2, the illumination lamp 2a is arranged to be a bright field light source, and the other illumination lamp 2b is arranged to be a dark field light source. By turning on 2b alternately, an image on the disk surface when the bright-field light source is turned on and an image on the disk surface when the dark-field light source is turned on can be taken with one line camera. Therefore, the presence or absence of a surface defect can be reliably recognized from any of the captured images, even for a surface defect that can be confirmed only by either a bright-field light source or a dark-field light source.
[0026]
Further, in the embodiment shown in FIGS. 3 to 5, the two illumination lamps are regions where both the bright field light source and the dark field light source are used, and the disk is viewed from a direction different from the disk transport direction. The inspection apparatus arranged so as to illuminate is described. According to the above inspection apparatus, when the state of the disk surface is directional, surface defects can be recognized and inspected regardless of the directionality. Hereinafter, a description will be given in connection with an example of performing a surface inspection of a disk that is transported in a state where a directional hair line exists on the disk surface and the direction of the hair line is not constant.
[0027]
Now, assuming that the direction of the hairline of the disk substrate D is conveyed in a direction orthogonal to the direction of the illumination lamp 2a, the light of the illumination lamp 2a is irregularly reflected by the hairline of the disk substrate D and a striped shadow is captured as an image. It is. At this time, even if there is a surface defect such as a scratch on the surface of the disk substrate D, the surface defect cannot be found if it overlaps with the striped shadow. On the other hand, according to the illumination of the illumination lamp 2b, the direction of illumination and the direction of the hairline of the disk substrate D are almost the same, so the influence of irregular reflection is reduced, and a striped shadow that is inconvenient for observation of surface defects occurs. It is difficult to recognize surface defects.
[0028]
The image obtained by scanning the line sensor with the illumination lamps 2a and 2b alternately turned on is subjected to image processing by alternately outputting a line image by illumination of the illumination lamp 2a and a line image by illumination of the illumination lamp 2b. Thus, an image by the illumination lamp 2a and an image by the illumination lamp 2b are obtained. In the above example of the disk, it is possible to determine the presence or absence of surface defects based on the image of the illumination lamp 2b.
[0029]
The control device 3 analyzes the two images obtained as in the above two embodiments, and determines the presence or absence of surface defects based on preset determination conditions. Although continuous image information is obtained in the main scanning direction of the line sensor, surface defect information can be obtained only by skipping one line in the disk substrate transport direction (sub-scanning direction). It is necessary to set judgment conditions.
[0030]
Next, identification of the type of surface defect by the inspection apparatus of the present invention will be described. From the above description of the embodiment, it can be seen that there are types of scratches that can be recognized according to the projection direction of illumination and types of scratches that cannot be clearly recognized. As an example, scars with large irregularities hardly appear in bright-field images but clearly appear in dark-field images. In addition, a dent or the like with relatively little unevenness appears in a bright-field image but is hardly identifiable on a dark-field screen. Furthermore, dirt attached to the disk surface can be clearly recognized in a bright field, but is often difficult to recognize in a dark field image.
[0031]
In the inspection apparatus according to the present invention, a plurality of images obtained by illuminating the disk surface from different directions can be obtained. By comparing the appearance of the surface unevenness defect by these images, the type of the surface unevenness defect is identified. It becomes possible to do .
[0032]
Next, the surface inspection system according to the present invention will be described with reference to FIGS. As shown in FIG. 6, a directionality detection station 20 and an imaging station 21 of the transport device 7 are provided. The directionality detection station 20 includes a directionality detection sensor 22 and detects the directionality of the surface state of the disk D being conveyed. The directionality of the surface state mentioned here means a direction such as a linear unevenness whose direction becomes a problem when imaging is performed by an imaging means, such as a hairline on the disk surface.
[0033]
The imaging station 21 is provided with the line sensor camera 1 as an imaging means above the conveying device, and further provided with an illumination lamp 2a, an illumination lamp 2b-L, and an illumination lamp 2b-R. Here, the illumination lamp 2b-L and the illumination lamp 2b-R are arranged so as to illuminate the disk surface from different directions so that appropriate images can be taken according to the output of the detection sensor 22 of the surface state detection station 20. In response to the output of the detection sensor 22, one of the illumination lamps is selected to be lit. The illumination lamp 2a is provided so as to image surface defects that cannot be recognized by illumination by the illumination lamp 2b-L and the illumination lamp 2b-R, and is selected from the illumination lamp 2b-L and the illumination lamp 2b-R. By alternately lighting the illuminated lamp and the illuminated lamp 2a, an image is captured so that various surface defects existing on the disk surface can be recognized.
[0034]
In the description of the surface inspection system described above, an example has been described in which only one illumination lamp 2a is used as an illumination lamp other than the illumination lamp linked to the directionality detection sensor 22, but a plurality of lamps are arranged. Alternatively, the plurality of images may be obtained by alternately lighting.
[0035]
【The invention's effect】
In the conventional surface inspection apparatus, there is a problem that there is a type of surface defect that cannot be recognized depending on the projection direction on the disk substrate as the object to be measured, and the presence of the surface defect on the disk substrate cannot be confirmed by the direction of the hairline. There's a problem. In the present invention, a plurality of different images are obtained by providing a plurality of illuminations having different projection directions and sequentially turning on the illuminations. As a result of being able to capture an image of a surface defect such as a flaw by illumination of any one of the plurality of images, it is possible to eliminate the occurrence of inspection omission.
[0036]
Further, in the surface inspection apparatus of the present invention, by comparing the information of different images obtained as a result of the inspection, the result of being able to know the type of surface defect, the occurrence location and cause of the surface defect in the manufacturing process This helps to improve the quality of the manufacturing process.
[0037]
On the other hand, in the surface inspection system of the present invention, the directionality of the surface state of the disk substrate is detected by the directionality detection station, and control is performed so that only the illumination device in the imaging station corresponding to the directionality is operated. As a result, it is possible to improve the accuracy of the image and reduce the burden on the control device without capturing an image that clearly indicates that a desired surface defect image cannot be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a surface inspection apparatus according to the present invention.
FIG. 2 is an explanatory view showing an embodiment of the surface inspection apparatus of the present invention.
FIG. 3 is a plan view showing another embodiment of the present invention.
4 is a side view seen from the II direction in FIG. 3; FIG.
5 is a side view as seen from the direction II-II in FIG. 3. FIG.
FIG. 6 is a plan view showing an embodiment of the surface inspection system of the present invention.
FIG. 7 is a side view showing an embodiment of the surface inspection system of the present invention.
FIG. 8 is an explanatory view showing a conventional surface inspection apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Line sensor camera 2a Illumination lamp 2b Illumination lamp 2a-L Illumination lamp 2b-R Illumination lamp 3 Control apparatus 4 Image processing unit 5 Illumination power supply 6 Monitor 7 Conveyance apparatus 11 Imaging apparatus 12 Illumination apparatus 20 Directionality detection station 21 Imaging station 22 Directional sensor D Disk substrate

Claims (1)

The surface of the object to be inspected is illuminated by illumination means, the reflected light from the surface is imaged by the imaging means, and the image output from the imaging means is processed by an image processing device to inspect the irregularities on the surface A light source for dark field that projects from a direction and angle that becomes a dark field, and a light source for bright field that projects from a direction and angle that becomes a bright field as the illumination means , and from different positions Provided with a plurality of light sources for projection, and provided with one line sensor camera as the imaging means, and each time the line sensor camera scans one line during the movement of the object to be inspected , surface inspection apparatus characterized by by switching the light source light source for the bright field alternately obtain images captured by irradiation of a plurality of different light sources in one line sensor camera

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