JPH08128965A - Surface inspection device - Google Patents

Abstract

PURPOSE: To easily inspect the surface and rotating state of a subject by emitting a band light onto the surface of the rotatable subject at a fixed incident angle, successively measuring the illuminance change of the reflected light to determine a standard characteristic as a function of reflecting angle, and providing an optical line sensor out of the maximum illuminance position. CONSTITUTION: A light source 10 emits a light made into band by a slit onto the inspection line on a disc 2 to be inspected at a prescribed incident angle. The image of the reflected light is taken by an optical line sensor 14 consisting of CCD, and the illuminance is successively measured as a function to reflecting angle. From the result, the standard characteristic of illuminance change of the reflected light is determined as the function of reflecting angle and stored. The sensor 14 is situated in a position having a level lower than 1/2 of the maximum illuminance value in the standard characteristic. The reflected light scanned by the band light is then measured during the rotation of the disc 12, and compared with the standard characteristic to inspect the surface state and rotating state of the disc 12. The processing therefor is performed by an image processing device 16 and a computer 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection method for inspecting the surface condition of a magnetic disk or optical disk.

[0002]

2. Description of the Related Art Conventionally, as a method of inspecting the state of the surface of a magnetic disk for a computer, a so-called magic mirror as disclosed in Japanese Patent Publication No. 63-19001 is used. A method utilizing the principle is known. This method irradiates the surface of the object to be inspected with light, collects the reflected light of this light with a light receiving lens, projects the image on the light receiving surface, and detects the unevenness of the surface of the object to be inspected as a light and dark image. It is a thing.

However, in this method, since the depression on the surface of the object to be inspected is considered to be equivalent to a concave mirror, there is a problem that if the focal lengths are regarded as concave mirrors, the detection sensitivity decreases. .

Another surface inspection method is disclosed in Japanese Patent Laid-Open No. 62-2.
As disclosed in Japanese Patent No. 35511, there is a method of irradiating the surface of an object to be inspected with laser light and detecting and analyzing the reflected light. However, this method
There is a problem that it takes a long time to scan the entire area of the disk surface, which is the object to be inspected, with the beam.

Further, since the disc to be inspected is used by rotating it, not only are there no scratches or dents on the surface, but there are problems such as rotational blurring of the entire disc surface. The surface inspection method cannot detect the rotational shake of the disk, and thus has had to adopt a completely different detection method.

An object of the present invention is to provide a surface inspection method capable of easily detecting the state of the surface of an object to be inspected such as a disk medium in a short time and simultaneously detecting the rotational shake of the disk. is there.

[0007]

The surface inspection method of the present invention comprises:
Irradiate a strip-shaped light at a predetermined incident angle on a predetermined inspection line on the main surface of the rotatable disc-shaped object to be inspected, and sequentially measure the brightness of the reflected light from the inspection line as a function of the reflection angle, From this measurement result, the reference characteristic of the luminance change of the reflected light is obtained as a function of the reflection angle, and in the reference characteristic of the luminance change of the reflected light beam, the optical line sensor is arranged at a position deviated from the maximum luminance position by a predetermined angle. The surface state and the rotation state of the object to be inspected, which is scanned by the band-shaped light while the disk-shaped object to be inspected is rotating, are inspected.

In particular, by arranging the optical line sensor at a position within the semi-bright field region in the reference characteristic of the brightness change of the reflected light beam, the surface condition and rotational blur can be effectively detected. $ Also, the optical line sensor is set to the maximum luminance value of 2 in the reference characteristic of the luminance change of the reflected light beam.
It is characterized in that it is arranged at a position where the level is one-half or less.

[0009]

FIG. 2 is a block diagram showing the configuration of an embodiment according to the present invention. Further, FIG. 3 is a perspective view schematically showing a main part of the configuration of the apparatus of FIG. The light source 10 irradiates the surface of the disk 12, which is the object to be inspected, with the light shaped into a band by the slit. Light is irradiated on a straight line (hereinafter referred to as an inspection line) between the outer circumference and the inner circumference of the disk 12, and the reflected light from this inspection line is imaged by a line sensor 14 which is a CCD imaging device. This line sensor is a device in which a plurality of CCD image pickup cells are arranged in a line, and for example, 5000 CCD cells are arranged in a line. Therefore, by operating the line sensor 14 for one clock, the inspection lines on the disk 12 are simultaneously imaged, and image samples of 5000 pixels are obtained. With such a configuration, an image of the entire inspection area on the surface can be captured by simply rotating the disk 12 once, so that the inspection time can be significantly shortened.

In FIG. 2, the image sample obtained by the line sensor 14 is sent to the image processor 16.
Digital / analog conversion is performed, image processing well known to those skilled in the art is performed to detect a defective portion, the defective portion is stored in a memory, and a predetermined analysis is performed by the computer 18.

FIG. 4 is a graph showing the relationship between the brightness of the light reflected from the surface of the object to be inspected and the reflection angle. Since the surface of the object to be inspected is a substantially mirror surface state, most of the light rays irradiated at the incident angle θi are reflected at the reflection angle θr = θi, but due to irregular reflection due to slight irregularities on the surface,
The brightness of the reflected light has a curve distribution as shown in FIG. In the present specification, the range from the reflection angle θr of the maximum brightness value Imax to the level (Imax / 2) of the maximum brightness value is called a bright field area, and the bright field area is half the maximum brightness value. The brightness range from the level to one-tenth of the maximum brightness value (Imax / 10) is called a semi-bright field area, and is one-tenth of the maximum brightness value.
An area having a luminance lower than the level of is called a dark field area. However, the division of the visual field area is convenient, and the division may be performed on the basis of another luminance level.

The invention is characterized in that the line sensor is arranged in the semi-bright field region in the characteristic curve. This area is characterized in that the rate of change (gradient) in luminance is relatively large and the change in luminance level is easy to detect, so the state of the surface to be inspected is most prominently reflected, and defects are easy to detect. . Further, when the disc to be inspected rotates, if the rotation blur occurs, the reflection angle of the reflected light also changes, so that the change in luminance at that time can also be efficiently detected. The luminance change due to the unevenness of the surface of the disk 12 and the luminance change due to the rotational blur of the disk 12 can be easily discriminated because the rate of change of the luminance with respect to time is different. That is, since the frequency of the luminance change based on the unevenness of the surface is high, it can be easily detected by the high-pass filter, and on the other hand, the frequency of the luminance change based on the rotational shake of the disc is low, so the low-pass filter can easily Can be detected. In the embodiment of the present invention, the maximum brightness value Ima is based on various experiments.
A line is placed at the position of the reflection angle where the level is 1/5 of x.
The sensor 14 is arranged. However, the position is not limited to this position, and the line sensor 14 may be arranged at any level position as long as it is at a level equal to or lower than ½ of the maximum brightness value. This state is shown in FIG. 2, and the direction in which the light from the light source 10 is most strongly reflected is indicated by the solid arrow, and the reflected light to the position where the light intensity is one fifth of the maximum brightness level in the semi-bright field region. Is indicated by a dashed arrow. Although not shown in FIG. 2, the line sensor 14 is provided with an adjusting mechanism capable of arbitrarily adjusting the relative position (the position based on the reflection angle) with respect to the inspection line on the disk surface irradiated with light. ing. This adjustment is preferably performed automatically under the control of the computer 18, but can also be performed manually sequentially.

FIG. 5 is a block diagram showing the configuration of an embodiment of the image processing apparatus 16 shown in FIG. Line sensor 14
The image sample captured by the amplifier is amplified to a desired level by the amplifier 40, and the analog-digital converter 42 is used.
Is converted into digital data by. Next, the filter processing is performed by the filter processing circuit 44. At this time, each processing of the high pass filter or the low pass filter is executed according to the detection target. This processed data is compared with an appropriate threshold value to be binarized data, and defect data representing a defect on the surface to be inspected is detected. These defect data are represented by continuous data for each imaging line, but since defects on the disk surface are usually related to each other between adjacent inspection lines, an adjacent data group representing a defective portion is set. The operation of extracting and assigning the reference number of the defective portion to each adjacent data group is called labeling processing. After performing this processing in block 48, the processed data is stored in the memory 50.
To memorize. The data in the memory 50 is analyzed by the computer 18.

As described above, the defect data based on the unevenness of the disk surface is scattered in the data stored in the memory 50 as a group of adjacent data. The defect is detected as a change having a cycle of the address range for one rotation of the disk. As described above, since the reference characteristic as shown in FIG. 4 is detected in advance and stored in the memory of the computer 18, the reference characteristic and the defect data are compared and analyzed to disc The degree of defects on the surface of the disk and the degree of rotational blur of the disk 12 can be inspected. It should be noted that each defective portion on the surface can be evaluated individually, but the effect of rotational blur is significantly reflected in the vicinity of the outer circumference of the disc in the change in luminance caused by the rotational shake of the disc. The rotation blur of the disk can be evaluated by performing processing such as averaging a plurality of data corresponding to the vicinity for each inspection line.

Further, in FIG. 2, the line sensor 14
Is provided with a so-called squeezing mechanism used in a normal camera or the like. The squeezing mechanism is the CCD of the line sensor
The amount of light incident on the cell is adjusted, and when the amount of light is reduced by narrowing the squeezing mechanism, so-called focus shift is less likely to occur. This is particularly effective when it is difficult to finely adjust the position of the line sensor 14. As a result, the position of the line sensor 14 can be easily adjusted. Therefore, adjustment of this squeezing mechanism is
An effect equivalent to finely adjusting the relative position of the sensor 14 with respect to the inspection line on the surface of the disk 12 will be obtained.

The above inspection procedure is shown in the flow chart of FIG. In block 1, a predetermined inspection line on the surface of the disk 12 is irradiated with band-shaped light at a predetermined incident angle. Next block 2
Then, the brightness of the reflected light from the inspection line is sequentially measured as a function of the reflection angle. Then, in block 3, the reference characteristic of the luminance change of the reflected light is obtained from the measurement result of block 2 as a function of the reflection angle and stored. In the next block 4, the line sensor is arranged at a position deviated from the maximum brightness position by a predetermined angle in the reference characteristic of the brightness change of the reflected light beam. In the last block 5, the reflected light from the disk surface scanned by the band-shaped light during the rotation of the disk 12 is measured, and the measurement result is compared with the reference characteristic to determine the surface state and the rotating state of the disk 12. inspect.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments described herein, and various modifications and changes can be made as necessary without departing from the gist of the present invention. It will be apparent to those skilled in the art that changes can be made.

[0018]

According to the present invention, the line sensor is arranged in the semi-bright field region, and the reflected light from the surface of the object to be inspected is detected and compared with the reference reflection characteristic measured in advance. By analyzing, not only the condition of the surface to be inspected but also the degree of rotational blur of the object to be inspected can be inspected at the same time. Further, since the method of irradiating band-shaped light and detecting with a line sensor, the inspection can be completed in a very short time by rotating the disc to be inspected once.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure of a surface inspection method of the present invention.

FIG. 2 is a block diagram showing a configuration of an embodiment of a surface inspection apparatus suitable for using the surface inspection method of the present invention.

FIG. 3 is a simplified perspective view of a main part of the apparatus shown in FIG.

FIG. 4 is a graph showing characteristics as a reference of the brightness and the reflection angle of the reflected light from the surface of the inspection object.

5 is a block diagram showing a configuration of an embodiment of the image processing device 16 of FIG.

[Explanation of symbols]

 10 light source 12 object to be inspected (disk) 14 line sensor (CCD imaging device) 16 image processing device 18 computer

Claims (4)

[Claims] 1. A predetermined inspection line on a main surface of a rotatable disc-shaped object to be inspected is irradiated with band-shaped light at a predetermined incident angle, and the brightness of the reflected light from the inspection line is a function of the reflection angle. As a function of the reflection angle, the reference characteristic of the luminance change of the reflected light is obtained from the measurement result, and in the reference characteristic of the luminance change of the reflected light beam, the optical line is located at a position deviated from the maximum luminance position by a predetermined angle. A surface inspection method, in which a sensor is arranged and the surface state and rotation state of the inspection target object scanned by the belt-shaped light while the disk inspection target object is rotating are inspected. 2. The surface inspection method according to claim 1, wherein the optical line sensor is arranged at a position within a semi-bright field region in the reference characteristic of the luminance change of the reflected light beam. 3. The optical line sensor is provided with a half of the maximum brightness value in the reference characteristic of the brightness change of the reflected light beam.
The surface inspection method according to claim 1, wherein the surface inspection method is arranged at a position having the following level. 4. The surface inspection method according to claim 1, wherein the amount of light incident on the optical line sensor is adjusted by a squeezing mechanism.