JPH0228815B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flaw inspection device for inspecting flaws on a metal surface such as an aluminum surface of a magnetic disk material.

Various methods have been proposed as methods for inspecting scratches, one of which is a diffused reflection light condensing method. As shown in Fig. 1, the laser beam from the laser oscillator 1 passes through the mirror 2 and the lens 3.
After that, the sample surface 4 is irradiated. When the sample surface 4 is a smooth plane, the laser beam is specularly reflected, passes through the center passage of the mirror 5, and returns to the laser oscillator 1.

When the sample surface 4 has irregularities, diffused reflection occurs, the light is focused by the lens 3, passes through the mirror 5, and enters the phototube 6. When the sample surface 4 is a surface of metal or the like having a cutter mark, the diffusely reflected light is scattered in a direction perpendicular to the cutter mark, as shown in FIG.
This diffusely reflected light intensity distribution is expressed in polar coordinates as shown in the third figure.
It is a diagram.

For example, when the cutter mark is ground, the main direction component θ of the diffusely reflected light is within 1°. As shown in Fig. 4A, when there is an isolated flaw such as an indentation on the sample surface 4, and as shown in Fig. 5B, when the irradiation diameter is larger than the isolated flaw, the directionality as shown in Fig. 5A A less isolated scattered reflected light intensity distribution can be obtained. Fifth
In the figure, B is the intensity distribution of diffusely reflected light from the cutter mark.

Incidentally, since the diffusely reflected light incident on the phototube 6 includes the cutter mark diffusely reflected light and the isolated scattered reflected light, the phototube voltage output is as shown in FIG.

In addition, if there are linear scratches such as scratches on the sample surface 4 as shown in FIGS. 7A and 7B, a linear scattered reflected light intensity distribution A with strong directionality is observed in the direction perpendicular to the scratch as shown in FIG. is obtained. In FIG. 8, B is the intensity distribution of diffusely reflected light from the cutter mark, and C is the direction of the linear scratch. In this case as well, the phototube voltage output is similar to that shown in FIG. However, since the phototube voltage output obtained by these methods is always offset by the intensity of the diffusely reflected light from the cutter mark, the sensitivity for detecting flaws is extremely low. This is because the sensitivity characteristic of the phototube is that when the light is bright, the output is saturated, and the sensitivity has linearity in dark areas.

For example, when using a lens with N.A. of 0.4, aluminum grinding (0.5S) on the sample surface, and a laser irradiation diameter of 50 μm, the detection limit was an isolated flaw with a diameter of 10 μm (depth of 1 μm). Furthermore, it was not possible to distinguish between isolated scratches and linear scratches.

The present invention was devised in view of the above-mentioned conventional drawbacks, and its purpose is to prevent cutter marks from being detected as flaws in ground magnetic disks, and to detect linear flaws and isolated flaws that are defective products. To provide a flaw inspection device for magnetic disk materials that can easily detect flaws in magnetic disk materials without performing complicated image processing.

That is, in order to achieve the above object, the present invention has the following features:
A flaw inspection device for ground magnetic disk material includes a light source, an objective lens for condensing and irradiating light emitted from the light source perpendicularly to the surface of the magnetic disk disk, and a surface of the disk. Among the scattered light reflected from the surface, a light shielding means for shielding the scattered light generated in a direction substantially perpendicular to the longitudinal direction of the cutter marks formed in large numbers with the longitudinal direction facing the circumferential direction by grinding; A magnetic disk characterized in that it is equipped with a photoelectric conversion element that receives scattered light that is not scattered and converts it into a signal, and a detection circuit that detects linear flaws and isolated flaws based on the spread of the signal obtained from the photoelectric conversion element. This is a flaw inspection device for used materials. The present invention also provides a flaw inspection device for a ground magnetic disk material, which includes a light source and an objective lens that condenses and irradiates the light emitted from the light source perpendicularly to the surface of the magnetic disk disk. Among the scattered light reflected from the surface of the disc, the scattered light generated in a direction approximately perpendicular to the longitudinal direction of the cutter marks, which are formed in large numbers by grinding with the longitudinal direction facing the circumferential direction, is missed, and the other A light reflecting means that reflects scattered light; a photoelectric conversion element that receives the scattered light reflected by the light reflecting means and converts it into a signal; and linear flaws and isolation based on the spread of the signal obtained from the photoelectric conversion element. The present invention is a flaw inspection device for magnetic disk materials, characterized by comprising a detection circuit for detecting flaws.

Embodiments of the present invention will be specifically described below with reference to FIGS. 9 to 14. That is, in a flaw inspection device for ground magnetic disk material, the magnetic disk material is inspected by avoiding the influence of diffusely reflected light from the many cutter marks made by grinding the magnetic disk material with the longitudinal direction facing the circumferential direction. An embodiment of the present invention will be described in which linear flaws and isolated flaws existing on a material are discriminated and inspected.

First, the first embodiment of the present invention is shown in FIGS. 9 to 1.
This will be explained based on Figure 1. That is, as shown in FIG. 9, while rotating and scanning the magnetic disk material 4, the laser beam output from the laser oscillator 1 is
It is reflected by the mirror 2, passes through a hole formed in the center of the mirror 5, and is passed through the lens (objective lens) 3 onto the magnetic disk material 4, which has been grinded with many cutter marks with its longitudinal direction facing the circumferential direction. The beam is focused and irradiated almost perpendicularly to the object. The light that is specularly reflected on the surface of the magnetic disk material 4 that has been rotated and scanned passes through the lens 3 and escapes from the hole formed in the center of the mirror 5, and the scattered light that is diffusely reflected on the surface of the magnetic disk material 4 is focused through the lens 3. and is reflected by mirror 5. The light shielding plate 7 blocks the main component of the diffusely reflected light caused by the many cutter marks that are formed on the magnetic disk material 4 by grinding so that the longitudinal direction faces the circumferential direction, and only the diffusely reflected light caused by the scratches enters the phototube 6. . Therefore, since the diffusely reflected light from the cutter mark is blocked, the influence of the diffusely reflected light by the cutter mark can be avoided.Furthermore, the spread of the signal output from the phototube 6 as the magnetic disk material 4 rotates and scans the magnetic disk. Linear flaws and isolated flaws present on the material can be discriminated and inspected.

By the way, instead of the light shielding plate 7 shown in FIG.
As the mirror 5, it is also possible to use a mirror 5a which doubles as a light shielding plate and has a portion painted black as shown in FIG.

As shown in FIG. 11A, a light shielding plate 8 having a light shielding portion may be installed under the lens 3.

FIG. 11B shows an example of the light shielding plate 8. As shown in FIG.

In either case, the main component of the cutter mark diffusely reflected light is blocked, so the offset of the phototube output as shown in Fig. 6 is reduced, and linear flaws and isolated flaws can be detected with high sensitivity, as shown in Fig. 5. As such, linear flaws and isolated flaws have different spreads, and inspection can be performed by distinguishing between linear flaws and isolated flaws based on the spread of the signal output from the phototube 6.

Next, the second embodiment of the present invention is shown in FIGS. 12 to 1.
This will be explained based on Figure 4. That is, as shown in FIG. 13, scratches parallel to the cutter mark are generated due to cutting of the cutter during processing. In this case, as shown in FIG. 12A, a phototube 6a is provided to detect scratches parallel to the cutter mark. At this time, the diffusely reflected light due to the cut mark and scratches parallel to the cut mark reaches the phototube 6a through the pass part of the mirror 5a, an example of which is shown in FIG. 12B. The 14th example of the voltage output of a phototube 6a with scratches parallel to the cutter mark
As shown in the figure. The example shown in FIG. 12 has the advantage that isolated and linear flaws can be distinguished and detected by the phototube 6, and flaws parallel to the cutter mark can be distinguished and detected by the phototube 6a.

An example of an apparatus for inspecting scratches on magnetic disk materials that is not directly related to the present invention will be described below with reference to FIGS. 15 to 22. FIG. 16 is a view taken along the line XX in FIG. 15, in which a plurality of phototubes 61 to 6e are arranged in a ring shape, each facing the sample surface 4. Here, they are arranged in two stages so that there are no gaps in the circumferential direction. The phototubes 61 and 6m are oriented in the direction of the main component of the diffusely reflected light of the cutter mark. The diffusely reflected light from the linear scratches as shown in FIG. 16 is directed toward the phototubes 65 and 6n. The output of each phototube is shown in FIG. Here, linear flaws can be detected with extremely high sensitivity using the outputs of the phototubes 65 and 6n. This is because the non-principal component of the diffusely reflected light from the cutter mark is dispersed and incident on each phototube except for 61 and 6m. In the case of an isolated flaw, since the directionality of diffusely reflected light is small, the outputs of the phototubes other than the phototubes 61 and 6m are about the same as shown in FIG. 18.

In the case of scratches parallel to the cutter mark, phototube 6
Since diffusely reflected light enters only the output of 1.6 m,
The output shown in FIG. 19 is obtained.

Since scratches parallel to the cutter mark and linear scratches have directionality, they produce diffusely reflected light of the same intensity in the direction perpendicular to the scratches, so the outputs of phototubes at opposing positions (for example, 65 and 6n) can be processed by adding them. So,
The circuit can be simplified. FIG. 20 shows a block diagram of a flaw inspection device using this method. Phototube 61
The outputs of 6m and 6m are added by an analog addition circuit 91, quantized by a flaw detection circuit 10 parallel to the cutter mark, and then sent to a display circuit 12. Outputs from other phototubes at opposing positions are added by analog adder circuits 92 to 9s, and quantization processing is performed by an isolated flaw and linear flaw detection circuit 11. In the detection circuit 11, if adjacent detector outputs of a predetermined number or less are significantly larger than other outputs other than 61, 6m, it is considered a linear flaw, and if there is no significant difference, it is called an isolated flaw. distinguish.

In the example shown in FIG. 21, a plurality of optical fibers 13 are installed in a ring shape, and one end of each opposing fiber is fixed on the sensor array 14. A detection signal is obtained by scanning.

It is also possible to join the opposite ends of the fibers as shown in FIG. Although the above embodiment has been described with respect to a sample surface having cutter marks, it is natural that this example can be used as a flaw inspection device for a smooth surface without cutter marks.

As described above, according to the present invention, it is possible to easily detect cutter marks on ground magnetic disk materials without detecting them as scratches, and without performing complicated image processing to detect linear scratches or isolated scratches that are defective products. Since it can be detected quickly, high-speed inspection is possible.

[Brief explanation of drawings]

Figure 1 shows a conventional diffuse reflection condensing flaw inspection device. Figure 2 shows an example of diffusely reflected light from a cutter mark, Figure 3 shows a polar coordinate representation of the intensity distribution of diffusely reflected light from a cutter mark, Figure 4 shows diffusely reflected light from an isolated scratch, and Figure 5 Figure 6 shows the polar coordinate surface of the intensity distribution of the diffusely reflected light from an isolated scratch, Figure 6 shows the phototube voltage output due to an isolated scratch, Figure 7 shows the diffusely reflected light from a linear scratch, and Figure 8 shows the linear scratch. FIG. 9 shows a polar coordinate representation of the intensity distribution of diffusely reflected light from
The figure shows a first embodiment of the present invention using a light-shielding plate, FIG. 10 shows an embodiment in which the mirror shown in FIG. 9 has the function of a light-shielding plate, and FIG. FIG. 12 is a diagram showing an embodiment in which the light-shielding plate shown in the figure is placed between the lens and the magnetic disk material, and FIG. FIG. 13 is a diagram showing a scratch parallel to the cutter mark, and FIG. 14 is a diagram showing the example of the cutter mark shown in FIG. Diagram showing the output voltage waveform to be output, No. 15
Figure 1 shows an example not directly related to the present invention.
Figure 6 is an X-X arrow view in Figure 15, Figure 17 is a diagram showing the voltage waveform output from the phototube shown in Figures 15 and 16 in the case of a linear flaw, and Figure 18 is a diagram in the case of an isolated flaw. Figures 15 and 16 show the voltage waveforms output from the phototubes, and Figure 19 shows the voltage waveforms output from the phototubes shown in Figures 15 and 16 in the case of scratches parallel to the cutter mark. , second
Figure 0 is a block diagram showing a circuit that processes signals output from the phototubes shown in Figures 15 and 16, and Figure 21 is an optical fiber and sensor used in place of the phototubes shown in Figures 15 and 16. FIG. 22 is a diagram showing an example of coupling the opposing optical fibers shown in FIG. 21. 61-6e...Phototube, 91,9s...Analog addition circuit, 10...Flaw detection circuit parallel to the cutter mark, 11...Isolated, linear flaw detection circuit, 12
... Display circuit, 13 ... Optical fiber, 14 ... Sensor array.

Claims (1)

[Scope of Claims] 1. A flaw inspection device for a ground magnetic disk material, comprising: a light source; and an objective for condensing and illuminating the light emitted from the light source perpendicularly to the surface of the magnetic disk disk. A lens and a light shielding means for blocking scattered light generated in a direction substantially perpendicular to the longitudinal direction of the cutter marks, which are formed in large numbers by grinding with the longitudinal direction facing the circumferential direction, among the scattered light reflected from the surface of the disk. , a photoelectric conversion element that receives scattered light that is not blocked by the light blocking means and converts it into a signal, and a detection circuit that detects linear flaws and isolated flaws based on the spread of the signal obtained from the photoelectric conversion element. A flaw inspection device for magnetic disk materials, characterized by: 2. A flaw inspection device for a ground magnetic disk material, comprising: a light source, an objective lens that focuses and irradiates light emitted from the light source perpendicularly to the surface of the magnetic disk disk, and the disk. Among the scattered light reflected from the surface, the scattered light generated in a direction approximately perpendicular to the longitudinal direction of the cutter marks, which are formed in large numbers by grinding with the longitudinal direction facing the circumferential direction, is missed, and the other scattered light is reflected. A light reflecting means, a photoelectric conversion element that receives the scattered light reflected by the light reflecting means and converts it into a signal, and a detection that detects linear flaws and isolated flaws based on the spread of the signal obtained from the photoelectric conversion element. A flaw inspection device for magnetic disk materials, characterized by comprising a circuit. 3. A photoelectric conversion element that receives the scattered light missed by the light reflecting means and converts it into a signal, and a detection circuit that detects scratches parallel to the cutter mark existing on the cutter mark based on the signal obtained from the photoelectric conversion element. An apparatus for inspecting scratches on a magnetic disk material according to claim 2, characterized in that it is equipped with: