JPH06309829A - Inspecting device of surface defect of optical disk - Google Patents

Abstract

PURPOSE:To detect a surface defect of the whole signal surface (recording film) of an optical disk and also the one of specular surface parts of the inner and outer peripheries thereof. CONSTITUTION:A switch SW is controlled so that an output signal from a shaping circuit 11 be taken out through a low-pass filter 13 when an irradiated position detecting circuit 12 detects a part in the vicinity of a specular surface (including signal surface parts adjacent to specular surfaces of inner and outer peripheries) of an optical disk and that the output signal from the shaping circuit 11 is taken out directly when the circuit 12 detects positions other than the aforesaid parts. Accordingly, the signal taken out from the low-pass filter 13 is made flat like a signal of other parts, i.e., the signal surface parts of the optical disk. These signals are inputted to a determination signal preparing circuit 14 through the switch SW, a determination signal is prepared therein and it is compared with a video signal obtained through the switch SW, by a determination circuit 15.

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 recording information on an optical disk.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a visual inspection machine for optical disks. As shown in FIG. 3, the light generated by the light source 1 passes through the irradiation optical system 2 and then is irradiated onto the optical disc 3.
The optical disc 3 is rotating during the inspection. The light reflected from the optical disc 3 is received by the CCD 5 by the light receiving optical system 4.

When there is an appearance defect on the optical disk 3, the CCD 5 as shown in the example of the conventional video signal in FIG.
Is generated in response to the range from the outer circumference to the inner circumference of the optical disc 3, and if there is an appearance defect on the optical disc 3, the signal 8 caused by the defect is detected by comparing with the determination signal 7.

This decision signal 7 is made by multiplying the level of the signal responding to the normal surface by a multiplier.

[0005]

However, as described above, in the conventional inspection method, large signals 9 and 10 are generated for the signal surface portion and the mirror surface adjacent to the mirror surfaces of the inner and outer circumferences of the optical disk 3. Therefore, although the level of the signal 6 is unstable or defective, it cannot be accurately inspected.

Therefore, an object of the present invention is to provide a surface defect inspection apparatus for an optical disk which solves the above problems.

[0007]

In order to achieve the above object, the present invention provides means for irradiating the surface of an optical disk with light, light receiving means for receiving reflected light from the surface of the optical disk and performing photoelectric conversion, and the light receiving means. Defect detection means for detecting a surface defect of the optical disc by comparing a signal from the means with a determination signal, position detection means for detecting the irradiation position of the light on the optical disc, and a detection result of the position detection means And a means for supplying a signal from the light receiving means concerning reflected light from a predetermined position of the optical disk to the defect detecting means after passing through a low pass filter.

[0008]

According to the present invention, by determining the signal from the light receiving means in response to the reflected light from the predetermined position of the optical disc through the low pass filter, the inner circumference of the optical disc
Accurate inspection can be performed on the signal surface and the mirror surface adjacent to the mirror surface on the outer periphery.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a detection circuit to which the present invention is applied. This detection circuit inputs a signal from the CCD 5 of the visual inspection machine shown in FIG. The video signal from the CCD 5 is shaped by the shaping circuit 11. An irradiation position detection circuit 12 detects the irradiation position of the light source 1 onto the optical disk based on a signal from the scanning means of the light source 1 in the appearance inspection machine shown in FIG. 3, and switches according to the detected position. Switch SW. That is, when the vicinity of the mirror surface of the optical disk (including the signal surface portions adjacent to the inner and outer mirror surfaces) is detected, the output signal from the shaping circuit 11 is taken out through the low-pass filter 13, and the other positions are detected. In this case, the switch SW is controlled so that the output signal from the shaping circuit 11 is directly taken out. Therefore, the signal taken out from the low-pass filter 13 becomes flat like other portions, that is, the signal surface portion of the optical disc, and these are input to the determination signal generating circuit 14 through the switch SW to generate the determination signal, and the determination circuit 15 Is compared with the video signal obtained through the switch SW. The judgment circuit 15 judges that the video signal has dropped to the level of the judgment signal as a defect and outputs the judgment signal.

Thus, as shown in the example of the video signal in the embodiment of the present invention in FIG. 2, even a video signal in the vicinity of the inner circumference and the outer circumference of the optical disk has a level equivalent to that of the signal surface and the judgment signal is obtained. Since they can be created and compared, it is possible to accurately detect the defects around the inner circumference and the outer circumference.

[0012]

As described above, according to the present invention, it is possible to detect the surface defects of the entire signal surface (recording film) of the optical disk and the inner and outer mirror surface portions.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a video signal in the embodiment.

FIG. 3 is a diagram showing a structure of an appearance inspection machine.

FIG. 4 is a diagram showing an example of a conventional video signal.

[Explanation of reference numerals] 1 light source 2 irradiation optical system 3 optical disk 4 light receiving optical system 5 CCD 11 shaping circuit 12 irradiation position detection circuit 13 low-pass filter 14 determination signal generation circuit 15 determination circuit

Claims (1)

[Claims] 1. A means for irradiating the surface of an optical disk with light, a light receiving means for receiving reflected light from the surface of the optical disk and photoelectrically converting the reflected light, and comparing a signal from the light receiving means with a determination signal. Defect detecting means for detecting a surface defect of the optical disc, position detecting means for detecting an irradiation position of the light on the optical disc, and reflected light from a predetermined position of the optical disc based on a detection result of the position detecting means A device for inspecting a surface defect of an optical disc, comprising: means for supplying a signal from the light receiving means to the defect detecting means after passing through a low pass filter.