JPS5992453A - Disk inspecting device - Google Patents

Abstract

PURPOSE:To ensure an inspection of a disk by setting a sensor so as to detect just either one of diffracted beams of the primary or higher orders generated from a signal track and detecting only the signal corresponding to a defect on the disk recording surface. CONSTITUTION:When the laser light is projected to a disk 1, the diffracted light is emitted due to a defect and a track on the disk surface. If the recording surface has no defect, the laser light 11 projected to the disk 1 produces diffracted beams 13 and 14 at the prescribed angle positions by the track on the disk recording surface in addition to the positive reflected light 12. While no diffraction phenomenon is produced due to the track if the track has a partial crack owing to the defect of the recording surface. In other words, the beams 13 and 14 are modulated in response to the crack state of the track and generate the diffracted light 15. Thus the change of a diffraction phenomenon can be detected by setting a sensor 9 on the optical axis of the beam 13. Furthermore, it is possible to provide a sensor corresponding to the diffracted beam of higher order.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a disc inspection device for inspecting defects on the recording surface of a video disc, audio disc, or the like.

Conventional structure and its problems In general, scratches and scratches occur on the disk surface during the disk manufacturing process.
Defects occur due to unevenness, adhesion of foreign matter, etc., resulting in poor quality of the disk, and the above-mentioned defects must be inspected during the manufacturing process. Therefore, attempts have been made to inspect the disk recording surface for defects at high speed by scanning the disk recording surface with Raded light and detecting signals corresponding to defects with a sensor.

In this case, the above-described defect detection method has conventionally involved projecting radar light perpendicularly onto the disk 21 as shown in FIG.
One method is to collect the scattered light with a condenser lens 22 and detect it with a sensor 23, and the other is to project a laser beam onto the disk 21 at a predetermined angle and collect the specularly reflected light, as shown in FIG. A method of condensing light with an optical lens 24 and detecting it with a sensor 26 is adopted. However, in the case of any of the above-mentioned defect detection methods, in discs such as compact discs that have a protective layer on the recording surface, the light reflected from the surface of the protective layer and the light reflected from the recording surface are mixed, and it is difficult to detect defects. There was a problem that signals could not be detected reliably.Objective of the Invention An object of the present invention is to provide a disk inspection device that can perform more reliable inspection by detecting only signals corresponding to defects on the disk recording surface. 0 Structure of the Invention The disk inspection device of the present invention includes a sensor arranged in correspondence with the diffracted light so as to detect only one of the first-order or higher-order diffracted light generated by the signal track provided on the disk. This sensor is configured to detect defects on the disk recording surface by detecting only first-order or higher-order diffracted light.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment of the present invention. In FIG. 3, 1 is a disk to be inspected, 2 is a rotational drive section of the disk 1, and 3 is a disk 1 including the rotation drive section 2. feeding mechanism section,
Reference numeral 4 designates a drive unit of the feed mechanism section 3, 6 a laser light source, 6 a projection lens, 7 a half mirror, 18 a mirror, and 9 a sensor for primary diffracted light.

In such a configuration, the feed mechanism section 3 and its drive section 4
The disk 1 is rotated and fed by the rotation drive unit 2, and the laser light from the laser light source 5 is projected onto the surface to be inspected of the disk 1 through the projection lens 6, half mirror 7, and mirror 8. Scan in a spiral. The laser beam projected onto the disk 1 is diffracted by defects and tracks on the disk surface and detected by the sensor 9.

Here, when a laser beam is projected onto the disk 1, diffracted light is emitted due to defects and tracks on the disk surface as shown in FIG. In FIG. 4, 11 is an input laser beam, 12 is a specularly reflected light, 13 is a first-order diffracted light of the track, 14 is a second-order diffracted light of the track, and 16 is a diffracted light due to a defect. If there are no defects on the recording surface, the laser beam 11 projected onto the disk 1 is specularly reflected light 2 by the tracks on the disk recording surface.
In addition, diffracted lights 3 and 4 are generated at predetermined angular positions.

On the other hand, if a portion of the track is missing due to a defect in the recording surface, the aforementioned diffraction phenomenon due to the track will no longer occur. That is, the diffracted light beams 3.4 are modulated depending on the extent of track defects to generate the diffracted light beams 6. Therefore, by arranging the sensor 9 on the optical axis of the -order diffracted light 13, the sensor 9 can detect the change in the above-mentioned diffraction phenomenon, and defects can be reliably detected.

In the above embodiment, the sensor 9 is arranged to correspond to the first-order diffracted light 13, but it goes without saying that the sensor may be arranged to correspond to higher-order diffracted light.

Effects of the Invention As detailed above, according to the present invention, the sensor is arranged so as to respond to any of the first-order or higher-order diffracted light generated by the signal track provided on the disk. This method has the advantage of not only being able to reliably detect defects occurring on the surface, but also eliminating the need for a condenser lens and simplifying the apparatus.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional defect detection method using side scattering light reception, Fig. 2 is a schematic diagram of a conventional defect detection method using specular reflection light reception, and Fig. 3 is a block diagram showing an embodiment of the present invention. ,
FIG. 4 is an explanatory diagram of the operation of the main part. 11...Input laser beam, 12...Specular reflected light, 13...--order diffracted light, 14...
Second-order diffracted light, 15...Diffracted light due to defects, 9.
...Sensor, 1...Disk to be inspected. Name of agent: Patent attorney Toshio Nakao and one other aI
figure? ! Figure 2z/Figure 4

Claims (1)

[Claims] The sensor includes a sensor that scans the recording surface of the disk on which a signal is recorded with a laser beam and detects a signal corresponding to a defect on the recording surface of the disk, and the sensor is generated by a signal track provided on the disk. A disk inspection device arranged in correspondence with the above-mentioned diffracted light so as to detect only one of the first-order or higher-order diffracted lights.