JPH05342638A - Device and method for checking optical disk - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide an optical disc inspection apparatus and an inspection method therefor, which can obtain accurate information of a defect position with a simple configuration in a groove defect inspection of a continuous groove type optical disc. A disc reproducing device 20 reproduces an optical disc by groove tracking, and a reproduction signal at a defective location exceeding a certain threshold value 23 is detected as a defect. From the detected defects, only a large defect which causes a problem in recording / reproducing of the disc is taken out by the size detecting circuit 30 and the gate circuit 31 and stored in the memory 29. The defect position at this time is
The track position and the angular position are detected by using the rotation signal 22 of the disk reproducing device 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk inspection apparatus and an inspection method for detecting groove defects in a continuous groove type optical disk.

[0002]

2. Description of the Related Art FIG.
FIG. 7 is a diagram showing a configuration of an optical system of a conventional optical disc inspection apparatus shown in Japanese Patent Publication No. FIG. 5 is a diagram showing the positional relationship of groove defects with respect to two laser spots in a conventional optical disc inspection apparatus. Furthermore, FIG.
FIG. 6 is a waveform diagram of two detection signals in a conventional optical disc inspection apparatus.

In FIG. 4, 1 is an optical disk, 2 is a spindle, 3a and 3b are light projecting lenses, 4a and 4b are light receivers, 5 is a half mirror, and 6 is a mirror.

Conventional detection of groove defects has been carried out by the inspection apparatus having the above-mentioned structure. A conventional example will be described with reference to FIGS. 4, 5 and 6. 1 for the optical disk 1 to be inspected rotated by the spindle 2.
A laser beam T from each light source is converted into two beams T1 and T2 by the half mirror 5 and the mirror 6, and the beams are condensed and emitted by the light projecting lenses 3a and 3b. As shown in FIG. 5, the irradiation positions pa and pb are close to each other in the radial direction of the optical disc 1 (direction of arrow r) within a range where they do not interfere with each other, and spots Sa and Sb are formed on the optical disc surface. First-order diffracted light R1 of each spot
Light receivers 4a and 4b for a and R1b are provided, and the respective signals are A and B signals. However, the light receivers 4a and 4b may be arranged so as to receive a plurality of appropriate diffracted light of the first order or higher, but in that case, the light receivers 4a and 4b receive only the diffracted light and It is necessary to set so as not to receive scattered light in directions other than the angle.

Now, the spots Sa and Sb have a diameter that includes a large number of ID pits 1b as shown in FIG. Due to the ID pit 1b, the reflected light of the spots Sa and Sb becomes scattered light and the amount of light received by the light receivers 4a and 4b decreases, and the levels of the A signal and the B signal are respectively as shown in the signal (b) shown in FIG. descend. Now, when there is a groove defect (a) at the position of one spot Sa, the diffracted light corresponding to this is lost, and the A signal level is further reduced at time t ₀ . This is shown by (a) added to (b) of the A signal in FIG. To describe this point in more detail, in the ID portion having no groove defect, the signal level is lowered due to the scattered light due to the ID pit 1b, but the diffracted light due to the groove should still exist.
On the other hand, when there is a groove defect, the diffracted light truly disappears, and that amount further lowers the signal level.

If the above A signal and B signal are compared by a comparator and a difference signal between them is created, the ID pit 1b
Signal (b) is erased and a desired groove defect signal (b) is detected.

[0007] Next, in FIG. 5, the groove defect (b) to the data portion of the unwritten 'when there is, corresponding to the time point t ₁ to the A signal of Fig. 6 to (b)' is detected, the The waveform of the difference signal is obtained as it is. That is, the groove defect is similarly detected in the data portion, and thus the groove defect is detected regardless of the presence or absence of the ID pit 1b.

[0008]

The detection of a groove defect in a conventional optical disk inspection apparatus requires two laser beams and requires a plurality of light receivers, so that the optical system is more complicated than that of an ordinary disk reproducing apparatus. There was a problem that became.

Further, since the defect is detected by irradiating two beam spots which are sufficiently larger than the track pitch, the exact track position of the defect on the optical disk surface and the angular position from the reference position cannot be specified. There was a problem.

Further, Japanese Patent Laid-Open No. 3-73440 discloses that
An apparatus for inspecting a defect on an optical disc by tracking a land portion of the optical disc and processing a reproduction signal thereof has been proposed. According to this device, a defect can be inspected with one set of optical systems and its position can be accurately obtained, but with respect to a defect such as a groove defect, the change in the reproduced signal is small, and thus the inspection can be performed. Is very difficult,
Further, in the continuous servo format in which a part of the groove is a mirror surface for each sector, which is widely adopted at present, there is a problem that it is impossible to distinguish the groove defect from the mirror surface.

The present invention has been made in order to solve such a problem, and it is possible to perform a groove defect inspection with a simple structure without using a special disk reproducing device, and to accurately detect the size of a defect on an optical disk surface. It is an object of the present invention to provide an optical disk inspecting apparatus and an inspecting method therefor capable of obtaining a track position and an angular position.

[0012]

An optical disk inspection apparatus according to a first aspect of the present invention includes the following means. [1] A reproducing means for reproducing an optical disc by groove tracking. [2] Detecting means for detecting a defect in which the change in the reflectance of the reproduced signal exceeds a predetermined threshold value as a defect. [3] Defect storage means for taking out only defects having a set size or more from the defects and storing them in the memory as groove defects. [4] Defect position detecting means for identifying a defect position on the optical disk surface at this time by using a rotation signal of the optical disk by a track position and an angular position.

A method of inspecting an optical disc according to claim 2 is
It includes the following steps. [1] A reproducing step of reproducing the optical disc by groove tracking. [2] A detection step in which a change in the reflectance of the reproduced signal exceeds a predetermined threshold value is detected as a defect. [3] A defect storing step in which only defects having a set size or more are taken out from the defects and stored in a memory as groove defects. [4] A defect position detecting step of specifying a defect position on the optical disk surface at this time by a track position and an angular position by using a rotation signal of the optical disk.

[0014]

In the optical disc inspection apparatus according to the first aspect, the optical disc is reproduced by the groove tracking by the reproducing means. Further, the detection means detects that the change in the reflectance of the reproduction signal exceeds a predetermined threshold value as a defect. Further, among the defects, only defects having a set size or more are taken out by the defect storage means and stored in the memory as groove defects. Then, the defect position detecting means identifies the defect position on the optical disk surface at this time by using the rotation signal of the optical disk as the track position and the angular position.

In the optical disc inspecting method according to the second aspect, in the reproducing step, the optical disc is reproduced by groove tracking. Further, in the detecting step, a change in the reflectance of the reproduced signal exceeding a predetermined threshold is detected as a defect. Further, in the defect storing step, only defects having a set size or more are taken out from the defects and stored in the memory as groove defects. Then, in the defect position detecting step, the defect position on the optical disk surface at this time is specified by the track position and the angular position using the rotation signal of the optical disk.

[0016]

【Example】

Example 1. An inspection method for detecting a groove defect according to the present invention will be described with reference to FIG. The continuous groove type optical disk has spiral grooves from the inner circumference to the outer circumference. This groove is called a groove portion 12, and a portion between the groove portions 12 is called a land portion 11. The data written on the optical disc tracks the land portion 11 and is recorded on the land portion 11 to form the pit 10. Also, for reproduction, data is read by tracking the land portion 11.

Now, during normal land tracking, the reflectance of the reproduced signal when there is the groove defect 13 increases to almost the same level as that of the portion on the optical disc surface where nothing is recorded. However, the change in the waveform is very small as compared with the other non-defect portion, and the groove defect inspection with the minute change in the waveform is not suitable.

Therefore, a defect is detected by groove tracking. Similar to land tracking, the reflectance at the defect location during groove tracking increases to the mirror surface. In this case, since the reflectance of the portion having no defect is low, the change in the waveform is large, and the change in the waveform is used to detect a defect exceeding a certain threshold value as a defect. In this detection method, the reproduction signal is not affected by the pits, so that the inspection can be performed regardless of the presence or absence of the pits.

FIG. 3 is a block diagram showing the configuration of the first embodiment of the present invention. In FIG. 3, 20 is a disc reproducing device capable of reproducing the optical disc by groove tracking, 21 is a reproducing signal obtained from the disc reproducing device 20, 22 is a rotation signal of one pulse per one revolution of the disc,
Reference numeral 23 is a threshold value for detecting a defect, 24 is a defect detection circuit, 25 is a track / angular position detection circuit, 30 is a size detection circuit for detecting the size of a defect, and 31 is a memory for storing defects of a set value or more , A gate circuit for storing in the memory, 26 is defect size information, 27 is defect track position information, 2
Reference numeral 8 is angular position information from the reference position of the defect, and 29 is a memory for storing the defect information.

Next, the operation of the above-mentioned optical disc inspection apparatus will be described. First, in the disc playback device 20,
Play the optical disc with groove tracking. Figure 1
When there is the groove defect 13 shown in FIG. 2, the waveform of the reproduction signal changes like the groove defect waveform 17 shown in FIG.
At this time, the threshold value 15 shown in FIG.
Those exceeding the above are detected as groove defects.

It is judged whether or not the detected defect is larger than the size set by the size detecting circuit 30 shown in FIG. 3, and the gate circuit 31 is operated based on the information, and only the large defect is stored in the memory 29. The defect size 26, the track position 27, and the angular position 28 are stored in the memory. The track position and angular position of the defect are detected by the track / angular position detection circuit 25 using the rotation signal 22.

As described above, the first embodiment of the present invention catches the reflectance change when the groove portion of the optical disk is tracked and detects a defect larger than the size which causes a problem in the tracking servo in the drive. It is the one.

Even if there is a defect in the groove, since it is located at the end of the focused beam diameter, the influence on the reproduction signal such as data is small. However, the tracking servo signal for causing the focused beam to travel along the track is greatly affected, and in some cases, the beam deviates from the track, which is a cause of so-called off-track.

However, the frequency of the tracking servo is not so high in general, and is usually several tens KHz, and there is no problem even if there is a groove defect having a size equal to or smaller than this frequency. Therefore, in order to detect only a defect having a size equal to or larger than a preset size, the size detection circuit 30 and the gate circuit 31 are provided so that the fluctuation of the reflectance due to the mirror surface is not counted.

The defect position is specified by tracing the grooves of all tracks by groove tracking,
The position information of the defect on the optical disk surface is obtained by detecting the track position and the angular position of the defect by using the rotation signal of one pulse for rotation.

[0026]

As described above, according to the present invention, it is possible to provide an optical disc inspection apparatus and an inspection method therefor with a simple structure because the inspection can be performed by a normal disc reproducing apparatus without using a complicated optical system. Play. In addition, it is possible to obtain accurate position information of the defect.

[Brief description of drawings]

FIG. 1 is a diagram for explaining groove tracking and groove defects in Embodiment 1 of the present invention.

FIG. 2 is a waveform diagram showing a groove defect according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing an inspection apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a conventional optical disc inspection apparatus.

FIG. 5 is a diagram showing an operation of a conventional optical disc inspection apparatus.

FIG. 6 is a waveform diagram showing an operation of a conventional optical disc inspection apparatus.

[Explanation of symbols]

 1 Optical Disc 10 Pit 11 Land Part 12 Groove Part 13 Groove Defect 15 Threshold Value 17 Groove Defect Waveform 20 Disk Reproduction Device 21 Reproduction Signal 22 Rotation Signal 23 Threshold Value 24 Defect Detection Circuit 25 Track / Angular Position Detection Circuit 26 Size Information 27 Track Position Information 28 Angular Position Information 29 Memory 30 Size Detection Circuit 31 Gate Circuit

Claims (2)

[Claims] 1. An inspection device for detecting a groove defect of an optical disk, wherein a reproducing means for reproducing the optical disk by groove tracking, and a reproduction signal whose change in reflectance exceeds a predetermined threshold value are regarded as defects. Detecting means for detecting, defect storing means for taking out only defects having a set size or more from the defects and storing them in a memory as a groove defect, and a defect position on the optical disk surface at this time, a rotation signal of the optical disk. And a defect position detecting means for specifying the track position and the angular position by using the optical disc inspection apparatus. 2. An inspection method for detecting a groove defect of an optical disc, wherein a reproduction step of reproducing the optical disc by groove tracking and a change of the reflectance of the reproduction signal exceeding a predetermined threshold are regarded as defects. A detection step of detecting, a defect storage step of extracting only a defect having a size larger than a set size out of the defects and storing it in a memory as a groove defect, and a defect position on the optical disk surface at this time is a rotation signal of the optical disk. And a defect position detecting step of specifying the track position and the angular position by using the optical disc inspection method.