JPH05273141A - Optical disk inspecting device - Google Patents

Abstract

PURPOSE:To provide an optical disk inspecting device capable of easily detecting a fine defect caused by defective impregnation. CONSTITUTION:A focus-adjusted laser beam is radiated by an optical pickup 20 used at the time of information regeneration to a rotating optical disk 1 to be inspected, the optical pickup 20 is moved by a tracking servo 23, and the laser beam is radiated in sequence over the whole face of the optical disk 1. The reflected light is received by a photo-detector 20b, the maximum value and minimum value of the signal B' corresponding to the reflected light intensity are detected by sample hold circuits 32, 33, and the presence of a defect is reported when the difference voltage V3 between these output voltages V1, V2 becomes the reference voltage Vth or above. A fine defect can be easily detected with a simple structure, and the outflow of a defective product can be completely prevented.

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 device.

[0002]

2. Description of the Related Art Conventionally, an example of a reflection type optical disc shown in FIG. 2 is known. In the figure, reference numeral 1 denotes an optical disk, which is composed of a circular substrate 2, a recording layer 3 formed on the lower surface of the substrate 2, and a reflective layer 4 formed by vapor-depositing gold on the surface of the recording layer 3, for example. As a material for the substrate 2, a translucent member such as glass or polycarbonate is mainly used. Further, in the CD system, the MD system, etc., a concavo-convex portion such as a spiral or concentric guide groove is formed on the surface of the substrate 2, and this serves as a guide for irradiating laser light when recording information. Become.

The recording layer 3 is formed by coating an organic dye such as a cyanine dye on the substrate 2 by a spin coat method. Furthermore, a protective film 5, on the surface of the recording layer 3,
Alternatively, a film having another function may be formed.

After inspecting the optical disc 1 described above, when inspecting it, a dedicated inspection apparatus is used. This inspection apparatus, as shown in FIG.
It includes a mirror 12, a cylindrical lens 13, a photoelectric conversion unit 14, and a defect detection unit 15.

The laser light generator 11 is composed of a YAG laser, a rotating mirror, etc., and scans between the central portion and the outer peripheral portion of the optical disk 1 rotating at a predetermined speed in the radial direction at a predetermined speed. The reflective surface 1a is irradiated with laser light. The incident angle of the laser light on the optical disc 1 at this time is always maintained constant.

The reflected light from the optical disk 1 is reflected by the mirror 12 and passes through the cylindrical lens 13 to the photoelectric conversion unit 1.
It is incident on 4. The mirror 12 has a length equal to or larger than the radius of the optical disk 1, and is arranged so as to be fixed at an angle at which all reflected light to be scanned is incident on the cylindrical lens 13. The cylindrical lens 13 refracts the laser light reflected by the mirror 12 and makes it enter the entrance of the photoelectric conversion unit 14. The photoelectric conversion unit 14 outputs a voltage corresponding to the intensity of incident light to the defect detection unit 15, and the defect detection unit 15 detects a defect on the optical disc 1 based on this voltage value.

According to the above-mentioned structure, the laser light incident on the reflection layer 4 via the substrate 2 and the recording layer 3 of the optical disk 1 is reflected by the reflection layer and then photoelectrically converted via the mirror 12 and the cylindrical lens 13. It is incident on the portion 14. As a result, when the reflection layer 4 of the optical disc 1 has a defect such as a scratch or a small hole, the light intensity of the reflected light from the defect portion decreases, so that the voltage output from the photoelectric conversion unit 14 changes. However, it is possible to detect that the optical disc 1 has a defect by this voltage change. In addition, when the film thickness of the recording layer 3 is changed due to the coating defect of the recording layer 3, the reflected light intensity changes as compared with the position of the normal film thickness, which can also be detected as a defect.

Further, since the entire surface of the optical disc 1 can be inspected only by rotating the optical disc 1 once,
The inspection time can be shortened.

[0009]

However, in the above-mentioned conventional optical disc inspection apparatus, since the YAG laser light having a wavelength of 534 nm is uniformly irradiated in the radial direction of the optical disc 1 for inspection, it is possible to detect. The diameter of such a defect is 30 μm or more.

Therefore, there is a problem that it is impossible to detect a defect due to a so-called imperfect penetration.

That is, when the film pressure of the reflection layer 4 becomes non-uniform due to some reason, when the top coat agent is applied to form the protective film 5, the top coat agent is recorded from the thin portion of the reflection layer 4. When the recording layer 3 is penetrated into the layer 3 and the recording layer 3 is violated, a defective penetration may occur. However, a defect due to the poor penetration has a diameter of about several μm,
Frequently over the entire surface of the optical disc 1. Therefore, the conventional inspection device cannot detect the defect due to the defective penetration.

In view of the above problems, it is an object of the present invention to provide an optical disc inspection apparatus capable of easily detecting a minute defect such as a defective penetration.

[0013]

In order to achieve the above object, the present invention irradiates a laser beam while rotating an optical disc to be inspected at a predetermined rotation speed, and based on the reflected light from the optical disc, In an optical disk inspection device for inspecting the optical disk, a laser light generating means for emitting to the optical disk a laser light having a wavelength substantially the same as that at the time of reproducing information from the optical disk, and the laser light generating means. Focus adjusting means for adjusting the focus of the laser light, light receiving means for receiving the reflected light from the optical disc of the laser light emitted by the laser light generating means, and outputting a signal corresponding to the light intensity,
A maximum value detecting means for detecting a maximum value of the reflected light based on an output signal of the light receiving means, and a minimum value detecting means for detecting a minimum value of the reflected light based on an output signal of the light receiving means, Based on the detection result of the maximum value detection means and the detection result of the minimum value detection means, a notification means for notifying the presence of a defect when the difference between the maximum value and the minimum value becomes a predetermined reference value or more. Optical disk inspection device is proposed.

[0014]

According to the present invention, the laser light emitting means emits a laser light having a wavelength substantially the same as when the information recorded on the optical disk is reproduced, to the optical disk by the focus adjusting means. Focus adjustment of the laser light emitted from the emitting means is performed. As a result, the optical disc is irradiated with a laser beam corresponding to the diameter of a defect which becomes a problem during information recording or information reproduction. Further, the reflected light from the optical disc of the laser light emitted by the laser light emitting means is received by the light receiving means, and a signal corresponding to the light intensity of the laser light received by the light receiving means is output and the maximum The value detecting means detects the maximum value of the reflected light based on the output signal of the light receiving means, and the minimum value detecting means,
The minimum value of the reflected light is detected based on the output signal of the light receiving means. Further, the notification means notifies the presence of a defect when the difference between the maximum value and the minimum value becomes a predetermined reference value or more based on the detection result of the maximum value detection means and the detection result of the minimum value detection means. To be done.

[0015]

1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in the conventional example described above are designated by the same reference numerals, and the description thereof will be omitted. Further, the difference between the conventional example and the present embodiment is that an optical pickup including a semiconductor laser, which is usually used in an optical disk player and the like, and a second defect detection section connected thereto are provided.

That is, 20 is an optical pickup, which is movably arranged on the reflection surface side of the optical disc 1 and is connected to the second defect detection section 30. FIG. 4 is a configuration diagram of an electric system circuit related to the optical pickup 20 and the second defect detection unit 30. As is well known, the optical pickup 20 is composed of a laser diode 20a, a photodetector 20b, a half mirror 20c, a lens 20d and the like. The laser diode 20a emits laser light of a predetermined intensity corresponding to the current input from the laser drive circuit 21, and this laser light is emitted.
The light is applied to the optical disc 1 through the half mirror 20c and the lens 20d. Further, the laser light emitted from the optical pickup 20 is focus-adjusted by the focus servo 22 and is applied to the optical disc 1 as spot light having a diameter of several μm. Further, the optical pickup 20 is moved by the tracking servo 23 in the radial direction of the optical disc 1 at a predetermined speed so that the entire surface of the optical disc 1 can be sequentially irradiated with laser light. As a result, the reflected light from the optical disc 1 is reflected by the lens 2
It is incident on the photodetector 20b via 0d and the half mirror 20c, is converted into an electric signal B having a voltage proportional to the reflected light intensity by the photodetector 20b, and is output.

The second defect detecting section 30 includes the RF amplifier 3
1, a sample hold circuit 32, 33, a subtractor 34, a comparator 35, and a notification circuit 36. The RF amplifier 31 inputs the signal B from the photodetector 20b and inputs it to the sample hold circuits 32 and 33 as a signal B'amplified by the predetermined amplification degree. The sample hold circuit 32 detects and holds the maximum value of the voltage of the signal B ′, and outputs the held voltage V1 to the subtractor 34. Further, the sample hold circuit 33 holds the minimum value of the voltage of the signal B ′ and outputs this voltage V2 to the subtractor 34.

The subtractor 34 outputs a voltage V3 obtained by subtracting the voltage V2 from the voltage V1 to the comparator 35. The comparator 35 compares the input voltage V3 with a preset reference voltage Vth, and outputs an abnormal signal C to the notification circuit 36 when the value of the voltage V3 becomes larger than the reference voltage Vth. When the alarm circuit 36 receives the abnormal signal C from the comparator 35,
It informs that the optical disc 1 has a defect.

According to the present embodiment having the above-described structure, the YAG laser light emitted from the laser light generator 11 is radially moved between the central portion and the outer peripheral portion of the optical disc 1 rotating at a predetermined speed. The reflective surface 1a of the optical disc 1 is irradiated with the light while scanning at a predetermined speed. The reflected light from the optical disc 1 at this time is reflected by the mirror 12 and is incident on the photoelectric conversion unit 14 via the cylindrical lens 13, and a voltage corresponding to the intensity of the light incident by the photoelectric conversion unit 14 is applied to the defect detection unit 15. Is output. Thereby, the defect detection unit 1
5, defects such as scratches and small holes having a diameter of 30 μm or more in the optical disc 1 are detected based on this voltage value.

Further, the laser light emitted from the laser diode 20a of the optical pickup 20 is focused and radiated onto the optical disc 1 as in the case of reproducing information. At this time, the tracking servo 23 is stopped and the optical pickup 20 is fixed at a predetermined position. As a result, the laser light emitted from the optical pickup 20 scans one predetermined track of the optical disc 1. The reflected light from the optical disc 1 at this time is the photodetector 20.
An electric signal B having a voltage proportional to the intensity of reflected light is output from the photodetector 20b. This makes it possible to detect a defect having a diameter of several μm, which is a problem when reproducing information, as the intensity of reflected light, that is, the voltage of the signal B.

When the optical disc 1 does not have the defect due to the defective penetration and the other defect as described above,
The reflected light intensity is almost constant on the entire surface of the optical disc 1. In this case, the voltage of the signal B ′ is held in the sample hold circuits 32 and 33 as the maximum value and the minimum value, and the output voltage V3 of the subtractor 34 becomes almost 0V. Therefore, the voltage V
3 becomes the reference voltage Vth or less and the abnormal signal C from the comparator 35
Is not output.

Further, when there is a defect such as defective penetration, the intensity of the reflected light at the defective part is reduced and the voltage of the output signal B of the photodetector 20b is lowered.
The voltage of the signal B ′ at this time is held in the sample hold circuit 33 as the minimum value. As a result, the output voltage V3 of the subtractor 34 rises due to the difference between the output voltage V1 of the sample and hold circuit 32 and the output voltage V2 of the sample and hold circuit 33, and exceeds the reference voltage Vth. Therefore, the comparator 35 outputs the abnormal signal C, and the notification circuit 36 notifies the existence of the defect. Further, when there is a defect such as a defective penetration, a defect is generated over the entire surface of the optical disc 1, so that the laser beam causes a defect.
Defects can be easily detected by scanning only the tracks. When performing a more detailed inspection, the tracking servo 23 may be operated and the optical pickup 20 may be moved to scan the entire surface of the optical disc 1 with laser light.

As described above, according to this embodiment, it is possible to easily detect a defect having a diameter of several μm. Therefore, it is possible to detect a minute defect which is a problem when recording and reproducing information without missing it. , It is possible to completely prevent the outflow of defective products. Further, since the inspection apparatus of this embodiment can perform inspection in a short time with a very simple structure, it can be easily installed in the existing manufacturing and inspection line of the optical disc 1.

The structure of the inspection apparatus in this embodiment is an example, and the present invention is not limited to this.

[0025]

As described above, according to the present invention, the optical disc to be inspected is irradiated with the laser beam corresponding to the diameter of the defect which becomes a problem at the time of information recording or information reproduction, and the maximum value of the reflected light intensity and Since the defect is detected based on the minimum value, it is possible to easily detect a minute defect such as a defective penetration which cannot be detected conventionally, and it is possible to completely prevent the defective product from flowing out. Further, since the inspection can be performed in a short time with a very simple structure, it has an extremely excellent effect that it can be easily installed in an existing optical disc manufacturing and inspection line.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a configuration example of an optical disc.

FIG. 3 is a configuration diagram showing an example of a conventional optical disc inspection apparatus.

FIG. 4 is a configuration diagram of an electric system circuit relating to an optical pickup and a second defect detection section in an embodiment of the present invention.

[Explanation of symbols]

1 ... Optical disc, 2 ... Substrate, 3 ... Recording layer, 4 ... Reflective layer,
5 ... Protective film, 11 ... Laser light generating part, 12 ... Mirror, 1
3 ... Cylindrical lens, 14 ... Photoelectric conversion part, 15 ... Defect detection part, 20 ... Optical pickup, 20a ... Laser diode, 20b ... Photodetector, 20c ... Half mirror, 20d ... Lens, 21 ... Laser drive circuit, 22 ... Focus servo , 23 ... Tracking servo, 31 ... R
F amplifier, 32, 33 ... Sample and hold circuit, 34 ...
Subtractor, 35 ... Comparator, 36 ... Notification circuit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takashi Ishiguro 6-16-20 Ueno Taito-ku, Tokyo Taiyo Induction Co., Ltd.

Claims (1)

[Claims] 1. An optical disc inspection apparatus for irradiating a laser beam while rotating an optical disc to be inspected at a predetermined rotation speed, and inspecting the optical disc based on reflected light from the optical disc, the information from the optical disc. A laser beam emitting means for emitting a laser beam having a wavelength substantially equal to that during reproduction to the optical disc; a focus adjusting means for adjusting the focus of the laser beam emitted by the laser beam emitting means; Light receiving means for receiving the reflected light of the laser light emitted by the means from the optical disc and outputting a signal corresponding to the light intensity; and detecting the maximum value of the reflected light based on the output signal of the light receiving means. Maximum value detecting means, a minimum value detecting means for detecting the minimum value of the reflected light based on the output signal of the light receiving means, and the maximum value detecting means. Based on the detection result of the large value detection means and the detection result of the minimum value detection means, a notification means for notifying the presence of a defect when the difference between the maximum value and the minimum value becomes equal to or more than a predetermined reference value is provided. An optical disk inspection device characterized by the above.