JP2000021035A - Optical disk or method for inspecting optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect an optical disk or the substrate of the optical disk with good productivity. SOLUTION: An article 2 to be inspected is irradiated with light, and the characteristic of the article 2 to be inspected is inspected with good productivity based on reflected light from the article 2 to be inspected. In this case, for an inspection characteristic, a known optical disk or an optical disk substrate is prepared and set as a reference for inspection. The result of subjecting a signal component included in the reflected light from the article to be inspected to Fourier transform is compared with the result of irradiating the inspection reference with light and subjecting a signal component included in reflected light from the inspection reference to Fourier transform, and then the characteristic of the article 2 to be inspected is evaluated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk or a substrate for an optical disk as an inspection object, irradiating light to the inspection object, and inspecting characteristics of the inspection object based on reflected light from the inspection object. Inspection method.

[0002]

2. Description of the Related Art The characteristics of an optical disk are inspected by using a recording signal generator, an apparatus generally equipped with an optical pickup called a spin stand and a spindle, and a reproduction waveform equivalent circuit.
The jitter is evaluated using a value conversion circuit and a time interval analyzer.

[0003] Atomic force microscopes, scanning tunneling microscopes and the like are used for inspection of minute defects of the optical disk substrate and roughness of the substrate surface.

[0004]

All of these devices are expensive, and the inspection of the characteristics of the optical disk and the inspection of minute defects of the optical disk substrate and the roughness of the substrate surface are performed by different inspection devices. Was causing it.

[0005] Further, when an analysis is performed by using an atomic force microscope, a scanning tunneling microscope, or the like in the inspection of minute defects of the optical disk substrate and the roughness of the substrate surface, it takes time for the analysis, and the surface roughness of the substrate is determined. Accuracy was lacking because it was affected by variations in needle performance and deterioration.

[0006] The present invention does not use expensive equipment,
An object is to obtain a method for inspecting an optical disk or an optical disk substrate with high productivity. In particular, it is an object of the present invention to perform an accurate and short-time inspection of minute defects or substrate surface roughness of an inspection object, and to enable these inspections to be performed by the same inspection apparatus.

[0007]

According to the method for inspecting an optical disk or an optical disk substrate of the present invention, an optical disk or a substrate for an optical disk is used as an inspection object, light is irradiated to the inspection object, and reflected light from the inspection object is reflected. In an inspection method for inspecting the characteristics of an inspection target product based on an inspection method, an optical disk or an optical disk substrate whose inspection characteristics are known is prepared in advance and used as an inspection reference product, and a signal component contained in reflected light from the inspection target product is Fourier transformed. Irradiating the inspection reference product with light and comparing the result of Fourier transform of the signal component contained in the reflected light from the inspection reference product to evaluate the characteristics of the inspection target product. I do.

Thus, according to the present invention, an optical disk and / or an optical disk substrate can be inspected by an inexpensive inspection device. In particular, a minute defect and / or the roughness of the substrate surface can be inspected accurately and in a short time. And the present invention
In the inspection of a write-once and / or rewritable optical disc, it can be preferably used.

[0009]

FIG. 1 is a block diagram showing a schematic configuration of an inspection apparatus according to an embodiment of the present invention. Here, a case is shown in which a superheterodyne method is used as a means of Fourier transform. In the figure, reference numeral 2 denotes an inspection object which is an optical disk or an optical disk substrate, 3 denotes an optical pickup for emitting a reproduction laser beam to the recording surface side of the inspection object, 4 denotes a spindle for rotating the inspection object, and 5 denotes an inspection. An RF reproduction processing unit that performs signal processing on the reproduction laser light reflected from the target product. Reference numeral 6 denotes a Fourier transform unit for performing a Fourier transform of the reproduced signal, and includes a mixer 7, an IF filter 8, a detector 9, a local oscillator 10, and a scan generator 11. Reference numeral 12 denotes a memory for storing Fourier transform results, and 13 denotes a comparator for comparing the Fourier transform results with the contents of the memory.

The reflected laser light is processed by the RF reproduction processing unit 5 and supplied to the Fourier transform unit 6. In the Fourier transform unit 6, the output of the local oscillator 10 is stored in a memory 12
Alternatively, it is output to the comparator 13. Scan generator 1
The oscillation frequency of the local oscillator 10 is controlled by the sawtooth voltage from 1. The oscillation frequency from the local oscillator 10 is input to the mixer 7 and mixed with the reproduction signal. The mixed frequency passes through the IF filter 8 because it matches the selected frequency of the IF filter 8. The mixed signal that has passed through the IF filter 8 is converted by the detector 9 into a DC voltage corresponding to the amplitude. By controlling the output voltage of the scan generator 11, the amplitude of each frequency band can be known from the output voltage value of the detector 9.

The output voltage from the detector 9 and the output voltage 17 from the scan generator when one test object is measured are stored in the memory 12, and the detector voltage when another test object is measured is measured. From 9, the output voltage 15 and the output voltage stored in the memory 12 are compared by the comparator 13, and the difference between them is output to the comparison result output terminal 14.

The procedure of the defect inspection of the inspection object is described below. When a laser beam for reproduction is irradiated on the inspection object having a defect, the reflected laser light level of the defective portion becomes different from that of a normal portion, and the reproduction signal has a certain periodicity due to the rotation of the inspection object. Will be. When the reproduction signal 15 having periodicity is input to the Fourier transform unit 6, the output voltage 16 from the detector 9 in that frequency band increases. On the other hand, when there is no defect, there is no change in the reflected laser beam level and there is no periodicity. Therefore, the output voltage 18 from the detector 9 obtained by inputting the non-periodic reproduced signal 17 to the Fourier transform unit 6 is different from the output voltage 16 of the periodic reproduced signal 15 from the detector 9. Will be different values.

The output of the optical disk or optical disk substrate, which has been checked beforehand for any defect, that is, the detector 9 of the inspection reference product, is stored in the memory 12 in correspondence with the output of the scan generator. The output voltage from the detector of the inspection target product whose degree of defect is unknown is compared with the output voltage in the memory corresponding to the scan generator using a comparator. If the two are equal, the inspection target product has no defect. If there is no difference, it is determined that there is a defect.

The procedure for inspecting the surface roughness of the inspection object is shown below. In the inspection of the surface roughness, as in the defect inspection, when the inspection object is irradiated with the reproduction laser beam, the reflected laser light level fluctuates according to the surface roughness, and the reproduction signal is generated due to the rotation of the inspection object. It will have periodicity. The output voltage 18 from the detector 9 of the inspection reference product whose surface roughness is known is stored in the memory 12 and compared with the output voltage 16 from the detector 9 of the optical disk and / or optical disk substrate to be inspected. By doing so, the surface roughness is inspected.

The procedure of the characteristic inspection when the optical disk is a write-once and / or rewritable optical disk will be described below. For example, in an inspection for manufacturing a write-once and / or rewritable optical disk continuously, an unrecorded reference disk whose jitter when information is recorded becomes a judgment reference limit is used, and this inspection machine is used. The inspection and the output voltage 18 from the detector 9 are stored in the memory 12. Detector 9 for write-once and / or rewritable optical disc to be inspected
The output voltage 16 from the memory 12 is compared with the memory 12
It is judged as pass if it is equal to or less than, and rejected if it is more than.

[0016]

According to the detection method of the present invention, the cost can be reduced without using an expensive apparatus, and a minute defect and surface roughness of an optical disk substrate can be accurately and quickly inspected. .

[Brief description of the drawings]

FIG. 1 shows the configuration of an inspection apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection apparatus 2 Inspection object 3 Optical pickup 4 Spindle 5 RF reproduction processing part 6 Fourier transformation part 7 Mixer 8 IF filter 9 Detector 10 Local oscillator 11 Scan generator 12 Memory 13 Comparison part 14 Comparison result output terminal

Claims (3)

[Claims] In an inspection method, an optical disk or a substrate for an optical disk is set as an inspection target, light is irradiated to the inspection target, and characteristics of the inspection target are inspected based on reflected light from the inspection target. An optical disk or optical disk substrate with known characteristics is prepared in advance and used as an inspection reference product, and the result of Fourier transform of a signal component contained in the reflected light from the inspection target product and the inspection reference product are irradiated with light to obtain an inspection reference product. A method for inspecting an optical disk or an optical disk substrate, comprising: comparing a signal component included in light reflected from an article with a result of Fourier transform to evaluate characteristics of the article to be inspected. 2. The method for inspecting an optical disk or an optical disk substrate according to claim 1, wherein the characteristics to be inspected are defects and / or surface roughness. 3. The method for inspecting an optical disk or an optical disk substrate according to claim 1, wherein the optical disk is a write-once and / or rewritable optical disk.