JPH03116563A - Stamper inspecting device - Google Patents

Abstract

PURPOSE:To exactly measure the C/N of a stamper by providing a means to detect the noise ratio of the stamper according to the photoelectric converting output of an optical system for which masking is executed to a preformat data part. CONSTITUTION:In a preformat data reproducing part 44, when the address information of a block header corresponding to one block are reproduced according to a binary signal to be supplied from a binary circuit 43, corresponding to the reproducing, a block header detection signal is outputted to a preformat timing control part 42. In the preformat timing control part 42, when the block header detection signal is supplied from the preformat data reproducing part 44, a mask signal corresponding to the block header is prepared and outputted to a C/N detection part 41. In the C/N detection part 41, corresponding to the mask signal to be supplied, a part corresponding to the block header in a reproducing signal to be supplied from an adder circuit 40 is removed. Thus, the C/N of the stamper can be exactly measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a stamper inspection apparatus for inspecting a stamper for producing, for example, a substrate for an optical disk.

(Prior Art) As is well known, information reproduction, such as an optical disk device, records information on an optical disk by irradiating the optical disk with laser light output from a semiconductor laser, and reads recorded information. Various devices have been developed.

The optical discs used in such optical disc devices are
The substrate is now created using a stamper as a mold. That is, by using this stamper, a large number of replica disks (copies) are created. The method for creating optical discs using this stamper includes:
There are ultraviolet curing resin methods and injection molding methods, and tracks (groups) as guide grooves and preformat data such as addresses are formed respectively.

By the way, when creating an optical disc using the stamper as described above, the C/N ratio (Carrier
No.1 Rethio) is affected. Therefore, it is necessary to measure the C/N ratio of the surface of the stamper in advance.

Usually, the C/N ratio of a stamper is measured by the change in reflected light obtained by irradiating the stamper with laser light. Only stampers with a good C/N ratio are used to create optical discs.

However, with this method, the preformat data formed on the stamper is observed as a noise component, making it impossible to accurately measure the C/N ratio.

(Problems to be Solved by the Invention) As described above, in conventional inspection equipment, preformat data is observed as a noise component when measuring the C/N ratio of a stamper, so the C/N The disadvantage was that the ratio could not be measured accurately.

Therefore, an object of the present invention is to provide a stamper inspection device that can accurately measure the C/N ratio of a stamper.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the stamper inspection device of the present invention includes a method of applying light to a stamper having a recording track in which preformat data is recorded. an optical system that detects the light obtained by irradiation and converts it into electricity;
A masking means for masking the preformat data part in the photoelectric conversion output of the optical system, and a noise ratio on the stamper is detected by the photoelectric conversion output of the optical system in which the preformat data part is masked by the masking means. Detection means.

(Function) According to the present invention, the preformat data portion is masked by the above-described means when measuring the C/N ratio, so that the preformat data can be prevented from being treated as a noise component.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 shows a stamper inspection device of the present invention. A convex portion is formed on the surface of the stamper (mold) 1 for forming guiding grooves (tracks, groups) in a spiral or concentric manner on an optical disk (not shown). For example, it is rotated at a constant speed. This motor 2 is controlled by a motor control circuit 18.

As shown in FIG. 3, the stamper 1 is formed of, for example, a glass mask disk plated with nickel, and has a cutout, that is, a reference position mark 11, near its center. .

Further, the stamper 1 is divided into 256 sectors "0 to 255" with the reference position mark 1 being "0".

There are a plurality of blocks of a certain length on the stamper 1, and for example, 300,000 blocks are formed on 36,000 tracks.

The number of sectors in one block in the upper self-stamper 1 is, for example, 40 sectors on the inner side and 20 sectors on the outer side. A block header (preformat data) A consisting of a block number, track number, sector number, etc. as address information is given to the start position of each block. This block header A is formed by changing the height of the convex portion.

Further, if each block in the stamper 1 does not end at the sector switching position, a block gap is provided so that each block always starts at the sector switching position.

Reproduction of information on the stamper 1, that is, measurement of the C/N ratio, is performed by an optical head 3, as shown in FIG. This optical head 3 is fixed to a drive coil 13 that constitutes a movable part of a linear motor, and this drive coil 13 is connected to a linear motor control circuit 17.

A linear motor position detector 26 is connected to this linear motor control circuit 17, and this linear motor position detector 26 is connected to an optical scale 2 provided on the optical head 3.
5, a position signal is output.

Further, a permanent magnet (not shown) is provided in the fixed part of the linear motor, and when the drive coil 13 is excited by the linear motor control circuit 17, the optical head 3 is moved in the radial direction of the stamper 1. It looks like this.

An objective lens 6 is held on the optical helad 3 by a wire or a leaf spring (not shown), and the objective lens 6 is moved in the focusing direction (
The driving coil 4 allows movement in the tracking direction (direction perpendicular to the optical axis of the lens).

Laser light generated by the semiconductor laser 9 driven by the laser control circuit 14 is irradiated onto the stamper 1 via the collimator lens 11a1, the half prism 11b1, and the objective lens 6, and the reflected light from the stamper 1 is , objective lens 6, half prism 11b1
Condensing lens 10a1 and cylindrical lens 10b
is guided to a photodetector 8 via. This photodetector 8 has 4
It is composed of divided photodetection cells 8a, 8b, 8c, and 8d.

Note that the above-mentioned wire-based objective lens driving device is described in Japanese Patent Application No. 61-284591.
The explanation thereof will be omitted here.

The output signal of the photodetection cell 8a of the photodetector 8 is supplied to one end of the adders 30a, 30c via the amplifier 12a, and the output signal of the photodetection cell 8b is supplied to the adders 30b, 30d via the amplifier 12b. is supplied to one end of the photodetection cell 8
The output signal of C is passed through an amplifier 12c to an adder 30b,
The output signal of the photodetecting cell 8d is supplied to the other end of the adders 30a and 30d via an amplifier 12d.

The output signal of the adder 30a is supplied to the inverting input terminal of the differential amplifier OP1, and the output signal of the adder 30b is supplied to the non-inverting input terminal of the differential amplifier OP1. As a result, the differential amplifier op, the adders 30a, 30
A track difference signal is supplied to the tracking control circuit 16 according to the difference in b. This tracking control circuit 16 creates a track drive signal according to the track difference signal supplied from OPl.

A track drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Further, the track difference signal used in the tracking control circuit 16 is supplied to the linear motor control circuit 17.

On the other hand, the output signal of the adder 30c is transmitted to the differential amplifier OP2.
The output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. As a result, the differential amplifier OP2 is connected to the adder 30e.
, 30d, a signal regarding the focus point is supplied to the focusing control circuit 15.

The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5, and is controlled so that the laser beam is always in just focus on the stamper 1.

As described above, the sum signal of the outputs of the respective photodetection cells 8a to 8d of the photodetector 8 in a state where focusing and tracking are performed, that is, the adder 30a.

The output signal from the stamper 30b reflects noise caused by roughness on the surface of the stamper 1.

This signal is supplied to the C/N ratio inspection circuit 19, and this C/N ratio inspection circuit 19
The C/N ratio on the surface of the stamper 1 is measured in the /N ratio testing circuit 19.

The tracking control circuit 16 moves the objective lens 6 in response to a track jump signal supplied from the CPU 23 via the D/A converter 22, thereby moving the light beam by one track. There is.

The laser control circuit 14 and the focusing control circuit 15
, tracking control circuit 16, linear motor control circuit 1
7. The motor control circuit 18, the C/N ratio inspection circuit 19, etc. are controlled by the CPU 23 via the pass line 20, and the CPU 23 is connected to the memory 24.
Predetermined operations are performed by a program stored in the computer.

The D/A converter 22 is used to exchange information between the focusing control circuit 15, the tracking control circuit 16, the linear motor control circuit 17, and the CPU 23, respectively.

Further, PD is a light receiving element for detecting the amount of light from the semiconductor laser 9.

As shown in FIG. 1, the C/N ratio inspection circuit 19 includes an addition circuit 40, a C/N ratio detection section 41, a preformat timing control section 42, a binarization circuit 43, and a preformat data reproduction section 44. It is made up of.

The addition circuit 40 is the adder 30a.

By adding the addition signals from 30b, the result shown in FIG.
A reproduced signal (photoelectric conversion output) as shown in a) is obtained, and this reproduced signal is output to the C/N ratio detection section 41 and the binarization circuit 43.

As shown in FIG. 4, the C/N ratio detection section 41 converts the reproduced signal (a) supplied from the addition circuit 40 into a mask signal (b) supplied from the preformat timing control section 42. Accordingly, a frequency analyzer (not shown) detects the C/N ratio detection signal (C) from which the block header A portion as preformat data has been removed, and performs frequency analysis on this to determine the C/N ratio n1. ).

The preformat timing control section 42 generates a clock for reproduction synchronization and also generates a mask signal corresponding to the block header A as shown in FIG. 4(b). is outputted to the binarization circuit 43, and the mask signal is outputted to the C/N ratio detection section 41. This preformat timing control section 42 creates a clock by dividing an oscillation signal from an oscillator (not shown), and also generates a mask signal when a preformat detection signal is supplied from the preformat data reproducing section 44. It is configured by a logic circuit (not shown) and the like.

The binarization circuit 43 binarizes the reproduction signal supplied from the addition circuit 40 in synchronization with the clock from the preformat timing control section 42,
This binary signal is transferred to the preformat data reproducing section 4.
It is designed to output to 4.

The preformat data reproducing section 44 reproduces the block header A as preformat data using the binarized signal supplied from the binarization circuit 43, and converts the data from serial data to parallel data. . In addition, the preformat data reproducing section 4
4 outputs a block header detection signal to the preformat timing control section 42 in synchronization with the end of the block header when the block header A corresponding to the first block is reproduced.

Next, the operation in such a configuration will be explained.

For example, now, the movement of the optical head 3 is started from the innermost circumference of the stamper 1 toward the outer circumference, and the optical head 3
The reproducing operation is activated to cause the semiconductor laser 9 to generate laser light. Thereby, the laser beam generated from the semiconductor laser 9 is irradiated onto the stamper 1 via the collimator lens 11a1, the half prism 11b1, and the objective lens 6, and the reflected light from the stamper 1 is reflected from the objective lens 6,
The light is guided to the photodetector 8 via the Nof prism 11b, the condensing lens 10a1, and the cylindrical lens 10b. Therefore, the output signal of the photodetection cell 8a of the photodetector 8 is transmitted to the adders 30a, 30c via the amplifier 12a.
The output signal of the photodetection cell 8b is supplied to one end of the adders 30b, 30d via the amplifier 12b, and the output signal of the photodetection cell 8C is supplied to the adders 30b, 30c via the amplifier 12c. The output signal of the photodetection cell 8d is supplied to the other end of the photodetection cell 8d and is sent to the adder 30a via the amplifier 12d.
, 30d.

In this state, the signals from the adders 30a and 30b are supplied to the adder circuit 40 in the C/N ratio test circuit 19. Then, the addition circuit 40 adds the photodetection cells 8a to 8d.
The reproduction signal corresponding to the sum of the detected signals is output to the C/N ratio detection section 4.
1 and output to the binarization circuit 43.

As shown in FIG. 4(a), this reproduced signal shows a signal amount of 1 when no preformat data is recorded, and when data is recorded, the data is shown downward in the figure as 1'. The signal corresponds to the shape. Furthermore, as in the signal S, there are parts in the signal where an amplitude that should not appear due to noise due to roughness or the like appears.

On the other hand, the binarization circuit 43 binarizes the reproduction signal from the addition circuit 40 using the clock supplied from the preformat timing control section 42 and outputs it to the preformat data reproduction section 44. .

In the preformat data reproducing section 44, the binarization circuit 4
The preformat data is reproduced by the binarized signal supplied from 3, and the data is converted from serial data to parallel data. Further, the preformat data reproducing section 44 also receives the 2 bits supplied from the binarization circuit 43.
When the address information of the block header A corresponding to one block is reproduced using the value signal, a block header detection signal is output to the preformat timing control section 42 in response to the reproduction.

Then, in the preformat timing control section 42,
When a block header detection signal is supplied from the preformat data reproducing section 44, a mask signal corresponding to block header A as shown in FIG. 4(b) is created and
/N ratio detection section 41.

As a result, the C/N ratio detection section 41 detects the portion corresponding to the block header A of the reproduced signal supplied from the addition circuit 40 according to the mask signal supplied from the preformat timing control section 42. Remove. As a result, as shown in FIG. 4(c), the signal 1' corresponding to the preformat data is removed from the reproduced signal, and a C/N ratio detection signal containing only the signal S due to noise is generated.

The C/N ratio detection signal thus obtained is outputted to, for example, a frequency analyzer, and is used for accurate C/N ratio measurement.

As described above, the C/N ratio of the stamper can be measured without mistaking the preformat data for noise.

That is, when measuring the C/N ratio of the stamper, the preformat data portion of the reproduced signal is masked. This makes it possible to prevent preformat data from being treated as a noise component.

Therefore, accurate measurement of the C/N ratio is considered to be extremely difficult.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, preformat data is not observed as a noise component, so a stamper inspection apparatus is provided that can accurately measure the C/N ratio of a stamper. can be provided.

[Brief explanation of drawings]

The drawings show one embodiment of this invention, and FIG. 1 shows a C/
A block diagram schematically showing the configuration of the N ratio testing circuit, FIG. 2 is a configuration diagram showing the stamper testing device, FIG. 3 is a diagram showing the configuration of the stamper, and FIG. 4 shows the C/N ratio testing. FIG. 3 is a signal waveform diagram showing an example of each signal waveform in the circuit. DESCRIPTION OF SYMBOLS 1... Stamper, 3... Optical head, 8... Photodetector, 19... C/N ratio inspection circuit, 23... CPU
. 24...Memory, 40...Addition circuit, 41...C
/N ratio detection section, 42... Preformat timing control section, 43... Binarization circuit, 44... Preformat data reproduction section.

Claims (1)

[Scope of Claims] An optical system that detects and photoelectrically converts light obtained by irradiating light onto a stamper having a recording track in which preformat data is recorded; The present invention is characterized by comprising a masking means for masking the format data portion, and a detection means for detecting the noise ratio on the stamper based on the photoelectric conversion output of the optical system in which the preformat data portion is masked by the masking means. stamper inspection equipment.