JPH0318883Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical disk inspection device for inspecting the quality of an optical disk by detecting the amount of waviness of the optical disk and the deviation of pit rows formed on the disk surface. .

[Technical background of the invention]

Generally speaking, there are two types of optical discs: read-only discs and recording discs. DAD (Digital Audio Disc), VD (Video Disc), etc. are known as playback-only disks, and pit rows as recorded information are formed in a spiral shape on the surface of these disks at a constant track pitch.

There are two types of recording disks: toss file disks, still image file disks, etc. Unlike playback-only disks, recording disks do not initially have pit rows formed (before recording), but pit rows are formed during recording. A guide groove for moving the robot is formed in a spiral shape with a constant track pitch.

By the way, when manufacturing these optical disks, quality inspection is performed to determine whether the product is within an acceptable range by measuring the amount of waviness of the optical disk and the deviation of pit rows or guide grooves.

A conventional method for measuring the amount of waviness of an optical disk has been to trace the surface of the disk with a contact type sliver and measure the amount of waviness. In addition, as for deviations in pit rows and guide grooves, for example, a microscope and an ITV were combined to enlarge the pit rows or guide grooves on the screen, rotate the disk, and measure the left and right deviations due to rotation.

[Problems with background technology]

However, with this method, measurement errors may occur due to the shape of the tip of the stylus, for example when measuring the amount of waviness on the disk surface.Also, a certain amount of load is applied to the stylus to ensure that it is always in contact with the disk surface. The disadvantage is that the product may be damaged due to the need for contact.

Furthermore, regarding the deviation of pit rows and guide grooves, the movement of the pit rows or guide grooves is tracked visually, which is time consuming and tends to be inaccurate.
Another drawback is that only the outermost or innermost portions of the disk can be inspected.

[Purpose of invention]

The present invention was made to solve the above-mentioned drawbacks, and provides an optical disk inspection device that can accurately inspect the amount of waviness and pitch row of an optical disk in a short period of time without damaging the product. The purpose is to provide.

[Summary of the idea]

In order to achieve the above object, the present invention uses an optical head equipped with autofocus and autotracking mechanisms, detects electrical signals from the drive parts of these mechanisms, and converts the electrical signals into characteristics of the drive parts. The present invention is characterized in that the output compensated by a compensator having characteristics opposite to the above is used as the measurement value of the amount of waviness of the optical disk and the deviation of the pit row.

[Example of idea]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Figures 1 to 5 all illustrate one embodiment of the present invention, with Figure 1 showing a schematic configuration diagram of an inspection device, and Figure 2 showing an optical head used in the same embodiment. FIG. 2 is a diagram showing a schematic configuration diagram. Further, FIGS. 4 and 5 are circuit diagrams showing circuit examples of the compensating section.

In FIG. 1, the reference numeral 1 is an optical head with an autofocus and autotracking mechanism, and the reference numeral 2 is an optical head that detects the amount of deviation in the focusing direction and the tracking direction from the signal obtained by the optical head 1. , a control section that operates each drive section of the optical head 1. Further, reference numeral 3 indicates a compensation section, and reference numeral 4 indicates a moving table for moving the optical head 1 in the radial direction parallel to the disk surface of the optical disk 5. Incidentally, during inspection, the optical disk 5 is rotated at a constant speed by a rotation mechanism (not shown).

The optical head 1 has a structure as shown in FIG. Reference numeral 11 in the figure indicates a semiconductor laser as a light source, and laser light emitted from the semiconductor laser 11 is incident on a collimating lens 12. The laser light incident on the collimating lens 12 is converted into a parallel light beam, passes through the polarizing prism 13, and is guided to the next 1/4 wavelength plate 14. 1/4 wavelength plate 1
After the laser beam incident on 4 is converted into circularly polarized light,
The light enters the objective lens 15 and is focused onto the surface of the optical disk 5. Then, the laser beam focused on the optical disk 5 is reflected by the reflective film (recording film) of the optical disk 5, travels backward along the same optical path, and enters the polarizing prism 13. Here, the laser light (reflected light) from the optical disk that enters the polarizing prism 13 is polarized by the 1/4 wavelength plate 14 in front of it, so that it is reflected and guided to the split light receiving sensor 16. Since the reflected light incident on the split light receiving sensor 16 changes due to the amount of bending due to the rotation of the optical disk 5 and the misalignment of the pit row or guide groove, the output of the split light receiving sensor 16 is controlled by the control unit 2. Then, signal processing is performed, and the amount of deviation in the focus direction and tracking direction is detected.

When a focusing error and a tracking error are detected, the control unit 2 sends a control signal to a focus drive unit 17 and a tracking drive unit 18, and the drive units 17 and 18 move the objective as shown by arrows A and B. Move the lens 15 to a predetermined position.

Therefore, in this embodiment, the amount of waviness of the optical disk 5 and the deviation of the pit row or guide groove are measured by determining the amount of displacement of the objective lens 15 from the signals detected by the drive units 17 and 18. There is.
However, since the signals detected by the focus drive section 17 and the tracking drive section 18 are not flat with respect to the frequency characteristics of each drive section, it is not possible to obtain the actual amount of displacement with the values as they are.

Therefore, in this embodiment, the signals detected by the focus drive section 17 and the tracking drive section 18 are compensated by the compensator 3 so that the frequency characteristics of the entire measurement system become flat. For example, if the frequency-amplitude characteristics of the driving sections 17 and 18 are monotonically increasing, the compensating section 3 includes an operational amplifier OP1, a resistor R1, and a resistor R1 as shown in FIG.
A low-pass filter circuit consisting of R2 and capacitors C1 and C2 may be used.

Further, the signals detected by the drive units 17 and 18 have a characteristic influence on the linearity with respect to the amount of displacement. For example, if the characteristics of the relationship between the signals detected by the drive parts 17 and 18 and the amount of displacement are different in slope depending on the direction, as shown in FIG. A circuit can be used.

As shown in the figure, the signals detected from the focus drive section 17 and the tracking drive section 18 are sent to the operational amplifier via resistors R3, R4, and R5, respectively.
Input to OP3, OP4, OP5. operational amplifier
The signals from the drive unit inputted to OP3 and OP4 are respectively amplified into signals of a predetermined voltage and then applied to switch terminals S1 and S2 of the analog switch AS.
On the other hand, the signal from the drive unit input to the operational amplifier OP5 is high when this signal is on the positive side.
If it is on the negative side, it becomes an L level signal and is applied to the gate end of analog switch AS. Therefore, analog switch AS
Then, the switch terminals S1 and S2 are opened and closed based on the signal level from the operational amplifier OP5 applied to the gate terminal. That is, analog switch AS
operates when the gate signal from the operational amplifier OP5 is at H level, and when the signal detected by the drive section is on the positive side, the switch terminal S1 is closed and the signal from the operational amplifier OP3 is input to the negative input of the operational amplifier OP6. supply to. If the signal from the drive section is on the negative side, the switch end S2 is closed and the signal from the operational amplifier OP4 is supplied to the positive input of the operational amplifier OP6. In the operational amplifier OP6, the signal supplied to the minus input is amplified, and the signal supplied to the plus input is inverted and amplified and output. Therefore,
The operational amplifier OP6 outputs signals with different amplification factors when the signal is on the plus side and on the minus side from the drive section. As a result, operational amplifiers OP3 and OP4
By adjusting the amplification factor using variable resistors R9 and R10, the characteristic of the amount of displacement of the driving section - the signal value detected by the driving section can be made into a characteristic straight line with a constant slope.

As described above, in this embodiment, the optical head 1 equipped with an autofocus and autotracking mechanism is used to detect electrical signals from the drive parts 17 and 18 of the autofocus and autotracking mechanism, and Since the amount of displacement of the objective lens 15 is used as a measurement value of the amount of waviness of the optical disk 5 and the deviation of the pit row or guide groove based on the electric signal, quality inspection can be performed accurately in a short time without damaging the disk surface. I can do it. Furthermore, according to this embodiment, the amount of waviness of the optical disk 5 and the deviation of pit rows, etc. can be measured at the same time, thereby simplifying the inspection process.

In the above embodiment, the optical head 1 of a type in which the objective lens 15 is moved is used as an autofocus mechanism, but it is of course also applicable to a type of optical head 1 in which a rotating mirror is rotated to correct tracking errors.

[Effect of idea]

As described above, according to the present invention, there is provided an optical head having an autofocus and autotracking mechanism, and a compensation section having characteristics opposite to those of the drive section of the autofocus and autotracking mechanism. With this structure, it is possible to provide an optical disk inspection device that can accurately inspect quality in a short time without damaging the product.

[Brief explanation of drawings]

1 to 5 are diagrams showing one implementation and example of the present invention, in which FIG. 1 is a schematic diagram of the inspection device, FIG. 2 is a schematic diagram of the optical head, and FIG. 3 is a drive diagram. A diagram showing an example of the displacement amount-signal value characteristic of the part,
FIGS. 4 and 5 are circuit diagrams showing circuit examples of the compensating section. DESCRIPTION OF SYMBOLS 1...Optical head, 2...Control unit, 3...Compensation unit, 4...Movement table, 5...Optical disk, 1
7... Focus drive section, 18... Tracking drive section.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An optical head having an autofocusing and autotracking mechanism, and a compensating section having characteristics opposite to those of the driving section of these autofocusing and autotracking mechanisms. and detecting an electrical signal obtained from the driving section through the compensating section, and measuring the amount of waviness of the optical disk and the deviation of pit rows, etc. on the disk surface based on the signal from the compensating section. Disk inspection equipment. (2) The optical disk inspection device according to claim 1, wherein the characteristics of the driving section are frequency characteristics, displacement amount, and electric signal value characteristics. (3) The optical disk inspection apparatus according to claim 1, wherein the drive section is a focus drive section and a tracking drive section.