JPH041946A - Exposure device for master optical disk - Google Patents

Abstract

PURPOSE:To eliminate the pitch variance and the fluctuation of the signal level by controlling a drive system to set the difference of speeds at 0 when the difference exists between the speeds obtained based on the detection value of a detection means which detects the moving speed toward the radius direction of a disk. CONSTITUTION:The detection means 10 and 11 are provided to the turntable support means 5 and 6 and an optical system support means 1 respectively and detects the moving speeds of them toward the radius direction of a disk. Then the control parts 14 - 18 control a drive system 9 so that the difference of speeds is set at 0 when the difference is produced between the speeds obtained based on the detection values of the means 10 and 11. As a result, no pitch variance is produced at the condensing position of the laser light despite the vibrations caused in an optical system 2 which outputs the laser light and on a turntable 4 which supports a glass master disk.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an improvement of a master exposure device used in manufacturing masters of optical discs, and in particular, to improvement of a master exposure device used in manufacturing masters of optical discs, and in particular, to improvement of a master disk exposure device used in mastering by an optical disk exposure device. The present invention relates to an optical disk master exposure device that eliminates pitch unevenness caused by the pitch unevenness.

(Prior art) In recent years, various data or audio/visual (AV)
Optical disks and magneto-optical disks, which are compact but can record large amounts of information, have become commonplace as media for recording signals. Writable optical information recording and reproducing devices have been widely developed.

Compression molding is a common method for manufacturing optical discs as disk-shaped recording media, and this method involves press-molding plastic softened by heating using a metal stand bar with minute protrusions corresponding to the bits. It is something to do.

A metal stand bar is created from a metal master or mother made using a glass master.

F2 glass master: It is manufactured using a dedicated master exposure equipment, but in conventional master exposure equipment, a photoresist as a photosensitive agent is placed on a glass master positioned on a turntable that is rotationally driven by the rotation axis of a spindle motor. After coating the photoresist uniformly, the portions corresponding to the bits are exposed by irradiating the photoresist with a tiny spot of a laser beam on and off from pickups placed opposite each other on the glass master disk. The metal mask is manufactured by plating using this resist master.

By the way, in the above-mentioned master exposure apparatus, if the optical element, actuator, or turntable vibrates during laser irradiation, it will have an adverse effect on the focus direction and pitch direction when forming the bit. It has been attempted to absorb and alleviate disturbance vibrations using static pressure bearings such as air spindles and air spindles.
For example, Japanese Unexamined Patent Publication No. 154356/1983). In addition, water cooling is often used as a cooling method for high-output exposure laser output means.

Vibrations occur due to cooling water circulation. Moreover, these components such as laser output means and turntable,
Since they are supported by the same pedestal, vibrations caused by the circulation of cooling water propagate to the entire device such as the turntable via the pedestal. Although the influence of vibration in the focus direction can be suppressed by focus servo, it is difficult to eliminate the influence of vibration in the two-pitch direction. Particularly when the vibrations of each component are out of phase, pitch unevenness becomes large, causing signal level fluctuations.

(Object of the Invention) The present invention has been made in view of the above, and even if vibration occurs on the optical system side that outputs the laser and the turntable side that supports the glass master disk, pitch unevenness will occur at the converging position of the laser beam. It is an object of the present invention to provide an optical disk master exposure apparatus that does not cause the occurrence of the problem.

(Structure of the Invention) In order to achieve the above object, the present invention provides a radial direction by driving at least one of means for supporting a turntable that supports a master disc and optical system support means for irradiating a laser beam onto the master disc. In the optical disk master exposure apparatus configured to be movable, the turntable support means and the detection means for detecting the movement speed in the radial direction provided on the optical system support means, respectively, and the detection means based on the detected values by each detection means. and a control unit that controls the drive system so that when there is a difference between the obtained speeds, the speed difference becomes O. ,
The control unit stops the exposure operation by the optical system when the speed difference obtained based on the detected values by the two detection means exceeds a predetermined tolerance value, and displays the level of the speed difference on the display unit. It is characterized by

Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is an explanatory diagram of the main part configuration of an optical disk master exposure apparatus according to an embodiment of the present invention, in which an optical bench l including an exposure optical system is equipped with an objective lens driving actuator 2, and an actuator 2 for driving an objective lens is mounted on the optical bench l including an exposure optical system. A photoresist substrate (glass master) 3 is coaxially positioned on the arranged turntable 4. The objective lens at the tip of the actuator 2 is subjected to focus servo so as to maintain the same focal position on the photoresist substrate 3. By moving either the optical bench l or the turntable 4 in the radial direction of the substrate, a spiral or concentric exposure latent image is formed on the substrate 3 by the laser beam irradiated from the objective lens. In this embodiment, an example is shown in which the optical bench 1 is fixed and the turntable 4 side is movable in the radial direction.

The turntable 4 is rotatably supported by a movable table 5 fixed on an air slider 6. Inside the screw hole of the nut 5a extending from the bottom surface of the movable table 5,
A spiral shaft 7 connected to the output shaft of a motor (drive system) 9 via a coupling 8 is screwed into the movable table 5 by rotation of the spiral shaft 7 in both forward and reverse directions.
moves in the radial direction shown by arrow A while being guided by the air slider 6.

A vibration acceleration pickup (acceleration sensor) 10 as a vibration detection means for detecting vibration in the moving direction A of the optical bench 1 is arranged at a suitable place 1 of the optical bench 1, for example, on the illustrated end face, and at a suitable place of the movable table 5. 1. For example, a vibration acceleration pickup 1) for detecting vibrations of the movable table 5 in the moving direction A is arranged also on the illustrated end face in the moving direction.

The detection signals from each vibration acceleration pickup 10.1) are input to an amplifier 12.13, respectively. In the present invention, by automatically controlling the rotational speed of the motor 9 so that the output difference from each amplifier I2. It is characterized by eliminating.

In the block diagram shown in the figure, each A〉・B I2, !
3 is input to the first differential amplifier 14 that detects the acceleration difference, the differential amplifier 14 outputs a difference signal (acceleration difference) to the calculation feedback circuit 15. The calculation feedback circuit 15 calculates a relative speed difference by integrating the input acceleration difference over time, and uses this value as a second
It is output to one input terminal of the differential amplifier 16. The second differential amplifier 16 uses the reference speed signal of the movable table 5 outputted from the motor drive command circuit 17 as the other input, and outputs a comparison value obtained by comparing both human power signals to the motor driver circuit I8. In the motor driver circuit (control means) 18,
Control is performed to finely adjust the rotational speed according to the input speed difference value, and a control signal is output to the motor 9. For example, if the speed difference is positive, the rotational speed is decreased, and if the speed difference is negative, the rotational speed is increased.

Furthermore, if the output difference of each acceleration pickup IO1+16) increases beyond a predetermined tolerance value due to external factors such as collision or contact with an object, the exposure operation is stopped and the speed difference is output. The level may be controlled to be displayed on the display unit.

With this configuration, it is possible to increase the operating rate of the apparatus by omitting the exposure process for masters that are obviously defective, and to make defective judgments. In addition, by displaying the speed difference output level on the monitor,
It can be known that an abnormality has occurred on either the optical bench l side or the turntable 4 side. Further, since it is possible to monitor an increase in vibration due to deterioration of the feed mechanism such as the spiral shaft 7, it is possible to easily determine when it is time for maintenance.

In the present invention, as shown in FIG. Since the correction is made by controlling the constituent motors, pitch unevenness can be suppressed even in the presence of vibration, and fluctuations in signal level during exposure of the photoresist substrate can be eliminated.

Various types of vibration detection means can be used in addition to the acceleration sensor used in the above embodiment.

For example, it is also possible to use minute displacement measuring means such as an interferometer or a laser length measuring device that uses a special reference stand as a reference. In addition, for length measuring instruments, etc., the DC of the movable side support
It is necessary to add a circuit to remove the temporary displacement.

In the above embodiment, an example was shown in which the spiral shaft 7 is rotationally driven by a motor 9 as a rotary machine whose output shaft rotates, such as a servo motor or a stepping motor. It is also possible to apply a motor in which the side) moves linearly forward and backward in the axial direction. Linear motors have no mechanical errors, so
It is possible to perform highly accurate radial movement.

Therefore, in the claims, the drive system is a concept that includes only a motor whose output shaft rotates, and includes a near motor whose output shaft moves back and forth in the axial direction.

(Effects of the Invention) As described above, according to the present invention, one or both of the turntable side that supports the master disc and the optical system side that irradiates the master disc with laser light is configured to be movable in the pitch direction. In the optical disc master exposure system, the value of the acceleration difference detected by each vibration detection means arranged on the turntable side and the optical system side is converted into a speed difference, and this speed difference is compared with a reference speed difference. Based on the speed difference from the reference speed obtained by It is possible to eliminate pitch unevenness and eliminate signal level fluctuations.

In addition, if the vibration detected by each of the above detection means is too large to be corrected, the exposure operation is stopped and the level of vibration is displayed on the display to prevent a decrease in the out-of-work rate of the equipment. It can be prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main part configuration of an instant embodiment of the present invention. l...Optical bench 2...Actuator for driving objective lens 3...Photoresist substrate 4-...Turntable 5...Movable table 7...Spiral shaft 9-...Motor 10.1) ...Vibration acceleration pickup (detection means) 12, I3...Vibration acceleration pickup 14.16...Differential amplifier 1
5... Arithmetic feedback circuit 17... Motor drive command circuit I8... Motor driver circuit

Claims (2)

[Claims] (1) An optical disc configured to be movable in the radial direction by driving at least one of a means for supporting a turntable that holds a master disc and a means for supporting an optical system that irradiates a laser beam onto the master disc by a drive system. In the master exposure apparatus, the turntable support means, the detection means for detecting the movement speed in the radial direction provided on the optical system support means, and the speed difference obtained based on the detection value by each detection means. When there is a difference in speed, the speed difference is set to 0.
An optical disk master exposure apparatus comprising: a control section that controls the drive system so as to perform the following steps. (2) In the optical disk master exposure apparatus, the control section stops the exposure operation by the optical system when the speed difference obtained based on the detection value by each of the detection means exceeds a predetermined tolerance value, and 2. The optical disk master exposure apparatus according to claim 1, wherein the level of the speed difference is displayed on the display section.