JPH0395733A - Optical reproducing system - Google Patents

Abstract

PURPOSE:To obtain the reproduced signal of an optical disk with high quality by using a time base servo suitable for each frequency component for time fluctuation. CONSTITUTION:A condensing beam driving part 8 is provided in the internal part of an optical head 1 and a condensing beam to be emitted form the optical head 1 is moved parallelly with the peripheral direction of an optical disk 2. Namely, in addition to the time base servo under the rotation control of the optical disk, the laser beam for information reproducing to be emitted from the optical head and to be condensed to the optical disk is moved parallelly to the peripheral direction of the optical disk and by controlling the move of the condensing beam as the time base servo, the time fluctuation is removed for the reproduced signal of the optical disk. Thus, by executing the satisfactory time base servo, the quality reduction for the reproduced signal of the optical disk can be suppressed at a minimum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical reproduction method for reproducing information from an optical information recording medium using a laser beam.

[Prior Art] Optical disk reproducing systems using laser light are capable of large-capacity recording and non-contact high-speed access, and are now being put to practical use as large-capacity memories. Optical discs are classified into read-only types known as compact discs and laser discs, write-once types that can be recorded by the user, and rewritable types that can be repeatedly recorded by the user.

In any of these optical discs, the optical disc is rotated at high speed, the optical head follows information recorded inside the optical disc, and a reproduced signal is detected.

When reproducing a signal recorded on an optical disc, temporal fluctuations occur in the reproduced signal due to fluctuations in the rotational speed of the disc, vibrations and eccentricity of the disc, and the like. These temporal fluctuations reduce the quality of the reproduced signal, and if this reproduced signal is video information, there is a possibility that the reproduced image will be distorted, and if this reproduced signal is recorded information from a computer, etc., data errors may occur. There is. An example of a method for correcting such temporal fluctuations in the reproduced signal is shown in FIG.

This conventionally known correction of temporal fluctuations in the reproduced signal (hereinafter referred to as time base servo) is based on the information recorded inside the optical disc 2 detected by the optical head (2), as shown in FIG. A phase comparator 4 compares the phase of the synchronizing signal generated by the optical information recording/reproducing device and the reference signal generated by the oscillator 3 built in the optical information reproducing device to detect a phase error. The control circuit 5 outputs a control signal to the drive circuit 6 to control the rotation of the optical disk so that this phase error is minimized. The drive circuit 6 supplies a drive current to the motor 7, and the rotation of the motor 7 is controlled.

[Problem to be solved by the invention]

However, timebase servo, which controls the rotation of an optical disk, is not perfect, and as optical disks become larger in diameter and rotate at higher speeds, the rotational inertia of the optical disk increases. In the control of the motor that is used to control the servo, there is a limit to the servo control due to temporal fluctuations in the high-frequency reproduction signal. This is because, among the temporal fluctuations of the reproduced signal, high-frequency fluctuations fluctuate quickly, and the rotation control cannot keep up with the rotational inertia of the optical disc.

An object of the present invention is to provide an optical reproduction method that can eliminate the above-mentioned drawbacks and minimize deterioration in the quality of an optical disc reproduction signal by performing good time servo. be.

[Means for Solving the Problems] The present invention provides an optical information recording and reproducing device that reproduces information using a laser beam, and an optical reproducing method using an optical head of the optical information reproducing device. The present invention is characterized in that it has means for controlling the emitted information reproducing laser beam by moving it in parallel to the circumferential direction of the optical disk, thereby eliminating temporal fluctuations in the reproduced signal of the optical disk.

[Operation] Since the optical head is independent of the rotation mechanism of the optical disk, it is not affected by the rotational inertia of the disk at all. Furthermore, since the parts that move the focused beam are small and lightweight, they can be moved with good response even at high speeds. Based on these principles, it is very effective to control the movement of the condensed beam itself emitted from the light source and the light beam in the circumferential direction of the optical disk as a time base servo.

That is, the optical reproducing method of the present invention is an optical disc reproducing method that reproduces information using laser light, and in addition to the time servo control by controlling the rotation of the optical disc, the optical reproducing method emits light from an optical head and focuses on the optical disc. By making the information reproducing laser beam (hereinafter referred to as the focused beam) move parallel to the circumferential direction of the optical disc and controlling the movement of the focused beam as a time base servo, the reproduction signal of the optical disc can be adjusted. Remove temporal variation.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a structural diagram showing an embodiment of the present invention. The optical reproduction method of this embodiment uses an optical disc 2.

This optical reproduction system includes an optical head 1, an oscillator 3, a phase comparator 4, control circuits 5A, 5B, a drive circuit 6A,
6B, a motor 7, a focused beam drive section 8, and a filter 9.

In an optical reproduction system with such a structure, the optical head l
reads the synchronization signal recorded on the optical disc 2. As the optical converter 1, a reproduction-only type, a rewritable type, etc. are used.

Oscillator 3 generates a reference signal.

The phase comparator 4 compares the synchronization signal from the optical head 1 and the reference signal from the oscillator 3 to generate a phase error.

The filter 9 separates the phase error from the phase comparator 4 into a low frequency component and a high frequency component.

The control circuit 5A generates a control signal based on the low-frequency phase error from the filter 9.

The drive circuit 6A operates according to the control signal from the control circuit 5A.
A drive current is applied to the motor 7.

The motor 7 rotates the optical disc 2.

The control circuit 5B generates a control signal based on the Takagi phase error from the filter 9.

The drive circuit 6B operates according to the control signal from the control circuit 5B.
A driving current is passed through the focused beam driving section 8.

The focused beam drive section 8 is provided inside the optical head 1 and moves the focused beam emitted from the optical head 1 in parallel to the circumferential direction of the optical disk 2. As shown in FIG. 2, this driving unit 8 may be configured using a galvanometer mirror 10 and a condensing lens 11 for the laser beam 13, or as shown in FIG. There is a method of moving the optical lens 11 in the circumferential direction of the disk 2 using the voice coil l2.

Next, the operation of this optical reproduction method will be explained.

The synchronization signal recorded inside the optical disk 2 detected by the optical head 1 and the reference signal generated by the oscillator 3 built in the optical information recording/reproducing device and the optical information reproducing device are electrically converted by the phase comparator circuit 4. Compare. Phase comparison circuit 4
The phase error signal detected by the filter 9 is separated into a low frequency signal and a high frequency signal. The control circuit 5A generates a control signal that controls the phase error to a minimum based on the low frequency distribution of the phase error signal. The drive circuit 6A is
A drive current is applied to the motor 7 according to a control signal from the control circuit 5A, and the rotation of the motor 7 is controlled. This controls the rotation of the optical disc.

Further, based on a high frequency portion of the phase error signal of the filter 9, a control circuit 5B generates a control signal for controlling the phase error to be minimized. The drive circuit 6B causes a drive current to flow through the focused beam drive circuit 8 in response to a control signal from the control circuit 5B. As a result, the focused beam drive section 8 inside the optical head 1 is controlled, and the focused beam moves. In other words, the temporal fluctuations in the reproduced signal are removed to some extent by controlling the rotation of the optical disk, and the temporal fluctuations in the frequency of the reproduced signal which cannot be completely eliminated by the rotation control method of the optical disk. For,
By controlling the movement of the optical axis of the information reproducing laser beam, temporal fluctuations in the reproduction signal of the optical disc can be effectively eliminated.

In this way, the optical head is equipped with a drive section, and by sending a control signal to this drive section and moving the focused beam in the rotational direction of the optical disk or in the opposite direction, the same effect as time base servo can be obtained. .

〔Effect of the invention〕

As explained above, in the present invention, in order to remove the temporal fluctuations of the optical disc playback signal, the temporal fluctuations are divided into low frequency commands and high frequency commands, and the temporal fluctuations are divided into low frequency commands and high frequency commands, and the temporal fluctuations are divided into low frequency commands and high frequency commands. By using the time base servo, it is possible to obtain a high quality optical disc reproduction signal.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are condensed lights emitted from the optical head inside the optical head according to the present invention. FIG. 4 is a block diagram showing a device for moving a beam parallel to the circumferential direction of an optical disk. FIG. 4 is a block diagram of a conventionally known device for correcting temporal fluctuations in a reproduced signal. 1... Optical head 2... Optical disk 3... Oscillator 4... Phase comparator 5A, 5B... Control circuit 6A, 6B... Drive circuit 7... ...Motor 8 ・ 9 ・ 10 ・ 11 ・ 12 ・ 13 ・Drive unit・Filter・Galvano mirror・Condensing lens・Voice coil・Laser light

Claims (1)

[Claims] (1) In an optical information recording and reproducing device that reproduces information using a laser beam and an optical reproducing method using an optical head of the optical information reproducing device, a laser beam for information reproducing focused on an optical disk is An optical reproducing system characterized by having means for controlling the optical disc by moving parallel to the circumferential direction of the optical disc, and eliminating temporal fluctuations in a reproduction signal of the optical disc.