JPH02165434A - optical disc playback device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc playback device for reading information from an optical disc.

Conventional Technology In an optical disc playback device that uses a light beam to play back information recorded on a recording track from an optical disc having a recording surface on which a recording track is formed, the optical disc is rotated and the light beam is Focus control is performed to make the light beam incident on the recording surface of the rotating optical disc in an appropriate focused state, and tracking control is performed to make the light beam appropriately follow the recording track of the optical disc.

That is, for example, an objective lens that makes a light beam incident on the recording surface of an optical disk by focus control,
The distance from this objective lens to the recording surface is maintained so that the position toward or away from the recording surface is controlled and the light beam is properly focused on the recording surface.

In addition, tracking control controls the position of the objective lens in the plane along the recording surface of the optical disk, so that the arrival position of the light beam incident on the recording surface is placed correctly on the recording track. Move across the recording track.

In this manner, various controls are performed on the light beam that is incident on the recording surface of the rotating optical disk via the objective lens, and as a result, an appropriate light beam that is incident on the recording surface is obtained.

However, even under the various controls described above, due to deformation of the optical disc, etc., the light beam that enters the recording surface of the optical disc through the objective lens may not be able to reach the recording surface of the optical disc at the incident position. The optical axis of the incident light beam is tilted with respect to the perpendicular direction.

In this case, the spot of the incident light beam on the recording surface of the optical disc is expanded due to the influence of coma aberration, and as a result, for example, an increase in crosstalk components from adjacent recording tracks in the reproduced information, , problems such as deterioration of frequency characteristics of reproduced information occur.

It is desired to detect such an inclination (hereinafter referred to as skew) between the optical axis of the light beam and the vertical direction of the optical disc and to control the skew to zero.

FIG. 7 shows a conventional example for solving this problem. The light beam emitted from the light emitting element 21 is transmitted to the optical disc 2.
The light receiving elements 22 and 23 detect the respective reflection amounts, and the differential amplifier 24 calculates the difference in the reflection amounts of the light receiving elements 22 and 23. It is configured to operate so as to equalize the amount of reflection at the light receiving elements 22 and 23 by moving the light receiving elements 22 and 23.

Problems to be Solved by the Invention However, in the conventional method, a dedicated light-emitting element and light-receiving element were required in order to detect skew, resulting in a relatively large-scale configuration. Furthermore, since the tilt is detected using dedicated light-emitting elements and light-receiving elements, there is uncertainty in the correlation between the recording surface of the optical disc that is hit by the light emitted from one light-emitting element and the increase or decrease in crosstalk of the reproduced carrier wave. There are other inconveniences.

In view of this, the present invention detects an increase or decrease in crosstalk directly from a reproduced carrier wave, and uses this detection.

It is an object of the present invention to provide a disk-shaped recording medium reproducing device in which control to reduce skew to zero is appropriately performed.

Means for Solving the Problems In order to achieve the above-mentioned objects, the disc-shaped recording medium reproducing device according to the present invention is an optical recording medium that converts the frequency of a video signal or an information signal and an information code added at the time of recording. In the type disc, means for extracting reproduced carrier wave signals from code mismatching portions of adjacent recording tracks in an information code section; means for detecting crosstalk caused by adjacent recording track signals from the extracted carrier wave signals; A device having a configuration that controls the light beam to be irradiated perpendicularly to the information recording surface by means of changing the light beam irradiated onto the information recording surface in a direction across the information track in accordance with the talk. It is.

Effect The present invention has the above-described configuration, which eliminates the need for a dedicated light-emitting element and light-receiving element for detecting skew, and improves performance by controlling the skew to zero by increasing and decreasing the crosstalk of the reproduced carrier wave. This results in a circuit groove bottom that is relatively simple and can be made into 10 circuits.

Embodiment Hereinafter, an optical disc reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the invention. An FM modulated signal recorded on the optical disc 2 is reproduced by an optical device 3 from an optical disc 2 being rotated by a spindle motor 1. The reproduced carrier wave signal reproduced by the optical device 3 is converted into an electric signal by the amplifier 4, and is supplied to the signal processing 6 and the reproduced carrier wave sampling circuit 6. In signal processing 6, the reproduced carrier wave signal is subjected to various processing and outputted to a television receiver. On the other hand, the reproduced carrier wave signal applied to the reproduced carrier wave sampling circuit 6 is extracted only in a desired section, and the crosstalk included in the reproduced carrier wave signal is detected in the cross-reference sampling circuit 7, and based on this detected signal, A light beam axis correction circuit 8 generates a light beam skew correction signal t. Then, move the tilt mechanism body part 9.

The structure is such that the skew of the light beam is zero.

The operation of the optical disc reproducing apparatus configured as described above will be described below with reference to FIGS. 1, 2, and 3. FIG. 2 is a diagram showing the modulation signal of the information code section of the FM modulation signal recorded on the optical disc,
FIG. 3 is a diagram showing the frequency distribution of an optical disc recording signal of an optical video disc. For example, as shown in FIG. 2, the carrier wave signal of the mismatched portion in the information code section of the modulated wave of the FM modulated wave of the reproduced track and the modulated signal of the inner and outer tracks adjacent to the reproduced track on the optical disk is extracted. In FIG. 2, the sections where the modulation signal of the reproduced track is in a high state and the modulation signal of an adjacent track is in a low state are indicated by sections I to section ■. As is clear from the frequency distribution shown in FIG. 3, the frequency of the signal recorded on the optical disc is determined under certain conditions. When the information code of the modulation signal is in the low state, it is at the frequency f, and when it is in the high state, it is at the frequency fH. At this time, crosstalk from each adjacent track can be detected by detecting the frequency level f in sections ① to ② in FIG. The crosstalk in sections I and If is in sections III and IT.
If the crosstalk is larger than the crosstalk in sections I11., it indicates that the optical axis of the light beam is inclined to the inside of the optical disk, and on the contrary, the crosstalk in sections I and II is larger than that in sections I11. If it is smaller than the IV crosstalk, it indicates that the optical axis of the light beam is tilted to the outside of the optical disc. Therefore, interval I,
The optical beam axis correction circuit 8 in FIG. 1 outputs a signal to the tilt mechanism drive section 9 so that the crosstalk between II and sections III and IV becomes equal.

As described above, according to the embodiment of the present invention, there are provided a means for extracting a recovered carrier signal corresponding to a low or no state in an information code section, a means for detecting crosstalk from the extracted recovered carrier signal, and a means for detecting crosstalk from the extracted recovered carrier signal. By controlling the light beam to be irradiated perpendicularly to the information recording surface by means of changing the optical axis of the light beam irradiated onto the information recording surface in a direction that crosses the information track according to the crosstalk, without using light-emitting or light-receiving elements.

The skew can be made zero directly using the crosstalk of the regenerated carrier signal.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows a second embodiment of the invention.

In FIG. 4, 1 is a spindle motor, 2 is an optical disk, 3 is an optical device, 4 is an amplifier, 6 is a signal processor, 6 is a reproduction carrier extraction circuit, 7 is a crosstalk extraction circuit, 9 is a tilt mechanism drive unit, The above configuration is similar to the configuration shown in FIG. The difference from the configuration shown in FIG.
/mu conversion 12 and drive circuit 13.

The operation will be explained below using FIGS. 4 and 6. As shown in FIG. 6, the microcomputer 11 in FIG.
A minute pulse signal is generated at the output of the drive circuit 13, and the tilt mechanism drive section 9 causes the tilt between the optical disk surface and the optical axis of the light beam to minutely change. The microcomputer 11 determines the direction of skew based on the increase or decrease in crosstalk that occurs at that time, and controls the skew so that it becomes zero or below a certain value.

That is, as shown in FIG. 6, for example, when the output of the drive circuit 13 in FIG. 4 is positive, the tilt mechanism drive section 9 operates so that the optical axis is tilted inward, and when the output is negative, the optical axis is tilted inward. If the tilt mechanism and drive section 9 operate so as to tilt outward, the output of the crosstalk extraction circuit 7 changes as shown in FIG. 6. When the skew is tilted inward, as shown in FIG. 6a, the crosstalk increases; on the other hand, when the skew is tilted outward, as shown in FIG. 5, the crosstalk decreases. From this result, the slope of the skew.

In other words, the direction of warpage of the optical disc can also be determined.

As described above, the light beam correction circuit 8 is converted into a MU/D converter 10,
By configuring the microcomputer 11, the D/MU converter 12, and the drive circuit 13, it is possible to eliminate crosstalk caused by skew changes due to minute signals generated by the microcomputer 11 without checking the relationship between the section where the reproduced carrier wave is extracted and adjacent tracks. By determining the increase/decrease in talk using the microcomputer 11, the direction of the skew inclination and the direction of warpage of the optical disk can be determined, and control can be performed to reduce the skew to zero.

FIG. 6 shows a crosstalk extraction circuit for an optical disc playback device showing a third embodiment of the present invention. The difference from FIG. 4 is that the crosstalk extraction circuit 7 and the trap circuit 14. This is shown in the configuration of the amplifier 16.

The operation of the above configuration will be explained. In this configuration,
For example, a regenerated carrier wave corresponding to a high or low state of the information code of the modulation signal of the regenerated carrier wave signal is extracted by the regenerated carrier wave extracting circuit 6, and a carrier frequency corresponding to the high or low state of the information code of the modulation signal is removed by the trap circuit 1.
4, only the crosstalk component is applied to the amplifier 16 and is increased to a level suitable for the optical beam axis correction circuit 8.

By providing the trap circuit 14 and the amplifier 16 as described above, crosstalk in the sampled section can be detected, and when used in conjunction with the second embodiment, the information codes of the modulation signals of the recording track and the adjacent track match. Regardless of the mismatch, the skew can be controlled to zero using crosstalk. This means - for boat fishing, CAT
, it is shown that the skew can be controlled without any difference between CI4 disks.

Effects of the Invention As described above, the present invention provides a means for extracting a reproduced carrier wave corresponding to a low or high state in an information code section, and a method for extracting a reproduced carrier wave signal from the extracted reproduced carrier wave signal on an information recording surface on which the reproduced carrier wave signal is recorded. The system is configured to control the skew to zero by means of detecting crosstalk caused by adjacent recording tracks and means of changing the skew according to the crosstalk. Since the crosstalk of the reproduced carrier signal is directly used to control the skew to zero without using a light-emitting element or light-receiving element dedicated to correction, more appropriate control can be obtained, and the configuration allows for greater circuit integration. is obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical disc playback device according to a first embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams and characteristic diagrams for explaining the embodiment of FIG. 1, and FIG. 4 6 is a block diagram of an optical disc reproducing apparatus according to a second embodiment of the present invention, FIG. 6 is a waveform diagram for explaining the embodiment of FIG. 4, and FIG. 6 is a diagram of an optical disc according to a third embodiment of the present invention. FIG. 7 is a block diagram of a conventional optical disc reproducing apparatus. 6... Regenerated carrier wave extraction circuit, 7... Crosstalk extraction circuit, 8... Light beam axis correction circuit. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (7)

[Claims] (1) When reproducing a signal from an optical disc on which a video signal or information signal and an information code added at the time of recording are FM-modulated and recorded, the reproduction corresponds to the low or high state of the information code section. means for extracting a carrier wave signal; means for detecting, from the extracted reproduced carrier wave signal, crosstalk caused by signals of recording tracks adjacent to recording tracks of an information recording surface on which the reproduced carrier wave signal is recorded; The light beam is controlled to be irradiated perpendicularly to the information recording surface by means of changing the optical axis of the light beam irradiated onto the information recording surface in a direction that crosses the information track in response to crosstalk. Characteristic optical disc playback device. (2) The means for extracting the reproduced carrier wave consists of the first code, which is the information code section of the modulated signal of the reproduced carrier wave from the reproduced recording track, and the FM signals recorded on the adjacent recording tracks inside and outside the recording track on the information recording surface. In the second code and the third code, which are information code intervals of the modulated signal of the modulated wave, a first mismatch interval between the first code and the second code and a first code and the third code. means for extracting a signal section with a second mismatch section, and the crosstalk detection means detects a first crosstalk in the first mismatch section and a second crosstalk in the second mismatch section. The detecting means is characterized in that the means for changing the optical axis of the light beam is a means for changing the optical axis of the light beam so that the first crosstalk and the second crosstalk match. An optical disc reproducing apparatus according to claim 1. (3) The means for changing the optical axis of the light beam records the crosstalk obtained by crosstalk detection on the information recording surface with the first code that is the information code section of the modulated signal of the reproduced carrier wave from the reproduced recording track. A second code and a third code which are information code sections of the modulation signal of the FM modulated wave recorded on the inner and outer adjacent tracks of the track, and the first code and the second code are Only the parts corresponding to the mismatching section and the second mismatching section between the first code and the third code are extracted, and the crosstalk in the first mismatching section is made equal to the crosstalk in the second mismatching section. 2. The optical disk reproducing apparatus according to claim 1, further comprising means for changing the optical axis of the light beam. (4) The means for changing the optical axis of the light beam in the direction across the information track is a means for detecting the direction of warpage of the optical disk based on the increase or decrease in the amount of crosstalk when a slight change is made to the light beam. An optical disc playback device according to claim 1, characterized in that: (5) The means for extracting the reproduced carrier wave signal is means for extracting the reproduced carrier wave corresponding to the high state of the information code section, and the means for detecting crosstalk is the means for extracting the reproduced carrier wave signal from the extracted reproduced carrier wave signal. The signal of the recording track adjacent to the recording track of the information recording surface that is being recorded is an FM modulation signal of the information code section or the vertical retrace section, and this is a means for detecting crosstalk of a specific frequency caused by this FM modulation signal. An optical disc reproducing apparatus according to claim 1, characterized in that: (6) The means for extracting the recovered carrier wave signal is means for extracting the recovered carrier wave corresponding to the high state of the information code section, and the means for detecting crosstalk is the means for extracting the recovered carrier wave corresponding to the high state of the information code section from the extracted recovered carrier wave signal. 2. The optical disk reproducing apparatus according to claim 1, further comprising means for detecting crosstalk by removing a specific frequency corresponding to the reproduced carrier wave signal from the reproduced carrier wave signal. (7) The means for extracting the recovered carrier wave signal is means for extracting the recovered carrier wave corresponding to the low state of the information code section, and the means for detecting crosstalk is the means for extracting the recovered carrier wave corresponding to the low state of the information code section from the extracted recovered carrier wave signal. 2. The optical disk reproducing apparatus according to claim 1, further comprising means for detecting crosstalk by removing a specific frequency corresponding to the reproduced carrier wave signal from the reproduced carrier wave signal.