JPS60123189A - Jitter corrector for disk player - Google Patents

Abstract

PURPOSE:To reduce the number of necessary memories by using the clocks of the same signal system to control the revolution of a motor and to read data. CONSTITUTION:For the reflected signal of laser light 5, a video subcarrier frequency f1 synchronizing with a jitter is detected by a burst rod circuit 7 via a video detection circuit 6 and according to a burst signal. This reflected signal is multiplied four times (4f1) through a 4-multiplying circuit 9, and a video signal is sampled by the signal (4f1) via an A/D converter 8 then written to a memory 11. While a signal of 4-fold as much as a frequency (f) oscillated from an oscillator 14 is divided by a frequency dividing circuit 15 to obtain a reference frequency. This reference frequency is compared with an oscillation angle frequency obtained by a motor 3 by a phase comparator 16, and the phase difference is set at zero. Then the data stored in the memory 11 is read out with a signal containing no jitter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a jitter correction device for a disc player. More specifically, there are two types of data detection for video discs: an optical method using laser light and a stylus contact method using a piezoelectric conversion needle or a capacitive needle. ~ several μm,
Further, pits in the optical type are approximately 1.6 μm. Therefore, the position error in the focus direction of the pickup, in the direction perpendicular to the track, and in the tangential direction to the track is 0.1
It must be controlled with high precision on the order of μm. Among these, the present invention relates to a jitter correction device for correcting the tangential direction of tracks in optical discs, button contact discs, and the like.

Generally, so-called jitter correction in the tangential direction of a disk track has been performed by mechanically moving a pickup. However, the mechanical movement method had the following drawbacks. In other words, in the optical system, the focus direction,
There are three position controls: track direction and jitter one direction, and the needle contact type has two position controls: track direction and jitter one direction.
Therefore, if mechanical movement is applied to the pickup in one direction for jitter, it will adversely affect the servo system in other directions, and mechanical methods have the disadvantage that correction accuracy is low. was there. Furthermore, a memory-based method is used for jitter correction in some business VTRs. This memory method is a method in which data read from a VTR is temporarily stored in a memory and then read out from this memory at a constant speed, and has the advantage of high correction accuracy.

However, because writing to memory and reading from memory do not match, reading from memory may be too fast and the data in memory is lost, or reading from memory may be too slow and the memory capacity is insufficient. Therefore, there is a problem that a large capacity memory is used, such as requiring a memory capacity for several frames to be read out from a VTR and stored, resulting in an increase in cost.

The present invention was made to solve the above-mentioned problems, and it detects a data signal from a video disk rotated by a motor using a pickup, stores this data signal in a memory, and then reads it out at a constant speed. The disc player includes: a burst rod circuit for obtaining a write signal synchronized with a burst signal frequency in a reproduction signal from the disc; a crystal oscillator that oscillates at a constant frequency four times that of a video subcarrier signal; a PLL servo circuit for controlling the motor to a constant rotation speed based on an oscillation output signal of an oscillator; a memory for A/D converting a playback signal from the disk and writing it as a write signal from the burst rod circuit; The device includes a D/A converter that reads data stored in the memory based on the oscillation output signal of the oscillator and converts it from D/A. In this way, by controlling the rotation of the motor and reading data using the same signal system clock, the memory has the effect of requiring a minimum capacity, for example, the capacity of the IH.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The case of an optical disc as an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (1) is an optical disk, and a track (2) of this optical disk (1) stores, for example, a signal obtained by FM modulating a video signal, an audio signal, etc.

This optical disk (1) is directly connected to a motor (3) and has an 18
00 rpm, that is, it rotates 30 times per second.

An optical pickup (4) is provided facing the surface of the optical disk (1) so as to move toward the center of the optical disk (1) while keeping a servo (feed servo) always near the center of the actuator movable part. Further, a laser beam (5) is irradiated onto the optical disk (1), and the reflected light is detected by a photodiode or the like in an optical pickup (4). On the output side of this optical pickup (4), a high frequency signal processing and video signal detection circuit (6
) is provided on the output side of this circuit (6), and P L L (P
hase 1. A burst rod circuit (7) consisting of a bent loop circuit is coupled thereto, and an A/D converter (8) for converting a video signal from an analog signal to a digital signal is provided. The output side of the burst rod circuit (7) is connected to the A/D converter (8) and memory control via a quadruple frequency circuit (9) that multiplies the frequency of the output signal by an integer, specifically, by four times. coupled to the circuit (10). This memory control circuit (10) is a control circuit (
10) is connected to memory (11) by a control bus and an address bus.
), and said A/D converter (8) is also coupled to a memory (11). An output terminal (13) for a jitter-corrected analog video signal is provided on the output side of this memory (11) via a D/A converter (12).

Next, (14) is a crystal oscillator, and this oscillator (14
) oscillates a signal with a frequency (14,348 MHz) that is four times the video subcarrier frequency (f). The output side of this oscillator (14) is coupled to the memory controller (10) and the D/A converter. Also, this oscillator (1
4) is coupled to one input side of a phase comparator (16) via a 1/13650 frequency divider circuit (i5), and the other input side of this phase comparator (16) is connected to the motor (3
), and furthermore, the output side of this phase comparator (16) is connected to the motor (3) via a motor drive circuit (17).
) is combined with And these phase comparators (1
6), the motor drive circuit (17), and the motor (3) constitute a motor servo circuit consisting of a PLL circuit.

Next, the operation of the circuit according to the present invention will be explained.

Laser light (5) from the optical pickup (4) is irradiated onto the disk (1) rotated by the motor (3), and the reflected light is detected by a photodetector element such as a photodiode in the optical pickup (4). . This photodetection signal is sent to a high frequency signal processing and video detection circuit (6), as shown in Fig. 2(a).
This results in a video signal containing jitter as shown in the figure below. This video signal is sent to an A/D converter (8) and a burst strand circuit (7). This burst strand circuit (7)
Then, the video subcarrier frequency (
fl) signal, and further transmits this signal to a quadruple frequency circuit (9)
The signal is quadrupled (4f+). 4f thus obtained.

The signal is sent to the A/D converter (8), and during 111,
The video signal is sampled using this signal 4f and written into the memory (11). More specifically, 174 periods of a burst signal of a video signal including jitter are T,
Then, during IH, T 1 (or an integer fraction thereof)
When the 1/4 period of the burst signal (B) becomes T2, the period of I - 1 is T2 or an integer fraction thereof. memory (11) sampled at time intervals of
is written to and absorbs jitter.

On the other hand, the oscillator (14) generates the video subcarrier frequency (f
= 3.579545 MHz)
f = 14.318MHz), and this signal is frequency-divided by the frequency divider circuit (15) to obtain a signal of 10501 (z) and manually input it to the phase comparator (16).The motor (3) has no jitter. Since it outputs 35 pulses per rotation and rotates 300 times per second, a signal of 10501 (z) is output, but when there is jitter, a signal slightly increased or decreased from 1050 Hz is output to the phase comparator ( 16) is sent to the other input side.

Then, the phase comparator (16) compares the phase difference between the oscillation angular frequency by the motor (3) and the reference angular frequency i based on the reference frequency from the frequency dividing circuit (15), and generates an error according to this phase difference. A voltage is generated, and the motor drive circuit (17) applies a voltage to the motor (3) so that the error voltage becomes zero, that is, the oscillation angular frequency of the motor (3) approaches the reference frequency. The rotation of the motor (3) is controlled until the oscillation angular frequency and the reference frequency match and are locked.

The A/D converted video data stored in the memory (11) is read out based on a jitter-free and accurate signal from the oscillator (14).

The D/A converter (12) converts it back to the original analog signal and outputs it.

In the above embodiments, the case of an optical disk was explained, but it goes without saying that the case of a nail contact type can also be used as is by making some changes in accordance with the change in the number of rotations of the disk.

As described above, the video signal reproduced from the disc contains jitter due to eccentricity of the disc, wow and flutter of the motor, etc., but the present invention provides a signal synchronized with the jitter by using a burst signal of the video signal containing this jitter. This allows the video signal to be A/D converted and written to the memory, while the rotation of the motor is controlled using signals from an accurate oscillator, and furthermore, the video signal is read from the memory using accurate signals from the motor control oscillator. I decided to put it out. Therefore, the total number of cycles in one revolution of the video signal including jitter and the total number of cycles in one revolution of the oscillator without jitter for motor control and reading are exactly equal, and It is possible to eliminate the DC-like memory amount drift, and it is possible to correct jitter using low-capacity memory.

By the way, the memory capacity for the video data IH is divided into, for example, four blocks and stored sequentially.
Jitter can be sufficiently removed even with a capacity of 1 to 2 H.

Furthermore, since there is no need to mechanically move the pickup in the tangential direction of the track, the structure of the pickup is simple and reliability is improved, and color unevenness is also improved by improving the accuracy of jitter correction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a jitter correction device according to the present invention, and FIGS. 2(a) and 2(b) are waveform diagrams of a video signal and a sampling pulse. (1) Disc, (2)...Track, (3) Motor, (4)...Pickup, (5) Laser light,
(6)...High frequency signal processing and video signal detection circuit, (7)...Burstron circuit, (8)...A/
D converter, (9)...quadruple frequency circuit, (10)...memory control circuit, (11)...memory, (12)...D
/A converter, (13)...output terminal, (14)...
Oscillator, (]5) Frequency divider circuit, (16) Phase comparator, (]7) Motor drive circuit. Applicant General Co., Ltd. Procedures Amendment (Method) 1. Display of the case Japanese Patent Application No. 58-230223 2, name of the invention Jitter correction device 3 for disk players, person making the correction Relationship with the case Patent applicant address 1116 Suenaga, Takatsu-ku, Yozaki City, Kanagawa Prefecture Name (6)
61) General Co., Ltd. Representative Kanazawa - Department 4, Agent

Claims (1)

[Scope of Claims] (1) A disc player in which a data signal is detected by a pickup from a video disc rotated by a motor, the data signal is temporarily stored in a memory, and then read out at a constant speed from the disc. a burst strand circuit for obtaining a write signal synchronized with a burst signal frequency in a reproduced signal; an oscillator that oscillates a signal synchronized with a frequency of a video subcarrier signal; With a servo circuit to control the rotation speed. A memory that A/D converts a reproduction signal from the disk and writes it as a write signal from the burst strand circuit; and a memory that reads data stored in the memory based on an oscillation output signal of the oscillator and performs D/A conversion. 1. A jitter correction device for a disk player, comprising a D/A converter. (2. In claim 1) < - A jitter correction device for a disk player, in which the strod circuit and the motor servo circuit each include a PLL circuit. (3) The jitter correction device for a disc player according to claim 1, wherein writing and reading of the data signal is performed at a frequency four times that of the video subcarrier signal.