JPH03156734A - Optical disk search device - Google Patents

Abstract

PURPOSE:To make the search time for a CLV disk the same as that for a CAV disk by applying reproduction with the input control of a buffer memory and the track kick control while keeping number of revolutions of a spindle motor to a value close to number of revolutions in the innermost circumference of the CLV disk. CONSTITUTION:A ratio of an output of an optical pickup radial direction posi tion sensor 15 to the radius of innermost circumference is obtained, the fre quency of an output of a reference clock generator 8 is multiplied by a value of a number of revolution multiple calculator 16, and an input address for a buffer memory 13 is revised by an output of a multiplier 17. An output address of the buffer memory 13 is revised by an output of the reference clock generator 8, the input period of the buffer memory 13 and the tracking are controlled by the output of the calculator 16. Thus, even when the optical pickup 2 is at any position, the number of revolutions of a spindle 11 is kept to a speed close to the speed at the innermost circumference. Thus, the search time is decreased as near as that of a CAV disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a search device for optical discs with constant linear velocity.

Conventional technology In recent years, high-speed search of optical discs has become important.

The recording method uses a constant linear velocity method (
Hereinafter, it will be abbreviated as CLv. ) and the constant angular velocity method (hereinafter abbreviated as CA), which is characterized by high-speed search. Both types are used for video discs. below,
A video disc using the CLV system will be explained.

As a conventional optical disc search device, for example, "Laser Disc Technical Book" ASCII Publishing Co. L5BN
4-87148-20G-5.

FIG. 4 is a block diagram showing the configuration of a conventional optical disc search device.

In FIG. 4, 1 is an optical disk, 2 is an optical pickup, 3 is an audio signal demodulator, 4 is a video signal demodulator, 5 is a horizontal synchronizing signal separator, 6 is a phase comparator, and 7 is a reference horizontal synchronizing signal generator. , 8 is a reference clock generator, 9 is a compensation amplifier,
10 is a drive amplifier, and 11 is a spindle motor.

Next, this operation will be explained.

An optical pickup 2 tracks a bit string on an optical disk 1 and outputs a high frequency signal. These outputs are input to an audio signal demodulator 3 and a video signal demodulator 4. The reproduced video signal output, which is the output of the video signal demodulator 4, is input to a horizontal synchronizing signal separator 5, where the horizontal synchronizing signal is separated. On the other hand, the reference clock from the reference clock generator 8 is frequency-divided by the reference horizontal synchronization signal generator 7, and a reference horizontal synchronization signal is output. These horizontal synchronization signals and reference horizontal synchronization signals are input to a phase comparator 6. The output of the phase comparator 6, which is an error signal, is sent to a compensation amplifier 9 with low-pass filter characteristics.
is input. The output of this amplifier 9 is input to a drive amplifier 10 to drive a spindle motor 11.

Now, assume that the optical pickup 2 is searched from the innermost circumference to the outermost circumference. In the case of a CAV disc, the process completes in about 3 seconds. This is determined by the slider movement time, the tracking kick and retraction time, and the time until the spindle servo is activated.

Problems to be Solved by the Invention However, in the above conventional configuration, in the case of a CLv disk, it took a long time until the spindle servo was activated, and it took more than 10 seconds to search from the innermost circumference to the outermost circumference.

In a CLV disk, the rotation speed must be lowered from about 180 Orpm at the innermost circumference to about 60 Orpm at the outermost circumference. However, since the mass of the disk is large, it is impossible for a spindle motor to which a limited power supply capacity is supplied to rapidly reduce the rotational speed. Therefore, there was a problem that the search time was long.

The present invention solves the above-mentioned conventional problems, and aims to provide an optical disc search device that has almost the same search time for CLV discs as for CAV discs.

Means for Solving the Problems To achieve this object, the optical disc search device of the present invention determines an optical pickup radial position sensor and a ratio between the output of the sensor and the innermost radius when reproducing a CLv disc. A rotation speed multiplier calculator, a frequency multiplier that multiplies the frequency of the output of the reference clock generator by the value of the output of the calculator, and an input address of a buffer memory that receives the high frequency signal of the optical pickup output as input by the multiplier. a first address counter that updates the output address of the buffer memory with the output of the reference clock generator; a second address counter that updates the output address of the buffer memory with the output of the reference clock generator; It has a memory kick controller that controls the input period and track kick.

According to the above-described configuration, the present invention performs playback of a CLV disk by controlling the input of the buffer memory and controlling the track kick while maintaining the rotational speed of the spindle motor at a value close to the rotational speed at the innermost circumference.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an optical disc search device in an embodiment of the present invention.

In FIG. 1, 1 is an optical disk, 2 is an optical pickup, 3 is an audio signal demodulator, 4 is a video signal demodulator, 5 is a horizontal synchronization signal separator, 6 is a phase comparator, and 7 is a reference horizontal synchronization signal generator. , 8 is a reference clock generator, 9 is a compensation amplifier,
10 is a drive amplifier, 11 is a spindle motor, 12 is A
D converter, 13 is a buffer memory, 14 is a DA converter,
15 is an optical pickup radial position sensor, 18 is a rotation speed multiplier, 17 is a frequency multiplier, 18 is a memory kick controller, 19.20 is an address counter, 21 is a track kick drive amplifier, and 22 is a CAV detector. be. Here, the constituent elements 1 to 11 are the same as those described in the conventional example.

The AD converter 12 converts the high frequency signal from the optical pickup 2 into a digital signal using the sampling clock that is the output of the frequency multiplier 17.

A reference clock, which is the output of the reference clock generator 8, is supplied to the frequency multiplier 17. The frequency of the reference clock can be determined by the band of the high frequency signal. In the buffer memory 13, this signal is written using the write signal and address signal output from the address counter 19. Address counter 2 to which the reference clock is supplied
Reading is performed using a read signal and an address signal which are outputs of 0. The DA converter 14 converts it into an analog signal using the reference clock. This output is supplied to a video signal demodulator 4 and an audio signal demodulator 3. An optical pickup radial position sensor (hereinafter abbreviated as calculator) 15 is a sensor that detects the radial position of the optical pickup,
For example, there is a potentiometer. The sensor 15 can detect the radial position. The output of this sensor 15 is input to a rotation speed magnification calculator (hereinafter abbreviated as a calculator) 16.

In the CAV detector 22, the 18th, 17th, 18th and 279°280.28th signals within the vertical retrace period of the video signal are detected.
When a CLV disc is detected from the signals on each of the first horizontal scanning lines, the calculator 16 calculates the magnification k, which is the ratio of the rotational angular velocity during normal CLV disc playback to the rotational angular velocity at the innermost circumference, as follows. Obtained using the principle shown below.

Now, the radius at the innermost circumference is R (am), the rotational angular velocity is W (1/S), and the radius at an arbitrary position is r
(cm), and the rotational angular velocity is w (1/s). Since the linear velocity is constant, R・W=r・W=constant linear velocity 1'-w/W=R/r Therefore, r=@R (However, if ≧1), then 1, ', =
r/R=W/w Note that when the CAV detector 22 detects a CAV disk, k=1. This value k is input to the frequency multiplier 17.

In this way, the write speed to the buffer memory 13 for the optical pickup 2 located at an arbitrary radial position is increased based on the radial position, while the read speed is kept constant. Then, no matter where the optical pickup 2 is located, the rotation speed of the spindle can be maintained at a value close to the speed at the innermost circumference due to the feedback loop.

By the way, since the writing speed to the buffer memory 13 is higher than the reading speed, if the playback time is long, data will overflow and the buffer memory 13 will not function. Therefore, a method is needed to properly perform the kick and input the signals separately. This is controlled by a memory kick controller 18.

This control method will be explained using FIG. 2.

FIG. 2 shows the time relationship between the input and output of the buffer memory 13 under the control of the memory kick controller 18. This example deals with the case where =3. This almost corresponds to the outermost circumference, and there are 6 fields on the - circumference. The horizontal axis shows the rotational time axis, and the vertical axis shows the radial time axis.

Enter the memory input field number■■■■■■■■■...
・, set the memory output field number (1) (2) (3)
(4) (5) l) (7) (8). In the first half of the first stage, (1) is output while rotating half a revolution while inputting ■■■. In the second half of the cycle and the first half of the second stage, no input is made, and (2) and (3) are output, respectively. During this time, perform a backward kick for one track. The period during which a backward kick is possible is shown by a thick solid line in the figure. In the second half of the second stage, (4) is output while inputting ■■■ and rotating half a revolution. In the first half and second half of the third row, do not input, but enter (5) and (
6) is output. During this time, perform a backward kick for one track. Similarly, for the fourth and subsequent stages, (7) is output while rotating half a revolution while inputting ■■■. In the second half, no input is made and (8) is output.

Next, a summary of this processing process is shown in FIG.

a is an integer, and represents the start phase of the memory output when the phase of -period is 2. b is a positive number, and represents the start phase of memory input when the phase of -period is 2. i is the number of fields that are consecutively input into the memory. In the first stage of FIG. 2, both memory input and output start phases are at the left end. At this time, both a and b are set to 0. Then, increase i sequentially from 1, (al1)k
Repeat until −(b+i)≧2.

Here, until the time difference between the ends of the same field between the memory output and the memory input becomes larger than the time required for one revolution, the AD converter 1 is used for every field, that is, for the time T/.
2. Input the output data into memory. However, T is one field period IB, which is 7 mS. Thereafter, a signal for kicking one track backward is sent to the track kick drive amplifier 21.

Return the next start phase of memory input by the amount of kick, and also change a+i-2 to a to reset the number of fields.
Then, b+i is set to b.

Furthermore, to prevent the value of al b from becoming too large, a≧
2 and b≧2, set a-2 to a, set b-2k to b, and reduce both by one rotation. After the memory input is completed, it is checked whether one rotation, that is, 2T has elapsed. When the elapsed time has elapsed, the activation signal of the memory kick controller 18 is sent to the address counter 19, and the output data of the AD converter 12 for the time T/ is input to the memory. The memory kick controller 18 having such a function can be easily realized with a microcomputer consisting of a CPU, RAM, ROM, etc.

With the above method, no matter where the optical pickup 2 is in the case of a CL disk, the spindle rotation speed can be maintained at a value close to the speed at the innermost circumference, and in this state, video, audio, etc. can be played. Even if there is an error in the magnification k or if the frequency multiplier can only take discrete values for k, the spindle rotation speed is 1800rl.
) is in the vicinity of m. When the optical pickup moves, k
The spindle rotation speed is slightly changed according to the value of . However, the rotational driving force required for this change is small (and the settling time for several rotations is also minute. Therefore, the time until the spindle servo is activated can be made equal to that of a CAV disk, and as a result, the search time is also shortened. It can be as short as a CAV disc.

Effects of the Invention As described above, the present invention has the following advantages in the reproduction of CLV discs.
An optical pickup radial position sensor, a rotation speed multiplier that calculates the ratio between the output of the sensor and the innermost radius, and a frequency multiplier that multiplies the frequency of the output of the reference clock generator by the value of the output of the calculator. a first address counter that updates the input address of the buffer memory that receives the high-frequency signal of the optical pickup output with the output of the multiplier; and the output address of the buffer memory that uses the output of the reference clock generator. and a memory kick controller that takes the output of the calculator as input and controls the input period of the buffer memory and the track kick, so that the optical pickup can be positioned at any position. Even if there is a spindle, the rotational speed of the spindle can be maintained at a value close to the speed at the innermost circumference, and video, audio, etc. can be reproduced in this state. Therefore, the time it takes for the spindle servo to start can be made equal to that of a CAV disk, and as a result, the search time can be shortened to the same level as that of a CAV disk.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an optical disc search device in an embodiment of the present invention, FIG. 2 is a time relationship diagram between input and output of the buffer memory, FIG. 3 is a processing process diagram of the memory kick controller, and FIG. FIG. 4 is a block diagram showing the configuration of a conventional optical disc search device. 12... AD converter, 13... Buffer memory, 14... DA converter, 15... Optical pickup, radial position sensor, 18... Rotation speed magnification calculator, 17... Frequency Multiplier, 18...Memory kick control! , 19.20...Address counter, 21...Track kick drive amplifier, 22
...CAV detector.

Claims (1)

[Scope of Claims] In reproducing a constant linear velocity optical disc, there is provided an optical pickup radial position sensor, a rotation speed multiplier calculator for calculating the ratio between the output of the sensor and the innermost radius, and the ratio of the output of the calculator to the innermost radius. a frequency multiplier that multiplies the frequency of the output of the reference clock generator by a value; a first address counter that updates an input address of a buffer memory that receives the RF signal output from the optical pickup with the output of the multiplier; a second address counter that updates the output address of the buffer memory with the output of the reference clock generator; and a memory kick that receives the output of the calculator and controls the input period of the buffer memory and track kick. An optical disc search device comprising a controller.