JPS61276132A - High-speed seeking system for optical disk - Google Patents

Abstract

PURPOSE:To shorten the time needed for the start through the end of a track follow-up action by performing both the adjusting and cross-tracking actions at a time for the rough seeking control. CONSTITUTION:The output of a fine seeking control driver 22 drives a fine shift mechanism 28 set on a rough shift mechanism 8 via switches 24 and 26 and according to the cross-track deviation 226, i.e., the value of a cross-track counter 12. Thus the mechanism 28 is shifted at a high speed up to the target of the mechanism 8. When a light spot reaches the target of the mechanism 8 and the deviation 226 is equal to zero, the connection between switches 7 and 24 is switched and both rough and fine follow-up control signals 238 and 240 of a track follow-up control driver 32 are applied to the mechanisms 8 and 28 respectively. Thus the track follow-up control is started. Then an information reading circuit reads out the track address of the place where the track follow-up control is started. Then the mechanism 28 is driven and shifted up to the target track by the shift amount 242 from the target track, the track jump control signal 244 and the track jump switching signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a seek method for positioning a recording/reproducing optical spot on a target track of an optical disc at high speed.

[Background of the invention]

The access time of an optical disk device is the sum of the seek time for moving a recording/reproducing light spot to a target track and the disk rotation waiting time.

Among these, the rotation waiting time is often determined based on the system transfer rate, etc., so in order to shorten the access time, it is necessary to shorten the seek time.

There are two methods for seek operations in optical disk devices. One method is to perform the seek in two stages: coarse seek and fine seek, and the other method is a method called cross track.
See publication.

The two-step seek method is as follows. That is,
An optical head for recording and reproducing is roughly positioned with respect to a track on an optical disk by a rough seek mechanism such as a linear motor. At this time, an optical linear scale or the like fixed to the base is used as a position detector. After the operation has been settled, a track following operation is performed once, and the track address at that location is read to determine the deviation from the target track. In order to correct the deviation from the target track, a precision seek mechanism such as a galvano mirror mounted on the optical head repeatedly jumps from track to track to move the light spot to the target track.

Looking at this operation in terms of seek time, as shown in Figure 1, the total seek time is: (1) the time required for coarse seek movement; (2) the positioning accuracy of coarse seek is 1 on a linear scale.
The settling time until it enters the pitch, ■The time it takes for the track following servo system to start and actually start tracking,
(2) The total time required for fine seek movement.In the case of high-speed seek, an integer time is longer than the time required for coarse seek movement, and it becomes a value that cannot be ignored.

Furthermore, if the rotational speed of the disk is high and the eccentricity of the disk becomes large, even if the track following servo system is activated, the track may fall off, and the time required until track following actually starts becomes a problem.

On the other hand, the cross-track method positions the optical spot on the target track by counting the number of pulses output from the track deviation signal each time it crosses a track, and in principle there is no seek error. In the case of high-speed seek, the header and data signals written on the disk are mixed into the track deviation signal, and the band overlaps with the band of the pulse output each time a track is crossed, resulting in incorrect counting of the number of tracks. occurs, making it impossible to correctly position the target track, making it unsuitable for high-speed movement.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve one or more of the problems and provide a stable and high-speed optical disk seek system.

[Summary of the invention]

In the two-step seek method, it takes time because it is necessary to wait until the settling of the coarse seek is completed, so it is sufficient to avoid affecting subsequent operations even if the wait is not required.

The distance traveled by the coarse seek mechanism after the time it switches from deceleration to stabilization until stabilization is extremely small compared to the required time, so the fine seek mechanism simultaneously performs cross-track seek on only the number of tracks corresponding to that distance. Move together. In this case, cross-track seeking is faster than rough seeking, but it is not so easy that the band of the header and data signals written on the disk overlaps with the band of the pulses output each time a track is crossed. Since the speed is not high, the signals can be separated and the number of tracks can be counted correctly, so the light spot can be moved at high speed to the original target of the coarse seek movement amount.

In addition, in the cross-track type seek using the precision seek mechanism, even if the disk is eccentric, it follows the movement of the disk, so actual track following can be started in a short time when the next track following servo system is activated.

Thereafter, the track address at that location is read, the deviation from the target track is determined, and the precision seek mechanism repeatedly jumps from track to track to move the light spot to the target track.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail using FIG.

A value N obtained by converting the number of moving tracks by the pitch of the linear scale 2 is written into the rough seek movement counter 4.

For example, the number of moving tracks M=10008.

In the case of linear scale pitch L = 32 μm and track pitch p = 1.6 μm, these are converted into integers and N = 500 is written in the coarse seek movement counter 4. At this time, the rounding error E is 0.4.

This rough seek movement counter 4 is counted up and down by up and down pulse signals 202 and 204 outputted at each pitch of the linear scale 2 according to the direction of movement.

The output 207 of the coarse seek control drive 6 corresponds to the coarse seek deviation 206 which is the value of the coarse seek movement amount counter 4.
is a coarse movement mechanism 8 using a linear motor via a switch 7.
to drive. At this time, the output 208 of the switch 7 is set to the seek side 207 by the seek/track following switching signal 234.
It is connected to the. When the coarse movement mechanism 8 moves and the coarse seek deviation 206 becomes smaller and reaches a predetermined value S, the coarse seek control drive 6 switches the coarse movement mechanism 8 from deceleration to stabilization. This function is based on the speed command characteristic included in the coarse seek control drive 6, and is a well-known method and is not the purpose of the present invention.

When the comparator 10 detects that the rough seek deviation 206 matches the value S, the output 210 causes the cross track number counter 12 to record the number of tracks corresponding to S at the pitch of the linear scale 2.

A value SL corrected for the rounding error E for the pitch of the linear scale is written.

For example, when the pitch L of linear scale 2 is 32 μm,
Track pitch of optical disc P = 1.6 μm, S = 4
The value for E=0.4 is written to the cross track number counter.

The track deviation signal 214 from the optical spot positioning sensor 14 and the total light intensity signal 216 pass through low-pass filters 16 and 18 to remove the influence of the header and data signals written on the disc, and become signals 218 and 220, which are then crossed. The signal is input to the track pulse generation circuit 20. The cross-track number counter 12 is counted up and down by up and down pulse signals 222 and 224 outputted from the cross-track pulse generation circuit 20 in accordance with the moving direction of the light spot with respect to the track.

In accordance with the cross-track deviation 226 which is the value of the cross-track number counter 12, the output 228 of the fine seek control drive 22 is transmitted via the switch 24 and the switch 26 to the fine movement mechanism 28 by the galvano mirror mounted on the coarse movement mechanism 8. The light spot is moved at high speed to the original target of the coarse movement mechanism 8. At this time, the output 230 of the switch 24 is connected to the seek side 228 by the seek/track following switching signal 234, and the output 232 of the switch 26 is connected to the 230 side by the track jump switching signal 236.

When the light spot reaches the original target of the coarse movement mechanism 8 and the cross-track deviation 226 becomes zero, the seek/track following switching signal 234, which is the output of the cross-track end determination circuit 30, disconnects the switch 7 and the switch 24. Then, the coarse follow-up control signal 238 and fine follow-up control signal 240 of the track follow-up control drive 32 are applied to the coarse movement mechanism 8 and the fine movement mechanism 28, respectively, and track follow control is started.

At this time, since the fine movement mechanism 28 has previously followed the eccentricity of the optical disk through cross-track control, it takes almost no time from the start of track following control until track following is actually performed.

After that, an information reading circuit (not shown) reads
The track address of this location is read out, and the amount of deviation 242 from the target track is calculated.

The fine movement mechanism 28 is driven by the track jump control signal 244, which is the output of the track jump control drive 34, and the track jump switching signal, and moves to the target track.

〔Effect of the invention〕

As described above, in the present invention, the settling time of the coarse seek and the time from start to completion of the track following operation by the fine movement mechanism, which took a long time in the seek time, can be reduced to By performing the cross-track operations simultaneously, the total seek time can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the seek time of an optical disc;
The figure is a block diagram illustrating one embodiment of the present invention. Agent: Patent Attorney Katsoo OgawaFigure 2

Claims (1)

[Claims] 1. In a seek method in which a seek operation for positioning a recording/reproducing optical spot on a target track of an optical disk is performed by a coarse seek operation by a coarse movement mechanism and a fine seek operation by a fine movement mechanism mounted on the coarse movement mechanism, When the seek mechanism arrives a minute amount before the target of the coarse seek operation, the fine movement mechanism moves to the position of the number of tracks corresponding to the minute amount by counting the number of tracks, and performs the coarse seek operation. Positions at the target, performs track following operation, reads the track address at that location, detects the deviation to the target track, and repeats the jump operation for each track using the precision movement mechanism according to the deviation, recording and reproducing on the target track. A high-speed seek method for optical discs that is characterized by positioning the optical spot for use.