JP2539362B2 - Seek method of optical disk - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seek method for positioning a recording / reproducing light spot on a target track of an optical disc at high speed.

[Background of the Invention]

The access time of the optical disk device is the sum of the seek time for moving the recording / reproducing light spot to the target track and the rotation waiting time of the disk. Of these, the rotation waiting time is often determined from the transportation rate of the system, etc., and therefore, the seek time must be shortened in order to shorten the access time.

There are two methods for the seek operation in the optical disk device. One method is divided into two steps, coarse seek and fine seek, and the other is a method called cross track. See, for example, JP-A-58-91536.

The two-step seek method is as follows. That is, an optical head for recording / reproducing is used for a track on an optical disc by a coarse seek mechanism such as a linear motor.
Position roughly. At this time, an optical linear scale or the like fixed to the base is used as the position detector. After the settling of the operation is completed, the track following operation is once performed, the track address at that location is read, and the deviation from the target track is obtained. In order to correct the deviation from the target track, a precise seek mechanism such as a galvano mirror mounted on the optical head repeatedly jumps each track,
Move the light spot to the target track.

When this operation is viewed from the perspective of seek time, as shown in FIG. 1, the total seek time is the time required to move the rough seek, and the positioning accuracy of the rough seek is 1 of the linear scale.
Settling time until entering the pitch, time until the track following servo system starts and track following actually starts,
This is the sum of the time required for the movement of the fine seek, but in the case of the high speed seek, the settling time becomes longer than the time required for the movement of the rough seek, which is a non-negligible value. Further, when the disk rotation speed is high and the eccentricity of the disk is large, a track deviation occurs even if the track following servo system is activated, and the time until the track following actually starts becomes a problem.

On the other hand, the cross-track method counts the number of pulses output from the track deviation signal every time the track is crossed, and positions the light spot on the target track. In principle, there is no seek error. In the case of high speed seek, the header and data signals written on the disc are
Since it mixes with the track deviation signal and its band overlaps with the band of the pulse that is output every time the track is crossed, the number of tracks is erroneously counted, and the target track cannot be positioned correctly. Is not suitable.

[Object of the Invention]

An object of the present invention is to solve the above problems and provide a stable and high-speed optical disk seek method.

[Outline of Invention]

In the two-step seek method, it takes time because it is necessary to wait until the rough seek settling is completed, so it is sufficient to avoid affecting the subsequent operations without waiting.

After the time when the coarse seek mechanism switches from deceleration to settling,
Since the distance to settle is very small for the required time, only the number of tracks corresponding to the distance is moved simultaneously using the cross track type seek by the fine seek mechanism. The seek by cross track in this case is faster than the movement by coarse seek, but it is so fast that the band of the header or data signal written on the disk and the band of the pulse output every time the track is crossed overlap. However, since the signals can be separated and the number of tracks is correctly counted, the light spot can be moved to the original target of the coarse seek mechanism at high speed.

Further, in the cross-track type seek by the fine seek mechanism, even if the disk has an eccentricity, it follows the movement, so that the actual track following can be started in a short time when the next track following servo system is activated.

After that, the track address at this location is read, the shift from the target track is obtained, and the fine seek mechanism repeats jumps for each track to move the light spot to the target track.

Example of Invention

 An embodiment of the present invention will be described in detail with reference to FIG.

A value N obtained by converting the number of moving tracks at the pitch of the linear scale 2 is written in the coarse seek moving amount counter 4.

For example, when the number of moving tracks M = 10008, the linear scale pitch L = 32 μm, and the track pitch p = 1.6 μm, Therefore, it is converted into an integer and N = 500 is written in the coarse seek movement amount counter 4. At this time, the rounding error E is 0.4.

This coarse seek movement amount counter 4 is a linear scale 2
Is counted up and down by the up and down pulse signals 202 and 204 output according to the moving direction for each pitch.

According to the coarse seek deviation 206 which is the value of the coarse seek movement amount counter 4, the output 207 of the coarse seek control drive 6 drives the coarse moving mechanism 8 by the linear motor via the switch 7. At this time, the output 208 of the switch 7 is connected to the seek side 207 by the seek / track follow-up switching signal 234. When the coarse movement mechanism 8 moves to reduce the coarse seek deviation 206 to a predetermined value S, the coarse seek control drive 6 switches the coarse movement mechanism 8 from deceleration to settling. This function is based on the speed command characteristic included in the coarse seek control drive 6 and is a method well known in the related art and is not the object of the present invention.

Further, when the comparator 10 detects that the coarse seek deviation 206 matches the value S, the output 210 thereof causes the cross track number counter 12 to indicate the number of tracks corresponding to S at the pitch of the linear scale 2 and the linear scale. A value SL in which the rounding error E for the pitch is corrected is written.

For example, if the pitch L of the linear scale 2 is 32 μm,
Track pitch of optical disk p = 1.6 μm, S = 4 E = 0.
In case of 4 The value of is written into the cross-track number counter.

Track deviation signal from optical spot positioning sensor 14
214 and the total light amount signal 216 are low-pass filters 16 and 18 for removing the influence of the header and data signals written on the disc.
And become signals 218 and 220, which are input to the cross track pulse generation circuit 20. The up / down pulse signals 222 and 224 output from the cross track pulse generation circuit 20 according to the moving direction of the light spot with respect to the track causes the cross track number counter 12 to count up and down.

Output 2 of the precise seek control drive 22 according to the cross track deviation 226 which is the value of the cross track number counter 12.
28 drives the fine movement mechanism 28 by the galvano-mila mounted on the coarse movement mechanism 8 via the switch 24 and the switch 26,
The light spot is moved at high speed to the original target of the coarse moving mechanism 8. At this time, the output 230 of the switch 24 is connected to the seek side 228 by the seek / track follow-up 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 follow-up switching signal output from the cross-track end determination circuit 30.
The connection between switch 7 and switch 24 is switched by 234, and the coarse follow-up control signal of the track follow-up control drive 32 is output.
238 and the fine tracking control signal 240 are applied to the coarse moving mechanism 8 and the fine moving mechanism 28, respectively, and the track following control is started.

At this time, since the fine movement mechanism 28 follows the eccentricity of the optical disk by the cross track control in advance, it takes almost no time from the start of the track following control to the actual track following.

Thereafter, an information reading circuit (not shown) reads the track address at this location, calculates the deviation amount 242 from the target track, and calculates the track jump control signal 24 output from the track jump control drive 34.
4 and the precise movement mechanism 2 by the track jump switching signal
8 is driven and moves to the target track.

〔The invention's effect〕

As described above, in the present invention, the settling time of the rough seek and the time from the start to the completion of the track following operation by the settling movement mechanism, which takes a long time in the seek time, are set to the settling operation of the coarse seek and the fine seek By simultaneously performing the cross-track operation of, the seek time can be extremely shortened, and the overall seek time can be greatly shortened.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the seek time of an optical disc, and FIG.
FIG. 1 is a block diagram illustrating an embodiment of the present invention.

Claims (2)

(57) [Claims] 1. A seek method for performing a seek operation for positioning a light spot on a target track on an optical disk by a rough seek operation by a coarse moving mechanism and a fine seek operation by a fine moving mechanism mounted on the rough moving mechanism, During the settling operation when the coarse moving mechanism refers to the linear scale to position the light spot in the vicinity of the target track, the fine moving mechanism causes the light spot to move in parallel with the coarse seek operation by the coarse moving mechanism. A seek method for an optical disk, wherein the optical spot is moved to the target track while counting the number of tracks based on a pulse detected when the track is crossed. 2. A method of seeking an optical disk according to claim 1, wherein a linear motor is used as the coarse moving mechanism and a carbano mirror is used as the precise moving mechanism.