JPS61280031A - Seek method for optical disk device and optical disk 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 Application of the Invention] The present invention relates to a theta method of an optical spot for recording and reproduction in an optical disc device.

[Background of the invention]

Since a seek operation in an optical disk device requires a wide movement range and highly accurate positioning, it is performed in two stages: a coarse seek and a fine seek, as described below. First, an optical head for recording and reproducing is approximately positioned with respect to a track on an optical disk by a coarse movement 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 stabilized, the track following operation is performed once, and
Read the track address at that location and find the deviation from the target track. In order to correct the deviation from the target track, a precision movement mechanism such as a galvano mirror mounted on the optical head is driven, and each time the optical spot passes the track, the pulse output from the track deviation error signal and the total reflected light amount signal is Count the number and position the light spot on the target track. This method of precision seeking is called the cross-track method. In this case, it is necessary to pulse the track misalignment error signal and the total reflected light amount signal, but the total reflected light amount signal may vary in the radial direction,
If the output of the recording/reproducing laser changes or the optical disc is replaced, the AC level and D of the total reflected light amount signal will change.
Since the C level changes together, the value of the slice level for pulsing becomes inappropriate, the number of tracks cannot be counted correctly, and the light spot cannot be correctly positioned on the target track.

Note that related devices of this type include, for example, Japanese Patent Application Laid-Open No. 58-91536.

[Purpose of the invention]

The purpose of the present invention is to solve one or more problems, and to provide a stable optical disk even when the reflectance of the optical disk changes in the radial direction, the output of the recording/reproducing laser changes, or the optical disk is replaced. An object of the present invention is to provide a highly reliable optical disk seek method.

[Summary of the invention]

In the case of two-step positioning with coarse seek and fine seek, the amount of movement due to cross-tracking is small, so in order to correctly pulse the total reflected light amount signal, it is necessary to slice the total reflected light amount signal in the vicinity of performing cross-tracking. All you need to know is your level. The values of the AC level and DC level of the total reflected light amount signal, which are used to determine the slice level of the total reflected light amount signal, cannot be observed unless the light spot has completely read the track.
This is not required in normal track following conditions. Therefore,
These values are the AC level of the total reflected light amount signal near the end of rough positioning by the coarse movement mechanism.

A feature of the present invention is that it is determined based on the value of the DC level.

[Embodiments of the invention]

Among the embodiments of the present invention, a method for determining the slice level of the total reflected light amount signal will be described in detail with reference to FIG.

The low-pass total reflected light intensity signal 100 from the optical spot positioning sensor, which has been passed through a low-pass filter, has a varying DC level E.
1 and AC level E2, and is output in the form of a sine wave every time the light spot crosses the track. This low-frequency total reflected light amount signal 10 near the completion of the coarse seek movement
0, an upper envelope signal 102 and a lower envelope signal 104 are generated, and an upper envelope signal 1
The minimum value E3 of 02 and the maximum value E4 of the lower envelope signal 104 are determined. The slice level of the total reflected light amount signal is determined as the intermediate value E5 between the minimum value E3 and the maximum value E4.

The entire embodiment of the present invention will be explained 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. Number of moving tracks M = 10008, pitch of scale 2 = 32μ
m, and when the track pitch of the optical disc is p=1.6 μm, the exact amount of movement is N=500 is written in the rough seek movement amount counter 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.

According to the coarse seek deviation 206 which is the value of the coarse seek movement amount count 4, the output 208 of the coarse seek control drive 6 is
The coarse movement mechanism 8 is driven by a beam near motor. Track deviation error signal 2 from optical spot positioning sensor 10
10 and the total reflected light amount signal 212 pass through a low-pass filter 12.14 for removing the influence of the header and data signals written on the disc, and produce a low-pass track deviation error signal 2.
14 and a low frequency total reflected light amount signal of 100. An upper envelope signal 1 is generated from the low-frequency total reflected light amount signal 100 by an upper envelope circuit 16 and a lower envelope circuit 18.
02 and a lower envelope signal 104 are produced.

The coarse movement mechanism 8 moves to near the coarse seek target, and the coarse seek deviation 206 reaches predetermined values α1 and α2 (
The window comparator 2 came between α1〉α2).
0 is detected, and its output 216 operates the minimum value circuit 22 and maximum value circuit 24, and the minimum value E3 of the upper envelope signal and the maximum value E4 of the lower envelope signal 104 are determined, and the intermediate value circuit 26 Rough seek deviation 206 where the intermediate value E5 between the minimum value E3 and the maximum value E4, which is the slice level of the total reflected light amount signal, is determined by
becomes less than the value α2 and the end determination circuit 28 determines that the movement of the coarse movement mechanism 8 has been completed, the output 218 is sent to a higher level control device (not shown) and is processed by a track following control device (not shown). Once the light spot is track-followed, the track address at that location is read. Then, the higher-level control device calculates the deviation 220 from the target track and writes it into the cross-track number counter 30, and the switch 40 is closed by a signal 221 from the higher-level control device to start the cross-track operation.

The low-frequency track deviation error signal 214 is pulsed at O level by the comparator 32 to become a signal 222, and the low-frequency total reflected light amount signal 100 is pulsed by the comparator 34 to a slice level E5 to become a signal 224, both of which are cross-track. The signal is input to the pulse generation circuit 36. The cross-track number counter 30 is counted up and down by up and down pulse signals 226 and 228 output from the cross-track pulse generation circuit 36 in accordance with the moving direction of the light spot with respect to the track. This cross-track pulse generation circuit 36
A specific method of outputting the down pulse signals 226 and 228 is detailed in Japanese Patent Laid-Open No. 58-91536.

The precision seek control drive 38
The output 232 drives a fine movement mechanism 42 using a galvano mirror mounted on the coarse movement mechanism 8 via a switch 40 to move the light spot to the target address with high precision.

〔Effect of the invention〕

As described above, according to the present invention, even if the reflectance of the optical disc changes in the radial direction, the output of the recording/reproducing laser changes, or the optical disc is replaced,
It is possible to perform stable and reliable optical disc seek to the target track.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a method of determining a slice level of a total reflected light amount signal in an embodiment of the present invention. FIG. 2 is a diagram illustrating the entire embodiment of the present invention. ′! J10

Claims (1)

[Claims] The optical head for recording and reproduction is approximately positioned with respect to the track on the optical disk by a coarse movement mechanism, and then a fine movement mechanism mounted on the optical head is driven to generate a track deviation error signal and a track deviation error signal each time it crosses a track. In the optical disk seek method that counts the number of pulses output from the total reflected light amount signal and positions the optical spot on the target track, the slice level value for pulsing the total reflected light amount signal is roughly determined by the coarse movement mechanism. An optical disk seek method characterized by determining the AC level and DC level of the total reflected light amount signal near the end of positioning.