JPH01178131A - Optical disk - Google Patents

Abstract

PURPOSE:To improve the alignment accuracy by using an optical head for multi-beam, obtaining the servo signal of each track and averaging the servo signal. CONSTITUTION:A multi-beam optical head 1 is used, the servo signal is detected from a track other than the track recording and reproducing the data signal to extract a position error from each track of multi-beam. Then the sum of error signals is calculated and the value dividing the sum by the number of beams is used as the servo error signal, the signal is used to align the optical head. That is, if the number of beams of the optical head 1, is e.g., 5, an abnormal servo signal due to the flaw of a medium 20 is corrected by the servo signals reproduced by other four beams. Then the accuracy of positioning of the optical head 1 of flaw part in the medium 20 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk device having a servo mechanism that is resistant to medium defects.

[Conventional technology]

Conventionally, optical disk devices including magneto-optical disk devices use reflected light from a pre-group formed in advance on a substrate, generate a servo signal from this reflected light, and position an optical head.

[Problem that the invention seeks to solve]

As mentioned above, when a servo signal is extracted from a pregroup of one track, there is a problem in that the servo signal is greatly disturbed by a small defect in the optical disk medium, which significantly deteriorates the positioning accuracy of the optical head.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc device that improves the above-mentioned problems by extracting servo signals from a plurality of tracks.

[Means for solving problems]

In order to solve the above-mentioned problem, a multi-beam optical head is used to detect servo signals from tracks other than the track on which data signals are recorded and reproduced, and a position error signal is extracted from each track of the multi-beam.
The sum of these error signals is calculated, and the value obtained by dividing the sum by the number of beams is used as a servo error signal, and this signal is used to position the optical head.

[Effect]

As described above, abnormalities in servo signals can be reduced using a multi-beam optical head. For example, if the number of beams in the optical head is 5, an abnormal servo signal due to a media defect will be corrected by the servo signal reproduced by the other 4 beams, and the positioning accuracy of the head in the area of the media defect will be only 80%. Close to normal value.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a semiconductor laser array 2. Bolarized beam splitter 5. λ/4 plate 4. Wide field collimating lens 6, beam splitter 8° critical angle prism 9. Servo signal detector 10. The optical head 1 consisting of a condensing lens and the information signal detector array 7, four servo reproducing circuits 12, 13, 14 and 15, and the sum of the outputs of each of these servo reproducing circuits 12 to 15 are determined. A summation circuit 16 and a division circuit 17 that divides the output of the summation circuit 16 by 4.
, a servo control circuit 18 that controls the optical head using a servo signal output from the divider circuit 17 , an actuator 19 , an optical disk 20 , and a data reproducing circuit 11 .

The beams of the four channels of the semiconductor laser array 2 are respectively irradiated onto four tracks on the optical disk 20, and the reflected light is given to the servo signal detector 10 through the optical system, and the servo signal detector 10 detects the servo of each track. A signal (position error signal) is detected. The outputs of the four channels of the servo signal detector 10 are input to servo reproducing circuits 12, 13, 14 and 15, respectively. The servo signals output from the four-channel servo reproduction circuits 12 to 15 are summed by a summation circuit 16.
Further, this sum value is divided by 4 by a division circuit 17 to become a position error signal. Based on this position error signal, the servo control circuit 18 controls the actuator 19.
The position of the end 1 to the light is controlled. The data signal of the track thus positioned is reproduced by the data reproducing circuit 11 and output as data.

In the above embodiment, from the information signal detection array 7,
The data reproducing circuit 11 outputs only the data signal of a single track.
However, it is also possible to provide a plurality of data reproducing circuits 11 to simultaneously reproduce the data signals of a plurality of tracks.

〔Effect of the invention〕

As explained above, the present invention is applicable to multi-beams such as 4 beams.
Since a channel optical head is used to obtain 4-track servo signals and the servo signals are averaged, if there is a defect on one data track of the 4 channels, the other 3 tracks will have a defect. Corrected with 7 servo signals.

Therefore, the effect of improving the positioning accuracy of the optical head by 75% can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1... Optical head, 2... Semiconductor laser array, 3.
...Focusing lens, 4...λ/4 plate, 5...Bolarized beam splitter, 6...Wide field collimating lens, 7...Detector array for information signal, 8...Beam Splitter, 9... Critical angle prism, 10... Servo signal detector, 11... Data reproducing circuit, 12, 1
3.14.15... Servo reproduction circuit, 16... Addition circuit, 17... Division circuit, 18... Servo control circuit, 19... Actuator, 20... Optical disk.

Claims (1)

[Claims] In an optical disc device, an optical head using multi-beams, a servo signal reproducing circuit for reproducing servo signals reproduced from tracks corresponding to each of the multi-beams on the optical disc, and the sum of the outputs of the servo signal reproducing circuit are determined. A summation circuit, a division circuit that divides the output of this summation circuit by the number of multi-beams, a servo control circuit that controls the position of the optical head using the output of this division circuit, and a An optical disc device comprising: an actuator that drives an optical head; and a data reproducing circuit that outputs a data signal from at least one data track among multiple beams.