JPS5841446A - Optical information tracking system - Google Patents

Abstract

PURPOSE:To perform tracking with high accuracy, without being affected by recorded pits, by performing tracking over two guide tracks and recording information between the guide tracks. CONSTITUTION:An optical spot 6a from a light source (not shown) is positioned at the right side of a guide track 16b on an optical disc, an optical spot 6c is positioned at the left side of a guide track 16a and an optical spot 6b is positioned between the tracks 16a and 16b. In controlling the position of the optical spots so that the amount of reflected light of the spots 6a and 6c can be made just equal, the spot 6b is located at the center of the tracks 16a and 16b and in recording information with the spot 6b, a pit 17 is formed. When address information and synchronizing signals are desired to be recorded on the disc in advance, a pit 18 for recorded information is recorded between the guide tracks 16b and 16c.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information tracking method for an optical memory device such as an optical disk, and more particularly to an accurate information tracking method for an optical disk memory that records and reproduces information in real time.

Conventionally, in optical video discs, PCM optical discs, optical disc memory devices for recording and reproducing digital information, etc., tracking technology that tracks information tracks on the disc surface with an accuracy of approximately ±0.1 μm has become indispensable. There is. A typical method is to form three light spots on the disk surface, as shown in Figure 1A.
A method of tracking using this is known.

In FIG. 1A, a laser beam 2 emitted from a laser light source 1
becomes a parallel beam of light by the lens 3, is divided into three beams of 0th-order light and ±1st-order light by the diffraction grating 4, is reflected by the mirror 15, and is reflected by the diaphragm lens 5,
The light is focused on the disk 7 as three light spots 5a, 6b, and 6C. The three light spots 5a, 6b, 5C are located on the disk 7.
Track 1 on top track 16 as shown in FIG. 1B.
It is formed to have an inclination of θ with respect to the direction of 6.

The reflected light beam from the surface of the disk 7 is guided by a half mirror 8 onto photodetectors 10a, 10b and IOC.

At this time, the light spots 5a, 6b, and 6C are each detected by a photodetector 10a,
10b, detected corresponding to IOC. Photodetector 10b
The output from the amplifier 12 is led to a signal reproducing circuit. The output of the photodetector 10a and IOC is output from the differential amplifier 1.
After passing through the servo circuit 13, the signal υ is guided to the driver 14 of the mirror 15, and the mirror 15 is rotated in accordance with the track deviation current, thereby performing full tracking. That is, if the track 16 shifts to the right in FIG. 1A, the amount of reflected light from the light spot 6a decreases, and the amount of reflected light from the light spot 6C increases. The opposite is true if the track 16 shifts to the left. Constant amount of reflected light from 6a and 60, light detector 1
Mirror 15 so that the output from 0a and 100 are the same
All you have to do is control it. This method can perform stable tracking for optical video discs or optical PCM discs where information is formed on the tracks in advance, but it is possible to perform stable tracking for discs with information formed on the tracks in advance, such as optical video discs or optical PCM discs. Conventionally, optical disk memories that record and play back data have had major drawbacks. In other words, as shown in Figure 2, it is pre-guided on the disk.
In an optical disk memory, tracks 16a, 16b, 16C are formed, a recording film such as a thin metal film is formed on top of the tracks, and pits 17 corresponding to information are formed in this recording film. The light spot 6b records information, and the light spot 5a records information.

When trying to obtain a tracking signal using 6C, the light point 6
Since the light spot 6C is located in the area where information is not recorded and the light spot 6C is located in the edge area where information is recorded, the amount of reflected light is not equal even in a state where there is no track deviation. In addition, the non-uniformity varies greatly depending on the pattern of the recorded information or the arrangement pattern of the pits, which significantly deteriorates the accuracy of tracking.

The present invention solves the above-described drawbacks of conventional tracking and provides a highly accurate information tracking method.

In order to achieve this object, the present invention performs tracking along two guide tracks and records information between the guide tracks, thereby achieving high-precision tracking without being affected by recorded edge bits. It is something to be done.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 is a diagram illustrating an embodiment of the present invention.

In the figure, among the three light points 6a, 6b, and 6C, 6a is located on the right side of the guide track 16b, 6C is located on the left side of the adjacent guide track 16H on the right, and 6b is located on the left side of the guide track 16H adjacent to the right. It is located in the area between the guide tracks 16a, 16b.

Taking the difference in the amount of reflected light from 6a and 6c, when the track shifts to the right, the amount of reflected light from 6c increases and the amount of reflected light from 6a decreases. If the truck shifts to the left, the opposite will occur.

If the position of the light spot is controlled so that the amounts of reflected light from 6a and 6c are exactly equal, the light spot 6b will always be located at the center between the tracks. When information is recorded using 6b, a pit 17 is formed at the center between the tracks. Since the light spot 6c is placed on the guide track 16a, it does not overlap the pit 17 and there is no fluctuation in the light amount even if it is in the edge area where information is written.) When there is no rack shift, the light spot 6
It becomes an isophotic point with a.

Furthermore, when it is desired to record address information, synchronization signals, etc. on the disk surface in advance, as in the case of recording and reproducing digital information, the pits 18 of low recording information are placed on the guide track as shown in FIG. You should record it in the meantime. For creation and detection of the three light spots in FIG. 3, the same conventional device as shown in FIG. 1 may be used.

Regarding the guide track, there are no particular restrictions on its depth and width, but for example, the pitch is 2.5 μm.
m1 width approximately 0.4 to 0.8 μm, depth λ/4 to λ/8
Appropriate. Furthermore, information recording media are not particularly regulated, but for example,
e, Se, As.

It is preferable to use a material containing PB, In, etc. and having a thickness of about 100 to 500 Å.

As described above, by using the present invention, it is possible to provide a stable tracking method in an optical disk memory device that records and reproduces information in real time.

[Brief explanation of the drawing]

FIG. 1A and FIG. 1B are diagrams showing conventional information tracking methods,
FIG. 2 is a diagram for explaining its operation, and FIG. 3 is a diagram for explaining one embodiment of the present invention. '%I °Ca (Δ) I? 'l Kuzu 1 Figure (B) 6 A Z Snake/4Z 3 Figure/6b/1561-

Claims (1)

[Claims] 1. A laser light source, means for guiding a laser beam from the laser light source to a recording medium having a guide track, and means for detecting a reflected beam of the laser beam from the recording medium;
In the information tracking method in which information is tracked by a means for guiding the laser beam onto the guide track, the laser beam is diffracted in the means for guiding the laser beam onto the recording medium. and a means for converging the laser beam and the diffracted beam onto the recording medium as three light spots, and each of the three light spots has one light spot.
two guide tracks, an intermediate area between the guide tracks, and one other track adjacent to the intermediate area; An optical information tracking system characterized by comprising three of the above photodetectors for detection.