JPS6129423A - Recording and reproducing method of optical recording medium - Google Patents

Abstract

PURPOSE:To double the recording density with no increase of the crosstalk level by recording and reproducing information at the recess and projection parts of a groove-shaped track with different method respectively. CONSTITUTION:A reflection factor changing type reproduction is carried out by means of an optical system shown by a figure (b). The circuit connection to a tracking error signal detector is switched to decide whether a laser light beam 8 is led to a recess part 5 or a projection part 4 of a track. While in a production mode of a photomagnetic recording/reproducing type, an optical system of a figure (a) is used to delete differentially the information of the reflection factor changing type with no rotation of a polarizing surface. Thus only the information of the photomagnetic recording/reproducing type is extracted. Thus it is possible to double the recording density just with a conventional crosstalk level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for recording and reproducing information on an optical recording medium using light.

Conventional Structures and Problems With optical recording media, focusing and tracking control are essential for non-contact, high-density recording. Many optical recording media already have some form of tracking guide, allowing accurate tracking control. In this case, either the concave or convex portion of the track is used for recording, and the other serves to separate two adjacent tracks so that recording and reproduction can be performed independently.

However, since the light beam cannot be focused below that wavelength, as recording density increases, the track pitch becomes shorter to the order of the wavelength of the laser being used. There is a drawback that the recording density is controlled because information on adjacent tracks is mixed in (hereinafter referred to as crosstalk) and the reproduced signal quality is degraded.

Additionally, as shown in Figure 1, attempts have been made to form a tracking guide with a V-shaped groove and use each slope of the groove as a recording track to reduce crosstalk and increase recording density. However, tracking information is required at the peaks and valleys of the groove1, and the optical detection system also requires a driver.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks and aims at high-density writing.

Structure of the Invention The present invention doubles the recording density without interfering with each other by recording and reproducing information using different methods in the concave and convex portions of tracks formed in advance in the shape of grooves on a substrate. It can be said that

DESCRIPTION OF THE EMBODIMENTS A recording and reproducing method for an optical recording medium according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an enlarged view of the periphery of a reflective optical disk. In Fig. 2, 1 is an optical disk substrate, 2 is a recording layer, 3 is a protective layer, and 4 is a width of approximately 0.8 μm.
a convex portion of the track in which the first recording/reproducing method is used in m;
Reference numeral 5 indicates a concave portion of the track which has a width of about 0.8 μm and is used in the second recording/reproducing method, 6 indicates information recorded on the protruding portion 4 of the track by the first recording/reproducing method, and 7 indicates a recessed portion 5 of the track.
Information recorded by the second recording/reproducing method is shown in FIG. 8, and 8 is a laser beam.

In this example, an amorphous GdTbFe single layer film is used as the recording layer 2, and thermomagnetic recording is performed as the first recording/reproducing method.
A magneto-optical recording and reproducing method that performs magneto-optical reproducing is used as a second recording and reproducing method, which is a recording and reproducing method that uses reflectance change due to crystallization of an amorphous material (hereinafter referred to as reflectance change method).

Figures 3a and 3b show magneto-optical and reflectance-changing reproduction optical systems, respectively; 9 is a laser, 10 is a beam shaping lens, 11 is a half mirror, 112 is a condensing lens, 13 is an optical disk, and 14 is a wall glass. 15 is a two-split photodiode, 16 is a differential amplifier, 17 is a photodiode, and 18 is an amplifier.

Recording on the track portion using magneto-optical recording/reproducing method uses a semiconductor laser at a temperature higher than one Curie temperature (160°C or higher).
The temperature of the recording layer is raised to a temperature at which the amorphous recording layer does not crystallize, and the recording is performed in a recording magnetic field. Reproduction using the magneto-optical recording and reproducing method is performed using the optical system shown in FIG. 3a.

Recording using the reflectance change method on the separation strip of a track uses a He-Ns laser, which has a narrower beam diameter than a semiconductor laser. Increase the temperature and perform without a recording magnetic field. Reproduction using the reflectance change method is performed using the optical system shown in FIG.

Here, whether the laser beam 8 is guided to the concave portion 5 of the track or the convex portion 4 of the track can be selected simply by switching the circuit connection to the tracking error signal detector.

Further, although some information from other methods is mixed into the re-time detector of each method, the influence of this can be almost eliminated. That is, during reproduction using the magneto-optical recording and reproducing method, the optical system shown in FIG. When reproducing the reflectance change method, only the reflectance change method information is extracted using the optical system shown in FIG. 3, which does not detect rotation of the plane of polarization.

As described above, according to this embodiment, the recording density can be doubled with the same crosstalk level as the conventional one.

Effects of the Invention By using the optical recording medium of the present invention, in high-density recording, the recording density can be doubled while suppressing the crosstalk level to the same level as before.

An enlarged view of the periphery of a reflective optical disk for explaining the recording and reproducing method of an optical recording medium in an embodiment of the present invention, No. 3
Figures a and b are configuration diagrams of a reproducing optical system of the magneto-optical recording and reproducing method 2 reflectance change method.

DESCRIPTION OF SYMBOLS 1... Optical disk substrate, 2... Recording layer, 3... Protective layer, 4... Protrusion of track, 6... Concave portion of the track, 6... Information recorded in the convex portion of the track by the first recording/reproducing method, 7... Information recorded in the concave portion of the track by the second recording/reproducing method , 8...Laser light beam, 9...Laser, 10...Beam shaping lens, 11...Half mirror 112...
... Condensing lens, 13 ... Optical disk 1, 1
4...Wollaston prism, 15...
・Two-split photodiode, 16...Differential amplifier, 17...Photodiode, 18...
··amplifier.

Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) A recording and reproducing method for an optical recording medium in which information is recorded and reproduced in different ways on the concave portions and convex portions of a track formed in a groove shape. (2) A recording and reproducing method for an optical recording medium according to claim 1, wherein a magneto-optical recording and reproducing method is used for recording information on either the concave portion or the convex portion of the track. (3) A recording and reproducing method for an optical recording medium according to claim 1, which uses a recording and reproducing method that utilizes an irreversible process for recording information on either the concave portion or the convex portion of the track.