JPH06295438A - Information recording and erasing method for optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve an erasing ratio and to make an SN ratio large at the time of over writing in an optical disk system making a phase transition type medium a recording medium. CONSTITUTION:An output control power source 2 and a power source 3 for controlling a radiation angle are connected to a semiconductor laser 1, two power sources are synchronized by means of a synchronizing circuit 4, the radiation angle for writing power is controlled to be large at the time of over writing and the radiation angle is controlled to be small at the time of an erasing power. By arranging the control direction of the radiation angle on a phase transition type medium 7 in the radial direction, an old recorded pit written by a beam in the radial direction is erased without incomplete erasure by thick erasure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information input / output device for recording / reproducing information on / from a phase change medium using light, and to a method for recording / erasing information.

[0002]

2. Description of the Related Art In recent years, as an overwritable optical information recording / reproducing device, a device using a phase change medium as an information recording medium and utilizing intensity modulation of a single laser beam has been actively researched and developed ( Proceedings of an International Symposium on Optical Memory (PROCEEDING OF AN)
INTERNATIONAL SYMPOSIUM O
N OPTICAL MEMORY), Vol. 28
(1989), pp. 141-145). The phase change medium records and reproduces information by utilizing the difference in reflectance between the crystalline state (erased state) and the amorphous state (recorded state) of the medium. FIG. 3 shows the configuration of the optical head section of this type of optical information recording / reproducing apparatus and the information recording / erasing method. The radiation beam emitted from the semiconductor laser 1 is collimated by the collimator lens 2 and collimated by the shaping prism 3 into a substantially circular beam. Then, after being circularly polarized by the quarter wavelength plate 5, it is condensed on the phase change optical disk 7 by the objective lens 6. Further, the reflected light enters the objective lens 6 again, becomes linearly polarized by the quarter-wave plate 5, is reflected by the deflecting beam splitter 4, is guided to the RF signal and error signal detecting optical system 8, and is focused and focused. A track error signal and an RF signal are obtained.

As an overwriting method, FIG.
As shown in (b), the output control circuit 9 modulates the optical output of the semiconductor laser. That is, the semiconductor laser is modulated by the two light outputs of the erasing level higher than the read level and the recording level higher than the erasing level in the portion for overwriting. At this time, the portion exposed to the erasing level light is crystallized (erased state) after cooling, and the portion exposed to the recording level light is amorphized (cooled state) after cooling.
In this way, overwriting can be performed with only a single laser beam.

[0004]

However, in the case of the conventional overwrite method, the beam spot size does not change even if the light intensity of the semiconductor laser is modulated. At this time, a problem as shown in FIG. 4 occurs. That is, FIG.
The recording threshold value shown in (b) and the erasing threshold value shown in FIG. 4 (c) are values determined by the chemical properties of the recording medium. The possible range is also defined. At this time, if the recording level for stable recording is set, the recording width w ₃ becomes larger than the erasing width w ₄ , and as shown in FIG. Recording point 1
As 2 is written, a part of the old recording point 14 disappears and remains as the remaining 15, which causes a deterioration of the error rate.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide an information recording / erasing method for an optical information recording / reproducing apparatus, which has no residual data and has a good error rate.

[0006]

According to the present invention, a phase change medium is used as a recording medium, light emitted from a laser light source is condensed as a minute spot on the phase change medium, and reflected light from this condensing point is collected. In an optical information recording / reproducing apparatus having an optical system for guiding a light detector to a photodetector, a circuit for controlling a light output and a circuit for controlling a radiation angle are connected to a laser light source, and the two circuits are controlled by a synchronous circuit. Then, the emission angle of the light beam emitted from the laser light source is modulated in synchronization with the intensity modulation of the laser light source corresponding to erasing / writing of recording.

[0007]

The principle of the present invention will be described with reference to FIG. When an optical system of a collimator lens and an objective lens under the same conditions is used, the larger the emission angle of the semiconductor laser, the smaller the focused beam diameter. Therefore, in the present invention, the radiation angle is modulated in synchronization with the optical output modulation. That is, the irradiation angle is increased to reduce the beam diameter on the optical disk during writing power irradiation, and the irradiation angle is decreased to increase the beam diameter during erasing power irradiation. By arranging the modulation direction of the radiation angle in the radial direction, the recording width w ₁ (see FIG.
(B) becomes smaller than the erase width w ₂ (FIG. 2 (c)),
As shown in FIG. 2A, all the old recording points 14 which have been made amorphous can be overwritten without disappearing.

[0008]

1 is a diagram showing an optical head portion and an information recording / erasing method in an optical information recording / reproducing apparatus showing an embodiment of the present invention.

In this optical head, the radiation beam emitted from the semiconductor laser 1 is collimated by the collimator lens 2 and is collimated by the shaping prism 3 into a substantially circular collimated beam. It passes through the polarization beam splitter 4, passes through the quarter-wave plate 5, and is focused on the recording medium 7 by the objective lens 6. The light reflected by the recording medium 7 passes through the objective lens 7 and the quarter-wave plate 5 again, and is guided to the RF signal and error signal detection optical system 8 by the deflecting beam splitter 4 to focus and track error signals and RF. The signal is obtained. At this time, the output and the radiation angle of the semiconductor laser 1 are independently controlled by the output control circuit 9 and the radiation angle control circuit 10, and
The output control circuit 9 and the radiation angle control circuit 10 include a synchronization circuit 11
It is synchronized with. In the semiconductor laser 1, the current for controlling the radiation angle is made to flow independently of the current for controlling the output, whereby the equivalent refractive index in the direction parallel to the joint surface changes, and the radiation angle changes. With these control circuits,
By synchronizing the output and the radiation angle, as shown in FIG. 1 (b), the radiation angle is increased and the beam diameter on the optical disk is reduced during writing power irradiation, and the emission angle is reduced during erasing power irradiation over the optical disk. By increasing the beam diameter of, it is possible to realize overwriting with a good error rate without erasure due to the principle described in the action section.

In this embodiment, an optical system using a shaping prism, a deflecting beam splitter, a quarter wavelength plate, etc. is shown. However, in the case of a semiconductor laser having a small aspect ratio, the shaping prism may be omitted, It is possible to use an optical system that can be used in an apparatus using a phase change medium, such as omitting the quarter-wave plate and using a half mirror instead of the deflecting beam splitter.

[0011]

As described above, according to the information recording / erasing method of the optical information recording / reproducing apparatus of the present invention, in the optical information recording / reproducing apparatus using the phase change recording medium,
Overwriting with a good error rate can be performed without the remaining unerased old recording pits.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is an explanatory diagram showing an optical head portion and an information recording / erasing method of a conventional optical information recording / reproducing apparatus.

FIG. 4 is an explanatory diagram showing a problem of an information recording / erasing method of a conventional optical information recording / reproducing apparatus.

[Figure 5]

[Explanation of symbols]

 1 Semiconductor Laser 2 Collimating Lens 3 Shaping Prism 4 Deflection Beam Splitter 5 1/4 Wave Plate 6 Objective Lens 7 Phase Change Optical Disk 8 RF Signal and Error Signal Detection Optical System 9 Output Control Circuit 10 Radiation Angle Control Circuit 11 Synchronous Circuit 12 Amorphization Recording point 13 Crystallization erasure part 14 Old recording point 15 Remaining erased

[Procedure amendment]

[Submission date] January 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is an explanatory diagram showing an optical head portion and an information recording / erasing method of a conventional optical information recording / reproducing apparatus.

FIG. 4 is an explanatory diagram showing a problem of information recording / erasing in a conventional optical information recording / reproducing apparatus.

Claims (1)

[Claims] 1. An optical system in which a phase change medium is used as a recording medium, light emitted from a laser light source is condensed as a minute spot on the phase change medium, and reflected light from this condensing point is guided to a detector. In the information recording / erasing method of the optical information recording / reproducing apparatus having, a circuit for controlling an optical output and a circuit for controlling an emission angle are connected to a laser light source, and the two circuits are controlled by a synchronous circuit to perform recording. An image recording / erasing method for an optical information recording / reproducing apparatus, characterized in that the emission angle of a light beam emitted from the laser light source is modulated in synchronization with intensity modulation of a laser light source corresponding to erasing / writing.