Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-03-24
2001-08-21
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044370, C369S044230
Reexamination Certificate
active
06278680
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an initial crystallization method of a recording medium recording an information with a recording beam (light energy beam) such as a laser light, etc., and a device thereof, and in particular, to an initial crystallization method of a recording medium such as a phase-change optical disk recording an information by the phase change between a crystalline state and an amorphous state with a recording beam such as a laser light, etc., and a device for the initial crystallization.
BACKGROUND OF THE INVENTION
In phase-change optical disks by conventional techniques, an information is written by irradiating a recording beam such as a laser light, etc., and erasing of the information is carried out by applying an overwrite by irradiating an erasing beam (erasing optical spot) such as a laser light, etc., onto the information-written portions.
An initial crystallization device for the phase-change optical disk carrying out a high-speed erase of an information performs an overwrite that by changing the power of one laser beam between two levels higher than a reading power level (the two levels are called an intermediate powder level and a high power level), while erasing the already written information, a new information is recorded.
In the phase-change optical disk, at least a part thereof is in a non-crystalline state or in a quasi-stable crystalline state direct after producing (called as-deposited state) the recording film by a vapor-deposition method or a sputtering method. In the phase-change optical disk in the as-deposited state, auto-focusing and tracking (i.e., a function of positioning a beam onto a recording track) are usually liable to become unstable owing to the low reflectivity thereof.
Accordingly, in the phase-change optical disk, an initial crystallization of previously crystallizing the whole surface of the above-described recording film is generally carried out.
In the known first initial crystallization method by a conventional technique, as described, for example, in JP-A-4-186530, a high-output laser beam of the output of from 1 to 2 W is formed into a flat elliptical light spot, a recording medium is irradiated with the light spot such that the lengthwise direction of the light spot coincides with the radius direction of the recording medium, and the initial crystallization is carried out by heating the crystal film of the recording medium with the light spot to a temperature range of from the crystallization temperature of the film to the melting point thereof.
Because in the conventional first initial crystallization method, to surely initially crystallize the crystal film of a recording medium, it is necessary the sending speed of the light spot is delayed and a same place of the crystal film is irradiated with the light spot several times, there are a disadvantage that a time of 1 minute or more is required for the initial recrystallization of the recording medium and a disadvantage that a non-uniformity of reflectivity occurs on the recording track by the non-uniformity of overlapping of the light spot and a jitter of a reproduced wave-form signal occurs.
Also, in a known second initial crystallization method by other conventional technique, as described in JP-A-62-271234, a light spot for the initial crystallization is divided into a welding spot for heating the crystal film of a recording medium and slow-cooling light spots for removing heat. Also, in the initial crystallization method, the above-described slow-cooling spots are in the form of two partially overlapped flat elliptical spots which are arranged in such a manner that the lengthwise directions of the flat elliptical spots coincide with the track direction of the recording medium, and the initial crystallization is carried out by the welding spot and the slow-cooling spots described above.
However, because in the conventional second initial crystallization method, flat elliptical slow-cooling spots extending to the track direction of the recording medium are used, there is a disadvantage that only one track can be initially crystallized by one rotation of a recording medium and a time of 1 minute or more is required for the initial crystallization of the whole surface of a recording medium.
Also, the present inventors previously filed Japanese Patent Application No. 8-262757 (Application date: Oct. 3, 1996) [JP-A-10-112065, Laid-open date: Apr. 28, 1998], in which, as a third initial crystallization method, a technique of carrying out the initial crystallization by flat elliptical light spots for initial crystallization formed by arranging laser beams of a small diameter from plural light sources in a partially overlapped state in the direction (the radius direction of an optical disk) rectangular to the track of the optical disk was proposed.
However, because in the third initial crystallization method, the flat elliptical light spots for initial crystallization formed by arranging laser beams of a small diameter from plural light sources in the direction rectangular to the track of an optical disk are used and the optical spots are moved to the radius direction of the optical disk per definite pitch, there is a disadvantage that a non-uniformity occurs in the reflectivity on the recording track by the non-uniformity by overlapping of the light spots, whereby a jitter of the reproduced wave-form signal occurs.
In addition, the conventional techniques on the second and third initial crystallization methods described above were indicated by the official actions when the present inventors previously filed other inventions regarding initial crystallization device to the Japanese Patent Office. The inventions filed by the present inventors are Patent Application No. 10-72367 wherein two circular light spots are almost overlapped with each other to unify the power distribution of the laser beams and Patent Application No. 10-93410 in which in addition to a circular light spot for initial crystallization, a circular light spot of focusing is employed. The explanations of these inventions are omitted because they have no direct relation with the content of the present invention.
SUMMARY OF THE INVENTION
The present invention has been made for solving the above-described disadvantages of the initial crystallization methods and device of optical disks by the conventional techniques. Furthermore, an object of this invention is to provide an initial crystallization method and device of an optical disk capable of surely initial-crystallizing the crystal film of a recording medium at a high speed without giving non-uniformity.
By the initial crystallization method and the initial crystallization device of the present invention for attaining the above-described object, the crystal film of a recording medium can be surely initial-crystallized at a high speed without giving non-uniformity by forming a light spot composed of at least two flat elliptical beam spots each having a long axis direction and a short axis direction, irradiating the rotating medium with the light spot such that the above-described long axis direction becomes other direction than the parallel direction to the track direction of the recording medium, wherein said beam spots each has at least two peaks of light intensity in the short axis direction, and the interval between said two peaks of light intensity is 10 &mgr;m or smaller but not smaller than 2 &mgr;m.
Also, in the present invention, the above-described light spot has a 1st beam spot first irradiating the rotating recording medium and a 2nd beam spot irradiating the rotating recording medium subsequent to the irradiation by the above-described 1st beam spot, and the light intensity of the 1st beam spot is higher than the light intensity of the 2nd beam spot.
Furthermore, in the present invention, the ratio of the light intensities of the above-described two beam spots of the light spot are changed, or the linear velocity of the track of the above-described recording medium is made constant, or the rotation speed of
Matsumoto Shin
Miyauchi Yasushi
Sahota Eiji
Soga Kazuhiro
Terao Motoyasu
Costellia Jeffrey L.
Edun Muhammad
Hitachi Computer Peripherals Co., Ltd.
Nixon & Peabody LLP
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