Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Reexamination Certificate
2000-09-25
2002-11-26
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
C369S053100, C369S059120
Reexamination Certificate
active
06487152
ABSTRACT:
Japanese Patent Application No. 11-273061 filed Sep. 27, 1999 is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of recording information in a phase-change recording medium comprising a phase-change material in a recording layer thereof, which phase-change material is capable of recording information in a rewritable manner and reproducing recorded information by being subjected to phase change at the irradiation with a laser beam. The present invention also relates to a phase-change recording medium produced by the method of recording information of the present invention, such as a rewritable compact disk (CD-RW), and other recording media for use in optical memory appliances.
2. Discussion of Background
As described in Japanese Laid-Open Patent Application 63-29336, there is conventionally known a method of recording information signals in an optical disk, using an optical disk recording apparatus, by causing a laser beam to scan the optical disk in such a manner that the surface of the optical disk is irradiated with a light spot of the laser beam, for instance, with the light spot of the laser beam being subjected to power modulation with information signals.
Furthermore, there is conventionally known a method of determining or setting optimum recording conditions such as recording (light) power, and the pulse width of recording (light) power by reproducing the information signals recorded in the optical disk and monitoring the reflection amplitudes of the reproduced signals or the length of a recording mark.
Various recording compensation methods have been disclosed for improving the quality of recording signals in the phase-change recording.
For example, in Japanese Laid-Open Patent Application 63-26632, as an effective method for improving the quality of recording signals, there is disclosed a method of recording long amorphous marks, using a pulse train in a PWM (pulse width modulation) method by use of a recording film with a high crystallization speed.
Furthermore, in Japanese Laid-Open Patent Application 63-266633 and U.S. Pat. No. 5,150,352, there is disclosed a method of controlling the fluctuations of the positions of the edge portions of a recording mark for marking an improvement in the reduction of the jitters by increasing the laser energy at the leading edge and the tail-end edge of a pulse train, or by lengthening laser irradiation time.
Orange Book Part III (ver 2.0) provides the standard of CD-RW for line recording at one to quadruple speeds (1.2 to 5.6 m/s). Such low line speeds take a long time for recording, so that there has been a demand for a rewritable compact disk capable of performing rewritable recording at higher speed.
Due to the above disclosed prior art, phase-change disks and optical disk drives having excellent performance have been made available. However, there has been desired further improvement on the technology for producing the optical disk and optical disk drive in order to obtain an optical disk which is securely compatible with CD-R(recordable), and an optical disk drive for use with the optical disk, which have completely satisfactory performance in overall aspects thereof, and which can create a new market of optical disk and optical disk drive.
By use of the conventional methods, however, it is extremely difficult to find most appropriate recording conditions without fail even if information signals are recorded in the conventional optical information recording media by a conventional, ass-produced optical information recording and reproducing apparatus for the following reasons:
In the above-mentioned conventional methods, there is known a method for determining a most appropriate recording power for each optical information recording and reproduction apparatus by monitoring the amplitudes of recording signals, that is, the difference between a signal level in an unrecorded portion and a signal level in a recorded portion of the recording medium, which amplitude constitutes a representative reproduction signal in the optical information recording medium.
However, it is known that the value of the amplitude of the recording signal is varied not only by the recording power, but also by the wavelength of the LD (laser diode) of the recording and reproduction apparatus, the numerical aperture of an optical pickup, the rim intensity (the intensity distribution of a laser beam which enters a condenser lens), the size or the shape of a light spot, and the pollution of the optical system with time, so that the optimum recording laser power and the quality of recorded signals are largely varied. Therefore, the conventional optical drives for the optical disk recording apparatus have been designed so as to be made compatible with different types of optical disks produced by different manufacturers thereof.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a method of recording information in a phase-change recording medium, which is free of the above-mentioned shortcomings of the conventional recording methods, and has the following features: The method includes a test recording step and is capable of attaining high recording performance without resort to a particularly selected combination of a rewritable compact disk and a compact disk drive, and also is capable of significantly improving the initial characteristics and overwrite characteristics of the rewritable compact disks and compact disk drives used therewith. The method is also suitable for performing recording and erasing of information, using a compact disk with a rotation speed in a wide range of 1.2 m/s to 22.4 m/s in terms of line speed.
A second object of the present invention is to provide a phase-change recording medium which is produced by the above-mentioned recording method.
The first object of the present invention can be achieved by a method of recording information in a phase-change recording medium comprising the steps of:
conducting a test recording with the application of a laser beam to the phase-change recording medium, the laser beam comprising a plurality of pulse trains, each pulse train comprising alternately (a) a comb-shaped pulse train portion and (b) a flat pulse-free portion, with a duty ratio of the comb-shaped pulse train portion being changed, thereby recording a plurality of signals in the recording medium,
reproducing the plurality of recorded signals, and
obtaining the relationship between the amplitudes of signals reproduced from the recorded signals and the duty ratios corresponding thereto in order to specify a pulse strategy for recording information in the phase-change recording medium.
More specifically, the first object of the present invention can be achieved by a method of recording information in a phase-change recording medium with a predetermined recording line speed, comprising the steps of:
conducting a test recording with the application of a laser beam to a predetermined portion of the phase-change recording medium, the laser beam comprising a plurality of pulse trains, each pulse train comprising alternately (a) a comb-shaped pulse train portion comprising a plurality of pairs of pulses, one with a pulse width T1 and a recording power P1, and the other with a pulse width T2 and a recording power P3, and (b) a flat pulse-free portion with a recording power P2, wherein P1, P2 and P3 are in the relationship of P1>P2≧P3 in terms of the intensity of the light of the laser beam, and each of the comb-shaped pulse train portion and the flat pulse-free portion has the same duration width, with a duty ratio of the comb-shaped pulse train portion, defined by T1/(T1+T2) wherein 1/(T1+T2) is a clock frequency, being changed, thereby recording a plurality of signals in the recording medium,
reproducing the plurality of recorded signals to obtain reproduced signals corresponding to the plurality of recorded signals and to determine the amplitudes of the respective reproduced signals, and
obtaining the re
Cooper & Dunham LLP
Edun Muhammad
Ricoh & Company, Ltd.
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