Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-01-27
2001-04-24
Tran, Thang V. (Department: 2753)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S059160
Reexamination Certificate
active
06222814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase-change drive of a high transfer rate, and more particularly, to a phase-change optical disc drive with a semiconductor laser power control and a method of writing/reading a phase-change optical disc at a high transfer rate by controlling the laser power of the semiconductor laser.
2. Description of Related Art
Typical phase-change optical discs in which information can be rewritten include a so-called DVD-RAM. DVD-RAM adopts an EFM (Eight-to-Fourteen Modulation) method for signal modulation to drive a semiconductor laser to emit multi-pulses for generation of recording waveforms for marks of 3T to 11T.
FIG. 1
is a timing chart of recording waveforms in DVD-RAM. As shown, a mark 3T is written with a single light pulse while a mark 11T is recorded with nine light pulses. Each light pulse is immediately followed by a bias power
2
set to a lower value than a bias power
1
corresponding to an erasure power to control the crystallization speed of the phase-changed recording medium. Further, both leading and trailing pulses have a period of about 1T, and they are generated with predetermined time delays (T
SFP
and T
SLP
in FIG.
1
), respectively, from the clock pulse.
DVD-RAM uses a clock frequency of 29 MHz (user transfer rate of 11 Mbps). Both the leading and trailing pulses have a width of about 35 ns. The recording power of these light pulses is detected by a laser power monitoring detector, and then sampled and given a predetermined value, thus the recording pulse is controlled to always have a constant power. For example, the peak power is controlled by sampling the light power of the leading or trailing pulse, and the bias power
1
is controlled by sampling the light output of the multi-pulse. Note that the bias power
2
is controlled by sampling a reproducing output detected by an RF signal detector.
For a phase-change optical disc drive of a higher transfer rate than the normal one of DVD-RAM, however, it is necessary to increase the clock frequency. For a clock frequency of 100 MHz (use transfer rate of 38 Mbps), for example, the leading and trailing pulses will have a width of less than 10 ns, so it will be difficult to accurately sample the light output for controlling the recording power. Furthermore, wen the light pulse is less than 10 ns in width, it will easily be affected by noise component and also a sufficient band of the optical system cannot be assured, so that the recording power cannot be controlled.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a phase-change optical disc writing/reading apparatus and method in which a laser power of a semiconductor laser can be accurately controlled even at the time of writing or reading a phase-change optical disc at a high transfer rate.
The above object can be attained by providing a phase-change optical disc drive in which a data of nT in pulse width is recorded with a multi-pulse generated from a semiconductor laser, including a number (n−1) of pulses and which shifts at a minimum of three levels, comprising according to the present invention:
means for detecting a laser power of the semiconductor laser; and
means for generating, when in a power control mode, an output control pulse larger in pulse width than the multi-pulse to drive the semiconductor laser to generate a light pulse based on the output control pulse, sampling and holding, based on the output control pulse, the laser power detected by the detecting means, and controlling the laser power of the semiconductor laser so that the sampled and held laser power has a predetermined value.
When in the power control mode, the phase-change optical disc drive generates, when in the power control mode, an output control pulse larger in pulse width than the multi-pulse, drives the semiconductor laser based on the output control pulse to generate a light pulse, samples and holds, based on the output control pulse, the laser power detected by the detecting means, and controls the laser power of the semiconductor laser so that the sampled and held laser power has a predetermined value.
The above object can also be attained by providing a method of recording a data of nT in pulse width with a multi-pulse generated from a semiconductor laser, including a number (n−1) of pulses and which shifts at a minimum of three levels, comprising, according to the present invention, the steps of:
generating, when in a power control mode, an output control pulse larger in pulse width than the multi-pulse;
driving the semiconductor laser to generate a light pulse based on the output control pulse;
detecting a laser power of the semiconductor laser;
sampling and holding the detected laser power; and
controlling the laser power of the semiconductor laser so that the sampled and held laser power has a predetermined value.
When in the power control mode, an output control pulse larger in pulse width than the multi-pulse is generated, and the semiconductor laser is driven based on the output control pulse to emit a light pulse, the laser power detected by the detecting means is sampled and held based on the output control pulse, and the laser power of the semiconductor laser is controlled so that the sampled and held laser power has a predetermined value.
These objects and other objects, features and advantages of the present intention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4796250 (1989-01-01), Kobayashi et al.
patent: 4845720 (1989-07-01), Koishi et al.
patent: 5059780 (1991-10-01), Kakuta
patent: 5457666 (1995-10-01), Toda et al.
patent: 5477557 (1995-12-01), Inaba et al.
patent: 5490126 (1996-02-01), Furumiya et al.
patent: 5495463 (1996-02-01), Akagi et al.
patent: 5636179 (1997-06-01), Tateishi
patent: 5642343 (1997-06-01), Toda et al.
patent: 5798992 (1998-08-01), Kaneko et al.
patent: 5974021 (1999-10-01), Toda et al.
patent: 0 552 936 (1993-07-01), None
patent: 0 851 413 (1998-07-01), None
patent: 9-330519 (1997-12-01), None
Frommer William S.
Frommer Lawrence & Haug LLP.
Sony Corporation
Tran Thang V.
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