Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2002-04-10
2004-10-05
Gordon, Raquel Yvette (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
Reexamination Certificate
active
06801240
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information recording method and an information recording device suitable for recording an optical mark on an optical disk, especially a phase-change optical disk using a heat applied by laser light irradiation.
2. Description of the Related Art
A method of recording information is known in which a hole is formed in a recording film by a thermal effect of optical energy of irradiated laser light, changing a crystal structure, or changing direction of magnetization, or deforming the recording film, or the like, and, thus, an optical mark is recorded on a recording medium.
Such a method is applied to an optical disk device or a magneto-optical disk device in recent years, and is put in practical use. In such a device, increase in recording density and increase in memory capacity are demanded, as an external information recording device for an information processing device, such as a computer.
As examples of this type of information recording method, or an information recording device, an information recording device disclosed in Japanese laid-open patent application No. 8-221757 (see Japanese patent No. 2899551) is known. There, in synchronization with a predetermined bit period T, a rate of heating/cooling of a phase-change recording medium is controlled by irradiating laser light in a form of an optical pulse for heating and an optical pulse for cooling alternately, and thereby, amorphous mark formation is made by sudden cooling while crystal formation is made by gradual cooling. Such a method may also be applied to information recording on CD-RW.
In this method, a recording length of the optical mark is controlled by changing a manner of repetition of the cooling pulses and heating pulses with bit period intervals. However, in case the predetermined bit period T becomes much shorter and becomes much higher bit rate of 10 nanoseconds or less, it becomes difficult to make a laser pulse to be emitted properly. The limit thereof is approximately 12 times the standard rate on CD.
Recently, a demand of increasing in recording speed has become stronger with technical progress on personal computers. Thereby, improvement in operation speed of a laser light source driving part and improvement in recording efficiency have been demanded. An information recording scheme for responding thereto is disclosed by Japanese laid-open patent application No. 9-134525.
In this scheme, a requirement of pulse light-emitting of a laser light source is eased as a result of heating/cooling pulses of periods of approximately 2T with respect to the bit period T being applied. However, as mark length is classified integrally, heating/cooling pulse may have a length of approximately 1.25T, or the like, and, thereby, it may not be possible to precisely emit light-emitting pulse at a time of some high-speed recording case.
Then, it is required for an information recording method and an information processing device to solve a problem that a mark having a predetermined length-cannot be precisely formed, or a problem that a load required for a laser light source driving part becomes large according to improvement in the recording speed.
Media only for reproduction (recording media) such as a CD for music, a CD-ROM, a DVD, and a DVD-R, an OM, and so forth are put in practical use with development in multimedia. Recently, a phase-change disk also attracts attention besides write-once optical disk employing coloring material, and rewritable MO disk using an optical magnetism material.
In this phase-change disk, a recording material is switched reversibly between a crystal phase and an amorphous phase, and, thus, information is recorded there. Furthermore, in the phase-change disk, reproduction is made only with laser light from a light source of a semiconductor laser and no external magnetic field is needed, unlike MO media, etc. Further, informational recording and erasing can be performed at once by laser light in the phase-change medium. The semiconductor laser is driven by a semiconductor laser driving circuit here.
Generally, a semiconductor laser light-emitting waveform of single pulse generated as a recording waveform for recording information on an information recording medium based on EFM (Eight Fourteen Modulation) code, etc. is used. In a case of using phase-change media, by this recording waveform, a record mark has a distortion in shape like a tear drop with an accumulated heat, or insufficient cooling speed, forming of an amorphous phase becomes inadequate, and there may cause problems that the thus-formed record mark has not a sufficient reflectance to laser light.
In order to solve the above-mentioned problem, forming of a mark on phase-change media is made by laser light of multi-pulse waveform, as shown in
FIG. 1A
, which includes recording power in many stages generated based on the EFM code, etc. A top heating pulse Htop on a mark part of this multi-pulse waveform fully carries out preliminary heating of the recording film of the phase-change medium more than a melting-point temperature. Then, following the top heating pulse Htop, a plurality of heating pulses Hmp occur, while cooling multi-pulses Cmp also occur between these heating pulses, respectively, as shown in the figure. Assuming that light-emitting power of the top heating pulse Htop is Phtop, a light-emitting power of the following heating pluses Hmp is Phmp, and a light-emitting power of the cooling pulses Cmp is Pcmp, setting is made such that:
Phtop=Phmp>Pcmp≈Pr
An erasing part of this multi-pulse waveform includes an erasing pulse E, and a light-emitting power Pe thereof is set such as
Phmp<Pe<Pcmp
Thus, by making a recording waveform into such a multi-pulse waveform, an amorphous phase is formed as a mark part by a condition of sudden cooling of heating
cooling. A crystal phase is formed by a condition of gentle cooling of only heating on the erase portion E. Thereby, a sufficient difference in reflectance can be created between the amorphous phase and crystal phase.
There are two information recording methods, i.e., a mark position (PPM) type and a mark edge (PWM) type. Recently, the mark edge type which can respond to high-density recording is used. In case information recording is performed on phase-change medium according to the mark edge type, a heating/cooling pulse having a length of 0.5T with respect to a recording channel clock period T is used.
That is, whenever the mark length of recording data increases by 1T, the light of the multi-pulse has 1 set of heating pulse and cooling pulse added thereto is used.
FIG. 1A
shows a typical example of recording waveform. Since this recording waveform can always record the record data of different mark length on a predetermined fixed heating/cooling condition, edge shift occurring depending on the mark length of record data can be effectively reduced. Moreover, in a case where high-speed recording is performed by this recording waveform, the recording channel clock frequency is made twice and 4 times, the-same rate at which the record line speed is increased. In this case, the basic number of pulses and the relation between levels of the recording power are maintained, and, the pulse width of the heating multi-pulses Hmp can be set variably in a range between 0.25T and 0.55T.
When recording information on phase-change media by the mark edge recording type is performed, it is important for phase-change media to perform heating sufficient and sudden cooling in a record mark formation portion so as to form~edge parts front and rear of the mark clearly.
However, in the case where high-speed recording is performed with the recording waveform as it is, the recording channel clock frequency is made twice or 4 times, and, thereby, the heating pulse and cooling pulse have a reduced time interval each such that sufficient temperature increase and decrease required for phase change in the recording film may not be achieved. Moreover, the rate of the interval of the heating pulse
Abe Michiharu
Shinotsuka Michiaki
Yokoi Kenya
Dickstein , Shapiro, Morin & Oshinsky, LLP
Gordon Raquel Yvette
Ricoh & Company, Ltd.
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