Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Patent
1997-10-23
1999-01-19
Dinh, Tan
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
430321, G11B 724
Patent
active
058621229
ABSTRACT:
The optical phase difference between reflected laser light from the crystalline and the amorphous part of a phase change recording layer is established as 180 degrees .+-.5 degrees. The ratio between the light absorption factor when the phase change recording film is in the crystalline condition to that when it is in the amorphous condition is set to within the range 0.9 to 1.1. With the wavelength of the laser light used as .lambda., the optical depth of a guide groove formed on the substrate is set to within the range .lambda./9 to .lambda./6. With the wavelength of the laser light used in the range 635 nm to 650 nm, the depth of the guide groove is in the range 40 to 70 nm. In an optical disk such as this, when seen from reflected light, the groove region of a groove during playback and land region of the groove during playback are optically equivalent. For this reason, it is substantially the same as the case in which the optical phase difference between the reflected laser light from the crystalline part of the recording film and the reflected laser light from the amorphous part of the recording film is zero, this making it possible to achieve consistency in the signal levels between land playback and groove playback. As a result, it is possible to perform double track density recording and mark edge recording.
REFERENCES:
patent: 5381395 (1995-01-01), Okada
patent: 5493561 (1996-02-01), Nishiuchi et al.
patent: 5646924 (1997-07-01), Nonoyama et al.
Ishida et al., High Density Mark Edge Recording on a Phase Change Rewritable Disk by 680nm Laser Diode, pp. 70-75, Nov., 1994.
Ohno et al., High Density Phase Change Optical Disks Using Land & Groove Recording Method, pp. 114-120, Nov., 1993.
Ohkubo Shuichi
Okada Mitsuya
Dinh Tan
NEC Corporation
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