| US 7,474,603 B2 | ||
| Optical information recording method, apparatus, and medium, laser control circuit, wobble signal detection method, and servo signal detection method | ||
| Hiroshi Maegawa, Kanagawa (Japan) | ||
| Assigned to Ricoh Company, Ltd., Tokyo (Japan) | ||
| Filed on Aug. 29, 2003, as Appl. No. 10/650,814. | ||
| Claims priority of application No. 2002-259179 (JP), filed on Sep. 04, 2002; application No. 2002-346800 (JP), filed on Nov. 29, 2002; and application No. 2002-346820 (JP), filed on Nov. 29, 2002. | ||
| Prior Publication US 2004/0052177 A1, Mar. 18, 2004 | ||
| Int. Cl. G11B 7/00 (2006.01) | ||
| U.S. Cl. 369—116 [369/47.51; 369/59.11] | 1 Claim |
| 1. A laser control circuit adapted to modulate a light intensity of a laser beam irradiated for recording multilevel information
on an optical information recording medium, wherein an area of the optical information recording medium is divided into approximately
uniform cells, and marks that can be formed in a plurality of sizes are recorded on the cells according to the multilevel
information being recorded by adjusting a time width of a bias power period and an off power period of the laser beam, said
laser control circuit comprising:
a unit that inputs a clock signal indicating a cell frequency and the multilevel information corresponding to each cell, and
determines a laser beam emission waveform for each cell based on the input clock signal and multilevel information,
wherein a period of an n-multiplied frequency (n being an integer) of the clock signal indicating the cell frequency is used
as a step in setting the laser beam emission waveform, and
wherein the time width of the bias power period is based on an equation:
Tb=(a−1)Tx+Ty,
where Tb is the time width of the bias power period, a is a multilevel value, Tx is a unit of time width, and Ty is a time
width provided for each level of multilevel information.
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