Patent ID: 7142492
Filing Date: 2006-11-28
Classification: G11B

Abstract:
1. A method for determining a power of a laser beam which is adapted for determining a recording power of the laser beam to be projected onto a data rewritable type optical recording medium for recording data therein, which comprises steps of: projecting the laser beam onto a first track, a second track and a third track in this order formed on the data rewritable type optical recording medium to be adjacent with each other while varying a level of the recording power of the laser beam, thereby recording a first test signal; reproducing the first test signal recorded on the second track, measuring, for each of the levels of the recording power of the laser beam, jitter JJ projecting the laser beam onto the first track and the third track y times where y is a positive integer, thereby directly overwriting the first test signal recorded on the first track and the first test signal recorded on the third track with the first test signal; reproducing the first test signal recorded on the second track, measuring jitter JJ(n+1) of the thus reproduced signal where n is an integer equal to or larger than 0 and equal to or smaller than y, obtaining, for each of the levels of the recording power of the laser beam, a value of nc of n at which a function of a difference between JJ(n+1) and JJ setting the recording power of the laser beam to a predetermined level, projecting the laser beam onto a fourth track, a fifth track and a sixth track in this order formed on the data rewritable type optical recording medium to be adjacent with each other, thereby recording a second test signal thereon, reproducing the second test signal recorded on the fifth track, measuring an amplitude A directly overwriting the second test signal recorded on the fourth track and the second test signal recorded on the sixth track with the second test signal x times, reproducing the second test signal recorded on the fifth track, measuring an amplitude A(x+1) and jitter J(x+1) of the thus reproduced signal, calculating, for each of the levels of the recording power of the laser beam, a second parameter as a function of a difference between the amplitude A obtaining a value of the first parameter corresponding to a value of the second parameter when the third parameter is equal to a tolerance, thereby determining a critical parameter; recording a third test signal in the data rewritable type optical recording medium while varying levels of the recording power of the laser beam; measuring, when signal characteristics of a reproduced signal obtained by reproducing the third signal recorded in the data rewritable type optical recording medium satisfy reference conditions, an amplitude D comparing the critical parameter and the fourth parameter, and determining the recording power of the laser beam at which the fourth parameter was obtained as an optical recording power when the fourth parameter is equal to or smaller than the critical parameter.