Patent ID: 7126897
Filing Date: 2006-10-24
Classification: G11B

Abstract:
1. A multi-level information recording method for radiating a laser beam in an information recording medium and recording multi-level data in said information recording medium wherein a radiation energy level of said laser beam is controlled in accordance with said multi-level data, comprising the steps of: recording a known multi-level data sequence by using said laser beam of a radiation energy level corresponding to a combination of multi-level data and obtaining a reproduction result for said combination; performing a waveform equalizing process for said reproduction result; computing a target signal level for each combination of said multi-level data by using a waveform equalizing coefficient; computing a difference between said target signal level and a value obtained by performing said waveform equalizing process; determining a correction amount of said laser beam for each combination of said multi-level data in accordance with said waveform equalizing coefficient and said difference; and determining a correction amount of said laser beam corresponding to said combination of the multi-level data, and wherein said waveform equalizing process is performed based on a formula (1), and said correction amount of the laser beam is determined based on a formula (2),  where the number of taps of a waveform equalizer is 2h+1, EQ′(i) is a signal level after said waveform equalizing process, s′(i) is a reproduction signal level of i-th multi-level data, Cj is a waveform equalizing coefficient (j=−h, −(h−i), . . . , −1, 0, 1, . . . , h−1, h), β is a correction coefficient, Δ(i) is a difference between a target signal level and a result of the waveform equalizing process, and ds′(i)/dE(i) is a gradient of a curve of said reproduction signal level s′(i) to a laser beam energy E(i).