Patent ID: 7729218
Filing Date: 2010-06-01
Classification: G11B

Abstract:
1. An apparatus for recording and reproducing a signal on and from a rewritable optical disc by applying a laser beam to the optical disc, the optical disc having a plurality of recording layers including a selected recording layer, the apparatus comprising: first means for recording test signals on a prescribed area in the selected recording layer while changing a power of the laser beam among a setting recording power, a setting erasing power, and a setting bias power, the setting recording power changing the selected recording layer from a crystalline state to an amorphous state, the setting erasing power changing the selected recording layer from the amorphous state to the crystalline state, the setting bias power preventing unwanted diffusion of heat in the selected recording layer; second means for, after the first means records the test signals on the prescribed area in the selected recording layer, exposing the prescribed area in the selected recording layer to the laser beam and scanning the prescribed area in the selected recording layer by the laser beam while maintaining the power of the laser beam at a DC erasing power and changing the DC erasing power among different values, wherein the different values of the DC erasing power are assigned to the recorded test signals respectively; third means for reproducing the recorded test signals from the prescribed area in the selected recording layer to obtain reproduced signals after the second means implements said exposing and scanning; fourth means for detecting parameter values of the respective reproduced signals obtained by the third means, the parameter values being at least ones of (1) modulation factors, (2) modulation-factor-slope “γ” values, (3) asymmetry-related “β” values, and (4) asymmetry values, wherein the detected parameter values of the reproduced signals correspond to the different values of the DC erasing power respectively; fifth means for deciding, among the parameter values detected by the fourth means, a detected parameter value matching one of (1) a target value and (2) a target condition; sixth means for selecting, from the different values of the DC erasing power, one corresponding to the parameter value decided by the fifth means; seventh means for multiplying a prescribed coefficient and the DC erasing power value selected by the sixth means to calculate an optimum level of the erasing power of the laser beam.