Patent ID: 7706243
Filing Date: 2010-04-27
Classification: G11B

Abstract:
1. A method of reproducing multi-level information recorded by changing one of a width and an area of an information pit in a track direction, and a phase of the information pit in virtual cells provided on a track of an optical information medium at predetermined intervals, the method comprising the steps of: setting the optical information medium including a plurality of cells, each of which is recorded with an information pit of a selected level of an N-value (N≧3), and a cell recorded with an information pit of a selected level of an M-value (M<N) for each group including the plurality of cells, wherein the cell recorded with the information pit of a selected level of the N-value follows the cell recorded with the information pit of a selected value of the M-value; obtaining a reproduction signal when a center of a light spot is moved to a center of the cell recorded with the information pit of a selected level of the M-value; and correcting a reproduction signal of the cell recorded with the information pit of the selected level of the N-value, based on a difference between the reproduction signal of the cell recorded with the information pit of a selected level of the M-value and a reference signal obtained from learning information.