METHOD AND APPARATUS FOR REPRODUCING OPTICAL INFORMATION

Abstract

Provided are an optical information reproducing method capable of determining multi-level information with high precision, and an apparatus for the method. Specifically, a cell having a reduced multi-level is provided in a portion of a data region to perform the level correction or the AGC. For example, a cell recorded with an M-value for each group including a plurality of cells, each of which is recorded with an N-value (N≧3, M

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an optical information recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship among preceding and following cells and a light spot in a case where a cell center value is sampled.

FIG. 3 is an explanatory diagram showing a positional relationship among the preceding and following cells and the light spot in a case where a cell boundary value is sampled.

FIG. 4 shows a structure in which an M-value mark and N-value marks are recorded in a block and sampling locations of data used for level correction in a first method according to the present invention.

FIG. 5 is an explanatory diagram showing a width of an information pit in a track direction, which is changed according to a level, in a case where the M-value mark is recorded based on a binary level.

FIG. 6 shows an algorithm for performing the level correction on a reproduction signal in the present invention.

FIG. 7 shows a cell center value learning table (one cell of M-value mark and two cells of N-value mark, M=2) consulted for performing the level correction by the first method according to the present invention.

FIG. 8 shows a structure in which M is set to 2, N is set to 8, and cells of two M-value marks and three N-value marks are recorded in a block in a second method according to the present invention.

FIG. 9 shows a cell boundary value learning table (two cells of M-value mark, M=2) consulted for performing level correction by the second method according to the present invention.

FIG. 10 shows a structure in which M is set to 2, N is set to 8, and cells of three M-value marks and three N-value marks are recorded in a block in a third method according to the present invention.

FIG. 11 shows a cell center value learning table (three cells of M-value mark, M=2) consulted for performing level correction by the third method according to the present invention.

FIG. 12 is a schematic block diagram showing an AGC circuit according to the embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a multi-level data determining method for a multi-level data determination circuit.

FIGS. 14A and 14B show learning tables used for multi-level data determination, in which FIG. 14A shows a cell center value learning table and FIG. 14B shows a cell boundary value learning table.

FIG. 15 is an explanatory diagram showing a method of determining a candidate value of a target cell based on the cell center value learning table of a cell center value determination section shown in FIG. 13.

FIG. 16 is an explanatory diagram showing a method of determining a candidate value of the target cell based on the cell boundary value learning table of a cell boundary value determination section shown in FIG. 13.

FIG. 17 is an explanatory diagram showing an algorithm for a final value determination section shown in FIG. 13.

FIG. 18 is an explanatory diagram showing an algorithm for determining a multi-level of the target cell shown in FIG. 17.

FIG. 19 is an explanatory diagram showing an algorithm for correcting a multi-level of a preceding cell shown in FIG. 17.

FIG. 20 is an explanatory diagram showing widths in a track direction and corresponding combinations of three bits based on different levels of multi-level information pits.

FIG. 21 is an explanatory diagram showing amplitude distributions of the cell center values.

FIG. 22 is a simple diagram showing a normal block structure of a fixed pattern region for performing the AGC and the level correction in an optical disk.

Claims

1. A method of reproducing multi-level information recorded by changing one of a width and 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, comprising the steps of: setting the optical information medium including a plurality of cells, each of which is recorded with an N-value (N≧3), and a cell recorded with an M-value (M<N) for each group including the plurality of cells;obtaining a reproduction signal when a center of a light spot is moved to a center of the cell recorded with the M-value; andcorrecting a reproduction signal level of the cell recorded with the N-value, which follows the cell recorded with the M-value based on a difference between a cell center value and a reference value obtained from learning information.

2. The method of reproducing multi-level information according to claim 1, wherein the reference value is a cell center value obtained from the learning information based on a multi-level determination value for determining a multi-level of a target cell recorded with the M-value and a multi-level determination value for a preceding cell and a following cell which are located before and after the target cell, each of which is recorded with one of the M-value and the N-value.

3. The method of reproducing multi-level information according to claim 2, wherein when the target cell recorded with the M-value and successive cells including the preceding cell and the following cell which are located before and after the target cell, each of which is recorded with one of the M-value and the N-value, are included in a single group, the learning information is obtained by learning in advance possible multi-level information of each of the cell center values in the group.

4. A method of reproducing multi-level information recorded by changing one of a width and 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, comprising the steps of: providing a cell recorded with an M-value for each group including a plurality of cells, each of which is recorded with an N-value (N≧3, M<N);obtaining a reproduction signal when a center of a light spot is moved to a center of the cell recorded with the M-value;detecting a peak from a plurality of reproduction signals; andperforming automatic gain control on the reproduction signal based on a value of the detected peak.

5. A method of reproducing multi-level information recorded by changing one of a width and 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, comprising the steps of: setting an optical information medium including a plurality of cells, each of which is recorded with an N-value (N≧3), and cells recorded with successive M-values (M<N) for each group including the plurality of cells;obtaining a reproduction signal when a center of a light spot is moved to an interface between a cell recorded with the M-value and a following cell recorded with the M-value; andcorrecting a reproduction signal level of a cell recorded with the N-value, which follows the cell recorded with the M-value based on a difference between a cell boundary value and a reference value obtained from learning information.

6. The method of reproducing multi-level information according to claim 5, wherein the reference value is a cell boundary value obtained from the learning information based on multi-level determination values for the cells recorded with the successive M-values.

7. The method of reproducing multi-level information according to claim 6, wherein when the cells recorded with the successive M-values are included in a single group, the learning information is obtained by learning in advance possible multi-level information of each of the cell boundary values in the group.