Optical recording method, optical recording apparatus and optical recording medium

Abstract

To provide an optical recording method including: applying information and reference beams onto an optical recording medium to record information therein, the optical recording medium having a recording layer for recording the information by holography, wherein at least the information beam is passed through a spatial light modulator and is formed as a two-dimensional pattern composed of a data area and a plurality of synchronization marks for detecting information concerning the positions of data recorded in the data area, and wherein the synchronization marks are arranged in a random pattern so that in a Fourier-transformed image of the two-dimensional pattern, light intensities derived from the synchronization marks are lower than light intensities in a Fourier-transformed image of a two-dimensional pattern composed of a data area and a plurality of synchronization marks arranged in a grid pattern, the light intensities being derived from the synchronization marks arranged in a grid pattern.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing a pattern of synchronization marks of a conventional information beam passed through a spatial light modulator, the synchronization marks being arranged in a grid pattern.

FIG. 2 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a random pattern.

FIG. 3 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a solid cross.

FIG. 4 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a dotted cross.

FIG. 5 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a zigzag cross.

FIG. 6 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a corrugated cross.

FIG. 7 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a solid line which encompasses the entire circumference of a data area.

FIG. 8 is a conceptual diagram showing a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a dotted line which encompasses the entire circumference of a data area.

FIG. 9 is a perspective diagram conceptually showing performing shift-multiplexing recording on an optical recording medium using the information beam and the reference beam in the present invention.

FIG. 10 is a schematic cross-sectional view of a conventional optical recording medium.

FIG. 11 is another schematic cross-sectional view of a conventional optical recording medium.

FIG. 12 is a partial schematic cross-sectional view showing the structure of the optical recording medium of the present invention.

FIG. 13 is an exploded perspective view showing an example of the layer configuration of the optical recording medium of the present invention.

FIG. 14 is a schematic cross-sectional view showing an example of the structure of an optical recording medium according to Specific Example 1.

FIG. 15 is a schematic cross-sectional view showing an example of the structure of an optical recording medium according to Specific Example 2.

FIG. 16 is a graph showing reflection characteristics of a filter, which is a laminate of three cholesteric liquid crystal layers, for incident light from the vertical direction (0°).

FIG. 17 is an explanatory diagram showing an example of optical systems according to the present invention around an optical recording medium.

FIG. 18 is a block diagram showing an example of an entire configuration of the optical recording apparatus of the present invention.

FIG. 19 is a conceptual diagram showing a specific example of a pattern of a conventional information beam passed through a spatial light modulator, the synchronization marks being arranged in a grid pattern.

FIG. 20 is a conceptual diagram showing a specific example of a Fourier-transformed image of a conventional information beam passed through a spatial light modulator, the image having synchronization marks arranged in a grid pattern.

FIG. 21 is a conceptual diagram showing a specific example of a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a random pattern.

FIG. 22 is a conceptual diagram showing a specific example of a Fourier-transformed image of an information beam in the present invention passed through a spatial light modulator, the image having synchronization marks arranged in a random pattern.

FIG. 23 is a conceptual diagram showing a specific example of a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a solid cross.

FIG. 24 is a conceptual diagram showing a specific example of a Fourier-transformed image of an information beam in the present invention passed through a spatial light modulator, the image having synchronization marks arranged in a solid cross.

FIG. 25 is a conceptual diagram showing a specific example of a pattern of synchronization marks of the information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a dotted cross.

FIG. 26 is a conceptual diagram showing a specific example of a Fourier-transformed image of an information beam in the present invention passed through a spatial light modulator, the image having synchronization marks arranged in a dotted cross.

FIG. 27 is a conceptual diagram showing a specific example of a pattern of synchronization marks of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a solid line which encompasses the entire circumference of a data area.

FIG. 28 is a conceptual diagram showing a specific example of a Fourier-transformed image of an information beam in the present invention passed through a spatial light modulator, the image having synchronization marks arranged in a solid line which encompasses the entire circumference of a data area.

FIG. 29 is a conceptual diagram showing a specific example of a pattern of an information beam in the present invention passed through a spatial light modulator, the synchronization marks being arranged in a dotted line which encompasses the entire circumference of a data area.

FIG. 30 is a conceptual diagram showing a specific example of a Fourier-transformed image of an information beam in the present invention passed through a spatial light modulator, the image having synchronization marks arranged in a dotted line which encompasses the entire circumference of a data area.

Claims

1. An optical recording method comprising: applying an information beam and a reference beam onto an optical recording medium to record information therein, the optical recording medium having a recording layer for recording the information by holography,wherein at least the information beam is passed through a spatial light modulator and is formed as a two-dimensional pattern that is composed of a data area and a plurality of synchronization marks for detecting information concerning the positions of data recorded in the data area, andwherein the synchronization marks are arranged in a random pattern so that in a Fourier-transformed image of the two-dimensional pattern, light intensities derived from the synchronization marks are lower than light intensities in a Fourier-transformed image of a two-dimensional pattern composed of a data area and a plurality of synchronization marks arranged in a grid pattern, the light intensities being derived from the synchronization marks arranged in a grid pattern.

2. The optical recording method according to claim 1, wherein the synchronization marks arranged in a random pattern are present in two or more different forms.

3. The optical recording method according to claim 1, wherein the synchronization marks arranged in a random pattern are randomly arranged both in vertical and horizontal directions.

4. The optical recording method according to claim 1, wherein the synchronization marks are arranged in a cross consisting of a vertical line and a horizontal line, and at least one of the vertical line and horizontal line is a straight line or curve.

5. The optical recording method according to claim 1, wherein the synchronization marks are arranged at the entire circumference of the two-dimensional data area, the synchronization marks being arranged in a straight line or curve.

6. The optical recording method according to claim 4, wherein the straight line or curve constituting the synchronization marks is a solid line or solid curve.

7. The optical recording method according to claim 4, wherein the straight line or curve constituting the synchronization marks is a dotted line or dotted curve.

8. The optical recording method according to claim 7, wherein the interval between the adjacent synchronization marks in the dotted line or dotted curve is an integer multiple of a minimum pixel interval of the spatial light modulator.

9. The optical recording method according to claim 1, wherein recording of information performed by application of the information beam and reference beam is performed with shift-mutiplexing recording.

10. The optical recording method according to claim 1, wherein the information beam and reference beam are applied in such a way that the optical axis of the information beam is collinear with the optical axis of the reference beam.

11. The optical recording method according to claim 1, wherein the optical recording medium comprises, in order, a first substrate, the recording layer, a filter layer, and a second substrate.

12. The optical recording method according to claim 1, wherein the optical recording medium records therein a reflective hologram.

13. An optical recording apparatus comprising: a laser light source for emitting an information beam and a reference beam onto an optical recording medium to record information therein, the optical recording medium having a recording layer for recording the information by holography; anda spatial light modulator through which at least one of the information beam and reference beam passes,wherein the information beam passed through the spatial light modulator is formed as a two-dimensional pattern that is composed of a data area and a plurality of synchronization marks for detecting information concerning the positions of data recorded in the data area, andwherein the synchronization marks are arranged in a random pattern so that in a Fourier-transformed image of the two-dimensional pattern, light intensities derived from the synchronization marks are lower than light intensities in a Fourier-transformed image of a two-dimensional pattern composed of a data area and a plurality of synchronization marks arranged in a grid pattern, the light intensities being derived from the synchronization marks arranged in a grid pattern.

14. An optical recording medium comprising: a hologram recorded by an optical recording method which comprises:applying an information beam and a reference beam onto the optical recording medium to record information therein, the optical recording medium having a recording layer for recording the information by holography,wherein at least the information beam is passed through a spatial light modulator and is formed as a two-dimensional pattern that is composed of a data area and a plurality of synchronization marks for detecting information concerning the positions of data recorded in the data area, andwherein the synchronization marks are arranged in a random pattern so that in a Fourier-transformed image of the two-dimensional pattern, light intensities derived from the synchronization marks are lower than light intensities in a Fourier-transformed image of a two-dimensional pattern composed of a data area and a plurality of synchronization marks arranged in a grid pattern, the light intensities being derived from the synchronization marks arranged in a grid pattern.