Patent ID: 7911918
Filing Date: 2011-03-22
Classification: G03H,G11B

Abstract:
1. An optical recording method, comprising: a first step of recording an interference image, in which a recording light is irradiated to an optical recording medium that is provided with a recording layer to record information by use of holography, an interference image is formed, and the interference image is formed on the recording layer, wherein the recording light is irradiated at an optional focusing length X1 in thickness direction of the recording layer, and multiple bits are recorded per one recording, and a second step of recording an interference image, in which the recording light is irradiated to form a second interference image, and the second interference image is formed and recorded on the recording layer, wherein the recording light is irradiated at a focusing length X2 that is different from the focusing length X1, and multiple bits are recorded per one recording, wherein the optical recording medium comprises at least two hologram memories, which record focus position information with an interval in thickness direction of the recording layer, and the focus position information comprises at least one of track information, address information, and focusing length information that expresses a distance between a collecting lens and the focus point of the recording light, wherein the optical recording method comprises: a first servo step, in which the recording light is irradiated to a first hologram memory among the at least two hologram memories, the diffracted light from the first hologram memory is received, the recording light is subjected to tracking servo on the basis of the track information and the address information, and the recording light is subjected to focus servo on the basis of the focusing length information, a first step of recording the interference image, in which the focus position of the recording light is displaced horizontally in parallel with layer plane of the recording layer and within the plane that contains the first hologram memory so as to place the focus position of the recording light to a position other than the first hologram memory, the recording light is irradiated to the recording layer to form the first interference image, and the first interference image is recorded on the recording layer, a second servo step, in which the recording light is irradiated to a second hologram memory, which records with an interval between the first hologram memory in thickness direction of the recording layer, the diffracted light from the second hologram memory is received, the recording light is subjected to tracking servo on the basis of at least one of the track information and the address information, and the recording light is subjected to focus servo on the basis of the focusing length information, and a second step of recording the interference image, in which the focus position of the recording light is displaced horizontally in parallel with layer plane of the recording layer and within the plane that contains the second hologram memory so as to place the focus position of the recording light to a position other than the second hologram memory, the recording light is irradiated to the recording layer to form the second interference image, and the second interference image is recorded on the recording layer.