Optical information reproduction apparatus and optical information reproduction method

An optical information reproduction method of reproducing information from an optical information recording medium by using holography, the method comprising:

• a laser emission process of generating a reference beam;
• an optical axis division process of dividing the reference beam into at least two reference beams or more having different angles in a multiplexing direction;
• a multiplexing angle adjustment process of adjusting the angle of the divided reference beams in the multiplexing direction;
• a perpendicular angle adjustment process of adjusting an angle of the reference beam in a direction perpendicular to multiplexing;
• an imaging process of detecting diffraction light which is to be reproduced from the optical information recording medium;
• a detection process of causing a light detecting unit which has at least two light receiving surfaces or more, to detect diffraction light which is reproduced by irradiating the optical information recording medium with the reference beam in a state where an angle of the reference beam in the multiplexing direction is shifted from an optimal angle;
• and
• an angular error signal calculation process of generating an angular error signal in a direction perpendicular to multiplexing of the reference beam, from a signal detected by the light detecting unit,
• wherein in the perpendicular angle adjustment process, the angle of the reference beam in the direction perpendicular to multiplexing is adjusted based on a signal which is output in the angular error signal calculation process.

An optical information reproduction method of reproducing information from an optical information recording medium by using holography, the method comprising:

• a laser emission process of generating a reference beam;
• an optical axis division process of dividing the reference beam into at least two reference beams or more having different angles in a multiplexing direction;
• a multiplexing angle adjustment process of adjusting the angle of the divided reference beams in the multiplexing direction;
• an imaging process of detecting diffraction light which is to be reproduced from the optical information recording medium;
• a detection process of causing a light detecting unit which has at least two light receiving surfaces or more, to detect diffraction light which is reproduced by irradiating the optical information recording medium with the reference beam in a state where an angle of the reference beam in the multiplexing direction is shifted from an optimal angle;
• and
• a wavelength error signal calculation process of generating a wavelength error signal from a signal detected by the light detecting unit,
• wherein in the emission process, a wavelength is adjusted based on a signal which is output in the wavelength error signal calculation process.