Patent ID: 7680007

Claim:
An optical state recognizer for recognizing a state of a light beam that is irradiated from a light source on a diffraction grating, the light beam comprising a transmitted light beam transmitted by the diffraction grating and a diffracted ham beam diffracted by the diffraction grating, the transmitted light beam and the diffracted light beam being irradiated on a recording surface of a recording medium comprising a reference recording medium and a target recording medium and being reflected by the recording surface, the optical state recognizer comprising: a reference light intensity information acquiring section that acquires reference transmitted light intensity information corresponding to an intensity of the transmitted light beam reflected toward a first region by the recording surface of the reference recording medium whose recording surface has a specific reflection characteristic and reference diffracted light intensity information corresponding to an intensity of the diffracted light beam reflected toward a second region by the reference recording medium; a detected light intensity information generating section that detects an intensity of the transmitted light beam reflected by the recording surface of the target recording medium toward the first region to generate first detected light intensity information corresponding to the detected intensity of the transmitted light beam and detects an intensity of the diffracted light beam reflected by the recording surface of the target recording medium toward the second region to generate second detected light intensity information corresponding to the detected intensity of the detected light beam; and a reflected state recognizing section that recognizes an optical reflected state of the target recording medium on the basis of a ratio of intensity of the reference transmitted light intensity information and the reference diffracted light intensity information, and intensities of the first detected light intensity information and the second detected light intensity information.