Patent ID: 8036091

Claim:
An optical pick-up comprising: an objective lens to direct light from a light source toward an information recording layer of an optical recording medium; a diffracting optical element to divide reflected light from the optical recording medium into multiple light beams and diffract them; and a photodetector to receive the light beams which have been diffracted by the diffracting optical element, the photodetector being composed of a first photodetecting part to detect first diffracted light which is diffracted light generated by the diffracting optical element and diffracted light in the central region of the reflected light, and a second photodetecting part to detect second diffracted light which is diffracted light in the central region of the reflected light and diffracted light differing in order from the first diffracted light, and the photodetector outputting a first detected signal which is in response to the amount of the second diffracted light detected and which generates a signal for assembling adjustment, and a second detected signal which is in response to the amount of the first diffracted light detected and which generates a signal for information recording and reproducing and feedback control.