Patent ID: 8040783

Claim:
An optical information recording and reproducing apparatus comprising: a light source; a splitting element for splitting a light flux from the light source into light fluxes; an optical system for guiding one of the light fluxes split by the splitting element to an information recording medium as a reference beam; a spatial light modulation element for receiving the other of light fluxes split by the splitting element and generating an information beam; an objective lens for converging the information beam onto the information recording medium; an image receiving element for receiving a light flux from the information recording medium; a moving device for moving the information recording medium between a recording and reproducing position where information can be recorded or reproduced for the information recording medium and a retracting position where the information recording medium is retracted away from the recording and reproducing position; a mirror for moving together with the information recording medium; and a detector for detecting a deviation of at least one of the reference beam and the information beam, wherein the optical information recording and reproducing apparatus employs a two-beam interference method that information is recorded for the information recording medium by using an interference between the reference beam and the information beam both radiated from different directions, and information is reproduced by radiating the reference beam onto the information recording medium and guiding the light flux from the information recording medium to the image receiving element, and wherein the mirror moves to a position which is displaced from the at least one of the reference beam and the information beam when the information recording medium moves to the recording and reproducing position, and moves to a position where the mirror can reflect the at least one of the reference beam and the information beam toward the detector when the information recording medium moves to the retracting position.