Optical information recording and reproducing apparatus and optical information recording apparatus

An optical information recording and reproducing apparatus for recording information on a recording medium by forming interference fringes generated by interference between an information beam and a reference beam on the recording medium and for reproducing the information by irradiating, with the reference beam, the recording medium, in which the interference fringes are formed, said apparatus comprising:

• a spatial light modulator for spatially modulating at least a portion of a light beam emitted from a light source into the information beam, wherein said spatial light modulator comprises a plurality of modulators changing in the intensity of reflection light, according to a modulation signal;
• a light sensing device that reads the information beam extracted from the recording medium by the reference beam irradiated on the recording medium;
• a shift amount detector that detects a shift of the irradiating position of the light beam entering said spatial light modulator;
• and
• means that corrects a positional shift between a position of an area for modulating the information beam and a position of the light beam in said spatial light modulator, based on a positional shift amount detected by said shift amount detector.