Apparatus and method for recording optical information, apparatus and method for reproducing optical information, and apparatus and method for recording/reproducing optical information

In a servo operation, position-controlling light, which is red light, is projected onto a recording medium so as to converge to a minimum diameter on a reflecting surface of the recording medium. In a recording operation, information light and recording-specific reference light, each of which is green light, are projected coaxially onto one side of an information recording layer of the recording medium so as to converge to a minimum diameter at an identical position located off the reflecting surface. Information is recorded in the information recording layer in the form of an interference pattern resulting from interference between the information light yet to impinge on the reflecting surface and the recording-specific reference light reflected by the reflecting surface and an interference pattern resulting from interference between the recording-specific reference light yet to impinge on the reflecting surface and the information light reflected by the reflecting surface.