An optical disc and pickup apparatus therefor.

摘要

An optical disc has a two-step pit structure in which first pits (6) and second pits (7) whose depth ( lambda 1/8) is half that ( lambda 1/4) of the first pits are arranged in superposition in the same track direction. A first laser diode (11) emits first laser light having a first wavelength ( lambda 1) which is four times the depth of the first pits, and a second laser diode (12) emits second laser light having a second wavelength ( lambda 2) which is four times the depth of the second pits. An optical system (14-18) introduces the first and second laser light beams onto a recording surface (17) of the optical disc and also introduces reflected light to a detector (19). A selecting drive mechanism (13,20) may be provided to select one of the first and second laser diodes as a light source for actually emitting light to be introduced onto the recording surface. <IMAGE>