Patent ID: 7065009

Claim:
An optical information storage apparatus comprising: a light source for emitting a divergent light; an objective optical system for focusing the light emitted from said light source upon an optical information storage medium to generate a return light at least partially including a signal light corresponding to stored information, and for converting the return light from the optical information storage medium to convergent light and directing the light toward said light source; and an optical device, positioned between said light source and said objective optical system, for passing and guiding the light emitted from said light source to said objective optical system, and for splitting the signal light from the return light reflected by said optical information storage medium and returned via said objective optical system, said optical device comprising a splitting surface formed of a part of a cylindrical surface, passing and guiding the light emitted from said light source via a concave surface side of the splitting surface to said objective optical system, and splitting, by said splitting surface, said signal light from the return light which returns via the same route as the route when guided to the objective optical system and which is incident upon a convex surface side of the splitting surface.