Patent ID: 6643247
Filing Date: 2003-11-04
Classification: G11B

Abstract:
An information recording/reproducing apparatus comprising:a first light source for emitting an optical beam of a first wavelength; a second light source for emitting an optical beam of a second wavelength different from the first wavelength; an optical system for guiding the optical beams from the first and second light sources along substantially one optical path, said optical system including an object lens and at least one collimate lens, and providing a prism unit for synthesizing the optical beams from the first and second light sources together between the object lens and the at least one collimate lens along an optical pathway; a detector for performing photoelectric conversion with respect to optical beams that are reflected by an optical information medium and recieved at the detector by way of the object lens; and a beam diameter varying device, arranged between one of the at least one collimate lens disposed in the vicinity of each of the first and second light sources and the prism unit along the optical, pathway, for varying a beam spot diameter of an optical beam emitted from one of the first and second light sources, wherein said beam diameter varying device has a light-shielding structure for shielding a central portion of a light beam output from one of the at least one collimate lens. wherein said beam diameter varying device has a light-shield structure for shielding a central portion of a light beam output from one of the at least one collimate lens.