Abstract: In an information recording/reproducing apparatus, there is provided a mechanism for opening/closing a shutter of a cartridge having a case for storing a recording medium. The shutter is adapted to be slidable in a recess portion on a case surface. The cartridge is held by a holder. A shutter opening/closing device is arranged on an upper surface of the holder so as to open/close the shutter of the cartridge. A projection is formed in front of the shutter opening/closing device in an insertion direction of the cartridge with respect to the holder, on the inner surface of the holder facing the cartridge.

Abstract: In an optical pickup apparatus comprising a light source for applying a light beam to an optical memory medium, a beam splitter disposed in the optical path from the light source to the medium to separate the reflected beam from the medium from the beam from the light source, and a photodetector for detecting the separated reflected beam, having a surface opposed to that surface of the beam splitter which faces the photodetector is formed so as to form an angle different from the perpendicular with respect to the optic axis of the separated reflected beam.