Parkhurst & Oliff
Apparatus for recording and reproducing information on an optical disc
 An optical recording and reproducing apparatus includes a first semiconductor laser for emitting a recording laser beam whose intensity is modulated in accordance with an information signal to be recorded and a second semiconductor laser for emitting a reproducing laser beam having a constant intensity. The recording and reproducing semiconductor lasers are commonly mounted in a supporting member which is mounted on a pick-up plate arranged movably in a radial direction of a rotating optical disc. The recording and reproducing laser beams are composed with each other by means of a substantially parallelogram shaped prism having a reflection surface for reflecting the reproducing laser beam and an optical surface upon which the reproducing laser beam is made incident at an incident angle larger than a critical angle and the recording laser beam is made incident at an incident angle near Brewster's angle. The composed recording and reproducing laser beams are commonly focussed by a single objective lens onto the optical disc in such a manner that the recording laser beam is made incident upon an information track to be formed and the reproducing laser beam is made incident upon a guide track or a previously recorded information track. 
Olympus Optical Company Limited
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G11B G11B G11B
inventional inventional inventional
Kiichi Masaharu Haruhiko
Kato Sakamoto Takemura