Armstrong, Nikaido, Marmelstein, Kubovcik & Murray
Optical information recording and reproducing apparatus
 In an optical information recording and reproducing apparatus for recording and reproducing information by controlling the focus of an optical system for condensing and projecting lights of a light source onto a recording medium, an offset part produced in case the lights are condensed and projected in a focus servo state in data writing regions in the recording medium and prepit regions which are adjacent to the data writing regions and in which discriminating codes are written is detected in the respective format regions by a format detecting means and an offset fluctuation controlling voltage is impressed on the basis of this detecting signal to inhibit the fluctuation of the offset in the respective regions of different formats. 
Olympus Optical Co., Ltd.
G G
G11B G11B
additional inventional
Nobuyuki Kiichi
Kaneko Kato