| 摘要 |
An optical information playback apparatus comprises a light detector having a light receiving area divided into four sections by transverse axes and an optical system having a cylindrical lens arranged with its axis taken at about a 45 DEG angle to a direction of an information track of an optical disk to direct a reflected light from the optical disk to the light detector. A difference signal between outputs from the light receiving sections on the opposite sides of the axis parallel to an information track of the optical disk and the axis transverse to the information track, respectively, is produced for use as a focusing signal and as a tracking signal for tracking the information track with the tracking signal having an improved S/N ratio.
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