Technique for Adjusting Optical File Head to Compensate Phase Distortion Due to Disc Land/Groove Structure
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19
The combination of an astigmatic lens and a quadrant detector is often used to generate servo information for the track-following and focusing of the optical beam. Due to the land/groove structure on the optical discs, the reflected light contains a phase distortion which causes the position of the detector to be in error. The technique described below solves this problem. The divergent light from laser 1 is collected with lens 2. The collimated beam passing through the polarizing beam splitter (PBS) 3 is focused into a spot on disk 5 by objective lens 4. Interaction of the light spot with the disc land/groove structure 5A gives rise to a phase distortion in the reflected wavefront.