Simple Rotating Technique to Compensate an Optical Read/Write Head for the Retardation of a Plastic Optical Disk
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19
Many optical systems use a quarter-wave plate and polarizing optics to isolate the source from the reflected beam. In optical storage systems, a severe problem exists in that the protective cover plate of the disk introduces an additional optical retardation resulting in incomplete isolation. This feedback into the laser contributes to laser feedback noise and reduces the signal to the detector. The technique described herein solves these problems. The laser 1 produces a diverging beam which is collimated by lens 2 and sent to the polarizing beam splitter (PBS) 3. The linearly polarized light emerging from PBS 3 is converted to circular polarization by the quarter-wave plate 4. The light is then focused by the objective lens 5 onto the disk surface 7 through the protective cover plate 6.