Read/write Optical Head Compensation for Birefringence of Plastic Cover of Optical Disk
Original Publication Date: 1986-Jan-01
Included in the Prior Art Database: 2005-Mar-08
Most optical disks use a clear plastic cover plate over the data layer of the optical disk to protect the data area from damage due to contamination and handling. The read and write beams pass through this cover and undergo an undesirable retardation due to the plastic cover. In a typical optical storage system this additional retardation adds to the desired retardation of the system's quarter-wave plate. To compensate for that additional retardation, the system's quarter-wave plate is modified to provide a retardation of l/4 wave minus the average retardation caused by the disk cover plate.