AN OPTICAL DATA READING/WRITING DEVICE HAVING SEPARATED READ AND WRITE BEAMS

摘要

A method is proposed that allows a static design of an optical pickup unit (OPU) that delivers two output beams (30, 32). Both laser beams (30, 32) result in successive spots, which have the appropriate characteristics. In this OPU concept both read and write spots are present at the same time, and they are sufficiently spaced apart in the focus direction. This allows switching from the read situation to the write situation by introducing an appropriate focus offset in the electronics . The two output beams (30,32) are generated from a polarized incoming beam, said polarized incoming beam is split by a tilted birefringent grating (18).