Optical pickup system for DVD and CD-R disks uses holographic ring lens to differentially diffract two wavelengths into suitable spots

摘要

The optical pickup is used to read data from either a DVD disk (37) or a CD-R (41) disk. Two laser sources (31,39) and detectors (38,39) provide the two wavelengths needed. A selective optical unit (33) directs wavelengths as required. The light beams pass through a holographic ring lens (35) that has outer and inner areas that differently diffract the wavelengths. The diffracted beams pass through an objective (36) that produces the spot on the relevant disk.