CD playback using a monolithic confocal laser coupler with a confocal knife edge (CKE) structure

We previously reported a monolithic optical pick-up based on confocal optic s [1]. Although the optical pick-up is very stable in principle for a lens displacement, we found some substantial problems in using the confocal opti cal system for detection of tracking-error (TE) signal. In this paper, we discuss the inherent characteristics of TE signal using t he confocal optical system and we also propose another monolithic optical p ick-up which has an improved TE detection method to be applied to the optic al disk with any pit depth. Using this novel optical pick-up, we demonstrat e CD playback with a single-beam device for the first time. Jitter level ac hieved is 6.7ns. Drastic improvement in DC offset against lens shift in rad ial direction was also achieved compared with the conventional push-pull me thod. The new optical pick-up also demonstrates to be a substantially stabl e system.