Compact-Size Optical Head For Magneto-Optical Disk Drive

A compact-size optical head for magneto-optical disk drives has been developed. The head is designed to be built into a disk drive which is of the same size as a full-height, 5.25" floppy disk drive. By using a newly developed semiconductor laser that can radiate a beam with a small divergent angle and of small eccentricity, we have attained simplification of a collimating system and ease of assembly. To obtain a high readout carrier-to-noise ratio, we have adopted the differential readout method and the high frequency superposition method. Moreover, to stabilize a focus servo system when a focused spot traverses guide grooves, we have chosen the pupil obscuration method for focus error detection. With these technologies, continuous irradiation of 8mW onto a disk surface and a carrier-to-noise ratio in excess of 50dB within 30kHz bandwidth have been achieved.