DEVELOPMENT OF PLANAR OPTICS FOR AN OPTICAL TRACKING SENSOR

An optical tracking sensor for large-capacity flexible disk drive (FDD ) is demonstrated. The passive optics is compact and lightweight (5.4 mm length x 3.6 mm width x 1.2 mm height in size arid 18 mg weight). I t comprises all passive optical elements necessary for optical trackin g, e.g., a focusing lens, a three-beam grating, an aperture and a beam splitter grating. Three beams were focused to a predetermined spot si ze of 13 mu m at designed intervals of 110 mu m on a disk surface and the reflected beams were successfully guided to photodiodes. This conf irms that the application of the planar optical technique is very usef ul for realizing a compact and light optical sensor.