Optical sensor for servo position control

摘要

This optical sensor has cylindrical symmetry and is comprised of a semiconductor light source/light detector combination and an optical element comprising a single lens, where the sensor is particularly suitable for uses in accurate position detection in data recording systems. In a preferred embodiment, the light source is a forward-biased p-n junction, while the light detector is a reverse-biased p-n junction located below the light source and coaxial therewith. Light from the source is directed to a point on a data recording medium and the light reflected therefrom passes through the light source to the light detecting junction. The ac signal corresponding to the reflected light is an indication of the position of the recording head with respect to the data storage medium.