An integrated high-resolution optical angular displacement sensor

Abstract

The sensor consists of a rotating element with reflective patterns fabricated onto it and a stationary part with optical detectors and readout circuitry, integrated in a standard BiFET IC process. High-resolution absolute angular position measurement is realized by combining the information of a high-resolution incremental analog sensor with that of a low-resolution absolute binary sensor. The high-resolution sensor part is implemented by a reflective zigzag pattern on the rotor and a position-sensitive device (PSD) on the stator. The low-resolution sensor part comprises a binary reflective code pattern on the rotor and a photodiode array on the stator. Angular displacement causes the code on the photodiode array to alternate and the reflected light spot on the PSD to move over the full length of the PSD in between each code transition. The sensor permits a contactless angular measurement over the full range of 360 degrees , without blocking at full scale. The sensor is insensitive to electric and magnetic fields and can be placed radially at any place on a rotating shaft.<>