Pulse generating apparatus

Abstract

A three-channel optical shaft angle encoder has two channels for encoding the incremental angle and the direction of rotation of a shaft. A third channel provides a synchronizing index pulse for encoding the absolute position of the shaft once per revolution. The encoder has an emitter module containing three high irradiance LED emitters and integral truncated collimating lenses for producing three closely spaced collimated light beams, one beam for each channel. These light beams are modulated as a function of the relative angle between a code wheel coupled to the shaft and a phase plate fixedly mounted to the body of the encoder. The modulated light beams are received by a detector module having beam splitting truncated and siamesed lenses positioned to split each of the closely spaced light beams and to focus each of the split beams onto a photo detector pair. The photo diode pairs are coupled to balanced hysteretic optical comparators which provide analog and digital output in response to the position and direction of rotation of the shaft.