Actuator with an optical position sensor using a variable magnetic field

摘要

An actuator having an optical position sensor is disclosed. The sensor remotely provides via a single optic fiber light having two spectral frequencies of about equal intensities to two inversely acting linear optical attenuators that attenuate light in response to the intensity of a magnetic field varied in relation to the movement of the actuator. The attenuated light from each attenuator is filtered producing two attenuated light signals of the two frequencies that are combined in another single optic fiber and then processed into voltages indicative of their intensities. The position of a moving object attached to the attenuators is derived from the difference of the two signals relative to their combined value, minimizing errors associated with obstructions the optical couplings. The attenuators may be orthagonal strips that slide in unison in slots in an elongated rod containing light transmitters and receivers. Light transmittance of the strips varies along their length. The strips are joined as a cartridge that slides within the rod.