Optical scanning transducer

Claim 1

Optical scanning apparatus, comprising: (a) a drive means for driving an optical element configured to receive a radiated beam to be directed by the optical element; (b) programmable electrical circuit means for controlling the drive means to produce an angular displacement of the optical element; (c) angular capacitive positioning means coupled to the drive means for detecting the angular position of the optical element and generating a feedback output signal to the programmable electric circuit means that is proportional to the angular position; (d) the angular capacitive positioning means is generally comprised of a variable capacitor including: a capacitive rotor disc having a plurality of wedge shaped conducting surfaces equally spaced thereon and connected to the shaft of the dc motor generally perpendicular to the axis of rotation; a capacitive stator disc having twice as many equally spaced wedge shaped conducting surfaces as the rotor disc spaced axially parallel to the rotor disc and having an air gap therebetween for capacitive coupling; adjusting means for adjusting the air gap for changing the capacitive coupling of the variable capacitor; and programmable excitation means for providing a sinusoidal input voltage to the capacitive rotor and stator combination including a bridge circuit and synchronous demodulator for providing a DC output proportional in sign and polarity to the angular displacements of the discs from a null position.