Photodynamic pickoff system for a free-rotor gyroscope

Claim 1

Photodynamic pickoff means for spatial orientation responsive devices and the like of the type having a stator member, a spinning rotor member, and means for supporting the spinning rotor member to permit relative angular movement between the spin axis of the rotor member and a reference axis of the stator member in at least a first plane in which said axes lie, comprising means mounted on said stator member for producing an incident light beam coaxial with said stator reference axis and directed toward one of the spin axis poles of the rotor member; biplanar mirror means mounted on said rotor member at said one spin axis pole thereof for reflecting said incident light beam To form a reflected light beam which lies at an acute angle with respect to said rotor spin axis, said biplanar mirror means having first and second light reflecting surfaces respectively lying at different acute angles with respect to a line perpendicular to said indent light beam, so that rotation of the rotor member about said spin axis causes said reflected light beam to rotate about said axis and thereby trace a closed path, whereby the line of movement of the center of said closed path represents the angular deviations between said rotor spin axis and said stator reference axis in said first plane; and photoelectric transducer means mounted on said stator member in the path of said reflected light beam and symmetrically disposed about said reference axis, said transducer means being provided with an aperture through which said incident light beam passes and having at least two independently operable portions for actuation by said reflected light beam, which portions are disposed on opposite sides of a dividing line which is perpendicular to the said line of movement of the center of the closed path and which bisects the closed path when the rotor spin axis coincides with the stator reference axis, so that each of said transducer portions produces an output signal in the form of a series of output pulses having a pulse repetition rate corresponding to the rotor spin speed and a pulse width representing the angular deviation between the rotor spin axis and the stator reference axis in said first plane, whereby the magnitude and sense of the differential between the pulse widths of the two series of output pulses respectively represent the magnitude and direction of the angular deviation between the rotor spin axis and the stator reference axis in said first plane.