Abstract: An RLG OPTICAL NOISE INJECTOR places a random signal on a PZT driving one mirror controlling the optical path length (OPL) of a ring laser gyro (RLG) and the negative of the signal on a PZT driving a second mirror controlling the OPL. The OPL is therefore maintained constant while injecting random noise into the phase of the counterpropagating beams to avoid dynamic lock-in. Static lock-in may also be avoided by superposing an oscillatory signal on the random signal fed to the first PZT and the negative of the oscillatory signal on the random signal fed to the second PZT.

Abstract: A self-erecting tiltmeter includes a vertical seeking assembly suspended on a gimbals within a housing which contains a viscous fluid. Portions of the assembly outer surface spherically match corresponding portions the housing inner surface, leaving a gap or gaps across which the fluid may transfer tilts to the vertical seeking assembly. Different portions may have different radii or curvature. The fluid is sufficiently dense as to reduce the weight of the assembly on the gimbals. The vertical seeking assembly includes a conductivity difference bubble sensor assembly, signals from which are transmitted to the exterior of the housing through wires which pass through the pivots of the gimbals. An annulus of closed cell neoprene accommodates thermal expansion of the fluid.

Abstract: A liquid filled pathlength control device is disclosed that responds to a pathlength control signal for adjusting the pathlength in an optical signal process dependent on coherent light. The liquid filled pathlength control device has a housing containing a liquid filled chamber. The liquid filled chamber has an extendable wall having an inner surface subject to pressure from the liquid. An external mirrored surface on the extendable wall is inserted into and the light path. The liquid filled chamber has a deformable wall having an inner surface subject to the pressure of the liquid and an external surface. A displacement transducer is coupled to the deformable wall and responds to a control signal of a first polarity to deflect the internal surface of the deformable wall in a first direction to increase the pressure of fluid in the chamber.