Optically differentiating and adding passive ring laser gyroscope

摘要

Disclosed herein is an improved passive ring laser gyroscope with two systems: common mode and differential mode error systems. The common mode error system modulates counter propagating coherent radiation. The modulated light from a common source is split at a beam splitter before the reasonator cavity and then optically recombined at the same beam splitter for further propagation to an electronic detecting and demodulation servo system. The resulting electronic error signal is used to adjust the ring resonator and the laser so that the frequency output of the coherent radiation of the laser is substantially equal to the resonance frequency of the ring resonator. The differential mode error system optically substracts counter propagating radiation signals emanating from the resonator cavity to form a differential error signal that is detectable by an electronic detector for further processing by demodulation. This output signal is used to servo and drive acousto-optic modulating frequency shifters, one for each counter propagating radiation of the ring resonator. The difference between the frequencies at which the acousto-optic modulators are driven is made equal to the difference between the frequencies of the counter propagating radiation of the ring resonator. In this manner a reading of the difference of the frequencies driving the two acousto-optical modulators provides a beat signal which is directly translatable to a reading indicating the rate of rotation of the gyroscope.