Gas bypass for bias reduction in laser gyrescopes

Abstract

A ring laser gyro, having: an envelope for an optically resonant cavity having a gain bore section, the envelope containing an active gas medium. The envelope contains electrically energizable electrode means having at least two electrodes at electrode locations within the envelope for establishing an electrical discharge in an active gas medium between the electrode locations. The electrical discharge excites a pair of light beams along a lasting path between the electrode locations. The light beams counterpropagate in the optically resonant cavity. The envelope is coupled to means for generating an output signal for the gyro by measuring a difference in the frequencies of the light beams. The active gas medium has an axial current driven gas flow and a return gas flow induced by the electrical discharge, the resultant gas flow contributing to bias errors in the output signal. The envelope also comprises a gas bypass cavity adapted to pneumatically couple the electrode locations along the gain bore. The gas bypass cavity has a length adapted to inhibit ionization of the gas medium within the bypass cavity and also has a cross-section selected to reduce axial current driven gas flow between the respective electrode locations. The gas bypass cavity reduces the tendency of the ring laser gyro to exhibit bias errors by providing an alternate path for the return gas flow. The gas bypass cavity also operates to reduce the differential pressure between the respective electrode locations. The gas bypass cavity is equipped with a means for controlling the return gas flow.