Showing papers on "Ring laser gyroscope published in 1980"

Laser gyro at quantum limit

Abstract: We show that a certain fundamental limit applies to the accuracy of all optical rotation sensors which use laser light as a probe. We derive this fundamental rotation-rate uncertainty from the Heisenberg uncertainty relations and Glauber's minimum uncertainty states. The same relationship is obtained from a spontaneous-emission noise formulation. We present experimental data on a (nondithered) four-frequency ring laser gyroscope for which this limit is attained.

Multioscillator laser gyros

Abstract: The two-mode ring laser gyro is reviewed. Standard bias and dither techniques are discussed that alleviate the mode locking encountered at low rotation rates. The four-mode DILAG (differential laser gyro) and its magnetic field extension the ZLAG (Zeeman laser gyro) are defined and analyzed. These devices contain two coresident ring lasers of opposite helicity and may have no moving parts. The mode-locking problems are overcome with the use of various biases that cancel out in the rate signal. A semiclassical analysis is reviewed that gives the electric field amplitudes and frequencies of the four modes in the presence of multilevel atoms, cavity anisotropy, and backscattering. It is shown that without mode-locking contributions, laser operation can be approximated very well by four independently oscillating modes. The Zeeman effects are considered. Novel scalar four-mode schemes are also discussed that circumvent the mode-locking problem.

Pathlength controller for a ring laser gyroscope

Abstract: A method and apparatus for pre-setting the position of a piezoelectric actuator used in controlling the path length of the laser beam of a ring laser gyroscope is disclosed. The path length controller of this invention minimizes the necessary rectilinear motion of the actuator by presetting the actuator position according to the environmental or start-up temperature of the ring laser gyroscope to anticipate changes in the laser path length resulting from changes in the environmental temperature and/or self heating effect when the gyroscope is in operation.

Phase-locked loop laser gyroscope system

Abstract: A very high resolution laser gyroscope system having a phased-locked loop operatively coupled to one or more frequency difference outputs from a laser gyroscope cavity. Waves of at least four frequencies propagate around the gyroscope cavity, with output signals being formed having a frequency equal to the difference between the frequencies of wave pairs. In one set of embodiments of the invention, the frequency difference signal for one wave pair is phase-locked to an external reference source. A signal applied to a Faraday rotator bias coil provides the frequency shifting of the wave pairs necessary to achieve phase lock. The amplitude of the signal applied to the Faraday bias coil provides a highly precise measure of the rate of rotation. In another set of embodiments of the invention, one or more of the wave pair frequency difference signals are coupled as inputs to an external phase-locked loop in which a voltage controlled oscillator is followed by a frequency divider of the feedback circuit. In these embodiments, the output of the voltage controlled oscillator provides an output signal which has a frequency in proportion to but many times higher than the frequencies of the wave pair difference signals. In still further embodiments of the invention, the two phase-locked loop techniques may be combined. In all of the disclosed systems, the quantization error normally associated with laser gyroscope output signals is substantially reduced.

Ring laser gyro dither pulse eliminator

Abstract: A ring laser gyro is electromechanically oscillated so that oppositely moving light beams in the gyro do not exhibit an undesirable lock-in effect A piezoelectric transducer mounted in the gyro measures the dither Analog/digital circuitry converts the measurement to digital dither signals A non-compensated beam combiner and photodetector assembly are integrally mounted to the gyro for producing beam frequency outputs from the light beams, indicative of inertial rotation of the gyro The beat frequency outputs and dither signal are input to logic circuitry which eliminates the effect of the dither signal on the beam frequency output signals

Laser gyro dither mechanism

Abstract: An improved laser gyro dither mechanism is shown utilizing a three-spring suspension system which isolates dither vibrational energy generated within the gyro and prevents that energy from passing to the mounting case of the laser.

Laser gyro coupling system

Abstract: This invention relates to a laser gyro coupling system which utilizes a pair of resilient rings located between a plate attached to the laser dither suspension mechanism and the lower surface of a ring laser to form a reservoir for a viscous fluid The coupling system permits the dither suspension mechanism to drive the ring laser at its dither frequency without transmitting stresses to the ring laser due to thermal expansion

Rotation detection by optical fibre laser gyro with easily introduced phase-difference bias

Abstract: An optical system for easy introduction of phase-difference bias to optimise the sensitivity of the optical fibre laser gyro is proposed. The preliminary test set-up has been constructed and tested. A detectable limit of rotation of 8.7×10-4 rad/s has been achieved.

Dual-input fiber-optic gyroscope

Abstract: A fiber-optic gyroscope is operated at maximum sensitivity by supplying two equal-intensity inputs with a specific phase difference to the gyroscope beam splitter. When the beam-splitter outputs have equal intensity, reciprocity requires the Sagnac interferometer to be at quadrature. A sensitivity of ∼0.93 rad−1 is demonstrated with a minimum-detectable rotation rate of 0.4 deg/sec.

Bending actuator for ring laser gyroscope

Abstract: Bias shift caused by distortion of a ring laser gyroscope block is corrected by bending the block Electromechanical bending devices may be piezoelectric crystals adherently attached to the block and resposive to voltage derived from distorting influences

Optically biased laser gyro.

Abstract: We describe a four-mode ring laser that exhibits none of the mode-locking characteristics that plague laser gyros. This laser is characterized by a bias that changes sign with a change in the direction of rotation and prevents the counterpropagating modes from locking. A theoretical analysis explaining the experimental results is outlined.

Laser gyro oscillation suppression

Abstract: A laser gyroscope having a multi-frequency ring laser resonator containing a gas laser energized by electric discharge through a gaseous laser medium from two anodes to a common cathode positioned outside the lasing passage and communicating therewith through a narrow bore having a nonuniform constant magnetic field applied to the gaseous discharge in said bore to suppress high frequency gas discharge oscillations in the laser.

Ring laser revolution rate meter with optical switch - alternately passes in opposite directions, for if operation, and overcomes lock-in effect

Abstract: The laser gyroscope or ring laser revolution rate measurement device contains an electromagnetic radiation amplifying medium in a closed beam path traversed in opposite directions by electromagnetic beams, ie laser beams. It is designed to overcome the lockin effect which tends to synchronise the two beams to a common frequency at low revolution rates. It thus enables low revolution rate measurement. An optical switching device placed in the beam path is switched alternately for passage of a beam in one direction only. It is non-reciprocally controlled with time so that two wave packets pass round the beam path in opposite directions and alternately amplified. The beam path can be an optical wave conductor wound into a loop. In one arrangement two circulators (Z1, Z2) are connected one each at either end of a loop contg., an amplifier (V) and a frequency filler (F), connected between change-over switches (S1, S2).

Measurement of rotation rate using sagnac effect

Abstract: In a Sagnac effect optical fibre gyroscope a commutating switch (SW) is included immediately before the Sagnac coil (C). Operation of the switch synthesises turning the coil upside down. This provides the advantages of producing an a.c. signal in response to a constant rotation rate and in certain arrangements remove a source of systematic error occasioned by drift in optical parameters of unbalanced components.

Laser Inertial Rotation Sensors

Abstract: (1980). Laser Inertial Rotation Sensors. Optica Acta: International Journal of Optics: Vol. 27, No. 4, pp. 445-446.

Ring Laser Gyro - A Status Report,

Abstract: : A general review of laser gyros is presented. Basic concepts of the gas ring laser are reviewed. These include the 'lock-in' phenomena, geometric performance factors, and other problem areas. Various biasing methods to eliminate some of these basic problems are presented. Salient features of the laser gyro which are unique for gyro instruments are shown with data. Various laser gyro design parameters are reviewed with respect to projected performance requirements for various applications. (Author)

New Approaches to Optical Systems for Inertial Rotation Sensing.

Abstract: : The objective of this research program has been to investigate the potential of new fiber optic configurations for inertial rotation sensing so as to extend the sensitivity and stability of such systems In particular, the research has been aimed at the design and construction of reentrant Sagnac systems permitting recirculation of the optical signals There have been two main activities in the program, (1) the design and partial construction of an all-fiber Sagnac rotation sensor eliminating all previously used bulk optical components, lenses, mirrors, prisms, etc Bulk components do not have sufficient precision and impose alignment problems so as to limit the sensitivity and recirculation capability of Sagnac sensors The all fiber design was made possible by the development in this laboratory partially under other contract support of a set of all fiber components, directional couplers, polarizers, and polarization controllers, which have been incorporated in the all fiber design This configuration should provide greatly increased sensitivity and device compactness and ruggedness The second set of activities in the program has been to investigate various limitations on the sensitivity (minimum detectable rotation rate) of Sagnac systems One such limitation is the extraneous noise known to exist in all Sagnac systems We have found particularly, that the effects of Rayleigh backscattering from fiber inhomogeneities of phase detection in Sagnac systems, as one of the principle limitations on sensitivity

Laser Gyro Theory Extension

Abstract: : Three investigations have been completed under the contract entitled 'Laser Gyro Theory Extension,' as follows: (1) The accuracy of the Zeeman laser gyro (ZLAG) theory was tested by comparing its predictions with experimental results. (2) Other multioscillator approaches to solving the lock-in problem have been investigated. (3) Two earthbound experiments to test general and special relativity theories were designed, based on the Sagnac interferometer. (Author)

Fourrmode ring laser

Abstract: A ring laser gyroscope system is provided in which four frequencies of oscillation are allowed to simultaneously propagate within the ring laser cavity, with two modes propagating in each direction. Separation of the resonant frequencies is accomplished through reciprocal, nonreciprocal, and anisotropic optical effects within the laser path, plus Zeeman effect produced by a magnetic field in a predetermined intensity range over the laser gain plasma. The magnetic field substantially parallel to the laser path over the gain medium reduces the effects of hole burning or source depletion when the amplitudes of the field is within a predetermined intensity range to allow frequencies of the four modes to be spaced closer together. The system employs cavity length control circuitry to optimize system output. Rotation of the system results in frequency changes which are detected and processed to yield inertial rotation information.