Showing papers on "Ring laser gyroscope published in 2002"

Method of joining mirrors to ring laser gyro block assemblies

Abstract: A method of attaching at least one component to a ring laser gyro block. The method may include positioning the component so that a mounting surface of the at least one component is substantially parallel to a mounting surface of the ring laser gyro block and applying a fluid adhesive to the exposed interface of the mounting surface of the at least one component and the mounting surface of the ring laser gyro block. The method also includes allowing the fluid adhesive to harden.

Gyroscope with at least one rotation sensing element and detector of sagnac-shifted frequencies

Abstract: A monolithically integrated semiconductor laser rotation sensor/gyroscope that includes at least two isolated, nonsynchronized semiconductor lasers; at least one being unidirectional and at least a further one being either a straight-line laser or a second unidirectional ring laser configured to propagate lasing light waves in the direction opposite to the first unidirectional ring laser; semiconductor directional waveguide couplers; a semiconductor Y-junction mixing region; and a semiconductor photodetector. Evanescently outcoupled signals are routed to a photodetector for detection of the Sagnac shifted frequencies to discern a beat frequency resulting from rotation of the chip structure. The straight-line semiconductor laser serves as frequency reference insensitive to rotation. Directing, filtering, and radiating unwanted reflections or backscattered light to highly absorbing regions is carried out with waveguide coupler designs and nonreciprocal couplers and filters.

Mechanical Dither Design for Ring Laser Gyroscope

Abstract: The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) by the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference and an angular increment is not detected. This problem can be overcome by the mechanical dithering. The purpose of the mechanical dithering is to suppress the dead band, oscillate the monoblock about the rotation axis and add an external rotation rate. This paper presents the theoretical considerations of the mechanical performances of dither on the basis of the loading condition and angular characteristics due to the piezoelement deformation and the validity of theoretical equations are compared through FEM (Finite Element Method) simulations.

Monolithically integrated semiconductor unidirectional ring laser rotation sensor/gyroscope

Abstract: A monolithically integrated semiconductor laser rotation sensor/gyroscope that includes at least two isolated, nonsynchronized semiconductor lasers; at least one being unidirectional and at least a further one being either a straight-line laser or a second unidirectional ring laser configured to propagate lasing light waves in the direction opposite to the first unidirectional ring laser; semiconductor directional waveguide couplers; a semiconductor Y-junction mixing region; and a semiconductor photodetector. Evanescently outcoupled signals are routed to a photodetector for detection of the Sagnac shifted frequencies to discern a beat frequency resulting from rotation of the chip structure. The straight-line semiconductor laser serves as frequency reference insensitive to rotation. Directing, filtering, and radiating unwanted reflections or backscattered light to highly absorbing regions is carried out with waveguide coupler designs and nonreciprocal couplers and filters.

Photonics True-Time-Delay Unit for Phased-Array Antenna Using Multiwavelength Fiber Laser Based on a Sagnac Interferemetric Filter

Abstract: A photonics true-time-delay system for phased array beamforming using a chirped grating-based time-delay element and a novel multiwavelength erbium-doped fiber ring laser source employing a Sagnac filtering mirror is proposed. The Sagnac filtering mirror consists of a polarization maintaining directional coupler and two pieces of polarization maintaining fibers. The lasing wavelength and number are determined by properly adjusting the polarization controller within the unidirectional ring cavity and are very stable. A chirped-grating-based true-time-delay system using the proposed laser source is constructed and demonstrated experimentally.

Effect of Mirror Misalignments on Optical Ray Path In a Ring Resonator

Abstract: The operating principal of a ring laser gyroscope depends on the phase difference for the counter-propagating waves within a closed path. The reflecting mirrors mounted on the monoblock form the traveling waves. The manufacturing accuracy of the monoblock influences the traveling path of ray, the sensitivity of laser resonator for misalignments, and diffraction losses. A 3 $\times$ 3 ray transfer matrix was derived for optical components with centering and squaring errors in a ring resonator. The matrix can be utilized to predict the optical ray paths on the basis of the manufacturing errors of the monoblock as well as the misalignment of mirrors. Then the distance and orientation (o. slope) at the arbitrary plane inside the resonator along the ideal optical path can be calculated from the chain multiplication of the ray transfer matrix for each optical component in one round trip. We also show that the counter-propagating rays In a ring resonator with errors does not coincide in each round trip, which results in gain difference between two beams, and how these errors can be adjusted through the alignment procedure. Finally this 3 $\times$ 3 ray matrix formalism can be used to calculate the beam size and its displacement from the optical axis and the deviation at the diaphragm.

Experimental research on the diode-pumped solid-state ring laser

Abstract: The experimental research on diode-pumped solid-state ring laser (DPSSL) is reported in this paper. The research target is to develop a new style optical gyroscope. The ring cavity is a plane, 8-shape 4-mirror laser resonator. Nd:YVO4 crystal is exploited as a laser media which is longitudinally pumped by a 2w laser diode. An optical delay path attached to the cavity is composed of a beam splitter and a prism. The bidirectional traveling waves partly output from one of the flat mirror and one directional beam interferes with the other on a photo detector with optical delay. The resonator design is discussed; the pump power threshold is about 600mW. We obtain the bidirectional continuous TEM00 mode outputs and their interfering pattern. In the experiment, Sagnac effect is watched, which indicates that the DPSSRL can be used as optical gyroscope.

Simulation of characteristic of comb-gimbal micromachined gyroscope

Abstract: A novel micromachined comb-gimbal gyroscope is presented, which is excited by electrostatic forces and its Coriolis acceleration induced torsional motion is read out capacitively. Since electrostatic comb driving and DRIE (deep reactive ion etching) technology are adopted, the large driving amplitude and higher sensitivity of the gyroscope can be achieved. Driving mode and sensing mode working in different planes may prevent mechanical coupling. Characteristic analysis results obtained from simulation show that when the driving mode frequency equals the sensing mode frequency, the gyroscope may achieve maximal sensitivity. Then according to the matching of the driving mode frequency and detection mode frequency, the structure dimensions of the gyroscope are optimized using the finite element method (FEM). Finally, an equivalent circuit model of the gyroscope is derived, which is available for detection oscillating properties analysis and also enables the simulation of the sensor with the interfacing electronics.

Measuring system, for horizontal or vertical drilling, comprises measuring unit with fibre optic or ring laser gyroscopes, microelectromechanical system or tempo sensor

Abstract: A measuring system for a drilling arrangement comprises a measuring unit (10) with sensors and a means for moving the unit along a borehole. The sensors include at least one of the following - a fibre optic gyroscope, a ring laser gyroscope, a microelectromechanical system and a tempo sensor. An Independent claim is also included for a method of measuring a distance between two points in a borehole. DGPS (RTK) readings are taken at both points in the borehole, a measuring unit with an optical gyroscope is moved from the first point to the second point, and the positions of locations between these two points are determined by dead reckoning based on signals generated by the gyroscope. Dead reckoning is then used to determine a position for the second point, the difference between the DGPS (RTK) reading and the dead reckoning calculated position for the second point is calculated, and this difference is used to correct the positions of the locations between the first and second points.

Semiconductor side pumping solid laser gyroscope and its electrooptical modulation method

Abstract: The present invention relates to the structure design of semiconductor side pumping solid laser gyroscope. The gyroscope consists of mainly circular cavity reflector combination, gain medium, pumpingunit, electrooptical crystal, beam splitting plate, optical delayer and readout circuit. It features its side pumping comprising focusing and coupling lens, semiconductor laser array and temperature controller. The present invention has less heat stress, triangular circular cavity, without negative area and structure similar to that of gas laser gyroscope. It has two electrooptical crystals in the same parameters for electrooptical jetter and uses sinusoidal waves with 180 deg phase difference for modulation to reduce blocket area. The present invention has advantages of small volume, stable work and long service life, and may be used widely in inertial navigation, inertial guidance, inertial measurement and other inertial technology.

Optimization of dither amplitude and frequency of RLG

Abstract: Proper selection of the dither amplitude and frequency of the ring laser gyroscope (RLG) influences the effect of dither bias directly. In order to reduce RLG lock-in effectively, the dynamic lock-in width is obtained by deducing the basic RLG input-output equation in the article. The corresponding optimization model is based on the purpose of reducing the influence of dynamic lock-in. The result of the optimization shows that it is necessary to enlarge dither depth to reduce the nonlinear influence. When dither depth is large enough, there is no evident effect on the reduction of dynamic lock-in by enlarging it further. However, dynamic lock-in may be reduced to zero by modulating dither depth locally with very small value according to the results of optimization. Some constructive conclusions are obtained at the end of the article.

Frequency characteristic of a uniformly rotating laser gyroscope with differently amplified counterpropagating waves

Abstract: It is shown that the frequency characteristic of a uniformly rotating laser gyroscope with differently amplified counterpropagating waves is described by the expression containing components that are commuting or noncommuting with respect to the angular velocity.

A Digital Frequency-Stabilization Method for Laser Gyroscope

Abstract: A digital method for the frequency stabilization of laser gyroscope is described. A digital circuit for the frequency stabilization control of the laser, including the interrelated software, is designed and developed. The experimental results show that the digital method is feasible and better than the analog one.

Influence Analyses of Resonator Parameters on Laser Gyro Performance

Abstract: The resonator parameters of laser gyro can directly influence its performance. The scale rule of laser gyro is given and analyzed. The effects of the size tolerance of discharge tube and the resonator diaphragm on laser gyro are investigated. The design rules of discharge tube and diaphragm are given. The formula of back-scattering of the diaphragm is induced. These are valuable to the design of laser gyro.

Initial alignment of laser gyroscope inertial navigation system with disturbances

Abstract: The initial alignment of laser gyroscope inertial navigation system (LINS) for land vehicles is difficult when disturbance are present, for example when the motor is running on or people are walking in the vehicle The Kalman filter alignment technique was developed for signal analyses of the LINS inertial instruments The observation signals were pre processed to reduce the interference, then the Kalman filter algorithm was improved to increase the stability The experimental results show that this technique effectively increases the alignment accuracy with disturbances

CEL gyroscope with injected squeezed vacuum

Abstract: It is shown that the injection of a squeezed vacuum into a correlated emission ring laser gyroscope enhances the sensitivity of the device. In particular, it is demonstrated that if the phase of the injected squeezed vacuum is chosen appropriately, then the output is squeezed in the phase quadrature. This may lead to complete suppression of the shot noise in the signal.

Differential surface acoustic wave IDT gyroscope

Abstract: This paper presents the design and experimental evaluation of a gyroscope based on differential design of a surface acoustic wave (SAW) resonator and a sensor on a piezoelectric substrate. The resonator is divided into two halves, one with metallic dot arrays and other without any metallic dots. Standing waves are formed inside both cavities. The particles at the antinodes of the standing wave pattern experience large amplitude of vibration that serves as the reference vibrating motion for this gyroscope. The metallic dots strategically positioned at the antinode locations experience Coriolis force due to rotation and acoustically amplify the magnitude in the orthogonal direction. However, the other half of the resonator cannot generate any secondary SAW. A wideband SAW sensor arranged orthogonal to the SAW resonator picks up these two secondary SAWs and is fed to a differential amplifier. Any drift in the gyroscope signal can be completely eliminated by this novel design. The performance of this 74.2‐MHz gyroscope shows very high sensitivity and dynamic range, which is ideal for many commercial applications. Unlike other MEMS gyroscopes, this gyroscope has a planar configuration with no suspended resonating mechanical structures, thereby being inherently robust and shock resistant.

Current control biasing to protect electrode seals of a ring laser gyroscope

Abstract: Current control biasing of a ring laser gyroscope is employed to protect electrode seals. A frame (214) of a ring laser gyroscope has more than one electrode (206, 212) attached to it. An electric field is created between the electrodes during the operation of the gyroscope, which causes ions in the frame to migrate towards a lowest electrical potential. Electrode seals (210) are located between the electrodes and the frame. By providing a positive power supply voltage (Vs) and connecting the current control (202) to the non-ground side of the power supply (204), the mounting structure (208) may be at the lowest electrical potential. The ions will then migrate towards the mounting structure, which significantly reduces migration to the electrodes.

Lock-in frequency improvement of ring laser gyro using a low - scattering mirror

Abstract: For the improvement of the lock-in frequency of a ring laser gyro, a low-scattering mirror was employed in the laser resonator. A super-polishing technique produced fine mirror substrates of less than 1-A-rms-roughness. The mirror coating using an ionbeam sputtering technique reduced the scattering loss to less than 30 ppm. As a result of the mirror scattering enhancement of the ring laser, the lock-in frequency of the gyro was improved up to about 0.1 deg/sec.

Dynamics of a Micro Three-Axis Ring Gyroscope

Abstract: In this paper, we analyse and present mechanical dynamic characteristics of a micro-machined vibrating silicon ring gyroscope which can measure angular velocities about three orthogonal axes. The ring gyroscope has a ring connected to the gyroscope main body by support-ligaments which are arranged with cyclic symmetry. The natural modes of its vibration can be distinguished into the in-plane motion and the out-of-plane motion which are coupled by the gyro-effect due to the rotation of the gyroscope main body. The equations of motion, the response to angular velocities, and the relationships between the natural modes of vibration are derived and compared with the previous studies for the design of a micro three-axis ring gyroscope.