Showing papers on "Ring laser gyroscope published in 2007"

Optical gyroscope based on a coupled resonator with the all-optical analogous property of electromagnetically induced transparency

Abstract: The electromagnetically induced transparency- (EIT)-like phenomenon, called coupled-resonator-induced transparency (CRIT), could occur through a classical mean in a coupled resonator structure, due to classical destructive interference. We propose to utilize this property to construct a miniature highly sensitive gyroscope. We analyze the Sagnac effect in the CRIT structure and point out that the Sagnac phase shift contributed by the whole structure is notably enhanced due to its highly dispersive property. An explicit expression of the phase shift is derived and discussed. To realize the implementation of the CRIT-structure-based gyroscope, issues that ought to be considered are fully discussed here, such as the fabrication possibility, linewidth, shot-noise-limit sensitivity, and integration.

Bidirectional operation and gyroscopic properties of passively mode-locked Nd:YVO4 ring laser

Abstract: A simple LD-end-pumped, passively mode-locked Nd:YVO4 ring laser with bidirectional outputs was demonstrated, and the gyroscopic properties of the ring laser was studied. The laser was continuous wave mode-locked by use of a semiconductor saturable absorber mirror (SESAM), and both clockwise and counter-clockwise outputs are stable laser pulse trains with pulse duration of 64 ps. The continuous wave mode-locking was obtained under pump power as low as 540 mW. The average output power is 50 mW for the counter-clockwise laser and 52mW for the clockwise laser under pump power of 1378 mW. The whole slope efficiency of the ring laser is about 9.4%. The two output pulse trains of the ring laser were combined to study its gyroscopic properties. The beat frequency of the pulsed solid-state laser gyro versus the rotation rates follows the Sagnac formula. The laser gyro has a large dead band of 6-8 dec/s, which was believed to be caused by the long pulse duration and the colliding of the opposite pulses on the SESAM.

Oscillation regimes of a solid-state ring laser with active beat-note stabilization: From a chaotic device to a ring-laser gyroscope

Abstract: We report an experimental and theoretical study of a rotating diode-pumped Nd-YAG ring laser with active beat-note stabilization. Our experimental setup is described in the usual Maxwell-Bloch formalism. We analytically derive a stability condition and some frequency response characteristics for the solid-state ring-laser gyroscope, illustrating the important role of mode coupling effects on the dynamics of such a device. Experimental data are presented and compared with the theory on the basis of realistic laser parameters, showing very good agreement. Our results illustrate the duality between the very rich nonlinear dynamics of the diode-pumped solid-state ring laser (including chaotic behavior) and the possibility to obtain a very stable beat note, resulting in a potentially new kind of rotation sensor.

Drift error analysis caused by RLG dither axis bending

Abstract: In this paper, a drift error equation caused by the flexure of ring laser gyroscope (RLG) mechanical dither is derived for analyzing the effect on system performance in the presence of input acceleration. To separate the effects of dithering rate motion and vehicle rate motion, the flexure error is classified as sensor level error if the sensing axis coincides with the dithering axis and as system level error if the two axes do not coincide. The drift error is then derived by using the relationship between gyro output and the rotation vector. These equations show that RLG-based INS attitude error caused by the flexure is directly proportional to time, the amount of input acceleration and the dynamic frequency of the vehicle.

Random vibration analysis of mechanically dithered ring laser gyroscope

Abstract: In order to research the performance of mechanically dithered Ring Laser Gyroscope(RLG) against the dynamic environment,the random vibration analysis is presented.The analysis method of structural random vibration response by the base excitationis described.The finite element model of mechanically dithered RLG is established and its modal analysis is performed by the finite element software ANSYS.It has been proved by the experiments that the model is reasonable and accurate,and the calculate error is less than 7%.The responses on axial and transversal random vibrations of mechanically dithered RLG are analyzed with the finite element model and the experiments and analysis results are compared.By analyzing the Power Spectrum Density(PSD) of acceleration response,the random vibration characteristic of mechanically dithered RLG is assessed.By analyzing the weakness of the present structure,an anti-vibration suggestion is put forward,which is useful to improve the structure design and reform for the further development of RLG.

Differentiel birefringent fiber frequency-modulated continuous-wave sagnac gyroscope

Abstract: Disclosed is a differential birefringent fiber frequency-modulated continuous-wave (FMCW) Sagnac gyroscope for measuring rotation velocity. The gyroscope uses a 90°-twisted single-mode birefringent fiber coil as a double unbalanced fiber-optic FMCW Sagnac interferometer, and uses the phase difference between the two beat signals from the fiber coil to determine the rotation velocity. This gyroscope can eliminate the nonreciprocal phase drift and provide a doubled resolution.

Search for Frame-Dragging in the Vicinity of Spinning Superconductors

Abstract: High-resolution accelerometer and laser gyroscope measurements were performed in the vicinity of spinning rings at cryogenic temperatures. After passing a critical temperature, which does not coincide with the material's superconducting temperature, the angular acceleration and angular velocity applied to the rotating ring could be seen on the sensors although they are mechanically de-coupled. A parity violation was observed for the laser gyroscope measurements such that the effect was greatly pronounced in the clockwise-direction only. The experiments seem to compare well with recent independent tests obtained by the Canterbury Ring Laser Group and the Gravity-Probe B satellite. All systematic effects analyzed so far are at least 3 orders of magnitude below the observed phenomenon. The available experimental data indicates that the fields scale similar to classical frame-dragging fields. A number of theories that predicted large frame-dragging fields around spinning superconductors can be ruled out by up to 4 orders of magnitude.

Solid-state laser gyro with a mechanically activated gain medium

Abstract: The field of the invention is that of solid-state ring lasers or laser gyros. The laser gyro according to the invention comprises at least one optical cavity in the form of a ring and a solid-state amplifying medium which are designed so that two counterpropagating optical modes can propagate in opposite directions one with respect to the other inside said optical cavity and pass through the amplifying medium, said amplifying medium being coupled to an electromechanical device imparting on said amplifying medium a periodic translational movement along an axis substantially parallel to the direction of propagation of said optical modes. Thus, the population inversion grating, written by the standing wave into the amplifying medium, which disturbs the nominal operation of the laser gyro, is greatly attenuated.

Experimental investigation of Sagnac beat signals using semiconductor fiber-optic ring laser gyroscope (S-FOG) based on semiconductor optical amplifier (SOA)

Abstract: We are conducting research to confirm the performance of a semiconductor fiber-optic ring laser gyroscope (S-FOG) featuring a semiconductor in its laser cavity. This S-FOG consists of a semiconductor optical amplifier (SOA) as a gain medium, a polarization-maintaining fiber to make a ring cavity, and a directional coupler to take part of the optical power out of the cavity. One of the advantages of the S-FOG is the adaptability of the laser cavity, which allows us to examine many cases of S-FOG applications easily. In the first case, we observed that the S-FOG generated Sagnac beat signals whose peak frequency was proportional to the rotation rate when it rotated. In the second case, we changed the area surrounded by the ring cavity (the fiber) and its perimeter and maintained a near-fixed oscillation wavelength of the ring laser. In this case, all of our experimental results were in good agreement with theoretical calculations, within a few percent. In the third case, we changed the oscillation wavelength and fixed the shape of the ring cavity. In this case, our results were also in good agreement with theoretical calculations. In the fourth case, we examined the Sagnac beat spectrum generated by the S-FOG in detail. The linewidth of the Sagnac beat spectrum increases as the area bounded by the optical path in the ring cavity becomes smaller, or as the length of the cavity becomes shorter. Our experimental results show that the S-FOG works as a gyro and that there exists practical potential for a semiconductor ring laser gyro.

Precise MEMS Gyroscope with Ladder Structure

Abstract: We report a precise MEMS gyroscope with a 'ladder structure', which was designed to reduce acceleration sensitivity, temperature dependence of sensitivity, and offset drift. This gyroscope has four masses linked by two parallel straight beams, and each mass oscillates in opposite directions in a driving mode. A sensor module using the fabricated gyroscope shows low acceleration sensitivity and stable characteristics in the presence of temperature changes. This gyroscope will be useful for car navigation systems, for example, where high precision is necessary.

Gyroscope mode shift detection and scale factor compensation

Abstract: A method for maintaining measurement accuracy of a ring laser gyroscope is disclosed. The method involves periodically measuring a path length control voltage in the ring laser gyroscope over a prescribed temperature range. When a first path length controlled by the path length control voltage deviates at least one wavelength from a nominal path length, the method detects the change in the path length as a mode shift. For each mode shift, the method applies a path length correction to maintain the first path length at a target path length over the prescribed temperature range. The method can apply a correction to a measurement signal output of the ring laser gyroscope by adjusting a calibrated scale factor depending on an actual integer number of wavelengths achieved during a mode shift.

Search for Frame-Dragging-Like Signals Close to Spinning Superconductors

Abstract: High-resolution accelerometer and laser gyroscope mea- surements were performed in the vicinity of spinning rings at cryo- genic temperatures. After passing a critical temperature, which does not coincide with the material's superconducting temperature, the an- gular acceleration and angular velocity applied to the rotating ring could be seen on the sensors although they are mechanically de- coupled. A parity violation was observed for the laser gyroscope measurements such that the effect was greatly pronounced in the clockwise-direction only. The experiments seem to compare well with recent independent tests obtained by the Canterbury Ring Laser Group and the Gravity-Probe B satellite. All systematic effects ana- lyzed so far are at least 3 orders of magnitude below the observed phenomenon. The available experimental data indicates that the fields scale similar to classical frame-dragging fields. A number of theories that predicted large frame-dragging fields around spinning supercon- ductors can be ruled out by up to 4 orders of magnitude.

Laser gyro and electronic device using the same

Abstract: A laser gyro of the present invention includes laser light excitation means (a semiconductor laser device 100 ) that excites first and second laser lights propagating in the opposite directions to each other in a circular ring-shaped path (an optical path 40 ), coupling means (optical waveguides 41 and 42 ) for superimposing the first and the second laser lights, and a photodetector for observing an interference signal generated by the superimposed first and second laser lights.

Er-doped fiber ring laser gyroscopes operating in continuous waves

Abstract: A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope (FRLG) operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good linear relation between the beat frequency shift and cavity rotation rate was obtained.

Design of a Novel MEMS IDT Dual Axes Surface Acoustic Wave Gyroscope

Abstract: The configuration of a novel MEMS interdigital transducer (IDT) dual-axis surface acoustic wave (SAW) gyroscope is presented in this paper. There have been an increasing demand for gyroscopes with small size and low cost in military and commercial systems, however rotator gyroscopes, laser gyroscopes, fiber optic gyroscopes, and silicon-based MEMS gyroscopes can't meet the demand. Although the MEMS IDT SAW gyroscope previously is without a suspended structure, it can only detect the angular velocity of one axis, and two gyroscopes of the kind are used to measure the angular velocity of two axes which can be detected by a MEMS IDT dual-axis SAW gyroscope. The configuration and working principles of the gyroscope were explored. The 95.9 MHz gyroscope sample fabricated on the 128° YX-LiNbO 3 substrate was primarily designed.

Research on Principle and Phase of Silicon Micromachined Gyroscope Using for Rotating Carrier

Abstract: The principle and phase picking-up technique of silicon micromachined gyroscope using for rotating carrier is proposed in the paper. Be differ from conventional gyroscope, this one hasn't self-driver part and the configuration is simple. According to the principle of the gyroscope, when the sensitivity axis parallel to the deflexion plan, silicon pendulum will get the biggest Coriolis force, and the output is the peak value of the sine wave; when the sensitivity axis perpendicularity to the deflexion plan, the output is the zero value of the sine wave. So taking the input signal of the gyroscope as the benchmark, we will get the direction of the sensitive axis by comparing the output signal phase in benchmark coordinate. Moreover we can confirm the circumrotating plan and the deflexion direction of the rotating carrier in the space.

Systems and methods for utilizing pulsed radio frequencies in a ring laser gyroscope

Abstract: Ring laser gyroscope that includes a gyroscope block, a radio frequency transmitting device, and a radio frequency energy source. The gyroscope block has at least one discharge bore containing a gain medium, and the radio frequency transmitting device is located within the gyroscope block in proximity to at least one discharge bore and located so as to encompass the discharge bore. The radio frequency energy source is configured to apply a pulsed radio frequency signal to the transmitting device.

Pulse subdivision technique for differential ring laser gyro

Abstract: Error of integer pulse counting method for differential ring laser gyro is analysed in the article.And the pulse subdivision method is brought for- ward,with which the pulse mantissa is accurately measured.Error of the method is also analysed.On the basis of these,data of some type differential RLG are sampled with the pulse subdivision method.Theoretical analysis and experiments show that angular resolution of the pulse subdivision technique is better than 0. 1 are second.

Photonic crystal based rotation sensor

Abstract: A gyroscope having photonic crystals for sensing rotation uses the Sagnac effect to determine angular motion. The gyroscope comprises a photonic crystal capable of guiding counter-propagating light beams in a closed path. A light source, coupling, and detection apparatus permits detection of phase changes between the counter-propagating beams, thereby permitting measurement of angular rotation. The photonic crystal comprises a periodic structure of pillars and voids which creates a photonic bandgap waveguide within which light waves in the proper wavelength range propagate with low loss.

Improved Design of laser Gyroscope SINS Data Acquisition Card

Abstract: For the limitation of the primary data acquisition card of laser gyroscope SINS, based on the further analysis of the features of output signals of laser gyroscope and accelerator, this paper has finished the design of data acquisition card according to FPGA, which is described by VHDL. This design of data acquisition card is faced to PC/104 system. The experiments show that this acquisition card counts numbers real-timely and exactly, and can achieve the counting effect of primary acquisition card completely; taking PC/104 system simplifies the devices at a large extend so that it also improves its simplification for using and flexibility for collocation.

Prototype Design and System Test of Fiber Optic Gyroscope North-Finder

Abstract: A dynamic north-finder scheme based on the fiber optic gyroscope(FOG) is presented to measure the north component of the angular velocity of earth rotation.The sine output signal of the FOG is sampled and processed to calculate the direction of surveyed point on the surface of earth.The principle and the prototype of the fiber optic gyroscope north-finder is described,the deviation influence caused by the basemen tilt on the north angle precision is analyzed particularly,the accelerometer is used to compensate and improve the accuracy of the north-finder.The multi-period and multi-position sampling techniques are adopted to effectively restrain the measurement noise of FOG.The test results show that the true north angle accuracies of 5′ can be obtained within not more than three minutes.

Application of median filter in wavelet domain in the signal processing of the laser gyro

Abstract: The various random noises in laser gyro are the main factor affecting the accuracyIn accordance with the property of its noise,traditional filtering methods have many shortagesIn order to decrease the random error and improve the measuring precision of laser gyro,a median filter method in wavelet domain is presented to denoise a set of zero drift signal of laser gyro,and the method of Allan variance is used to analyze the filtering result quantitativelyThe result shows that the filtering algorithm can produce the better filtering effect than median filter and wavelet soft threshold denoising,decrease the angle random walk,rate random walk,rate ramp,the bias instability and quantization noise,and improve the stability of laser gyro drift output

Influence of nonlinear dispersion of the refraction index on the Sagnac effect in semiconductor ring lasers

Abstract: Mutually contradicting previously reported theoretical results on the effects of a dispersive active medium in a ring laser on its sensitivity to rotation are critically analyzed. A measure of the rotation rate in the active ring resonator is the beating frequency Dn between the counterpropagating waves whose frequencies are shifted in opposite directions due to the Sagnac effect. Dn is shown to be inversely proportional to the group index of the medium filling the cavity. A comparison of the results obtained considering the resting and rotating frames confirms the applicability of Fresnel's original expression for the optical drag effect to the analysis of the Sagnac effect in an active laser gyro. The frequency splitting Dn is sensitive to dispersion via the group refractive index.

A dual-mass MEMS vibratory gyroscope with adaptive control scheme

Abstract: A micromachined vibratory gyroscope with two proof-masses to measure rotation rate is presented. The two proof-masses are driven electrostatically in opposite directions along drive axis to generate differential Coriolis force detection. In order to improve the performance of the MEMS gyroscope, an adaptive control method is developed. This scheme tunes the drive natural frequencies of gyroscope to a given frequency, regulates the amplitudes of the drive axis to a required value, achieves translational acceleration elimination, cancels out quadrature error due to stiffness coupling, and drives the sense axis vibration to zero for dynamic range and precision improvement. Simulation results verify the theoretical analysis.

A New Method for Eliminating the Lock-in Error of Mechanically Dithered Ring Laser Gyro

Abstract: The origin of tock-in error of the mechanically dithered ring laser gyroscopes(MDRLG)is theoretically analyzed.It is obtained that the lock-in error relates to the input angular velocity,the dither frequency and the dither magnitude.According to the limitation of pulse count decoder caused hy the readout circuit,a new method for eliminating the lock-in error of RLG is presented.At first,the phase character at the zero rate of crossing is described by a parabola equation.Secondly,the fractional angular signal that is smaller than a pulse count is compensated.Finally,by utilizing the values of sine,cosine and the second derivate of the phase at the zero rate of crossing,the lock-in error is eliminating.The simulation results show that the maximum output error of RLG is reduced from 6.25% to 0.622%.So this method improves the detection precision of RLG,and the output signal of RLG has preferably stability and repetition.

A bulk micromachined gyroscope with improved quality-factors at atmospheric pressure

Abstract: This paper presents a bulk micromachined gyroscope with fully symmetric and doubly decoupled structure. The fully symmetric structure enables matched resonant frequencies of the drive and sense modes. The doubly decoupled mechanism, which reduces the cross-coupling and the quadrature error, is realized by independent and folded suspensions for restricting the drive and sense moveable fingers' degree of freedom (DOF). Additionally, the gyroscope has large quality factors even operating at atmospheric pressure, which is designed by utilizing slide film damping effects in drive and sense modes. Simulation results show that the resonant frequency for the drive and sense modes are 2776Hz and 2777Hz, respectively, and the cross-coupling is less than 0.2%. The gyroscope chip is fabricated by silicon-glass anodic bonding and deep reactive ion etch (DRIE) technology. The fabricated gyroscope has a structure thickness of 80 μm and a whole chip size of 5.5×5.5 mm 2 . The gyroscope has a static sense capacitance of 3.5 pF with minimum capacitive gaps of 4 μm. The measured resonant frequency with damping is 2581 Hz with the quality factor of 195 at atmospheric pressure.

Detection limit of a Sagnac interferometer

Abstract: In this work an implementation of angular sensor movements is made based on the Sagnac effect, made it in volume optics, using a detection method of the interference lines and its amplified pattern. The new devices of sensing through optical systems, have given a new vision of measurement and instrumentation, guiding to new studies on designs and prototypes of themselves. An example of these developments is the advance in devices of sensing in fiber optic, such is the fiber optic gyroscope (FOG) which is based on the Sagnac effect. This device has a great sensitivity because the area enclosed by the interferometric ring, is through a fiber optic coil, which increases the sensitivity and diminishes the size of the device. It is possible to indicate that in previous years, with the technology then existing, the utility to use the Sagnac effect like a gyroscope was very limited, because it was just employed to measure angular movements of great magnitudes and with very big areas, since there was not the optical detection systems of the great sensitivity that now exist or coherent sources with high power, indispensable elements in the implementation of the system. For that reasons, the application of this effect began to grow with the development of the fiber optic, and was possible diminish the size and increase the area of the device. Thus the Sagnac effect in volume optics was relegated by the fiber optic interferometer. Nevertheless using the new electronic systems of amplification and optoelectronic devices that now exist, we have rescued the Sagnac effect in volume optics to make measurements of angular velocities in an interferometric system of 0.25m2. For this work, was necessary to create a detection system of great quality, this was made using a detection method of the interference lines and amplification of the interferometric pattern.

Rotating sensing based on slow light coupled resonator structure with EIT-like property

Abstract: We discuss the relationship between Sagnac effect and "slow light" phenomenon, and point out that although the medium and waveguide dispersion can in no way affect the magnitude of Sagnac effect, the highly dispersive structure is still beneficial to the enhancement of Sagnac effect and can be utilized to detect absolute rotation for navigation purpose. Based on the EIT-like property of coupled resonator structure, a miniature highly sensitive gyroscope is possible. This EIT-like phenomenon occurs through a classical mean in a coupled resonator structure due to all-optical classical interference, called coupled resonator induced transparency (CRIT). With the analogy between optical and atomic parameters, we treat Sagnac effect as a phase perturbation to resonators' optical parameters, and then analyze Sagnac effect in a CRIT structure with a transfer function approach and derive the explicit expression of relative Sagnac phase shift. We find that Sagnac effect is enhanced as a factor as light slows, and can be tailored by adjusting the optical parameters of structure. Furthermore, as a potential highly sensitive, compact size rotation sensor, some issues for the implementation of CRIT structure based gyroscope are discussed and considered, such as the fabrication possibility, line-width, shot noise limit sensitivity and integration issues. With the improvement of micro-fabrication technique, this gyroscope should have all-solid configuration, compact size and also be expected to achieve comparable sensitivity to common optic-fiber gyroscope. It would be easily integrated to all-optical application and construct a high performance rotation sensor.

Method for determining angular speed of laser gyroscope and systems based thereon

Abstract: FIELD: engineering of laser gyroscopes ^ SUBSTANCE: laser gyroscope includes circular laser, electronic block and swaying system on immobile base, possible use for measuring its angular speed Method includes measuring increments of turning angle theta during query time l/fd and determining speed of rotation of gyroscope and systems based on it in accordance to following formula: where thetai - increment of rotation angle, i - number of measurement thetai, N - number of measurements thetai, fd - number of measurements per second ^ EFFECT: substantially reduced error caused by mechanical oscillations of gyroscope relatively to immoveable base, and reduced discontinuousness of angular speed measurement without usage of additional optical elements in its structure ^ 2 dwg