Showing papers on "Ring laser gyroscope published in 1989"

Optical fibre Brillouin ring laser gyroscope

Abstract: An active all-fibre ring resonator gyroscope based on stimulated Brillouin scattering is demonstrated. The occurrence of guided acoustic modes in certain optical fibres is found to increase the lock-in range, and a novel method to reduce lock-in for this type of gyroscope is investigated.

Ring laser gyroscope dither drive system and method

Abstract: A dither drive system for a ring laser gyroscope includes a computer, a digital to analog converter, a filter, and a power amplifier The system senses the dither frequency of the gyro frame and produces a digital signal that corresponds to a specified dither drive signal and toggles the dither drive signal to drive the flexure at its resonant frequency The dither drive system generates digital waveforms that approximate the sine function and digital waveforms that approximate the cosine function and applies the digital waveforms in quadrature to the flexure

Analysis and observation of coupling ratio dependence of Rayleigh backscattering noise in a fiber optic gyroscope

Abstract: Noise due to Rayleigh backscattering in a fiber-optic gyroscope is observed in quadrature with the Sagnac signal. This noise can be nulled by adjustment of the coupling ratio of the loop coupler and the state of polarization in the gyro loop. A rigorous analysis of the phases of, and the modulations applied to, the primary and scattered beams shows that no coherent Rayleigh backscatter noise should be detected on the Sagnac signal even with relatively coherent semiconductor laser sources. >

Resonant interferometer fiber optic gyroscope

Abstract: A passive resonator gyroscope in which a laser beam is split into two equal intensity beams in a waveguide, each of the beams being coupled to counterpropagate around a fiber optic ring. The beams, after splitting, are frequency modulated with a voltage having a serrodyne waveform, the polarity of the voltage applied to the modulator for the one beam being opposite to the polarity of the modulating voltage applied to the modulator for other beam. The laser frequency is locked to the optical cavity half wave resonant frequency and when the laser is so locked, the modulating voltage is applied for a first period with one polarity and then for a second period of the same duration with the opposite polarity. The output beams from the optical fiber ring are combined in the waveguide and a portion of the combined optical beam is provided to a photodetector. A circuit connected to the photodetector determines the difference between the light impinging upon the photodetector during the first period and during the second period, this difference providing a measure of the Sagnac shift produced by the rotation of the fiber optic ring.

Housing and support assembly for ring laser gyroscope

Abstract: Disclosed is a housing and support plate assembly for use with a dithered ring laser gyroscope which attenuates thermal and structural changes due to a varying environment. A dither mechanism is structurally supported between a housing and a support plate in a manner which serves to attenuate cross-axis movement and input axis tilting of the gyro assembly, and torsional stress.

Optically-locked fiber-optic resonant gyro

Abstract: A fiber optic resonance gyroscope which has a laser diode as the coherent light source and employs direct optical feedback to that laser diode from light propagating in one direction around a fiber optic resonance ring operating in the peak resonance mode, to maintain the laser output locked to the resonance frequency of the ring. Light propagated around the fiber optical ring in the opposite direction is phase and frequency modulated before being coupled to the ring and a portion of that light exiting the ring is photodetected, the resultant electrical signal being demodulated and used as an error control signal to maintain the modulation frequency at a specific value related to the resonance frequency of the ring for light transmitted in that direction. This error control signal is taken as the gyroscope output of the system.

Partially transparent mirror for a ring laser

Abstract: Provided herein is a ring laser gyro system having a special and improved partially transparent output mirror which provides relatively undistorted circularly polarized coherent light beams to the photo detector and amplifier of the system from the laser cavity thereof. This improved mirror achieves its results by sandwiching a non-quarterwave stack between two quarterwave stacks of multi layer, all of which are coated on a Zerodur substate mirror. The improved mirror achieves nearly Zero phase retardation and a Tp/Ts ratio equal to one.

Faraday rotator assembly.

Abstract: Disclosed herein is a side mounted aperture and a Faraday rotator assembly useful in conjunction with an out-of-plane multi-oscillator ring laser gyroscope. The aperture and Faraday rotator assemblies contain components which are optically contacted to one another as well as the ring laser gyroscope frame. The assemblies disclosed herein provide a simplified construction designed to fixture the Faraday rotator element in order to minimize handling and facilitate alignment to the ring laser gyroscope cavity, free from contamination and in proper alignment for optimum use of the Faraday rotator component and aperture needed for proper operation of an out-of-plane multi-oscillator ring laser gyroscope.

Cost‐Effective, High‐Accuracy Inertial Navigation

Abstract: In spite of the trend towards Global Positioning System (GPS)/ Inertial Navigation System Hybrids, certain applications demand a pure inertial solution to give high-accuracy navigation performance. Modern day Inertial Navigation Systems are dominated by the Ring Laser Gyro technology; however, these systems lie normally in the 1 nautical mile per hour class. To obtain a factor of improvement demands either: • Development of higher accuracy (and hence more expensive) inertial sensors; both gyro and accelerometer • Alternative mechanization of existing inertial sensors. An alternative mechanization which is ideally suited for today's ring laser gyros is one that can be borrowed from the past. This technique is the rate bias technique which solves many of the problems associated with dithered gyros, and in addition attenuates the effects of many of the inertial sensors (both gyro and accelerometer) errors. This paper discusses the design rationale and system design, which together with flight test results demonstrate that a rate bias ring laser gyro Inertial Navigation System provides a cost effective solution to the pure high-accuracy Inertial Navigation System requirement.

Triaxial ring laser gyroscope with independent cavity length control

Abstract: A monolithic triaxial ring laser gyroscope includes three orthogonal ring cavities, the optical path length of each of which is independently controllable. Three planar ring cavities are formed within a frame that is shaped into the form of a rhombic dodecahedron. A mirror is fixed to each of the twelve faces of the frame for directing the counter propagating light beams within the three orthogonal cavities. Anodes which communicate with the cavities through bore holes are fixed to predetermined surfaces of the frame while three cathodes are positioned at flattened portions of preselected vertices of the dodecahedron and located in such a way as to eliminate undesired bias resulting from Fresnel-Frizeau effects.

Piezoelectric transducers for a ring laser gyroscope dither motor

Abstract: The present invention is to provide an arrangement of piezoelectric transducers attached to a dither spring spoke which allows for both flexing a dither spring spoke and sensing the flexure of the same dither spring spoke.

Method and apparatus for planar alignment of a ring laser gyroscope forminimum magnetic bias sensitivity

Abstract: A method and apparatus for aligning the light path of a square ring laser gyroscope wherein the alignment method includes directing two input beams of light into the cavity of the gyroscope. Next, the input beams are intercepted prior to their incidence upon the input mirror with a pair of polarizers. Subsequently, the extinction ratios of the first and second output beams of light are measured at the exit mirror. The curved mirrors of the gyroscope are then translated in opposite directions and equal amplitude so as to change the extinction ratios of the output beams. Such translations are repeated until the measured extinction ratios are substantially equal.

Process and device for demodulating the turning rate signal of a fibre-optical gyroscope

Abstract: of EP0400197The method and the device for reading out a fibre-optical gyroscope is based on the concept of determining in each case only one particular phase interval of the read-out signal of the photodetector (7) of the fibre-optical gyroscope modulated with a periodic function by keying the light signal for particular time intervals, and thereafter and cyclically further phase intervals in the same manner, so that the entire photodetector signal is detected after one full cycle. The signals allocated to individual phase intervals are in each case averaged by themselves and processed further to obtain a proportional signal proportional to the rate of rotation. The readout signals can also be processed in such a manner that a control signal is obtained for the deviation of the phase modulator (6) and/or the gyroscope scale factor is stabilised. The essential advantage of the invention lies in the fact that the signal processing frequency of the gyroscope electronics is no longer tied to the frequency of modulation of the fibre-optical gyroscope but can be much lower (for example lower by a factor of 1000), which considerably increases the accuracy of the electronic evaluation. The invention can be applied to interferometer and resonator gyroscopes.

Piezoelectric mirror for a laser gyroscope

Abstract: The mirror is used in a laser gyroscope of the type comprising an otical unit (1) containing an optical cavity, inside which laser waves are generated, at least one movable mirror (19) with piezoelectric motor and means for servocontrol of the cavity length. It comprises a motor composed of at least two piezoelectric elements (25, 26) fixed on either side of a part (27) having the shape of a thin disc, made of the same material as the other parts of the mirror. One of the two diametres of one of the piezoelectric elements (25, 26) differs from the corresponding diameter of the other piezoelectric element. The invention provides a solution making it possible to ensure the required dynamic range without any risk of creep in the parts or in the bonding areas whilst being insensitive to the environmental conditions.

Ring laser gyroscope with a tube assembly

Abstract: A ring laser gyroscope, which has a triangular quartz block with a triangular quartz tube assembly forming an outer cavity for one rotating beam and an inner cavity for an oppositely rotating beam, is provided. The problem of lock-in of the beams is avoided. A pair of anodes and cathode means are provided for energizing the beams. A mirror is mounted at each corner of the block for reflecting the beams with one mirror being a partly reflective mirror for passing through portions of the inner beam and the outer beam. Outside the partly reflective mirror are mounted a first mirror for reflecting the inner beam, a second mirror for reflecting the outer beam, and a beam combiner mirror for combining the beams. A frusto-conical mirror receives the combined beams and reduces the mean diameter of the outer beam. A fringe detector receives the inner beam and outer beam on an area or point on a face of the fringe detector, which provides a gyroscope output.

Apparatus and method for correcting ring laser gyroscope phase errors at turnaround

Abstract: Digitized heterodyne signals in a ring laser gyroscope are processed to determine the phase and acceleration of heterodyne signals at turnarounds in the angular motion of the frame of the ring laser. A hybrid analog/digital design that incorporates the necessary logic processes the turnaround data to produce a phase correction that can be added to the gyroscope count to correct phase errors that at each turnaround. Separation of high speed data processing from lower rate data simplifies the code and permits evaluation of turnaround correction performance. A fully digital system determines a phase distribution for the detected turnarounds and processes the phase distributions of the heterodyne signals for a multiplicity of turnarounds to determine an angle towards which the phase distributions are skewed and the amount of that skew. A phase correction is then calculated to compensate for turnaround-induced errors in measurements of phase differences between the two beams as a function of the skew angle and the amount of skew of the phase distribution.

Ring laser gyroscope with a non-loss inducing mode suppression mechanism

Abstract: Disclosed herein is an apertureless ring laser gyroscope which achieves higher order transverse mode suppression without the use or need for a restrictive aperture that can be a source of unwanted scatter. Such mode suppression is achieved by operating the ring laser gyroscope in a higher pressure range (from 12 to 18 torr) than the range normally considered for ring laser gyroscope operation. Through the mechanism of pressure broadening and mode competition, the lower order TEM 00 mode remains the only transverse mode present in the optical cavity of the ring laser gyroscope.

Apparatus and method for determining ring laser gyroscope phase at turnaround

Abstract: An apparatus and method of determining gyro het phase and acceleration at turnaround using the digitized heterodyne signals. A digital design that incorporates the necessary logic and is integrated into a gyro unit. An integer algorithm that processes the turnaround data to produce a phase correction that can be added to the gyroscope count. Separation of high speed data processing from lower rate data to simplify the code and permit evaluation of turnaround correction performance.

Combination fringe pattern and power monitoring assembly for a ring laser gyroscope.

Abstract: To detect both the rotation and rotational rate of a ring laser gyroscope and the power level of the laser beams circulating within a cavity of a particular axis in the gyroscope, the present invention uses a multiple segment photodetector, in combination with appropriate circuitry. The fringe pattern information relating to the gyroscope rotation is obtained by combining 90 DEG out of phase currents from adjacent segments and the total power level of the circulating laser beams is obtained by summing algebraically the power from the different segments.

Readout beamsplitting/combining apparatus for ring laser gyro

Abstract: A readout apparatus for both partial beams (101,102) of a ring laser gyro (100) is designed strictly symmetrical so that each partial beam until its detection on a photodetector (114-117) travels the same path length. Both partial beams are differently polarized (105,106), are superimposed (107,108,109) and then again geometrically split-up (110,111) whereby a fixed phase relationship (90°) may be introduced between the split-up partial beams (FIG. 1).

Apparatus reducing thermal sensitivity of multioscillator

Abstract: Disclosed herein is a ring laser gyroscope having a non-reciprocal polarization rotation device such as a Faraday rotator configured to provide, through use of a Faraday magnet, a relatively uniform magnetic field across the profile of the Faraday rotator. By providing a uniform magnetic field across the diameter of the Faraday rotator, the magnetic lensing effects are reduced and the thermal sensitivity of the gyroscope's bias is substantially reduced.

Passive type ring laser gyroscope

Abstract: PURPOSE:To prevent a zero point and a scale factor from fluctuating by a method wherein a passive type ring resonator which projects a parallel beam when the input light is a parallel beam and a drive mechanism which corrects a light emitting element in a plane vertical to an optical axis are provided. CONSTITUTION:A ring resonator 16 is composed of an optical element 16A which consists of a half mirror 161 and a mirror 162 and an optical element 16B which comprises mirrors 163 and 164. A projecting beam from the resonator 16 is made to penetrate half mirrors 18 and 19 and detected by a detector 20 and supplied to a lock-in amplifier 22 through a light detecting circuit 21. A signal of a frequency W from an oscillator 17 is supplied to the amplifier 22 and a detected light signal is synchronously detected, whereby an output can be obtained proportionally to a revolution angular speed. The positional relation of a laser rays source 11 with the half mirror 161 and a mirror group is corrected even if a temperature changes and an oscillation occurs. That is, a positional deviation is detected by a position detecting element 26, and an incident position is controlled and corrected by an X-Y fine movement mechanism 28.

Ring laser gyroscope

Abstract: A radio frequency excited ring laser gyroscope 50 comprises a closed resonant cavity 75 which surrounds a helical coil 72 driven at a high radio frequency (eg 5 to 550 megahertz). The coil surrounds one leg of the gyroscope which is carved out and surrounded by the resonant cavity 75. Such a radio frequency excitation system eliminates the need for high power DC discharge components such as cathodes and anodes, and, for example, problems inherent with properly sealing the cathodes anodes to the monolithic frame of the ring laser gyroscope. The resonator shield prevents r.f. interference. Also detailed is a multioscillator ring laser gyroscope (Fig. 5): a split gain multioscillator ring laser gyroscope (Fig. 6) (a low D.C. signal applied to r.f. coil 112 fine tunes the field from permanent magnet 116); and control circuitry (Fig. 7).

Fin-stabilized subprojectile

Abstract: There is provided a fin-stabilised subprojectile (10) with a target acquisition device which, by the use of a rigid sensor (14) and a triaxial laser gyroscope (16), is characterised in comparison with known subprojectiles by a high firing stability and reliability, at the same time with a simple construction. … For control in a target area, there are microreaction propulsion units (18) which are arranged in the subprojectile (10) in front of its centre of gravity. … …

Method of making glass-ceramic laser gyroscope frame

Abstract: This invention provides a method for forming ring laser gyroscope frames without extensive machining. Parts of necessary configurations for such frames are so fashioned that they can be sealed together into a unit. Those parts are prepared from very low expansion glass-ceramics of particular compositions and are sealed together with low expansion, thermally devitrifiable sealing glasses, also of particular compositions.

Fixation device for the actuation mechanism of a laser gyroscope.

Abstract: of EP0323359The device is applicable to a laser rate gyro consisting of an optical block (1) mounted so as to oscillate on a support (13) and an elastic system in the form of a wheel comprising an outer ring (9) and a hub connected by thin plates (11) which are excited by piezoelectric ceramics. The optical block (1) is gripped between two gripping rings (15 and 16) attached firmly to the outer ring (9). The optical block (1) is gripped by the said rings (15 and 16) through a material (26) which is more ductile than the material of the said rings. The device is particularly useful for solving problems arising from the deformation of the optical block through stresses caused by temperature variations and from the need to dismantle the device easily.