Showing papers on "Ring laser gyroscope published in 1990"

Passive fiber optic gyroscope

Abstract: A fiber optic gyroscope different from the standard concept is presented. A fused fiber 3 x 3 directional coupler provides a constant phase shift thus enabling the detection of rotation rate at the quadrature point without phase modulation. Bias errors due to birefringent coupling centers in the fiber coil are avoided by using an unpolarized light source. A contrast insensitive signal recovery scheme eliminates the influence of polarization fluctuations on the scale factor. First measurements with a prototype gyroscope (90 mm in diameter and 23 mm in height) show a bias stability of <4.7 degrees /h and scale factor accuracy of <0.1% in the range of +/-200 degrees /s.

Radio frequency excited ring laser gyroscope

Abstract: A radio frequency excitation system is disclosed for use in conjunction with a ring laser gyroscope. The radio frequency excitation system is comprised of a closed resonant cavity which surrounds a helical coil driven at a high radio frequency at a range of 5 to 550 megahertz. This closed resonant coil surrounds one leg of a ring laser gyroscope which is carved out and exposed so that it may be surrounded by the resonant cavity. Using such a radio frequency excitation system eliminates the need for high power DC discharge components such as cathodes and anodes, as well as problems inherent with properly sealing the cathodes and anodes to the monolithic frame of the ring laser gyroscope.

Open loop fibre optic gyroscope with phase shift nulling signal processing

Abstract: A simple analogue phase tracking circuit for the fibre gyroscope is described. The system provides a linear output from an open loop gyroscope configuration over a range in Sagnac phase shift >±500° Sagnac, with good linearity and relatively low noise and drift. The use of this demodulator in low-cost medium grade fibre gyroscope applications is projected.

Method and apparatus for demodulating the rotation rate signal of a fiber optic gyroscope

Abstract: A method and device for reading out a fiber gyroscope based on the concept of determining, by gating the light signal for particular time intervals, only one particular phase section of the read-out signal of a photodetector of the fiber optic gyroscope modulated with a periodic function. Further phase sections are determined in sequence and cyclically in the same manner so that the entire photodetector signal is detected after one full cycle. Signals associated with individual phase sections are averaged separately and processed to obtain a rotation rate-proportional signal. The read-out signals can also be processed so that a control signal for deviation of the phase modulator is obtained and/or the gyroscope scale factor is stabilized.

GG1308 ring laser gyro inertial measurement systems: Honeywell's low-cost solution for tactical applications

Abstract: The GG1308 ring laser gyro (RLG) inertial measurement systems represent the smallest-volume, lightest-weight, and lowest-cost RLG systems. These systems are designed to provide the functions required for inertial guidance, aided or midcourse navigation, and vehicle stabilization and control to a wide variety of tactical missiles, standoff weapons, unmanned aerial vehicles, torpedoes, and manned rotorcraft. GG1308 inertial systems achieve their low cost as a result of several significant development thrusts. Low-cost inertial sensors must be utilized. The GG1308 RLG is a true design-to-cost device with producibility and the cost of parts, materials, assembly labor, and manufacturing automation being the dominant design drivers. Additionally, these GG1308 inertial systems use a commonality design approach. This philosophy has made it possible to develop several generic hardware elements which need only be repackaged to provide an inertial system in the form factor required for specific programs. It also provides the system with an adaptability and intelligence to improve its performance throughout its useful life by making software improvements which do not affect the hardware design or production process. >

Dual-Ramp Closed-Loop Fiber-Optic Gyroscope

Abstract: A practical closed-loop approach to signal processing in the fiber gyroscope is presented. A triangle wave phase modulation is used in which the slope of the increasing and decreasing sections of the modulation are adjusted independently to compensate for the phase difference due to rotation rate. Accordingly, the phase difference due to rotation is determined solely by the difference in the times spent on each of the legs of the triangle wave. By synchronizing these times to a clock signal, the output becomes a digital measure of rotation angle.

Laser beam control for a ring-laser gyro

Abstract: An RLG has a laser beam current control system which controls the current so as to produce a constant beam intensity, allowing the RLG to operate at a current level continuously matched to the operating conditions, thus extending the operating life of the RLG.

Mirror transducer assembly for ring laser gyroscope

Abstract: Disclosed herein is a Pathlength Control Assembly for Ring Laser Gyroscope comprising, in a preferred embodiment, a mirror, coupled to a mirror housing including a mirror post, wherein the mirror is mounted on an axially deflectable membrane of the housing. A pair of piezoelectric transducers are responsive to an electronic input signal and mounted to a backing plate. The transducers are mounted within a driver housing and drive a driver post which is made from a thermally expansive material. As the backing plate is deformed to drive the mirror post to axially deflect the mirror membrane, the central driver post passively expands in response to temperature changes. In this manner, the transducers and thermally expansive mirror post act in conjunction to both actively and passively drive the mirror post over the full dynamic range of multioscillator or other ring laser gyroscope.

Ring laser gyroscope output optics detection system

Abstract: A ring laser gyroscope output optics detection system, including a rotational sensing system and cavity length control system for a multioscillator ring laser gyroscope, is disclosed herein that can operate with a simple upright symmetric optics mechanism, where the required signal separation is performed fully electronically. In a preferred embodiment, signal separation circuitry is provided which performs a 90° or π/2 radians phase shift to one of a set of heterodyned signals in order to extract the sagnac effect modulated Faraday frequency signals W A and W B . In order to deal with the inherent problems of crosstalk present in a Faraday biased system, alternative signal separation schemes suggest the use of a 45° or π/4 radians phase shift, as well as a 60° or π/3 radians phase shift. Complementary cavity length control schemes are presented in both fixed component and digitally controlled formats.

Providing an Inexpensive Gyro for the Navigation Mass Market

Abstract: The Micro-Optic Gyro is an all-solid-state, passive ring resonator, laser gyro. It uses a waveguide resonator fabricated in glass by ion-exchange, a GaAlAs diode laser, and a SAW frequency shifter, arranged to operate with servos to maintain the CW and CCW ring resonances. The frequency difference between the CW and CCW resonances is a measure of the rotation rate. The equation for the gyro resolution is given, and some data are presented on prototype gyro performance. We discuss the differences between the cost and performance of this gyro and the fiber optic gyros.

Method and apparatus for suppressing off-axis modes in laser and ring laser gyroscopes

Abstract: A dielectric interference film having a central region of one thickness and a peripheral region of a different thickness is superimposed on one of the mirrors of a ring laser gyroscope for the purpose of suppressing off-axis resonant modes that are characteristic of a resonant cavity. The central region is designed to intercept a large portion of the fundamental mode power and a lesser portion of the off-axis mode power. The difference in thickness between the central and peripheral regions causes the reflected light from the two regions to differ in phase by approximately one-half wavelength and destructively interfere. As a result of the imbalance of the fundamental and off-axis mode powers incident on the central region, the reflectivity losses of the off-axis modes are more pronounced than those of the fundamental mode with the result that the off-axis modes are completely suppressed.

Behavior Of Broadband Fiber Sources In A Fiber Gyroscope

Abstract: Two fiber laser sources, a resonant fiber laser (RFL) and a superfluorescent fiber laser (SFL), have been given initial tests as gyro sources using a medium quality gyro test bed. The RFL reacted strongly to optical feedback from the gyro circuit resulting in very large unstable errors in the gyro output. These were suppressed substantially by an optical isolator which reduced feedback from the gyro, or by a phase modulator within the laser cavity. The SFL was found to be free of errors of this type when operated at output power levels below a threshold level (about 0.5 mw) for self oscillation due to external optical circuit reflections.

Dither signal remover for a dithered ring laser gyro

Abstract: In a dithered ring laser gyro, a dither reference signal is provided to supply information representative of the dither angle or dither angular rate. This information is processed by a signal processor to generate a correction signal which is the sum of (i) a first function of the dither reference signal indicative of the dither angle multiplied by a first coefficient, and (ii) a second function of the dither reference signal indicative of the dither angular rate multiplied by a second coefficient. The aforementioned coefficient may be either selected or generated based on historical data derived from the dither reference signal and the usual sensor output signal. In turn, the correction signal is subtracted from the usual ring laser gyro output signal to provide a corrected sensor output signal.

Digital path length control for ring laser gyros

Abstract: A digital path length control for ring laser gyros comprises a square wave generator, a dither counter (driven by the generator with a quarter cycle delay, a dither DAC, a control counter, a control DAC, and a PZT driven by the two DACs. The PZT controls the path length of the ring laser gyro, and thus controls the intensity of the light in the gyro. A photodetector samples this light and produces an ac signal, which a voltage comparator compares with ground. The output of the comparator is XORed with the square wave, and the output of the XOR gate drives the control counter, strobed with a frequency at least twice that of the square wave. All signal processing is digital, and analog conversion is made only when interfacing the gyro.

Design And Performance Of A Fiber Optic Gyroscope Using Integrated Optics

Abstract: Navigation grade fiber optic rotation sensors (FORS) are being developed as an alternative to spinning mass gyro's for unmanned planetary exploration spacecraft. FORS is attractive because of its many advantages such as long life, low weight, low power, and low cost as compared to its mechanical counterparts. FORS incorporates an advanced integrated optics circuit. The advanced eight-component integrated optics circuit performs all the key signal processing functions and in addition incorporates a unique optical beat detection circuit thereby providing an output in the form of pulses proportional to incremental angular position similar to a ring laser gyro (RLG) but without the inherent lock-in problem RLG's possess.

Demonstration of a ring laser gyro system for pointing and stabilization applications

Abstract: A system specifically designed to meet the requirements of the pointing and stabilization community is presented. Such applications include synthetic aperture radar (SAR) motion compensation and infrared sensor stabilization. Requirements peculiar to this application are discussed and contrasted with traditional inertial navigation requirements. Pointing and stabilization demand consideration of requirements such as high bandwidth, low noise, minimal data latency, dither effects, reference alignment, minimization of size, near-instantaneous turn-on, and analysis of structural resonances. The GG1320 RLG (ring laser gyro) was chosen for this application since it provided the necessary accuracy and could be contained in a small volume. Test results are presented indicating the performance of the IMU (inertial measurement unit). Testing techniques are also discussed and contrasted with traditional inertial navigation system testing. Results indicate that the GG1320 RLG IAU (inertial attitude unit) is capable of meeting the requirements of the pointing and stabilization community. Current and future development activities are discussed relative to performance enhancement, and further applications and requirements are identified. >

Optical Level Crossings

Abstract: We discuss the behavior of two coupled optical modes, specializing to the case of a clockwise and a counter-clockwise wave in an optical ring with backscattering. Generally the coupling constant is complex-valued; the limiting cases of conservative and dissipative coupling are emphasized. When lifting the polarization degeneracy we deal with four optical modes, coupled by backscattering and birefringence. We also consider an active i.e. oscillating optical ring: this corresponds to adding a nonlinear mode-coupling and leads to a description of frequency-locking in a ring laser gyro. Finally we address the analogy between optical and electronic mode coupling in ring-type and lattice-type configurations (“band structures”). Here we emphasize dynamic effects and discuss the merits and limitations of optical modeling of phenomena such as Bloch oscillations and Zener tunneling.

Ring laser gyro comprising rotary oscillation apparatus

Abstract: In a laser block (10) spokes (26,28,30) and a hub (34) are mechanically worked out resulting in a monolithic integration of a dither device into the laser block.

Ring laser gyroscope

Abstract: PURPOSE: To make it possible to conduct complete alignment by positioning an orifice during assembling of a ring laser gyroscope, and conducting the alignment so as to make it possible to pass one lateral mode through the orifice in the case of using. CONSTITUTION: A triaxial ring laser gyroscope 1 has a gain Bohr module 4 between mirror modules 2 and 3. Mirrors 6 to 8 are mounted on the inner surfaces 5 of the modules 2, 3, and shoulders 9 to 11 are provided at the module 2. Further, cutting region 15, disc 15 and orifice 17 are provided at the shoulders 9 to 11. The regulation is conducted by passing pair of lateral modes selected according to the sizes of the disc 16 and region 15, and passing no residue. When the regulation is once conducted by using a bench optical system developed for the purpose, the disc 16 is permanently set to the suitable position by epoxy resin. An aperture is aligned continued to the alignment of the mirror, fixed and a completely optical alignment can be always performed.

Apparatus for compensating for change in laser gyro dither pickoff scale factor

Abstract: A dithered ring laser gyroscope is mounted upon a support, and a pickoff is positioned between the gyro and the support to produce signals representative of rotation angle between the support and the gyro. A correction means is used to subtract out the effect of the dither from the output signal to the gyro. The correction means includes feedback means in the correction-producing apparatus. That feedback means includes tracking compensation for both gain and phase variation of the pickoff and pickoff electronics. To prevent constant or slowly varying signals from affecting the operation of the apparatus, the invention uses a differentiator or a high pass filter between the compensated output signal and the feedback loops.

New Developments In Fiberoptic Gyroscopes

Abstract: F. Zarinetchi, S.P. Smith, and S. EzekielResearch Laboratory of ElectronicsMassachusetts Institute of TechnologyCambridge, MA 02139Fiberoptic inertial rotation sensors (or gyroscopes) so far are based on the Sagnac effect in eithera multiturn interferometers or a resonator2. Both these approaches constitute the fiberopticimplementation of previously demonstrated Sagnac interferometer3 gyroscopes and resonator4gyroscopes employing bulkoptic components. However, there has not yet been a fiberoptic analog ofthe ring laser gyroscope5'6, which has always been a bulk -optic device. In this paper, we presentpreliminary data on a fiberoptic ring laser gyroscope using stimulated Brillouin7 scattering as the lasergain medium. To our knowledge, this is the first demonstration of a solid state ring laser gyroscope orRLG.Figure 1 shows a simplified diagram of a stimulated Brillouin fiberoptic gyroscope. A singlefrequency laser, He -Ne at 1.15 pm, is coupled into opposite directions of a non -polarization maintainingfiberoptic ring resonator (length 25 m; finesse - 250; coil diameter 7.5 cm) and acts as the pump forthe stimulated Brillouin laser. The frequency of the Brillouin laser$ -11 is downshifted from that of thepump by the acoustic frequency in the fiber which is about 15 GHz at 1.15 pm. The direction of theBrillouin laser is opposite to that of the pump because that is the direction that experiences the highestBrillouin gain. The clockwise pump in the resonator is denoted by P- and the counterclockwise pumpby P. The corresponding stimulated Brillouin lasers that are created by the pumps are denoted by B-

Ring laser gyroscope

Abstract: The gyroscope includes a device for producing two counter-rotating beams of laser radiation around a closed path defined by at least three mirrors. A first one of the mirrors is partially transmissive of the radiation in each beam. A detector is responsive to the laser radiation passing through the first mirror to derive electrical signals dependent upon the rotational forces acting upon the gyroscopes about a predetermined axis. A second one of the mirrors is totally reflecting and is associated with transducer operable to vary continuously the position of the second mirror. A second detector is responsive to laser radiation in each of the beams to derive alternating current signals to control the transducer. A control device is responsive to the direct current component of the output of the second r detector to maintain the intensity of the laser beams at a constant value.

Split-gain multimode ring laser gyroscope output optics detection system

Abstract: A rotational sensing system for a split gain, multi-mode ring laser gyroscope is disclosed herein that can operate with a simple upright symmetric optics mechanism, where the required signal separation is performed fully electronically In a preferred embodiment, signal separation circuitry is provided which performs a 180° or π radians phase shift to one of a set of heterodyned signals, A in , and B in , with respect to a second set of Split Gain frequency signals, A out and B out , in order to extract these Split Gain frequency signals

Trimode reflective plane position regulator and angular velocity sensor

Abstract: PURPOSE: To make the lock-in speed low by adjusting the reflection surface position of a laser angular velocity sensor by using a tri-mode type transducer which is capable of slanting with two degrees of freedom and translation with one degree of freedom. CONSTITUTION: A laser gyro 10 propagates mutually opposite laser lights IQ1 and IW2 in a closed circuit determined by mirrors 11 to 13. Parts IQ1' and IW2' of the laser lights pass through the mirror 12 and are inputted to an intensity detecting device 420 and a discriminating device 440. The device 440 responds to variation in intensity caused by the energy coupling between the two light waves IW1' and IW2' and a signal processor 540 adjusts the angle ϕof the mirror 13 and the angle θ of the mirror 11 according to the output of the device 440 and then adjusts a feather sum and an initial state to obtain a minimum lock-in speed. The device 420 outputs the mean intensity of the light wave IW1' and a signal processor 920 translates the reflecting surface 13 according to the output to perform path length control and further slants the reflecting surface 11 with a degree of freedom different from that of θto array an optical loop in a laser light cavity 900.

External scatter removal system

Abstract: Disclosed herein is an External Scatter Removal System for Ring Laser Gyroscopes (such as a Split Gain Multioscillator) comprising a prism mounted on an optoisolator, wherein light transmitted out at least one of the mirrors of the Gyroscope passes into the prism and detector system, while oppositely directed backscattered light from the prism components is not returned to the gyroscope frame's internal optical path, thereby limiting any appreciable backscatter from interfering with an accurate measurement of the rotation rate of the gyroscope.

Method for eliminating gyroscope errors

Abstract: To eliminate gyroscope errors in electrically stabilised two-axis gyroscopes in which one pick-off (52, 54) and one torque generator (46, 48) are arranged on each input axis (X, Y) and the output from each pick-off (52, 54) arranged on one input axis is applied to the torque generator (48, 46) arranged on the other input axis, a first measurement is taken at a first direction of rotation of the gyroscope rotor (42). During a second measurement, the direction of rotation of the gyroscope rotor (42) is then reversed and, at the same time, the polarity of the signals of the pick-offs (52, 54) is switched over. From the gyroscope signals obtained during the two measurements, a measurement value is formed. … …

Ring laser gyroscope mount

Abstract: Disclosed herein is a Ring Laser Gyroscope Mount comprising a low coefficient of expansion metal Invar sleeve and mount coupler The sleeve may be secured to the gyroscope pedestal by being screwed and affixed to a relatively high coefficient of thermal expansion material pedestal, such as HyMu 80 The sleeve is attached also to the glass frame by cementing it at selected locations within the central mounting aperture of the gyroscope frame This securement procedure makes the assembly stiffer in directions perpendicular to the axis of the coupler At least one concentric groove which surrounds the coupler is machined into at least one side of the frame to reduce stress at gyroscope mirror surfaces during thermal excursions The clearance gap where the cement is placed, the groove depth and shape, and the sleeve and coupler are designed to be stiff but not induce distortion

Sagnac-type fiber-optic gyroscope

Abstract: A Sagnac-type fiber-optic gyroscope having a light source, a fiber coil consisting of an optical fiber, a receiver arrangement which are all connected with gates of a directional coupler, in which the light fed into the fiber coil interferes with the light emerging from the fiber coil in a coupling area and the rate of rotation of the fiber-optic gyroscope is determined from the interference signals. In order to achieve a working point which is situated in or close to the quadrature point, the directional coupler is developed as a 4×4 coupler between the arms of which fixed phase relations are provided in the coupling area.

Position measuring device for the light beams of a laser gyroscope

Abstract: The invention relates to a position measuring device for the light beams within the capillaries which form the resonator of a laser gyroscope. This device, which is placed on the substrate of a mirror of the aforementioned laser gyroscope, uses a mask (21) which is perforated with openings (50) and interlocks with the rear side of the aforementioned substrate. The light energies (41) which pass through each opening (50) are directly dependent on the position of the light beam (16) on the mirror (3) and in the resonator. Measurement of these light energies by a photo-electric cell (22) enables accurate evaluation of the position of the laser beam. The invention is applicable to any laser, and in particular to laser gyroscopes.