Showing papers on "Ring laser gyroscope published in 1982"

All-fiber gyroscope with inertial-navigation short-term sensitivity.

Abstract: We report new experimental data for an all-fiber gyroscope with a noise density of 0.004(deg/h)2/Hz. This is compatible with the requirements for inertial navigation. Noise contributions from the coherent Rayleigh backscatter when a phase-modulation bias scheme is used and also from acoustic vibrations are discussed.

Observation of intensity-induced nonreciprocity in a fiber-optic gyroscope.

Abstract: Nonreciprocal phase shift has been predicted and observed in a fiber-optic gyroscope based on a Sagnac interferometer when the intensities of the counterpropagating beams are unequal. The magnitude of this intensity-induced phase shift is 1.4 rad/W power difference. At 1-μW power difference, this is equivalent to a rotation rate of 0.2°/h in our 200-m-long fiber with a core radius of 2.25 μm that is wound around a spool of 19-cm diameter. The data are consistent with theoretical predictions based on four-wave mixing in the quartz fiber.

Monolithic three axis ring laser gyroscope

Abstract: A monolithic ring laser gyroscope is formed by six mirrors mounted to the respective center of each face in a cube. Bores in the cube interconnect each of the mirrors. Three orthogonal planes are defined within the cube, each of which contains a laser cavity. Accordingly, three orthogonal beam paths exist, each responsive to rotational inputs about three orthogonal axes.

Dual cavity laser gyro

Abstract: A laser gyro having two cavities which are physically separated so that neither mode volumes have any common parts. Each cavity supports a wave traveling in only one direction either clockwise or counter-clockwise. Other waves, which are normally set up in a ring laser gyro, are prevented by a reversed feedback mirror. The gyro produces two waves whose frequencies are shifted in opposite directions by rotation. Lock-in is not possible. The two frequencies are mixed and the beat frequency is detected by optical heterodyne techniques. The response of this rotation sensor is linear down to zero rotation rate and its accuracy is limited by quantum effects.

Fiber optic rotation-sensing gyroscope with (3×2) coupler

Abstract: A Sagnac gyroscope, for measuring rotation rates, having an optical coupler, adapted for fabrication by integrated optical techniques, which is compact and provides for operation of the gyroscope at quadrature for small rotation rates. The optical coupler is a symmetrical, channel waveguide structure comprising a two-mode central waveguide branching into three one-mode input waveguides at one end and into two one-mode output waveguides at the other end. The output waveguides are optically coupled to the ends of a fiber-optic loop which provides a closed optical path in which the Sagnac phase shift is produced. The middle input waveguide is adapted to transmit an incident beam into the optical coupler while the outer input waveguides are adapted to transmit the output beams of the Sagnac gyroscope to a circuit for measuring and comparing the intensities of the beams in the outer waveguides so that the rotation rate may be determined.

Borehole surveying employing ring laser gyroscope

Abstract: A borehole mapping apparatus which employs a ring laser gyroscope. The path of the laser is defined by looping paths of laser beam travel having long and short stretches of travel. The ratio of the stretches being substantially greater than two.

Ring laser with wavefront conjugating beams

Abstract: An improvement for a ring laser gyro employs insertion of a wavefront conjugating coupling element inside a laser cavity to reduce the lock-in threshold and to reduce the imbalance between the amplitudes of the opposite direction traveling waves (ODTW) in homogeneously broadened rotating ring lasers.

Ring laser gyroscope with doppler mirrors

Abstract: of the Disclosure A ring laser gyroscope has at least two of its mirrors vibrated perpendicular to their reflective surfaces by equal and opposite amounts to maintain the total beam path length constant. The amplitude of vibration causes the beams to be shifted across surfaces of all of the mirrors by a distance that is at least close to a Bessel zero distance so as to reduce the intensity of back scattered radiation at the main wavelength to a value close to zero. For an equilateral triangular ring laser gyroscope, two of the mirrors are vibrated between about 0.66.lambda. and 0.74.lambda. , optimally about 0.71.lambda. . for an isosceles tri-angle having vibrating mirrors at two vertexes having angles of about 51.65°, the magnitude of vibration should be about 0.91.lambda..

Observation of low noise in a passive fiber gyroscope

Abstract: The concept of a fiber optic gyroscope without active control of noise sources or sensitivity has appeal for applications due to the resulting component simplicity and snail volume requirements. Many applications for such a device require only moderate rotation rate capabilities (1-10 deg/hr). The passive gyroscope with a 3×3 fiber coupler demonstrated by Sheem1 exhibited noise levels in the few deg/sec range. We report improvements to this device which resulted in noise levels of ~ 5 deg/hr and a 10 minute drift of ~ 10 deg/hr.

Zeeman multioscillator ring laser gyro insensitive to magnetic fields and detuning frequencies

Abstract: A Zeeman ring laser gyro is described which includes a laser medium of helium-neon consisting of dual isotopes of Ne 20 and Ne 22 in which 53.5% is Ne 20 and 46.5% is Ne 22 by volume. The laser also includes a reciprocal anisotropic dispersion element of quartz which optically splits right and left circularly polarized laser waves by 250 MHz. The portion of the laser cavity in which laser emission is stimulated is exposed to a colinear magnetic field of 30 -20 +10 gauss. The combined optimum parameters produce a laser gyro insensitive to changes in detuning frequencies and magnetic fields.

Ring laser gyroscope

Abstract: A resiliently mounted ring laser gyro is dithered below its resonant frequency with a waveform differing from the sine waveform. This is achieved by a piezoelectric motor formed by several piezoelectric elements in a pile. The motor is acting tangentially on a support for the laser and the support takes the form of a strong biased torsion spring.

Single mirror ring laser gyro readout without combining optics

Abstract: A detector structure for use in a ring laser gyroscope includes a partially reflective surface on an inside face of a carrying substrate for passing a portion of each of the counter rotating gyroscope beams for detection and for reflecting a portion of each of the beams into a light path of the laser gyroscope without passing any optical elements of the detector structure. A detector substrate is spaced with respect to said partially reflective surface to receive the portions of the beams passing the partially reflective surface with patterns formed by the respective beams only partially overlapping. A pair of detectors are provided on the detector substrate, located to receive at least a nonoverlapping portion of each of the beam patterns to provide an intensity indication of the respective beams, and another detector is also located on the substrate, located to receive an overlapping portion of the beams for detecting the rate and sense of motion of interference fringes produced by the respective beams to provide an indication of the frequency difference between said beams. The detector structure also includes yet another detector on the substrate, located to receive an overlapping portion of the beams to provide an indication of the sum of the intensities of the respective beams.

Ring laser gyroscope getter-holder

Abstract: A resilient serpentine shaped tungsten wire is formed to match a short wire section to hold a ring laser gyroscope getter. The getter-holder assembly is positioned within a stepped oblong bore so that the getter is in firm contact with the bore surface at two points. This prevents resonances of the getter or holder that might otherwise destroy the getter while subjected to vibrations.

Fiber optic gyroscope with alternating output signal

Abstract: A Sagnac rotation sensing interferometer that uses a Mach-Zehnder interferometer to provide incident light beams that counter-propagate through an optical-fiber loop. The Sagnac interferometer operates at maximum sensitivity for zero rotation rates when the Mach-Zehnder is adjusted so that the intensities of the incident light beams are equal. By peiodically varying the position of a mirror in the Mach-Zehnder the interferometer is switched into and out of quadrature so that the amplitude of the interferometer output signal is modulated at frequency f o . Phase sensitive detection at 2f o or multiples thereof reduces the background noise level several orders of magnitude below the level for dc operation.

Ring laser gyroscope readout for partially overlapping beams

Abstract: A ring laser gyroscope includes a laser ring having at least three reflective surfaces. At least one of the reflective surfaces is partially reflecting and partially transmissive for removing a portion of the laser light within the ring, and for directing the removed light onto an output detector. Optical elements are provided for displacing the light directed on the output detector in a fashion by which a portion of the light from one of the counter rotating beams only partially overlaps the light from the other beam. A detector is provided for detecting the intensity of each of the counter rotating beams from the nonoverlapping beam portions on the detector and for detecting the fringe motion of the interfacing beams produced by the overlapping portions of the beams on the detector. In another aspect, a detector is provided for detecting the intensity and frequency differences of the counter rotating beams in which two intensity producing detectors are provided spaced apart by a distance corresponding approximately to the overlapping portions of the counter rotating light beams upon the detector, whereby the overlapping portions of the beams fall generally between the two detectors. A plurality of detector stripes are provided between the two intensity detectors, whereby stripes of the interference patterns move across the detector stripes to provide an indication of the frequency difference between the counter rotating beams and sense of rotational input.

Laser gyro using ring laser

Abstract: PURPOSE:To eliminate the dead region around the angular velocity of a laser gyro omega=0 by detecting a one-way traveling wave ring laser rotating with an input axis which is a detected substance and the output beat frequency of a reference linear laser. CONSTITUTION:The frequency of laser light L2 takes a constant value depending on closed optical path length if a normal passing the center of the closed optical path surface of a one-way traveling wave ring laser URL is regarded as a sensitivity axis. In the angular velocity omega of the sensitivity axis, the frequency varies in directly proportional to omega by Doppler effect. When the modulated light L2 and laser light L3 from a reference linear laser RLL not sensing omega are interfered by combining them as the same directional traveling wave through an output read device ROD, interference fringe is generated by heterodyne effect and the fringe moves by a difference between the frequencies of L2 and L3, namely, by the velosity which is proportional to those beat frequencies. Therefore, the laser gyro recognizes omega by measuring its beat frequency.

Ring laser gyroscope with hollow cathode having frusto-ellipsoidal surface

Abstract: A cathode (12) for a glow discharge device and comprising a hollow body provided with an opening and having an internal working surface (18) which is substantially frusto-ellipsoidal. The cathode has particular application to a laser gyroscope.

Non-pendulous counter-balanced dither mechanism for laser gyro

Abstract: An improved laser gyro dither mechanism utilizing a three-spring suspension system which not only isolates dither vibrational energy generated within the gyro and prevents that energy from passing to the mounting case of the laser, but which, additionally, eliminates possible pendulous action by the suspended gyro mechanism. The gyro's ring laser is mounted about a center post in its case. A first spring member is connected between the ring laser an the center post at the top of the post. A second spring member is connected between a counterweight and the centerpost on the bottom of the post. A third spring member is connected between the ring laser and the counterweight on the bottom of the post to complete the suspension system.

Ring laser gyro

Abstract: A ring laser gyro uses means for shaping the gas flow, which inevitably develops as a result of a DC discharge, to optimize the effect of the Fresnel-Fizeau drag on the output signal of the gyro. In one embodiment, a sufficient component of the gain medium flow is provided to produce a substantially constant Fresnel-Fizeau component of the output signal even in the presence of variations of the discharge current. In another embodiment, a sufficient component of gain medium flow is provided to substantially eliminate the Fresnel-Fizeau component of the output signal at a predetermined level of discharge current.

Laser gyro system

Abstract: Disclosed is an improved method and apparatus for providing lock-in error reduction in ring laser angular rate sensors Two independent feed back control systems are employed to independently alter the laser path of a ring laser angular rate sensor so as to obtain a minimum lock-in rate

Polarization Control for an Optical Fiber Gyroscope

Abstract: It is well known that if birefringent fibers are used in the sensing loop of a fiber gyro, a kind of nonreciprocity arises. To overcome this, the insertion of polarizers in the loop has been proposed (Fig.1) [1] and has become common practice [2] . However, this solution of the problem causes further difficulties: time-varying birefringence of the fiber modulates the transmitt-ance of the sensor-loop. To give an example, assuming a fiber length L = 1000 m, a beat length of the orthogonally polarized modes A = 10 m and a temperature coefficient of ∂∧ /∂ϑ = 2 • 10–3/K (data which are common for standard fibers with intrinsic birefringence) one can calculate a temperature change of 10 K to be sufficient to completely block the transmittance. This might be a worst-case example but it illustrates the situation.

Design, Construction, and Analysis of an Ultra-Low Expansion Quartz Resonant Cavity Passive Ring Resonator Laser Gyroscope.

Abstract: : The purpose of this research is to design and build a Passive Ring Resonator Laser Gyroscope (PRLG) that is small in size, constructed from a thermally stable material, and utilizes a laser cavity--resonant cavity mode match design. The small size design is dominated by the physical size of the available components; consequently, the small design is as small as physically possible with these components. The dimensions of the PRLG are as follows: (1) the perimeter of the reson ant cavity is 45.2 cm., (2) the laser cavity is 22 cm. long, and (3) the distance from the center of the laser cavity to the input mirror of the resonant cavity is 49.664 cm. The thermally stable material obtained for the PRLG is a block of Ultra-Low Expansion Quartz (ULE Quartz). The coefficient of thermal expansion for ULE Quartz is 0.55 x 10 to the minus 6th power cm./cm./C, thus making this material a very thermally stable material. Due to the configuration and size of this ULE Quartz block, only the resonant cavity portion of the PRLG is formed using the ULE Quartz block. The laser cavity--resonant cavity mode matching design is accomplished in three steps. First, the spot size of the resonant cavity beam is determined at some point outside the resonant cavity. Second, the laser is designed such that its spot size is identical to the spot size of the resonant cavity beam at that same point. Third, the radius of curvature of the external corner mirror required to change the radius of curvature of the laser cavity beam into the radius of curvature of the resonant cavity beam is determined.

Magneto-optic fiber sagnac interferometer gyro

Abstract: An interferometer gyroscope includes a multitum optical fiber together with apparatus for producing therefrom a light beam containing a sagnac phase shift relatable to the rate of rotation of the coil about an axis of rotational sensitivity. An electrical coil is provided adjacent the optical fiber to generate a magnetic field parallel to the optical fiber to induce a Faraday effect into the optical fiber. A servo apparatus responsive to the sagnac phase shift is provided to adjust the current in the electrical coil. The servo is operative to null the sagnac phase shift in the optical fiber by balancing the Faraday effect and the sagnac effect in the optical fiber, whereby the current in the coil is proportional to the rate of rotation"of the waveguide when the sagnac phase shift is nulled.

Optical Fiber Laser Gyro: Homodyne and Heterodyne Detections

Abstract: The ring interferometer with a multiturn single-mode optical fiber loop has been investigated for use as a rotation rate sensor utilizing the Sagnac effect. We have proposed an optical system with homodyne detection, in which the phase-difference bias can easily be introduced, and the rotation detection experiment was performed using the preliminary test setup with a He-Ne laser [1].