Abstract: A rotational sensing 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, with the use of a local oscillator. The technique allows for rotational rate and direction detection, as well as cavity length control, with a minimum of cross-talk.
Type:
Grant
Filed:
November 21, 1991
Date of Patent:
February 23, 1993
Assignee:
Litton Systems, Inc.
Inventors:
John G. Mark, Daniel A. Tazartes, Tae W. Hahn
Abstract: Disclosed herein is a Fault-Tolerant Inertial Navigation System comprising, in a preferred embodiment, a Redundant Set of at least two Inertial Navigation Systems, from which one may identify and isolate at least one instrument within an Inertial Navigation Unit which shows substantial performance degradation. The two inertial navigation units are fully capable of performing navigational functions. Each of these inertial navigation units has a plurality of navigational instruments, including at least three linear sensors (such as accelerometers) and three angular change sensors (such as gyroscopes or ring laser gyroscopes). No two linear sensors nor any two angular change sensors of either unit are aligned colinearly. Each of the inertial navigation units produces a set of independent navigational solutions at each of their respective outputs.
Abstract: A triaxial Sagnac interferometer employs a single source of optical energy and a single photodetector. An optical fiber network interconnects the source and the photodetector with three fiber optic gyroscopes. A phase modulator is associated with each of the gyroscopes for applying a phase difference bias. The modulators are controlled by a common control circuit. The outputs of the modulators are divided into three distinct modes. During any one mode, two of the three gyroscopes are blanked so that the composite output comprises a readily interpreted serial presentation of individual gyroscope data.
Abstract: Apparatus and methods for reducing and preventing polarization fading in unbalanced measuring interferometers. An extended interferometer having a plurality of sensors and a compensating interferometer are used. They are driven from a pulsed optical signal source wherein the optical signal comprises sequences of two pulses each. To prevent polarization fading the polarization of a predetermined one of each two-pulse sequence is switched, preferably orthogonally, from sequence to sequence. Interference pulse output groups are produced for each two-pulse driving sequence. Each output group has the same number of usable pulses as the number of sensors in the interferometer.
Abstract: A high altitude G-valve produces a pressure signal in response to altitude and G-load without a connection to an external altitude sensing device. Bleed path pressure regulation by an aneroid valve and a G-sensing valve control a pilot valve which in turn controls a main valve. The main valve provides regulated air to the G-valve outlet in response to the pilot valve. A manually actuated button simulates a high-G load on the G-sensing valve to test the operation of the device.
Abstract: The frequency of an optical signal output from an optical source is controlled by adjusting the frequency of the optical signal output from the signal source to maintain a selected optical transmission through a Fabry-Perot cavity.
Abstract: A GaAs/AlGaAs heterojunction IMPATT diode is described. The AlGaAs n-type avalanche layer is graded so that a 0.30 eV bandgap discontinuity of the pn heterojunction is provided without any bandgap discontinuity at the avalanche/drift layer interface. Minority carriers in the p-type GaAs layer are concentrated at the junction due to the discontinuity which occurs primarily in the conduction band thereby concentrating the zero bias electric field and thus minimizing the voltage drop across the avalanche layer. Furthermore, the zero bias depletion width is increased due to the increased field, which lowers the device capacitance.
Abstract: A protected fiber optical splice and a method for making the protected splice. The protective structure encapsulates first and second spliced optical fibers. The fibers are preferably fusion spliced. The protective structure includes a rigid tube surrounding the splice and its adjacent regions of the spliced fibers. A plastic such as an epoxy or moldable plastic is injected into the tube between the substantially axially centered fibers and splice, and the interior wall of the tube. Two molding fixtures are preferably surrounding the two ends of the tube, for injecting the moldable plastic into the tube and for shaping the portions of the structure external to the the tube ends.
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.degree. or .pi. radians phase shift to one of a set of heterodyned signals, A.sub.in, and B.sub.in, with respect to a second set of Split Gain frequency signals, A.sub.out and B.sub.out, in order to extract these Split Gain frequency signals.
Abstract: A single frequency solid state laser has been designed for generation of a high power Q-switch pulse followed by a quasi-CW low power tail by properly controlling the laser resonator transmission via an intracavity Q-switch. The generation of a stable single frequency pulse is accomplished by a primary feedback control system containing a central timing and prelase control unit. Generation and smoothing control of a quasi-CW pulse tail is accomplished through a secondary feedback control system.
Abstract: A mismatched path length fiber optic interferometer is optically coupled to an optical fiber and configured to form an omnidirectional acoustic sensor. A second mismatched path length fiber optic interferometer is optically coupled to the optical fiber and configured as a first gradient sensor. A second fiber optic gradient sensor is also optically coupled to the optical fiber. A detector optically coupled to the omnidirectional acoustic sensor and to the gradient sensors converts optical signals output therefrom to electrical signals indicative of the magnitude and direction of changes in an acoustic field. The omnidirectional acoustic sensor may include a length of optical fiber wrapped around the housing while the gradient sensors are mounted inside the housing. The housing perferably has a volume that is adjustable for controlling the buoyancy thereof. Each gradient sensor preferably comprises a pair of mandrels formed to enclose chambers. Optical fiber coils are formed on the mandrels.
Type:
Grant
Filed:
May 22, 1990
Date of Patent:
October 13, 1992
Assignee:
Litton Systems, Inc.
Inventors:
Bruce A. Danver, Jeffrey D. Lastofka, Michael R. Layton
Abstract: A flux monitor high light intensity cut-off circuit for a night vision device which includes a photo detector and an integrator. Incident light striking the photo detector causes its resistance to change, resulting in a voltage change at the photo detector. As long as the photo detector voltage is below a first threshold voltage level, the integrator is inoperative. When the voltage at the photo detector exceeds the first threshold voltage level, this voltage is then applied to the input of the integrator. The integrator then produces an output voltage proportional to the integral of the input current. Once the output voltage of the integrator reaches a second threshold voltage, power to an image intensifier assembly within the night vision device is interrupted.
Abstract: A printed circuit board connector includes a daughterboard connector and a pin header. The daughterboard and pin header contacts are secured in their respective housings by interference nibs which are mounted on resilient portions of the contacts. Various constructions are disclosed for separating contact from a carry strip by means of a weakened break-line which will secure the contact to the carry strip during post-manufacturing operations and will form a sharp V-shaped tip when the contact is intentionally removed from the carry strip.
Type:
Grant
Filed:
June 17, 1991
Date of Patent:
October 6, 1992
Assignee:
Litton Systems, Inc.
Inventors:
Robert M. Bogursky, Robert M. Bradley, John E. Jones, Carmine Gugliotti
Abstract: A discoid optical correlator system having a plurality of reflective optical components, a source of electromagnetic radiation, such as visible light, and an output detector which are positioned around the rim region of a solid disk body to develop a symmetrically folded optical axis traversed by a beam of electromagnetic radiation so that an unknown object is optically detected and identified.
Abstract: Methods are disclosed for providing a rugged attachment of an optical fiber to an integrated optics chip. A first plate is attached to a first surface of the chip, the thickness of the chip is reduced to a value less than the diameter of the fiber but of sufficient optical thickness so that the evanescent field of a guided mode is negligible outside the chip, a second plate is attached to a second major surface of the reduced-thickness chip, the fiber is coaxially jacketed with a material suitable for attachment to the first and second plates, the fiber is positioned with respect to a waveguide on the chip, and the jacket of the fiber at its end face is symmetrically attached to both the first and second plates at a plurality of locations. Alternatively, a single plate can be attached to the first surface of the chip without reducing the thickness of the chip and either a jacket on the fiber or the curved periphery of the fiber itself can be attached symmetrically to both the plate and the substrate.
Abstract: A force balanced instrument, such as an accelerometer, employs a pendulous mass having combined electrostatic pickoff and forcing plates on opposite sides thereof. The plates provide a constant attractive force in successive periods acting alternatively on opposing sides of the sensitive element. Force balance is achieved by controlling the duty cycle so that the difference in duration between each of the parts of a full cycle is a linear measure of acceleration. Voltage on each of the forcing plates is sensed independently immediately after each is charged with a fixed charging pulse which provides a fixed force level over the duration of the part cycle. The two successive voltage samples are stored, and the difference between them integrated to control the duty cycle of a pulse width modulator, which itself controls the duration of application of the alternately directed forces applied by the respective plates to the pendulous mass.
Abstract: A rare-earth doped glass waveguide is optically pumped to produce superfluorescent light. The waveguide is formed in a glass substrate. The pump light is input to a first end of the optical waveguide, and the output is emitted from the other end. A grating formed on the waveguide near the output end reflects the pump light to separate the pump light from the output light.
Abstract: A correction to the output angle of the ring laser gyroscope is calculated as a function of the phase difference and the magnitude of coupling between the two counterpropagating beams when the dither oscillations change direction. A pair of heterodyne detectors produce heterodyne signals indicative of the interference pattern between the counterpropagating beams. A signal indicative of the sum of the separate beam intensities is demodulated with the heterodyne signals to determine the magnitude of coupling between the beams in the ring laser gyroscope.