Abstract: A system for measuring changes in an environmental parameter, such as velocity or pressure, includes an optical signal source for providing a coherent light signal, and an interferometer having a first and second optical legs of unequal optical path lengths. The signal is split into first and second beams that are respectively directed into the first and second optical legs of the interferometer. A fixed mirror reflects the first beam received at the end of the first optical leg. An optical pick-off includes a movable mirror, positioned to reflect the second beam received from the end of the second optical leg. The movable mirror is movable in response to changes in the-value of the parameter to be measured. An optical coupler combines the first and second beams after they have been reflected back into their respective optical legs, producing an interference signal, which is detected by an optical detector.

Abstract: A projectile guidance system without gyros in which the projectile has an orthogonal body coordinate system. The projectile has a triax of accelerometers providing x, y and z acceleration data measured along the x, y and z axes respectively. A GPS antenna and receiver means provides onboard GPS position and velocity data in earth referenced navigational coordinates. A computer and program means stores and accesses time indexed GPS position and GPS velocity data and transforms x, y and z axis acceleration data from body to navigation coordinates. The program means is responsive to corresponding time indexed acceleration data and to GPS velocity and position data for calculating and outputing an estimated projectile roll, pitch and yaw angle via optimal smoothing techniques with respect to local level for each time index iteration of present position to a flight control system for guiding the projectile to a predetermined location.

Abstract: A fiber optic displacement sensor includes a flexural disk assembly affixed to a mounting post that extends from a support base that is enclosed by a housing. Spiral wound optical fiber coils are mounted on opposite sides of the flexural disk with optical fiber leads extending from both the inner and outer diameters of the optical fiber coils and being optically coupled together to form an interferometer. An inertia ring connected to the periphery of the flexural disk has a plurality of peripheral slots therein for routing the optical fiber leads from the optical fiber coils to other components in the housing. The slots in the inertia ring are arranged to allow differing lengths of fiber to be wound circumferentially in different depth slots to accommodate mismatches in optical fiber lead lengths.

Abstract: A displacement sensor and an acceleration sensor are mounted to a common support member. The displacement sensor comprises a first circular flexural disk having a natural frequency less than the frequency range of the acoustic waves of interest. Spiral-wound optical fiber coils are mounted to opposite sides of the first flexural disk. The acceleration sensor comprises a second flexural disk having a natural frequency greater than the frequency range of the acoustic waves. Spiral-wound optical fiber coils are mounted to opposite sides of the second flexural disk. A fiber optic interferometer provides an output signal that is a combination of signals output from the displacement sensor and the acceleration sensor. The displacement sensor includes an inertia ring mounted to an edge of the first flexural disk to keep it nearly stationary when an acoustic wave in the selected frequency range is incident upon the housing.

Abstract: A system for measuring changes in an environmental parameter, such as velocity or pressure, includes an optical signal source for providing a coherent light signal, and an interferometer having a first and second optical legs of unequal optical path lengths. The signal is split into first and second beams that are respectively directed into the first and second optical legs of the interferometer. A fixed mirror reflects the first beam received at the end of the first optical leg. An optical pick-off includes a movable mirror, positioned to reflect the second beam received from the end of the second optical leg. The movable mirror is movable in response to changes in the value of the parameter to be measured. An optical coupler combines the first and second beams after they have been reflected back into their respective optical legs, producing an interference signal, which is detected by an optical detector.

Abstract: A fiber optic seismic sensor includes a central support assembly formed of a metal such as aluminum. A support plate has an inner portion retained within the central support assembly and an outer portion that extends beyond the central support assembly. A pair of hollow cylindrical substrates are mounted in axial alignment on opposite sides of the outer portion of the support plate with the central support assembly extending through the centers of the substrates. The central support assembly comprises a first central support member having a cavity in one end, and a second central support member having a projection extending therefrom and arranged to be received within the cavity in the first central support member. The support plate includes a passage arranged to receive the projection such that the inner portion of the support plate is retained between the first and second central support members.

Abstract: A fiber optic particle motion accelerometer has a housing with a mid-section mounted therein such that the mid-section flexes in response to acceleration along a sensing axis. A proof mass is mounted to an outer edge of the mid-section. A first spiral-wound optical fiber coil is mounted to a first side of the mid-section and a second spiral-wound optical fiber coil is mounted to a second side of the mid-section. A first hinge is formed in the mid-section adjacent the mounting of the mid-section in the housing, and a second hinge is formed in the mid-section between the proof mass and the first and second fiber optic coils. The optical fiber coils are included in an interferometer such that acceleration along the sensing axis produces a phase difference between optical signals propagating in the optical fiber coils.

Abstract: A fiber optic displacement sensor includes a flexural disk assembly affixed to mounting post that extends from a support base. The flexural disk assembly is mounted in a housing. Spiral wound optical fiber coils are mounted on opposite sides of the flexural disk with optical fiber leads extending from both the inner and outer diameters of the optical fiber coils. Optical signals output from the coils are coupled together to form an interferometer. An inertia ring connected to the periphery of the flexural disk. has a plurality of peripheral slots therein for routing the optical fiber leads from the first and second optical fiber coils to other components in the housing. The inertia ring has curved side edges formed such that the optical fiber leads may be spiral wound thereon between the first and second coils and the peripheral slots to prevent damage to the optical fiber leads from sharp bends.

Abstract: A system for measuring changes in an environmental parameter, such as velocity or pressure, includes an optical signal source for providing a coherent light signal, and an interferometer having a first and second optical legs of unequal optical path lengths. The signal is split into first and second beams that are respectively directed into the first and second optical legs of the interferometer. A fixed mirror reflects the first beam received at the end of the first optical leg. An optical pick-off includes a movable mirror, positioned to reflect the second beam received from the end of the second optical leg. The movable mirror is movable in response to changes in the value of the parameter to be measured. An optical coupler combines the first and second beams after they have been reflected back into their respective optical legs, producing an interference signal, which is detected by an optical detector.

Abstract: To minimize the uncompensated part of the Shupe error, a one or more continuous coils (28, 44, 46) thermally stable material is added to a composite coil assembly (20) to dominate the composite in terms of thermal expansion and elastic modulus. The thermally stable material includes a plurality of continuously coiled fibers (28, 44, 46) selected from a material group which possesses a high modulus and a low coefficient of thermal expansion. The preferred fiber is formed from a carbon-graphite material which is selectively wound within the optical fibers (22) in the coil assembly and/or is wound about the interior and exterior circumferences of the coil assembly.

Abstract: A multisensor includes a ring-like piezoelectric drive. The ring, which may comprise a closed configuration formed of straight ring segments, surrounds a rotor assembly formed of a pair of rotors, each having a central hub. Vanes extend radially from the central hubs of the rotors to the inner surface of the ring and are fixed to the ring adjacent the intersections of the substantially-straight ring segments. The ring is formed of a laminate of layers of piezoelectric material. Adjacent layers are of opposite piezoelectric polarity whereby an a.c. signal drives the alternating expansions and contractions of pairs of laminated layers.

Abstract: A system for measuring changes in an environmental parameter such as displacement, velocity, acceleration, or pressure, includes a laser for providing a pulsed, coherent light signal, and an interferometer having a first and second optical legs of unequal optical path lengths. The signal is split into first and second beams that are directed into the first and second optical legs. Either a fixed mirror disposed on a frame or a moving mirror on one side of the proof mass reflects the first beam received at the end of the first optical leg. The frame also suspends a proof mass at opposite ends. An optical pick-off embodied in a movable mirror formed on the proof mass reflects the second beam received from the end of the second optical leg. The proof mass with mirror moves in response to changes in the value of the parameter to be measured.

Abstract: A fiber optic accelerometer includes a ring that is twistably-responsive to an orthogonally-directed acceleration force. The ring is mounted by means of either an inner or an outer peripheral flange comprising an annular washer to one of two concentric walls of a disk-like casing. The walls apportion the interior of the casing into a disk-like central section and a surrounding annular section. The ring is appropriately flange-mounted and proportioned to present a moment of inertial that subjects the ring to twisting in the presence of acceleration along the sensitive input axis. Flat spiral coils of optical fiber are fixed to the top and bottom of the ring. Each coil forms a portion of the leg of an interferometer for generating a signal responsive to the acceleration input.

Abstract: The invention is a method and apparatus for determining the phase difference of light waves after propagating through each of one or more two-path pairs, a two-path pair being two optical transmission paths connecting a common entry point to a common exit point. Coherent light pulses of predetermined duration are fed into the entry point of each two-path pair in a group of two-path pairs at predetermined time intervals, the pulse duration being subdivided into a plurality of predetermined time segments. The light has a different frequency during each time segment. The light pulses at the exit points of the two-path pairs are delayed by predetermined time increments and then combined into a combination light signal. The combination light signal is converted into an electrical signal, the amplitude of the electrical signal as a function of time being proportional to the combination-light-signal power as a function of time.

Abstract: A sensor coil for a fiber optic gyroscope. At least one dummy layer forms an integral structure with, and shares the thermal expansion characteristics of, a potted coil comprising a plurality of layers of windings of a first optical fiber. In a gyroscope, the potted coil is arranged to receive the output of a source of optical energy as a pair of beams that counter-propagate therein and to provide the resultant interference pattern, as gyro output, to a detector. The dummy layer displaces layers or windings of the potted coil from regions likely to contribute to Shupe bias effects.

Abstract: A spool for receiving a fiber optic sensor coil includes a single, substantially-planar mounting flange and a central hub. The coil can be directly wound upon the hub. The coil is mounted transverse to the plane of the mounting flange and is unconfined in that direction as the surface of the hub is substantially non-adhesive with respect to the inner layer of the coil. This allows axial coil expansion with increases in temperature without generating gyro bias errors. The device is also substantially free from vibration-induced bias errors due to the relatively high resonant frequency (vis a vis environmental vibration) of the integral spool-plus-coil structure.

Abstract: A sensor for measuring angular rotation rates about three orthogonal axes is based upon sensing Coriolis acceleration forces with a pair of nearly-identical rotors coupled coaxialy by a torsion spring and counter-oscillating in rotation. The torsional oscillator is mounted within a case by means of radial vanes, each comprisig two piezoelectric ceramic plates bonded to a thin metal core responsive to drive signals and providing rotational vibration isolation. The arms of the rotors are designed as piezoelectric open loop accelerometers. Electrodes of selected configurations are mounted to the outer surfaces of the planar members to collect charge indicative of Coriolis accelerations proportional to the angular rotations about the orthogonal axes.

Abstract: A sensor coil for a fiber optic gyroscope. The coil is formed on a spool of carbon composite material or of another material whose coefficient of thermal expansion approximates that of the overlying windings of the glass optical fiber. The windings are potted in an adhesive material. Various bias effects are addressed by the coil design. The close matching of the thermal expansion characteristics of the spool and the fiber windings as well as proper selection of the coil potting material minimize the Shupe-like bias caused by thermal stress that would be otherwise exerted by a standard metallic spool. By careful selection of potting material (particularly its modulus of elasticity) vibration-induced bias, coil cracking, degradation of h-parameter and temperature-ramp bias sensitivity are also minimized.

Abstract: A three axis inertial measurement unit is shown having a low inertia mechanical oscillator formed from two platforms counterbalanced against each other. Each platform is dithered at its natural frequency about a single torsional axis. A plurality of accelerators are mounted upon at least one of the counterbalanced platforms with each accelerometer having at least an input axis mounted at a predetermined angle to the torsional axis and to the platform. Each platform has a three legged, Y-shaped mounting member with a rotor member positioned between the legs of the mounting member. Web members which form the legs of the mounting member join the rotor member to the Y-shaped mounting member. Additionally, driving webs are mounted on each side of the web members for further joining the mounting member to the rotary member.

Abstract: A vibrating rotation rate sensor of the type that includes a generally-planar, H-shaped frame of piezoelectric material such as quartz. A first set of drive electrodes is fixed to a pair of upper tines and a second set of pickoff electrodes is fixed to a pair of lower tines. An array of control electrodes is fixed to the upper tine pair adjacent the cross-piece of the H-shaped frame. The control electrodes permit the application of control signals for nulling Coriolis-induced out-of-plane vibration of the upper tines allowing use of a resonant frame.