Abstract: A fiber optic hydrophone is formed as a single interferometer having widely separated interferometer segments formed in each of a pair of optical fibers. The interferometer segments are designed to allow averaging of the effects of local noise sources over a broad area in order to increase the acoustic signal-to-noise ratio. The interferometer segments also allow deployment of the hydrophone around sharp bends. A first optical fiber is formed into a plurality of spatially separated outer coils. A second optical fiber is formed into a plurality of inner coils corresponding to the outer coils. The inner and outer coils are preferably arranged in concentric pairs to form a plurality of sensor segments. A plurality of spacers is arranged such that a spacer is between successive sensor segments.

Abstract: A slip ring base assembly utilizing a novel construction and manufacturing technique uses a molded or extruded base profile that can be manufactured in various shapes and configurations and is flexible enough to conform to many diameters. A rigid backing is provided, as may be a suitable hub, for stiffening and reinforcing the base profile. Strip or round conducting rings whose surface may be flat, grooved or channeled, are inserted on the base member.

Abstract: A method and apparatus for testing materials for use in a laser resonator includes selecting a test fixture apparatus having a housing with an internal chamber volume selected to approximate the internal volume of a predetermined laser resonator and having a pair of sealed windows therein which are removably attached to the housing and having optical coatings selected to match the coating on the optics of a laser. The housing has a removable cover and a gas purging opening. A laser of a predetermined wavelength and power is mounted adjacent the test fixture and is aligned for directing the laser beam through both of the windows of the test fixture. A material is placed in the test fixture and a laser beam directed through the coated windows for a predetermined period of time and thereafter the coated windows are examined for damage or contamination. The test fixtures are also cleaned and certified prior to testing so that a preselected test fixture can determine damage for selective materials used therein.

Abstract: An active recognition system comprises a transceiver, tracking electronics, an optical processor, and a data handler. The transceiver transmits chirped pulses and receives a series of reflected ?replicas of the chirped pulse! replica pulses from ?features of! an object ?of interest!. The tracking electronics controls the transceiver to determine object range for gating the optical processor. The optical processor includes a "signal" Bragg cell driven by the reflection signal so that ?a! throughgoing light ?beam! is angularly redistributed as a function of the local spatial frequency of the acoustic waveform within the modulation aperture of the signal Bragg cell. At a first focal plane, the light defines a one-dimensional light distribution that includes moving spots that correspond to respective reflection replicas.

Abstract: A vibratory rotation sensor that utilizes non-capacitive mechanical displacement detectors (24) to detect the flexural standing wave pattern in a hemispherical resonator (14). In a preferred embodiment, a plurality of tunneling transducers (24) are positioned around the hemispherical resonator (14) to detect the standing wave. A "force-to-rebalance" mechanization mode is preferably used for calculating the sensor's rate of rotation, with a transducer (24) placement that allows for constant calibration of the sensor's scale factor. In addition, a pickoff transducer orientation is provided that allows for simultaneous calculation of the sensor's rotation angle and any linear acceleration that is exerted on the sensor's hemispherical resonator (14), thereby allowing the sensor to be simultaneously used as a rotation sensor and an accelerometer.

Abstract: The invention utilizes a sensing body having a non-zero product of inertia to sense acceleration when spun about the y'-axis of an x'-y'-z' Cartesian coordinate system. The product of inertia is computed with respect to an x-y-z coordinate system fixed in the sensing body, the z-axis being in the x'- z' plane, they and y' axes being aligned in the absence of acceleration. The sensing body is pivotally attached to a platform and pivots about an axis parallel to the z-axis. A torquing device applies a torque about the z-axis to the sensing body sufficient to cause the angle between the y-axis and the y'-axis to be zero in the absence of acceleration when the sensing body is being spun at predetermined rate. The accelerometer also includes an orientation sensor which provides a measure of the angle between the y-axis and the y'-axis. A drive assembly rotates the platform about the y'-axis.

Abstract: A laser apparatus includes a hollow cylindrical solid state laser medium and an optical resonator having reflective surfaces at each end of the laser medium in the axial direction of the laser medium for causing a light emitted into the laser medium to travel back and forth along the elongated axial direction of the laser medium. One of the reflective surfaces of the optical resonator is shaped to reflect the beam at an angle to the beam impinging thereagainst to thereby walk the beam tangentially around the hollow cylindrical solid state laser medium at a fixed radial distance from the elongated axis of the laser medium. An exit slot is formed in one of the reflective surfaces. A pumping means for exciting the laser medium includes at least one flashlamp positioned adjacent the laser medium along the laser medium axis through the hollow cylindrical portion of the laser.

Abstract: Radar emitter carrier frequency or pulse time-of-arrival measurements are used to resolve the differential phase measurement ambiguities on a long baseline interferometer (LBI) used to passively locate the emitter. The LBI requires only two pulses to precisely measure the change in signal angle of arrival caused by observer motion relative to the emitter, whereas frequency Doppler needs tens of pulses, and time Doppler may need hundreds of pulses, to estimate the same change to the same accuracy. Therefore Doppler measurements are made only to the accuracy needed to estimate the angle change accurately enough to differentially resolve the LBI.

Abstract: A binocular night vision device (BNVD) includes a pair of night vision monocular scopes which pivotally and adjustably depend from a central housing portion. The central housing portion and the two night vision monocular scopes cooperatively define a singular gas envelope, which allows the entire BNVD to be purged of moist air and back filled with dry nitrogen gas to prevent fogging while requiring only a single purging port. Further, the central housing portion contains a single battery and a single voltage step up circuit powering both image intensifier tube modules of the two monocular night vision scopes. In order to provide for interpupillary distance adjustment, the central housing portion and each of the monocular night vision scopes defines a sealed pivot mechanism which also allows for electrical connection between the central housing portion and each of the night vision scopes.

Abstract: A photocathode which is responsive to ultraviolet light to release photoelectrons includes a supportive window layer of sapphire and a single-crystal active layer of AlGaN. Interposed between the window layer and the active layer is an interface layer which insures a low population density of crystalline defects at the interface of the interface layer with the active layer and in the active layer itself. Consequently, the photocathode is an effective emitter of photoelectrons in the transmission mode.

Abstract: A fiber optic sensor comprises a first optical signal source that produces an optical signal of wavelength .lambda..sub.1 and a second optical signal source that produces an optical signal of wavelength .lambda..sub.2. A first WDM coupler is connected to the first and second optical signal sources to combine signals output therefrom. An optical fiber is connected to the WDM coupler to guide the combined optical signals therefrom. A second WDM coupler is connected to the optical fiber to separate the optical signals of wavelength .lambda..sub.1 and .lambda..sub.2. A fiber optic sensor array containing a plurality of fiber optic sensors is connected to the second WDM coupler and arranged such that optical signals of the wavelengths .lambda..sub.1 and .lambda..sub.2 are directed to different fiber optic sensors in the fiber optic sensor array. A third WDM coupler is arranged for combining signals of wavelength .lambda..sub.1 and .lambda..sub.2 output from the fiber optic sensor array.

Abstract: A gas analysis apparatus using multiple orifices of preselected sizes to attain a calculated gas mixing ratio for diluting an oxygen sample to a concentration less than 95% prior to application to a limiting current oxygen sensor. The apparatus comprises a regulator for regulating the pressures of incoming flows of air and oxygen sample to be measured, a valve for allowing the concentration of the air sample to oxygen sample to be measured, and a system for calculating the air sample/oxygen sample mixing ratio based on the known air sample concentration and then, based on the known air concentration and calculated mixing ratio, calculating the unknown sample concentration from the output of the oxygen sensor.

Abstract: Method and apparatus for passive emitter location which overcomes the time to range and other restrictive limitations of passive tracking systems by combining pulse frequency, time of arrival and bearing or angle of arrival measurements to obtain a range measurement at each parameter update. No specific observer motion is required and relatively few restrictions on emitter motion are present in order to obtain an accurate determination.

Abstract: A loop controller for a fiber optic gyroscope employs distributed data processing to compress numerous additional useful functions into each loop transit time. The architecture of the loop controller includes a field programmable gate array for generating variables of varying sign. In addition, the array acts to buffer the transmission of parameters between the gyro processor and an auxiliary processor. The auxiliary processor updates such parameters (which do not require updating every loop transit time) and a number of such parameters are multiplied by values generated by the array in operations performed by the gyro processor that replace what would otherwise require throughput intensive test and branch operations. The combination of the off-loading of selected variable and parameter generation and updating with programming of the gyro processor for parallel processing permits the loop controller to perform numerous useful operations not previously possible during a realistic loop transit time.

Abstract: A phase modulator applies sequences of artificial phase shifts in the region of overmodulation between light beams counterpropagating within the sensor coil of a Sagnac interferometer to obtain improved random walk performance. The sequences are composed of phase shifts of .+-.a.pi./2b and .+-.(4b-a).pi./2b where a is an odd integer and b is an integer greater than 1. The waveform for driving the phase modulator is derived from a 2.pi. radian mapping plotted so that adjacent driving signal values differ by a.pi./2b or -(4b-a).pi./2b in a first angular direction and by -a.pi./2b or by (4b-a).pi./2b in the opposite angular direction. Angular transitions about the mapping may be predetermined to generate a deterministic, random, or pseudo-random modulation sequence. In the event that a deterministic sequence is chosen, it is examined for orthogonality properties to assume zero average output bias from crosstalk.

Abstract: An anode structure of the present invention provides radially disposed first vanes and radially disposed second vanes interdigitating with the first vanes. The first vanes and the second vanes are each interconnected by a first strap and a second strap, respectively. The first strap and the second strap are disposed coaxially on the same side of the vane structure and are generally rectangular in cross-section, having substantially parallel facing surfaces. Each of the vanes is generally T-shaped, with a relatively wide first portion and a relatively narrow second portion. The first portion is disposed proximate to an axis of the cavity with the second portion extending radially outward therefrom. The first portion has a radially tapered region extending to an innermost edge of the vanes, disposed completely within a diameter defined by an innermost one of said vanes.

Abstract: A laser system includes an apparatus having a primary laser resonator having a laser medium therein for producing a laser beam of a first wavelength and a second laser resonator optically connected to the primary resonator to allow a portion of the laser energy from the primary laser resonator to pass into the secondary laser resonator. An optical parametric oscillator is located intracavity of the secondary laser resonator and includes a nonlinear crystal for producing a laser beam of a second wavelength therefrom. A coherent beam output is coupled to the optical parametric oscillator for producing an output beam of predetermined wavelength of the second wavelength while blocking the output of the laser beam of the first wavelength so that a dual resonator combines a secondary laser cavity and an optical parametric oscillator to produce a predetermined output wavelength.

Abstract: A fiber optic gyro sensor coil with improved temperature stability for use at temperatures between T1 and T2, T1 being less than -30.degree. C. and T2 being greater than 60.degree. C. The coil is wound with an optical fiber having one or more jackets. The one or more jackets are made of materials having glass transition regions outside the temperature range from T1 to T2.

Abstract: The integrated GPS/inertial navigation apparatus utilizes satellite signals received with two spatially-separated antennas to achieve improved heading estimates for a mobile platform. Each satellite signal comprises one or more component signals with each component signal having a different carrier frequency. The integrated GPS/inertial navigation apparatus consists of a receiver and an inertial navigation system. The receiver measures the carrier phase of each of one or more component signals of one or more satellite signals received by each of the two antennas during successive time periods of duration T.sub.p. Phase measured during a T.sub.p time period is called T.sub.p -phase. Only one component signal of one satellite signal received by one antenna is measured during any T.sub.p time period. The receiver utilizes the T.sub.p -phases of each component signal obtained during a T.sub.k time period to estimate the phase of the component signal at the end of the T.sub.

Abstract: A high efficiency linear amplifier comprises an electron gun assembly having a cathode and an anode, the cathode being operable at a relatively high voltage potential relative to the anode to form and accelerate an electron beam. A control grid is disposed between the cathode and the anode, and is biased relative to the cathode for Class B operation. A high frequency input signal is applied to the control grid to density modulate the electron beam. A shadow grid may be disposed between the control grid and the cathode. A drift tube encloses the beam and includes a first portion and a second portion with a gap defined between the first and second portions. An inductive output cavity communicates with the gap, and the density modulated electron beam passed across the gap and induces an RF electromagnetic signal into the cavity. A multistage depressed collector accepts and dissipates the electrons of the beam which remain after transit across the gap.