Abstract: The design and method of fabrication for an acoustic sensor module for mounting on the hull of a submarine or surface ship is disclosed. The design involves the use of molded alignment structures within a two part rubber shell to reduce tooling requirements and eliminate a significant amount of assembly labor in fabricating hull mounted sonar arrays.

Abstract: Attenuation of an optical signal at the end of an optical fiber is achieved by positioning a high absorption region at the end of the fiber. A first embodiment teaches highly doped cylinders within a tapered end of the fiber. The highly doped cylinders adjacent the light transmitting core serves to absorb light at the end of the fiber. The light transmitting core of the fiber is reduced in diameter due to the tapering, causing the field of light to expand beyond the core. The highly doped cylinders are in proximity to the core due to the tapering. The cylinders, which are preferably heavily doped with a rare earth such as erbium, absorb the escaping light in sufficient quantities, both in the initial pass through the tapered region and again upon reflection of the light at the end of the tapered region, such that the attenuation of the reflected light is within acceptable limits without regard to the condition of the fiber's end surface.

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: The invention is a method and apparatus for generating a pseudorandom sequence of bits. The method comprises the steps of (1) selecting a “0” or a “1” as the next bit of the modified pseudorandom bit sequence if one or more criteria are satisfied, the criteria being based on the measured properties of a plurality of prior bits of the modified pseudorandom bit sequence; otherwise: (2) selecting the next bit of an initial pseudorandom bit sequence as the next bit of the modified pseudorandom bit sequence, the next bit of the initial pseudorandom bit sequence being a function of one or more prior bits of the initial pseudorandom bit sequence.

Abstract: The present invention uses feedback 300 from RF carrier frequency measurements 301 to disassociate the emitter angle-of-arrival component 313 in the ambiguous phase measurement 312 from the initially unknown phase measurement integer ambiguities 314; to then process 302 resolve the ambiguities; and finally to process 303 to obtain the correct emitter AOA. The present invention does this by converting the actual interferometer baselines 315 on which the unassociated pulse 308 phase measurements 304 were made at different emitter frequencies to a baseline set 305 for a single-frequency equivalent interferometer array. This conceptual array has the following property: the phase measurement 306 that would be made on it at the fixed frequency for a signal at the same direction-of-arrival 307 are identical to the actual phase measurements made on the physical array. Because of this equivalency the conceptual array is called the E(equivalent)-array.

Abstract: Micromechanical inertial sensors are formed of a plurality of substantially-planar semiconductor wafers interspersed with oxide layers. The sensitive element is located within an internal aperture of a wafer of the device and is separate therefrom. It is connected to an overlying oxide layer at pedestals that minimize contact area to thereby reduce stray capacitance. Portions of side edges of the various wafers are successively recessed to create topside-exposed wafer sections that permit the grounding of all exposed portions of the device as operational potentials are applied to internal electrodes and sensitive elements.

Abstract: The invention is a method and apparatus for generating a primary pseudorandom bit sequence consisting of a plurality of contiguous P subsequences. Each P subsequence consists of a start sequence of predetermined length followed by a sequence of trailing bits. The method comprises three steps. The first step consists of deriving a feedback bit from each generating sequence in a P subsequence in accordance with a specified rule where a generating sequence is any sequence of contiguous bits in the P subsequence having the same length as the start sequence. The bit that follows a generating sequence is called the trailing bit for that generating sequence. The second step of the method consists of determining a sequence of one or more modifier bits to be used in modifying the P subsequence. The third step of the method consists of modifying the P subsequence utilizing the one or more modifier bits.

Abstract: A method for detecting radiation comprising nine steps is disclosed. Step one, forming a detector having a photocathode (22) with a protective layer (22c) of cesium, oxygen and fluorine; a microchannel plate (MCP) (24); and an electron receiver (26). Step two, receiving radiation at the photocathode (22). Step three, photocathode (22) discharging electrons (34) in response to the received photons. Step four, accelerating discharged electrons (34) from the photocathode (22) to the input face (24a) of the microchannel plate (24). Step five, receiving the electrons (34) at the input face (24a) of the microchannel plate (24). Step six, generating a cascade of secondary emission electrons (36) in the microchannel plate (24) in response to the received electrons (34). Step seven, emitting the secondary emission electrons (36) from the output face (24b) of the microchannel plate (24). Step eight, receiving secondary emission electrons (36) at the electron receiver (26).

Abstract: A clip ring for securing a contact pin in a connector cavity is circumferentially compressible as in prior art clip ring, but includes several beam fingers projecting radially and obliquely outward against the walls of the cavity for a more secure and more stable position of the pin.

Abstract: The invention is a method and apparatus for determining a failure in a subsystem that is part of a system, the system being characterized in terms of a state vector comprising a plurality of state variables. The state vector is updated at times (jK+k)T&Dgr;t using one or more Kalman filter processes, j taking on integer values, K being a predetermined integer, k taking on integer values between 1 and K for each value of j, T being a predetermined integer, and &Dgr;t being a predetermined time interval.

Abstract: A system (10) for manufacturing a photocathode includes a support (12) and a polishing pad (14) disposed adjacent the support (12). The polishing pad (14) is operable to polish the photocathode in response to movable contact of the photocathode relative to the polishing pad (14). The system (10) also includes a rinsing system (16) coupled to the support (12). The rinsing system (16) is operable to deliver a rinsing agent to the polishing pad (14). The system (10) further includes a control system (62) operable to automatically regulate delivery of the rinsing agent to the rinsing system (16) at a predetermined time period.

Abstract: Disclosed is a method for surrounding electrical cable, such as coax cable or twinax cable, with an elastomer to form a twist capsule cable. The cables are placed in a fixture and stretched to a desired tautness using rubber bands at opposite ends of each cable without allowing the cables to sag in the fixture. The cables are clamped into yokes at opposite ends of the fixture. An elastomer, such as silicone, is poured into the fixture and allowed to cure. The portion of the cables within the fixture are embedded into the elastomer after the elastomer cures. Additional length of twist capsule cable can be fabricated by performing a similar process on adjoining sections of cable. The elastomer is then coated with a polyxylylene or similar polymer such as Parylene™ to prevent the elastomer from rubbing on itself when coiled and when uncoiling. Advantageously, any number of cables can be embedded in the elastomer to form the twist capsule cable.

Abstract: The present invention comprises a method for detecting photons and generating a representation of an image. A photocathode receives photons from an image. A power supply to the photocathode is gated such that the photocathode is switched between an on state and an off state. The photocathode discharges electrons in response to the received photons while the photocathode is in the on state. A microchannel plate is located no more than about 125 microns from the photocathode. The microchannel plate has an unfilmed input face and an output face that receives the electrons from the photocathode. The microchannel plate produces secondary emission electrons which are emitted from the output face. A screen receives the secondary electrons and displays a representation of the image.

Abstract: A system and method for improving the accuracy of altitude determinations in an inertial navigation system. The system utilizes pressure measurements which are taken by a barometric altimeter and converted into an estimated pressure altitude using any known pressure-to-altitude conversion. A pressure correction value is then generated using a correction value generating formula that is a function of altitude. The pressure correction value is then multiplied by a pressure offset value for the barometric altimeter to generate a pressure offset error for the barometric altimeter. This pressure offset error is used in the present invention to modify the pressure altitude estimation in order to generate an altitude determination having an improved accuracy. The present invention further determines an amount of observation noise in the barometric altimeter that is a function of pressure noise and altitude, where the altitude estimation is further modified to account for the observation noise.

Abstract: The invention comprises an alignment element for a multiple channel sight and method. In accordance with one embodiment of the invention, an alignment element (456) may comprise a first prism (492) and a second prism (494). The second prism (494) may be disposed proximate to the first prism (492). An adjustment device (506) may rotate the first prism (492) with respect to the second prism (494) to deviate an image of a first channel (54, 56) at an image plane (300).

Abstract: A precision, micro-mechanical semiconductor accelerometer of the differential-capacitor type comprises a pair of etched opposing cover layers fusion bonded to opposite sides of an etched proofmass layer to form a hermetically sealed assembly. The cover layers are formed from commercially available, Silicon-On-Insulator (“SOI”) wafers to significantly reduce cost and complexity of fabrication and assembly. The functional semiconductor parts of the accelerometer are dry-etched using the BOSCH method of reactive ion etching (“RIE”), thereby significantly reducing contamination inherent in prior art wet-etching processes, and resulting in features advantageously bounded by substantially vertical sidewalls.

Abstract: A sensor array includes a fiber optic cable and at least one electro-optical conversion unit connected to the cable. The electro-optical conversion unit includes a housing formed of mating upper and lower covers. The housing includes an interior cavity for receiving a phase modulator module, a strength member and an interferometer formed by fibers connected to various splices and couplers in combination with the phase modulator module. The interior of the housing is filled with a fill material for holding the position of optical fibers to thereby protect against environmental factors such as shock and moisture.

Abstract: A “Rendering Process and Method for Digital Map Illumination Intensity Shading” is disclosed that assigns an illumination intensity to pixels in a video display imaging a mapped terrain. The process comprises the steps of: providing a rectangular grid array of altitude values covering an area to be shaded. Each altitude value has a map position characterized by a coordinate location referenced to a first and second coordinate axes crossing orthogonally at an origin. Each coordinate location has a first and second value. Each first and second value characterizes the distance of the respective coordinate location from the origin. The map area is divided into an array of contiguous triangles. Each triangle area has a perimeter bounded by three straight line segments passing between three coordinate locations. The video display has pixel areas that corresponding to each respective triangle area. A normal vector is calculated for each triangle area.

Abstract: A system for sensing subterranean acoustic waves emitted from an acoustic source includes a plurality of laser sources, a plurality of subterranean optical sensors, at least one optical detector, and electronics. The laser sources each emit light at a different frequency. The subterranean optical sensors receive the light and alter the light in response to the acoustic waves. The optical detector receives the altered light and outputs an electrical signal. The electronics receives the electrical signal and converts it into seismic data format. Preferably, the light emitted from the optical sources is modulated at a plurality of modulation frequencies. The electronics can be used to demodulate the signal. The electronics may demodulate the electrical signal by mixing the signal with periodic waveforms having frequencies corresponding to the modulation frequencies and twice the modulation frequencies.

Abstract: The invention is a method and apparatus for obtaining an accurate value x1c of a variable x1 based on an estimate x1e that is a function of K variables x1, x2, . . . , xk, . . . , xK. The method comprises the steps of (a) obtaining a plurality of estimates x1e, x2e, . . . , xke, . . . , xKe of the variables x1, x2, . . . , xk, . . . , xK over a method-execution time period, the values of the variables x1, x2, . . . , xk, . . . , xK changing or being changed during the method-execution time period; (b) obtaining from an external source the actual values x1a of x1 during the method-execution time period; (c) defining a compensation model &dgr;x1 that is a function of one or more of the estimates x1e, x2e, . . . , xke, . . . xKe of the variables x1, x2, . . . , xk, . . . , xK, the compensation model being further defined by I unknown constants a1, a2, . . . , ai, . . . , aI; (d) applying an operator G to the values of x1e−x1a and &dgr;x1; (e) determining the values of a1, a2, . . . , ai, . . .