Abstract: A portable X-ray unit, of a relatively light-weight, occoping a volume of less then one-half a cubic foot containing an x-ray head assembly, a unique Marx generator, a plurality of spark-gap switches and control electronics is disclosed. The Marx generator allows for the development of a relatively high voltage in excess of 100 kV, yet allows for the discharge thereof within the nanosecond range. The Marx generator is enclosed by an acrylic insulator that cooperates with an aluminum enclosure, which functions as a return current path for the capacitors in the Marx generator and also as a shield against the escape of electromagnetic radiation from the pulsed x-ray unit. The Marx generator and spark-gap switches are confined within the pressurized chamber that may contain nitrogen gas to reduce the separation of the gap in the spark-gap switches.

Abstract: An optoelectronic system is provided for converting analog electrical sigs into digital electrical signals. An optical carrier produced by a laser source is separated into spectral components. An electro-optical modulator modulates the optical carrier with a radio frequency input signal so as to produce an amplitude modulated optical output signal. The optical output signal is then outputted to a wavelength division demultiplexer which separates the output signal into a plurality of separate channels, based on wavelength. Photodetectors connected to each of the channels convert the separated signals into analog electrical signals. These analog electrical signals are outputted to a plurality of standard analog to digital converters which convert the analog electrical signals into digital signals.

Abstract: An infrared fiber optic coupler and a method for making an infrared fiber optic coupler are disclosed.

Abstract: A grating sensor system for simultaneously determining strain and temperature is disclosed, which system comprises: a light source for providing a continuous broadband light; a single mode fiber coupled to the light source; a hybrid fiber grating sensor written into the single mode fiber, the sensor comprised of a long period grating having a first center wavelength and first and second fiber Bragg gratings respectively having second and third center wavelengths for respectively reflecting light therefrom at about the second and third center wavelengths, with the first center wavelength being between the second and third center wavelengths, the long period grating producing a broadband power loss around its first center wavelength, the first center wavelength shifting with strain and temperature, the sensor measuring the effect of the long period grating wavelength shift on the relative intensities of the light reflected from around the second and third wavelengths; an optical analyzer responsive to the refle

Abstract: A system that synchronously segments a speech waveform using pitch period and a center of the pitch waveform. The pitch waveform center is determined by finding a local minimum of a centroid histogram waveform of the low-pass filtered speech waveform for one pitch period. The speech waveform can then be represented by one or more of such pitch waveforms or segments during speech compression, reconstruction or synthesis. The pitch waveform can be modified by frequency enhancement/filtering, waveform stretching/shrinking in speech synthesis or speech disguise. The utterance rate can also be controlled to speed up or slow down the speech.

Abstract: An optical filter that uses multiple reflections to provide spectral bandpass filtering of ultraviolet, visible and infrared radiation with a very high transmission of wavelengths within a selected passband coupled with exceptional off-band rejection. The reflection filter uses dielectric-coated spherical reflectors or mirrors manufactured with absorbing glass substrates. The multiple-pass feature of the reflection filter is achieved using a traditional long-path absorption cell such as a White Cell or Wilkes Cell. The light transmitted through the reflection filter is only that light which has undergone multiple reflections as the wavelengths of high mirror reflectivity reflect off the dielectric-coated substrates. All remaining light at wavelengths corresponding to high mirror transmission is attenuated by absorption in the mirror substrate.

Abstract: A channelized protection circuit for protecting the front-end of a receiver rom the detrimental effects of interference signals within the bandwidth of received signals is disclosed.

Abstract: A high-resolution range imaging system and method can sense the presence of and determine the position or range of each point on the surface of an object through triangulation calculation methods. A moving pattern of light is projected onto the object to be imaged. This resulting moving light pattern, comprised of vertical planes of light, is achieved by projecting light through a moving mask having a DeBruijn code formed thereon, the light being projected through the mask to provide blurring. The light source has a slit or the like which is between one and two times as wide as the narrowest stripe on the mask. Each light ray of the incoming reflected light pattern is recorded by a detecting device, such as a charge coupled device camera (CCD camera). The detecting device measures the blurring of the light pattern and records the associated gray-scale value, a measurement of the reflected light intensity, at each pixel location.

Abstract: A system and method for providing accurate measurements of the reflected wavelengths from multiple strings of fiber Bragg grating (FBG) elements using a single scanning optical filter and an isolated duplicate reference string of FBG elements. A reference string of FBG elements permits precise long-term wavelength determination of sensors by providing real-time adaptive calibration adjustments to correct for any nonlinearities in the response of the single scanning optical filter.

Abstract: An optical fiber which includes a light transmitting center portion, a prcting layer and a stress preventing layer. The protecting layer concentrically surrounds the center portion, and reduces the effect of environmental factors on the center portion. The stress preventing layer concentrically surrounds the center portion and is positioned between the protecting layer and the center portion. The stress preventing layer has a Young's Modulus substantially lower than the Young's Modulus of the protecting layer, for preventing stress from being transferred from the protecting layer to the center portion. The optical fiber can be used in a filler optic sensor system.

Abstract: An ultraviolet laser system is disclosed for generating an ultraviolet frency in the spectral region between 223 nm and 243 nm by mixing the tunable output of a Ce.sup.3+ :LiCAF laser with the 1064 nm radiation from a Nd:YAG pump laser in a BBO nonlinear crystal.

Abstract: A distributed optical fiber sensor system including a patterned array of kly reflecting broadband gratings or other sensors serially disposed along a common fiber. The laser sources are multiplexed onto the fiber and are propagated through a directional coupler toward the sensors. The return signals are directed by the directional coupler to a demultiplexer that separates the signals by center frequencies and sends each to a respective detector. All reflection signals generated by a single input pulse of a given wavelength are detected prior to the input coupling of the next input pulse of that wavelength, the input pulse repetition period being T.gtoreq.Nt.sub.0, N being the number of grating sensors and t.sub.0 being their spacing or separation in optical propagation time.

Abstract: A mirrorless, distributed-feedback (DFB), ultraviolet, tunable, narrow-liidth, solid state laser for remote sensing and medical applications is disclosed. Optical pumping in the DFB laser is accomplished using a frequency quadrupled, 10 Hz., Q-switched, Nd:YAG laser operating at 266 nm. The pump beam is diffracted off a grating (2400 grooves per mm.) into two parts. The two beams are subsequently recombined at the side face of the Ce:doped crystal (8 mm.times.8 mm.times.30 mm) at an angle of about 2.theta.(about 81 degrees). The resulting spatially periodic excitation within the Ce-doped gain medium due to the interferring pump beams determines the operating wavelength of the DFB laser.

Abstract: A system for the in-situ detection of chemicals, including water, in soil comprises: a penetrometer for penetrating the soil, the penetrometer including interior and exterior surfaces, and a window for allowing infrared radiation to be transmitted between the interior and exterier surfaces of the penetrometer; a driver for driving the penetrometer into the soil to a plurality of different depths; a source for providing infrared radiation which passes through the window to irradiate the soil adjacent to the window; an infrared transmitting chalcogenide optical fiber; an optical system disposed within the penetrometer adjacent to the window for transmitting infrared radiation from the source through the window into the soil and for collecting infrared radiation reflected from the soil back through the window into a first end of the chalcogenide fiber; and a spectrometer coupled to a second end of the infrared transmitting chalcogenide optical fiber for receiving and analyzing the reflected infrared radiation pa

Abstract: A transducer and measurement system includes a fiber Bragg grating which a regular variation of spacing of partially reflecting surfaces, known as a chirp, either formed or induced therein and which is capable of reflecting energy having a predetermined wavelength. When the fiber Bragg grating is subjected to a strain, such as by a change in dimension or shape of a transducing element to which it is attached with change of a physical parameter to which the transducing element or the fiber Bragg grating is exposed, the location within the fiber Bragg grating which effectively reflects the predetermined wavelength will be formed (e.g. when the chirp is induced) or altered as the strain alters spacing of partially reflecting surface within the fiber Bragg grating allowing long optical fibers, such as are used in magnetometers and hydrophones, to be simulated with short optical fibers including a fiber Bragg grating.

Abstract: A signal processing apparatus for providing accurate electrical phase difference measurement of multiple concurrent signal inputs is disclosed. Phase measurement of an individual signal input is accomplished utilizing an efficient spatial sampling scheme. In operation, measurement and reference wideband RF inputs, differing primarily in phase over frequency, are respectively applied to two RF Channelizer components. Each Channelizer separates the composite input bandwidth into multiple time-coincident frequency output channels. Corresponding pairs of output channels then phase modulate a common independent carrier which propagates to the detection plane of a photodetector array forming a spatial interference pattern along one axis for each frequency channel number. A preferred detector element scaling relative to the interference pattern affords efficient phase difference measurement incorporating three detector elements at each frequency channel.

Abstract: An optical system for detecting perturbations indicative of the performance f the piece of equipment being monitored is disclosed. The optical system comprises sensors each of which use Bragg gratings induced therein and wherein the Bragg gratings are arranged into a preselected distribution and each Bragg grating returns, when subjected to incident light, a narrowbeam signal identified by a predetermined wavelength. The optical system utilizes at least one interferometer whose operation is interlinked with optical multiplexing techniques, such as differentiate-cross-multiplying and time-division multiplexing.

Abstract: A hydrophone group for shallow towed applications in less than 50 feet of ter. The hydrophone group has a series of hydrophones connected by relatively insensitive fiber optic interconnects. The individual hydrophones are sufficiently sensitive such that the interconnecting optical fiber does not introduce excessive noise. Each hydrophone is basically a sensing fiber wrapped around an air-backed mandrel. Each air-backed mandrel is formed of an extended solid frame substantially non-compliant along a longitudinal axis. The extended solid frame is provided with a channel around the periphery thereof. The channel extends substantially the entire length of the extended solid frame. A flexible outer covering surrounds the extended solid frame. The flexible outer covering is highly compliant in a radial direction extending from the longitudinal axis. The air-backed mandrel has a high frequency mechanical resonance.

Abstract: A filtered cascaded synchronized nonlinear system includes a nonlinear transmitter having stable first and second subsystems. The first subsystem produces a first transmitter signal for driving the second subsystem, and the second subsystem produces a second transmitter signal for driving the first subsystem. A first filter filters the second transmitter signal to produce a filter output signal. A subtractor subtracts the filter output signal from the second transmitter signal to produce a transmitter output signal which is transmitted to a nonlinear cascaded receiver. The receiver includes an adder for summing the received transmitter output signal with a receiver filter output signal to restore frequencies that were subtracted from the second transmitter signal in order to produce a first receiver drive signal. The receiver includes cascaded third and fourth subsystems that are respective duplicates of the first and second subsystems.

Abstract: A high power, highly efficient, phase-stable frequency-multiplying magnicon microwave amplifier is disclosed having efficiencies that exceed 60%. The magnicon amplifier has an output cavity that receives an electron beam that is deflection modulated by the drive, gain and penultimate cavities of the magnicon amplifier. The output cavity is dimensioned so as to operate in a TM.sub.m10 mode, where m is an even integer greater than two. The output cavity is selected to preferably have an operating frequency f.sub.o which is twice the cyclotron frequency f.sub.c of the output cavity.