Abstract: A method of remotely measuring the diffuse attenuation coefficient K of ocean water from an airborne platform such as an aircraft. By directing a pulsed laser beam having a wavelength .lambda..sub.0 from the platform into the water, the beam interacts therewith to produce inelastic Brillouin backscatter signals at the wavelength .lambda..sub.1, where .lambda..sub.1 .noteq..lambda..sub.0. The desired backscatter propagate generally oppositely to the direction of propagation of the pulsed laser beam so that the backscatter can be received and collected at the platform. The upwelling optical energy includes the desired backscatter signals, which are separated out from the remainder of the upwelling optical energy. The separated backscatter signals are converted to equivalent electrical signals and periodically analyzed to generate therefrom the diffuse attenuation coefficient of the ocean water at the .lambda..sub.1 wavelength at periodic depths beneath the water surface.

Abstract: To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a laser beam having a high power or intensity is split into two parts, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water, and the reference beam into a reference sample of water having a known temperature T.sub.r. The intensities of the two beams, which exceed a predetermined threshold are sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two phase-conjugate beams. The two phase-conjugate beams are mixed to produce a heterodyne frequency that is proportional to the difference in temperature T.sub.s and T.sub.r. The frequency difference is converted into a temperature value equal to the value of T.sub.s.

Abstract: Apparatus for measuring the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water comprises a pulsed laser having a high intensity (power per unit area) output beam split into two sub-beams, one of which is a probe beam directed into the ocean water. The intensity of the output beam pulses exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering within the medium and to produce therefrom a phase-conjugate beam which propagates along the path of the first sub-beam but in the opposite direction. The second sub-beam is reflected by a mirror to and combines with the PC beam and the combined beams are mixed at the cathode of a photodetector which produces a heterodyne frequency that is proportional to the temperature T.sub.s. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: Apparatus is disclosed for remotely sensing the unknown subsurface temperature T.sub.s of a bulk transparent medium, such as ocean water, using a cw laser beam and a pulsed laser beam. In one embodiment the cw output of a continuous laser is split into two sub-beams. An optical amplifier periodically amplifies the first such sub-beam thereby generating an intense pulsed laser beam having a plurality of pulses with the same wavelength as the cw laser beam. The intensity level of the pulses is sufficient to produce stimulated Brillouin scattering when focussed into the ocean water. The pulsed laser beam is directed into the water thereby generating an intense return phase-conjugate beam propagating along the path of the pulsed laser beam but in the opposite direction thereto. The phase-conjugate beam and the second sub-beam are mixed at the cathode of a photodetector to produce a heterodyne frequency proportional to the temperature T.sub.s.

Abstract: To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a high intensity pulsed laser beam is split into two sub-beams, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water of unknown temperature, and the reference beam into a reference sample of water having a known temperature T.sub.r. The irradiance of the two pulse beams exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two return phase-conjugate (PC) beams. A photodetector mixes the two PC beams and produces a heterodyne frequency that is proportional to the difference in temperatures T.sub.s and T.sub.r. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: A telescopic mast system has a base tube, a plurality of axially movable coaxial inner tubes nestable successively within each other and within the base tube, and a winch supported at the lower end of the base tube with a pair of preferably wire ropes driven thereby for extending and retracting the inner tubes. The base and inner tubes have collars at their respective ends, the collars of adjacent tubes engaging each other to limit extension thereof and to provide additional structural support during application of bending loads on the mast system. The ropes are connected to pulleys mounted near or within tube collars so that the ropes and pulleys are totally enclosed within the mast system. As the winch is rotated in one direction, the ropes axially move the inner tubes from a nested or stowed position within the base tube to a fully vertically extended operational position.

Abstract: A linkage device connectable between adjacent ends of a tubular support member and payload member is adapted to rotate the payload member through approximately 180.degree. about the end of the support member between inoperative and operative positions by movement of an actuating rod longitudinally within the tubular member. The linkage device comprises first and second frames secured to adjacent ends of the members and four bars pivotally connected at opposite ends to corners of the frames, the first pair of bars extending within the frames and the second pair extending outside the frames. The actuating rod is connected to the first pair of bars and rotates them about their pivotal connection to the first frame when the rod is moved longitudinally within the tubular member. Both pairs of bars cause the payload member to rotate about the end of the support member through 180.degree. and into an operative position in longitudinal alignment with the support member.

Abstract: A method of accelerating the training of an artificial neural network uses a computer configured as an artificial neural network with a network input and a network output, and having a plurality of interconnected units arranged in layers including an input layer and an output layer. Each unit has a multiplicity of unit inputs and a set of variables for operating upon the unit inputs to provide a unit output. A plurality of examples are serially provided to the network input and the network output is observed. The computer is programmed with a back propagation algorithm for adjusting each set of variables in response to feedback representing differences between the network output for each example and the desired output. The examples are iterated while those values which change are identified. The examples are reiterated and the algorithm is applied to only those values which changed in a previous iteration.

Abstract: A winch having a torodially-shaped drum with an axis of rotation and at least one cable wound on the drum having a cable length extending from the drum parallel to and substantially equally spaced from said axis at all times during rotation of the winch. The drum has negatively-curved and positively-curved surfaces joined at a common edge, the cable being wound on the negatively-curved surface and directed therefrom over the positively-curved surface in a direction parallel to the drum axis. This drum is used advantageously with the mast system described in application Ser. No. 246,112.

Abstract: The etendue (throughput or area-solid angle product) of a high resolution interferometer is maintained at a substantially high level by use of a transparent chamber defined by a highly reflective internal surface, the chamber being located at the input to the interferometer. The chamber has an input aperture to admit light into the chamber and an output aperture or exit opening to pass light to the interferometer. By integrating the input light through multiple reflections thereof within the chamber until it exits to the interferometer, the etendue of the latter is substantially enhanced.

Abstract: A foreshortened log-periodic antenna which includes variously configured dipole elements and a tapered feedline is disclosed. The dipole elements are arranged in four regions. A first region, located nearest to a feed end of the antenna, includes solid triangular dipoles having constant base-to-height ratios. A second region, adjacent to the first region, includes solid triangular dipoles having decreasing base-to-height ratios. A third region, located adjacent to the second region, includes a single linear dipole. A fourth region, located adjacent to the third region and nearest to a low frequency end of the antenna, includes foreshortened dipoles. The feedline may be implemented either in coaxial or microstrip form so that a lower characteristic impedance is pressed at the feed end of the antenna than at the low frequency end of the antenna.

Abstract: Subsurface waves in an ocean are created by the turbulence in a submarine's wake. These waves can be remotely detected by a search submarine by monitoring subsurface water temperatures using a laser. A pulsed laser beam is directed into the water to at least the depth of the thermocline and an analysis is made of the resultant Brillouin and Rayleigh backscatter components. Wavelength shifted Brillouin scatter is mixed with the unshifted Rayleigh scatter in a self-heterodyne manner for each volume element of illuminated water, and the frequency of the heterodyne signal is measured and converted into equivalent temperature values. This produces the desired temperature-depth profile of the water enabling detection of the first submarine by tracking the internal waves at or near the ocean thermocline.

Abstract: The pulse signal generator produces a repetitive pulse output signal consisting of repetitive pulse groups which may have either constant pulse intervals or staggered pulse intervals. Each pulse in the group also has an adjustable pulse width and may be time referenced to a clock pulse signal. The pulse generator employs cascaded stages of individual pulse generators: one stage for each pulse in the group. The first stage generates the first pulse in each group of n pulses and additionally controls the pulse group repetition interval and the pulse width of each pulse.A first counter/comparator generates a first start-pulse, when it counts N.sub.1 clock pulses. The start-pulse resets the first counter and triggers an output bistable (multivibrator) circuit, which initiates the leading edge of the first output pulse of the group. When N.sub.

Abstract: A technique for accurately controlling both the pulse repetition interval and pulse width of a pulse signal generator which uses a crystal oscillator to maintain a very accurate time base. Two separate digital counters clock-in the clock pulses. When the desired number of clock pulses are registered by the first counter, a first digital comparator generates a start pulse which resets the first counter and triggers an output flip-flop. The change of state in the flip-flop enables the second counter to begin its count. When the desired number of clock pulses are registered by the second counter, a second digital comparator generates an end pulse which resets the second counter and triggers the flip-flop a second time. The second change of state of the flip-flop disables the second counter until the first comparator generates a new start pulse.

Abstract: The subsurface temperature of a body of water such as an ocean is measured remotely by directing a laser beam deeply into the water and analyzing the resultant Brillouin and Rayleigh backscatter components. Wavelength shifted Brillouin scatter is mixed with the unshifted Rayleigh scatter in a self-heterodyne manner for each volume element of illuminated water and the frequency of the heterodyne signal is measured. This produces the desired temperature-depth profile of the water.

Abstract: Subsurface waves in a body of water such as an ocean caused by a submarine are remotely nonacoustically detected by monitoring subsurface water temperatures using a laser. A pulsed laser beam is directed into the water to at least the depth of the thermocline and an analysis is made of the resultant Brillouin and Rayleigh backscatter components. Wavelength shifted Brillouin scatter is mixed with the unshifted Rayleigh scatter in a self-heterodyne manner for each volume element of illuminated water, and the frequency of the heterodyne signal is measured and converted into temperature. This produces the desired temperature-depth profile of the water enabling detection of internal waves generated by submarines.

Abstract: A universal demodulator programmable for any digitally modulated carrier signal having a known constellation format which can be characterized by a unique constellation pattern of phase-amplitude states. The demodulator also generates phase and gain-error signals for locking onto the phase and amplitude of the digitally modulated carrier. The demodulator splits the received digitally modulated carrier signal into an inphase component, D.sub.x, and a quadrature-phase component, D.sub.y. Using a preprogrammed memory device keyed to the identified modulation format, each D.sub.x signal is mapped into one of a plurality of one-dimensional zones each having R.sub.x center values. Using a second preprogrammed memory device also keyed to the identified modulation format, each D.sub.y signal is similarly mapped into a plurality of orthogonal one-dimensional zones having R.sub.y centers. Each pair of R.sub.x and R.sub.

Abstract: The efficiency of an optically pumped solid state laser is substantially improved with a controlled geometry fluorescent converter between the pump light source and the lasing medium. Fluorescent materials have the capability of absorbing broadband pumping radiation, shifting it in wavelength and re-emitting it in the absorption band of the selected solid state laser medium. Use of angular formations having the converter surface facing the laser medium reduces fluorescent light trapping within the converter due to internal reflection thereby greatly increasing the total light output of the converter and thus the efficiency of the laser.

Abstract: An adjustable optical mounting assembly, particularly suited for folding or periscope optics, provides for optical beam motion in three axes using a bearing having a spherical surface. This invention greatly simplifies the mount mechanism and operting procedure, reduces the size, and provides enhanced stability and lockability relative to comparable conventional devices.

Abstract: The foreshortened dipoles of the antenna described in U.S. Pat. No. 3,732,572 are further substantially shortened with a new construction in which each radiating element comprises two portions. A planar rectangular body electrically connects to the feed point by a stem portion which attaches to the rectangular body at the farthest point from the feed point and is spaced slightly from the plane of the body to electrically isolate the two portions.