Abstract: A method for estimating the size and location of couplings within a waveguide directional coupler is provided. The method is applied to a waveguide directional coupler having a main transmission waveguide connected to an auxiliary transmission waveguide by a plurality of bore hole couplings. The bore hole couplings are in the interior of the waveguide directional coupler and, therefore, are not easily measurable. The invention provides a simple and inexpensive method for measuring the size and location of the couplings without dismantling or destroying the waveguide directional coupler.

Abstract: Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.

Abstract: A system for real-time video image display for robotics or remote-vehicle teleoperation having at least one robot arm or remotely operated vehicle controlled by an operator through hand-controllers, and one or more television cameras and optional lighting elements. The system has at least one television monitor for display of a television image from a selected one of the cameras and the ability to select one of the cameras for image display.

Abstract: Self-collimation of the output is achieved in an unstable resonator semiconductor laser by providing a large concave mirror M.sub.1 and a small convex mirror M.sub.2 on opposite surfaces of a semiconductor body of a material having an effective index of refraction denoted by n, where the respective mirror radii R.sub.1, R.sub.2 and beam radii r.sub.1, r.sub.2 are chosen to satisfy a condition ##EQU1## with a value of geometric magnification ##EQU2## where r.sub.1 and r.sub.2 are the radii of counterpropagating beams at respective mirrors of radii R.sub.1 and R.sub.2.

Abstract: Apparatus and methods for near real-time stereo vision system for use with a robotic vehicle comprises two cameras mounted on three-axis rotation platforms, image-processing boards, a CPU, and specialized stereo vision algorithms. Bandpass-filtered image pyramids are computed, stereo matching is performed by least-squares correlation, and confidence ranges are estimated by means of Bayes' theorem. In particular, Laplacian image pyramids are built and disparity maps are produced from the 60.times.64 level of the pyramids at rates of up to 2 seconds per image pair. The first autonomous cross-country robotic traverses (of up to 100 meters) have been achieved using the stereo vision system of the present invention with all computing due aboard the vehicle. The overall approach disclosed herein provides a unifying paradigm for practical domain-independent stereo ranging.

Abstract: A very high voltage amplifier in which plural cascaded banks of capacitors are switched by optically isolated control switches so as to be charged in parallel from the preceding stage or capacitor bank and to discharge in series to the succeeding stage or capacitor bank in alternating control cycles. The optically isolated control switches are controlled by a logic controller whose power supply is virtually immune to interference from the very high voltage output of the amplifier by the optical isolation provided by the switches, so that a very high voltage amplification ratio may be attained using many capacitor banks in cascade.

Abstract: A high speed read MRAM memory element is configured from a sandwich of magnetizable, ferromagnetic films surrounding a magento-resistive film which may be ferromagnetic or not. One outer ferromagnetic film has a higher coercive force than the other and therefore remains magnetized in one sense while the other may be switched in sense by a switching magnetic field. The magneto-resistive film is therefore sensitive to the amplitude of the resultant field between the outer ferromagnetic films and may be constructed of a high resistivity, high magneto-resistive material capable of higher sensing currents. This permits higher read voltages and therefore faster read operations. Alternate embodiments with perpendicular anisotropy, and in-plane anisotropy are shown, including an embodiment which uses high permeability guides to direct the closing flux path through the magneto-resistive material. High density, high speed, radiation hard, memory matrices may be constructed from these memory elements.

Abstract: This is a method and associated apparatus for accurately and quickly estimating the amplitude, frequency and phase of a signal of interest. The method comprises the steps of, inputting the signal of interest; generating a reference signal with adjustable amplitude, frequency and phase at an output thereof; mixing the signal of interest with the reference signal and a signal 90.degree. out of phase with the reference signal to provide a pair of quadrature sample signals comprising respectively a difference between the signal of interest and the reference signal and a difference between the signal of interest and the signal 90.degree.

Abstract: Surface-emitting distributed feedback (DFB) lasers are disclosed with hybrid gratings. A first-order grating is provided at one or both ends of the active region of the laser for retroreflection of light back into the active region, and a second-order or nonresonant grating is provided at the opposite end for coupling light out perpendicular to the surface of the laser or in some other selected direction. The gratings may be curved to focus light retroreflected into the active region and to focus light coupled out to a point P. When so focused to a point, the DFB laser may be part of a monolithic read head for a laser recorded disk, or an optical coupler into an optical fiber.

Abstract: A uniformly flexible core, and method for manufacturing the same, for use between the face plates of a sandwich structure. The core is made of a plurality of thin corrugated strips, the corrugations being defined by a plurality of peaks and valleys connected to one another by a plurality of diagonal risers. The corrugated strips are orthogonally criss-crossed to form the core. The core is particualrly suitable for use with high accuracy spherically curved sandwich structures because undesirable stresses in the curved face plates are minimized due to the uniform flexibility characteristics of the core in both the X and Y directions. The core is self-venting because of the open geometry of the corrugations. The core can be made from any suitable composite, metal, or polymer. Thermal expansion problems in sandwich structures may be minimized by making the core from the same composite materials that are selected in the manufacture of the curved face plates because of their low coefficients of thermal expansion.

Abstract: A relatively small and low-cost system is provided for projecting a large and bright television image onto a screen. A minature liquid crystal array is driven by video circuitry to produce a pattern of transparencies in the array corresponding to a television image. Light is directed against the rear surface of the array to illuminate it, while a projection lens lies in front of the array to project the image of the array onto a large screen. Grid lines in the liquid crystal array are eliminated by a spacial filter which comprises a negative of the Fourier transform of the grid.

Abstract: Density measurements can be made in a gas contained in a flow through enclosure by measuring the sound pressure level at a receiver or microphone located near a dipole sound source which is driven at constant velocity amplitude at low frequencies. Analytical results, which are provided in terms of geometrical parameters, wave numbers and sound source type for systems of this invention, agree well with published data. The relatively simple designs feature a transmitter transducer at the closed end of a small tube and a receiver transducer on the circumference of the small tube located a small distance away from the transmitter. The transmitter should be a dipole operated at low frequency with the kL value preferably less than about 0.3.

Abstract: A spectral imaging system having an integrated filter and photodetector array. The filter has narrow transmission bands which vary in frequency along the photodetector array. The frequency variation of the transmission bands is matched to, and aligned with, the frequency variation of a received spectral image. The filter is deposited directly on the photodetector array by a low temperature deposition process. By depositing the filter directly on the photodetector array, permanent alignment is achieved for all temperatures, spectral crosstalk is substantially eliminated, and a high signal-to-noise ratio is achieved.

Abstract: A surface emitting laser or SEL having a pair of vertical oscillator mirrors and a pair of integrated 45.degree. beam deflectors etched in a pair of parallel grooves in a broad-area multilayered wafer by tilted ion beam etching. Each SEL has high output power, low threshold current density, relatively high efficiency, and is compatible with large scale optoelectronic integrated circuit technology. One embodiment includes a lattice matched, unstrained AlGaAs/GaAs single quantum well (SQW) optical cavity in a graded index separate confinement heterostructure (GRINSCH). A second embodiment is a 945 nm lattice-mismatched or pseudomorphic In.sub.0.15 Ga.sub.0.85 As/AlGaAs SQW optical cavity SEL in a GRINSCH configuration in which the lattice mismatch is accommodated by elastic deformation of the lattice. Strain-induced reduction of valence band non-parabolicity and effective density states permits operation with a relatively low threshold current and improved spectral and dynamic properties.

Abstract: A three-stage sorption type cryogenic refrigeration system, each stage containing a fluid having a respectively different boiling point. Each stage includes a compressor in which a respective fluid is heated to be placed in a high pressure gaseous state. The compressor for that fluid which is heated to the highest temperature is enclosed by the other two compressors to permit heat to be transferred from the inner compressor to the surrounding compressors. The system may include two sets of compressors, each having the structure described above, with the interior compressors of the two sets coupled together to permit selective heat transfer therebetween, resulting in more efficient utilization of input power.

Abstract: Edge enhancement of an input image by four-wave mixing a first write beam with a second write beam in a photorefractive crystal, e.g., GaAs, achieved for VanderLugt optical correlation with an edge enhanced reference image by optimizing the power ratio of a second write beam to the first write beam, e.g., 70:1, and optimizing the power ratio of a read beam, which carries the reference image to the first write beam, e.g., 100:701. Liquid crystal TV panels are employed as spatial light modulators in order to change the input and reference images in real time.

Abstract: A redundant robot control scheme is provided for avoiding obstacles in a workspace during motion of an end effector along a preselected trajectory by stopping motion of the critical point on the robot closest to the obstacle when the distance therebetween is reduced to a predetermined sphere of influence surrounding the obstacle. Algorithms are provided for conveniently determining the critical point and critical distance.

Abstract: A method and apparatus for sensing wave flow across a surface wherein at least two pressure levels are sensed and combined to provide a representation of waves within the flow. In the preferred embodiment holes bored through the aircraft surface at an interval of one-half the wavelength of the flow being measured introduce pressure perturbations into a cavity so they may acoustically interfere. The interfering waveform is sensed by at least one microphone disposed in the cavity.

Abstract: A new approach to long-wave-infrared (LWIR) technology is based on molecular beam epitaxy (MBE) growth of holeimmobilized doping superlattices (12) in narrow band gap III-V semiconductors, specifically, InAs and InSb. Such superlattices are incorporated into detector structures (10, 10', 10") suitable for focal plane arrays. The objective of this approach is an LWIR detector possessing the advantages of high detectivity performance, to wavelengths of at least about 16 .mu.m, at operating temperatures of 65K, where long-duration space refrigeration is plausible.

Abstract: A basic single-chip building block for a RS decoder system is partitioned into a plurality of sections the first of which consists of a plurality of syndrome subcells each of which contains identical standard-basis finite-field multipliers that are programmable between 10-bit and 8-bit operation. A desired number of basic building blocks may be assembled to provide a RS decoder of any syndrome subcell size that is programmable between 10-bit and 8-bit operation.