Abstract: In a method of detecting ice on surfaces of an aircraft, a surface of an aircraft is scanned with laser light operating at different wavelength regions in a manner whereby the surface scatters the laser light. Laser light scattered from the surface is detected. Radiation outside the wavelength bands of interest is removed prior to detection. The detected, filtered, scattered laser light is processed to reconstruct images of the surface, thereby indicating areas of ice and water on the surface. The processing takes into account the directions of scanned continuous wattage laser beams relative to the surface, laser beam geometry factors due to changing distance between the laser beams and the surface while scanning, relative signal levels, normalizations and returns from other detectors. The material of the windows of the aircraft blocks the laser beam and any stray laser light. Also, the windows of the aircraft could be treated to block the laser beam and the laser light.

Abstract: A method and system for searching for a given sequence in a data base having a multitude of reference sequences stored or identified therein. In accordance with this method, a light beam is modulated with patterns representing the reference sequences, and with a pattern representing the given sequence, and a correlation signal is generated representing the correlation of the reference and given sequences.Optical diffraction patterns may be used to represent the given and reference sequences. In one embodiment, a multitude of first diffraction patterns, each one representing the given sequence, are formed in an optical medium, and a light beam is modulated with each of those multitude of diffraction patterns to form a multi-channel signal beam. Each channel of that beam is then modulated with a respective one second diffraction pattern representing one of the reference sequences to form a multi-channel correlation beam.

Abstract: Denticulated strips receive orthogonally disposed panels to form rectangular or cube enclosures of desired sizes. They are quickly assembled utilizing push pins. The panels are designed to have overlapping edges so that they minimize light/air leakage--making them particularly adaptable as optic baffles.

Abstract: A system and method of optical correlation that avoids bias level terms in the optical correlation output. In the system and method, two coherent polarized component beams having frequencies f.sub.1 and f.sub.2 are derived from a light source. Portions of these component beams are converted to a reference electrical signal having a frequency .DELTA.f=f.sub.2 -f.sub.1. The sum f.sub.1 +f.sub.2 of the component beams is correlated under the control of a multiple of the reference electrical signal. The Fourier transform of the amplitude of the correlated light is projected and detected on a detection plane.

Abstract: A plurality of fiber optic laser members are supported in an apertured plate so as to form an array supplied by an optical pump. Individual members may have the light passing there through modulated by respective modulators. Light from the fiber optic laser array illuminates an optical storage medium which stores information. The resulting output undergoes Fourier transformation and optical filtering. Filtered light then undergoes inverse Fourier transformation and detection.

Abstract: A fixture comprising three plates capable of exercising decoupled motion along three angular axes. A first end of a connecting rod is mounted, by way of a spherical bearing in one of the plates, while an opposite end is secured to the peripheral center of a spherical sector platform. The periphery of the platform is supported on bearings mounted to a rotatable gear which imparts yaw motion to the spherical section. Displacement of the connecting rod causes tilting of the spherical section in roll and pitch directions. Three linear and three rotational degrees of freedom are possible for the platform while maintaining a constant pivot point at the center of the sector's radius of curvature, on the system axis. The pivot point lies above the unobstructed mounting surface of this fixture.

Abstract: Holographic optical elements are utilized for discriminating between monochromatic, coherent radiation and broadband, noncoherent radiation in passive coherent radiation detection systems such as aircraft warning systems and submarine laser communication systems. Coherent laser light can possess an extremely high energy density, directivity, (i.e., collimation), and a very narrow wavelength band when compared to natural or man-made, broadband white light sources. The concentration of laser light energy by a holographic optical element at the detector stage is a consequence of its special characteristics. Moreover, equally important, the diffracted light distribution in the neighborhood of the detector possesses a unique, bright geometric pattern not readily obtained with noncoherent sources. This geometric pattern is used as a laser wavelength detector for determination of the incident angular direction of the laser beam, as well as a coherent/noncoherent light discriminator.

Abstract: A viewing window is equipped with a selective attenuator for a harmful incoming laser beam. The attenuator principally employs a holographic optical element which selectively deflects the laser beam where it may be absorbed or further deflected. Ordinary light passes undeflected so that it may be processed by optical equipment or a viewer.

Abstract: A neural network processing element uses primarily optical components to model a biological neuron having both spatial and temporal dependence. The neural network processing element includes a switch-controlled laser source, a multiple holographic lens, a spatial/temporal light modulator, and a photodetector array. Laser beam control may be optical, electrical or acoustical, or a combination of these.

Abstract: An image enhanced optical correlator system providing for optical preprocessing of an input image prior to processing thereof in an optical correlator. The optical preprocessing is provided to enhance the image and/or image related characteristics such that the probability of detection of prescribed targets therein in the optical correlator is increased. In the system, an input image beam is split into orthogonally polarized image inputs, processed to enhance targets therein, and then the algebraic result (addition and/or subtraction) thereof is processed through an optical correlator. Techniques are used in the feedback systems to enhance the output plane correlation signal detection by an adjustment in phase, spatial frequency filtering and/or threshold setting optimization.

Abstract: This invention enables a laser beam, expanding from a pinhole aperture spatial filter, to be brought back on the optical axis of an optical system such as an optical correlator system and maintained there. The principle of operation is that photodetectors spaced in the outer region of the expanding beam detect a change in orientation of the incident laser beam, and the change is measured and an error signal is used to drive electrically controlled micrometers so as to restore and maintain alignment.

Abstract: A system and method is presented for obtaining optical phase and amplitude measurements utilizing an acousto-optical modulator for modulating a laser light beam with a multifrequency electrical signal to form an image that is Fourier transformed and spatially distributed proportional to the frequency components of the electrical signal. An optical component such as a spatial light modulator is located in the Fourier plane and the modulated image is inversely transformed and optically heterodyned to produce a transformed image. The transformed image impinges a photodetector that produces an electrical output signal that is inputted to a network analyzer to measure phase and amplitude of the transformed image. The electrical output signal is compared with a reference signal and deviations from the reference signal provide a quantitative measurement of the phase and amplitude response of the spatial light modulator.

Abstract: Method of fabricating a coherently exposed multiple holographic lens including a first step of fabricating an incoherently exposed master multiple holographic lens with an array of overlapping holographic lens elements, each of said lens elements having an interference pattern substantially covering the entire area of the lens. The master multiple holographic lens is illuminated with a first beam of light from a coherent source to provide a plurality of light waves equal in number to the number of lens elements in the master lens. The plurality of light waves overlap in a region downstream of the master lens. A holographic recording medium is positioned in the region of overlap such that an area thereon is illuminated simultaneously by each of the plurality of light waves. A second beam of light from a coherent source is directed toward the area of the holographic recording medium illuminated by the plurality of light waves.

Abstract: Prior art optical image correlators are extremely cumbersome and do not use spatial light modulators. To determine whether an of-interest target is within a scene, the present invention optical correlator uses a laser diode, a spatial light modulator, a holographic lens array, a matched filter array and an inverse transform lens. In particular, the laser diode generates a coherent laser beam, which is expanded and collimated. Information of the of-interest target is encoded thereon by the spatial light modulator. The encoded laser beam is then directed to the holographic lens array, which replicates from the single laser beam a plurality of similar beams. These beams are focused onto a matched filter array having multiple matched filters, the number of which corresponds to the number of incoming beams.

Abstract: An alignment fixture for an optical instrument such as an optical correlator providing for the adjustment of the alignment of an element thereof, such as a matched filter or multiple matched filter or a multiple holographic lens, along at least two transverse x and y axes, and also rotationally .theta. in roll about a z axis perpendicular to the transverse x and y axes. The alignment fixture is constructed with a base plate which is designed to be mounted on a stabilized optical bench. The base plate is movable along the z axis for adjustment therealong, and includes a vertically extending frame member. An L-shaped lift angle plate is vertically movably and supported by the vertically extending frame member to provide for alignment adjustments along the y axis. The L-shaped lift angle plate movably mounts a rotational stage in a manner which provides for alignment adjustments along the horizontal x axis.

Abstract: An optical correlator system, comprising a laser to generate a signal beam, an image means located in the path of the signal beam to spatially modulate the signal beam, and first and second matched filters. A multiple beam generating holographic lens is located in the path of the modulated signal beam to partially transmit the signal beam and to deflect a first matrix of replicas of the signal beam onto the first matched filter. A mirror is located in the path of the partially transmitted signal beam to reflect that transmitted beam back to the holographic lens, which deflects a second matrix of replicas of the signal beam onto the second matched filter. With an alternate embodiment, a series of holographic lenses and beam splitters are alternatively arranged along the path of the signal beam. Each holographic lens generates two matrices of beams, with each matrix of beams being focused on an associated matched filter.

Abstract: Reference patterns are disclosed which are designed particularly for the functions of evaluation and alignment of an optical instrument, such as a spectrum analyzer or an optical correlator employing a matched filter array as its memory. A preferred embodiment of the reference input pattern is binary and of simple geometry such that it can be easily fabricated and the Fourier transform and autocorrelation functions can be easily calculated. Two-dimensional spectral features and autocorrelation patterns for one particular input function have been derived in closed form and numerically evaluated. The Figures herein illustrate the symmetries in the multi-peaked distributions. Tables of relative intensities are disclosed and are useful in evaluating and comparing the performance of different coherent optical processing systems.

Abstract: An optical system for an in-line holographic lens or lens array which is designed to produce and pass a symmetrical focused beam of light while or blocking or attenuating the zero order in-line collimated beam illuminating and passed by the lens. Each holographic lens is designed to produce a symmetrical focused beam of light, and has particular applicability to high quality, low f-number holographic lenses. In the optical system, the in-line holographic lens is illuminated by a reconstruction beam of light such that it produces a focused beam of light along the optical axis of the lens, and also passes the zero order in-line reconstruction beam. A polarization rotator is positioned along the optical axis to receive the focused beam of light and also the zero order reconstruction beam, with the focused beam of light being incident thereon and traversing through the polarization rotator at different angles from the zero order reconstruction beam.

Abstract: A variable area recording geometry is formed over the surface of a photosensitive material by scanning and exposing with an optical writing beam. The width of this area is determined by input signals to be processed. The exposed photorefractive medium results in a phase modulation of an optical beam traversing the medium in a direction parallel to the surface as in an integrated optical waveguide.

Abstract: A hybrid opto-electronic method and apparatus for Fourier transform measurements of temporal signals are disclosed.The magnitude and phase of the signal transform are system outputs. High resolution spectral analysis operation is accomplished by proper spatial phase corrections, equivalent to aperture synthesis. Configurations for one-dimensional and two-dimensional input data formats are described. The disclosed method and apparatus can process signals with continuous spectral content as well as narrow spectral lines.