Abstract: A method of marking and identifying an object (10) by the marking consists of applying to an object (10) an up-conversion material (12), then irradiating the object (10) with infrared electromagnetic radiation (16) and, finally, observing the irradiated object to detect the spectrum of emitted electromagnetic radiation (18). A suitable up-conversion material (12) is selected from a group of up-conversion materials consisting of CaF2, BaF2, CdF2, LaF2 and SrF2 doped with erbium, praseodymium, neodymium or dysprosium. The objects (10) may be observed to detect emitted electromagnetic radiation (18) from that part of the electromagnetic spectrum that is visible to the naked eye. The objects (10) may also be observed to detect specific wavelengths of electromagnetic radiation which are known to be emitted by the up-conversion material (12) when the up-conversion material (12) is irradiated by designated wavelengths of infrared electromagnetic radiation.

Abstract: A fiber optic interferometric sensor (150) having constantly high sensitivity by use of two lasers (152, 154) that simultaneously output at first and second wavelengths. By judicious choice of the wavelengths, the optical path length difference between the two interferometer paths (164, 166) can be kept near the maximum slope of the interference fringes for one or the other of the wavelengths. The output from the interferometer (160) is divided between first and second detector arms (170, 130). A filter (172) in the first detector arm passes the first wavelength and rejects the second. A filter (182) in the second detector arm passes the second wavelength and rejects the first. A first detector (174) at the output of the first detector arm reads the interference pattern at the first wavelength. A second detector arm reads the interference pattern at the second wavelength.

Abstract: A visual display and helmet assembly is configured to function in the presence of a harsh environment, e.g., high wind, vibration and shock and strong ambient light. The visual display preferably includes a transmissive liquid-crystal display to reduce the display's size and to enhance the intensity of a virtual image. In addition, the display is preferably reconfigurable so that different display indicia can be programmed as desired. To reduce probability of injury to a user, the visual display is carried on the exterior of the helmet with its center of mass positioned substantially on the midsagittal plane of the user. In addition, a mount permits the visual display to detach from the helmet when it is subjected to forces above a predetermined threshold. The mount is also permits yielding movement between the visual display and the helmet to enhance viewing of the image.

Abstract: A measurement optical fiber is placed into contact with a geological structure, and a reference optical fiber of about the same length is not contacted to the geological structure. An input beam of light is transmitted down the lengths of the measurement and reference optical fibers, and the interference fringes formed between the reflected beams in the two optical fibers are counted to determine the geological displacement, and thence the geologic strain, experienced by the measurement optical fiber. Preferably, multiple pairs of the measurement and reference optical fibers are used, the optical fibers of the various pairs being of different lengths. The difference in displacement measured by any two pairs is a measure of the geological strain in the region between the ends of the two pairs. The multiple pairs are conveniently provided in two optical fiber cables, a measurement cable which contacts the geological structure and a reference cable which extends parallel and adjacent to the measurement cable.

Abstract: The image source of a head up display for a motor vehicle is illuminated from a remote high intensity source using fiber optics. The HUD image source and optics are under the dash pad of the vehicle and include color LCD or color filtered image source. The image is lighted by a high intensity light source which yields a bright projected image and which generates substantial heat. The light source includes lamps in a fan-cooled heat sink located in the vehicle engine compartment, for example, and coupled to the image source by fiber optic light guides. The light guides abut the image source to uniformly light small image patterns commensurate with the light guide size, or light spreading techniques are used for larger image patterns.

Abstract: An improved image transmission system which includes an elongate optical waveguide 15 having an input aperture 17 and an output aperture 19. Optical apparatus 11, 13 is provided for injecting a transform of an image into the waveguide. In a specific implementation, the Fourier transform of the image is injected at the input aperture 17. The output image is transformed as well to provide the desired image. When the Fourier components of the image are transmitted, each component propagates at a different velocity. However, the magnitude of the components are preserved and used to reconstruct the image at the output of the waveguide. This allows for the transmission of optical images without digitization with a single, inexpensive waveguide.

Abstract: A system for optically generating expansion coefficients for an image processing function. The invention (10) includes a first optical element (18) for providing a transform of an image provided at a first image plane (16). A second optical arrangement (20) provides a product of the transform of the image and a transform of a convolving function. This product is transformed by a lens (22) to provide an image intensity distribution representative of expansion coefficients resulting from a convolution of the image by the convolving function. In a specific implementation, the convolving function is a wavelet and the intensity distribution is detected to provide the expansion coefficients.

Abstract: An improved wide-spectrum test target assembly, with visual and near IR (infrared) targets integrated with a long wavelength emissivity target. A single relatively thick optical fiber (78) is used to receive target signals emitting from several thinner fibers (72, 74, 76), each carrying a signal of different wavelength. The integrated signal is then relayed to an aperture (108) of an emissivity target through a gradient index lens (88) to further combine with the long wavelength target signal emitted from the emissivity target assembly (100). By selecting appropriate numerical apertures and diameters of the fibers, relatively high power output is achieved. A light collimator (200) is also disclosed for collimating light generated by the test target assembly to simulate targets at infinity.

Abstract: Selective emissivity coatings are disclosed for temperature reduction of enclosures such as vehicles and building structures. The coating includes a selective emissivity material such as silicon-oxy-nitride having a desired thermal emissivity function which is high in the 8-13 micron wavelength region, and low elsewhere except in the visible wavelength region. The material provides a mechanism for radiative cooling of the enclosure by converting the blackbody radiation of the enclosure, which would be reflected by the earth's atmosphere, into far infrared radiation which is transmitted by the atmosphere. According to another aspect of the invention, the coating further comprises a semimetal which is reflective of radiation in the near infrared region, thereby reducing the solar heat load on the enclosure. One suitable semimetal is LaB.sub.6. The coating may be applied to the exterior surface of vehicle and building windows, or to the exterior, non-window surfaces of building structures.

Abstract: A sensitive towed optical fiber sensor array 50, wherein the fiber sensors (60A-60N) are connected in parallel, and the optical fiber cable (34) is paid out from the towing ship at a velocity about equal to but opposite to the velocity of the towing ship. The fiber sensors (60A-60N) are immune to electromagnetic interference, and the output of the sensors can be isolated readily to the parallel hookup of the sensors. Turbulence and acceleration noise is greatly reduced due to the manner in which the fiber cable (34) is paid out, and crosstalk between sensors is eliminated.

Abstract: An improved target for testing and calibrating a detection device. The target (10) includes a metal substrate (12) with a first layer (14) of high emissivity material and a second layer (16) of low emissivity material are deposited thereon. In the specific implementation, the substrate (12) is copper, the first layer (14) is chromium-oxide and the second layer (16) is chrome. In the illustrative embodiment, an aperture (22) is drilled through the substrate (12) and the first and second layers (14, 16) thereon. An infrared emitter (20) is located at the aperture (22) to provide point source radiation. A conventional heater (26) is applied to the back surface of the target. A pattern is etched on second layer (16) on the front surface of the target using electron beam lithography. The use of a metal substrate (12) allows for the drilling of small holes more easily than in the conventional target.

Abstract: An optical fiber evanescent wave fuel sensor, employing a light source with a wavelength selected to be at the strong infrared absorption lines of the fuel, typically hydrocarbons. The amount of light leaking from the optical fiber is an exponential function of the length of the fiber in the liquid, and is independent of the relative indices of refraction of the fuel and fiber cladding material.

Abstract: A nondestructive method and apparatus is disclosed for determining the thickness and composition of a zinc phosphate layer applied to a metal surface, such as sheet metal on an automotive assembly line. The phosphate layer is irradiated with infrared light which is at least partially transmitted through the phosphate layer. Reflections from the upper and lower surfaces of the phosphate layer return a total reflected intensity which is a function of the optical parameters of the phosphate components and the ratio of the components corresponding to the optical parameters. In the event, for example, that a phosphate layer includes two zinc phosphate components, the measure of reflected intensity at two separate wavelengths will be different inasmuch as the optical properties of the zinc phosphate components is also a function of frequency.

Abstract: An inexpensive, broadband technique for testing laser rangefinder systems. The invention includes a mechanism (18) for detecting an emission of a pulse of electromagnetic energy by a laser rangefinder under test (12) and providing a first signal in response thereto. In response to the first signal, a second signal is generated (20) with a predetermined delay on detection of the pulse from the laser rangefinder (12). The second signal is used to trigger a radiation source (16) which generates an output signal. This output signal simulates a return signal, the reflection of the pulse from a hypothetical target back to the laser rangefinding system.

Abstract: A low cost visual simulation system (100) for training simulators is disclosed. Aerial photo transparencies are used directly as image sources without creating a digital data base. The approximately correct image perspective is generated optically by a deformable mirror (114) and a zoom lens and rotation prism assembly (106). Stereo image photo pairs (120) need to be analyzed only at a relatively small number of points; thus, the computational burden is greatly reduced.

Abstract: An adaptive electroopical lens system for use in optical data storage systems, optical phased arrays, laser or other optical projectors, and raster scanning devices, and the like. The invention provides an electrooptical means for scanning an optical beam or moving an optical storage or retrieval point. Beam movement is achieved electrooptically, by changing the index of refraction of an electrooptical material by controlling electric fields applied thereto. A plurality of electrodes are disposed on one surface of the electrooptic material and a ground electrode is disposed on the other. The electrodes are adapted to apply electric fields derived from a voltage source to the electroopic material that selectively change its index of refraction and provides for a predetermined index of refraction profile along at least one dimension thereof, thus forming a lens. By appropriately forming the electrode pattern and properly controlling the voltages applied thereto, differing lens shapes may be formed.

Abstract: Human aesthetic evaluation of a finished painted surface, such as an automotive body, is automatically simulated by analyzing a distorted reflected test pattern from the finished surface. Fourier power spectra of the distorted test pattern are generated to form a parameterization of the reflected distorted test pattern. A correlation is statistically made to reference Fourier power spectra, each of which has been associated with a specific human aesthetic evaluation, such as wetness, dullness, softness, brightness, and the like. The Fourier power spectra of the distorted reflected image are automatically generated through a digitized two dimensional pixel map, which are mapped into functions of the edge direction and edge intensity of the pixels. The functions are then Fourier transformed into Fourier power spectra and correlated with reference reflected patterns.

Abstract: An analog optical processor for performing affine transformations and constructing fractal objects. An optical processor for optically performing an iterated affine transformation includes a rotating prism, an imaging lens and a translatable mirror, together with a pulsed laser as an input light source and an image detector array to record the final transformed image. The amount of rotation is determined by the setting of the rotating prism. The imaging lens provides the required magnification or demagnification. The translating mirror is shifted to provide the necessary translation. The pulsed image passes through the optical loop many times to perform the transformation. An optical Iterated Function System is implemented by connecting a plurality of the optical loops in parallel, together with shutters or beamsplitters for guiding the pulsed image to different loops according to the probabilities assigned by the Iterated Function System.

Abstract: A display system is disclosed which employs multiple holographic elements for selectively reflecting images from separate projectors to one or more distinct viewing volumes. The display system provides the capability to project differing perspective images to individual crew members located at separated positions within a training simulator.

Abstract: An electro-optical system that implements the self-tiling process of fining proper Iterated Function Systems for modeling natural objects. The system can operate in two different modes, a real-time interactive mode and an automated mode. The purpose of the system is to speed up the process of finding a proper IFS for a given object to be modeled. The system makes use of optical processing, including optical means for rotating, magnifying/demagnifying and translating an input image. Optical beamsplitters are used to combine transformed images to produce a tiled output image. In one embodiment, an automated controller evaluates the goodness of the match between the tiled image and the input image and generates control signals which cause adjustment of the settings of the optical means. The process is repeated automatically until the match is sufficiently good. The invention can also be operated in a manual, man-in-the-loop mode.