Abstract: An optical system for determining if a target object is an object of a first kind, including means for illuminating the target object along an incident path with coherent light of a selected nature means, for retro-reflecting coherent light from an object of a first kind, means for detecting the nature of light reflected from at least a portion of the target object, means for comparing the nature of the detected light to the selected nature, and means for indicating that said target object is an object of a first kind if the nature of said detected light is the same as the selected nature. Alternative embodiments include encoding interrogating and retro-reflected light signals at both the interrogating station and target stations, and the use of a verification signal directed at the target object prior to illumination of the target object with an interrogating beam.

Abstract: A secure identification system for identifying a potential target in a battlefield environment as being either a friend or a foe is disclosed. An interrogator produces two interrogation pulses, such as laser flashes, aimed at the target and separated from each other by a randomly determined period of time. The target detects the two interrogation pulses, measures elapsed time between the two pulses, and prepares a reply signal for transmission which is controlled by the elapsed time. Frequency, pulse width, and transmission delay parameters are each controlled in a substantially random, but predetermined manner in response to the elapsed time. The interrogator has a receiver and qualifier which receive reply signals and define expected values for the controlled parameters. An indication is provided concerning whether the target represents a friend or a foe based on received reply signals at the interrogator.

Abstract: A position sensing apparatus and method useful for surveying, marking, and grading implement sensing and control is disclosed. The position sensing apparatus includes two laser reference stations, each of which projects a laser beam that periodically sweeps in a plane across the area to be surveyed. Each time a laser beam strikes the opposite reference station, a radio timing signal is broadcast by that reference station. The position sensing apparatus also includes a portable sensing station that comprises a laser beam receiver, a radio reciever, and a programmed computer. The planar position of the portable sensing station relative to the reference stations is computed by a triangulation technique based on the relative timing of detection of the laser beams by the laser beam receiver and the reception of the radio timing signals by the radio receiver. Elevation is determined according to the height at which one of the laser beams strikes the laser beam receiver.

Abstract: A rf decoy for use with rf repeater devices, transponders, noise jammers and other jamming devices. The decoy is adapted to be towed behind an aircraft using a tow line which incorporates a fiber optic link through which signals are transmitted. The device is excited through rf energy which is modulated on a laser carrier and transmitted through the fiber optic link. While the principal application is to repeaters which are towed behind an aircraft, the invention has utility in free-falling and forward fired transmitters as well as land and sea based vehicles.

Abstract: An aircraft collision warning system in which a low power pulsed laser sym projects narrow bandwidth radiation into 4.pi. steradians around an aircraft and a matched, narrow bandwidth receiver system, with a 4.pi. steradian field-of-view which detects such radiation emitted from another aircraft within range of the receiver and activates appropriate warning.

Abstract: A 3 or more - dimensional optical processor for simultaneously processing ree or more parameters from a coherent emitter via an acoustic Bragg cell. For a 3-D processor, two separate antenna arrays (azimuth and elevation) are connected to excite two sets of acoustic transducer arrays on one edge of the Bragg cell. Multiplexing is achieved by the appropriate choice of the transducer array apertures. One transducer array set may have a narrow aperture to produce one wide first grating lobe pattern or a fraction thereof in a given focal plane (nonredundant imaging). The other transducer array set may have a wider transducer array aperture to produce a plurality of smaller second grating lobes within the first grating lobe pattern in the focal plane (redundant imaging). One coordinate axis of the focal plane represents the frequency of the emitter.

Abstract: A "passive interrogator label system" (PILS) comprises an interrogator for transmitting an interrogation signal, one or more "labels" or passive transponders which produce a reply signal containing coded information in response to the interrogation signal, and a receiver and decoder for receiving the reply signal and decoding the information contained in it. The frequency of the interrogation signal assumes a plurality of frequency values within a prescribed frequency range. The decoder includes a mixer (four quadrant multiplier) for mixing together the interrogation and reply signals (or signals derived therefrom) to produce a mixed signal containing frequencies which are the sum and difference of the frequencies of the interrogation and reply signals. A signal processor, responsive to this mixed signal, detects the amplitude and phase of at least some of the frequencies contained in the mixed signal and thereby determines the informational code associated with the transponder.