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: Means and methods are provided for determining the energy content of a hydrocarbon fuel by infrared spectroscopy. The relationship between the energy content of the fuel and the number of carbon-carbon and carbon-hydrogen bonds in the fuel is disclosed. This relationship is utilized to determine the energy content of the hydrocarbon fuel by measuring the concentration of such carbon-carbon and carbon-hydrocarbon bonds by infrared spectroscopy. A first embodiment irradiates a hydrocarbon fuel with infrared radiation of wavelengths at which specific carbon-carbon and carbon-hydrogen bonds strongly absorb. A detector array and microprocessor process the data to compute the energy content of the fuel or rate of energy consumption by a device using the fuel. A second embodiment exposes the hydrocarbon fuel to infrared energy by using frustrated total internal reflection.

Abstract: Apparatus for determining the density of fluids in containers utilizing an x-ray source and two radiation detectors located at different distances from the source by a known amount. The outputs of the detectors are ratioed to produce a signal which varies with the density of the fluid lying between the source and the two detectors.