USA As Represented by Secretary of the Navy

William E Richards

Henry F Taylor

John A Trias

Paul S Catano

The detection and localization of an antiship torpedo is accomplished by ustic and optical means. A ship's sonar determines the approximate location of the incoming torpedo and a laser scans this location with energy in the blue-green spectrum. Surface reflections are gated out of a linear detector array and reflected portions of the scanning beam which penetrate the water's surface are divided among the elements of the linear detector array into field of view element signals. These field of view element signals are subsequently compared in time and amplitude to determined disparities between them which point to the torpedo's position, depth and bearing. Optionally, spectral and polarizing filters are provided to enhance the signal to noise ratios and to facilitate signal processing.

Antiship torpedo defense system

An electro-optical modulator/antenna operates in the tunable diffraction ting mode to vary the magnitude of the zero diffraction order and consequently transmits optical information. A relatively thin slab of lithium niobate or equivalent electro-optic material has its lateral surfaces optically polished and its C-axis, or optical axis, running parallel to the polished lateral surfaces. At least one set of interdigital metallic electrodes are deposited on the face or just within the lateral surfaces to form, among other things, a diffraction grating that is orthogonally disposed with respect to the C-axis. When a potential source is coupled to the interdigital electrodes, the electric fields between adjacent electrodes change the crystal's index of refraction in accordance with the linear transverse Pockel's effect. The thin crystal having the electrodes substantially covering at least one of its lateral surfaces, thusly presents a large aperture modulator/antenna capable of modulating incident optical energy over a wide angle of incidence, for example, up to plus and minus 45 degrees. Because of the thinness of the crystal, transmissivity is good and losses are reduced. The cooperation between the diffraction grating phenomenon and the Pockel's effect greatly reduces if not totally eliminates the possibility of arcing between adjacent electrodes as the zero diffraction order is modulated since the potentials creating the modulating electric fields between adjacent interdigital electrodes are greatly reduced in this mode of operation.

Large aperture phased element modulator/antenna

An all-weather, maximum resolution system visually presents a multi-color mposite image of plural selected spectral ranges of energy received from a common field of view. First, second, and third images of a selected common field of view are developed and respective, first, second and third sensors (each responsive to a different spectral range of energy) develop first, second, and third sets of electrical signals commensurate with the energy emanating from the selected common field of view. In a typical preferred embodiment the selected spectral ranges may comprise the visual range of light energy, the middle infrared range comprising light energy in the 3 to 5 micron region, and the far infrared range comprising light energy in the 8 to 10 micron region. A multi-color cathode ray tube receives the three different sets of electrical signals thus developed and produces a multi-color composite image in three different primary colors representing the common field of view in the three discrete selected spectral ranges of energy which emanate from it. All-weather detection of objects within a field of view is then enabled such as during clear visibility, fog conditions, and rain conditions, in both daytime and nightime.

All-weather multi-spectral imaging system

A wide angle narrowband optical filter is provided by an assembly in which a body member supports multiple absorption materials in a common optical path. Each of the multiple absorption materials contributes toward narrowing the spectral bandwidth region permitting transmittance of light energy. A bandpass glass color filter restricts light transmission to a relatively broad spectral range of approximately 250 nanometers and a selected coumarin dye material in solution used with a second solution of a selected rare earth material narrows the spectral range of transmittance. In a preferred embodiment an interference filter further narrows the transmitting bandwidth to approximately 12.5 nanometers at FWHM (measured at Full Width Half Maximum) in the spectral region which is desirably coincident with the wavelengths of light energy best transmitted in ocean waters.

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El Cajon, CA, United States of America

William E Richards