USA As Represented by Secretary of the Navy

Myer Geller

Daniel E Altman

Glidden J Barstow

Richard H Patterson

George A Evanoff, Jr

Thomas E Keenan

An early warning system for detecting the UV from a missile plume has a wide field of view, large spectral bandwidth, solar blind detector. A coated detector passes only a spectral region that embraces UV signals of interest and a wavelength shifter includes a material that shifts the impinging UV energy into a spectrum that embraces the frequencies emitted by fluorescent photons. A photomultiplier tube responsive to the fluorescent emissions provides a responsive read-out indicative of an incoming missile.

Large spectral bandwidth, U.V. solar blind detector

A system enables omnidirectional non-line-of-sight simultaneous communicans in a number of frequency separated channels in the ultraviolet spectrum. A plurality of discharge lamps each has at least a single different isotope of mercury for each omnidirectionally radiating a discrete line in the ultraviolet spectrum. Each of the discrete lines in the ultraviolet spectrum is modulated by an on-off sequence generator so that modulated discrete lines transmit communications to a number of receivers randomly disposed in a non-line-of-sight relationship to the discharge lamps. Aborption filters at each receiver contain a quenching gas and all the other isotopes of mercury except the one which generated the modulated discrete line of interest. Photons from the other discrete lines in the ultraviolet spectrum which do not contain the information of interest are dissipated and quenched by the isotopes responsive to the radiation and the quenching gas, so that the modulated discrete line in the ultraviolet spectrum passes through the filter and to a photo-multiplier tube where the information provides representative output pulses for appropriate use. Simultaneous communications within the solar blind region are assured for non-line-of-sight transmitters and receivers within a limited range so that communications are not compromised.

Multi-channel, covert, non-line-of-sight UV communication

Mid-range communications are improved with a transmitter having an elongate omni-directionally radiating tube of UV energy that are focussed by a compound parabolic reflector to within a designated azimuth and/or elevation. The configuration of the reflector gives a broad beam directivity over a receiver target area to the exclusion of other bearings and elevations such that selected receiving stations can be designated between moving or unstable communication platforms, such as aircraft or ships. Because scattering occurs at angles larger than the direct beam, the requirement for accurate tracking mechanisms is further relaxed. Furthermore, these extra scattered photons increase the link distance. The need for very small divergence transmitters, like lasers, is eliminated permitting inexpensive, efficient UV lamps to be used with compound reflectors as transmitter sources.

Mid range UV communications

Detection of 253.7 nm radiation in the solar blind UV spectrum is enhanced y using an energy wavelength shifter with a photomultiplier tube which senses fluorescent emissions. A ruby block wavelength shifter has a coating that passes energy including the 253.7 nm radiation and a layer that passes radiation within a bandwidth including the fluorescent emissions. The ruby block absorbs the energy of the 253.7 nm radiation and produces fluorescent emission that passes through the layer. The photomultiplier tube is sensitive to the fluorescent wavelengths to aid in detection. The relatively large coated area provides a wide aperture, wide field of view detection of the 253.7 nm radiation.

Narrow spectral bandwidth, UV solar blind detector

An omnidirectional non-line-of-sight communication capability is assured by ransmission and reception in the 'solar blind' ultraviolet spectrum. An omnidirectional ultraviolet source generates a UV carrier in the tens of watts power range. This is modulated and received by having a sensitivity to respond to scattered UV modulated energy. Pulse modulating the ultraviolet spectrum signal and providing appropriate logic circuitry associated with the wide field-of-view receiver reduces the values of bit error rate.

Optical non-line-of-sight covert, secure high data communication system

An apparatus and method is described for separately measuring the optical tensities of the following: a sample beam having traversed a sample medium; a backscattered beam having been backscattered by the sample medium; a composite beam composed of the sample beam plus a reference beam having traversed a reference medium; and a second composite beam composed of the backscattered beam plus the reference beam. Measurements of these parameters is accomplished through the use of a linearly polarized source beam whose plane of polarization may be rotated between two orthogonal planes. The source beam is split into the sample and reference beams. The plane of polarization of the sample beam is caused to be rotated 90.degree. from the plane of polarization of the backscattered beam after interaction with the sample medium. The plane of polarization of the reference beam is selectively controlled between two orthogonal planes such that when combined with the sample beam and backscattered beam a polarization analyzer will allow passage of only those portions with a preselected plane of polarization for measurement and analysis of the light intensity. From the various measured intensities available the visibility or transmissivity of a sample medium may be determined. The sample medium may be isolated from the remainder of the transmissometer by a window which will allow unaltered transmission of the sample beam and the backscattered beam from the sample medium. With this configuration the invention may be utilized in an airborne manner, mounted on an airplane for the purpose of measuring transmissivity of atmospheric conditions in clouds.

Atmospheric transmissometer

An electronically controllable, wide angle of view, notch filter operates attenuate predeterminable narrow bandwidth wavelengths of light energy. An enclosure contains a selected material characterized by exhibiting strong quantum mechanical coupling between two determinable energy states of different levels above its ground energy state and also producing radiated emission within the desired narrow bandwidth wavelengths when externally excited to populate the upper of the two determinable energy states. Transparent windows at opposite ends complete the enclosure which is maintained at a desired temperature to vaporize the selected material. Two electrodes, oppositely positioned within the enclosure contiguous to its optical path, are connectable to a source of pulsed electrical energy to generate an electric discharge across the electrodes of sufficient strength to raise the vaporized selected material from its ground energy state to the lower of the two determinable higher energy states, causing selective absorption of predetermined narrow bandwidth wavelengths of light energy under the timed control of electrical actuation.

Electrically controllable wide angle of view optical notch filter

A high intensity source produces light energy output principally in the 3A to 4300A spectral region. An envelope of material substantially transparent to light energy within the desired spectral region is sealed to contain xenon gas in an amount sufficient to produce at least one atmosphere of pressure in its unheated state and also mercury in an amount sufficient to develop a vapor pressure of not less than one atmosphere when the envelope is heated to an operative temperature. Electrically conductive electrodes communicate with the interior of the sealed envelope forming a gap therebetween which becomes a conductive arc upon connection of external terminals of the electrodes to a source of pulsed electrical power. The sealed envelope and its contents are maintained at an operative temperature of the order of not less than approximately 500.degree. C, ensuring the vapor pressures required to produce the high intensity output within the desired spectral region.

Pulsed laser excitation source

An improved metal vapor laser tube is comprised of an enclosure, preferably n an elongate tubular form, containing an amount of a metallic element. The material of the enclosure is selecteed to be electrically non-conductive and also for its ability to withstand elevated temperatures of the order of 1000.degree. C. The enclosure has at least one window capable of transmitting energy at the wavelength of emission of the metallic element contained within it. Two electrodes, preferably in the form of cylinders, are disposed at opposite ends within the enclosure in coaxial alignment with the major axis of the enclosure. An extension from the major axis of the enclosure is disposed proximate to each electrode and an electrical conductor connected to each electrode is sealed within substantially the entire length of each extension. Each electrical conductor is characterized as being of a strip configuration and having a substantially elongate elliptical cross-section. A method of sealing the metallic conductor strip within a substantially tubular extension member comprises the steps of positioning the metallic strip within the hollow of the tubular member, then inserting a semi-cylindrical piece of fusible material into the hollow portion of the tubular member on each side of the metallic conductor strip, and finally simultaneously fusing the fusible material to both the metallic strip and the tubular member to form a unitary extension assembly.

Growing community of inventors

San Diego, CA, United States of America

Myer Geller