US Government As Represented by the Secretary of the Army

The United States of America As Represented by the Administrator of the

United States of America As Represented by the Administrator of Nasa

The University of Alabama

Don A Gregory

James C Kirsch

Amy Sue Kransteuber

Valentin Korman

John L Johnson

Travis S Taylor

Peter S Erbach

Joseph G Duthie

Bob D Guenther

Kevin W Pedersen

Charles D Stocks

David J Lanteigne

Seyed Sadreddin Mirshafieyan

John T Wiley

James A Harrington

Laura L Huckabee

Joseph J Booth

Scottie B Mobley

An electrically-tunable optical filter has an optical cavity that forms an absorption peak in light that is incident on the filter. The optical cavity includes a layer composed of a material with a high electro-optic coefficient so that the index of refraction of the layer changes in response to a voltage applied by a controller. By adjusting the voltage, the controller can control the index of refraction so that an absorption peak of the filter can be tuned as may be desired without having to alter the physical structure of the filter.

Electrically-tunable optical filters and methods

A method and apparatus are provided for sensing the mass flow rate of a fluid flowing through a pipe. A light beam containing plural individual wavelengths is projected from one side of the pipe across the width of the pipe so as to pass through the fluid under test. Fiber optic couplers located at least two positions on the opposite side of the pipe are used to detect the light beam. A determination is then made of the relative strengths of the light beam for each wavelength at the at least two positions and based at least in part on these relative strengths, the mass flow rate of the fluid is determined.

Fiber optic liquid mass flow sensor and method

A Real-Time Optical Correlating System produces holograms that contain both amplitude and phase information and have none of the time constraints of the traditional holographic methods. It has been demonstrated to operate at television field rates (60 Hz) employing currently available devices of moderate resolution. Using the System, the holographic matched filter of an input scene is calculated optically as an analog sum, captured by a charge-coupled device (CCD) camera and transmitted directly or through a computer to and displayed on a commercially available liquid crystal display (LCD) device. The correlation plane may be viewed immediately on a suitable screen because there is no film to process or computer calculations to be performed. Concurrently with the creation of the holographic matched filter of the input scene, a Fourier transform of a test scene is produced and both are imaged on another charge-coupled device camera for any correlation between the input and test scenes.

Real-time optical correlating system

A method is disclosed by which filters are created optically in real time&mdash;and tested. This technique is made possible by recent advances in Charge Couple Detector (CCD) detector array technology. Pixel (picture element) size has decreased to the point that real fringes can be detected and displayed. The fringes result from the interference of the optical Fourier transform of a displayed scene with a specified plane wave. Phase information is thus preserved. This is the critical information required in producing a hologram or a holographic matched filter.

Real-time analog creation of holographic fourier transform matched filters

The off-axis joint transform correlator improves on the extant on-axis jo transform correlator by eliminating the requirement for a second laser frequency and the means for blocking the first laser frequency from propagating beyond a given point in the correlator. These eliminations are accomplished by using a beamsplitter and a mirror to bring a second portion of the first frequency at an angle to read the pattern information written onto a spatial light modulator by the first portion.

Off-axis joint tranform correlator

The fiber optic-based correlating and sensing system (the System) utilizes length of optical fiber through which the object beam travels prior to being incident on the holographic plate. First, a matched filter is created on the holographic plate of the initial condition of the environment. Then when the plate is re-placed in its original position in the System and the reference beam is blocked from reaching the plate, a correlation peak appears as the object beam passes through the holographic plate. To use the System as a correlator, the object beam is transmitted through an input scene prior to its travel through the optical fiber. The changes in the input scene from the initial scene causes broadening of the shape of and degradation of intensity of the correlation peak. To use the System as a sensor, the object beam travels through the optical fiber acquiring information regarding the environment surrounding the fiber, such as pressure, temperature, sound, electric and magnetic fields. Again, the changes in the environment are indicated by the broadening shape and decreased intensity level of the correlation peak.

Fiber optic-based correlating and sensing system

The mirror elements mirror device spatial light modulator are selectively deflected. Such deflection causes incident infrared radiation to be reflected in selected directions. The number of deflected mirror elements as well as the degree of deflection determines the amount of reflected radiation which travels through an aperture and is collimated by suitable imaging optics, thus creating an infrared image that appears to be at infinity.

Infrared image projector utilizing a deformable mirror device spatial

An optical correlator system for encoding a complex optical image onto a erent beam of light such as a laser and comparing it with a reference complex image. One embodiment of the invention encodes phase only information of the complex image onto the coherent beam of light by means of a liquid crystal television receiver. The light beam is passed through the liquid crystal television receiver, whose pixels are manipulated to provide phase information concerning the image. A second embodiment of the invention encodes both phase and amplitude components of a complex image onto the coherent beam of light such as a laser beam. Either or both encodings are utilized in the optical correlator system.

Optical encoding and correlation system

Incoherent optical processing techniques are shown which demonstrate image intensity normalization and contour enhancement. A new type of incoherent optical correlator which combines a model of the human neural system with an intensity image convolver. The processor's principal element is a Hughes liquid crystal light valve (LCLV). All components are commercially available and used without modification except for a liquid crystal television (LCLV). In operation the invention can be used as either a pre-processor to intensity normalize and edge enhance video scenes for use in pattern recognition applications or as a real-time pattern recognition device within itself, with the addition of an LCTV.

Incoherent image intensity normalization, contour enhancement, and

The spatial light modulator utilizes a modified liquid crystal television for modulating a laser beam so as to produce a transformed hologram image on a film plate which is identical with the video information being fed into the liquid crystal TV. Once a image film has been produced the film is developed and placed back in the system so that the system will now act as a comparator and tracking device. With the reference beam blocked and a new video input fed into the liquid crystal TV the system now will have an output only when the scene on the TV is identical to the scene recorded on the film. Indicator means give a signal output from this comparison that is identical.

Modified liquid crystal television as a spatial light modulator

A method of and apparatus for acousto-optically addressed pattern recognition using Vander Lugt matched filtering. In optical correlation a beam of light containing an image to be examined is directed to fall on a matched filter array that contains a representation of an object of interest. Critical alignment between the beam and a matched filter of the array is achieved by acousto-optical deflection of the light beam. A large number of matched filters can be addressed sequentially at very high sampling rates, thereby providing a large memory capability for coherent optical image processing. In the system an object beam containing an image of interest is directed to a plane of interest where the matched filter is located. An acousto-optical device located in the object beam path is driven by a signal generator at megahertz frequencies. The acousto-optical device converts the megahertz frequency signals to acoustic waves that affect the density of the optical path of the object wave, changing the index of refraction at a selected plane in this path. This spatial modulation of the index of refraction across the path of the wave causes the incident light to be deflected at selectable angles. By proper selection of the megahertz frequency driving signals these variable angles are selected to direct the Fourier transform of the object beam to selected ones of an array of matched filters at the focal plane, allowing rapid correlation of any incoming intelligence information on the object beam with prerecorded information stored in a filter array.

Large memory acousto-optically addressed pattern recognition

The apparatus 11 according to the present invention effectively eliminates losses to reflection and/or secondary emission of the charged particle beam 13 being measured. It comprises a sense cup (17) with an interior chamber and an entry opening (25) through which the charged particle beam (13) enters. A sense cone (19) forms the rear wall of the interior chamber with the cone apex adjacent the entry opening (25). An outer case (21) surrounds the sense cup (17) and is electrically insulated therefrom. Charged particles entering the interior chamber are trapped and are absorbed by the sense cup and cone and travel through a current measuring device (15) to ground.

Apparatus for measuring charged particle beam

Disclosed are a method and the chemical solutions (a blend of H.sub.2 SO..4 and CH.sub.3 COOH) employed for producing high quality crystal surfaces on CaF.sub.2 and BaF.sub.2 by a chemical polishing cycle that follows a multistage mechanical polishing cycle. The high quality crystal surfaces on CaF.sub.2 and BaF.sub.2, which otherwise are of the quality for field of use, makes these crystals ideally suited for applications as windows for HF/DF laser since the chemically polished crystal surface has fewer irregularities which reduce the amount of surface scattering of the HF/DF radiation, thus allowing a more predictable output. The high quality surfaces achieved from chemical polishing are of particular value in the study of optical absorption of very low loss materials, where the scattered radiation produces heat.

Growing community of inventors

Huntsville, AL, United States of America

Don A Gregory