Showing papers on "Signal beam published in 1970"

Efficiency and Image Contrast of Dielectric Holograms

Abstract: The contrast and diffraction efficiency of a dielectric hologram made from a diffuse signal beam is calculated. Diffraction efficiency of 64% with acceptable image contrast is possible. Experimental results with holograms made by bleaching photographic emulsions are presented.

Weapon system for the detection of and use against stationary or moving objects

Abstract: Weapons system for both detection and affecting of stationary or moving objects. A laser beam is generated at a relatively low power level and caused to monitor, as by sweeping, a predetermined zone or space. Said laser beam or a portion thereof is reflected by and from an object appearing within said zone or space and is sensed by suitable detection means. The detection means provides the input to a computer which then locks the generator onto said object and simultaneously increases the power emitted therefrom to a predetermined higher, as destructive, value. Friendly objects operating within the same area can be caused to emanate a signal beam which is sensed simultaneously with the sensing of the reflected laser beam and prevents the actuation of the computer.

Holographic image recording and reproducing system

Abstract: A holographic image recording and reproducing system for use with a conventional television receiver. A laser beam which is intensity modulated in accordance with video information is projected through a Bragg cell deflection system to provide a scanning image beam. The undiffracted output beam from the Bragg diffraction scanning system is employed as the reference beam. The reference beam and the scanning signal beam are converged by an optical lens system at a Fourier transform plane where a light responsive film is transported. Image data from an entire horizontal scanning line of the TV image is overlapped to provide a single holographic image, and a separate deflection mirror or other deflecting system is provided to sweep the scanning signal beam and the reference beam, still converged, slowly across the width of the even more slowly moving film. For playback, the reference beam component is removed, the film is swept by an unmodulated scanning signal beam following the same scanning pattern as the original recording signal beam, and a photodetector is positioned on a projection of the path of the original reference beam to reconstruct the television signal for playback through the TV receiver.

Characteristics of dielectric holograms

Abstract: The diffraction efficiency and signal-to-noise ratio for two-dimensional and volume diffuse-signal-beam holograms are calculated and experimentally determined. Calculations are based on the statistical properties of the signal beam, and exact integrals rather than series approximations are used. High signal-to-noise ratio and high diffraction efficiency are possible, with the peak calculated diffraction efficiency being 22% for two-dimensional and 64% for volume holograms. The experimentally achieved efficiencies were 12% for two-dimensional and 36% for volume holograms.

Mixing Partially Coherent Fields with Gaussian Irradiance Profiles; Optimization Criteria

Abstract: A detailed analysis of the average signal-to-noise ratio (SNR) resulting from the mixing or heterodyning of partially coherent, collinear beams with gaussian irradiance profiles is undertaken. It is shown that SNR can be expressed as a function of the beam cross sections and coherence areas and the area of the photodetector. The dependence of SNR on each of these parameters is examined. The previously observed saturation phenomenon, as well as coherence suppression and degradation effects, are observed and explained theoretically. Optimum values of the local oscillator beam size and coherence area are derived which generally produce the best SNR for a given set of signal beam parameters.

Amplitude weighting in holography

Abstract: Holographic system in which the signal (object) beam, the reference beam, or the readout beam is weighted (i.e., shaped) in amplitude as a function of the spatial coordinates of the hologram plane. Either the reference beam or the signal beam may be weighted in accordance with the light distribution of the signal beam to provide smaller variation in modulation, or unity modulation, for the various spatial frequencies in the signal beam over the entire area of the hologram. The readout beam may be shaped or weighted to further compensate for the variation in diffraction efficiency caused by the interaction of the residual variations in the modulation level and the nonlinearities of the recording medium.

Multiple image storing system for high speed projectile holography

Abstract: A THREE BEAM SYSTEM FOR OBTAINING A HOLOGRAPHIC RECORD ON FILM OF A HIGH SPEED PROJECTILE, WHEREIN A COHERENT BEAM OF RADIATION IS DIVIDED INTO A REFERENCE BEAM, A DIRECT SIGNAL BEAM AND A REFLECTED SIGNAL BEAM. THE REFERENCE BEAM IS DIRECTED WITHOUT MODULATION TO A PHOTOGRAPHIC PLATE AND THE DIRECT SIGNAL BEAM IS DIRECTED TO THE PHOTOGRAPHIC PLATE AFTER TRANSMISSION BY THE PROJECTILE. THE REFLECTED SIGNAL BEAM IS DIRECTED INTO A BEAM STEERER WHICH ALLOWS THE SYNCHRONOUS TRACKING OF THE PROJECTILE WITH THE REFLECTED SIGNAL BEAM. ON REFLECTION FROM THE PROJECTILE THE REFLECTED SIGNAL BEAM IS INCIDENT ON THE PHOTOGRAPHIC PLATE. AS THE INCLUDED ANGLE BETWEEN THE REFERENCE BEAM AND THE REFLECTED SIGNAL BEAM CHANGES, MULTIPLE IMAGES OF THE TARGET WILL BE STORED IN THE THICK EMULSION OF THE PHOTOGRAPHIC PLATE.

Spatial filtering properties of the reference beam in an optical heterodyne receiver.

Abstract: The optical heterodyne receiver with signal-conditioning optics is treated as an active spatial filter for applications in which the signal source is located in the Fresnel field region of the receiver. A theorem is presented and proved which shows that any thin, passive, optical elements placed in the signal beam for the purpose of spatially filtering the signal radiation may be replaced by an equivalent heterodyne reference beam. This theorem can simplify the analysis of optimum optical heterodyne receiver configurations and offers alternative methods for practical implementations.