Photoelectric detection of coherent light in filtered background light
Coherent light photoelectric detection probability in background light passing through narrow band filter of rectangular or Lorentz frequency characteristics
Helstrom, C. W.↗
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Elimination of coherent noise in a coherent light imaging system
Coherent noise elimination in coherent light imaging systems by time averaging noise concentrations through lens rotation about optical axis
Grebowsky, G. J.↗
Photoelectric detection of coherent light in filtered background light
Photoelectric detection of coherent light in filtered background light
Helstrom, C. W.↗
Elimination of coherent noise in a coherent light imaging system
Optical imaging systems using coherent light introduce objectionable noise into the output image plane. Dust and bubbles on and in lenses cause most of the noise in the output image. This noise usually appears as bull's-eye diffraction patterns in the image. By rotating the lens about the optical axis these diffraction patterns can be essentially eliminated. The technique does not destroy the spatial coherence of the light and permits spatial filtering of the input plane.
Grebowsky, G. J.↗
Coherent light scattering spectroscopy for supersonic flow measurements
A unified discussion on coherent light scattering spectroscopy and its spectral dependence on molecular gas velocity, temperature and density is presented. The feasibility of using coherent Raman spectroscopy techniques for nonintrusive measurements of supersonic flow parameters is demonstrated and recent laboratory as well as wind tunnel experiments are reviewed. In addition, the advantages of using coherent Rayleigh-Brillouin spectroscopy for measuring high pressure flows are discussed.
She, C. Y.↗
Amplitude and Transverse Quadrature Component Squeezing of Coherent Light in High Q Cavity by Injection of Atoms of Two-Photon Transition
The amplitude and transverse quadrature component squeezing of coherent light in high Q cavity by injection of atoms of two-photon transition are studied. The Golubev-Sokolov master equation and generating function approach are utilized to derive the exact variances of photon number and of transverse quadrature component as function of t. The correlation functions and power spectrums of photon number noise and of output photon current noise are also investigated.
Cao, Chang-Qi↗
A new real-time non-coherent to coherent light image converter - The hybrid field effect liquid crystal light valve
A new, high-performance device has been developed for application to real-time coherent optical data processing. The new device embodies a CdS photoconductor, a CdTe light-absorbing layer, a dielectric mirror, and a liquid crystal layer sandwiched between indium-tin-oxide transparent electrodes deposited on optical quality glass flats. The noncoherent image is directed onto the photoconductor; this reduces the impedance of the photoconductor, thereby switching the ac voltage that is impressed across the electrodes onto the liquid crystal to activate the device. The liquid crystal is operated in a hybrid field effect mode. It utilizes the twisted nematic effect to create a dark off-state and the optical birefringence effect to create the bright on-state. The liquid crystal modulates the polarization of the coherent read-out light so an analyzer must be used to create an intensity modulated output beam.
Grinberg, J.↗
Populating excited states of incoherent atoms using coherent light.
Study of the influence of various experimental parameters on the interaction between a multimode high-intensity laser light and the absorbing atoms of an atomic gas. Using a simplified treatment of line broadening which does not include correlations between momentum-changing collisions and pressure-broadening collisions, expressions are obtained that show the effect of pressure, laser-pulse length, and intensity on the excitation. It is found that, as long as the dephasing time of the atomic system is sufficiently short, the interaction reduces to a two-body collision between the atoms and photons, where coherence effects do not occur.
Mcilrath, T. J.↗
A coherent light scanner for optical processing of large format transparencies
A laser scanner is discussed in which the scanning beam is random-access addressable and perpendicular to the image input plane and the irradiance of the scanned beam is controlled so that a constant average irradiance is maintained after passage through the image plane. The scanner's optical system and design are described, and its performance is evaluated. It is noted that with this scanner, data in the form of large-format transparencies can be processed without the expense, space, maintenance, and precautions attendant to the operation of a high-power laser with large-aperture collimating optics. It is shown that the scanned format as well as the diameter of the scanning beam may be increased by simple design modifications and that higher scan rates can be achieved at the expense of resolution by employing acousto-optic deflectors with different relay optics.
Callen, W. R.↗
Polarization Characteristics of Spectralon Illuminated by Coherent Light
The Multi-angle Imaging Spectroradiometer (MISR) makes use of an on-board calibration system to provide routine absolute radiometric calibrations of the instrument while in flight. In addition to on-board detector standards, two spectralon panels will reflect sunlight into the nine cameras.
reflectance standards spectralon polarization↗
Optical-to-optical interface device
Studies were conducted on the performance of a photoactivated dc liquid crystal light valve. The dc light valve is a thin film device that consists of two transparent electrodes, deposited on glass substrates, that enclose a thin film photoconductor (cadmium sulfide) and a thin layer of a nematic liquid crystal that operates in the dynamic scattering mode. The work was directed toward application of the light valve to high resolution non-coherent light to coherent light image conversion. The goal of these studies was to improve the performance and quality of the already existing dc light valve device and to evaluate quantitatively the properties and performance of the device as they relate to the coherent optical data processing application. As a result of these efforts, device sensitivity was improved by a factor of ten, device resolution was improved by a factor of three, device lifetime was improved by two-orders of magnitude, undesirable secondary liquid crystal scattering effects were eliminated, the scattering characteristics of the liquid crystal were thoroughly documented, the cosmetic quality of the devices was dramatically improved, and the performance of the device was fully documented.
Jacobson, A. D.↗
Diffusion filter eliminates fringe effects of coherent laser light source
Diffusion filter comprised of small particles in colloidal suspension reduces the coherence of a laser beam used as a photographic light source. Interference patterns which obscure details in photographic film are eliminated, the intensity and collimation are moderately affected.
Olsasky, M. J.↗
System and Method for Scan Range Gating
A system for scanning light to define a range gated signal includes a pulsed coherent light source that directs light into the atmosphere, a light gathering instrument that receives the light modified by atmospheric backscatter and transfers the light onto an image plane, a scanner that scans collimated light from the image plane to form a range gated signal from the light modified by atmospheric backscatter, a control circuit that coordinates timing of a scan rate of the scanner and a pulse rate of the pulsed coherent light source so that the range gated signal is formed according to a desired range gate, an optical device onto which an image of the range gated signal is scanned, and an interferometer to which the image of the range gated signal is directed by the optical device. The interferometer is configured to modify the image according to a desired analysis.
Zuk, David M.↗
A method of measuring the amplitude-modulated vacuum field near a conducting mirror
Electromagnetic fields of the vacuum mode near a conducting mirror are modified with respect to those in free space, with their amplitudes having a sinusoidal spatial dependence from the mirror. Therefore if we combine this spatially amplitude-modulated vacuum field mode and intense coherent light with a beam splitter, we may detect this fluctuation of the vacuum mode in a homodyne detection scheme. It will give a new method to produce squeezed states of light with a single mirror placed close to an unused port of a beam splitter. We show that the amplitude fluctuation of the combined light can be reduced by a factor of 2 below that of the coherent light. We also discuss the limitations due to the finite line width of the laser and the effective absorption length of the photodiodes.
Youn, Sun-Hyun↗
Optical noise suppression device and method
A device and method is disclosed for suppression of optical noise in an optical spatial filtering system using highly coherent light. In the disclosed embodiment, input photographic film to be processed in the system, and output photographic film to be exposed, are each mounted on lateral translation devices. During application of the coherent light for exposure of the output film, the two translation devices are moved in synchronism by a motor-driven gear and linkage assembly. The ratio of the resulting output film translation to the input film translation is equal to the magnification of the optical data processing system. The noise pattern associated with the lenses and other elements in the optical processing system remains stationary while the image-producing light moves laterally through the pattern with the output film, thus averaging out the noise effect at the output film.
Horner, J. L.↗
Laser-Induced Fabrication of Metallic Interlayers and Patterns in Polyimide Films
Self-metallizing polyimide films are created by doping polyamic acid solutions with metallic ions and solubilizing agents. Upon creating a film, the film is exposed to coherent light for a specific time and then cured. The resulting film has been found to have a metallic surface layer and a metallic subsurface layer (interlayer). The layer separating the metallic layer has a uniform dispersion of small metal particulates within the polymer. The layer below the interlayer has larger metal particulates uniformly distributed within the polymer. By varying the intensity or time of exposure to the coherent light, three-dimensional control of metal formation within the film is provided.
Miner, Gilda A.↗
Parallel Information Processing (Image Transmission Via Fiber Bundle and Multimode Fiber
Growing demand for visual, user-friendly representation of information inspires search for the new methods of image transmission. Currently used in-series (sequential) methods of information processing are inherently slow and are designed mainly for transmission of one or two dimensional arrays of data. Conventional transmission of data by fibers requires many fibers with array of laser diodes and photodetectors. In practice, fiber bundles are also used for transmission of images. Image is formed on the fiber-optic bundle entrance surface and each fiber transmits the incident image to the exit surface. Since the fibers do not preserve phase, only 2D intensity distribution can be transmitted in this way. Each single mode fiber transmit only one pixel of an image. Multimode fibers may be also used, so that each mode represent different pixel element. Direct transmission of image through multimode fiber is hindered by the mode scrambling and phase randomization. To overcome these obstacles wavelength and time-division multiplexing have been used, with each pixel transmitted on a separate wavelength or time interval. Phase-conjugate techniques also was tested in, but only in the unpractical scheme when reconstructed image return back to the fiber input end. Another method of three-dimensional imaging over single mode fibers was demonstrated in, using laser light of reduced spatial coherence. Coherence encoding, needed for a transmission of images by this methods, was realized with grating interferometer or with the help of an acousto-optic deflector. We suggest simple practical holographic method of image transmission over single multimode fiber or over fiber bundle with coherent light using filtering by holographic optical elements. Originally this method was successfully tested for the single multimode fiber. In this research we have modified holographic method for transmission of laser illuminated images over commercially available fiber bundle (fiber endoscope, or fiberscope).
Kukhtarev, Nicholai↗
Problems and possible solutions involved in hard target calibration of coherent Doppler lidar
The field of radiometry is surveyed with reference to coherent light, since the surfaces to be considered here are irradiated with coherent, polarized light. Definitions of some concepts are modified. In light of these modifications calibration problems are analyzed and solutions suggested. The most important task was to develop hard targets exhibiting minimal specular reflection (mirror-like and retroreflection) and following closely a Lambertian scattering curve. Bistable reflectometer experiments and integrating sphere measurements are used to physically characterize the targets. Optical and electron microscopy are used to physically characterize the targets. Since the BRDF matrix is not measured, this capability must be developed preferably for both bistatic and monostatic reflectometer measurements. The equipment is expensive and not yet developed. Calibration can be simplified if it can be proved that the BRDF matrix is diagonal for a diffuse scatterer.
Anderson, Richard↗