Microwave Radiometric Detection of Oil SlicksRadiometry and the Detection of Optical RadiationOptical Systems Design Detection EssentialsOptoelectronic Workshops 7: Advanced Technology for Radiometry and the Detection of Optical RadiationStudies of Radio Frequency Interference Detection Methods in Microwave RadiometryPassive Infrared DetectionAdvances in Radiometry ResearchDetection and Assessment of Dental CariesMicrowave and Millimeterwave Remote Sensing for Security ApplicationsNon-Imaging Microwave and Millimetre-Wave Sensors for Concealed Object DetectionIntroduction to Radiometry and Photometry, Second EditionOptical Radiation Measurements: Grum, F. C., Becherer, R. RadiometryMicrowave Radiometric Studies in Relation to Mine DetectionMicrowave Radiometry and Remote Sensing of the Earth's Surface and AtmosphereMILLIMETER WAVE RADIOMETRIC DETECTION OF TARGETS OBSCURED BY FOLIAGE.Applied Photometry, Radiometry, and Measurements of Optical LossesPassive Standoff Detection of Chemical Vapors by Differential FTIR RadiometryClinical Application of Microwave Radiometry Techniques in the Detection of CancerPhotometry, Radiometry, and Measurements of Optical LossesRadiometryIce/frost Detection Using Millimeter Wave RadiometryFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsEM Detection of Concealed TargetsLaser Photothermal Radiometry for the Detection of Early Enamel DemineralizationRadio Frequency Radiometry for the Remote Airborne Detection of Small Forest FirDetection and Characterization of Nuclear CloudsAn Application of Pattern Recognition to Radiometric Target DetectionTheory of Broadband Autocorrrelation Radiometry for Spectral Line DetectionInfrared Detectors and SystemsRadiometry Detection of Acoustic SignalsDetection of Greenbug Infestation Using Ground-based RadiometryRadiometry and the Detection of Optical RadiationW-band Radiometry for the Non-invasive Investigation of MaterialsHuman Presence Detection Using Millimeter-wave RadiometryRadiometry for Low Target DetectionUse of Airborne Microwave Radiometry for the Detection and Investigation of Oil Slicks at SeaFeasibility Study of Radiometry for Airborne Detection of Aviation HazardsIntroduction to Radiometry and PhotometryRadio Frequency Interference Characterization and Detection in L-band Microwave RadiometryDetection of Abandoned Underground Coal Mines by Geophysical Methods

Radiometry and the Detection of Optical Radiation

A new architecture for photorefractive adaptive filtering is introduced. This architecture is based on the principle of time-integrating correlator with a photorefractive material as the time-integrating photosensor. A compact and rugged system is achieved by using the same Bragg cell as both the delay line for computing correlation values and the delay to which the tap weights are applied. In this way a self-aligning structure is achieved. Semiconductor photorefractive materials are used with 1.2-1.3-microm wavelength injection lasers to achieve fast response, low power, and a compact structure. Tests of an experimental system demonstrated >40-dB rejection of narrow-band interference with a transient response time constant of 70micros.

Photorefractive adaptive filter structure with 40-dB interference rejection.

Coherent illumination (12) is used to illuminate a symmetrical alignment mark (18) with an image rotation interferometer (26) producing two images of the alignment mark, rotating the images 180° with respect to each other, and recombining the images interferometrically. The recombined images interfere constructively or destructively, in an amplitude and or polarization sense depending upon the method of recombination, when the alignment sensor (10) is located at the center of the alignment mark. The rotation interferometer (26) is preferably a solid glass assembly made of a plurality of prisms. A detector (28) extracts the alignment information from the image rotation interferometer (26). The resulting center of the alignment mark (18) is accurately determined. A relatively large number of different alignment mark patterns may be utilized, as long as the alignment mark patterns exhibit one hundred and eighty degree symmetry. Parallel lines, a grid pattern, or a checkerboard grating may be used. The alignment sensor (10) may be applied to a scanning photolithographic system providing sinusoidal alignment signals. The alignment system is particularly applicable to photolithography as used in semiconductor manufacturing.

Mark independent alignment sensor

The data obtained by Quasi-Elastic Light-Scattering Spectroscopy on twenty five alkane-oxygen sooting flames are presented. This optical method, based on the interaction between particles and their surrounding, allows the granulometric study of the soot aerosol evolution accounting for the specific aerosol regime existing in the considered flame. Diffusion Broadening and/or Photon Correlation Spectroscopy adapted to a Brownian aerosol in a flowing high temperature medium are used for the simultaneous measurements of soot diameter and number density or diameter and polydispersity. The data reduction method employed permits easy analysis including the transit time and the polydispersity aspects of the scatterers. Soot coagulation growth rates are also determined for these flames.

Extensive Measurements on Soot Particles in Laminar Premixed Flames by Quasi Elastic Light Scattering Spectroscopy

Forward wave interactions in photorefractive materials

An apparatus is described which performs optical processing on electrical signals to calculate the triple product integral in a manner which accommodates high bandwidth signals, which processes were formerly possible only in mechanically unstable designs.

High bandwidth triple product processor using a shearing interferometer

Adaptive linear predictors have found important application in channel equalization, source redundancy removal, speech encoding and analysis, interference and noise rejection, signal classification, adaptive control, and adaptive antenna systems. In an effort to provide adaptive linear predictors of wide bandwidth, several optical implementations have been proposed. This paper reviews and analyzes the existing optical architectures, putting them in a common framework. Four new common-path architectures are proposed and compared with the others.

Optical adaptive linear predictors.

This paper presents a nonmechanical method of measuring temporally coherent light which may be dominated by incoherent background radiation. To obtain detection in the presence of high levels of incoherent radiation, the detector must reject constant and fluctuating contributions due to incoherent light. Extreme sensitivity of the method derives from preferentially modulating the coherent light in such a way that the exact periodicity of the resulting detected signal component is known, permitting, in principle, processing gains which are almost arbitrarily large. Wavelength estimates are also obtained, even when the coherent source power is orders of magnitude less than the power of background radiation. The approach lends itself to rugged and easily constructed implementation. This paper then provides an in-depth noise analysis of the general approach. Numerical examples are also given. Results of a crude laboratory test are presented. Although limited by shortcomings of the components at hand, the experiment demonstrated easy measurement of coherent radiation >40 dB below the ambient incoherent light and discernible output at a signal-to-interference level of −53 dB.

Electrooptic detector of temporally coherent radiation

The use of a photorefractive material as an adaptive beam combiner is described. The beam combiner is demonstrated in an interferometric optical signal processor. The photorefractive beam combiner offers the advantage of exact phase matching between interfering beams over an extended period of time.

Photorefractive adaptive beam combiner: use in a crossed acoustooptic cell correlator

The recent success in performing incoherent-light Fourier transforms on static objects prompted an investigation to see whether space-integrating acoustooptic signal processors could be made with incoherent-light sources. This paper is a summary of highlights from that research. Methods of implementing the excisor, radiometer, and ambiguity processor are presented. Experimental results are given showing successful operation of each.

Jonathan D. Cohen

Papers

High bandwidth triple product processor using a shearing interferometer

Optical adaptive linear predictors.

Electrooptic detector of temporally coherent radiation

Photorefractive adaptive beam combiner: use in a crossed acoustooptic cell correlator

Incoherent-light space-integrating acoustooptic processors