This month, we include a small special section that covers the broad nature of infrared radiometric sensor calibration. Guest editor Alan Thurgood has selected a sampling of papers from the annual symposium on Infrared Radiometric Sensor Calibration that is hosted by the Space Dynamics Laboratory at Utah State University and the National Institute of Standards and Technology (NIST). The latest of these symposia was held 13–15 May 1997. The goal of the symposium is to provide a forum for those engaged in the calibration and evaluation of infrared radiometric sensors.

The spatial infrared imaging telescope (SPIRIT III) radiometer is the primary instrument aboard the Midcourse Space Experiment (MSX), which was launched on April 24, 1997. The Space Dynamics Laboratory at Utah State University (SDL/USU) developed and implemented a ground-based procedure to optimize the focus of the SPIRIT III radiometer. The procedure used point source data acquired during ground measurements. These measurements were obtained with a calibration source consisting of an illuminated pinhole near the focus of a cryogenically cooled collimator. Simulated point source measurements were obtained at multiple focus positions by translating the pinhole along the optical axis inside and outside the optimum focus of the collimator. The radiometer was found to be slightly out of focus, and the detector focal plane arrays were moved to positions indicated by the test results. This method employed a single cryogenic cycle to measure both the distance and direction needed to adjust each array for optimal focus. The results of the SPIRIT III on-orbit stellar point source observation demonstrate the success of the technique. The method and hardware used to achieve focus optimization are described.

The spatial uniformity of two nonimaging concentrators is measured, each with a silicon photodetector positioned immediately behind the concentrator. The comparison is made between a compound parabolic concentrator (CPC) and a ?i/?o concentrator. The latter consists of a parabolic section followed by a cone section to restrict the divergence angle of the exit beam. The spatial uniformity of the ?i/?o concentrator measured with an f/4 beam diverging from a circular aperture is 1.2% across the central 4 mm of the entrance aperture of the concentrator, and demonstrates the use of this type of concentrator for effectively maintaining high throughput when using small-area (<2-mmdiam) detectors in applications requiring small fields of view. The uniformity of the gold-coated ?i/?o concentrator measured with a nearly collimated HeNe laser beam is not nearly as good, due in part to the imperfect reflectance of gold. The uniformity of the CPC in the f/4 beam is not nearly as good as that of the ?i/?o concentrator in the f/4 beam.

The spatial infrared imaging telescope (SPIRIT III) radiometer is the primary instrument aboard the Midcourse Space Experiment (MSX), which was launched on April 24, 1996. The SPIRIT III radiometer observed various orbital and suborbital targets, celestial sources, zodiacal emissions, the earth’s airglow, the aurora, and other upper atmospheric phenomena until its cryogen was depleted on February 26, 1997. During its on-orbit mission, the temperature of the radiometer focal planes rose as the cryogen was depleted, which resulted in expected changes in the radiometer’s responsivity. The responsivity’s dependency on temperature was quantified from ground calibration experiments to determine correction functions. These correction functions were verified by applying them to on-orbit observations of internal stimulators. The characterization of the dependence of responsivity on focal plane temperature is presented, the temperature effects as a function of integration mode and response level are described, and the results of applying these corrections to on-orbit internal stimulator data are given.

A temperature-dependent linearity correction function is derived using ground calibration data for the spatial infrared imaging telescope (SPIRIT III) radiometer. First, a small-signal analysis is used to derive linearity correction functions for each array at several focal plane temperatures. These functions are used to derive a single temperaturedependent linearity correction function for each array. The arrays exhibit some detector-dependent nonlinearity. A temperature- and detectordependent linearity correction function is developed by modifying the temperature-dependent array-average linearity correction function so that the half-scale nonlinearity is correct for each detector in the array. Using the nonuniformity correction (NUC) coefficient of variation (COV) as a metric, this temperature- and detector-dependent linearity correction function results in a COV between 0.35 to 2.6% for all arrays, depending on the array and integration mode.

The Space Dynamics Laboratory at Utah State University (SDL/USU) calibrated the spatial infrared imaging telescope (SPIRIT) radiometer as part of its contract with the Ballistic Missile Defense Organization (BMDO). During the calibration effort, SDL/USU discovered and characterized a phenomenon that reduces the detector dark offset and responsivity after saturation, which results in increased calibration uncertainties directly following a saturation event. The magnitude and recovery duration for the dark offset and responsivity depend on several variables, including saturation flux level, saturation integration mode, integration mode, focal plane temperature, and saturation duration. Detector-to-detector variations in the magnitude of the saturation effect were also observed for detectors within an array. This phenomenon and the methods used to characterize it are described.

We present the derivation of the Midcourse Space Experiment (MSX) SPatial InfRared Imaging Telescope (SPIRIT III) ‘‘truth’’ inband irradiances and associated uncertainties for the six primary calibration stars in the six IR radiometer bands. The inband irradiances are calculated from the approved stellar spectral irradiances S(?) from the literature and the measured end-to-end relative spectral response R(?) curves for the bands. The spectral uncertainties associated with the stellar spectra and the instrument response are propagated to provide total uncertainties for the inband irradiance values.

The Space Dynamics Laboratory at Utah State University (SDL/USU) designed, built, and calibrated the Midcourse Space Experiment’s (MSX) spatial IR imaging telescope (SPIRIT III) spectrometer and radiometer as part of the MSX program. During calibration, one of the parameters characterized was the spectrometer’s spatial responsivity, which determines the relative object-space detector positions, maps the detector field of view, and computes the effective field-of-view solid angle. SDL/USU performed this calibration both on the ground and onorbit. The two calibration efforts produced similar results, although detector position shifted about 264 mrad on-orbit. The methods and results from these two calibration efforts are compared and the various approaches to determine a sensor’s spatial responsivity are discussed.

The spatial infrared imaging telescope (SPIRIT III) Fourier transform spectrometer, a Michelson interferometer, contains six IR detectors having independent fields of view and spectral responsivities. The Space Dynamics Laboratory at Utah State University (SDL/USU) designed, built, and calibrated the instrument for the Midcourse Space Experiment (MSX) sponsored by the Ballistic Missile Defense Organization (BMDO). The spectrometer uses a HeNe laser to record the optical path difference introduced by moving one mirror in the spectrometer. Spectral line position errors in the spectrometer were expected as a result of slight deviations in the optical axes of each detector and the reference laser detector relative to the optical axis of the instrument. These spectral line position errors were measured for the spectrometer by comparing measurements of earthlimb radiance to published line position values from the HITRAN database. These errors were fit to a model of the expected optical axis deviations to generate correction factors for the SPIRIT III spectrometer and to infer the approximate effective focal plane location of the reference laser detector relative to the focal plane location of each detector.

The measurements of pollution in the troposphere (MOPITT) instrument is an IR radiometer that uses gas correlation spectroscopy to detect carbon monoxide and methane in the earth’s troposphere. The instrument concept was developed by the Department of Physics of the University of Toronto and it was designed, manufactured and tested by COM DEV Ltd., Canada, the prime contractor, for the Canadian Space Agency. MOPITT will be flown on the National Aeronautics and Space Administration (NASA) earth observing system (EOS) AM1 platform in mid 1998. The MOPITT instrument has eight optical channels that operate in the spectral band 2130 to 4510 cm-1 (2.2 to 4.6 µm). The radiometric calibration of the instrument is achieved by using four onboard compact high-emissivity calibration sources working in the range 285 to 500 K that were designed, manufactured and tested at Bomem, Inc., Canada. A description of these calibration sources and the results of the qualification and acceptance testing performed are presented.

The solid-state imaging subsystem (SSI) on NASA’s Galileo Jupiter orbiter spacecraft has already demonstrated its superior performance as a scientific imager by returning stunning pictures of several planetary bodies as well as detailed inflight calibration data during its cruise to Jupiter. The SSI inflight performance remains excellent; the instrument calibration is stable and accurate. Improved determinations of the SSI’s absolute spectral radiometric response and scattered-light properties have been made. Evaluation of the camera’s point spread function suggests that the focus setting may be slightly nonoptimum, but the spatial resolution in returned images is still very good. The shielding of the SSI’s CCD detector against energetic particle radiation appears to be adequate for operation in Jupiter’s intense radiation field. New camera modes, onboard editing and data compression capabilities, and an adaptive mission operations plan have been implemented for the Jupiter orbital mission phase in order to mitigate the effects of a spacecraft anomaly that limits the allowable data return rate from Jupiter. These new capabilities are expected to allow the accomplishment of a historic scientific investigation of the Jupiter system using the SSI.

An acousto-optic time-integrating correlator with center frequency 80 MHz, bandwidth 40 MHz, time aperture 10 µs, and signal bandwidth 20 MHz was designed and assembled. A novel electronic method for estimating the overall optical misalignment in the processor was devised and tested. It represents a simple and robust alternative to purely optical procedures. The resolution accuracy of the method is limited by the CCD pixel dimensions. As a side result, the scaling law that applies to the output signal when using CCD detection is also derived.

Image compression plays an important role in the archiving and transmission of medical images. Discrete cosine transform (DCT)- based compression methods are not suitable for medical images because of block-like image artifacts that could mask or be mistaken for pathology. Wavelet transforms (WTs) are used to overcome this problem. When implementing WTs in hardware, finite precision arithmetic introduces quantization errors. However, lossless compression is usually required in the medical image field. Thus, the hardware designer must look for the optimum register length that, while ensuring the lossless accuracy criteria, will also lead to a high-speed implementation with small chip area. In addition, wavelet choice is a critical issue that affects image quality as well as system design. We analyze the filters best suited to image compression that appear in the literature. For them, we obtain the maximum quantization errors produced in the calculation of the WT components. Thus, we deduce the minimum word length required for the reconstructed image to be numerically identical to the original image. The theoretical results are compared with experimental results obtained from algorithm simulations on random test images. These results enable us to compare the hardware implementation cost of the different filter banks. Moreover, to reduce the word length, we have analyzed the case of increasing the integer part of the numbers while maintaining constant the word length when the scale increases.

The well-known LBG algorithm uses binary splitting for generating an initial codebook, which is then iteratively improved by the generalized Lloyd algorithm (GLA). We study different variants of the splitting method and its application to codebook generation with and without the GLA. A new iterative splitting method is proposed, which is applicable to codebook generation without the GLA. Experiments show that the improved splitting method outperforms both the GLA and the other existing splitting-based algorithms. The best combination uses hyperplane partitioning of the clusters along the principal axis as proposed by Wu and Zhang, integrated with a local repartitioning phase at each step of the algorithm.

In the framework of European Space Agency (ESA) FluidPac satellite mission, we have developed a fast, lossy image compression algorithm (ICA) based on a slight variation of the classical 2-D fast Fourier transform (FFT). In essence, given a monochrome picture, the ICA calculates (almost) its Fourier spectrum. It then applies a low-pass filter to eliminate all Fourier coefficients beyond a certain user-defined cutoff frequency. Finally, it further compresses by encoding the surviving FFT coefficients in a more memory efficient manner. The proposed scheme works best with pictures where the high-frequency data are of little value. This is precisely the case with electronic speckle pattern interferometer (ESPI) images. The ICA low-pass filter removes the speckle noise while preserving the useful scientific information: the interference fringe pattern. We have, however, also applied the FluidPac ICA to pictures generated by classical interferometers, photographic equipment, particle tracing instruments, and IR cameras. The results are extremely encouraging.

Restoration for actual atmospherically blurred images is performed using an atmospheric Wiener filter that corrects simultaneously for both turbulence and aerosol blur by enhancing the image spectrum primarily at those high frequencies least affected by the jitter or randomness in a turbulence modulation transfer function (MTF). The correction is based on weather-predicted rather than measured atmospheric MTFs. Both turbulence and aerosol MTFs are predicted using meteorological parameters measured with standard weather stations at the time and location where the image was recorded. A variety of weather conditions and seasons are considered. Past results have shown good correlation between measured and predicted atmospheric MTFs. Here, the predicted MTFs are implemented in actual image restoration and quantitative analysis of the MTF improvement is presented. Corrections are shown also for turbulence blur alone, for aerosol blur alone, and for both together.

A synthetic reference (SR) or fiducial mark is a target that has been designed and placed within a scene in order to help to locate objects. When a scene containing a small SR is acquired through a pixelated device (such as a CCD camera) and this SR is located using a digitally computed normalized correlation search, there is a lowering of the correlation peak if the target SR is displaced a nonwhole number of pixels with respect to the position of the previously acquired model SR. We propose a framework where the lowering is related to detection reliability, in order to compare the performance of different sizes and shapes of SR. This framework has been applied to eight SRs having simple shapes, using synthetic scenes. Results show large differences in their detection reliability according to their shape. A SR in the shape of a 45-deg-tilted square shows the best behavior among all the studied shapes, and one can take advantage of this fact when designing an application dealing with small-size SRs.

An image diffusion method based on the adaptive smoothing approach proposed by Saint-Marc et al. (1991) is presented. We first investigate the behavior of the adaptive smoothing approach for computing simplifications of an input image, a basic problem in image analysis. Whereas the original adaptive smoothing algorithm achieves satisfactory results for 1-D signals, the unequal strength of the boundaries of images (2-D signals) poses a difficult problem. We propose the addition of an edge-strengthening step that addresses that problem. Results show significant improvements. However, this added step requires us to (1) extract a set of edge pixels and (2) obtain certain edge information (in particular, edge-side location). These tasks are interrelated, and their computation is described. In addition, the limitations of the adaptive smoothing approach are studied in depth.

We present a theoretical study of the effects of threedimensional canopy structure on directional thermal infrared exitance. A physics-based model employing steady-state energy budget formulations is used to compute scene element temperatures. Two approaches are then used to combine soil and vegetation contributions to the composite scene response. One method uses a plane-parallel abstraction of canopy architecture to estimate canopy view factors for weighting of soil and vegetation emission terms. The second approach employs computer graphics and rendering techniques to estimate 3-D canopy view factors and scene shadows. Both approaches are applied to a test agricultural scene and compared with available measurements. The models correctly estimate hemispherically averaged thermal infrared exitance to within experimental error with root-mean-square errors of 15.3 W m-2 for the 1-D model and 12.5 W m-2 for the 3-D model. However, the 1-D model systematically underestimates exitance at high sun angles. Explicit modeling of canopy 3-D row structure indicates potential directional anisotropy in brightness temperature of up to 14°C.

One important issue in phase-shifting interferometry is to eliminate or compensate for phase shift errors. One solution is to adopt a least-squares technique in that actual reference values of phase shifts are readily identified directly from interferograms. This however, requires a relatively long computation time since a considerable amount of intensity information must be processed in an iterative way. To cope with this problem, we present an accelerated version of a least-squares phasemeasuring algorithm that can drastically reduce computation time.

By using a laser diode as the pump source and KTP as the intracavity doubling crystal, we have achieved green laser output at 0.5295 µm from a new crystal, Nd:Sr5(PO4)3F. The threshold power is 10 mW, and the TEM00-mode green laser output power is 40.4 mW at 400-mW incident pump power of the diode laser, corresponding to an optical efficiency of 10.1%. The theoretical formula for a cw intracavity frequency-doubled laser is given and is in agreement with the experimental result.

The authors present a systematic approach for the structural design of doublet lenses in accordance with a prespecified set of Gaussian parameters and primary aberration targets. This approach obviates the need for heuristic selection of glasses for the constituent lens elements. An identical approach is implemented for the structural design of both cemented and broken contact doublets. The optimization procedure is the well-known least-squares method. For facilitating convergence a second-derivative damping technique is utilized. Constraints are taken care of by suitably defined continuously differentiable penalty functions that are treated as pseudoaberrations in optimization. A strategy for dynamic weightage of the components of the defect function is devised for overcoming stagnation at the local optimum in the immediate neighborhood of the starting point. The strategy is also effective in constraining the glasses of the constituent elements of the doublet within the permissible glass domain. Some illustrative examples are given.

The displacement sensing accuracy of the reflected beam method in a turbulent environment is studied experimentally. The method includes an illuminated corner cube retroreflector (CCR) and a lateral effect photodiode (LEP) by which the image position of the CCR is detected. The results show turbulence (Cn~5X10-7m-1/3) limited measurement resolution to vary from 0.6 to 9 mm (standard deviation) in the distance range from 50 to 300 m. The result is 1.4 to 2.1 times worse than that measured for the direct beam sensor in the same atmospheric conditions. The CCR used is found to have no systematic effect on the achievable resolution but the method is found to be very sensitive to receiver defocusing. An approximately 10-fold increase in standard deviation is observed when the receiver is defocused by 2%. The possibility to average out part of the angular fluctuations by using multiple CCRs is verified. By using two CCRs instead of one, when positioned 1.3 m apart at a distance of 150 m, a resolution better by 22% is achieved. The averaging in the case of the LEP, however, is not effective because the noncorrelated intensity fluctuations of the reflections from the different CCRs cancel the averaging effect.

A writer verification system based on multiple neural network classifiers is described, aimed to be easily extendable. Each writer registers with the system by writing a set of discrete Chinese characters. One neural network is constructed for each enrolled character class on a per-person or a per-subgroup basis. The decisions from individual network classifiers are combined by voting. The method has been verified to work reliably on our testing database: a verification rate above 96% is achieved on short-term data.

A two-layer neural network architecture for carrying out optodigital classification operations is proposed. The optical neural network implementation is suitable for pattern recognition and classification into digital format. The neural network is based on an optical correlator, an optoelectronic threshold, and an optodigital encoder. The module needs only one laser light source, and the light propagation from the input to the output is uninterrupted. The output is the class of the input pattern encoded in a digital format. Experimental results using different images and classes are presented. The classification can be changed arbitrarily by changing the encoding mask.

The posterior capsule opacification images considered are images of the membrane encapsulating an artificial lens implanted during cataract surgery in place of the natural lens. The images are taken to monitor the state of the patient’s vision after the surgery. Subsequent to the surgery, the membrane of the posterior capsule may become opacified, thus degrading the patient’s vision. We discuss the methodology used and the results obtained in the segmentation of the images into transparent and opacified regions. The opacification is primarily characterized by its texture, therefore a directional standard deviation operator is applied to an image giving rise to a family of ‘‘conjugate’’ images. From these images, the multi-dimensional histogram (co-occurrence) array is calculated and subsequently approximated by Gaussian distributions to form the basis for the segmentation step.

Free-space optical communication between satellites networked together can permit high data rates between different places on Earth. The use of optical radiation as a carrier between the satellites permits very narrow beam divergence. Due to the narrow divergence and the large distance between the satellites, pointing from one satellite to another is difficult. The pointing task is further complicated by vibration of the pointing system caused by tracking noise and mechanical impacts. In this work we derive mathematical performance models for digital direct detection communication satellite networks as a function of the system parameters, the number of satellites, and the vibration amplitude. The optical intersatellite network model considered includes a transmitter satellite, regenerative satellites, and a receiver satellite all networked together. A comparison between three communication system modulation schemes—on-off keying (OOK), pulse position modulation (PPM), and pulse polarization binary modulation (PPBM)—is presented. These models are the basis for optical communication tracking- and pointing-system design of appropriate complexity and performance to make the network as simple and inexpensive as possible. From the analysis it is clear that even low vibration amplitude of one satellite pointing system decreases the network performance dramatically.

The principle and design of a self-routing 16 X 16 free-space optically interconnected crossbar cell switch are detailed. Vertical cavity surface emitting lasers (VCSELs) and VCSEL-based smart pixel arrays are key devices for this system and enable high density interconnection. Using the optical switching of VCSEL polarization extensively, the cell switch exhibits a potential high bit rate and low reconfiguration time between two cells. Moreover, because of the high speed switching of the VCSEL between its two linear polarizations, address substitution, which is one of the asynchronous transfer mode (ATM) requirements, can be implemented. A compact cell-switch demonstrator is proposed that uses low-cost optically recorded holograms and microlens arrays.

A novel automatic profilometry technique using the dual frequency of an optical fiber projection grating is introduced. 3-D shape can be measured automatically with this technique even with the problems of true discontinuities and phase noise. This method combines a singlemode optical fiber phase-shifting interferometer as the illumination part of the configuration. The design of the optical fiber interferometer has the following features: (1) easily adjustable fringe space and rotation and (2) automatic phase shifting. In addition, it has a number of important advantages over the more conventional methods for producing projection fringes, such as extremely small size and weight, high visible fringes with little noise and absolute sinusoidal intensity distribution, etc. These are very important and necessary to dual-frequency automatic measurement of 3-D shapes. Fringes generated by the interferometer are analyzed, and the relationship between the fringe phase and height distribution of an illuminated diffused surface is derived. The dual-frequency automatic phase unwrapping method is described. An example of the profilometry in operation is given.

The principle of laser common-path interference profilometry based on the theory of Gaussian beams is analyzed and its measurement equation is deduced. From the measurement equation, the main factors that affect the vertical resolution of the profilometer are discussed. According to the conclusions of the analysis, laser common-path interference profilometry can be used to measure microprofiles of fine surfaces with subnanometer vertical resolution.

A multiwavelength imaging pyrometer (MWIP) is described that permits real-time remote sensing of temperature profiles of targets with unknown emissivity by measuring the spectral radiance of a target at several distinct wavelengths using a 3203122-element PtSi ir CCD imager with an assembly of seven narrowband ir filters in the range from 1790 to 4536 nm. Based on these measurements, the temperature and model parameters of the target emissivity are determined simultaneously from the least-squares fit of the theoretical model of the ir camera output signal to the experimental data. The real-time least-squares minimization is accomplished by combination of Levenberg-Marquardt and simulatedannealing algorithms. The experimental MWIP system also includes a least-squares-based calibration algorithm for evaluation of effective values of peak filter transmissions and center wavelengths based on the detection of radiation emitted by the precalibrated blackbody source over a wide range of temperatures. To achieve high radiometric accuracy, the ir CCD camera was operated with black-level and background subtraction and with compensation for dark-current charge as a function of the detected signal level. To minimize the effect of the response nonlinearity on the accuracy of real-time MWIP temperature estimation, we have developed an algorithm that provides for imager operation at fixed preselected signal level for each spectral channel by adaptively changing the duration of the optical integration time of the imager. Initial testing demonstrated an accuracy of ± 1.0°C for real-time temperature measurements of the center of the blackbody aperture in the range from 500 to 1000°C. Temperature resolution of ± 3°C was demonstrated for the blackbody source viewed through a double-side polished silicon wafer with unknown spectral transmissivity in the temperature range from 500 to 900°C.

Details of an integrated apparatus to measure spectra of both the magneto-optical Kerr and the Faraday effect by the use of a rotating analyzer are given. The absolute values of both the Kerr rotation angle ?k and the ellipticity ?k can be determined by means of an achromatic quarter-wavelength retarder. The system is simple and reliable, and fully controlled by a computer. The measured values of the Kerr and Faraday effects for one MnBi(Al) film sample and for one GaP crystal sample are given. Since the magnitude of the Faraday rotation signal is proportional to the sample thickness, one must be careful in determining the fundamental energy gap by use of the Faraday spectrum only. Employment of the Fourier-transform technique will enable the system to measure both the Kerr and the Faraday effect in a wider data range from onehundredth to a few hundred degrees.

A long-working-distance fiber-optic-based confocal Raman spectroscopy (CRS) system, operating in the backscatter mode, was developed for rapid noninvasive characterization of ocular tissue. In vitro near-real-time axial scanning through ocular tissue was achieved using a CCD camera and a high-numerical-aperture long-working-distance microscope objective in a telecentric configuration. The system provides high spatial resolution (20 to 150 µm) of transparent ocular tissues up to 13 mm deep into the eye in a noncontact fashion while utilizing low argon-laser power and rapid scanning times (25 mJ), yielding a SNR range from 30 to 75. To test the performance of the system for characterizing ocular tissue, Raman spectra from rabbit eyes were obtained in vitro. Axial scans of the cornea, the aqueous humor, and the lens provided discrete and specific Raman spectra from each tissue, in both the lower and the higher wave-number region. Characteristic Raman signals common to all tissues are the OH vibrations (1650 and 3100 to 3700 cm-1) and the vibrations corresponding to amino acids (phenylalanine at 1003 cm-1, tryptophan at 760 and 881 cm-1, and tyrosine at 646 cm-1). The ocular lens can be identified by three distinct peaks (aromatic and aliphatic CH stretching and OH bending modes), of which the aromatic CH stretching mode (?3057 cm-1) is lens-specific. The cornea can be identified by the presence of two distinct peaks (aliphatic CH stretching and OH bending) and the absence of the aromatic CH stretching mode. The aqueous humor can be identified by the presence of the OH bending mode and the lack of the both CH stretching modes. A long-working-distance confocal Raman spectroscopy system may offer a novel technique for the noncontact spatially resolved biochemical characterization of various tissue layers of the anterior segment of the eye.

We theoretically and experimentally investigated the influences of the sensing and lead fiber length, the extinction ratio of the input polarizer, and the coherence properties of the light source on polarimetric temperature measurements. We have shown that there is a possibility to construct a simple and inexpensive fiber optic polarimetric thermometer for absolute temperature measurements by using a low extinction-ratio polarizer and a low-coherence source. An experimental temperature sensor for absolute temperature measurement that works in the range from 20 to 60°C has been produced.

Reticle systems, which are widely used in infrared (IR) missile seekers, are considered to be the classical approach for estimating the position of a target in the field of view (FOV). A new simulation tool is proposed that gives tracking results of the concentric annular ring reticle seeker in various cases. Our simulation model is applicable to the development of the advanced seekers. When false targets such as flares are present in the FOV, simulation results show that the existing seeker cannot determine the precise target location. To decrease the susceptibility to countermeasures such as flares, we propose an efficient counter-countermeasure using signal prediction and correlation. In the simulation results, we ascertain that with our technique the reticle seeker can perform more effective target tracking than previous seekers.

There is a need in the x-ray imaging community for phosphors with short persistence (I /Ib<0.1 to 0.01% in less than 0.5 ms). Persistence limits a detector’s performance by defining the minimum xray exposure discernible for a given time after a previous exposure, by ghosting of previous images, and by limiting the dynamic range. We characterize the persistence and relative light output of 25 commercially available and specially synthesized phosphors, five of which are gadolinium oxysulfide (Gd2O2S) with five different activators. The phosphor’s ‘‘practical efficiency’’ is presented for use with either front- or rearilluminated CCDs. The persistence of these phosphors is characterized as a function of x-ray intensity, exposure time, and, when possible, impurity concentrations. Each phosphor’s usefulness for particular x-ray imaging experiments is also discussed.

Given the pace of development in this most dynamic field, there is a continuing need for up-to-date, authoritative texts appropriate for advanced undergraduates, graduate students, and research and development practitioners. There has been a steady stream of books throughout the years aimed at satisfying this requirement, with varying degrees of success. Every once in a while, though, there comes a significant book— one that makes a particularly valuable contribution by virtue of its scope, style, depth of coverage, or distinctive interpretation.

This PDF file contains the editorial “High-Level Vision: Object-Recognition and Visual Cognition” for OE Vol. 36 Issue 11

This PDF file contains the editorial “Optical Fiber Sensors, Volume Three: Components and Subsystems” for OE Vol. 36 Issue 11

This PDF file contains the editorial “Deconvolution of Images and Spectra, 2nd Edition” for OE Vol. 36 Issue 11