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We report a multiframe blind deconvolution algorithm that we have developed for imaging through the atmosphere. The algorithm has been parallelized to a significant degree for execution on high-performance computers, with an emphasis on distributed-memory systems so that it can be hosted on commodity clusters. As a result, image restorations can be obtained in seconds to minutes. We have compared and quantified the quality of its image restorations relative to the associated Cramer-Rao lower bounds (when they can be calculated). We describe the algorithm and its parallelization in detail, demonstrate the scalability of its parallelization across distributed-memory computer nodes, discuss the results of comparing sample variances of its output to the associated Cramer-Rao lower bounds, and present image restorations obtained by using data collected with ground-based telescopes. OCIS codes: 100.1455, 100.3020, 110.3055, 110.4155.

A hybrid technique to simulate the imaging of space-based objects through cirrus clouds is presented. The method makes use of standard Huygens-Fresnel propagation beyond the cloud boundary and a novel vector trace approach within the cloud. At the top of the cloud, the wave front is divided into an array of input gradient vectors, which are in turn transmitted through the cloud model by use of the Coherent Illumination Ray Trace and Imaging Software for Cirrus. At the bottom of the cloud, the output vector distribution is used to reconstruct a wave front that continues propagating to the ground receiver. Images of the object as seen through cirrus clouds with different optical depths are compared with a diffraction-limited image. Turbulence effects from the atmospheric propagation are not included. OCIS codes: 100.3020, 280.1310, 290.1090, 080.2720, 350.5500.

The Air Force Phillips Laboratory is in the process of demonstrating an advanced space surveillance capability with a heterodyne laser radar (ladar) system. Notable features of this ladar system include its narrow micropulses (< 1.5 ns) contained in a pulse-burst wave form that allows high-resolution range data to be obtained and its high power (30 J/pulse burst) that permits reasonable signal returns from satellites. Recently, time-resolved image-domain signal-to-noise ratios have been derived for both the intensity projections calculated from the range-resolved reflective data and image information obtained with linear combinations of the projections. In this paper the signal-to-noise expression for intensity projections is validated by laboratory data. Key words: Laser radar, tomography, signal-to-noise.

Speckle imaging techniques have been shown to mitigate atmospheric-resolution limits, allowing near-diffraction-limited images to be reconstructed. Few images of extended objects reconstructed by use of these techniques have been published, and most of these results are for relatively bright objects. We present image reconstructions of an orbiting Molniya 3 spacecraft from data collected by use of a 2.3-m ground-based telescope. The apparent brightness of the satellite was 15th visual magnitude. Power-spectrum and bispectrum speckle imaging techniques are used prior to image reconstruction to ameliorate atmospheric blurring. We discuss how these images, although poorly resolved, can be used to provide information on the satellite's functional status. It is shown that our previously published optimal algorithms produce a higher-quality image than do conventional speckle imaging methods.

A new approach to three-dimensional tumor localization in turbid media with the use of measurements in a single plane is presented. Optical diffuse photon-density waves are used to probe the turbid medium. Relative amplitudes and phases are measured in the detection plane. Lateral localization is accomplished in the detection plane. With a Fourier optics approach, the scattered wave is reconstructed throughout the volume to provide depth localization. Computer-simulation results that validate this technique are presented. Applications of this technique to multiple tumors and to optical mammography are discussed. Key words: Diffuse photon-density waves, Fourier optics, optical imaging.

The use of support constraints for noise reduction in images obtained with telescopes that use adaptive optics for atmospheric correction is discussed. Noise covariances are derived for these type of data, including the effects of photon noise and CCD read noise. The effectiveness of support constraints in achieving noise reduction is discussed in terms of these noise properties and in terms of the types of algorithms used to enforce the support constraint. Both a convex-projections and a cost-function minimization algorithm are used to enforce the support constraints, and it is shown with the use of computer simulations and field data that the cost-function algorithm results in artifacts in the reconstructions. The convex-projections algorithms produced mean-square-error decreases in the image domain of approximately 10% for high light levels but essentially no error decreases for low light levels. We emphasize images that are well resolved by the telescope and adaptive-optics system. Key words: Adaptive optics, support, deconvolution, superresolution.

Previous analyses have predicted that improved power-spectrum estimation results from application of speckle-imaging postprocessing to compensated astronomical images. We report the first results, to our knowledge, of compensated-speckle-imaging experiments, conducted at a compensated telescope operated by the U.S. Air Force, that confirm these predictions. The power-spectrum signal-to-noise ratio is used as the metric for evaluating the performance. We report the results of power-spectrum estimation for a single star and three binary stars, and we reconstruct images of the binary stars using the bispectrum method to obtain the Fourier phase of the object. Compensated and uncompensated results are compared. A previously derived expression that expresses the power-spectrum signal-to-noise ratio in terms of the compensated optical transfer function statistics and object parameters is verified by experimental data.

Mathematical studies reveal that superresolution using support constraints improves the estimation accuracy of Fourier spectra. The expressions predict the extent of variance reduction as a noise correlation function. The studies indicate that superresolution is independent of the Fourier spectrum's bandwidth. Superresolution uses the enforced correlation mechanism and consequently is additive in nature.

The results of an extensive computer simulation study are presented in this paper. Optimal parameter values are determined for previously derived weighted least squares algorithms used to estimate an object's Fourier spectrum from its bispectrum. The relative quality of phase and power spectra estimated from bispectra is discussed, and it is shown that the useful portion of the bispectrum includes elements with offsets larger than the seeing cutoff spatial frequency.

We report on the first satellite feature reconstruction, to our knowledge, by use of range-resolved reflective tomography techniques from nonimaging laser radar data collected on an orbiting satellite. The reconstructed features were two retroreflectors mounted on a satellite. The data were collected with a coherent laser radar system located at the Maui Space Surveillance Site in Maui, Hawaii. We utilized a filtered backpropagation algorithm to reconstruct the images using intensity projections created from the raw data. Key components of the image reconstruction process included the calculation of tomographic angles, the alignment of the intensity projections to an appropriate center of rotation, and compensation for the lack of data for a full 360 [degrees] set of views. [C] 2001 Optical Society of America OCIS codes: 110.6960, 280.3640.

A new technique for modeling image transfer through cirrus clouds is presented. The technique uses a ray trace to model beam propagation through a three-dimensional volume of polydisperse, hexagonal ice crystals. Beyond the cloud, the technique makes use of standard Huygens-Fresnel propagation methods. At the air-cloud interface, each wave front is resolved into a ray distribution for input to the ray trace software. Similarly, a wave front is reconstructed from the output ray distribution at the cloud-air interface. Simulation output from the ray trace program is presented and the modulation transfer function for stars imaged through cirrus clouds of varying depths is discussed. [C] 2000 Optical Society of America OCIS codes: 100.3020, 280.1310, 290.1090, 080.2720.

The role that deconvolution plays in the achievable spatial resolution in optical diffusion tomography is examined for the case of imaging an inhomogeneity in an otherwise homogeneous medium. It is shown that, in the measured data, it is the shape of the turbid medium modulation transfer function that determines the maximum spatial resolution. When the turbid medium transfer function is deconvolved from the measured data, it is the signal-to-noise ratio properties of the Fourier-transformed measured data that determine the maximum spatial resolution. It is shown that deconvolution-based methods can improve the spatial resolution in measured data up to a factor of 5 for realistic noise levels. These results are demonstrated with computer-simulated data. OCIS codes: 170.5270, 170.7050, 170.3010, 100.1830, 100.2980.