Software has been developed for the SAINT program that simulates the operation of a Fourier Telescopy imaging system that could potentially be used to create images of a satellite in low earth orbit. Fourier telescopy uses multiple beams that illuminate the target with a fringe pattern that sweeps across it due to frequency differences between beams. In this way the target spatial frequency components are encoded in the temporal signal that is reflected from the target. The software simulates the propagation effects and target interaction effects that would be present in a real system. This enables the creation of a simulated received signal as a function of time. A particular problem was accurately modeling the appearance of the target as its aspect changes during a rapid transit over the transmitter and receiver. A novel reconstructor has been developed that compensates for atmospheric phase fluctuations affecting the large number of beams transmitted simultaneously (~10). The reconstructor solves for hundreds of image Fourier components simultaneously, permitting rapid reconstruction of the image.

Fourier Telescopy (FT) is an active imaging method which interferes spatially diverse, frequency-encoded laser beams on a distant target, and records a time history of the reflected intensity measured by a single photodetector on a large receiver. FT has been studied extensively for imaging Geostationary objects, using high-energy pulsed lasers to project triplets of laser beams, by gradually stepping over time through the multitude of u,v-plane baselines required for accurate object reconstruction. Phase closure among the received triplets plays a key role in canceling out random atmospheric phase errors between laser beams. A new method has been devised to apply FT to rapidly moving targets, such as LEO space objects. In order to implement the thousands of baselines in a short engagement time, approximately 20 continuous-wave laser beams are simultaneously broadcast, and the baseline configurations are rapidly changed through a dynamic optical element. In order to eliminate unknown atmospheric errors, a new type of global phase closure has been developed, which allows image reconstruction from the time history of measured total reflected intensity, originating from the complex 20-beam interference patterns. In this paper, we summarize the new FT LEO method, and give a detailed derivation of the phase closure and image reconstruction algorithms that will lead to ultra-high resolution images of fast-moving space objects.

High-resolution imaging of space-based objects is, and has been, a topic of significant interest. Considerable effort has been expended to develop techniques for compensating or correcting image degradations caused by unknown aberrations, resulting in many successful approaches. However, current techniques are limited to scenarios where the object of interest is either naturally illuminated or is itself radiating. Active illumination using laser light can overcome this limitation, but the applicable coherence properties introduce additional challenges. To utilize laser illumination, a multi-frame phase-diversity image reconstruction algorithm tailored to the statistics of coherent light is developed. The reconstruction problem is posed in the form of a regularized optimization over the space of object pixel values and atmospheric aberration parameters. The optimization objective function is derived from the statistics of the detected light, and a regularization term including information encoded in the pupilplane intensity statistics is added to include additional knowledge and better condition the inverse problem. A representative coherent imaging system is simulated and reconstruction results are presented.

For most radar or ladar systems range information is obtained from the time necessary for an electromagnetic pulse to propagate to a target and return to a receiving antenna. In contrast, we investigate a method that replaces temporal encoding of distance with spatial encoding. In particular, we use a self-referencing superposition of Laguerre-Gaussian beams to translate propagation distance into transverse rotation of cross-section of the beam intensity. We review the mathematical foundations of the technique and discuss models for simulating its performance in turbulent atmosphere. In addition, we present a simple technique to extract the rotation angle from a two-dimensional cross-section of the beam. Preliminary results indicate that the technique is robust with respect to propagation in a turbulent atmosphere.

Beam pointing is critical for laser ranging and imaging applications. Recently a technique has been developed that applies maximum likelihood estimation theory to estimate beam pointing parameters namely jitter and boresight from the statistics of the signal reflected from the target. In this paper we investigate the effect of atmospheric turbulence on this estimator through a wave optics computer simulation. The estimator was developed for vacuum propagation of a Gaussian beam, so its performance under these conditions was unknown. It was found that the estimator tends to provide a value that is associated with a combination of mechanical beam jitter and turbulence wander effects. In general, the estimator produces a value that is larger than the mechanical jitter. This work leads the way to a new estimator that incorporates both mechanical jitter and turbulence effects.

Previous papers introduced a method for simultaneously improving the spatial and spectral resolution of spectral images by developing a model of the spectral sensor and using this model in a statistical minimization algorithm. This paper expands on the Model-Based Spectral Image Reconstruction (MBSIR) algorithm by analyzing the lower bounds on the algorithm's performance. While the MBSIR algorithm improves both spatial and spectral resolution, just the spectral bounds will be analyzed in this paper. This is a valid approach since the functions describing the spatial and spectral blurring are separable. Two lower bounds will be analyzed. The first is the lower bound on spectral resolution and the second is on the spectral accuracy. The spectral resolution lower bound analyzes the improvement the MBSIR algorithm can achieve in resolving two closely spaced spectral features. The spectral accuracy lower bound analyzes the ability of the MBSIR algorithm to reconstruct a spectral feature at the correct location. The sensor model used for this analysis is the AEOS Spectral Imaging Sensor (ASIS). ASIS is located at the Maui Space Surveillance Complex (MSSC) and is used to collect spectral images of space objects. Since all of the objects that ASIS images are non-stationary, the bounds can be used to determine a filter sampling that balances imaging time and image enhancement through the development of a Spectral Reconstruction Capability Metric (SRCM). The SRCM is important for the operation of ASIS. ASIS collects one spectral image at a time to create the spectral image cube. Since ASIS is intended to image space objects that are in orbit, delays in collecting the entire spectral image cube could result in an orientation change in the object. The orientation change could prevent the MBSIR algorithm from working on the data. The SRCM provides a method for determining the optical collection parameters to minimize object motion while maintain algorithm performance. The SRCM also allows for a way to compare different parameters to determine the spectral imaging sensor design that best take advantage of the MBSIR algorithm.

An image reconstruction approach is developed that makes joint use of image sequences produced by a conventional imaging channel and a Shack-Hartmann (lenslet) channel. Iterative maximization techniques are used to determine the reconstructed object that is most consistent with both the conventional and Shack-Hartmann raw pixel-level data. The algorithm is analogous to phase diversity, but with the wavefront diversity provided by a lenslet array rather than a simple defocus. The log-likelihood cost function is matched to the Poisson statistics of the signal and Gaussian statistics of the detector noise. Addition of a cost term that encourages the estimated object to agree with a priori knowledge of an ensemble averaged power spectrum regularizes the reconstruction. Techniques for modeling FPA sampling are developed that are convenient for performing both the forward simulation and the gradient calculations needed for the iterative maximization. The model is computationally efficient and accurately addresses all aspects of the Shack-Hartmann sensor, including subaperture cross-talk, FPA aliasing, and geometries in which the number of pixels across a subaperture is not an integer. The performance of this approach is compared with multi-frame blind deconvolution and phase diversity using simulations of image sequences produced by the visible band GEMINI sensor on the AMOS 1.6 meter telescope. It is demonstrated that wavefront information provided by the second channel improves image reconstruction by avoiding the wavefront ambiguities associated with multiframe blind deconvolution and to a lesser degree, phase diversity.

This paper will analyze the performance degradation of the phase diversity algorithm due to error in modeling the noise statistics. In other words, it will answer the question: "What is the level of degradation, if any, when the true noise statistics is Gaussian (Poisson) but is modeled as Poisson (Gaussian) in the likelihood function?" Furthermore, many phase diversity studies have been performed with defocus as the diversity function. One may ask whether combining the defocus with another diversity function such as astigmatism could improve the performance. This paper will show that a phase diversity composed of an appropriate combination of defocus and astigmatism can result in performance superior to any one of the phase diversities considered separately.

Unconventional computer aided imaging approaches, such as bi-spectrum or multi-frame blind deconvolution, have been used for some time to obtain high resolution images of space based objects from the ground. This "looking up" imaging scenario is characterized by r0 diameters usually much smaller than the telescope aperture, and isoplanatic angles on the same order as the object under observation. Air to ground imaging on the other hand, is often characterized by relatively large r0 values usually about the same size of the imaging aperture, but very small isoplanatic angles. In such a case, where the scene covers many isoplanatic patches, it has been shown that improvements in image quality can be obtained by dividing the field of view into sub-regions and applying processing algorithms to each sub-region. Because r0 is roughly the diameter of the aperture, the primary aberration over a subregion is tip-tilt. Block matching algorithms that correct only the local tip-tilt over the sub-regions have been developed to run in near real time. Correcting higher order local aberrations, using a blind deconvolution algorithm, can lead to improved results but requires increased computation. In this presentation we seek to compare air-to-ground imagery with different levels of processing; first global tip-tilt only correction; second local tip-tilt correction; and finally local tip-tilt plus high order correction. The goal is to determine if the increased detail obtained at each step is worth in increased processing complexity.

The development of sensors that are compact, lighter weight, and adaptive is critical for the success of future military initiatives. Space-based systems need the flexibility of a wide FOV for surveillance while simultaneously maintaining high-resolution for threat identification and tracking from a single, nonmechanical imaging system. In order to meet these stringent requirements, the military needs revolutionary alternatives to conventional imaging systems. We will present recent progress in active optical (aka nonmechanical) zoom for space applications. Active optical zoom uses multiple active optics elements to change the magnification of the imaging system. In order to optically vary the magnification of an imaging system, continuous mechanical zoom systems require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of elements. By incorporating active elements into the optical design, we have designed, demonstrated, and patented imaging systems that are capable of variable optical magnification with no macroscopic moving parts.

The Magdalena Ridge Observatory Interferometer (MROI) is a US federally funded project to construct the world's most ambitious optical/IR (0.6-2.4micron) imaging interferometer at a 10,500ft-altitude site in New Mexico. In its initial phase it will consist of 6 telescopes, each 1.4m in diameter, separated by distances ranging from 7.5m to 340m. A second phase will upgrade the interferometer to a 10-telescope configuration, allowing a "snapshot" imaging capability. The MROI will deliver images with sub-milliarcsecond angular resolutions while simultaneously providing images over 5-70 spectral sub-bands. A key feature is that the array will have sufficient sensitivity to image a wide range of targets, including extragalactic targets and, potentially, geosynchronous satellites. We report on the design and current status of the array.

We examine the pairwise fringe formation process for Michelson stellar interferometry, focusing specifically on how the complex fringe visibility degrades with spatial sub-aperture decorrelations. The fringe intensity is formulated for spatially incoherent sources, radiating or re-radiating, thermal light over a spectral interval where the quasi-monochromatic and crossspectral purity approximations can be invoked. The imaging geometry is such that the source in distant enough to use the far-field approximation, and that a unique optical transfer function exists consistent with isoplanatic, or equivalently, linearly shift invariant imaging systems. It is shown that the complex fringe visibility is functionally dependent on the optical transfer function although the stellar interferometer does not form an image directly as would conventional imaging. The complex visibility is derived from the fringe intensity. Three forms of the complex visibility are developed and each formulation is interpreted.

We explore the problem of reconstructing a 3-d model of a convex object from unresolved time-series photometric measurements (i.e., lightcurves). The problem is broken into three steps. First, the lightcurves are used to recover the albedo-area density of the object as a function of the surface normal. The ill-posedness of this inversion is considered and a suitable regularization scheme proposed. Second, the albedo and area contributions are separated using either transits or additional measurements at different wavelengths. Finally, the Minkowski problem is solved to produce the 3-dimensional shape corresponding to the area density.

We examine the feasibility of applying oximetry for the assessment of the degree of brain activity. Changes in concentration of oxygenated and deoxygenated hemoglobin may be used to determine the activity levels through differential attenuation in red and infrared (IR) spectral lines. We extend the classical mathematical model for oxygen saturation to include multiplicative and additive noises, signal gain, and detector responsivity. We perform temporal correlation between two signals (red and IR) to increase immunity to noise. This is particularly important when we consider dynamic biological processes and that the movement is always present. In the literature the difficulty of movement (differences in optical paths) is resolved with electronic solutions. We improve the effect of time displacement between signals at the level of equations. The considerations of noise in the saturation expression are significant when the signal levels approach zero.

We characterize the fluorescence of Europium Thenoyltrifluoroacetonate (EuTTA) with respect to temperature for its use in formation of thermal images. Current applications of EuTTA are for the measurement of temperature distribution of systems in contact with it. With this work we extend its applications to include measuring temperature changes due to thermal irradiation. We characterize the EuTTA's fluorescence obtaining a sensitivity of 2.2 % K^-1 at 300 K. Minimum resolvable temperature difference ΔT_min for layout is 0.09 K, at same temperature, in our laboratory. We deposit a thin film of the material over an aluminum sheet and use a laser to generate heat over its surface. The EuTTA's fluorescence response to the incident heat is measured with a fiber optic spectrometer. We compare the measured thermal response to heat transfer model of our device. Measured thermal response to constant heat irradiation is 1.86 K. Thermal responses to heat pulses with duration of 1 and 5 seconds are 0.2 K and 0.78 K, correspondingly. We measure the variation of fluorescence due to constant heat input, and to heat pulses of duration of 1 and 5 seconds.

We propose a polar discretization as a flexible mathematical model for describing extra-solar radiation. The analysis permits us to predict both: the spatial and the frequency responses of optical systems pointing to an extra-solar star. The spatial response provides information of the misalignment between extra-solar star and optical system. We propose a polar representation in the convolution scan followed by a space transformation to compute the frequency content of the incoming radiation. To the best of our knowledge, the spatial frequency content has not been determined thus before. We demonstrate that the circularly concentric discretization (i.e., complex polar array of radiation sources) predicts an increment on spatial information, and a reduction on the frequency content with respect to conventional stellar models.

We applied vectorial shearing interferometer to the visualization of different combustion regions in the flame. Using the shearing interferometer as edge identifier, the following regions are localized: background (no flame), the hottest part of the flame, internal cone and primary flow of air and fuel. In addition to the so-called surface of stoichoimetric balance, we identify a volume where complete combustion takes place.

We derived an expression for the absorption coefficient of dental tissue that considers the effect of the energy absorbed during single pulse. We complemented the mathematical model that describes the thermal distribution in tooth. We used this model to simulate dental tissue ablation with Er:YAG laser. Good agreement between the simulated predictions and the published experimental results is found for low values of fluence, less than 100 J/cm².

We use exact ray trace to calculate the prism tolerance for manufacturing errors. We model the manufacturing errors by modifying the position of the prism vertices. The normal to the prism faces modify the direction of the rays. We determine the prism tolerance by analyzing the optical transversed path rays. We calculate the change to the image (position in 3D space) introduced by this deviation. When the manufacturing tolerance is maintained at ± 0.3 arc sec, the maximum wave-front deviation is λ/10 for 633 nm wavelength. The calculated tolerance improves the performance of the Dove prism in 99% with respect to the tolerance of ± 2 arc sec. This work complements a previous analysis on a Dove prism for its application in a rotational shearing interferometer.

We determine the temperature distribution within the flame as a function of position. We determined temperature distribution and the length of a flame by dual-wavelength thermometry, at 470 nm and 515 nm. The error percentages on the temperature and the flame length measurements are 1.9% as compared with the predicted thermodynamic results.

We develop some conditions to detect extra-solar planets with rotational shearing interferometer. We consider that the star is not on the interferometer axis. In addition, we include an arbitrary optical path difference between the interferometer arms. Previously, we showed that the light from the star may be cancelled out when the OPD is λ/2. We obtain analytic expressions for these conditions. We simulate several incidance distributions of the star-planet system. It is of utter most importance to align the interferometer axis with the host star, to the precision of 5 μrad.

A classifier of great capabilities and a good-selection of different features are two key and difficult keys answering for a high accuracy classification result. On the classifier, although there are all kinds of algorithms, most of them couldn't be used widely because of multifarious theoretical limitations. In this paper, based on the TM data, several representative interpretation features, including original bands, texture measurements and spatial metrics, are compared systemically for landcover/landuse classification test with the same classifier and the same training samples. The results show that different feature source has different relationship with the original band and they play the different roles. Summarily, the original bands are the most useful and essential feature source and play the important role and the others can only be seen as equivalent or enhanced feature source. Among which, the texture mean have equivalent capability as that of the original bands, and the spatial metrics and other texture measurements can be seen as compensatory source. For the combination of different features, the classification accuracy can be improved by using the texture measurements or the combination with original bands. As a sort of newly features, the classification accuracy was very poor if only landscape metrics were used, comparatively the accuracy can be greatly improved by combing with the original bands. So, the combination of original bands and texture measurements is the preference for TM dataset.

The shearing interferometry is an alternative technique for assessment and measurement of wave-front aberrations. The vectorial shearing interferometer uses a displacement system to shear a wave front in vectorial form. We describe the wave-front displacement system incorporating a novel configuration of a pair of wedge prisms. Its main advantage is that the shearing is constant from the displacement system to image plane. The shear direction depends of the relative orientation of the prisms. The magnitude of the shearing is proportional to the distance between prisms. The proportionality constant depends of the wedge angle and the material of the prisms. This constant gives the sensibility to the displacement of the system. We describe and analyze the wave-front propagation through the displacement system using the exact ray trace. The deviation of the shearing by the difference in the wedge angles is larger than the produced by the oblique incidence of the wave front. Finally, we compare experimental results with exact ray trace simulations. We observe that the theoretical data corresponds to the experimental results. There is a maximum rms error of ≈ 10 μm.

We propose a novel method to reconstruct Transmission Profile Function (TPF) information based on visibility measurements. In specific occasions, V<<1, the TPF is proportional to the visibility squared. Extremely low visibilities (~10^-8) hinder the capacity of the technique to recover information. We evaluate three biomedical cases to confirm TPF reconstruction. First, we assess a three-dimensional multilayer skin model to demarcate limits on the reconstruction process. A three-dimensional female breast phantom with spherical tumors is evaluated next. We concentrate on technique performance to describe tissue morphology. Reconstructed TPFs with different resolutions are presented. Agreement between modeled and recovered information is demonstrated. Finally, a healthy and metastatic liver is compared. We demonstrate that a reconstructed TPF comparison enables (potentially) the diagnosis of alien tissue.

Any device built to measure the radiation power density, such as photocells, photomultipliers, takes relies on the absorption of radiation by matter. In this presentation, we are interested in the description of the incident radiation, in particular in how to express the number of photons and their fluctuations for different spectral compositions of light, such as laser or chaotic light. We investigate the temperature dependence of the photon number and the corresponding radiation power density, as well as their fluctuations. In case of coherent states such as in laser light, only one term appears in the expression for the energy fluctuations, characteristic also for particles. In case of chaotic light, there are two terms in the expression for the energy fluctuations of which one is characteristic of particles and the other of waves. This is a manifestation of the dual particle-wave nature of light.

The presence of ions in LC displays influences the performance of the displays through their transport driven by the applied voltage, especially at low driving frequencies. The ion transport causes important degradation of the electro-optical characteristics of displays. We present a model of the ion transport mechanisms taking place within a LC display. Various ionic effects with strongly different time constants are considered and two main competing driving potential screening effects are assumed, caused by free ions in LC layer and free ions in alignment layers, respectively. The role of insulation layers separating ions in LC from the electrodes is considered which can switch a cell between different regimes (cell decay and charging-up of the cell); also the asymmetry of the cell and the problem of balancing the LC and alignment layers ions are addressed. For various ion concentrations, the transmittance of the LC cell is calculated and compared with experimental results.

Specific resistivity of glassy carbon material is reported as a function of temperature in interval [0 - 800 C]. Concurrent determination of voltage, current, and temperature is described. Temperature is assessed radiometrically. At room temperature, specific resistivity of glassy carbon has been measured to be equal to 3.02 x10^-5 Ωm. At higher temperatures, specific resisitvity of glassy carbon decreases linearly with temperature, with negative thermal coefficient of -1.25 x 10^-8 Ωm/C.

The performance of Pb_0.8Sn_0.2Te photodiodes and photoconductive detectors based on Pb_1-x-ySn_xGe_yTe:In epitaxial films has been investigated in a wide temperature interval and at various background fluxes. It was found that dark current of photodiodes in the temperature range 30 K < T < 100 K was due to the generation-recombination in depletion region and at T < 30 K tunneling through defects in the depletion region dominated and incremental resistance R_0tun at T < 30 K was exponential function of R_og-r at T = 77 K. Detectivity of more than 5 x 10¹² cmHz^1/2W^-1 limited by preamplifier noise at a background of 1 x 10¹² cm^-2s^-1 and T = 30 K was experimentally achieved. Pb_1-x-ySn_xGe_yTe:In epitaxial film photoconductive detectors had sensitivity in the spectral range λ < 15μm and it exponentially depended on temperature and varied from 10⁵ A/W at T = 10 K to 10² A/W at T = 30 K. Noise of the photoconductive detectors was independent of background flux when it varied from 10¹² cm^-2s^-1 to 10¹⁸ cm^-2s^-1. Multielement photoconductive detectors based on these films were fabricated and D^* = 1.7 x 10¹³ cmHz^1/2W^-1 at T ≤ 25 K was achieved.