This paper compares an optimal linear time-invariant controller and an adaptive controller for prediction and control of aero-optical wavefronts derived from recent flight-test data. Both control methods have the form of multichannel prediction filters that capture the statistics of the aero-optical turbulence to mitigate latency in the adaptive optics loop. Experimental results show the improvement in wavefront correction achieved by both prediction methods. Altering the flow characteristics of the disturbance wavefront during the control process illustrates the ability of the adaptive controller to track changes in the aberration statistics.

Adaptive optics (AO) can be used to mitigate turbulence; however, when a single deformable mirror is used for phaseonly compensation of thermal blooming, analysis predicts the possibility of instability. This instability is appropriately termed phase compensation instability (PCI) and arises with the time-dependent development of spatial perturbations found within the high-energy laser (HEL) beam. These spatial perturbations act as local hot spots that produce negativelens- like optical effects in the atmosphere. An AO system corrects for the hot spots by applying positive-lens-like phase compensations. In turn, this increases the strength of the thermal blooming and leads to a runaway condition, i.e., positive feedback, in the AO control loop. This study uses computational wave-optics simulations to model horizontal propagation with the effects of thermal blooming and turbulence for a focused Gaussian HEL beam. A point-source beacon and nominal AO system are used for phase compensation. Previous results show that a high number of branch points limit the development of PCI for phase compensation of only thermal blooming. For phase compensation of thermal blooming and turbulence, the number of branch points decreases and system performance is reduced. A series of computational wave-optics experiments are presented which explore the possibility for PCI.

Closed-loop adaptive optical correction using a deformable mirror based on the total internal reflection (TIR) from an electrostatically deformed liquid-air interface was performed on a collimated beam of a HeNe-laser that was aberrated by a rotating phase disk. The frequency response of the system was measured and the influence of liquid surface motion in absence of external optical aberrations on the liquid mirror was characterized. The performance of the AO system was determined for static and dynamic aberrations for various sets of system parameters.

The crosstalk problem inherent in holography based modal wavefront sensing (HMWS) becomes more severe with increasing aberrations of the incident beam. In this paper, the cause of crosstalk is theoretically revealed and then demonstrated using simulations. For extending the use of HMWS in correcting atmospheric turbulence introduced aberration, the sensor response is statistically analyzed with random aberrations created in accordance with the atmosphere turbulence model. The system parameters are optimized considering the turbulence strength and calibrated response curves are further used to improve the sensor performance. The simulation and first preliminary experimental results are shown for validating the method.

Optical imaging in a highly scattering medium is effective only at very shallow depths which limits its use as a diagnostic tool in biomedical imaging. By combining optical and acoustic modalities, high-contrast, physiologicallyrelevant optical information at higher spatial resolutions can be achieved. Hybrid imaging modalities such as acoustooptic and photoacoustic imaging improve resolution over conventional optical imaging, but tissue scattering results in poor signal-to-background ratios especially in deeper tissues. To overcome these challenges, we have developed a novel microbubble (MB) contrast agent surface-loaded with a self-quenching fluorophore. In response to ultrasound, the MB expands and contracts, generating changes in fluorophore surface density. The changes in physical separation between fluorophores modulate the quenching efficiency and produce a fluorescence intensity modulation. To our knowledge, this is the first experimental demonstration of ultrasound modulation of fluorescence using a self-quenching MB scheme. The modulation is spatially localized to the ultrasound focal zone where the pressure is greatest and the largest MB oscillations are induced. The modulated signal can be extracted from a large constant light background, increasing detection sensitivity. This technique can enable sensitive optical imaging with ultrasound-scale sub-millimeter spatial resolution, overcoming significant challenges of optical imaging in deep tissue. The contrast agent MBs were prepared with a shell of phospholipid and lipophilic self-quenching fluorophore. MB ultrasound response was studied in a custom setup which monitored fluorescence emitted from an insonified sample. Fluorescence signals displayed clearly modulated intensity and the fast Fourier transform (FFT) showed a strong component at the ultrasound driving frequency.

A new hyperspectral imaging system is constructed based on the idea of compressive sensing (CS). The compressed hyperspectral measurements are acquired and unmixed directly with the proposed algorithm which determines the abundance fractions of endmembers, completely bypassing high-complexity tasks involving the hyperspectral data cube itself. Without the intermediate stage of 3D hyper-cube processing, data reconstruction and unmixing are combined into a single step of much lower complexity. We assume that the involved endmembers' signatures are known and given, from which we then directly compute abundances. We also extend this approach to blind unmixing where endmembers' signatures are not precisely known a priori.

Building on the mathematical breakthroughs of compressive sensing (CS), we developed a 2D spectrometer system that incorporates a spatial light modulator and a single detector. For some wavelengths outside the visible spectrum, when it is too expensive to produce the large detector arrays, this scheme gives us a better solution by using only one pixel. Combining this system with the "smashed filter" technique, we hope to create an efficient IR gas sensor. We performed Matlab simulations to evaluate the effectiveness of the smashed filter for gas tracing.

Polarimetric SAR imaging is a direct-detection LADAR imaging technique designed to synthesize a large aperture made up of independent detectors all sensing a common beam of light that is polarized in nature. The aperture synthesis allows the array of detectors to achieve spatial resolution consistent with a monolithic aperture of a similar size. Unanswered questions remain about the use of this technique including how much power/aperture product is required in order to achieve a specified degree of spatial resolution. Also of concern is how much speckle averaging is necessary to overcome noise inherent in this type of synthetic aperture system. This paper addresses these questions by formulating relationships between array size, target size, laser energy per pulse, number of pulses required in averaging and the desired resolution of the system. Computer simulations are presented which demonstrate these relationships for a common resolution target.

The process of laser scanning a target to form an image through atmospheric turbulence is studied in terms of the optical transfer function (OTF). The problem of scanning a two-dimension target within the Fresnel zone distance is examined for long and short time exposures. An OTF for wave front tilt is introduced to describe the specific effect of beam wander. An analysis for typical operational parameters shows that wave front tilt can be a more significant limitation to imaging performance at high spatial frequencies than short exposure effects (e.g., beam spread). Wave optics simulations are performed to visualize the performance of the scanning method through turbulence and compare the results with the theoretical model.

The goal of this work is to develop an algorithm to enhance the utility of 3D FLASH laser radar sensors through accurate ranging to multiple surfaces per image pixel. Using this algorithm it will be possible to realize numerous enhancements over both traditional Gaussian mixture modeling and single surface range estimation. While traditional Gaussian mixture modeling can effectively model the received pulse, we know that the received pulse is likely corrupted due to optical aberrations from the imaging system and the medium through which it is imaging. Additionally, only identifying a single surface per pulse may result in the loss of valuable information about partially obscured surfaces. Ultimately, this algorithm in conjunction with other recent research may allow for techniques that enhance the spatial resolution of an image, improve image registration and enable the detection of obscured targets with a single pulse.

We describe results from new computational techniques to extend the reach of large ground-based optical telescopes, enabling high resolution imaging of space objects under daylight conditions. Current state-of-the-art systems, even those employing adaptive optics, dramatically underperform in such conditions because of strong turbulence generated by diurnal solar heating of the atmosphere, characterized by a ratio of telescope diameter to Fried parameter as high as 70. Our approach extends previous advances in multi-frame blind deconvolution (MFBD) by exploiting measurements from a wavefront sensor recorded simultaneously with high-cadence image data. We describe early results with the new algorithm which may be used with seeing-limited image data or as an adjunct to partial compensation with adaptive optics to restore imaging to the diffraction limit even under the extreme observing conditions found in daylight.

In this paper we present some experimental results of speckle imaging for near-diffraction-limited observation of ground-based scenery and astronomical objects through atmospheric turbulence. The method of alternating projections onto convex sets is used for iterative reconstruction of the point-spread function (PSF), combined with Wiener filtering for deconvolution and several pre-processing techniques. A modification of the optical system with aperture segmentation is considered. The results of imaging on a horizontal path and astronomical imaging are reported and compared with time averaged and best frame images. Apparent image improvement is demonstrated in a field much wider than the isoplanatic patch size.

Most non-conventional approaches to image restoration of scenes observed over long atmospheric slant paths require multiple frames of short exposure images taken with low noise focal plane arrays. The individual pixels in these arrays often exhibit spatial non-uniformity in their response. In addition base motion jitter in the observing platform introduces a frame-to-frame linear shift that must be compensated for in order for the multi-frame restoration to be successful. In this paper we describe a maximum aposteriori parameter estimation approach to the simultaneous estimation of the frame-to-frame shifts and the array non-uniformity. This approach can be incorporated into an iterative algorithm and implemented in real time as the image data is being collected. We can not only estimate the scene, but also the angle dependent point spread function. We present a brief derivation of the algorithm as well as its application to actual image data collected from an airborne platform.

Various image de-aliasing techniques and algorithms have been developed to improve the resolution of pixel-limited imagery acquired by an optical system having an undersampled point spread function. These techniques are sometimes referred to as multi-frame or geometric super-resolution, and are valuable tools because they maximize the imaging utility of current and legacy focal plane array (FPA) technology. This is especially true for infrared FPAs which tend to have larger pixels as compared to visible sensors. Geometric super-resolution relies on knowledge of subpixel frame-toframe motion, which is used to assemble a set of low-resolution frames into one or more high-resolution (HR) frames. Log-polar FFT image registration provides a straightforward and relatively fast approach to estimate global affine motion, including translation, rotation, and uniform scale changes. This technique is also readily extended to provide subpixel translation estimates, and is explored for its potential combination with variable pixel linear reconstruction (VPLR) to apportion a sequence of LR frames onto a HR grid. The VPLR algorithm created for this work is described, and HR image reconstruction is demonstrated using calibrated 1/4 pixel microscan data. The HR image resulting from VPLR is also enhanced using Lucy-Richardson deconvolution to mitigate blurring effects due to the pixel spread function. To address non-stationary scenes, image warping, and variable lighting conditions, optical flow is also investigated for its potential to provide subpixel motion information. Initial results demonstrate that the particular optical flow technique studied is able to estimate shifts down to nearly 1/10^th of a pixel, and possibly smaller. Algorithm performance is demonstrated and explored using laboratory data from visible cameras.

Airglow luminescence in the SWIR region due to upper atmospheric recombination of solar excited molecules is a well accepted phenomenon. While the intensity appears broadly uniform over the whole sky hemisphere, we are interested in variations in four areas: 1) fine periodic features known as gravity waves, 2) broad patterns across the whole sky, 3) temporal variations in the hemispheric mean irradiance over the course of the night, and 4) long term seasonal variations in the mean irradiance. An experiment is described and results presented covering a full year of high resolution hemispheric SWIR irradiance images. An automated gimbal views 45 hemispheric positions, using 30 second durations, and repeats approximately every half hour through out the night. The gimbal holds co-mounted and bore-sighted visible and SWIR cameras. Measuring airglow with respect to spatial, temporal, and seasonal variations will facilitate understanding its behavior and possible benefits, such as night vision and predicting upper atmosphere turbulence. The measurements were performed in a tropical marine location on the island of Kauai Hi.

Projection-based chromotomographic spectrometers are sensors that collect both spatial and spectral information with fairly simple optical as well as electronic hardware. Efforts to utilize them for remote sensing applications have met with obstacles primarily due to the fact that the impulse response of the imaging system as a function of wavelength must be know in order to reconstruct the spatial/spectral content of the scene under study. This paper reports a blind deconvolution algorithm specifically designed to reconstruct the spectrum of the scene under study as well as an estimate of the wavelength dependent atmospheric transfer function of the system. The method is tested using simulated data with realistic turbulence and noise factors in order to demonstrate its effectiveness.

The observation of satellites at geostationary earth orbits (GEO) from the ground presents some formidable technical and scientific challenges. In recent years, several approaches have been proposed and some have undergone field tests. The Naval Research Laboratory has pioneered the use of the Michelson-style sparse aperture interferometers for this problem by using the Naval Prototype Optical Interferometer (NPOI). Other groups have proposed the use of Intensity Interferometry to solve this problem. It is in this framework that we are addressing the issue of comparing Signal-to-Noise-Ratio (SNR) expressions and numerical simulations for various approaches in order to establish which is the most suitable technique for ground based observations. In this paper we present a comparison of SNR simulations for a Michelson Interferometer, an Intensity Interferometer and a filled aperture telescope. We present the basic background of the two interferometric techniques and the standard SNR expressions for the three approaches. We review the parameters of the simulations discussing the limitations and we will present the results.

Phase retrieval is explored for image reconstruction using outputs from both a simulated intensity interferometer (II) and a hybrid system that combines the II outputs with partially resolved imagery from a traditional imaging telescope. Partially resolved imagery provides an additional constraint for the iterative phase retrieval process, as well as an improved starting point. The benefits of this additional a priori information are explored and include lower residual phase error for SNR values above 0.01, increased sensitivity, and improved image quality. Results are also presented for image reconstruction from II measurements alone, via current state-of-the-art phase retrieval techniques. These results are based on the standard hybrid input-output (HIO) algorithm, as well as a recent enhancement to HIO that optimizes step lengths in addition to step directions. The additional step length optimization yields a reduction in residual phase error, but only for SNR values greater than about 10. Image quality for all algorithms studied is quite good for SNR≥10, but it should be noted that the studied phase-recovery techniques yield useful information even for SNRs that are much lower.

We simulate observations of geostationary satellites using different optical interferometer array configurations. We test several array designs, including the typical Y shaped array, a couple of circular arrays, telescopes mounted on a linear movable boom, and a couple of arrays of 30 telescopes on a non redundant and a redundant hexagonal grid. We use aperture synthesis techniques to reconstruct images from the simulated observations. We compared the performance and reliability of the different arrays, and find that the image quality increases with the number of telescopes being used. We also find that short baselines, with lengths of ~2m are needed in order to recover the large scale structure of the satellite. Some of the best results are produced by the non redundant and redundant arrays on a hexagonal grid. Considering that the satellite appearance changes with illumination, the boom array is not a good design, since it requires too much time to observe at different angles.

Iris AO has been developing dielectric-coated segmented MEMS deformable mirrors (DM) for use in laser applications that range from 355-1540 nm. In order to mitigate deformation from residual stress in the thick dielectric coatings, a stress-compensation layer has been added to the underside if the DM segments. This paper describes fabrication results of DMs with high reflectance dielectric coatings for 532 nm, 1064 nm, and 1540 nm. Additionally, a DM with a 532 nm coating has been tested with a 2 W, 532 nm CW laser. Laser testing shows the DM can handle 300 W/cm² with off-theshelf packaging. Projections show that with good heat sinking, the same DM can handle laser power densities of 2800 W/cm². The coatings showed no signs of damage after exposure to a w₀=25 μm beam with a power density of 205 kW/cm² for 105 minutes at the center of a segment and at segment edges exposed to 180 kW/cm² for 45 minutes.

The performance of Shack-Hartmann wavefront sensor (SHWFS) is mainly described by the accuracy, spatial resolution, dynamic range, and sensitivity of the measurement. These factors are particularly affected by the design of the microlens array (MLA). In order to provide a large dynamic range of wavefront measurement, most of the conventional and commercial SHWFS implemented a short focal length lenslet array, which means that the measurement sensitivity is being sacrificed and the accuracy of the wavefront sensor will be degraded. However, it is also critical to detect very small displacement of SHWFS spot in order to reconstruct it into a fine wavefront variation. We fabricated long focal length MLA with various structure arrangement by thermal reflow process with Polydimethysiloxane (PDMS) cover on the glass substrate and implemented them on the image system. A longer focal length will provide high sensitivity in determining the average slope across each lenslet under a given wavefront, and the spatial resolution of the wavefront sensor is increased by the number of lenslets across the detector. The experimental setup consists of the fabricated 245 μm diameter MLA which provides a 5.2 mm long focal distance and is paired with the CMOS as the detector. The observable smallest sensitivity is around wavelength/20 (λ=630nm).

By analysis of the mechanical equations, describing deformable mirrors, we show that the print-through is the natural property of a deformable mirror, which is completely defined by the geometry and mechanics of deformation. The print-through causes increased scattering in imaging applications, and can result in hot/cold spots in laser applications. Further development of adaptive optics for extreme UV applications would also require to address the print-through problem. We describe different ways to reduce, or completely eliminate the print-through in continuous faceplate and membrane deformable mirrors. In combination with simple hysteresis compensation, our approach allows for high-precision feedforward control of these deformable mirrors, directly in terms of Zernike modes.

This paper presents the results of a study designed to test the feasibility of imaging satellites in geostationary orbit from the ground. We argue that the instrument should be an interferometer consisting of > 30 telescopes mounted on a common, steerable boom. Light from the telescopes is fed to the beam combiner with optical fibers. The delays are equalized by steering the boom and stretching the fibers. The feed system and delay lines are replaced with single mode fibers. This system should be better throughput than the optical interferometers in use today and should be able to reach the sensitivity needed to image these targets with meter-scale telescopes. Calculations supporting this claim and a system design are presented.

Intensity interferometry, in which intensity fluctuations at separate apertures are measured and then correlated, is an attractive technique for high angular resolution measurements because of its simplicity. There is no need to transport light beams from the telescopes of the interferometer array to a beam combiner, and the telescope optics need not be precise. Michelson interferometry, in which light beams are brought together and the interference pattern is measured, is significantly more difficult, requiring precision optics and precise pathlength control, but it has a great advantage in sensitivity, requiring milliseconds to make a detection that might require hours with an intensity interferometer. However, for interferometry with a large number of array elements, the sensitivity of Michelson interferometry suffers from the fact that the light beams must be shared among many correlations, thereby reducing the sensitivity of each measurement. We explore these and other influences on the relative sensitivities of these techniques to determine under what circumstances, if any, their sensitivities become comparable.

In this paper, we present a laboratory demonstration of Fresnel telescope imaging ladar system for imaging the faraway objects with high resolution. Two concentric and coaxial quadratic wavefront with orthogonal polarization are used as scanning beams to illuminate the target. The scattered light from the target is heterodyne detected by a 90 degree 2×4 optical hybrid with two balanced receivers. The target image can be reconstructed by digital processing of the output signals of the balanced receivers. Point targets 4.3m away are reconstructed with high resolution in experiments.

There is an increasingly important requirement for day and night, wide field of view imaging and tracking for both imaging and sensing applications. Applications include military, security and remote sensing. We describe the development of a proof of concept demonstrator of an adaptive coded-aperture imager operating in the mid-wave infrared to address these requirements. This consists of a coded-aperture mask, a set of optics and a 4k x 4k focal plane array (FPA). This system can produce images with a resolution better than that achieved by the detector pixel itself (i.e. superresolution) by combining multiple frames of data recorded with different coded-aperture mask patterns. This superresolution capability has been demonstrated both in the laboratory and in imaging of real-world scenes, the highest resolution achieved being ½ the FPA pixel pitch. The resolution for this configuration is currently limited by vibration and theoretically ¼ pixel pitch should be possible. Comparisons have been made between conventional and ACAI solutions to these requirements and show significant advantages in size, weight and cost for the ACAI approach.

Interest in Adaptive Coded Aperture Imaging (ACAI) continues to grow as the optical and systems engineering community becomes increasingly aware of ACAI's potential benefits in the design and performance of both imaging and non-imaging systems , such as good angular resolution (IFOV), wide distortion-free field of view (FOV), excellent image quality, and light weight construct. In this presentation we first review the accomplishments made over the past five years, then expand on previously published work to show how replacement of conventional imaging optics with coded apertures can lead to a reduction in system size and weight. We also present a trade space analysis of key design parameters of coded apertures and review potential applications as replacement for traditional imaging optics. Results will be presented, based on last year's work of our investigation into the trade space of IFOV, resolution, effective focal length, and wavelength of incident radiation for coded aperture architectures. Finally we discuss the potential application of coded apertures for replacing objective lenses of night vision goggles (NVGs).

The requirements for a persistent wide-area surveillance system are discussed in the context of evolving military operations. Significant emphasis has been placed on the development of new sensing technologies to meet the challenges posed by asymmetric threats. Within the UK, the Electro-Magnetic Remote Sensing Defence Technology Centre (EMRS DTC) has supported the research and development of new capabilities including radio-frequency (RF) and electro-optic (EO) systems, as well as work on sensor exploitation, with a goal of developing solutions for enhancing situational awareness. This activity has been supported by field trials to determine the efficacy of competing technologies in relation to realistic threat scenarios.

Mapping of the degree of polarization improves sensitivity of imaging and ability to distinguish between polarized and partially polarized light. We developed and experimentally tested a method which is highly sensitive to a transverse distribution for the degree of light polarization. The method is based on adding several different sets of polarizing components to an imaging system, recording image set and digital processing to restore 2D maps for Stokes parameters and for the degree of polarization of the object. Results of computer simulations and optical experiments reveal that 3-5 times improvement of the contrast between polarized and partially polarized light was achieved.

We present a framework of multi-dimensional compound-eye imaging with the thin observation module by bound optics (TOMBO) and its applications. In the system, each of sub-optics equips optical coding elements to shear or to weight the multi-dimensional object information along the axial direction. The encoded information is integrated onto the detectors in the sub-optics. The object is reconstructed by a compressive sensing algorithm. The framework can be applied to various optical information acquisitions. We describe some applications of the framework including spectral imaging, polarization imaging, and so on.

We report the design of binary-amplitude masks that in conjunction with digital restoration enable mitigation of optical aberrations. Essentially, the design process aims to maintain high modulation-transfer functions by reducing destructive interference of optical-transfer-function phasors. Two optimization techniques are described: so-called contour masks and the use of multiple pixelated masks. In general the resultant modulation-transfer function is 20% of a diffractionlimited imaging system and due to the absence of nulls recorded images can be restored to a high-contrast diffractionlimited image. Example applications are presented for correcting ocular aberrations and for conformal imaging.

We consider a coded aperture imaging system which collects far fewer measurements than the underlying resolution of the scene we wish to exploit. Our sensing model considers an imaging system which subsamples pixel intensities with a SLM device. The theory of compressive imaging has been studied in the context of rebuilding high resolution imagery from a smaller set of image measurements, and thus is ideal for our application. We present a compressive imaging model to our proposed image measurement system and simulate image reconstruction performance. The compressive imaging sensing and reconstruction models are then modified to incorporate an exploitation task into the sensing and reconstruction process, the results being twofold: A more structured encoding for the measurement process, and an algorithm capable of reconstructing the processed imagery with the same computations as reconstructing the image itself. The equations are generated for an arbitrary linear filtering exploitation algorithm and we present some results based upon a quadratic correlation filtering target detection algorithm.

Traditional light field imagers do not exploit the inherent spatio-angular correlations in light field of natural scenes towards reducing the number of measurements and minimizing the spatio-angular resolution trade-off. Here we describe a compressive light field imager that utilizes the prior knowledge of sparsity/compressibility along the spatial dimension of the light field to make compressive measurements. The reconstruction performance is analyzed for three choices of measurement bases: wavelet, random, and weighted random using a simulation study. We find that the weighted random bases outperforms both the coherent wavelet basis and the incoherent random basis on a light field data set. Specifically, the simulation study shows that the weighted random basis achieves 44% to 50% lower reconstruction error compared to wavelet and random bases for a compression ratio of three.

Detection and tracking of self-luminous point sources and small targets is implemented using a single, low noise photodetector together with a programmable micromirror array. The array is programmed either to sample the scene image with a series of harmonically related stripe patterns or the array is partitioned into multiple regions modulated at several different temporal frequencies. The spatial subdivision method proves more effective at tracking slow moving, point-like targets, while the frequency based method is more effective at tracking and maintaining a spatially extended target within a track gate. The two methods have complementary features that have been combined in a hybrid algorithm, that is more effective at acquiring and maintaining track on an erratically moving object than either method individually. The tracking system concepts are introduced and an overall summary of the breadboard and simulation results are presented.

Coded aperture spectral imaging (CASSI) provides a mechanism to capture a 3D spectral cube with a single shot 2D measurement. This paper extends the concept of CASSI to a system admitting multiple shot measurements which leads not only to higher quality of reconstruction, but also to spectrally selective imaging when the sequence of code aperture patterns is optimized. The aperture code optimization problem is shown to be analogous to the optimization of a constrained, multichannel filter bank. The optimal code apertures allow the decomposition of the CASSI measurements into several matrices, each having compressive information from only a few selected spectral bands. Each matrix is reconstructed separately and the results are merged if the full data cube is needed. This technique is equivalent to a filter bank decomposition of the CASSI measurements. The approach shows better quality and higher speed of reconstruction than a non-optimized multishot CASSI system. A number of simulations are developed to illustrate the spectral imaging characteristics attained by optimal aperture codes.

This paper describes an adaptive compressive coded aperture imaging system for video based on motion-compensated video sparsity models. In particular, motion models based on optical flow and sparse deviations from optical flow (i.e. salient motion) can be used to (a) predict future video frames from previous compressive measurements, (b) perform reconstruction using efficient online convex programming techniques, and (c) adapt the coded aperture to yield higher reconstruction fidelity in the vicinity of this salient motion.

Coded aperture imaging has been used for astronomical applications for several years. Typical implementations used a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. Recently applications have emerged in the visible and infra red bands for low cost lens-less imaging systems and system studies have shown that considerable advantages in image resolution may accrue from the use of multiple different images of the same scene - requiring a reconfigurable mask. Previously reported work focused on realising such a mask to operate in the mid-IR band based on polysilicon micro-optoelectro-mechanical systems (MOEMS) technology and its integration with ASIC drive electronics using a tiled approach to scale to large format masks. The MOEMS chips employ interference effects to modulate incident light - achieved by tuning a large array of asymmetric Fabry-Perot optical cavities via an applied voltage using row/column addressing. In this paper we report on establishing the manufacturing process for such MOEMS microshutter chips in a commercial MEMS foundry, MEMSCAP - including the associated challenges in moving the technology out of the development laboratory into manufacturing. Small scale (7.3 x 7.3mm) and full size (22 x 22mm) MOEMS chips have been produced that are equivalent to those produced at QinetiQ. Optical and electrical testing has shown that these are suitable for integration into large format reconfigurable masks for coded aperture imaging applications.

An emergent electro-optic technology platform, liquid crystal (LC) waveguides, will be presented with a focus on performance attributes that may be relevant to coded aperture approaches. As a low cost and low SWaP alternative to more traditional approaches (e.g. galvos, MEMs, traditional EO techniques, etc.), LC-Waveguides provide a new technique for switching, phase shifting, steering, focusing, and generally controlling light. LC-waveguides provide tremendous continuous voltage control over optical phase delays (> 2mm demonstrated), with very low loss (< 0.5 dB/cm) and rapid response time. The electro-evanescent architecture exploits the tremendous electro-optic response of liquid crystals (can be > one million pm/Volts) while circumventing their historic limitations; speeds can be in the microseconds and LC scattering losses can be reduced by orders of magnitude from conventional LC optics. This enables a new class of photonic devices: very wide analog non-mechanical beamsteerers (270° demonstrated), chip-scale widely tunable lasers (50 nm demonstrated), chip-scale Fourier transform spectrometers (< 5 nm resolution demonstrated), widely tunable micro-ring resonators, tunable lenses (fl tuning from 5 mm to infinity demonstrated), ultra-low power (< 5 microWatts) optical switches, true optical time delay devices (12 nsecs demonstrated) for phased array antennas, and many more. Both the limitations and the opportunity provided by this technology for use in coded aperture schemes will be discussed.

This paper presents a memristor based unit cell design for a readout integrated circuit (ROIC). The memristor is a nonvolatile nanoscale circuit component that has dynamic resistance dependent on the total charge applied between the positive and negative terminals. In the circuit presented, the memristor acts as the integrator in the unit cell. This eliminates the need for a large integrating capacitor. Simulations demonstrate the functionality of the unit cell, where the memristor is accurately modeled according to previously published device characterization data. The results show that memristors can potentially be used to reduce the unit cell area, which could increase the fill factor of the photodetector in single chip detector and readout designs.

We propose tunable single-layer and multi-layer (periodic and with defect) structures comprising nanoparticle dispersed metamaterials in suitable hosts, including adaptive coded aperture constructs, for possible Adaptive Coded Aperture Imaging (ACAI) applications such as in microbolometry, pressure/temperature sensors, and directed energy transfer, over a wide frequency range, from visible to terahertz. These structures are easy to fabricate, are low-cost and tunable, and offer enhanced functionality, such as perfect absorption (in the case of bolometry) and low cross-talk (for sensors). Properties of the nanoparticle dispersed metamaterial are determined using effective medium theory.

This paper discusses the use of chalcogenide phase change materials to create tunable metamaterials as potential candidates for application to adaptive coded aperture control in the infrared. Phase change materials exhibit large and reversible changes in optical properties (Δn, Δk) when switched between the amorphous and crystalline phases. Thermally-induced phase transitions from the insulating amorphous to the conductive crystalline state can be controlled through external means, facilitating the design of reconfigurable metamaterial devices that operate with ultrafast response times. In this work, robust global stochastic optimization algorithms were combined with full-wave electromagnetic simulation tools to design periodic subwavelength chalcogenide nanostructured arrays to meet the specified device performance goals in each phase. The measured optical properties (n, k) of deposited chalcogenide thin films and nanofabrication constraints were incorporated into the optimization algorithm to guarantee that the designed nanostructures could be manufactured. By choosing the appropriate cost functions, adaptive metamaterials were designed to switch between transmissive and reflective, transmissive and absorptive, and reflective and absorptive states. These design demonstrations represent a significant step forward in the development of adaptive infrared metamaterials.