This PDF file contains the front matter associated with SPIE Proceedings Volume 6714, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Many of the more challenging goals set for future defence systems require a paradigm shift in imaging technology. Processes of bio-inspiration can inform the evolution of new imaging systems, especially those that exploit the benefits of computational imaging. Modern computing power shifts the emphasis away from costly highly engineered optical assemblies to lightweight systems exploiting algorithmic image reconstruction techniques. Yet some spiders are able to process several optical fields of different angular dimensions at the same time, which is a pre-requisite when organisms sense their environments using compound eye architectures. Some of the benefits of exploiting the parallels existing between evolutionary processes in biology and optical engineering are highlighted.

The Defense Advanced Research Projects Agency (DARPA) is in a unique position to question traditional sensing architectures and concepts while possessing both the charter and funding to explore and develop the technologies necessary to accomplish both existing and desired applications. This paper describes the logical flow from the need for long-term tracking of an extremely large number of vehicles in an urban environment, through the fundamental requirements and the application to the phenomenology tradespace.

Originally developed more than four decades ago for imaging non-refracting radiation such as x-rays, gamma-rays, and neutrons, today coded apertures are poised for new applications in other domains of the electro-magnetic spectrum. Boasting excellent angular resolution, wide field-of-view, negligible image distortion, and light weight construction, coded apertures are increasingly attractive for certain IR and optical applications. Successful exploitation of the coded aperture technique to these new venues will require the systems engineer or designer to understand the fundamental principles of imaging with coded apertures. This presentation explores the special properties of coded aperture masks, the algorithms used to design them, the signal processing algorithms used to decode recorded data, as well as important design considerations for a successful system. The targeted audience is the engineer with minimal prior working knowledge of coded apertures who wants to understand the technology sufficiently well to reliably assess applicability for present and future needs.

The use of staring infrared imaging systems provides significant advantages for military missions such as single sensor day/night persistent tactical surveillance of all moving vehicles in a large urban battlefield. Monitoring of very wide instantaneous field-of-regard with the capability to allocate parts or all of the video-channel bandwidth for high-resolution imaging of a narrow field of view allows identifying and tracking targets from long standoff distances. This capability has been successfully demonstrated in the Agile, Detecting and Discriminating, Infrared Electro-Optical System (ADDIOS) developed by Applied Science Innovations, Inc. in collaboration with the Air Force Research Laboratory (AFRL). The system features electronically switchable resolution achieved with digital processing gain, which replaced optical or opto-mechanical gain typical of conventional cameras. The output of the system has an order of magnitude higher resolution compared to pixel-limited resolution of the imaging sensor alone. This capability, demonstrated in the working ADDIOS prototype, is universally applicable for boosting resolution of "pixel-hungry" imagers where available pixel counts fall short of desired, e.g., due to technology limitations of high costs. The ADDIOS modular design makes the flexible-resolution imaging core equally applicable to cameras with conventional lenses, coded aperture systems, and potentially other technologies such as holography and optical metrology. The system features millisecond switching speed and low power consumption, combined with reasonable cost, small mass, and compact form factor applicable to retrofitting existing imaging systems. With the experimental prototype already demonstrated in the visible and near-infrared, the spectral range can be expanded into mid-wave and potentially long-wave infrared ranges. The paper summarizes the results of the ADDIOS technology development and addresses their application to DARPA's Large Area Coverage Optical Search-while-Track and Engage (LACOSTE) program, including coded aperture imaging.

The process of optical imaging and the use of a glass lens have been hitherto inseparable since it is the lens that is responsible for mapping incoming rays to form an image. While performing this critical role, the lens, by virtue of its geometry and materials composition, presents constraints on the size, weight, angular field of view, and environmental stability of an optical imaging system as a whole. Here, a new approach to optical imaging is presented. Tough polymeric light-sensing fibers are suspended on a frame to form large-scale, low-density, two- and three-dimensional photonic meshgrids. While a single grid can indeed locate a point of illumination, it is the stacking of a multiplicity of such grids, afforded by their essential transparency, which allows for the detection of the direction of illumination with a wide angular field of view. A surface-spanning-arrangement of such fibers is used to extract an arbitrary optical intensity distribution in a plane using a tomographic algorithm. Lensless imaging is achieved by a volumetric fiber assembly that extracts both the phase and intensity distributions of an incoming electromagnetic field, enabling one to readily determine the object from which the field originally emanated.

Previous applications of coded aperture imaging (CAI) have been mainly in the energetic parts of the electro-magnetic spectrum, such as gamma ray astronomy, where few viable imaging alternatives exist. In addition, resolution requirements have typically been low (~ mrad). This paper investigates the prospects for and advantages of using CAI at longer wavelengths (visible, infrared) and at higher resolutions, and also considers the benefits of adaptive CAI techniques. The latter enable CAI to achieve reconfigurable modes of imaging, as well as improving system performance in other ways, such as enhanced image quality. It is shown that adaptive CAI has several potential advantages over more traditional optical systems for some applications in these wavebands. The merits include low mass, volume and moments of inertia, potentially lower costs, graceful failure modes, steerable fields of regard with no macroscopic moving parts and inherently encrypted data streams. Among the challenges associated with this new imaging approach are the effects of diffraction, interference, photon absorption at the mask and the low scene contrasts in the infrared wavebands. The paper analyzes some of these and presents the results of some of the tradeoffs in optical performance, using radiometric calculations to illustrate the consequences in a mid-infrared application. A CAI system requires a decoding algorithm in order to form an image and the paper discusses novel approaches, tailored to longer wavelength operation. The paper concludes by presenting initial experimental results.

Gimbals have been the main mechanism to perform pointing and beam steering for most Electro-optic sensors. A new class of pointing and beam steering devices based on a pair of counter-rotating Grisms is presented here. The device is capable of wide spectral band. The paper first describes the design principles of counter-rotating Grisms for beam pointing and beam steering. Comparison between gimbals and counter-rotating prisms is given next. Finally potential applications of a pair of counter-rotating grisms are illustrated.

Recent theoretical work in "compressed sensing" can be exploited to guide the design of accurate, single-snapshot, static, high-throughput spectral imaging systems. A spectral imager provides a three-dimensional data cube in which the spatial information of the image is complemented by spectral information about each spatial location. In this paper, compressive, single-snapshot spectral imaging is accomplished via a novel static design consisting of a coded input aperture, a single dispersive element and a detector. The proposed "single disperser" design described here mixes spatial and spectral information on the detector by measuring coded projections of the spectral datacube that are induced by the coded input aperture. The single disperser uses fewer optical elements and requires simpler optical alignment than our dual disperser design. We discuss the prototype instrument, the reconstruction algorithm used to generate accurate estimates of the spectral datacubes, and associated experimental results.

Coded aperture imaging has been used for astronomical applications for several years. Typical implementations use a fixed mask pattern and are designed to operate in the X-Ray or gamma ray bands. More recent applications have emerged in the visible and infra red bands for low cost lens-less imaging systems. 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. We report on work to develop a novel, reconfigurable mask based on micro-opto-electro-mechanical systems (MOEMS) technology employing interference effects to modulate incident light in the mid-IR band (3-5μm). This is achieved by tuning a large array of asymmetric Fabry-Perot cavities by applying an electrostatic force to adjust the gap between a moveable upper polysilicon mirror plate supported on suspensions and underlying fixed (electrode) layers on a silicon substrate. A key advantage of the modulator technology developed is that it is transmissive and high speed (e.g. 100kHz) - allowing simpler imaging system configurations. It is also realised using a modified standard polysilicon surface micromachining process (i.e. MUMPS-like) that is widely available and hence should have a low production cost in volume. We have developed designs capable of operating across the entire mid-IR band with peak transmissions approaching 100% and high contrast. By using a pixelated array of small mirrors, a large area device comprising individually addressable elements may be realised that allows reconfiguring of the whole mask at speeds in excess of video frame rates.

Extension of coded apertures to the MWIR introduces the effects of diffraction and other distortions not observed in shorter wavelength systems. A new approach is being developed under the DARPA/SPO funded LACOSTE (Large Area Coverage Optical search-while Track and Engage) program, that addresses the effects of diffraction while gaining the benefits of coded apertures, thus providing flexibility to vary resolution, possess sufficient light gathering power, and achieve a wide field of view (WFOV). The photonic MEMS "eyelid" array technology is currently being instantiated in this DARPA Surveillance program study as the "heart", mediating the flow of the incoming signal. However, speed, lifetime, packaging and scalability are critical factors for the MEMS "eyelid" technology which will determine system efficacy as well as military and commercial usefulness. The electronic eyelid array is the fundamental addressable unit for adaptive code generation and will allow the system to multiplex in time for increased resolution. The binary code which determines whether a 500μm eyelid is open or closed is referred to as the "eyelid code." Groups of eyelids can work together as a "super aperture" by virtue of a "macro-code." A macro code becomes relevant to describe how dispersed eyelids across the 0.19m x 0.19m aperture will function together. Dynamic aperture arrays were fabricated on both quartz and sapphire substrates for operation in the visible to MWIR. Both 8x8 and 40x40 element arrays were designed, fabricated, and tested with macro-codes consisting of 4, 8, and 16 unique combinations. The die were packaged and tested in ambient for robust eyelid operations. The point spread function was also measured in an optical setup with the eyelid arrays located in the aperture plane.

Adaptive coded aperture sensing is an emerging technology enabling real time, wide-area IR/visible sensing and imaging. Exploiting unique imaging architectures, adaptive coded aperture sensors achieve wide field of view, near-instantaneous optical path repositioning, and high resolution while reducing weight, power consumption and cost of air- and space born sensors. Such sensors may be used for military, civilian, or commercial applications in all optical bands but there is special interest in diffraction imaging sensors for IR applications. Extension of coded apertures from Visible to the MWIR introduces the effects of diffraction and other distortions not observed in shorter wavelength systems. A new approach is being developed under the DARPA/SPO funded LACOSTE (Large Area Coverage Optical search-while Track and Engage) program, that addresses the effects of diffraction while gaining the benefits of coded apertures, thus providing flexibility to vary resolution, possess sufficient light gathering power, and achieve a wide field of view (WFOV). The photonic MEMS-Eyelid "sub-aperture" array technology is currently being instantiated in this DARPA program to be the heart of conducting the flow (heartbeat) of the incoming signal. However, packaging and scalability are critical factors for the MEMS "sub-aperture" technology which will determine system efficacy as well as military and commercial usefulness. As larger arrays with 1,000,000+ sub-apertures are produced for this LACOSTE effort, the available Degrees of Freedom (DOF) will enable better spatial resolution, control and refinement on the coding for the system. Studies (SNR simulations) will be performed (based on the Adaptive Coded Aperture algorithm implementation) to determine the efficacy of this diffractive MEMS approach and to determine the available system budget based on simulated bi-static shutter-element DOF degradation (1%, 5%, 10%, 20%, etc..) trials until the degradation level where it is perceived to necessitate component replacement. System performance impacts, from DOF degradation, will manifest in a spatially random method.

Eclipse SteerTech^TM transmissive fluid state electrowetting technology has successfully demonstrated the ability to control the shape and position of a fluid lenslet. In its final form, the technology will incorporate a dual fluid lenslet approach capable of operating in extremely high acceleration environments. The beam steering system works on the principle of electro-wetting. A substrate is covered with a closely spaced array of, independently addressable, transparent, electrically conductive pixels utilizing Eclipse's proprietary EclipseTEC^TM technology. By activating and deactivating selected EclipseTEC^TM pixels in the proper sequence, the shape and position of fluid lenslets or arrays of lenslets can be dynamically changed at will. The position and shape of individual fluid lenslets may be accurately controlled on any flat, simply curved, or complex curved, transparent or reflective surface. The smaller the pixels the better control of the position and shape of the fluid lenslets. Information on the successful testing of the Eclipse SteerTech^TM lenslet and discussion of its use in a de-centered lenslet array will be presented.

Diffractive optical systems in the Infrared (IR) wavelength regime are being re-examined for remote sensing applications. A pupil-plane adaptive coded aperture can enable a fine resolution, wide field of view sensor system without mechanical scanning. Due to the relatively long wavelengths, coded aperture systems in the IR have unique issues in regards to e.g. X-ray coded apertures. These include diffraction effects, wavelength dependence of optical elements, off axis aberrations due to thick screens, etc. In this paper, we provide a general system model framework based on partial coherence theory that enables us to explore many of the technical challenges in IR diffractive imaging. This paper develops the general theory and shows examples of issues that impact the optical transfer function (OTF) and impulse response of these types of architectures.

New advances in Liquid Crystal Spatial Light Modulators (LCSLM) offer opportunities for large adaptive optics in the midwave infrared spectrum. A light focusing adaptive imaging system, using the zero-order diffraction state of a polarizer-free liquid crystal polarization grating modulator to create millions of high transmittance apertures, is envisioned in a system called DAZLE (Discrete Adaptive Zone Light Elements). DAZLE adaptively selects large sets of LCSLM apertures using the principles of coded masks, embodied in a hybrid Discrete Fresnel Zone Plate (DFZP) design. Issues of system architecture, including factors of LCSLM aperture pattern and adaptive control, image resolution and focal plane array (FPA) matching, and trade-offs between filter bandwidths, background photon noise, and chromatic aberration are discussed.

An optical system consisting of an aqueous electrolyte resting on a polymer/gold/indium-tin-oxide (ITO) layer deposited onto a glass substrate is analyzed to acquire contact angle - focal distance data as a function of applied voltage. The shape factor of a liquid lens and its dependence on the perimeter of contact line and contact angle was analyzed in the presence of an electrical field applied between the electrolyte and planar electrode system. The contact angle of a liquid on a thin, transparent film of gold (20 nm thick) - on ITO under electrolyte solution could be varied from 110 ± 3° when the gold was held at -2.4 V to 41 ± 3° without voltage. The behavior of a water-based electrolyte and water-soluble polymer blend and its influence on the shape of contact line and profile of the lens were investigated by employing a holographic setup at wavelengths of 632.8 and 543.5 nm. Optical micrographs showing the profile of the lens, aberration-less aperture, deformation of contact line, and shape of the liquid lens, respectively, were analyzed in reflection and transmission. Both the advancing and receding contact angles were measured directly from digitized images of the profile of the lens. The dynamic range of linear beam steering and dependence of the focal length of the liquid lens on the applied voltage are discussed.