This PDF file contains the front matter associated with SPIE Proceedings Volume 8395, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We describe our Innovative Multi Aperture Gimbaless Electro-Optical (IMAGE) testbed which uses coherent detection of the complex field reflected off a diffuse target with seven hexagonally arranged apertures. The seven measured optical fields are then phased with a digital optimization algorithm to synthesize a composite image whose angular resolution exceeds that of a single aperture. This same post-detection phasing algorithm also corrects aberrations induced by imperfect optics and a turbulent atmospheric path. We present the coherent imaging sub-aperture design used in the IMAGE array as well as the design of a compact range used to perform scaled tests of the IMAGE array. We present some experimental results of imaging diffuse targets in the compact range with two phase screens which simulates a ~7[Km] propagation path through distributed atmospheric turbulence.

Developments in imaging technology for aircraft-based systems are moving in the direction of sparse, dis- tributed aperture arrays which are conformal to the shape of the air vehicle. These modular arrays can provide resolution capabilities similar to large monolithic telescope apertures without the associated weight and required aircraft structural modications. A key challenge of such a system is to accomplish the imaging function without requiring an elaborate optical relay system to bring the receive channels together on a single focal plane array (FPA). To overcome this challenge, phased array imaging systems rely on coherent imaging through holographic detection of the complex optical eld such as spatial-heterodyne imaging, which requires a digital processor to synthesize the combined imagery. This approach also allows atmospheric compensation to be included digitally in the image synthesis processing thereby eliminating any latencies due to phase modulation hardware in the subaperture module. To support testing of phased array imaging systems, we have constructed a GPU-based image processor capable of real-time (1 kHz) image synthesis including low-order atmospheric compensation. Using this processor and the IMAGE testbed at UD/LOCI, we demonstrate the eectiveness of our processor and phasing algorithm during scaled testing of a Hex-7 aperture array. We show image synthesis and compensa- tion results from laboratory testing where atmospheric turbulence eects have been induced with phase wheels at varying positions along the propagation path.

We examine a multi-aperture imaging system using a Boulder Nonlinear Systems (BNS) Spatial Light Modulator (SLM) for a wavefront control device. Such setup allows for focusing and tracking of a target over a fine angle while preserving high resolution imaging in a compact system. The SLM provides the necessary phase to focus, track and image a target. The effects of implementing a SLM on the multi aperture imaging system were investigated. The stepped phase and use of 2π resets from SLM was modeled for simulation. The result confirms the expectation that a periodic reset of the quadratic phase bowl introduces phase grating modulations, which produces "ghost images" around the desired zero order image.

This paper gives a background into aero-optics which is the effect that turbulent flow over and around an aircraft has on a laser projected or received by an optical system. The background also discusses the magnitude of the detrimental effects that aero-optics has on optical system performance and the need to measure these effects in flight. The Airborne Aero-Optics Laboratory, AAOL, fulfills this need by providing an airborne laboratory that can capture wavefronts imposed on a laser beam from a morphable optical turret; the aircraft has a Mach number range up to low transonic speeds. This paper presents the AAOL concept as well as a description of its optical components and sensing capabilities and uses.

In this paper recent in-flight aero-optical measurements on the Airborne Aero-Optics Laboratory (AAOL) will be given. Instrumentation and experimental set-up will be presented. Results of an extensive survey of the aero-optical environment at different viewing angles for both flat-window and conformal-window turrets at different subsonic and low transonic speeds, below M = 0.65, will be presented, compared and extensively discussed. The statistical analysis of wavefronts at different viewing angles will is also presented and discussed.

This paper discusses spatial-temporal characterizations of recent in- flight Airborne Aero-Optics Laboratory (AAOL) wavefront measurements at transonic speeds (Mach 0.61 - 0.65) with both flat and conformal window turrets as a function of turret look-back angle. Using both proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) analysis methods, the flow dynamics were characterized. The conformal window wavefronts showed shock formation between 85° and 90° that prematurely induced separation at a considerably lower turret look-back angle than would be expected at subsonic speeds without shock. Vortex shedding for the flat window is initiated by the leading edge of the window at a slightly lower angle than the shock-induced conformal window separation. Nevertheless, the vortex shedding dynamics of both flat and conformal window cases were found to be similar. In particular, the vortices grew in width and magnitude with increasing look-back angle. Furthermore, the corresponding shedding frequency dropped with increasing look-back angle maintaining a near constant vortex convection speed equal to about a third of the platform (free-stream) velocity. From these results a new form of the aero-optics frequency scaling relation is proposed that yields a Strouhal number independent of turret look-back angle in the vortex shedding portion of the flow.

This paper addresses a method for extracting the convection speed and direction of aberrations present in wavefronts due to aero-optical turbulence over the pupil of a turret on the side of an airborne platform. The method is applied to data from the Airborne Aero-Optics Laboratory (AAOL). Such convection information is useful in designing feed-forward adaptive-optic approaches. The method makes use of a four-beam Malley probe technique derived by constructing a two-dimensional local convective velocity-distribution over the beam's aperture. This technique is based on extending the analysis of the Notre-Dame-developed Malley probe. Two wavefront datasets (Azimuth 157° and Elevation 40°; Azimuth 42° and Elevation 43°) from the AAOL are analyzed using the derived method, the first where the laser propagates through fully-separated flow and the second where the laser propagates through an attached-flow region. Finally, the two-dimensional Proper Orthogonal Decomposition is applied to one in-flight measured dataset to determine the spatial requirements of deformable mirrors in an adaptive-optics system. The paper concludes with a discussion that points out the usefulness of the two-dimensional velocity-distributions in characterizing the various flow structures which convect over the aperture.

This paper introduces a new method for adaptive prediction and correction of wavefront errors in adaptive optics. The new method is based on receding-horizon control design and an adaptive lattice filter. Experimental results presented in the paper illustrate the capability of the new adaptive controller to predict and correct aero-optical wavefronts derived from recent flight-test data. The experimental results compare the performance of the new adaptive controller the performance of a minimum-variance adaptive controller previously used in adaptive optics. These results demonstrate the reduced sensitivity of the receding-horizon adaptive controller to high-frequency sensor noise.

Results of recent experimental measurements of aero-optical distortions caused by turbulent boundary layers at subsonic speeds M=0.4..0.6 are presented. Measurements were performed using a high-speed Shack-Hartmann sensor to collect instantaneous wavefronts with high spatial and temporal resolution, accompanied by wavefront measurements with a Malley probe. Effects of different aperture sizes on levels of aero-optical aberrations and detailed statistical analysis of spatial and temporal spectra of aero-optical distortions for both wavefront sensors are presented and discussed.

The aero-optical effects of turbulent boundary layers and separated shear layers are analyzed using the fluctuating density field obtained from large-eddy simulations. The similarities and differences in optical distortions caused by attached boundary layers and separated shear layers are discussed. The numerical database is further used to simulate Malley probe measurements and investigate its accuracy in terms of OPD_rms, correlation lengths, and the effects of aperture size and unsteady tilt removal. The use of multiple Malley probes in the transverse direction of the flow is examined to assess its capability to enhance the accuracy of measurements.

Wavefront measurements from wind tunnel or ight testing of an optical system are aected by jitter sources due to the measurement platform, system vibrations, or aero-mechanical bueting. Depending on the nature of the testing, the wavefront jitter will be a composite of several eects, one of which is the aero-optical jitter; i.e., the wavefront tilt due to random air density uctuations only. To isolate the aero-optical jitter component from recent testing, we have developed an estimation technique which uses only higher-order wavefront measurements to determine the jitter. Because these higher-order measurements are unaected by other jitter sources in the system, they can be used regardless of the additional sources of jitter in the test conguration. By analogy with work done previously with free-stream turbulence, we have developed a minimum mean-square error (MMSE) estimator using higher-order wavefront modes to compute the current-frame tilt components through a linear operation. The estimator is determined from computational uid dynamics (CFD) evaluation of aero-optical disturbances, but does not depend on the strength of such disturbances. Applying this technique to turret ight test data, we found aero-optical jitter to be 25 ± 2 μrad/m and to scale with (p/pSL)M²D_t (~ 1 μrad in the actual test cases examined.) The half-power point of the aero-optical jitter variance was found to be ~2u(see manuscript)D_t and to roll off in temporal frequency with a power law between f^-11/3 and f^-10/3.

Over the last few years, Boulder Nonlinear Systems (BNS) and North Carolina State University (NCSU) have developed a new beam steering technique that uses a stack of thin liquid crystal polarization gratings (LCPGs) to efficiently and non-mechanically steer a beam over a large field-of-regard (FOR) in discrete steps. This technology has been successfully transferred to BNS through an exclusive license agreement, and a facility has been completed to enable commercial production of these devices. This paper describes the capabilities enabled by both the LCPGs and the successful transfer of this technology.

Over the last several years, we have pioneered liquid crystal polarization gratings (PGs), in both switchable and polymer versions. We have also introduced their use in many applications, including mechanical/non-mechanical laser beam steering and polarization imaging/sensing. Until now, conventional holographic congurations were used to create PGs where the diameter of the active area was limited to 1-2 inches. In this paper, we discuss a new holography setup to fabricate large area PGs using spherical waves as the diverging coherent beams. Various design parameters of this setup are examined for impact on the quality of the recorded PG profile. Using this setup, we demonstrate a large area polymer PG with approximately 66 inch square area, and present detailed characterization.

In this paper, high frame-rate Shack Hartmann wavefront sensor with a C-MOS image sensor is presented. To realize high data rate wavefront sensor we adopted the flexible read out technique on C-MOS sensor, which makes it possible to reduce not only the amount of Hartmann spot but also image size. In the preliminary experiments, we have successfully obtained 10x10-Hartmann diagram with a rate of 4 kHz, leading to a high frame-rate wavefront sensor.

Inhomogeneity of intensity profile in techniques with illumination of SLM by laser beams leads to not efficient using of the SLM capabilities or complexity of algorithms to control these SLM. For example the typical Gaussian intensity distribution has peak intensity in the centre of a beam, and to prevent damaging the SLM it is necessary to reduce power of entire laser beam. In laser techniques like Computer Generated Holography (CGH) the not uniform intensity profile leads to essential increasing the complexity of mathematical models or makes some techniques of digital holography unrealizable. To overcome these drawbacks it is suggested to apply with SLM the refractive field mapping beam shapers providing high flexibility in building various optical setups due to their unique features: almost lossless intensity profile transformation from Gaussian to flattop, saving of the beam consistency, low output beam divergence and flatness of wavefront, extended depth of field, capability to adapt to real intensity profiles of TEM00 and multimode laser sources. Applications include CGH, holographic projection processing applications, holographic lithography, optical trapping and laser illumination in confocal microscopes. With a collimated flattop beam provided by refractive field mappers these techniques become easier to use, more effective and reliable in operation. This paper will describe some design basics of refractive beam shapers of the field mapping type, with emphasis on the features important for applications with SLMs. There will be presented comparative results of applying the refractive beam shapers in systems of holographic lithography and other techniques.

Position transducers are common but critical elements in defence, aerospace, security and surveillance equipment. Traditional solutions such as potentiometers, optical encoders and inductive detectors, struggle to match the high operational, environmental and lifetime requirements demanded by such equipment. This paper outlines a radically new approach to position measurement suitable for a wide variety of shapes and sizes including rotary, linear, 2D and 3D geometries. The technology's main components are arrays of printed conductors on thin, lightweight flexible substrates. The result is a non-contact, absolute measurement technique which offers high reliability, accuracy and robust operation in a compact, non-ITAR and lightweight form.

Line-of-sight stabilized system, which can be used to isolate the vibration of the moving bed and the disturbance of environment, is the most important part of an electro-optical tracking system. The steady precision and robustness are the key issues of recent researches. In this paper, a novel control approach so called 2-Port Internal Model Control (2-PIMC) for line-of-sight stabilized system is proposed. By adding a parallel feedback control loop on the basis of Internal Model Control (IMC), the 2-PIMC method can improve precision while it also has strong robustness as the IMC. The robustness and the static error of 2-PIMC method were subsequently analyzed. Based on this novel method, Simulation and experiment are both carried out for a gyro stabilized platform of electro-optical tracking system. The experiments include a shaking table which can generate disturbance as the moving bed and a gyro stabilized platform which is mounted on the shaking table. The experimental result indicated that the gyro stabilized platform using 2-PIMC method is accurate and effective. Comparing with PI control, the following error and disturbance restraining error were both greatly improved at low-frequency and mid-frequency by the 2-PIMC method proposed. The improvement of precision is more than 10dB at 4Hz. In addition, the 2-PIMC method doesn't need any extra sensors for the platform and it's easy for parameters regulation. It can be concluded that the2-PIMC method is a new approach for the high-performance gyro stabilized platform and might have broad application prospect.

Object detection and tracking using computer vision (CV) techniques have been widely applied to sensor fusion applications. Many papers continue to be written that speed up performance and increase learning of artificially intelligent systems through improved algorithms, workload distribution, and information fusion. Military application of real-time tracking systems is becoming more and more complex with an ever increasing need of fusion and CV techniques to actively track and control dynamic systems. Examples include the use of metrology systems for tracking and measuring micro air vehicles (MAVs) and autonomous navigation systems for controlling MAVs. This paper seeks to contribute to the determination of select tracking algorithms that best track a moving object using a pan/tilt/zoom (PTZ) camera applicable to both of the examples presented. The select feature generation algorithms compared in this paper are the trained Scale-Invariant Feature Transform (SIFT) and Speeded Up Robust Features (SURF), the Mixture of Gaussians (MoG) background subtraction method, the Lucas- Kanade optical flow method (2000) and the Farneback optical flow method (2003). The matching algorithm used in this paper for the trained feature generation algorithms is the Fast Library for Approximate Nearest Neighbors (FLANN). The BSD licensed OpenCV library is used extensively to demonstrate the viability of each algorithm and its performance. Initial testing is performed on a sequence of images using a stationary camera. Further testing is performed on a sequence of images such that the PTZ camera is moving in order to capture the moving object. Comparisons are made based upon accuracy, speed and memory.

This paper discusses the design and development of an autonomous intelligent modular surveillance system (AIM2S). The system represents a novel class of "smart" surveillance platforms that integrates multiple sensors on an open-bus chassis. AIM2S modular architecture allows plug & play system operation, enabling its performance as a standalone unit or in conjunction with other systems. The integration of multiple smart sensors facilitates the affective fusion of heterogeneous data sources to obtain previously unavailable state information.

Kalman filters have been used as a robust method for object location prediction in various tracking algorithms for nearly a decade. More recently, adaptive and extended Kalman filters have been employed, making predictions even more reliable. The presented addition to this trend is the employment of a polynomial fit to the history of object locations, using the adaptive Kalman filter framework. This allows the linear state model of the adaptive Kalman filter to predict non-linear motion, making tracking more robust. This modified filter will be used in conjunction with the Mean Shift algorithm as the measurement step. Another important consideration when using a Kalman filter in this manner will be which correlation coefficient is used. The Pearson product-moment correlation coefficient is shown to provide more robust tracking when compared to the Bhattacharyya coefficient when objects have either low resolution or are unresolved.