Distributed Test Capability Using Infrared Scene Projector Technology

SBIR has passed the midpoint of delivering ten 1024x1024 IR Scene Projector Systems (IRSPs) to the Government. Six systems have been installed at Redstone Technical Test Center (RTTC), Patuxent River, and Edwards Air Force Base. Four more systems are in production and will be shipped by the end of this year. The commercial name of the LFRA IRSP is Mirage XL. This ground breaking projector technology is being leveraged on the Wide Format Resistive Array (WFRA) program and on the Mirage II product. The WFRA IRSP, also known as Mirage HD, features an even larger 1536x768 emitter array and will be in system integration by the end of the year. Mirage II, which also leverages LFRA, is being readied as the next generation 512x512 projector system. Additional signal processing capabilities have been installed in the LFRA systems. Each system now has full Translation/Rotation Processing (TRP) capability. Systems also have image convolution and 400Hz 1024x512 windowing capabilities.

The importance of hard-ware-in-the-loop infrared seekers testing with realistic infrared scenes warrants a review of the current technologies used in dynamic infrared scene simulation. Infrared seeker dynamic scene simulation technology includes dynamic infrared simulator technology and infrared scene image generation technology. Infrared simulator includes resistor arrays, liquid crystal light valves, laser writers, laser diode arrays, CRT and digital mirror devices (DMD). The technology that may provide high performance for testing seekers is the DMD approach. Other technologies such as resistor arrays, LCLVs, laser diodes, and the CRTs are still under development. Infrared scene generation can be divided into the stage of data generation and the stage of programming. Target 3D model is completed by the software of Multigen Creator and dynamic scene image generation is completed by the software of Vega. The SensorVision module of Vega can supply the atmosphere model parameter and target texture material.

The inherent non-uniformity of a Wideband Infrared Scene Projector (WISP) necessitates an analytical prediction of the contribution of the scene projector's non-uniformity to a test article's output image non-uniformity. A mathematical model has been developed to calculate this non-uniformity based upon a number of input parameters. The output image non-uniformity is dependent on both the non-uniformity of the scene projector and the test article, as well as a weighting factor that results from the relative contribution of the different emitters to the individual detector elements. It is through this weighting factor that parameters such as the sampling ratio, the optical blur of the emitters on the detector' focal plane array, the fill factor of the detector array, and the alignment of the emitters with respect to the detector elements affect the non-uniformity of the output image. Using this model, a theoretical limit for the maximum output image non-uniformity can be calculated for particular values of the scene projector's non-uniformity and the test article's non- uniformity. Realistic situations likely to be encountered during simulation testing were all found to be below the maximum. In order to make this model a useful tool for the laboratory environment, a computer program has been written that calculates the output image non-uniformity based on a given set of input parameters and a numerical approximation of the weighting factor.

Raytheon Visions Systems (RVS) is furthering its capability to deliver state-of-the-art high performance large format HgCdTe focal plane arrays (FPAs) for dual-band long-wavelength infrared (LWIR) detection. Missile seekers are designed to acquire targets of interest at long ranges and discriminate targets from clutter. The use of dual-band long wavelength infrared detector technology provides the ability for these seekers to combine these operations into the same package with enhanced performance. Increasing the format size of dual-band longwavelength FPAs and tailoring the detector design for specific long-wavelength bands enables seekers to be designed for increased field-of-view, longer target acquisition ranges, and improved accuracy. This paper will review in further detail the aspects of detector design, MBE wafer growth, wafer fabrication, and detector characterization that are contributing to development and demonstration of high performance large format dual-band LWIR FPAs at RVS.

Texas Instruments has developed a new thermal imaging technology based upon focal plane arrays (FPAs) using the pyroelectric effect in ceramic barium-strontium titanate (BST). These devices operate near the paraelectric-ferroelectric phase transition, which, for the selected composition of BST, is near room temperature. The detector elements operate in the voltage mode with a bias voltage applied to maintain and optimize the pyroelectric effect near the phase transition. The BST array attaches via bump-bonding to a CMOS readout circuit that filters, buffers and multiplexes the output signals. These FPAs have facilitated the development of a system technology capable of satisfying a wide variety of applications, including surveillance devices, weapons sights, missile seekers and driver's aids. Resulting systems are performance-competitive with scanned FLIRs in these applications, and they are smaller in size, lighter in weight, and require less power than scanned FLIRs. Simplicity and compactness of the system designs will result in production costs competitive with image intensification devices.

A few years ago, a microlithographic deposition process on infrared-transmitting substrates was developed in order to produce realistic infrared scenes for FLIR testing. In recent months, the performance of this product, named Thermoscene, has been improved by improving the control over the production process. The two main results are: (1) An increase in the number of simulated grey levels from 15 to 290, without reduction of the total number of pixels. (2) A decrease in imperfections, such as unwanted holes in the mesh deposition, to almost zero. The Thermoscene is useful as a component of infrared simulators, to project realistic infrared scenes through collimating optics to a FLIR, missile seeker, etc., for testing purposes.

Infrared sensing technology has come a long way since Hershel made the unexpected discovery in 1800 that radiation at wavelengths beyond the visible spectrum were measurable by his rudimentary bolometer instrument. The tremendous advancements in this technology have been propelled heavily through defense research and development, aimed at providing important night vision and target detection capabilities for surveillance, reconnaissance, targeting, and threat warning systems. The maturation of the underlying infrared sensing technology, specifically infrared optics and focal plane arrays, has not only enhanced the system capabilities for these missions, but has also resulted in the proliferation of infrared systems into a more diverse set of air, land, sea, and space-based platforms. Furthermore, infrared sensing has become more affordable through the advent of uncooled and high-operating-temperature focal plane arrays, which has opened up civilian and commercial applications such as thermography, law enforcement, fire and security, weather monitoring, transportation, and spectroscopy.

This paper describes a simulation and analysis of a sensor viewing a 'pixelized' scene projector like the KHILS' Wideband Infrared Scene Projector (WISP). The main objective of this effort is to understand and quantify the effects of different scene projector configurations on the performance of several sensor signal processing algorithms. We present simulation results that quantify the performance of two signal processing algorithms used to estimate the sub-pixel position and irradiance of a point source. The algorithms are characterized for different signal-to-noise ratios, different projector configurations, and two different methods for preparing images that drive the projector. We describe the simulation in detail, numerous results obtained by processing simulated images, algorithms and projector properties, and present conclusions.

This paper reviews some of the technologies associated with evolutionary improvements in imaging infrared seeker designs and predicts technology performance into the future. The impact of technology advances is shown for several components of the missile system, including: dome, optics, motion stabilization, focal plane arrays, analog-to-digital conversions, and computer processing speed.

SCD has developed a series of Infra Red (IR) detectors based on the well established technologies of InSb diodes and the most advanced analogue and digital signal processors. These detectors exhibit great advantages for Missile Warning System (MWS). Their special modes of operation combined with a high level of performance enable efficient optimization for MWS applications. These high-end applications require special features including large dynamic range, high frame rate, high sensitivity at low signal and dual-color detection. The first detector that was developed for MWS applications is the "Blue Fairy" detector which has 320x256 elements. After the "Blue Fairy" a new generation of digital detectors was developed, starting with "Sebastian". Sebastian is based on a novel digital Focal Plane Processor (FPP) with formats of 640×512 and 480×384 elements. A detector based on two Sebastian Focal Plane Arrays (FPAs) assembled on a single substrate with a high degree of registration provides a good dual-color solution for MWS systems. In this paper the special features and the performance of all these detectors are presented showing their advantages for MWS applications.

The Naval Weapons Center (NWC) is currently developing automatic target classification systems for future surveillance and attack aircraft and missile seekers. Target classification has been identified as a critical operational capability which should be included on new Navy aircraft and missile developments or systems undergoing significant modifications. The objective for the Automatic Classification Infrared Ship Imagery System is to provide the following new capablities for surveillance and attack aircraft and antiship missiles: near real-time automatic classification of ships in day and night at long standoff ranges with a wide area coverage imaging infrared sensor. The sensor applies classical pattern recognition technology to automatically classify ships using Forward Looking Infrared (FLIR) images. Automatic Classification of Infrared Ship Imagery is based on the extraction of features which uniquely describe the classes of ships. These features are used in conjunction with decision rules which are established during a training phase. Conventional classification techniques require labeled samples of all expected targets, threats and non-threats for this training phase. To overcome the resulting need for the collection of an immense data base, NWC developed a Generalized Classifier which, in the training phase, requires signals only from the targets of interest, such as high value combatant threats. In the testing phase, the signals from the combatants are classified and signals from other ships, which are sufficiently different from the training data, are classified as "other" targets. This technique provides a considerable savings in computer processing time, in memory requirements and data collection efforts. Since sufficient IIR images of the appropriate quality and quantity were not available for investigating automatic IIR ship classification, TV images of ship models were used for an initial feasibility demonstration. The initial investigation made use of the experience gained with preprocessing and classifying ROR and ISAR data. For this reason, the most expedient method was to collapse the 2-dimensional TV ship images onto the longitudinal axis by summing the amplitude data in the vertical ship axis. The resulting 128 point 1-dimensional profiles show the silhouette of the ship and bear an obvious similarity with the radar data. Based on that observation, a 128 point Fourier transform was computed and the ten low order squared amplitudes of the complex Fourier coefficients were then used as feature vectors for the Generalized Classifier. In contrast to the radar data, the size of TV or IIR images of ships changes as a function of range. It is therefore necessary to develop feature extraction algorithms which are scale invariant. The central moments, which have scale and rotational invariant properties were therefore implemented. This method was suggested in 1962 by M. K. Hu (IRE Transactions on Information Theory). Using the moments alone resulted in unsatisfactory classification performance and indicated that edge enhancement was necessary and that the background needed to be rejected. The images were therefore processed with the Sobel nonlinear edge enhancement algorithm, which also has the desirable property that it works for images with low signal-to-noise ratios and poorly defined edges. Satisfactory results were obtained. In another experiment, the feature vector was composed of the five lower-order invariant moments and the five lower-order FFT coefficient squared magnitudes, excluding the zero frequency coefficient. This paper will describe the data base, the processing and classification techniques, discuss the results and addresses the topic of "Processing of Images and Data Optical Sensors."

A Scophony Infrared Scene Projector (IRSP) is being used at Wright Laboratories Armament Directorate, Guided Interceptor Technology Branch, Eglin AFB, to evaluate thermal-imaging guidance systems. This hardware-in-the-loop testing system reduces the number of necessary field trials and has potential for in-laboratory simulation where the performance of entire seeker systems can be analyzed. The performance of an optical system, in terms of such characteristics as wavefront error, resolution, and transfer factor, can be measured with knowledge of the system MTF and PSF performance. A slow-scan calibration system was used to measure an image plane of the IRSP under three separate configurations of the system. MTFs and PSFs were derived for the IRSP without the use of the scatter screen, with the scatter screen in place, and with the scatter screen rotating.

Infrared detectors and imaging arrays operating at wavelengths in the 8-12 µm atmospheric windows have attracted considerable interest because of their wide range of applications in areas such as infrared missile seeker-tracer systems, space surveillance, and medical imaging. Among the proposed III-V photodetectors, the most dramatic progress have been made by AlGaAs/GaAs multiquantum well detectors. Focal plane arrays and discrete detectors have already been demonstrated using this material system. The chapter presents the physical properties of this new InTlSb alloy and the advancements made towards realizing InTlSb infrared photodetectors. For the growths of InSb and InTlSb, both InSb and semi-insulating GaAs substrates were used. In order to investigate the physical properties of as-grown films, a number of structural, electrical, and optical characterizations were carried out on a routine basis. The band structure of InTlSb have been investigated by M. van Schilfgaarde et al. based on various material parameters of its binary constituents, InSb and TISb.

T HE development of aircraft guidance, navigation, and control systems has been a long-standing research area. Numerous methods relating to the enhancement of aircraft performance under various mission parameters have been developed in response to a need for more reliable and robust guidance systems. Current guidance systems applied to commercial, civilian, and unmanned aircraft rely on the knowledge of a flight path, specified bywaypoints located in inertial space. Most missions are considered successful when the vehicle reaches the designatedwaypoint at which new commands are issued to the vehicle to proceed to the next waypoint. Two common types of conventional aircraft guidance are the direct-to-waypoint (DTW) and track-to-waypoint (TTW) methods in relation to pathfollowing between designated waypoints. The DTWmethod simply issues heading commands to the vehicle based on the angular difference between thewaypoint and vehicle.When thevehicle reaches the waypoint, the control system issues a new command to guide the aircraft to the next waypoint. The TTW method aims to follow the track betweenwaypoints. In this guidancemethod the control system aims to minimize the lateral offset between the prescribed flight path and the aircraft’s position, issuing heading commands that return the vehicle to the nominal flight path. The track method therefore places the additional constraint on a flight path that the vehicle must follow in order to reach the waypoint, rather than simply reaching the waypoint. However, both methods are far from optimal. This is evident in how the aircraft transitions between flight paths after reaching awaypoint. During theseflight-path transitions, the aircraft will often overshoot the desiredflight path to correct its track, particularlywhen the flight-path transition angle is acute. Various control strategies have been investigated to alleviate or minimize flight-path deviations. Such strategies include applyingmodern control methods such as receding-horizon control [1,2] and model predictive control [3] to anticipate flight-path changes and take control action before reaching a goal while maintaining adequate vehicle flight performance. Missile guidance and control systems operate on similar principles to commercial, civilian, and unmanned aircraft guidance and control algorithms. The primary mission for missile systems is to intercept a moving target using information about the relative position and velocity between the pursuer and target. One of thefirstmethods used in missile guidance was pursuit guidance (PG) [4–7]. The method operates by forcing the angular displacement error between a pursuer and its target to zero. Control commands scaled by a proportional factor of the current error are then issued to direct the pursuer along the line of sight (LOS) between the pursuer and target. PG solutions, however, do not consider the path taken or the levels of system performance required by the pursuer in reaching the target, resulting in a far-from-optimal solution. To address this problem of suboptimality, additional parameters have been introduced to enhance missile performance. One method includes taking into account the motion of the commanded line of sight between the pursuer and target [4,7–10], issuing lateral acceleration commands based on tracking error and tracking error rate to the target. This approach has been shown to improve overall interceptor performance compared with conventional PG [4,7]. Another suchmethod aims tomodify the level of control the guidance algorithm possesses over the vehicle by adjusting the level of proportional gain. This is achieved by gain scheduling [11] to select gain values based on current interceptor states. In addition to modifying internal missile guidance and control parameters such as variable gains and LOS rate estimation, mission performance can be enhanced by manipulating the trajectory taken by the pursuer to the targets. A good example of such a method is discussed in [12], in which a missile aims to exploit the aerodynamic benefits of high-altitude flight by tracking a virtual target at some initially high altitude that is not necessarily along the trajectory to the true target. This Note discusses the development of a guidance law fusing the virtual-target concepts with those of pursuit guidance for implementation into an aircraft guidance system. This Note develops a path-following aircraft guidance algorithm that pursues synthetic waypoints using only a small set of guidance parameters, extending the virtual-target concept to complete aircraft guidance. The path is defined by the track between a minimal set of waypoints at specified locations, removing the need for a smooth path to be defined or the need for complicated path-switching logic or trajectory planning when awaypoint is reached. The synthetic waypoint travels along the path between waypoints, with the trailing aircraft traveling a smooth path generated through its own dynamics in following the synthetic waypoint. The guidance law is tested by varying guidance parameters, thus assessing vehicle sensitivity to and overall system performance of parameter variations. The following sections discuss the basic concepts of missile and aircraft guidance and provide a detailed description of the structure of the synthetic-waypoint guidance algorithm. A discussion on the implementation of the algorithm into the underlying aircraft control system will also be presented, followed by an analysis of the performance of the guidance algorithm in nonlinear simulation. Received 30 June 2009; revision received 3 November 2009; accepted for publication 9November 2009.Copyright©2009 by theAmerican Institute of Aeronautics and Astronautics, Inc. All rights reserved. Copies of this paper may be made for personal or internal use, on condition that the copier pay the $10.00 per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923; include the code 0731-5090/10 and $10.00 in correspondence with the CCC. ∗Graduate Research Student, School of Aerospace, Mechanical and Mechatronic Engineering; e.medagoda@aeromech.usyd.edu.au. Senior Lecturer, School of Aerospace, Mechanical and Mechatronic Engineering; pwg@aeromech.usyd.edu.au. JOURNAL OF GUIDANCE, CONTROL, AND DYNAMICS Vol. 33, No. 2, March–April 2010

The aim of the work described in this paper, is to generate realistic infra-red (IR) images of sea clutter including sun glint, suitable for the testing of image analysis and detection algorithms. The accuracy of detection algorithms can only be determined by using a wide variety of test data representing different scene parameters such as sea state, sun angles and camera position. This type of data is extremely costly and difficult to obtain in practical trials. Synthetic generation of such scenes offers the capability to generate suitable data sets at a fraction of the cost, whilst offering precise control over the scene parameters. A model suitable for the generation of such data is developed and some results of synthetic IR scenes are presented. The model presented in this paper consists of three parts, namely: 1. The generation of the sea surface, including: animation of the wave motion. 2. The computer graphics required for the viewing of the scene. 3. The computation of the IR radiance for each element of the scene.