In this report, we show both theoretically and experimentally how the IR signature of a semiconductor scene (with band gap energy Eg) can be monitored through contactless emissivity control even if this scene thermometric temperature is kept constant. More specifically, we show how a scene emissivity in the spectral band beyond the fundamental absorption range (ω2 < Eg / h, 3 to 5 μm and 8 to 12 μm transparency windows) can be dynamically (frame frequency > 20 kHz) monitored by a shorter wavelength photo excitation of non-equilibrium charge carriers (ω1 > Eg/h, "visible range"). Experimental tests performed on Si and Ge scenes (300 < T < 600 K), demonstrate optically generated cold and hot images and, what is more important, negligible temperature contrast between an object and a background (Stealth effect in IR).
The Kinetic Kill Vehicle Hardware-In-the-Loop Simulator, located at Eglin AFB, has developed the capability to perform broadband 2-color testing of guided missile seekers in both ambient and cryogenic environments. The 2-color capability is provided by optically combining two 512 X 512 resistor arrays and projecting through all-reflective optical systems. This capability has raised the following questions: `How would a resistor array, designed to work at ambient conditions, perform when operated in a cryogenic environment?' and `How would a resistor array that was non- uniformity corrected (NUC) at ambient conditions perform when the NUC is applied to the array in a cryogenic environment?' The authors will attempt to address these questions by performing several measurements on a Wideband Infrared Scene Projector (WISP) Phase III resistor array in both ambient and cryogenic conditions. The WISP array performance will be defined in terms of temporal response, spatial non-uniformity, radiometric and thermal resolution, and radiometric and thermal transfer function.
Naval Research Laboratory (NRL) has been developing high brightness mid-wave IR emitting fibers for HWIL testing. These fibers, based upon rare-earth doped chalcogenide glass, emit from 3.5 - 5 m and are capable of simulating very high temperatures in this band. To date, temperatures of 2400 K have been simulated. The fiber sources operate at room temperature, are environmentally tolerant, and can be formed into fiber bundles with high fill factors and low pixel to pixel cross- talk for IR scene generation. In this paper, we will present the spectral output, temporal response, temperature simulation and output uniformity of the mid-wave IR emitting fibers. The potential for long-wave IR emitting fiber sources will also be presented.
In the past year, Honeywell has developed a 512 X 512 snapshot scene projector containing pixels with very high radiance efficiency. The array can operate in both snapshot and raster mode. The array pixels have near black body characteristics, high radiance outputs, broad band performance, and high speed. IR measurements and performance of these pixels will be described. In addition, a vacuum probe station that makes it possible to select the best die for packaging and delivery based on wafer level radiance screening, has been developed and is in operation. This system, as well as other improvements, will be described. Finally, a review of the status of the present projectors and plans for future arrays is included.
The KHILS Vacuum Cold Chamber (KVACC) was developed to provide the capability of performing hardware-in-the-loop testing of infrared seekers requiring scenes involving cold backgrounds. Being able to project cold backgrounds enables the projector to simulate high-altitude exoatmospheric engagements. Previous tests with the KVACC projection system have used only one resistive-array projection device. In order to realistically stimulate a 2-color seeker, it is necessary to project in two, independently controlled IR bands. Missile interceptors commonly use two or more colors; thus, a 2-color projection capability has been developed for the KVACC system. The 2- color projection capability is being accomplished by optically combining two Phase 3 WISP arrays with a dichroic beam combiner. Both WISP arrays are cooled to user-selected temperatures ranging from ambient temperature to below 150 K. In order to test the projection system, a special-purpose camera has also been developed. The camera is designed to operate inside the vacuum chamber. It has a cooled, all- reflective broadband optical system to enable the measurement of low radiance levels in the 3 - 12 micrometer spectrum. Camera upgrades later this year will allow measurements in two independent wavebands. Both the camera and the projector will be described in this paper.
KEYWORDS: Infrared radiation, Nonuniformity corrections, Infrared imaging, Commercial off the shelf technology, Projection systems, RGB color model, Thermography, Mid-IR, Temperature metrology, Transform theory
It is shown that commercial-off-the-shelf (COTS) renderers can be used for covering the simultaneous fine temperature resolution and large dynamic range specifications associated with the demands of medium-wave infrared scene projection applications. Appropriate use of the RGB capabilities of the COTS renderer combined with redistribution of the binary scene data by using a nonlinear transformation enables the dual specifications for 0.1 degree Celsius small signal temperature resolution and > 400 degree Celsius range in simulated temperature difference to be simultaneously met.
The third generation of the Wide-band Infrared Scene Projector (WISP) resistor arrays has been delivered to the Air Force Research Laboratory's Kinetic Kill Vehicle Hardware-in-the-Loop Simulation facility. A critical parameter in determining the extent with which the thermal arrays simulate the real world is the radiometric and thermal resolution. The measurement of the resolution is dependent upon several factors including the input data word resolution, drive electronics resolution, system noise factors, and the measurement sensor. Several measurements were made to quantify the noise components of the WISP array and the measurement sensor to determine the limiting factor for the measurements. Due to the nonlinear transfer function between the command voltage and the projected radiance, measurements were made at several input levels to determine how the resolution varies as a function of command voltage level. Measurements were performed both with and without the spatial non-uniformity correction (NUC) applied to determine the impact of the NUC on the radiometric resolution. Based on the results of these measurements the resolution of the WISP arrays is defined in both radiometric and thermal units.
KEYWORDS: Cameras, Projection systems, Calibration, Black bodies, Quantum well infrared photodetectors, Long wavelength infrared, Infrared radiation, Mid-IR, Temperature metrology, Imaging systems
The Wideband Infrared Scene Projector (WISP) has been undergoing development for the Kinetic-Kill Vehicle Hardware-in-the-Loop Simulator facility at Eglin AFB, Florida. In order to perform realistic tests of an infrared seeker, the radiometric output of the WISP system must produce the same response in the seeker as the real scene. In order to ensure this radiometric realism, calibration procedures must be established and followed. This paper describes calibration procedures that have been used in recent tests. The procedures require knowledge of the camera spectral response in the seeker under test. The camera is set up to operate over the desired range of observable radiances. The camera is then nonuniformity corrected (NUCed) and calibrated with an extended blackbody. The camera drift rates are characterized, and as necessary, the camera is reNUCed and recalibrated. The camera is then set up to observe the WISP system, and calibration measurements are made of the camera/WISP system.
The KHILS Vacuum Cold Chamber (KVACC) provides the capability of testing IR seekers with scenes involving a `cold' background, more closely simulating a high altitude/exoatmospheric engagement. During the past year, a gaseous helium refrigeration system has been installed to simplify the logistics of cooling the chamber. An antechamber has also been installed to serve as a chamber for the sensor under test. A WISP array was installed in the Source Chamber. A thermal control system was developed by connecting the array to a cold surface by way of a thermal choke, then actively controlling the temperature with heating elements. This made it possible to operate the array at user selected, stable substrate temperatures ranging from ambient temperature to below 150 K. This capability makes it possible to select the infrared background level that the array operates at, and to operate with background levels that are adequate for testing the high altitude/exoatmospheric engagements. WISP arrays were designed for room temperature operation, but predicted performance at reduced temperatures appears acceptable. Tests were performed with a Phase I prototype WISP array inside the KVACC Source Chamber. Data on this array's radiometric response at various substrate temperatures are presented. It is demonstrated that the arrays can be operated at substrate temperatures as low as 145 K. Currently two Phase 3 WISP arrays and a dichroic beam combiner are being installed in the Source Chamber for 2- color testing.
The Wideband Infrared Scene Projector (WISP) has been undergoing development for the AF Research Laboratory Kinetic Kill Vehicle Hardware-in-the-loop Simulator facility (KHILS) at Eglin AFB, FL. Numerous characterization measurements defining array dynamic range, spectral output, temporal response and nonuniformity have been performed and reported on in the past. This paper addresses the measurements and analyses performed to characterize the radiometric, spatial, and temporal noise errors induced by the array on a unit under test (UUT). An Amber camera was used as the UUT. The Amber camera spectral, spatial and radiometric response characteristics were measured. The camera spatial and temporal noises were measured by observing an extended blackbody. Similar measurements were then made on the WISP/UUT system by projecting uniform scenes. The WISP spatial and radiometric responses and the WISP-induced spatial and temporal noise were determined from the measurements. Although the measurements are unique to the UUT adopted, the WISP contribution to the system noise-equivalent temperature difference (NEDT) was determined. The spatial noise measurements provided data for validating a spatial noise model described in a companion paper. The measurements and models are useful for analyzing future measurements and predicting the impact of WISP on various test articles.
To address the many challenges that are required to support testing of state-of-the-art guided weapons the Kinetic Kill Vehicle Hardware-in-the-Loop Simulation (KHILS) facility located at Eglin AFB, FL has integrated two projector technologies into one Infrared (IR) projector. This new projector combines the capabilities of the resistor array technology with the capabilities of a non-imaging laser scanning projector (SLP) to provide KHILS with a unique testing asset. To provide representative simulations of the real world both systems will need to perform a radiometric and spatial calibration to the unit-under-test (UUT) and will need to be synchronized together. This projector was utilized to perform closed-loop hardware-in-the-loop (HWIL) testing using real-time 3D scene generation to support several test entries. Using the UUT several measurements of the projector were proposed to characterize the performance of the two technologies. This paper will report the results of these tests along with the methods used to integrate the two projectors into one system.
Kinetic Energy Weapon (KEW) programs under the Ballistic Missile Defense Office (BMDO) need high fidelity infrared (IR) seekers. As imaging sensors have matured to support BMDO, the complexity of functions assigned to the KEW weapon systems has magnified the necessity for robust hardware-in- the-loop (HWIL) simulation facilities to reduce program risk. The IR projector, an integral component of a HWIL simulation, must reproduce the real world with enough fidelity that the unit-under-test algorithms respond to the projected images as though it were viewing the real world. For test scenarios involving unresolved objects, IR projector arrays have limitations which constrain testing accuracy. These arrays have limited dynamic range, spatial resolution, and spatial bandwidth for unresolved targets, decoys, and debris. The Steerable Laser Projector (SLP) will allow the HWIL simulation facility to address these testing issues. The Kinetic Kill Vehicle Hardware-in-the-loop Simulation (KHILS) facility located at Eglin AFB, FL is now in the process of integrating a projector array with the SLP. This new projector combines the capabilities of both projector technologies to provide KHILS with a unique asset that addresses many of the challenges that are required to support testing of state-of-the-art IR guided weapons.
KEYWORDS: Computer simulations, Missiles, Data modeling, Distortion, Signal processing, Sensors, Convolution, Energy based weapons, Control systems, Image processing
The Kinetic-kill-vehicle Hardware-in-the-Loop Simulation Facility (KHILS), located at Eglin AFB FL, has been involved in the development and ground testing of Ballistic Missile Defense Organization hit-to-kill interceptor concepts for 10 years. Work is ongoing to characterize the implement hardware-in-the-loop models for missile `environment' effects that are associated with high speed flight in general and endo-atmospheric flight in particular. Two critical areas of interest in endo-atmospheric simulation are: (1) effects on the line-of-sight due to divert thruster firings and the resulting structural vibration, and (2) the line-of-sight aero-optical environment which can be influenced by heated missile flowfields, coolant layers, and thruster fringes. The structural and aero-optical effects manifest themselves as image jitter, blurring, boresight shifts, and increased background radiance. At the KHILS facility, real-time closed-loop simulation techniques are being developed for structural and aero-optical effects presentation. These techniques include both software and hardware solutions. This paper describe the status of activities by describing the issues and the present KHILS solutions. The paper includes discussion of model interfaces with hardware-in-the-loop simulations, timing issues, and data transmittal bandwidth requirements. Image show the effects of structural and aero-optical disturbances on seeker focal plane energy distributions.
A steerable laser infrared projector (SLP) has been designed by Aegis Research Corporation and is currently being integrated into the Kinetic Kill Vehicle Hardware-in-the- Loop Simulator facility located at the Wright Laboratory Armament Directorate, Eglin Air Force Base, FL. The SLP utilizes lead salt laser diodes as the projector sources and two-axis galvanometer beam scanners to project six independently controlled point source targets to the unit- under-test. The laser diodes provide high intensity, 16 BIT radiometric resolution targets while the galvanometers provide wide angle, high precision (16 BIT) beam steering performance. Due to the nonlinear relationship between the input drive current and the output power of the diodes the calibration of the multiple sources is critical to the successful utilization of the projector.
Kinetic energy weapon (KEW) programs under the Ballistic Missile Defense Office (BMDO) need high fidelity, fast framing infrared (IR) imaging seekers. As imaging sensors have matured to support BMDO, the complexity of functions assigned to the KEW weapon systems has amplified the necessity for robust hardware-in-the-loop (HWIL) simulation facilities to reduce program risk. The IR projector, an integral component of a HWIL simulation, must reproduce the real world with enough fidelity that the unit under test's (UUT) software will respond to the projected scenario of images as though it were viewing the real world. The CMOS resistor array IR scene projector, a wideband flickerless technology, shows great promise in cryogenic vacuum chamber as well as room temperature testing. A 128 X 128 CMOS resistor array has undergone extensive characterization measurements at Eglin AFB to determine its potential for HWIL testing of BMDO IR seekers. This paper addresses the nonuniformity correction (NUC) and use of the array in a calibrated projection test. The methodology and process for the NUC is described. Sensitivities to such things as output averaging, and optical sampling are explained. With the NUC procedure established, a test was accomplished that provided calibrated scene radiance values to a UUT. Absolute radiance values were not projected. Rather, the array's low and high output capabilities were equated to the low and high radiance values of an input scene. A calibration curve was established that allowed the UUT's output to be equated to the input scene's radiance values. The input scene was projected to the UUT, and the scene's radiance values were reproduced after applying the calibration curve to the UUT's output response. To the authors' knowledge, this if the first accomplishment of such a test with a dynamic IR scene projector.
A scophony infrared scene projector (IRSP) was developed by AURA Systems Inc. for use in evaluating thermal imaging guidance systems. The IRSP is a laser-scanned projector system incorporating scophony modulation with acousto-optical (AO) devices to produce multiband 96 x 96 image frames. A description of the system and preliminary test results with the Seeker Endo/Exo Demonstration Development (SEEDD) breadboard interceptor are addressed.
An all acousto-optic infrared scene projector (IRSP) has been developed for use in evaluating thermal-imaging guidance systems at the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator (KHILS) facility located at Elgin AFB, Florida. The IRSP is a laser source based projector incorporating Scophony illumination and scanning methods to produce 96 X 96 pixel multi-wavelength images at very high frame rates (400 Hz). The IRSP is composed of five functionally similar optical trains, four of which are fed with a different `color' infrared laser. The separate scenes from each optical train are then combined and projected simultaneously into the imaging guidance system.
A Scophony Infrared Scene Projector (IRSP) was developed for use in evaluating thermal- imaging guidance systems. The IRSP is a very high frame rate, laser scanned projection system incorporating Scophony modulation. The Scophony IRSP serves as the image projection system in the Kinetic Kill Vehicle Hardware in the Loop Simulator (KHILS) terminal guidance simulation. It is capable of projecting multiband target engagement scenarios with high fidelity using Aura's proprietary software/electronic control system. The Scophony IRSP utilizes acousto-optical (AO) devices to produce the required imagery at separate wavelengths, simultaneously. The separate scenes are combined and projected into the imaging guidance system. The Scophony IRSP has been installed and integrated into the KHILS facility at Eglin Air Force Base, Florida. Some performance characteristics of the IRSP have been measured. The current presentation provides a brief description of the Scophony IRSP and a performance evaluation. The performance characteristics measured are spot size, dynamic range, and field of view. Further characteristics may be reported as they become available.
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