Integrated high-fidelity physics-based simulations that include engagement models, image generation, electro-optical hardware models and control system algorithms have previously been developed by Boeing-SVS for various tracking and pointing systems. These simulations, however, had always used images with featureless or random backgrounds and simple target geometries. With the requirement to engage tactical ground targets in the presence of cluttered backgrounds, a new type of scene generation tool was required to fully evaluate system performance in this challenging environment. To answer this need, Irma was integrated into the existing suite of Boeing-SVS simulation tools, allowing scene generation capabilities with unprecedented realism. Irma is a US Air Force research tool used for high-resolution rendering and prediction of target and background signatures. The MATLAB/Simulink-based simulation achieves closed-loop tracking by running track algorithms on the Irma-generated images, processing the track errors through optical control algorithms, and moving simulated electro-optical elements. The geometry of these elements determines the sensor orientation with respect to the Irma database containing the three-dimensional background and target models. This orientation is dynamically passed to Irma through a Simulink S-function to generate the next image. This integrated simulation provides a test-bed for development and evaluation of tracking and control algorithms against representative images including complex background environments and realistic targets calibrated using field measurements.
An Underwater Scannerless Range Imager illuminates a wide field-of-view with a broadbeam laser pulse and captures the entire scene with an image intensified solid state camera. By imaging the received light onto a microchannel plate (MCP) receiver whose gain is modulated, and focusing the CCD camera on the phosphor screen that fluoresces upon excitation by the MCP output pulse, a sequence of images differing in the phase of the modulation waveform can be formed, and high precision target ranges can be inferred for each pixel of the viewed scene. When the medium between transmitter and target is obscured, as by turbid water, the return signal is temporally extended so that the inferred range picks up a bias owing to backscatter. The intimate relationship between the spatial and temporal behavior of the signals (near targets produce different temporal profiles than distant ones) adds complexity that cannot be handled by point spread functions, as is common for CW illumination and range-gated systems with constant gain. The method described here breaks the propagation problem into four channels depending on whether the light is scattered by the medium on the way to or from the target (or both, or neither), and calculates arrays to represent mean pathlengths and their variances. A fairly rigorous sensor model based on the various layers in a particular implementation (photocathode, MCP, phosphor, CCD array, A/D converter) and on receiver modulation transfer characteristics completes the prescription for generating realistic synthetic USRI images in moderate turbidity.
The Irma synthetic signature model was one of the first high resolution Infrared (IR) target and background signature models to be developed for tactical weapons application. Originally developed in 1980 by the Munitions Directorate of the Air Force Research Laboratory (AFRL/MN), the Irma model was used exclusively to generate IR scenes for smart weapons research and development. In 1988, a number of significant upgrades to Irma were initiated including the addition of a laser channel. This two channel version was released to the user community in 1990. In 1992, an improved scene generator was incorporated into the Irma model which supported correlated frame-to-frame imagery. A passive IR/millimeter wave (MMW) code was completed in 1994. This served as the cornerstone for the development of the co-registered active/passive IR/MMW model, Irma 4.0. The latest version of Irma, 4.1, was released in April 1998 during the Aerosense Conference. It incorporated a number of upgrades to both the physical models and software. Current development efforts are focused on the inclusion of circular polarization, hybrid ladar signature blending, an RF air-to-air channel, reconfigurable sensor model, and enhance user interface. These capabilities will be integrated into the next release, Irma 5.0, scheduled for completion in FY00. The purpose of this paper is to demonstrate the progress of the Irma 5.0 development effort. Irma is being developed to facilitate multi-sensor research and development. It is currently being used to support a number of civilian and military applications. The Irma user base includes over 130 agencies within the Air Force, Army, Navy, DARPA, NASA, Department of Transportation, academia, and industry.
Realistic backgrounds are necessary to support high fidelity hardware-in-the-loop testing. Advanced avionics and weapon system sensors are driving the requirement for higher resolution imagery. The model-test-model philosophy being promoted by the T&E community is resulting in the need for backgrounds that are realistic or virtual representations of actual test areas. Combined, these requirements led to a major upgrade of the terrain database used for hardware-in-the-loop testing at the Guided Weapons Evaluation Facility (GWEF) at Eglin Air Force Base, Florida. This paper will describe the process used to generate the high-resolution (1-foot) database of ten sites totaling over 20 square kilometers of the Eglin range. this process involved generating digital elevation maps from stereo aerial imagery and classifying ground cover material using the spectral content. These databases were then optimized for real-time operation at 90 Hz.
The Irma synthetic signature model was one of the first high resolution infrared (IR) target and background signature models to be developed for tactical weapons application. Originally developed in 1980 by the Munitions Directorate of the Air Force Research Laboratory, the Irma model was used exclusively to generate IR scenes for smart weapons research and development. In 1988, a number of significant upgrades to Irma were initiated including the addition of a laser channel. This two channel version, Irma 3.0, was released to the user community in 1990. In 1992, an improved scene generator was incorporated into the Irma model which supported correlated frame-to-frame imagery. This and other improvements were released in Irma 2.2. Irma 3.2, a passive IR/millimeter wave (MMW) code, was completed in 1994. This served as the cornerstone for the development of the co- registered active/passive IR/MMW model, Irma 4.0. Currently, upgrades are underway to include a near IR (NIR)/visible channel; a facet editor; utilities to support image viewing and scaling; and additional target/data files. The Irma 4.1 software development effort is nearly completion. The purpose of this paper is to illustrate the results of the development. Planned upgrades for Irma 5.0 will be provided as well. Irma is being developed to facilitate multi-sensor research and development. It is currently being used to support a number of civilian and military applications. The current Irma user base includes over 100 agencies within the Air Force, Army, Navy, DARPA, NASA, Department of Transportation, academia, and industry.
Complete specification s for commercially available polarizers and retarders are often not available, incomplete, or inaccurate. We analyze several commercial polarization elements using Mueller matrix polarimetry. Elements are characterized in terms of their diattenuation, retardance, and depolarization. Measurements were made with laser polarimeters and a spectropolarimeter.