We describe algorithm development for a trigger system for bio-aerosol detection using bulk collection of aerosols. Two key problems inherent to any system which collects or probes a volume of air are presented - the "mixture" problem and the "spike" problem. We describe a background suppression and detection algorithm and show why knowledge of background endmembers is important. We present an endmember selection algorithm and show examples. Integrating these two algorithms solves both the mixture and spike problems and has applications to both bio-aerosol point detectors which collect samples from a volume of air, and to bio-aerosol stand-off detectors which probe a column of air.
We present a novel approach to a biological point detector system: extracting maximal information from fluorescence by using as much of the full excitation-emission-lifetime (XML) fluorescence space as can be conveniently gathered. Our paper has two parts. In the first part, we present initial XML spectral data gathered under Phase I of the DARPA Spectral-Sensing of Bio-Aerosols (SSBA) program using a commercial laboratory spectrofluorometer and illustrate its analysis in a multi-dimensional Principal Components Analysis (PCA) data space. We demonstrate classification using the spectral angle (SA) methodology developed for hyperspectral imaging in this PCA hyperspace. In the second part, we present a design for a custom trigger sensor developed in Phase II of the DARPA program. This Phase II sensor was motivated by the Phase I results and is intended to exploit them by gathering XML data at a rate consistent with near-real-time triggering.
Air refractivity changes, which include pressure, temperature, and composition effects, affect the performance of the Helium-Neon (HeNe) interferometer used to control the wafer and reticle stages of a step-and-scan lithography system. nanAlign is an auxiliary interferometer system designed to compensate for errors induced in a HeNe interferometer by refractivity changes. We conducted wafer exposure tests of nanAlign with 116 total wafers; 60 wafers with the same field order for each pass are discussed in this paper. We found that nanAlign measurements made on the x-axis could be used to improve the overlay in the y-axis. Over the entire ensemble of 60 wafers, the improvement of the x-axis was 0.6 nm, and the improvement of the y-axis was 0.4nm. Over the entire ensemble the worst wafers showed the most improvement, and there was some improvement on almost all wafers under a wide variety of conditions.
KEYWORDS: Signal processing, Surface plasmons, Digital signal processing, Stars, Surveillance, Cameras, Binary data, Space telescopes, Telescopes, Detection and tracking algorithms
An overview of the signal processor for the Space-Based Visible sensor system is presented. This signal processor, based on a 20 MHz Motorola DSP56001, places significant processing power into a satellite environment. The signal processor hardware and its real-time executive and applications software are briefly described. Typical performance figures are given, based on scenes taken by a ground-based telescope and processed by prototype hardware and software.
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