Pierre C. Trepagnier

Principal component analysis incorporating excitation, emission, and lifetime data of fluorescent bio-eerosols1

We describe a principal component analysis (PCA) of bio-aerosols which incorporates both fluorescence excitation-emission data over the excitation range 210 nm - 600 nm and lifetime data. The analysis suggests a useful separation metric based on spectral angle.

Background suppression and agent detection in multi-dimensional spaces

We describe a new method for background suppression and agent detection in principal component spaces derived from spectroscopic data to develop an improved trigger sensor for bioaerosol detection. Simulation results and laboratory data are shown.

A fluorescent bio-aerosol point detector incorporating excitation, emission, and lifetime data

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.

Stage accuracy results using interferometers compensated for refractivity fluctuations

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.