<title>Portable digital lidar: a compact stand-off bioagent aerosol sensor</title>

Abstract

Remote detection of biological warfare agents (BWA) is crucial for providing early warning to ensure maximum survivability of personnel in the battlefield and other sensitive areas. Although the current generation of stand-off aerosol and fluorescence lidars have demonstrated stand-offdetection and identification ofBWA, their large size and cost make them difficult for field use. We have introduced a new eye-safe portable digital lidar (PDL) technique based on digital detection that achieves orders of magnitude reduction in the size, cost and complexity over the conventional lidar, while providing an equal or better sensitivity and range. Excellent performance has been obtained with two ofour PDL sensors during two bio-aerosol measurement campaigns carried out at Dugway Proving Grounds. In the JFT 4.5 (Oct 98) tests, high aerosol sensitivity of 300ppl of biosimulant particles at up to 3km was demonstrated with an eye-safe single wavelength (523nm) aerosol micro PDL that utilized a 8' telescope, <1OiJ/pu1se energy at 2.5kHz, photon counting digital detection and 2 sec averaging. For the JBREWS DFT (June 99) tests an eye-safe two wavelength (523nm and 1 .O47.tm) horizontally scanned, aerosol micro PDL with the same 8 " telescope was utilized. With this lidar, high sensitivity, preliminary differentiation between natural and unusual clouds, and the ability to track the aerosol cloud location, their wind speed and direction were also demonstrated. Lidar simulations of both PDL and conventional analog detection lidar have been performed. Based on these model calculations and experimental results an analysis and comparison of the inherent capabilities of the two types of systems is given.

Optical Techniques for Detecting and Identifying Biological-Warfare Agents

“…Since the received signal is typically small, the APD is typically preferred over the PD, allowing for good QE, but suffering from relatively high dark current. A fairly recent development has been the photon-counting (Geiger-mode) APD, which detects a single photon at a time, providing a sensitivity that approaches the ideal Bwhite noise[ limit [69].…”

Compact 405-nm random-modulation continuous wave lidar for standoff biological warfare detection

“…7 The pulse output of a photomultiplier tube in the photon-counting mode can be understood as a digital signal which can be directly read by the FPGA chips; thus, a quick response A/D model is not required. 7 The pulse output of a photomultiplier tube in the photon-counting mode can be understood as a digital signal which can be directly read by the FPGA chips; thus, a quick response A/D model is not required.…”