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Optics detection using an avalanche photo diode array and the scanning-slit-method
Author(s): Daniel Svedbrand; Lars Allard; Magnus Pettersson; Pontus Köhler; Markus Henriksson; Lars Sjökvist
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Paper Abstract

The ability to detect optics is important for military surveillance, and allows early threat detection. Present-day optics detection systems are exploiting that focusing optics are retro-reflective. Hence, it is possible to discover threats, including riflescopes, electro-optical sensors, and magnifying optical assemblies used for weapon guidance, by illuminating them with a laser. However, the sensors have performance limitations and do not usually provide range information about the target. This work suggests a scanning optics detection system that uses a linear array of avalanche photo diodes (APD) with high sensitivity providing information about the target range and angular location. An experimental system using four pixels of a 16×1 linear APD array was constructed and tested against reference targets outdoors. The receiver assembly consisted of a micro-lens array, focusing optics, bandpass filter, and pre-amplifier circuit. The system also contained a pulsed NIR-laser, motorized pan-tilt stages for the scanning, and a calibrated scene camera to measure the background signal. It was possible to detect reference targets at over kilometre range while distinguishing the background, using dedicated signal analysis and noise reduction. The suggested scheme definitely benefit in long-range performance compared to similar techniques that use CCD/CMOS-sensors. The drawback using an APD array lies in reduced angular resolution and increased complexity of data acquisition electronics. In addition, the experimental results will be discussed in terms of a performance model, influence from turbulence effects and suggestions for future sensor improvements.

Paper Details

Date Published: 7 October 2019
PDF: 11 pages
Proc. SPIE 11161, Technologies for Optical Countermeasures XVI, 111610J (7 October 2019); doi: 10.1117/12.2531795
Show Author Affiliations
Daniel Svedbrand, FOI-Swedish Defence Research Agency (Sweden)
Lars Allard, FOI-Swedish Defence Research Agency (Sweden)
Magnus Pettersson, FOI-Swedish Defence Research Agency (Sweden)
Pontus Köhler, FOI-Swedish Defence Research Agency (Sweden)
Markus Henriksson, FOI-Swedish Defence Research Agency (Sweden)
Lars Sjökvist, FOI-Swedish Defence Research Agency (Sweden)


Published in SPIE Proceedings Vol. 11161:
Technologies for Optical Countermeasures XVI
David H. Titterton; Robert J. Grasso; Mark A. Richardson, Editor(s)

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