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Proceedings Paper

A novel NIR camera with extended dynamic range
Author(s): Austin A. Richards; Shariff D'Souza
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Paper Abstract

We have constructed a novel filter wheel camera that allows filters to be rapidly and sequentially introduced into the optical path of a high-performance NIR (near-infrared) camera based on a staring focal-plane array (FPA) made with indium gallium arsenide (InGaAs) detectors. The filter wheel is populated with neutral density filters ranging from a transmission of 0.97 (essentially no attenuation) to ~10-5 (an ND5 filter stack). The camera acquires images with increasing attenuation of signal in cycles of six images called subframes. Those images are collapsed into a single radiometrically-calibrated image (called a superframe) with a greatly extended dynamic range. In the current configuration of the system, the radiance dynamic range is about 4x106, which is equivalent to 22 bits, a significant enhancement over the nominal 14-bit dynamic range of the camera core. This extended range makes it possible to make radiometric measurements on low ambient light scenes with tremendous variability of temperature or radiance, such as rocket launches, laser beams and intense flames. It is also possible to image scenes with high ambient near-infrared light levels, such as landscape on bright, sunny days without having to dynamically adjust exposure. Since the wheel rotates at high speed (15 Hz), the resulting dataset of six-frame cycles can be reduced to a superframe movie sequence with 15 Hz frame rate, making it possible to image spatially-changing scenes such as rocket launches with good image registration between subframes in a given cycle.

Paper Details

Date Published: 18 April 2006
PDF: 13 pages
Proc. SPIE 6205, Thermosense XXVIII, 62050G (18 April 2006); doi: 10.1117/12.668218
Show Author Affiliations
Austin A. Richards, FLIR Systems, Indigo Operations (United States)
Shariff D'Souza, FLIR Systems, Indigo Operations (United States)

Published in SPIE Proceedings Vol. 6205:
Thermosense XXVIII
Jonathan J. Miles; G. Raymond Peacock; Kathryn M. Knettel, Editor(s)

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