A novel NIR camera with extended dynamic range

Austin A. Richards; Shariff D'Souza

doi:10.1117/12.668218

18 April 2006 A novel NIR camera with extended dynamic range

Austin A. Richards, Shariff D'Souza

Proceedings Volume 6205, Thermosense XXVIII; 62050G (2006) https://doi.org/10.1117/12.668218
Event: Defense and Security Symposium, 2006, Orlando (Kissimmee), Florida, United States

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.

Citation Download Citation

Austin A. Richards and Shariff D'Souza "A novel NIR camera with extended dynamic range", Proc. SPIE 6205, Thermosense XXVIII, 62050G (18 April 2006); https://doi.org/10.1117/12.668218

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