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Proceedings Paper

Thermal hyperspectral chemical imaging
Author(s): Hannu Holma; Timo Hyvärinen; Antti-Jussi Mattila; Ilkka Kormano
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Paper Abstract

Several chemical compounds have their strongest spectral signatures in the thermal region. This paper presents three push-broom thermal hyperspectral imagers. The first operates in MWIR (2.8-5 μm) with 35 nm spectral resolution. It consists of uncooled imaging spectrograph and cryogenically cooled InSb camera, with spatial resolution of 320/640 pixels and image rate to 400 Hz. The second imager covers LWIR in 7.6-12 μm with 32 spectral bands. It employs an uncooled microbolometer array and spectrograph. These imagers have been designed for chemical mapping in reflection mode in industry and laboratory. An efficient line-illumination source has been developed, and it makes possible thermal hyperspectral imaging in reflection with much higher signal and SNR than is obtained from room temperature emission. Application demonstrations including sorting of dark plastics and mineralogical mapping of drill cores are presented. The third imager utilizes a cryo-cooled MCT array with precisely temperature stabilized optics. The optics is not cooled, but instrument radiation is suppressed by special filtering and corrected by BMC (Background-Monitoring-on-Chip) method. The approach provides excellent sensitivity in an instrument which is portable and compact enough for installation in UAVs. The imager has been verified in 7.6 to 12.3 μm to provide NESR of 18 mW/(m2 sr μm) at 10 μm for 300 K target with 100 spectral bands and 384 spatial samples. It results in SNR of higher than 500. The performance makes possible various applications from gas detection to mineral exploration and vegetation surveys. Results from outdoor and airborne experiments are shown.

Paper Details

Date Published: 17 May 2012
PDF: 12 pages
Proc. SPIE 8374, Next-Generation Spectroscopic Technologies V, 83740E (17 May 2012); doi: 10.1117/12.919294
Show Author Affiliations
Hannu Holma, Specim, Spectral Imaging Ltd. (Finland)
Timo Hyvärinen, Specim, Spectral Imaging Ltd. (Finland)
Antti-Jussi Mattila, Specim, Spectral Imaging Ltd. (Finland)
Ilkka Kormano, Specim, Spectral Imaging Ltd. (Finland)

Published in SPIE Proceedings Vol. 8374:
Next-Generation Spectroscopic Technologies V
Mark A. Druy; Richard A. Crocombe, Editor(s)

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