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Proceedings Paper

Time-resolved videothermography at above-frame-rate frequencies
Author(s): Steven M. Shepard; David T. Sass; Thomas P. Imirowicz; A. Meng
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Paper Abstract

Temporal aliasing is a problem common all video imaging systems. IR video systems are particularly susceptible because of the relatively low (30 Hz) RS-170 frame rate. We have developed a system which compensates for the effects of aliasing, and allows images of repetitive thermal phenomena at frequencies up to 4 kHz to be acquired. The system utilizes an unmodified commercial imager (Inframetrics IR 600) and a microcomputer. Data is acquired selectively using a 'line-by-line' scheme which compares the motion of the camera's horizontal scanning mirror to a reference signal correlated to the event of interest. Only those horizontal lines that have a user-specified phase relationship to the reference signal are acquired. The resulting images have an effective integration time of 125 microseconds. This ability to acquire 'time-resolved' IR images allows investigation of phenomena not possible with a conventional RS-170 IR imaging system. For example, a conventional thermal image of an integrated circuit operating at several kilohertz yields no temporal information whatsoever. By comparison, we have acquired time-resolved images which show the AC heating and cooling of the circuit, so that we may identify AC hot spots. The system has also been applied to a running internal combustion engine. The imager views the piston head through an IR transparent (ZnS) window. Acquired images clearly show the motion of the flame front through the combustion chamber, and the subsequent heating and cooling of the piston head.

Paper Details

Date Published: 1 March 1991
PDF: 5 pages
Proc. SPIE 1467, Thermosense XIII, (1 March 1991); doi: 10.1117/12.46437
Show Author Affiliations
Steven M. Shepard, U.S. Army Tank and Automotive Command (United States)
David T. Sass, U.S. Army Tank and Automotive Command (United States)
Thomas P. Imirowicz, U.S. Army Tank and Automotive Command (United States)
A. Meng, U.S. Army Tank and Automotive Command (United States)

Published in SPIE Proceedings Vol. 1467:
Thermosense XIII
George S. Baird, Editor(s)

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