Temperature-monitoring system screens for SARS

Just as happens every year with the common cold, the newly emerged Severe Acute Respiratory Syndrome (SARS) has taken advantage of the world's airways to spring up swiftly in many places around the globe.

Jun 1st, 2003
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Just as happens every year with the common cold, the newly emerged Severe Acute Respiratory Syndrome (SARS) has taken advantage of the world's airways to spring up swiftly in many places around the globe. Unlike a cold, though, SARS can be lethal. Concerted efforts have contained the disease in many hot spots, but not yet in others. Airports are becoming a focus in the efforts to contain SARS. Some airline carriers are screening people for symptoms of SARS, which include a dry cough and fever.

In response to this phenomenon, Indigo Systems (Goleta, CA) and WinSoft (Santa Ana, CA) have developed a longwave infrared (IR) imaging system that, in real time, takes the temperature of someone standing in front of it (see figure). The measurement is typically taken of facial skin and is accurate to 0.5°C.


Screening for fevers potentially symptomatic of SARS, a longwave IR-imaging system measures the skin temperature of an airline passenger or other traveler (top). Optoelectronic components of the system include a microbolometer-based camera (bottom) and two blackbody calibration sources (not shown).
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The system includes a camera, two blackbody calibration sources, a computer, and software, according to Rudy Machuca, a segment manager at Indigo Systems. The optoelectronic hardware, which was previously developed at Indigo, was combined with software created at WinSoft for this application. The system was developed in only a three-week period, says Machuca—a turnaround time made possible by the fact that the two companies had worked together before on other projects.

The 160 × 120-pixel IR imager itself is microbolometer-based (vanadium oxide), senses over the 7.5 to 13.5-µm spectral region, and has an 85-mK sensitivity when used with ƒ/1.6 optics. "The 0.5°C sensitivity of the system as a whole is a fairly conservative estimate, looking at worst-case scenarios resulting from the nonlaboratory environments the system will be used in," says Machuca. The software contains "hooks" to work with the camera as well as with the two calibration sources, each of which emits blackbody radiation of a different characteristic temperature, notes Machuca. Typically, the system must be calibrated once manually; from then on, it automatically calibrates itself.

A typical normal human body temperature is 37.0°C (98.6°F); any body temperature above 37.5°C (99.5°F) is considered abnormal enough to raise a flag in the system, says Machuca. Although the system is intended for use at airports, it could be used at entrances of commercial or government facilities as well, he adds.

In today's atmosphere of heightened threat, imaging technology is being integrated into security systems as never before (see Laser Focus World, April 2003, p. S1). The newly developed IR skin-temperature-monitoring system appears to be no exception—on the first day the system was made public, Indigo Systems and WinSoft received inquiries from Singapore, Vietnam, and Hong Kong.

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