Safety in a Snap: Infrared Camera Boosts Vision

Wednesday, July 7, 2010 @ 03:07 PM gHale


Think of the safety ramifications of an infrared camera that can see well beyond what a human can visualize.
Just in terms of driving a car on a foggy, dark road, the safety potential is limitless. Think also about the process safety possibilities.
For cameras that deal in the long-wave infrared range the problem has always been the sensor requires constant cooling, which adds to the cost and complexity of the device. Now a new type of detector can work at room temperature.

Infrared camera photo shows the different temperature variations.

Infrared camera photo shows the different temperature variations.


In terms of driving safety, the scenario is you are driving at night on an unlit country road and the bends along the way restrict the view ahead and, to make things worse, it is foggy. The car driver is exercising all due care and yet still does not see the deer on the road ahead until it is nearly too late. A quick slam on the brakes and the accident does not occur, but that is because the driver used all due caution. That does not happen all the time, so as much advanced warning as possible would help in that type of case.
In that situation an infrared camera could provide a better level of safety. Objects at roughly body temperature are luminous in the infrared region at a wavelength of around ten micrometers. Detectors in the camera register this thermal radiation and locate the source of heat. This could enable drivers to see people or animals long before they come into vision through dipped headlights. In addition, drivers of other cars would not suffer because the infrared is invisible.
The problem is for the wavelength range above five micrometers infrared cameras like it cold, the sensor has to constantly cool down to minus 193 degrees Celsius. Uncooled imagers for the long-wave infrared range do already exist today, but they mainly see use in the military.
Research scientists at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg, Germany, created an imaging sensor for the long-wave infrared range that functions at room temperature.
At the heart of the IRFPA (Infrared Focal Plane Array) sensor is a microbolometer – a temperature-sensitive detector that absorbs long-wave infrared light, said Dr. Dirk Weiler, scientist at the IMS.
To produce a two-dimensional image, several microbolometers combine to form an array. If the microbolometer absorbs light from a heat source, its interior temperature rises and its electrical resistance changes. A readout chip then converts this resistance value directly into a digital signal. Previously this was not possible without a further intermediate step, normally the electrical pulse first translated into an analog signal and then digitized using an analog/digital converter.
“We use a very specific type of converter, a sigma-delta converter, in our imager. This has enabled us to produce a digital signal directly,” Weiler said.
As complex and costly cooling is no longer required, further areas of application become feasible beyond the automotive sector.
“Mobile devices in particular should benefit from the new development,” Weiler said. The fact the device no longer needs a cooling mechanism not only saves weight, it also boosts battery power and the operating time because it does not need energy for cooling, Weiler said. The potential uses of mobile infrared cameras include checking for hidden hot spots in a plant manufacturing area.
Initial tests with the new sensor element were successful. The research scientists have already been able to produce a number of infrared images.



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