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Fraunhofer Group for Microelectronics

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A better view thanks to infrared cameras

Driving at night on an unlit highway, it is hard to see ahead down the winding road and so the driver steers carefully, which does not stop him from almost hitting a deer. Infrared cameras could provide more safety in situations like this. Their sensors, however, usually need to be cooled. Researchers at Fraunhofer IMS in Duisburg have now found a way of allowing infrared cameras to work at room temperature.

 

A better view thanks to infrared cameras. Photo: Fraunhofer IMS
A better view thanks to infrared cameras. Photo: Fraunhofer IMS
Safe driving in poor visibility thanks to infrared cameras with an IRFPA sensor from Fraunhofer IMS. Photo: pixelio.de / Wolfgang Colditz
Safe driving in poor visibility thanks to infrared cameras with an IRFPA sensor from Fraunhofer IMS. Photo: pixelio.de / Wolfgang Colditz
The first laboratory tests on the new sensor element were a success, and researchers have been able to record a few infrared images. Photo: Fraunhofer IMS
The first laboratory tests on the new sensor element were a success, and researchers have been able to record a few infrared images. Photo: Fraunhofer IMS

Infrared cameras can see more than the naked eye and can help to make road traffic safer. This is because objects approximately at body temperature “glow” by themselves within the far-infrared wavelength range of 10 micrometers. Detectors in the camera record this heat dissipation and use it to locate the source of the heat. This allows the driver to detect people or animals long before the dipped-beam headlamps pick up on them.

Infrared cameras like it cold

For cameras that detect the far-infrared wavelength range, the sensor must, however, always be cooled to about minus 193 °C when in use. That is costly and requires additional effort. There are indeed uncooled imagers for the far-infrared range, but they are mostly used by the military and are hardly available on the European market. That’s set to change: Researchers at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg have succeeded in producing an imaging sensor for the far-infrared range that operates at room temperature. “We were the first in Germany to offer this technology,” says Dr. Dirk Weiler, a scientist at Fraunhofer IMS.

Temperature-resistant sensor

At the core of this IRFPA sensor, as it is known (Infrared Focal Plane Array), is a microbolometer. That is a temperature-dependent detector that absorbs long-wave infrared light. To generate a two-dimensional image, several microbolometers are joined together to form an array. When the microbolometer absorbs light from a heat source, the temperature inside it rises and changes its electrical resistance. A readout chip converts this resistance change straight into a digital signal. Until now, this has required an additional step: The electrical signal is normally first converted into an analog signal and then digitalized using an analog-digital converter. The scientists at Fraunhofer IMS have decided to use a sigma-delta converter for the new far-infrared sensor: a converter that generates a digital signal directly.

Wide range of possible uses

As the costly cooling is no longer required, a range of new fields of applications has been opened up to infrared cameras with an IRFPA sensor: As well as their use in cars, they are expected to be in demand for mobile devices. This is because the lack of a cooling mechanism not only saves weight; it also increases the battery life and therefore the operating time of a mobile device. Another potential use for mobile infrared cameras is in firefighting, such as in finding hidden fires or people trapped in smokefilled buildings.

Contact:

Martin van Ackeren
Phone +49 203 3783-130
martin.van.ackeren(at)ims.fraunhofer.de

Dr. Dirk Weiler
Phone +49 203 3783-219
dirk.weiler(at)ims.fraunhofer.de

Fraunhofer Institute for Microelectronic Circuits and Systems IMS
Finkenstrasse 61
47057 Duisburg
Germany
www.ims.fraunhofer.de