Infrared Microbolometer Sensors and Their Application in Automotive Safety
Recently the emergence of a new generation of infrared sensors — the microbolometer technology — based on an infrared thermal detection mechanism which is particularly suited to operate at ambient temperature has opened the opportunity for achieving low c
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Infrared Microbolometer Sensors and Their Application in Automotive Safety
JJ. Yon, E. Mottin, CEA L. Biancardini, L. Letellier, CEA JL. Tissot, ULIS Abstract Recently the emergence of a new generation of infrared sensors – the microbolometer technology – based on an infrared thermal detection mechanism which is particularly suited to operate at ambient temperature has opened the opportunity for achieving low cost infrared imaging systems for both military and commercial applications. In a first part, this paper gives an overview of this challenging technology highlighting the main characteristics of the sensors developed by LETI that are particularly relevant to automotive applications. A special highlight on recent results concerning the 160x120 focal plane array with a pixel pitch of 35µm is given. In a second part, the use of this technology in automotive safety field is illustrated through an application of detection of moving objects in front of a vehicle. The results shows that infrared sensors based on well-designed microbolometers represent a real middle-term alternative to usual video sensors.
1
Background
The automotive industry increasingly looks to microsystems to put intelligence into cars. Safety improvement is particularly concerned with this trend: acceleration sensors for airbags, tire pressure monitoring and collision avoidance radar system. However, despite all of the automotive safety breakthroughs of this last decade, drivers still face potential hazards during conditions of darkness or obscured visibility such as is present with fog, heavy rain or snow. A challenging concern for the next few years is to improve vehicle safety in such adverse conditions with the operation of front-hazard warning devices and reliable collision avoidance systems. One of the major issues of such safety systems largely deals with the availability of adequate sensors that allow an early and reliable detection of road
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Safety
obstacles in front of the car. Infrared thermal imaging is particularly suited for this purpose as it provides an effective night-time viewing system that could tackle the inefficiency of the usual sensors and fulfils the night driving safety requirements. Indeed, thermal imaging systems detect the electromagnetic radiation emitted by any object at room temperature whatever its natural or artificial illumination. As a result, infrared sensor intrinsically offers large advantages in comparison to alternative sensors working in the visible spectrum or in the millimetric wavelength range such as radars do. This statement is clearly illustrated considering that a visible vision camera exhibits poor efficiency in bad weather conditions even if it is coupled with automobile headlights illumination. Moreover the range of the road that can be covered by headlights at night is much less than the eye can see during daylight. Unlike visible vision, Infrared vision enhances the range of visibility at night up to six times further than standard headlights. On the other hand, radar systems typical
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