Abstract
We designed a cheap broadband uncooled microimager operating
in the long-wavelength infrared range using only one lens at a minimal cost for
the manufacturing process. The approach is based on thin optics where the
device volume is small and therefore inexpensive materials can be used because
some absorption can be tolerated. We have used a Fresnel lens on a thin silicon
substrate. Up to now, Fresnel lenses have not been used for broadband imaging
because of their chromatic properties. However, working in a relatively high
diffraction order can significantly reduce chromatism. A prototype has been
made for short range or indoor low-cost surveillance applications like people
counting, and experimental images are presented.