Calibrated sensitive polarization measurement methods in the regions 3-5 μm and 8-12 μm, corrected for contributions to the detector signal from the polarizer.

Exploitation of polarization increases the contrast in imaging sensors and makes reconnaissance and surveillance sensors more efficient. This paper reports about two methods of polarization measurements. The used equipments are two IR Thermovision(R)900 cameras, one in the wavelength region 3-5 mum and the other in the region 8-12 mum. The cameras have polarizing filters in front of the sensors. A calibration method is applied. In that way it is possible to correct for the signal contribution from the polarizing filters. The contribution can be separated into two parts, one consists of contributions to the detector signal due to the temperature of the filters and the other consists of reflections at the filter surfaces (Narcissus effects). The measurement methods are illustrated by laboratory measurements of surfaces of different surface roughness. The objectives of these measurements are to understand the physical properties of different surfaces for camouflage work. Also, calibrated sensitive polarization measurements of backgrounds are reported. The methods make it possible for the sensors to increase their ability for detection, recognition and classification.