Passive optical polarization is a versatile method to find partly covered objects, which are not observed, when the scene is surveyed with a sensor without polarizing elements. This has earlier been shown in an application to detect surface laid personal mines. In this work measurement of objects covered by camouflage nets has been performed in the wavelength region 8-12 micro meters. Calculations of Stokes parameters from these measurements show that a polarization sensor can detect an object hidden behind a camouflage net, though it is not possible to detect the object, with a sensor without a polarizer. The same measurements and calculations have been done for the region 3-5 micro meters, but the results show that polarization measurements do not show an increased possibility to detect the object.