The detection of camouflaged or hidden objects requires a measurement that provides a contrast between the object and background materials. Hyperspectral imagery is well suited to this application since the collected spectrum contains information related to the chemical makeup of materials. In addition, it is often possible to detect the presence of a target spectral signature in sub-pixel quantities when there is sufficient spectral contrast with background materials. Field collection of spectral signatures of both target and background materials is often critical to success since it is difficult to reproduce natural illumination conditions in a laboratory setting. Studies such as Bubner et al. (2001) have found significant discrepancies between field and lab measured spectral signatures with the largest differences seen for materials such as soils and vegetation whose spectral signatures are strongly dependent of the structure of the surface and where collection of the material significantly alters that structure.
One of the more widespread uses of camouflage is to mimic the spectral signature of vegetation. While the design of such a camouflage is relatively easy when the sensor is the human eye, if becomes increasingly more difficult with increasing spectral resolution and wavelength range of the imaging sensor. For the hyperspectral case, it is often possible to detect camouflaged objects that represent as little as 20% of a pixel (Bubner et al. 2001). This isn't surprising given that the dominant chemical makeup (pigments, water, cellulose, lignin) and complex three-dimensional structure of vegetation is nearly impossible to duplicate in a camouflage material.
Reference: T. P. Bubner, V. K. Shettigara, S. K. Kempinger (2001) An Investigation of Target Detection Ability Using Spectral Signatures at Hyperspectral Resolution. Defence Science and Technology Organisation (Australia) Electronics and Surveillance Research Laboratory, DSTO-TR-0807, pp. 47.