Electro-optic (EO) imaging systems are commonly used to detect civilian and military targets during surveillance operations and search and rescue missions. Adding the polarization of light as additional information to such active and passive EO imaging systems may increase the target discrimination performance, as man made objects are known to depolarized light in different manner than natural background. However, while the polarization of light has been used and studied in the past for numerous applications, the understanding of the polarization phenomenology taking place with targets used in cluttered backgrounds requires additional experimentations. Specifically, the target contrast enhancement obtained by analyzing the polarization of the reflected light from either a direct polarized laser source as encountered in active imagers, or from natural ambient illumination, needs further investigation. This paper describes an investigation of the use of polarization-based imaging sensors to discriminate civilian and military targets against different backgrounds. Measurements were carried out using two custom-designed active and passive imaging systems operating in the near infrared (NIR) and the long-wave infrared (LWIR) spectral bands. Polarimetric signatures were acquired during two distinct trials that occurred in 2007, using specific civilian and military targets such as cars and military vehicles. Results demonstrate to what extent and under which illumination and environmental conditions the exploitation of active and passive polarimetric images is suitable to enable target detection and recognition for some events of interest, according to various specific scenarios.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.