The problem ofmine and minefield detection continues to provide a significant challenge to sensor systems. Although the various sensor technologies (infrared, ground penetrating radar, etc.) may excel in certain situations there does not exist a single sensor technology that can adequately detect mines in all conditions such as time of day, weather, buried or surface laid, etc. A truly robust mine detection system will likely require the fusion of data from multiple sensor technologies. The performance of these systems, however, will ultimately depend on the performance ofthe individual sensors.Infrared (IR) polarimetry is a new and innovative sensor technology that adds substantial capabilities to the detection of mines. JR polarimetry improves on basic JR imaging by providing improved spatial resolution ofthe target, an inherent ability to suppress clutter, and the capability for zero iT imaging. Nichols Research Corporation (Nichols) is currently evaluating the effectiveness of JR polarization for mine detection. This study is partially funded by the U.S. Army Night Vision & Electronic Sensors Directorate (NVESD). The goal of the study is to demonstrate, through phenomenology studies and limited field trials, that JR polarization outperforms conventional JR imaging in the mine detection arena.
High spatial frequency metal gratings have long been recognized as an effective polarizer option for the infrared portion of the spectrum.1 Numerous applications can benefit from the development of arrays of such wire-grid polarizers in which subsets of the polarizers have arbitrary angular orientations. In this paper we describe the design and fabrication of an array of small aperture polarizers (i.e., micropolarizers) for the 3-5 μm wavelength range.
Nichols Research Corporation is currently developing innovative imaging polarimetric sensors for a number of applications such as mine and minefield detection, aircraft ice detection, and remote sensing. The wave bands in which the various sensors operate include the visible, mid-wave infrared (IR), and long-wave IR bands. This paper will summarize the current research that Nichols is conducting in the field of remote sensing using imaging polarimetric cameras. The polarization signatures of various targets, acquired from ranges up to 10 kilometers, will be presented for all three wave-bands. The benefits obtained using polarimetric imaging will be discussed along with potential applications for this innovative technology including possible astronomical observation applications.
Rayleigh scattering has been investigated in an effort to develop a nonintrusive diagnostic for electric-field strength at moderate (~1 atm) to high pressures. Both experimental and theoretical studies have been made, with experiments conducted on He, Ar, N2, CO2 C4, Kr, and air, and with theory confined to He. In all cases, the Rayleigh signal decreased with increasing applied field strength. However, no depolarization due to the applied field was found. Thus, although the effect appears to be applicable to any gas, there is no obvious means of separating electric-field effects from changes in the gas density. The measurement is most sensitive in a right-angle scattering configuration. At field strengths of 60 kV/cm, ~1 J of light energy is required to make a measurement. The largest effect was seen in neon, in which the electric field-induced differential cross section is 4 × 10−32 cm2/(kV)2 sr; the cross section for air is 3.5 × 10−32 cm2/(kV)2 sr. Calculations of the effect have been made using quantum perturbation theory and extended tables based on the Coulomb approximation. These calculations agree with the general behavior of the experimental results and give oscillator strengths for Stark-induced forbidden transitions as well.
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