Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves. Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object. Plane polarized light: According to the wave theory of light, an ordinary ray of light is considered to be vibrating in all planes of right angles to the direction of its propagation. If this ordinary ray of light is passed through a nicol prism, the emergent ray has its vibration only in one plane. Applications Polarimetry of thin films and surfaces is commonly known as ellipsometry. Polarimetry is used in remote sensing applications, such as planetary science, astronomy, and weather radar. Polarimetry can also be included in computational analysis of waves. For example, radars often consider wave polarization in post-processing to improve the characterization of the targets. In this case, polarimetry can be used to estimate the fine texture of a material, help resolve the orientation of small structures in the target, and, when circularly-polarized antennas are used, resolve the number of bounces of the received signal (the chirality of circularly polarized waves alternates with each reflection). Imaging In 2003, a visible-near IR (VNIR) Spectropolarimetric Imager with an acousto-optic tunable filter (AOTF) was reported. These hyperspectral and spectropolarimetric imager functioned in radiation regions spanning from ultraviolet (UV) to long-wave infrared (LWIR). In AOTFs a piezoelectric transducer converts a radio frequency (RF) signal into an ultrasonic wave. This wave then travels through a crystal attached to the transducer and upon entering an acoustic absorber is diffracted. The wavelength of the resulting light beams can be modified by altering the initial RF signal. VNIR and LWIR hyperspectral imaging consistently perform better as hyperspectral imagers. This technology was developed at the U.S. Army Research Laboratory. The researchers reported visible near infrared system (VISNIR) data (.4-.9 micrometers) which required an RF signal below 1 W power. The reported experimental data indicates that polarimetric signatures are unique to manmade items and are not found in natural objects. The researchers state that a dual system, collecting both hyperspectral and spectropolarimetric information, is an advantage in image production for target tracking. Gemology Gemologists use polariscopes to identify various properties of gems under examination. Proper examination may require the gem to be inspected in various positions and angles. A