Range-gated imaging in turbid conditions using a combination of intensity and polarization information

Polarization of light is introduced into range-gated imaging (RGI) for target detection and recognition in turbid conditions. The polarimetric RGI system can obtain both intensity and polarization information on objects. The experimental results show that an intensity-based image, when the target part and the background part of an object have similar reflective characteristic, can reveal the contours of the object by minimizing the effect of backscattering from the medium, and a polarization-based image can highlight the target part by common-mode rejection of the background. Furthermore, intensity and polarization components are combined to describe the scene systematically. Four methods-Laplacian pyramid, discrete wavelet transform, contourlet transform and nonsubsampled contourlet transform-are used for image fusion. Favourable information represented in each image can be extracted from image fusion for target detection and recognition. Objective evaluation indices are applied to compare the performance of different image fusion methods.