Calculation and hue mapping of AoP in polarization imaging

The value range of AoP (angle of polarization) is physically limited to [0, π]. However, for most programing languages such as Matlab and C/C++, the range of inverse tangent function is commonly limited to [-π/2, -π/2]. Therefore, this paper derives a practical formula for AoP calculation based on the inverse tangent function of common programming languages. Because AoP is a periodical function, the conventional gray image cannot effectively display the AoP levels. The hue component of HSV (hue, saturation and value) color space is also periodical. Therefore, this paper maps the AoP to hue component and then transforms HSV space to RGB space. Different AoP reference orientations will produce different false color displays. In our experiment, polarization images of a fishbowl scene are captured by a DoFP (division of focal plane) polarization camera, and a sequence of false RGB images with different reference orientations are produced.