Panasonic patent application US20110316983 proposes to use parallax from polarization split lens to determine the distance to the object. The lens is divided by a polarization filter into two halves:
Then the sensor has some number of pixels which are selective to the polarization, so that they get signal from only the left or the right half of the lens. Here are the examples of polarization selective pixel placement (Wv and Wh stands for white pixel sensitive to vertical and horizontal polarization, respectively):
Then one can determine the distance from seeing the parallax between the image sensed by W, Wh and Wv pixels - a nice way to implement a passive 3D camera.