Along with intensity and color, polarization is a property of light that can provide useful information for scene analysis; however, the human eye and most cameras cannot detect polarization. Gathering polarization data could aid machine vision in detecting information about surfaces, material properties, shadows, and illumination sources. A camera that could easily incorporate polarization imaging could provide better detail and scene analysis than conventional cameras.
Researchers have created an image sensor with real-time polarimetric extraction capability at the focal plane. A micropolarizer array mounted on the imaging sensor filters the incoming light through two polarization filters offset at 45 degrees to each other. For each given 2 × 2-pixel area, both light intensity and polarization information are captured.
The data captured by the imaging sensor can be used to calculate the Stokes parameters that quantify the polarization of the light. A complete image sensor is made up of sets of these 2 × 2-pixel blocks, with the current prototype consisting of a 256 × 256 imager (see figure). A polarization imaging camera based on this design could provide additional data for scene analysis and computer vision using a property of light that is often ignored.