Image reconstruction using polarized light

Polarization image of a model airplane

In this short research endeavor, I developed a proof of concept showing that information not currently used by optical sensors (cameras) has the potential to render better images. An immediate application that comes to mind is surveillance.

Regular cameras capture only natural light to form an image, but much more information is present in the polarized part of light. The study suggests that under lighting condition where no image can be formed by the human eye or regular cameras, polarization cameras form qualitatively better images. Furthermore, using superposition of the angle of polarization with the degree of polarization we often get an even better image of the object.

As an example, consider the following four pictures of a model airplane. The leftmost picture was taken with a regular camera, the Canon Rebel T3. The rest of the images are taken with a sensor capable of capturing the polarization of light, which we process and reconstruct to form the image. We first superimpose the degree of polarization of light reflecting from the object. In the next image, we superimpose the angle of polarization, and lastly, we reconstruct the image as we superimpose both the degree and angle of polarization.

Model airplane as seen in natural light
An image taken with a regular camera.
Model airplane as seen with Degree of polarization
Image reconstruction, using degree of polarization.
Model airplane as seen with Angle of polarization
Image reconstruction, using angle of polarization.
Model airplane as seen using Composite polarization
Image reconstruction, adding both the degree and angle of polarization.
 
As can be seen, the rightmost picture above gives a human observer enough details to be perceivable, almost to the point that the picture could be mistaken for taken in daylight.

The next challenge we researched was the ability to use polarized light for text reconstruction. Using the same equipment and image reconstruction algorithm, we took a picture of a cup, on which text was printed. We show again, from left to right, the progression of the image reconstruction.

Model airplane as seen in natural light
Regular camera.
Model airplane as seen with Degree of polarization
Degree of polarization.
Model airplane as seen with Angle of polarization
Angle of polarization.
Model airplane as seen using Composite polarization
Composite polarization.

  In the rightmost picture, even the small pores of the bricks from which our lab wall is build are perceivable.



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