Researchers from Stanford University and Cornell University have put together a projector-camera system that can read a playing card that is facing away from the camera.
The projector beams black and white pixels at a scene and the camera captures the way the light bounces off objects in the scene. A computer algorithm monitors the data and changes the patterns to gain the needed information.
For example, how can one read a playing card that is facing away from the camera? “In the card experiment, the camera cannot see the card directly, but it can see the surface of the book [behind the card]; the light from the projector bounces off the card, then bounces off the book and hits the camera,” said Pradeep Sen from Stanford University.
When the projector shines on a red part of the card the light gets a red tint. “The camera observes it and our algorithm determines that the projector saw something red at that position,” said Sen. “In this manner, we put together the projector image pixel-by-pixel and can see the card.”
The dual-photography technique could be used to relight movie scenes in five years. It will be 10 or 15 years before it is practical to work with the large data sets needed to use the technique to change the viewpoint of a movie scene after it has been filmed.