According to Prof. Dr.-Ing. Matthias B. Hullin from University of Bonn, the camera uses diffusely scattered light and reconstructs the shape of objects outside of the field of view, and combined with a mathematical procedure, it enables to virtually transform this wall into a mirror. The laser dot on the wall is by itself a source of scattered light, which serves as the crucial source of information. Some of this light, in a roundabout way, falls back onto the wall and finally into the camera.
They are recording a kind of light echo from which the object can be reconstructed, using the special camera system Hullin has developed together with his colleagues at the University of British Columbia, which not only records the direction from which the light is coming, but also how long it took the light to get from the source to the camera. Hullin said, in principle, they are measuring nothing other than the sum of numerous light reflections which reached the camera through many different paths and which are superimposed on each other on the image sensor.
This problem, known as multipath interference, has been giving engineers headaches for a long time. Traditionally, one would attempt to remove the undesired multipath scatter and only use the direct portion of the signal. Based on an advanced mathematical model, Hullin and his colleagues, however, developed a method which can obtain the desired information exclusively from what would usually be considered noise rather than signal.
The accuracy of their method has its limits and the results are still limited to rough outlines, he added. However, the researchers assume that based on the rapid development of technical components and mathematical models, an even higher resolution can be achieved soon. Hullin will present the method at the international Conference for Computer Vision and Pattern Recognition (CVPR).