Matrix Determination of Reflectance of Hidden Object via Indirect Photography

摘要

Indirect photography is a recently demonstrated technique that expands on the principles of dual photography and allows for the imaging of hidden objects. A camera and light source are collocated with neither having line-of-sight access to the hidden object. Light from the source, a laser, is reflected off a visible non-specular surface onto the hidden object, where it is reflected back to the initial non-specular surface and collected by the camera. This process may be repeated numerous times for various laser spot positions to yield slightly different camera images due to a variation in the illumination of the object. These images can then be used to construct an 'indirect' image of the hidden object. This work provides an alternative method of processing the camera images by modeling the system as a set of transport and reflectance matrices. This approach reduces the required size of the visible scattering surface. Matrix formulation and those parameters shown in simulation to improve indirect image quality as measured by a modified MTF, including the method of matrix inversion and number and pattern of laser spots, are discussed.