The focusing of light scattered from diffuse reflectors using phase modulation

摘要

“Indirect photography” was recently demonstrated for imaging hidden scene information through the collectionand radiometric modeling of light reflecting off of visible reflecting surfaces. The ability to focus the beam thatreflects off the visible surface to a tight spot on the hidden object is theorized to simulate a direct line of sightfrom the light source to the object, reducing the radiometric model to that of the previously demonstrated “dualphotography.” Experiments involving the focusing of light transmitted through highly scattering media havebeen adapted to the case of reflection. The focusing of a HeNe laser reflected off diffusely scattering surfaces toa tight spot is demonstrated using phase control. A liquid crystal spatial light modulator assigns pixelated phasedelay to the beam to conjugate the scattering properties of the reflector. Intensity enhancement values between13.8 and 122.3 are achieved for the surfaces studied. Samples with relatively strong specular reflection achievehigher enhancement for a given geometry. More diffusely reflecting materials achieve higher enhancement inregions of nonspecular scatter, facilitating non-mechanical beam steering.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.