Focus Range Sensors

Structures of dynamic scenes can only be recovered using a real-time range sensor. Focus analysis offers a direct solution to fast and dense range estimation. It is computational efficient as it circumvents the correspondence problem faced by stereo and feature tracking in structure from motion. However, accurate depth estimation requires theoretical and practical solutions to a variety of problems including recovery of textureless surfaces, precise blur estimation, and magnification variations caused by defocusing. Both textured and textureless surfaces are recovered using an illumination pattern that is projected via the same optical path used to acquire images. The illumination pattern is optimized to ensure maximum accuracy and spatial resolution in computed depth. A prototype focus range sensor has been developed that produces up to 512×480 depth estimates at 30 Hz with an accuracy better than 0.3%. In addition, a microscopic shape from focus sensor is described that uses the derived illumination pattern and a sequence of images to recover depth with an accuracy of 1 micron. Several experimental results are included to demonstrate the performances of both sensors. We conclude with a brief summary of our recent results on passive focus analysis.