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Fifth International Conference on Computer Vision (ICCV'95)   p. 995
Real-time focus range sensor
S.K. Nayar, Dept. of Comput. Sci., Columbia Univ., New York, NY, USA
M. Watanabe, Dept. of Comput. Sci., Columbia Univ., New York, NY, USA
M. Noguchi, Dept. of Comput. Sci., Columbia Univ., New York, NY, USA

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DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/ICCV.1995.466826
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Abstract
Structures of dynamic scenes can only be recovered using a real-time range sensor. Depth-from-defocus offers a direct solution to fast and dense range estimation. It is computationally 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 the 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 the computed depth. The relative blurring in two images is computed using a narrow-band linear operator that is designed by considering all the optical, sensing and computational elements of the depth-from-defocus system. Defocus-invariant magnification is achieved by the use of an additional aperture in the imaging optics. A prototype focus range sensor has been developed that produces up to 512/spl times/480 depth estimates at 30 Hz with an accuracy better than 0.3%. Several experimental results are included to demonstrate the performance of the sensor.
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Index Terms- real-time systems; optical focusing; distance measurement; image sensors; image restoration; image texture; lighting; image processing equipment; real-time focus range sensor; dynamic scene structure recovery; depth-from-defocus system; dense range estimation; computational efficiency; accurate depth estimation; textureless surfaces; blur estimation; magnification variations; textured surfaces; illumination pattern; optical path; spatial resolution; relative image blurring; narrow-band linear operator; defocus-invariant magnification; aperture; imaging optics; performance; 30 Hz Citation:  S.K. Nayar, M. Watanabe, M. Noguchi, "Real-time focus range sensor," iccv, p. 995,  Fifth International Conference on Computer Vision (ICCV'95),  1995