A large number of 3D cameras suffer from so-called holes in the data, i.e. the measurement lattice is affected by invalid measurements and the range image has undefined values. Conventional image filters used for removing the holes perform not well in presence of holes with large varying hole sizes. The novel hole-filling method presented in this paper operates on reliability attributed range images featuring unwanted holes with wide varying sizes. The method operates according to a multi resolution scheme where the image resolution is decreased at the same time as the range reliability is successively increased until sufficient confidence is reached. It builds on three main components. First, the described process performs a weighted local neighbourhood filter where the contribution of each pixel stands for its reliability. Second, the filtering combines filters with different kernel sizes and implements therefore the multi resolution schema. Third, the processing requires a complete travel from high resolution down to the resolution of satisfactory confidence and back again to the highest resolution. The algorithm for the described method was implemented in a efficient way and was widely applied in the hole-filling of range images from a depth from focus process where reliability is obtainable non-linearly from the local sharpness measurement. The method is valid in a very general way for all range imagers providing reliability information. It seems therefore well suited to depth cameras like time-of-flight, stereo and other similar rangers.
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