Fast approximate focal stack transform

In this work we develop a new algorithm, extending the Fast Digital Radon transform from Götz and Druckmüller (1996), that is capable of generating the approximate focal stack of a scene, previously measured with a plenoptic camera, with the minimum number of operations. This new algorithm does not require multiplications, just sums, and its computational complexity is O(N
⁴
) to achieve a volume consisting of 2N − 1 photographic planes focused at different depths, from a N
⁴
light field. The method is close to real-time performance, and its output can be used to estimate the distances to objects of a scene.