  To obtain depth information from a stereo camera setup, a common way is to
conduct disparity estimation between the two views; the disparity map thus
generated may then also be used to synthesize arbitrary intermediate views. A
straightforward approach to disparity estimation is block matching, which
performs well with perspective data. When dealing with non-perspective imagery
such as obtained from ultra wide-angle fisheye cameras, however, block matching
meets its limits. In this paper, an adapted disparity estimation approach for
fisheye images is introduced. The proposed method exploits knowledge about the
fisheye projection function to transform the fisheye coordinate grid to a
corresponding perspective mesh. Offsets between views can thus be determined
more accurately, resulting in more reliable disparity maps. By re-projecting
the perspective mesh to the fisheye domain, the original fisheye field of view
is retained. The benefit of the proposed method is demonstrated in the context
of intermediate view synthesis, for which both objectively evaluated as well as
visually convincing results are provided.
