lens creation function aufgerÃaeumt, beispiel fur fft angepasst (gerade fehler drin, verstaerkung geht nicht

added interpolator, special for surface only! faster than general interpolator, especially helpfor for interpolation of surface deformation

trilinear interpolation for grids available, but doesn't always give good results. needs to be improved

increased efficiency of iterpolator. trilinear interpolation not worth it, as it increases computational effort quiet a lot, while barely being more accurate