From http://www.michaelbach.de/ot/index.html : “This image is called “Out of Focus”. It leads to a seeming shift of the central disk with respect to the surround. It is very effectively provoked by the eye movements occurring during reading. So, while you are reading this cast your “inner eye” on the image and watch for a seeming decoupling of disk and background. You may also observe that the disk floats above the background“ --
