Günther,
Yes, I do get the same thing in your image if I really stretch it. It doesn't look like anything I've every seen caused by a camera. I suspect you have something happening in the optics, i.e.: a reflection, newton rings, etc.
Try shooting a flat with no lens on the camera; just aim the camera at a bright wall or use an EL panel over the end of the camera. I'd also take off the nosepiece to be sure it isn't causing a reflection. If the problem still exists, this would eliminate the optics and probably indicate something is truly wrong with the camera... But like I said, I've never seen this type of pattern caused by a camera.
bwa