{TAIL ~ A further object} is to provide {HEAD ~ a spot wobble defocusing scheme} for affecting the beam vertically while not affecting the beam horizontally 
{ TAIL ~ A further object } is to provide { HEAD ~ a spot wobble defocusing scheme } for affecting the beam vertically while not affecting the beam horizontally
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH