In an alternative embodiment of the invention, this difference voltage is continuously sensed and compared with a reference voltage for producing {HEAD ~ a signal} for operating {TAIL ~ a servo motor} that is operative to lock in the focal spot size during an exposure 
for operating
In an alternative embodiment of the invention , this difference voltage is continuously sensed and compared with a reference voltage for producing { HEAD ~ a signal } for operating { TAIL ~ a servo motor } that is operative to lock in the focal spot size during an exposure
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH