{HEAD ~ a pinhole plate} for receiving a first portion of the focused laser beam through the pinholes and, at the same time, reflecting {TAIL ~ a second portion} of the focused laser beam back to the focusing lens 
for reflecting
{ HEAD ~ a pinhole plate } for receiving a first portion of the focused laser beam through the pinholes and , at the same time , reflecting { TAIL ~ a second portion } of the focused laser beam back to the focusing lens
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH