means for regulating {HEAD ~ the intensity} of {TAIL ~ the source} of laser light in response to the error signal, to thereby maintain the light intensity on the photo detector substantially constant, 
of
means for regulating { HEAD ~ the intensity } of { TAIL ~ the source } of laser light in response to the error signal , to thereby maintain the light intensity on the photo detector substantially constant ,
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH