means for producing {HEAD ~ an electrical signal} in the photodetector having a frequency component proportional to {TAIL ~ the blood cell velocity} in response to autodyne beating of Doppler shifted and non Doppler shifted radiation signals 
means for producing { HEAD ~ an electrical signal } in the photodetector having a frequency component proportional to { TAIL ~ the blood cell velocity } in response to autodyne beating of Doppler shifted and non Doppler shifted radiation signals
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH