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