Dual diode transducer for laser Doppler skin blood velocimeter

Two parallel, oppositely placed photo-diodes were used to measure the scattered coherent light in the laser Doppler velocimeter used for skin blood flow measurements. The dual-diode arrangement effectively rejects the noise due to mode interference in the laser cavity and 50 Hz pick-up. During clinical tests, the skin blood velocity obtained by the transducer was compared with the results yielded by the conventional single-diode device.