Noise suppression and correction of laser Doppler blood flow spectra after high-pass filtering

摘要

Abstract: Laser Doppler flowmetry (LDF) is a method that can beused for measuring blood flow changes in themicrocirculation. We have contributed to thedevelopment of a new device for LDF, based on digitalsignal processing. A method for correcting thedisregarding of frequency components was developed, byapproximating the noise-free Doppler spectrum with anexponential shape. The frequency components from 40 kHzto 50 kHz can be used to correct for white noise. Weintroduced variable resistors for the case common modecomponents from both detectors have differentmagnitudes. However, after adjustment we found thatnoise may still be present. We have observed, thatcutting off at 150 Hz suppresses many noisecontributions and still provides sufficient Dopplerinformation. For the transfer of a moment calculatedfrom 150 Hz - 20 kHz into 0 - infinity Hz, thecorrection method mentioned above can be applied. !7