An optoelectronic method for standardization of laser Doppler (LD) instruments is proposed and tested. The optoelectronic standardization is based on detection of modulated near-infrared light from a light emitting diode (LED) emitted into the optic probe (detecting fiber) of the LD instrument. Changes of the frequency and amplitude of the light enables evaluation of the sensitivity and linearity of the instrument response. Measurements of the LD instrument response show linear increase of perfusion signal with the modulation frequency of light. Analysis of the LD signal components (flux, speed, concentration) show that for fixed amplitude and varying frequency of the modulation, the flux and speed are linearly related to the frequency and the concentration is constant. The linear increase of flux and concentration signals was observed for increasing amplitude of modulation with fixed frequency. The proposed technique allows for automatic evaluation of the instrument response.
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Liebert et al. (1999) studied this question.
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