This paper discusses a self-mixing interferometry method for measuring distances upon sawtooth modulation of the wavelength of laser radiation. Conditions under which the distance obtained from the spectrum of the modeled autodyne signal coincides with the distance specified in computer simulation are determined. The limiting capabilities of the method are theoretically substantiated for the increased range of deviations of the laser wavelength. The estimation of the limiting capabilities of the distance measurement method on the spectrum of the autodyne signal gives 10 microns at a wavelength of 650 nm at a 5-nm deviation of laser radiation wavelength. We also discuss difficulties of attaining the limiting accuracy of distance measurements associated with the nonlinear dependence of the wavelength emitted by a laser diode on its supply current and the need to analyze the self-mixing signal at high frequencies.
The results of measuring the derivative of the pulse wave using a laser autodyne based on the Fourier analysis of the low-frequency spectrum of the interference signal are presented. The features of using the windowed Fourier transform for window types and window widths are discussed. The correlation coefficient between the derivative obtained by direct differentiation of the sphygmographic signal and the frequency dependence of the windowed Fourier transform obtained from the analysis of the interference signal is calculated. It is shown that the amplitude of biovibration of the skin surface has the greatest influence on the correlation of the frequencies of the window spectrum of the autodyne signal with direct measurements of the pulse wave parameters by the sphygmographic method. Using a hardware-software system, we measured the sphygmogram of the pulse wave in the radial artery in a 19-year-old man who did not suffer from cardiovascular diseases. The derivative of the pulse wave obtained from the sphygmogram was compared with the dependence of the frequencies of the window spectrum of the autodyne signal. A comparative analysis of the dependences of the frequencies of the spectral harmonics of the window method with the derivative of the sphygmographic pulse showed a good correlation at the amplitudes of biovibration of the skin surface exceeding 10 μm.
Скрипаль Анатолий Владимиро вич, доктор физико-математических наук, профессор, заведующий кафедрой медицинской физики, Саратовский национальный исследовательский государственный университет имени Н. Г. Чернышевского,
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