Methods and apparatus for investigation of volume change dynamics of physiologically active samples

A method of investigation of volume change dynamics of physiologically, active samples exposed to a source of visible radiation comprising:

• splitting a source beam of monochromatic highly coherent radiation produced by a laser source two mutually perpendicular beams on the first beam splitter, of which the measuring beam falls via an adjustable mirror on a reflective target with highly reflective surface, which is in mechanical contact with the surface of the measured sample, and the reference beam falls on a fixed reference reflective mirror, after reflection and backward pass through the first beam splitter the measuring beam and the reference beam interfere,
• determining the transversal change of the measured sample surface position as a consequence of its volume change from the phase difference of the harmonic waves in the interfering radiation beam,
• splitting the beam of interfering radiation into two detection beams on a second beam splitter, where the first detection beam passes through the first converging lens and falls simultaneously on the first photodetector and on the second photodetector, while the photodetectors are mutually phase-shifted by 90° in the interferogram, and the second detection beam, perpendicular to the first detection beam falls on the third photodetector, which scans the whole interference pattern, while the detection beams before falling on the photodetectors pass through absorbers of diffuse radiation, formed by cylindrical tubes whose length is an order multiple of the length of the photodetectors,
• wherein the signals from the photodetectors lead to the processing unit, connected to a computer via an interface and the signals from the photodetectors lead to the basic module in the measuring unit, where the third reference photodetector after being processed in the amplifier gives the mean value of the radiation intensity as the reference level in the reference signal, and the signals from the first photodetector and the second photodetector are, after processing in amplifiers and after suppressing of the noise signals by the low-pass type active filters are transferred to symmetric alternating signals with suppressed direct component by the reference signal,
• separating the alternating component of the second photodetector signal by a signal shaper,
• taking samples of alternating signals from the first photodetector and from the second photodetector by the controlling and sequential circuit,
• transmitting the controlling signals for the sampling amplifiers to eliminate disturbing effects, and
• measuring with high amplitudes and voltage corresponding to the frequency of the noise signals on the output from the controlling and sequential circuit, while the basic module is connected to the computer through three A/D converters and the interface.