Search

We report the results of theoretical and experimental studies of a digital system for regulating and stabilising the frequency of a four-frequency Zeeman laser gyroscope (ZLG), in which generation occurs simultaneously on two longitudinal modes with orthogonal circular polarisations; therefore, four light waves propagate in the optical ring resonator. In contrast to a two-frequency Zeeman laser gyroscope, a four-frequency ZLG does not use the intensity modulation signal of one of the light waves, which appears when an alternating magnetic field is applied to the active medium, to analyse the frequency detuning of longitudinal modes from the centre of the active-medium gain contour. At the same time, it is possible to construct a digital perimeter adjustment system (PAS), which allows the resonator perimeter to be adjusted so that the magnetic components of the zero drift of the gyroscope for two longitudinal generation modes are equal and opposite in sign. Due to this, almost complete compensation for the magnetic component of the zero drift of the gyroscope is realised in a four-frequency ZLG. The use of the digital system makes it possible to provide a higher accuracy of the resonator perimeter adjustment than that in a two-frequency ZLG, even with a relatively small bit capacity of the PAS digital-to-analogue conversion (DAC), and to fully take advantage of the capabilities of a four-frequency ZLG to reduce the magnetic sensitivity.

Application of a ring laser to determine the directions to the poles of Earth's rotation is considered. The maximum accuracy of determining the directions is calculated, physical and technical mechanisms that limit the accuracy are analysed, and the instrumental errors are estimated by the example of ring He - Ne lasers with Zeeman biasing. (laser applications and other topics in quantum electronics)

An analysis is reported of various configurations of the Sagnac interferometer, in particular a fiber ring interferometer converting an optical phase shift to the rf range. It is shown that this interferometer may exhibit a high linearity of the output characteristics without recourse to frequency splitting, but the processes occurring in modulation–demodulation systems result in an instability and nonlinearity of the output characteristics of the interferometer. An interferometer with an angular velocity resolution of the order of 10 − 5 rad/s was used to show that the nonlinearity of the output characteristic of the interferometer used to convert the optical phase shift to the rf range amounted to 10 − 2, which was approximately an order of magnitude poorer than the corresponding parameter obtained for a coarse laser sensor of the angular velocity.

Today the noninvasive (in vitro, in situ) and real-time methods of diagnostics are desirable for general clinical practice. One of such promising technique is the optical multi-wave diffusion and absorption spectrophotometry. It allows a doctor to measure a number of important medical and biological (M&B) parameters such as the blood microcirculation parameters into the soft tissues, contents of the hemoglobin fractions into the periphery blood, etc. The use of the new components of the microelectronics and optics and development of new approaches to the diagnostic data processing makes it possible to design a number of small and effective devices for this purpose. The basic principle of work of them in means of hardware function is the multi-wave light scanning of the tested tissue’s area and detecting a backscattered light. In means of software function the basic principle of work of them is the inverse optical task solution when the optical and corresponding M&B parameters of the tested medium are calculated from the measured backscattered spectral optical data. This report presents one of such designed portable apparatus “Spectrotest” developed in cooperation with Moscow Regional Research and Clinical Institute of “MONIKI”. This device allows a doctor to register the index of melanin pigmentation of the skin, the volume of the blood in the tested tissue and the average hemoglobin saturation of the peripheral blood. All this parameters are available for a doctor to see them on the monitor screen in real-time mode directly during any diagnostic or treatment procedure. For that a new modified light scattering theory with the analytical solution of the main equations has been developed. Analytical solution allows the software to calculate and indicate the measured M&B parameters on the computer’s monitor screen during less than one second. Today the developed diagnostic system “Spectrotest” is used in real clinical practice in “MONIKI” and in the Oncology Center of the Russian Academy of Medical Science for the medical research aims. The general hardware and software composites of this diagnostic apparatus and examples of the application of it for the functional diagnostic tests are presented in this report as well.