Oliinyk O. Microscope measurement sensitivity increase for nonstationary photoelasticity research in electronic materials

The thesis is devoted to improving of modulation-polarization method for mechanical stress registration by increasing the measurement sensitivity of birefringence created by non-stationary processes in electronic materials. The modeling and technical implementation of photoelastic microscope is made on the base of nonstationary photoelasticity research in electronic materials to measure the birefringence values in them. The calculation method of the surface and internal mechanical stresses is described. Practical application of photoelastic microscope is demonstrated as mechanical displacement measurement of photoelastic bar with internal changes in refractive index. On the base of he modulator noise spectrum, thermal, structural, and other noises calculations it is shown that thermal noise, amplifier noise and low frequency vibration are the dominant. For linear and circular modulation of laser radiation components photoelastic modulator is used. To increase the sensitivity of the signal registration an optimal correlation filter is synthesized, which simultaneously perform lock-in detection of reference and useful signals under background noise. Equations that describe the S/N ratio in the output of photoelastic microscope are obtained as well as methodological and instrumental error. For mechanical stresses measurements and search of irregularities in optical materials it is made the comparative analysis of modulation polarization devices and designed photoelastic microscope.