Temperature compensation for the photoelastic modulator with a digital phase-locked loop

For temperature drift in the ultra-high speed photoelastic modulation interferometer, a control model with temperature compensation is presented including the voltage and phase compensation. First, according to the similar and modeling theory, an equivalent circuit of mechanical properties of the ultra-high speed photoelastic modulation interferometer is established. The impact on its resonance frequency is analyzed which is caused by temperature drift. And a mathematical model which contains drive voltage, frequency and resonance frequency is set up. Then, a design method including the voltage and phase compensation is given for optical path difference deviation control, which merges the digtal phase lock loop and the phase compensation. Finally, the test between a drive control system including voltage and phase compensation and a traditional drive control system is executed, using a laser doppler vibrometer to record the amount of change of optical path difference within 3 hours. Results show that the optical path difference deviation caused by temperature drift in long terms is reduced by about 50%.