Research Of Polarization State Measurement Based On Polarized Light Interference

The light polarization state(LPS)will be modified when light is reflected or transmitted from object.The measurement of LPS can provide the information of surface characteristics,internal refractive index change or even the distribution of micro molecules.Thus the detection of LPS can be used to research object's response to light and its micro mechanism,and it plays an important role in the biology,medicine,agriculture,communication etc.In this thesis a polarization interference method based on crystal wedge is proposed to measure full polarized light.The principle is that phase difference and angle of amplitude ratio of the detected polarized light are respectively encoded into interference fringes,and furthermore the polarization state is measured through measuring stripe position.The polarization interference method is simple and compact setup and insensitive to light power fluctuation.And more significantly,the single-shot setup without modulating optic devices is helpful to realize the real-time LPS measurement.The main works of this thesis are as follows:1.Jones matrix theory is used in theoretical derivation,simulation and error analysis on the principle of polarization interference method detecting phase difference and amplitude angle.The simulation results of phase different and amplitude angle of any polarized light detected by polarization interference method agree with their theoretical value,which verifies the feasibility of the proposed method.By means of the error analysis,the measuring error of amplitude angle is big when ? is equal to 90° or about 90°;phase modulation disappear and phase difference cannot be measured when polarized plane of linear polarized light parallels to optic axis of crystal wedge,the applicable range is obtained.2.According to measuring principle,experimental setup of polarization interference method is built;Labview program is used in interference image acquisition with median filter and valleys searching algorithm,which improves the measuring precision.3.The paper makes experimental verification on detecting phase difference and amplitude angle of polarization state by polarization interference method,and the experiment results are all under the allowing range of error,which confirms the reliability and accuracy of polarization interference method.4.Polarization interference method is used to obtain half-wave voltage of Lithium Niobate crystal through measuring phase difference of transmission polarized light from the crystal.The determined result is V? = 480 V with experimental error of 0.10%.Compared with experimental error of 0.96%in traditional extremum method,the measuring error of polarization interference method is reduced obviously.5.Polarization interference method is used to analyze polarization state of transmission polarized light from Twisted Nematic Liquid Crystal.Furthermore the dynamic measurement of the liquid crystal molecule mean director is implemented.The experiment results indicate that the response time of torsion angle and tilt angle reduces with the voltage increasing,and response time of torsion angle is faster,which agrees with the results derived by dynamical equation.Measured total torsion angle is 85.3° and determined pretilt angle 6.3°.