二色调相式双折射系统的设计及其应用

以二色氩离子激光作光源,采用相调制技术设计了用于同时实时测量流场双折射及取向角的二色调相式流动双折射实验装置。由于采用了二色光源,避免了在计算过程中运用二阶贝塞尔函数以及在信号处理时分析二次谐波,简化了实验装置及结果计算。装置通过低通滤波电路和锁相放大器分别测量入射光和出射光中基频成分的光强度,并把它们转换成数字信号,由此计算出待测流场的双折射和取向角。实验证明,应用该装置同步测量了双折射及取向角,最大测量误差控制在0.5%~1%。

Design of Two-color Phase-modulated Birefringence Experiment and Its Application

A two-color phase-modulated birefringence equipment,used for the simultaneous and real-time measurement of birefringence and orientation angle of flow field,was designed using a two color argon-ion laser as light source coupled with the phase-modulate technology.The involvement of second-order Bessel function in the calculation and analysis of second harmonic component in signal processing were avoided for the reason of a two-color laser used as light source,so the calculation and the process of experiment became simplified.Low filter circuits and lock-in amplifiers were used to measure the intensities of the incident light and the fundamental component of emergent light respectively,then the analog signals of light intensities were changed to digital signals,and thus the calculation of birefringence and orientation angle was achieved.It has been proved by experiments that this apparatus can accurately measure the birefringence and orientation angle simultaneously,where the maximum measurement errors are 0.5%~1%.