通过相移条纹图差分测定相移量的方法

提出一种通过两幅相移条纹图相减来确定它们之间相移量的方法,进行了理论分析和实验验证。两幅相移条纹图相减并归一化后,得到的相移差分函数是振幅只与相移量有关的正弦函数,可以通过确定该函数最大极值的方法得到振幅,进而计算出相移量。介绍了极值直接查找法和平均法两种实现最大极值测量的方法。由于不使用傅里叶变换,减少了运算时间,既可以用于高空间频率条纹,也可以用于稀疏平行条纹,以及任意花样的条纹。在衬比度因子确定后,用这种方法就能够直接在空域内确定两幅条纹图之间的相移量,通过大量采样点进行统计计算,使结果达到很高的精度。将所得到的结果与用傅里叶变换方法得到的结果进行了比较,表明两种方法得到的结果具有完全相同的精度。

A Method of Phase-Shifting Measurement by the Difference of Phase-Shifting Interferograms

A method of phase-shifting measurement of interferograms is proposed by the difference between two interferograms.In this method a phase-shifting interferogram is subtracted from the other one,and then the phase-shifting difference function,in which the amplitude is correlated only with the phase-shifting value,is obtained and normalized,so the phase-shifting value can be calculated by the maximum extremum of phase-shifting difference function,meanwhile two metheds including the direct search method and the average method are introduced to determine the maximum extremum of the normalized function.Experimental and analysis results show the phase-shifting value between two interferograms can be obtained when contrast function of interferogram is determined and the results are not affected by the measured phase.And as a statistical analysis for many sampling points in spatial domain is used in calculation,the high-precision phase-shifting measurement can be achieved.For another,as Fourier transform is not used in above proposed method,and it can be used in analyzing the high spatial frequency fringes,sparse parallel fringes,even arbitrary form fringes.Meanwhile the measuring precision of the proposed method is compared with that of Fourier transform method,and it is proved the measuring precision of two methods is identical.