针对开环相移驱动下的单色光干涉测量, 提出一种满足四步法的高精度相位识别的方法。首先选取干涉场中存在适当相位差的两像素点, 建立相移驱动单周期内两像素点灰度序列值之间的干涉方程组。运用椭圆拟合获取相应干涉方程组参数, 然后通过反算序列相位确定逐点驱动步长或序列相位信息。结合序列相位信息, 运用Lagrange抛物插值算法, 设计计算满足四步法的4幅干涉图, 并计算各像素点的初相位。最后, 运用多波长算法计算表面形貌并进行误差分析。实验表明: 计算得到的方波多刻线样板的Ra值为0.439 0 μm, 测量误差为0.23%,此方法降低了对测量条件的硬件与环境要求, 满足表面形貌高精度测量的要求。

For monochromatic light interferometry under open-loop phase shifter, a high precision method for phase recognization was developed to satisfy four-step phase-shift algorithm. Firstly two pixels with suitable phase-difference were selected from the interference field, and the interference equations of the two pixels’ gray values were established in one phase-shifting cycle. Secondly, the interference equations’ parameters could be obtained by using ellipse fitting algorithm, and the point-to-point driven step length and sequence phases could be determined through back calculation of sequence phases. Then four interference gray scales meeting the four-step phase-shift algorithm were designed and calculated through Lagrange parabolic interpolation, which were used to calculate the initial phase of every pixel. Finally, the surface topography was calculated through multi-wavelength algorithm and the measurement errors were analyzed. Experimental results show that the Ra value of square wave specimen with multiple grooves is 0.4390μm, and the measurement error is 0.23%. This method decreases the requirement for hardware and environment. It can meet the high precision demands of surface topography measurement.