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波长移相干涉仪可用于大口径光学元件的测试。其移相量需经过标定方可采用定步长移相算法计算相位分布。在长腔长测试条件下,由于激光器的波长调谐驱动源的精度有限,采用定步长移相算法求解相位分布的精度不高。在分析干涉腔长和波面计算误差的基础上,提出了一种自适应相位筛选计算方法。根据电压-相位标定曲线采集多组周期干涉图,对干涉图中的光强值进行均匀分布抽样后,对其进行随机移相计算,求取每帧干涉图精确的步进移相量,从中筛选出移相量为π/2的四帧干涉图,利用四步移相计算公式求得精确的相位分布。实验结果表明,在波长移相干涉仪中运用该方法,可以很好地解决长腔长测试条件下的相位计算问题,与未进行筛选的计算结果比较,其测试精度得到了显著提高。
Wavelength phase-shifting interferometers can be used for testing large-aperture optics. The phase shift should be calibrated before using the step-by-step phase shift algorithm to calculate the phase distribution. Under the condition of long cavity length, the precision of the phase distribution is not high because of the limited accuracy of laser wavelength tuning drive source. On the basis of analyzing the calculation error of the interference cavity length and the wavefront, an adaptive phase filtering method is proposed. According to the voltage-phase calibration curves, multiple sets of periodic interference graphs are collected. After the light intensity values in the interference graphs are uniformly distributed and sampled, they are randomly phase-shifted to calculate the exact step-by-phase phase shift amount of each interferogram. Four interferograms with phase shift of π / 2 are screened, and the exact phase distribution is obtained by using the four-step phase shift calculation formula. The experimental results show that this method can be used to solve the problem of phase calculation under the condition of long cavity length. Compared with the results without filtering, the testing accuracy is greatly improved.