介绍双螺旋叠栅条纹检测光束准直性的基本原理,进一步就双螺旋叠栅条纹的特征参量与被测光束发散角(即光束准直精度)的关系进行分析和推导。在分析双螺旋叠栅条纹进行时,首先采用频域低通滤波提取纯叠栅条纹,然后提取纯叠栅条纹的特征参量。提出两种特征参量的提取方法,一种依次进行傅里叶变换计算相位信息的傅里叶变换方法,另一种是受传统时间相移算法启发而提出的空间相移算法,讨论了在两种方法中极坐标的重采样问题和相应的计算公式,并进行了计算机模拟。结果表明,傅里叶变换方法和空间相移算法实质都是获取叠栅条纹全场趋势的平均值,使最终光束发散角的检测具有很高的精度,对自成像条纹周期的检测误差在±2.8‰以内。

The basic principle to check light beam collimation with double spiral moiré fringes is illustrated, and the relationship of the characteristic parameters of double spiral moiré fringes and the angle of divergence, i.e. collimation accuracy, is further deduced and analyzed. In the double spiral moiré fringes analysis, the pure moiré fringes are extracted by low-pass filter in the frequency domain at first, and then the characteristic parameter of the pure moiré fringes is extracted. Two methods are introduced to extract the characteristic parameter, one is Fourier transform algorithm, in which the phase information is derived by Fourier transform in turn, and another is spatial phase shift arithmetic, enlightened by the traditional temporal phase algorithm. The problems of re-sampling in polar coordinates and relevant formulae in the two methods are also discussed, and the results of computer simulation are presented. The result shows that the essence of the above two methods is acquisition of the average of the whole moiré fringes trend, and at last the angle of divergence is obtained with a high accuracy. The error of the fringes period of selfimaging is within ±2.8‰.