单缝衍射暗条纹中心距的精确测量

由于较高次衍射条纹的光强很微弱,以及激光的漫反射和CCD器件本身存在的暗电流噪声等原因,使得暗条纹中心距难以精确测量,这是单缝衍射法测量几何量中影响测量精度的主要原因。为此,提出了分步滤波法和暗条纹中心判定条件。对衍射条纹原始采集数据先进行过滤波,再进行欠滤波,尽量消除干扰信号的影响,获得有用信号;利用最小二乘法对衍射条纹曲线进行拟合,并利用二分搜索法对拟合曲线的波谷进行精确定位,就可较精确地得到暗条纹的中心位置。实验表明,暗条纹中心距的测量精度达到优于5μm的水平。

Precision measurement of the center distance of single slit diffracted dark stripes

Because of the feeble light intensity of higher sequence of diffraction stripes, the diffuse reflection of laser and dark current noise in CCD, the measurement of the center distance of dark stripes is difficult to carry out. And it is the main factor which affects the accuracy in measuring the geometrical quantity by single slit diffraction theory. So, batch fractional filtering and judgments of centers of dark stripes are proposed. The original acquisition data of diffraction stripes is processed by over-filtering first, then it is processed by deficient-filtering. They endeavor to eliminate the effect caused by interfering signal and obtain desired signal. Fitting curve of diffraction stripes is got by means of least square fitting. The wave troughs of fitting curve are precisely located by dichotomy search. So the central position of dark stripes can be got precisely. The measuring accuracy of center distance of dark stripes reaches the level better than five microns and it is proved by experiments.