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利用Ronchi光栅的Talbot效应和Moiré条纹测量长焦透镜焦距,根据焦距与莫尔条纹斜率之间的定量关系可求得透镜焦距.分别采用Canny算子和形态学方法对光栅的栅线中心进行像素级定位,再用高斯曲线拟合对其进行亚像素定位.经过对标准条纹的标定,验证了该方法的条纹中心定位误差小于0.1个像素.采用光栅作为系统的自基准对CCD像素当量进行了亚像素标定,为条纹斜率和宽度的计算提供了可靠的测量基准,经过计算,采用这些数据计算的焦距误差为0.10%.
The focal length of telephoto lens was measured by Talbot effect and Moiré stripe of Ronchi grating, and the focal length of the lens was obtained according to the quantitative relationship between the focal length and the slope of Moiré fringes. The centers of raster lines were calculated by Canny operator and morphological method respectively. Level positioning and sub-pixel location by Gaussian curve fitting.After the calibration of standard streaks, it is verified that the streak center localization error of this method is less than 0.1 pixels.Grid is used as the self-reference of the system for CCD pixel equivalent Sub-pixel calibration provides a reliable benchmark for the calculation of fringe slope and width, and the calculated focus error calculated using these data is 0.10%.