自准直法测凸透镜焦距易犯错误分析

Analysis on Fallibility in Measuring Convex Lens Focal Length by Auto-collimation Method

自准直法测凸透镜焦距是大学物理几何光学实验中的一个重要实验．在利用该方法测量凸透镜焦距时，由于存在不是在凸透镜焦平面上形成的像，而造成学生测量中的错误．本文通过理论和实验角度，就测量中学生易产生的错误进行分析，同时提出切实可行的排除方法．

Auto - collimation method is a main experiment to measure convex lens focal length in geometrical optics experiments. Students often confuse the ＂true＂ image and the ＂false＂ image, The ＂true＂ image is shown on the focal plane array of convex lens. However,the ＂false＂ image is not. This paper analyses the ＂true＂ and ＂false＂ images using the method of experiment and theory. A method is given to distinguish the ＂true＂ and ＂false＂ images.