在高中几何光学中,常有类似下面的问题:如图1所示,光线AB是通过透镜后的出射光线,试在图中作出入射光线.本题要想直接利用“三线两点一心”(即三条特殊光线,两个焦点 和一个光心)的特殊光线作图法,求作入射光线是不可能的.如果用透镜的焦平面和副光轴的知识解答,就十分简单.图1中F’A就是所求的入射光线. In high school geometry optics, there are often problems like the following: As shown in Figure 1, light AB exits through the lens and attempts to make incident light in the figure. This question is intended to directly use “three lines and two points” (ie, Three special rays, two focal points, and one optical center are special ray rendering methods. It is impossible to obtain incident rays. If the knowledge of the focal plane and sub-optical axis of the lens is solved, it is very simple. ’A is the incoming light.