用自准直仪测量平板的平面度 ,由于自准直仪本身有一定长度 (约 2 0 0mm) ,如果把带有反射镜的桥板放在自准直仪的正前方 ,则自准直仪本身占去的部分就测不到 ,造成被测截面少测一段。一般介绍把自准直仪架到被测平板的外面来测量 ,但需把桥板的侧面靠在一直尺上 ,以控制桥板移 Self-collimator flatness measurement of the plate, the self-collimator itself has a certain length (about 200mm), if the bridge with a reflector is placed in front of the self-collimator, the self-collimator Instrument itself occupies the part can not be measured, resulting in measured cross-section less measured section. General introduction The self-collimator rack measured to the outside of the flat to be measured, but the need to lean the side of the bridge on a ruler, in order to control the movement of the bridge