A concave mirror reflects parallel light rays so that they meet at the so - called focal point . ( if you try to use such a mirror to start a fire in sunlight , you place the tinder at the focal point . ) the distance from the mirror to the focal point is its focal length 凹面镜反射平行光,让光线汇聚到所谓的焦点(如果你想用这种镜子在日光下起火,就要把易燃物放在焦点上) ,从镜面到焦点的距离就是焦距。
So the base decided to rebuild the system , in the rebutided detect - calibrating system , closing control technique has been adopted and the guiding accuracy has been greatly improved . at the same time , it has adopted multiple parallel light - pipeline scanning technique , and the efficiency of detect - calibrating has remarkably enhanced 在改造后的检校系统中,采取了闭环控制,提高了引导精度,同时采用单航路多平行光管的扫描,提高了检校效率。