When the web worked normally, it passed through the central axle of the light pole so that the optical power received by photosensitivediode was normal constant.
带材正常运动时处于光柱的中心位置，光电二极管接收到的光功率为一定值；
2
On the basis of accurate theory, using laser emitter and photosensitivediode as testing sensor, a set of laser equipment for automobile axle depth of parallelism test is designed and produced.