The laser spot of the upright incidence to train wheel is imaged on CCD.While the train wheels are frayed, the image of spot will take place displacement.

• 激光束垂直入射到火车车轮上,再用透镜将火车车轮上的激光光斑成像到CCD上,当火车车轮产生磨损时,CCD上激光光斑的像也将发生位移。