变焦距跟踪测量的应用

Application for Changing Focal Length in the Process of Tracking Measurement

摄影和摄像测量中，为计算脱靶量方便，通常都采用固定焦距、固定视场。这不能兼顾目标距离近时，需要大视场，目标距离远时，需要长焦距的矛盾。如果能在跟踪测量过程中改用不同的焦距就能解决此问题。

In order to measure quantity of target-axis offset more conveniently, photograph and image pick-up usually use fixed focal length and angle of view. However, this can not meet the need when the distance of the target is different. When the target is near, a wider viewal field is needed, when the target is far, a longer focal length is needed. We can therefore solve the problem by using different focal length in the process of tracking measurement.