A Focal Length Measurement Method Based on Automatic Focusing Technique

摘要

A focal length automatic measurement method is presented here based on automatic focusing technique. The method assesses the accuracy of auto focus by means of image definition evaluation. The long-range coarse focusing is gotten by using Rapid evaluation function, the fine focusing is gotten by accuracy evaluation function. Finally focal length is measured automatically by grating displacement transducer. Experimental results demonstrate that the method has good repeatability, high accuracy', fast speed and so on.