Research On The Optical Parameters Measurement Technique Based On Image Analysis

For the measurement of optical parameters, the traditional measuring instruments need to be visually aligned and artificial measurement data which lead to low precision and efficiency. With the development of the Digital Image Processing technology and the diverse needs of customers, the high-precision and multifunctional testing equipment has become a developing trend. The thesis is to research on testing technology based on image analysis.First of all, the advantages and disadvantages of various methods are discussed in detail based on analyzing the most of the traditional measuring method of the measured parameters. Based on them, the testing models are established. The image of the characteristics of target are collected by a CCD. According to Matlab and other software programming, the program can control the movement of component, image collection and data processing.Secondly, the various of focusing evaluation functions and search algorithms are studied. There are four types of focusing functions consist of gray gradient functions, frequency-domain functions, informatics functions and statistics functions. There are seven algorithms include Fibonacci, golden section method, curve fitting method, traverse the search method, slope method, bisection method and hill-climbing. To deal with the same image which are from spot to dot and then from dot to spot by using all kinds of focusing evaluation functions. The focusing curves are gained by Matlab programming. According to the characteristic of curves, the gradient vector square function was treated as the focus judgment basis of focal length. Those characteristic include unbiased, unimodality, sensitivity and efficiency. The step selection affects the precision and speed of test system. It is an important factor in search algorithm.The multi-point comparison method is chosen by experiment.Finally, the focal lengths which are 68.39mm,196.34mm,15.01mm are tested. The radius of a conver len which is 51.32mm and the radius of a concave len which is 75.18mm are tested. And F number of the optical component which is 8 is tested. The experimental results indicate, the error and repeatability are±0.5% for the focal length. The error is±1.0% and repeatability is ±0.5%for the radius.The error and repeatability are±3% for MTF.