Dynamic Variable Frequency Sinusoidal Grating Measurement Ccd Modulation Transfer Function Of The Processing System

The charge-coupled device (CCD) is a very versatile image-forming device. CCDs have a number of advantages over other image-forming devices, and in recent years have used in many fields. Therefore, it is the current need for producers and users to find out a method for testing the quality of CCDs. The modulation transfer function (MTF) is an important parameter for evaluating the quality of a image-forming system, because MTF can objectively reflect characteristics of spatial frequency response of the system.This paper bases on a new method for measuring the modulation transfer function of the CCD by using frequency-variable sine grating patterns, which is proposed by Professor Hu Jiasheng. The author has realized this method and constructed the system setup for MTF measurement of CCD. This system setup includes optics unit for creating frequency-variable sine grating patterns, collection unit for collecting the sine grating patterns, and data processing unit. In the optics unit, basing on the previous researcher's study, the author improves Michelson interference apparatus, and has constructed a suit of apparatus for creating sine grating patterns. This suit of apparatus can create high contrast and frequency-variable sine interference patterns. In the collection unit, the author makes use of the collecting card to collect the patterns passing by the CCD into the computer. The author improves the collecting software, whose interface became more friendly, more easily to operate, and propitious to use. In the data processing unit, basing on the collected patterns, the author writes the data processing software and gives multi-frame-average, multi-line-average, improves median filter algorithm. The given algorithm can filter the noises of the patterns efficiently. It is easy to work out the modulation of each special frequency by the software, and to draw the modulation transfer function curve by least square algorithm. By several testing, the measured results show that the respective error of modulation transfer function curve of repeated measurement is under allowing, and can apply to measuring MTF of CCD.In sum, in this study the author has completed the following works: 1. The author farther theoretically analyses on this new method. 2. The author has designed and constructed a suit of experiment apparatus for creating frequency-variable sine grating. 3. The author has improved collecting system software. 4. The author has written data processing software and filtered the noises efficiently by using manifold methods. 5. The author has measured the MTF of CCD by using this processing system.