Video Optical Transfer Function Instrument

Optical Transfer Function (OTF) is currently considered as a premier parameter for objectively and effectively evaluating of the performance of optical systems. It has been widely applied in optical system design, imaging quality measure and testing. With the development of computer, photodetector, and image collection and processing technology, OTF instrument is improved continuously and video OTF instrument has come out.In this thesis, a video OTF instrument is proposed. Its measurement principle is based on a focal plane array with electronic scan and a digital Fourier analysis. By taking a pinhole as target object and Charge Coupled Device (CCD) as image detector, the obtained image of target is preprocessed and analyzed with a computer, and then OTF of the lens under test is obtained. This video OTF instrument works without scan mechanism and is of simple structure. Its measurement results are real-time displayed. Its testing process is absent of principle error.This paper first introduces the trends and present status of OTF instruments home and abroad, presents the mathematical model and physical meaning of OTF, and analyzes the working principle of video OTF instrument. Then the constitution and function of our video OTF instrument are specified. Its optical layout design is put stress upon. Next, its measurement error, especially the influence of system components on its measurement precision, is analyzed and corrected. The instrument test results are listed. In addition, a plano-convex standard lens of 50mm effective focal length is designed to verify the accuracy of video OTF instrument. Finally, our research achievements are summarized. Problems to be solved are discussed and prospects for the future work are brought forward.