Evaluation Of Image Quality Of Electro-optical Imaging System

To evaluate image quality is an important method to test an electro-optical imaging system performance objectively and accurately. Modulation transfer function (MTF) is one of the important characters of an electro-optical imaging system performance. It indicates the spatial frequency response character of an electro-optical imaging system objectively and also an important basis of further researches of minimum resolvable contrast(MRC) and range prediction of electro-optical imaging systems work in visable light band. MTF used to evaluate the performance of optical systems, since optical systems are considered linear and space-invariant. But to extend this method to evaluate electro-optical imaging systems performance was not successful because that CCD array is a discrete sampling device and may cause aliasing which may damage the image quality in high frequency severely. So it is necessary to develope new methods to evaluate electro-optical imaging systems performance.The imaging theory of electro-optical imaging systems is analysed and MTF model of imaging systems is indicated. The typical methods in lab of measuring MTF of electro-optical imaging systems are discussed and compared carefully and the test procedure is illustrated. The reason of big inaccuracy of the MTF calculation method using the contrast of periodic square-wave pattern is analysed. An easy way of MTF measurement using images of three-bar patterns is suggested right after the spectrum of 3-bar pattern is illustrated. This new method can attenuate aliasing which is caused by discrete sampling device efficiently. Feasibility of this MTF measurement method is proved by test results comparison and theory analyse, future discussion is conducted.A new way of MTF measurement of electro-optical imaging systems in lab and field test is open by using resolution targets images.