System Design And Software Development For MTF Testing Of A Lens

Ever since MTF substituted the traditional criteria as the modern standard to evaluate optical imaging systems, it had been favored by the photographers, industrial production and optical engineering field, and had been advanced day by day. With the fast development of computer industry and photo-electronic device, new instruments used for MTF testing had been developed both in home and abroad.Based on close research on the theory of optical transfer function, this dissertation offers an practical arrangement to test the MTF of a lens using contrast method.With its origin in the theory of signal and system, transfer function describes the way how a system will exert on its input signal. It bridges the way in which the input and output signals behave. Optical imaging systems are systems relating to spatial coordinate, they have the same mathematic model with the signal processing systems which are relate to temporal coordinate. Moreover, optical imaging systems are most cases linear and shift-invariable systems. In the case of being illuminated by incoherent light, they are linear shift-invariable systems in the respect of light intensity. For systems of this kind, if the target intensity has a sine wave distribution pattern, the intensity in the image plane will also distribute in the same way. What's encouraging, they are of the same frequency. The only difference is that the contrast in the image plane is compromised. How the contrast is impaired tells the MTF value at this specific frequency.Owning to the design and fabrication process of the LCD and CCD, what intensity value emitting from the LCD is not what value you set to that pixel, and what you read from the CCD is not the real value of what it really got from the outside, these all bring errors to the test result. According to the different ways LCD and CCD are contributing to the errors, here we bring forward an effective approach to isolate the modifying coefficients for both LCD and CCD respectively, given the system's integrative response-to different inputting intensity at different pixels-is obtained. Besides, the paper gives a detailed discussion on how to decide on theoptimal magnifying ratio, and measure to extent the testing range is also covered.Among other things, the author redesigned the overall testing flow with reference to the predecessors' work. Codes were written, and tests were performed.