Abstract The applications of CMOS image sensor play more and more important role on engineering measurements because of its low price and versatility. What its limitations and functions are of interest. The purpose of this study shows combination of digital image processing and CMOS image sensor, with delicate optical imaging system and proper math models, this system offers satisfied precision and stability. In addition, from these digital image models, we conclude that they can be applied to not only general size or distance measurements but evaluations of subpixel resolution. In this thesis, some digital image theories and large amount of data are presented. Though aberrations modified on image plane by digital image theory at last chapter do not have a series of complete verification, this characterizes the feasibility of higher precision and more practicability provided by CMOS image sensor.