The Principle of image measurement system is that the geometrical parameters are ob-tained by processing the image edge of the object. For improving the accuracy of the imagemeasurement system

this paper proposed a crossed window automatic edge detection algo-rithem which has the properties of holding edge

reducing noise and adjusting threshold auto-matically in case of nonuniformluminary

and furthermore

a new subpixel edge detection al-gorithem based on polynominal interplation is presnte. By the algorithems the measuringresolution of CCD camera in image measurement system might be improved by about 60 times.