In the system,some new image-processing algorithms such as image segmentation method based on thread detection and sub-pixel subdivision technique so that the system is featured with good real-time characteristic and higher precision.

To do the edge detection of smoother accessory image attained after histogram adjusting the original image and holdiong edge filter,using the least-squares algorithm to do the edge fiting in order to get the sub-pixels figures of image edge,then worked out the accessory parameters.