principle of operation on banner vision system:model:presence plus. precence plus sensor are advanced inspection systems that capture and process an image of a defined area. the presence plus pixel-counting sensor renders a pass or fail judgement based on converting a 256-level grayscale image to a black and white binary image and comparing the number of white or black pixels to a user-programmed reference count .there are four basic components to the presence plus systems- light source.sensor lens,and programmer, if you want to get more information for futher,please send an email to me,I will try my very best to help you:crackchen@163.com