A new algorithm to conduct target precise locating is designed

mainly including dual fixed thresholds edge detection and subpixel edge locating by gray weighted centroid algorithm. By means of quantitative numerical adjusting to the 2 parts of the loop

integration time and program controlled gain(PGA)

a linear CCD video amplitude controller feedback system is devised so that each frame can keep a constant peak gray value of the target image to satisfy the needs of dual thresholds edge detection

and this light adjusting loop system features a less difficult light path design and lower cost. Compared with traditional binarization method

it is a simpler system with a more excellent algorithm

and its engineering application shows that this system

with a subdivided degree of less than 1/10 pixel

can function spot target locating precisely. The system scheme of the 2-varible stepless light adjusting numerical controller possesses an important reference value to the future design of multiple-varible light adjusting video system.