Automatically Based On The Talbot Effect Of Moire Fringe Count

Accurate counting of moire fringe is the key step of imaging test of large aperture lens which is based on Talbot effect. A new moire fringe counting theory is given in this paper. The concepts of correlation and patter-match are induced to this algorithm. The contribution curve of moire fringe is fully used so those mismatch mistakes are avoided, which usually happen when dealing with pictures that have high similarity. Both rapid capture and slow capture can use this algorithm. Meanwhie, it makes good judgement on the direction the moire fringe moves towards, all that leads to an accurate auto count.This paper also gives a 4-step process that can calculate the interval of moire fringe. Traditional algorithm first create a filter to get rid of noise, then set a threshold value to binarize the target image and finally thin the stripe to get its skull. In this paper, erode algorithm is added before thinning. The result turns out good. And because the direction of erode can be controlled at will, this 4-step process can handle moire fringe with different angles.In order to test quality of large aperture lens, two-dimension scanning is a good solution. We design the system based on Talbot effect and finished its software which contains digital image capture and procedure, engine control by COM port and accurate moire fringe count and direction judgement. All above help to realize auto testing the wave front of long focal length lens.