Can you suggest a method to measure centering error of lens using frame grabber card plugged in a PC? Our test set up is as follows--We have a autocollimating optical head mounted on the measuring unit. A CCD camera is placed at the focal point of autocollimator. The autocollimating optical head is focussing in the centre of curvature of the lens.When rotating the lens under test, if centering errors are present, the image of the target formed on the CCD will move correspondingly. Presently we go by visual judgement on the CRT monitor to find out the displacement , ( a reticle is formed through the collimator) by seeing how many divisions the reticle has moved. Kindly suggest a method to quantify the error with above setup?