A computer aided system has been developed for the focal length measurement/compensation in camera manufacture. Signal data proportional to light intensity is obtained and sampled very rapidly from the line CCD. Based on the measured signal, the MTF performance is calculated, where the MTF is the ratio of magnitude of the output image to the input image. In order to find the optimum MTF performance, an effcient algorithm has been implemented using the least squares technique. The developed system has been applied to a practical camera manufacturing process, and demonstrated high productivity with high precision.