Camera focusing based on fringe pattern matching.

A method of camera focusing based on fringe pattern matching is presented. In the method, the variance of the mismatch function is used as a focus measure. The focus measure was examined in a fringe analysis system, and the results from the three well-known focus measures-gray-level variance, image gradient, and Laplacian-were also obtained in the experiment as a comparison. The experimental results show that the focus measure based on fringe pattern matching performs well in peak sharpness, monotonicity, and noise sensitivity and that it has a better performance in noise sensitivity owing to its advantage of averaging noise.