Camera Module Focus Adjust using Contrast Transfer Function

Question

Currently I'm designing a test program for mobile phone camera module. I'm trying to control a precision motor that adjust the focus barrel of the camera to get optimum focus point. I've been looking for an algorithm for contrast transfer function but so far what I can find is only mathematical formulas.

Has anyone tried implementing CTF before?

Answer 1

Yes check this one, it performs CTF for microscopes photographs

Answer 2

You probably want to CTF only the center of the image, both for speed and to "read user's mind". Depending on speed, you may even want to CTF just small sample regions within that - the faster your focus slew, the more impetus you have to be able to do a fast CTF. To me, the interesting question is the next part - what kind of control system should be used to find the best focus, given what-all the user's doing while you're trying to focus? [I'm just spouting off - I've never done this!!]