Hi For our control systems project, we are trying to implement a closed feedback image focusing system. A digital camera captures the image of an object (a checkerboard), sends it to a computer algorithm which determines the amount of defocus in it and sends an actuation signal to a stepper motor controller which adjusts the focal length of the camera lens mechanically (by rotating the knob flanking the lens). For our experimentation right now, we're using a Lego Mindstorms Vision Commad System camera (lego cam), but our challenge is to be able to couple a stepper motor to the focusing knob which does not rotate freely. I have two questions: 1. Is there a USB webcam which has an adjustable focal length, with a knob that is convenient to couple with something? 2. What mechanism should be employed to couple the knob with the motor? Thanks for your help. Cheers Vivek.