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Control Systems Project Closed Feedback Image Focusing

  1. Mar 25, 2008 #1

    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.

  2. jcsd
  3. Mar 26, 2008 #2


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    2. What mechanism should be employed to couple the knob with the motor?

    That would depend on you focus knobs amount of rotation. If it's range is <360° then you could just couple a 360° stepper directly. I don't think the power of the stepper will be much consideration if the focus control is done with a pot.
    Last edited: Mar 27, 2008
  4. Apr 9, 2008 #3
    Hi dlgoff, sorry I did not notice your reply. We have since made considerable progress in the hardware aspects, but the software aspects remain fuzzily addressed.

    Below is the link to my most recent post regarding the same project:


    I am sorry for the double posts, but as the problem statement has been modified, it seemed appropriate to start a new thread.
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