Laser pointing stability

  1. hi,
    I'm measuring my laser pointing stability with a focusing lens and a CCD.
    Could you guys tell me what would the relationship be between the offset from focal point in CCD and the angle with which the beam exits the laser?

    CCD is in focus.
     

    Attached Files:

  2. jcsd
  3. mfb

    Staff: Mentor

    That depends on your setup. If the laser source is in the focus (as well as the CCD), there is no offset at all - that is the idea of the focus,
     
  4. light source is about 2 meters from the ccd with a lens 10cm before the camera (100 mm f).
    software fits a gaussian to an image of the beam and tells me the central coordinates. Now I see that the laser is unstable in a way that the centrum of the Gaussian moves up and down in the focal plane, meaning that the beam hits the lens sometimes higher/lower than the middle. I'm trying to relate the angle from the source to that offset (see the attachment) in μradians.
     
  5. mfb

    Staff: Mentor

    Okay, so focus of the camera is basically set to infinity. Then the vertical position of the laser does not matter (in an ideal camera) and you can consider rays going through the center of the lens. The displacement is just sin(angle)*focal length.
     
  6. Andy Resnick

    Andy Resnick 5,785
    Science Advisor

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