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Thread: A Bit about Measuring Beam Diameter.

  1. #11
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    Thank you Steve !!! MMMMmmmm......next you will post a link to " Beam Measurement for Dummies " book....I qualify for that read !!!

    Free and good software with "Image J"...The TM7 camera...$ 75 bucks on fleabay..YES !!! We have long focused on power output !!! But....looks like accurate beam measurements/properties = beam density are within a very reasonable $$ reach !!

    Yikes....Maybe " Gone are the days of Sniffing the Dirt " !!! haha ( From the movie "Twister") Thanx again !!! Please keep the info come'in !!! CDBEAM, and MeasureDBEAM=======>
    Last edited by CDBEAM; 01-30-2015 at 18:55.
    Beam Axiom #1 ~The Quantum well is DEEP ! Photons for ALL !!
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    Beam Axiom #5 ~"Abstract Photonic Expressionism"....is "Abstractonimical" !!
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    Beam Axiom #6 ~ "A Posse ad Essea" ~ From being possible to being actual ...is the beam target !

  2. #12
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    Quote Originally Posted by mixedgas View Post
    I have a love affair with the LM1881, it lets me do field sequential stereo video with two synchronized cameras and LCD goggles. But I digress...

    Steve
    Very interesting and informative Thread Steve...
    And your Highlighted project is what got my attention...


    @CDBEAM
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  3. #13
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    Hi Jerry...Good to see you here at the " Swinging Beam Dream Team "...Yea...I still hang out at both forums... photons are photons as long as they are coherent...Each has something to offer....and that Dog Swami has me back to projector land with a passion !!! CDBEAM=======>
    Beam Axiom #1 ~The Quantum well is DEEP ! Photons for ALL !!
    .
    Beam Axiom #2 ~Yes...As a matter of fact...I DO wear tinfoil on my head !!
    .
    Beam Axiom #3 ~Whe'n dout...Po ah Donk awn et !!
    .
    Beam Axiom #4 ~A Chicken in every Pot, and a Laser Lumia in every Livingroom !!
    .
    Beam Axiom #5 ~"Abstract Photonic Expressionism"....is "Abstractonimical" !!
    .
    Beam Axiom #6 ~ "A Posse ad Essea" ~ From being possible to being actual ...is the beam target !

  4. #14
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    the low budget low tech way i always measured beams (old school)was to use a drill gauge

    http://www.toolfetch.com/irwin-hanso...FYsbgQodFyEAzg

  5. #15
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    You are doing this by brute force and trying to count photons? then based on RGB value calculate the energy of each wavelength? Or just get a color power profile of the beam? To make this simple.. Just take a picture of the beam with a camera. As long as it is not clipping high or low and the surface the beam is hitting has a known gain for each wavelength. Hell if you are just getting size or volume.. a few registration marks on the target material. Could even do it where the CCD is behind a translucent target.
    Rob Mudryk
    Retired old and Grumpy Laserist

  6. #16
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Rob,

    Pros go direct to the CCD and count photons. Doing it off a screen with a lens induces the transfer function of the lens, which is often suprisingly non-linear. What looks good to the eye via a lens is often a bit off for the beam profiling math. Camera Lenses are a tradeoff.

    Color cameras are not used to the pixel weighting which is R= 0.2989, G= 0.5870, B= 0.1140

    Besides, the CCD pixels make it inherently self calibrating. Spiricon built a multi-million dollar company out of doing it with photon counting.

    Ie its a heck of a lot easier to count pixels with the fram grabber when you know each pixel is 7 um by 14 um with a .5 um spacing. Saves on the calibration step and makes it far more accurate. Its self calibrating, and that is the beauty.

    It also offers the bonus of real time.

    35$ USB Frame grabber and a 15-50$ used B&W camera works a treat.

    I own a Spiricon, which does the M^2 , Size, and Gaussian Fit all in real time. It throws up a 3D model of the beam profile on the screen. If you have the camera on a rail and move it back a known distance, the Spiricon Software also does the divergence calculation in real time.

    Makes tuning a diode for least divergence and centering the collimator lens a breeze.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

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