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Question on laser reflection (pic included)

  1. Jan 30, 2016 #1
    Good morning all,

    I'm currently working in some undergraduate research involving lasers and recently had the opportunity to play around with a few that my research professor has at our disposal. I've included a picture below of a strange phenomenon that has me a little puzzled, but then again I haven't taken any optics courses.

    https://scontent-ord1-1.xx.fbcdn.net/hphotos-xat1/v/t1.0-9/12509680_10156372942255580_8733921899061724202_n.jpg?oh=6d59dee08a311015be6e8811bd211c64&oe=573793A9

    While the quality of the image isn't the best, what I've done is place the outputs of three 90 mW lasers of 656 nm, 532 nm, and 405 nm up on a wall located in a room with very little to no textural disturbances on the surface of the wall. I can't seem to understand why the green laser would have such an enormously wide output compared to the two others.

    Is there a property in optics that might explain this? I thought maybe diffuse reflection would be greater for longer wavelengths or something along those lines, but the red laser would have to display that property too, so I'm a little stumped.

    Any ideas?
     
  2. jcsd
  3. Jan 30, 2016 #2

    davenn

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    Question to you
    was this extra brightness just visible in the camera image ? or visible directly by eye as well ?

    There are some significant reasons ......
    ....... ohhh and to help you in your quest ..... google search eye and digital camera sensor sensitivities


    Dave
     
  4. Jan 30, 2016 #3
    Hey Dave,

    This extra brightness was also visible via the naked eye as well, and is especially more pronounced. Unfortunately, none of the crazy reflective detail translated to the photo.

    Thanks for your recommendations!
     
  5. Jan 30, 2016 #4

    Drakkith

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    First thing I would do is make sure the lens on each laser is clean and free of smudges, dirt, etc. It could be something as simple as a smudge on the green laser that's causing it.
     
  6. Jan 30, 2016 #5

    blue_leaf77

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    Or batteries?
     
  7. Jan 30, 2016 #6

    mfb

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    Humans eyes have their sensitivity peak around green, while 405 nm is at the edge of the visible range and the sensitivity for 656 nm is worse as well. That explains a large part of the observed difference. Cameras are more sensitive to green light as well to improve image quality, but image processing takes care of this.
     
  8. Jan 30, 2016 #7

    davenn

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    yes and this is what I was wanting the OP to google research on and he would have discovered that :smile:


    Dave
     
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