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Thread: Laser diffusers - for speed cameras

  1. #1
    Join Date
    Dec 2006
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    Default Laser diffusers - for speed cameras

    ok its been a bad day today, i got done for doing 92mph in a 70mph

    any one know much about how laser diffusers work??
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  2. #2
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    Sorry to hear mate.
    The laser speed guns bounce a pulsed IR beam off your number plate (the most reflective part of your car)
    Ever shone a red laser pointer at a parked car in the distance?
    Standard number plate backing is retro-reflective.
    A several stage approach would be to acquire a non standard plate with a non-retro-reflective backing then coat the top surface of the plate with a visible pass, IR absorbing lacquer. That will reduce your reflection by several orders of magnitude.
    (You then wait to get pulled by every IR cam equipped constabulary car that you pass. They would take notice when your plate appeared blank on their cam display)
    I know this is going to sound crazy but you could try slowing down
    Lasers and beer don't mix. After 2 beers I lose coherence.

  3. #3
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    sorry i dont understad what you just said??? slow.... down..... ?????

    LOL

    does it pulse at a certain speed? is it possible to rig something up without spending 250 on a proper one?
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  4. #4
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    100W diode bars pointing backwards? That should cause some camera problems. Other then that, just add a band pass plate over the license plate to allow IR to bounce off. Final option would be to make your own license plate! Just take a picture then print it onto a piece of cardboard or wood.
    CLICKY!!!

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  5. #5
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    what do they use 808nm?
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  6. #6
    Join Date
    Apr 2006
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    Were they using a laser or just measuring the red-shift of your tail-lights?

    The speed detectors use a train of very short pulses from a 904nm laser diode.
    Your distance is continually calculated from time of flight.
    Speed is calculated from looking at the change in distance reading over a fixed time (0.3 seconds I believe)
    If the distance reading is very erratic - i.e. not linearly changing over time but jumping around an error is displayed.

    If you can provide a fairly random pulse train of your own at 904nm the gun will struggle getting a lock.
    I believe a fixed frequency pulse train is interpreted by the gun as jamming and indicates accordingly.
    A more fluctuating signal (like that of an IR remote) would be preferable.

    BTW this will only work at distance and the closer you get to the gun the more signal to noise will be on their side.
    You really need an 904nm pulse detector which turns on a cabin sounder and an IR pulse generator for 5 seconds.

    The IR beam is fairly narrow so ideally you need your pulse detectors (and emitters) on front and back plate + rear view mirror.
    Lasers and beer don't mix. After 2 beers I lose coherence.

  7. #7
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    lol...

    this is getting all hi-tech! the cost to do all this is more than the ticket.

    someone selse said it...

    andy....



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  8. #8
    Join Date
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    thanks robin, i will look into 904nm diodes.

    i didnt buy a fast car to drive slow LOL
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  9. #9
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    what kind of car you got?

  10. #10
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    clio 182 .
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