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  1. #1
    Newcomer
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    Feb 2006
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    yeovil somerset UK
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    2

    Default DIY Laser Detector

    Hi,

    I'm an engineer in the UK seeking methods of detecting so called safety cameras when they are pointed at me. I noticed a few items a while back which discussed the matter, but no conclusions were reached.

    My research has found a report from Laser Technology Inc. (LTi), where they have listed the detailed spec of their 20-20 in order to comply with the eye safety requirements of the US authorities. I have a .PDF of the report, but the parameters are:-

    Marksman 20/20:-
    Laser diode wavelength 904nm
    PRF 125Hz
    Pulse Duration 12 ns
    Pulse Energy 416nJ
    Peak Pulse Power 34.7W
    Average Power 52mW
    Speed Measurement Distance: 30 ft to 3500 ft
    Acquisition Time: 0.3 seconds

    I have similar data for the stalker lidar:-

    wavelength 905nm +- 10nm
    Divergence <3 mrad
    PRF 130Hz

    I have also found a few PhD theses, and a useful suite of circuits at http://www.imagineeringezine.com/files/air-bk2.html

    It would seem viable to construct a receiver capable of detecting 904nm laser radiation. The issue is would such a receiver give enough warning?

    If anyone from the previous threads has devised any circuits or has any advice, I would like to share what I have with them.

    Simon Bond MEng, BSc(Hons),IEng,MRAeS

  2. #2
    Radar Fanatic
    Join Date
    Feb 2005
    Location
    Earth
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    2,357

    Default

    Sure, you can construct a circuit to detect the IR radiation if you have the expertise. You would end up with something that does the same job as the laser detection circuits built into modern radar detectors.

    The question is how the laser is used. I haven't heard too much about the camera vans that you have to contend with, so I don't know if there is a human pulling the trigger or if the beam is always present. In the latter case you might be able to reduce speed if you can be alerted upon entering the very fringes of the beam. How much time you would have I am not sure. But if there is a person pulling the trigger once you are in range then your chance of reacting quickly enough are roughly nil. Readings are practically instantaneous once the lidar unit is triggered. At the very least you would need passive countermeasures to reduce the reflective signature of the vehicle so as to substantially reduce targeting range. Active countermeasures (jammers) tend to be even better.

  3. #3
    Advanced Member
    Join Date
    Dec 2004
    Location
    Michigan
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    7,509

    Default

    There were a couple of other threads:

    http://www.radardetector.net/viewtopic.php?t=6673

    Vonkie was testing some different circuits, he posted schematics once I think too.

    Jim

 

 

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