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looking to buy your first laser? Read this first!

  • DrJones Sunday, September 18, 2011 4:03 PM Reply
    And if the beam (or a reflection) hits someone inside, his/her eyes are permanently injured... Bad idea.
    And probably illegal anyway, depending on your country.
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  • kutro Wednesday, October 12, 2011 3:15 PM Reply
    DrJones, Leodahsan,

    I have the SD-306 200mW 532nm green laser pointer (bought from here).

    I understand it's quite powerful and dangerous. It can pretty much cut black garbage bags as butter.

    I don't know whether the actual reading is correct, nor how focused the beam(s) is(are).

    What is a safe distance that the laser can be shined at people, without causing damage?

    100m? 500m? 1km?

    I successfully tested the laser at 5km, and photographed it. I assumed this is safe distance. It's interesting, that it appears multiple beams are leaving the source. The diffused "dot" is about 3-5 meters in diameter.

    Looking forward to hear from you!
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  • sheepish Top 10 Forum Poster Friday, December 28, 2012 6:13 PM Reply
    In the first post "mw" should be "mW" and there's an occasional "w" that should be a "W".

    AUSTRALIA CAN'T HAVE 2MW LASERS BECAUSE OF THAT!

    2 megawatt lasers were pretty rare even before they were banned.

    For the purpose Mikkk mentioned above a 100mW laser is ridiculously overpowered and very dangerous, as DrJones mentioned.
    Remembering 30 years.
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  • fdg965 Wednesday, February 11, 2015 1:35 AM Reply
    Is this thread still alive? I just received my 200mW green laser SKU:26891. Reviews said that the wires are easily broken off from the contacts.

    I received with wires broken off. However I managed to test it out with two AA batteries. Panasonic Evolta with 1.58V each. Brand new batts.

    At first the laser is very bright and then it just dim out. Subsequent attempt was a failure. The dot was very dim. Like a 5mW green laser with weak batteries.

    Anyone knows how to repair/solve this issue?
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  • Clement0401 Monday, September 7, 2015 1:50 PM Reply
    Dear Leodahsan

    Recently I have bought a laser pointer from DX (Model as mentioned below), but was rejected in my country (Singapore) due to over specification. In the spec indicates that it is 5mW but custom checked in my country was 24mW. Therefore was force to sent it back.

    Any one out there have purchased any laser pointer which will not have problem going through Singapore custom? Your recommendation is much appreciated. Thanks.

    True Green Laser Pen 5mW (sku.91 External link)

    Regards
    0401
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  • RhyvenNZ Sunday, June 19, 2016 5:41 PM Reply

    Leodahsan thank you, your hard work is still helpful in 2016  :-)

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  • RLNDS.nl Sunday, February 19, 2017 7:00 AM Reply

    Wasn't interested in buying a laser, but the reading was very interesting. I didn't know about the physics. Now I understand why pilots are alway complaining about ppl pointing lasers at them and it being dangerous...  


    Thanks! 

    Booo !

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  • sheepish Top 10 Forum Poster Sunday, February 19, 2017 7:59 AM Reply

    Not all the info in the first post is correct. For example, 405 nm is violet, whereas purple is a mix of blue and red. The symbol for milliwatts is mW not mw or MW. Those are minor points, but the symbol error has been pointed out before, so I can only conclude that Leodahsan was not particularly interested in accuracy (even before it was pointed out). He appears to have moved on so is unlikely to correct it.


    Some more important points:


    10 mW green lasers are not safe for playing with your pet. That power can cause permanent damage. Your pet is never going to tell you how well it can see.


    10 mW blue is not "somehow safe". That power can cause permanent damage.


    50 mW blue lasers should definitely not be used without safety goggles. That power can easily cause permanent damage.


    Cheap green lasers from China do not have an infrared filter, which means harmful levels of invisible IR can be emitted out to the sides even when the laser is not aimed directly at someone.


    As DrJones mentioned, cheap lasers from China are known to sometimes not conform. with their claimed ratings. That is dangerous.


    I had a keyring red laser pointer measured by the local university; 4mW. For its spot size it had the intensity of full direct sunlight, but with only red light (632 nm), appears significantly dimmer than normal sunlight does. Our pupils open wide in dim light which increases the risk of retina damage, because it allows more of the laser beam through (especially if the beam is slightly off axis) and the laser dot can play on the retina for longer. Full sunlight can do permanent damage, but on a wide open, dark adapted eye it would be even worse.


    Retina damage can be either temporary or permanent. Obviously both should be avoided if at all possible and the best way to do that (while still using lasers, not avoiding them completely) is to only use low power ones.

    Remembering 30 years.
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