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Thread: Home use laser show safe?

  1. #11
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    Nov 2008
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    Nope. Won’t work. You need to expand the beam with a beam expander then scan that. That needs two lens. Best way is to just drop the power on the modulation side. If you use a neutral density filter make sure to mount it slightly off axis so you do not send a reflection back to the diodes. The reflection should not be much. Also the filter needs to be glass and large enough to dissipate any heat. The energy has to go somewhere. Your choosing to dump it in thermal energy.

    just turn down the analog signal input and be happy.

    Im assuming beams here. If graphics your fine have fun just don’t look into the beam.
    if you really want to calculate the mpe there are lots of calculators on the web. Patrick Murphy does a good job presenting this on his webpage.

  2. #12
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    Sep 2019
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    Thanks again all for very useful feedback. Need to study all those details :-)

    @Kecked: you write just turn down the analog signal input...which I then take means to go down the path of DAC and what have we? don’t have a 360 view of how to hack that connection to the projector still and see it opens up for a bunch of other reading/complexity (if I end giving up on the right solution do you have any suggestion on ND filter value? Found a cheap solution variable ND2-400 I have been considering)

    See some cheap projectors having a “power” adjustment knob so would be tempting to check with the product team if that adjustment could be done on a pot inside the projector - will check that just for the fun of it. I also note that you say I would be fine with graphics which might be the answer to my original question. If looking into graphics is “safe” (not as problematic) as looking into beams is what you mean...

    thanks again all - more fun reading for me still progressing as we speak - as it becomes clear that I managed to onboard yet another hobby :-)
    Last edited by jemath; 09-23-2019 at 11:53.

  3. #13
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    be careful in the words used. "You'll be fine watching graphics ON THE WALL AS A REFLECTION OFF THE WALL" not LOOKING INTO THE LASER. Understand? Very important. You NEVER look down the beam toward the projector just at the image reflecting off a none shiny surface like a flat painted wall.

    For beams a lot of people like to look down the beams toward the projector. THAT is what is dangerous unless you do the MPE calculations and have tons of experience. Watching beams in the air with the visible beam away from you is fine. It is the direct beam that is hazardous.

    To adjust the power into the laser might not work in retrospect. The laser is probably a crap laser with bad modulation. IF you just drop the input modulation signal the mix of colors will likely be off. In that case a neutral density filter is best but read above again. In all cases but the direct viewing of a beam 2W should be safe unless it reflects off a shiny surface and again becomes a direct to the eye beam/

  4. #14
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    Sep 2019
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    Noted and understood - thanks for clarifying the safety side.

    Will work with two tracks onwards then: the filter-easy-lane and then the longer term correct way down the DAC lane...

    Thanks also for the tip of off-axis ND mounting which I’ll test. Also need to look for a cheap “disco scan lens” (or similar from aliexpress) that John mentioned.

  5. #15
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    there is no cheap disco scan lens. AND you only get one set of eyes so cheap isn't important here.

    JUST DONT LOOK AT THE BEAM DIRECT. that's it.

  6. #16
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    Looking at the projector, I think it’s likely that you have TTL modulation which is no-bueno when it comes to crowd scanning beams in your home environment. Converting to analog and adding ILDA capability is certainly possible, but would likely mean dumping all of the auto mode and SD card capability. You would need new diode drivers and some knowledge on how to tune them. After that you would need a DAC and software which allows you to define BAM safety zones and lots of knowledge on how to use such tools safely. Regarding safety scan lenses, I’m not sure you can get that laser to a safe level with even a -6 lens if you are in a small room. Even if you could, you’d need to learn a lot to do so safely.

    I think I’d start over by doing a lot of reading and analysis on laser projector offerings and the available software options. This will likely cost a factor of 10 or more as compared with what you have spent to date, so don’t feel bad as you haven’t lost that much money yet. 😁. Like most things, you get what you pay for when it comes to lasers. Feel encouraged to ask lots of questions as you do your research.

    Best of luck to you!

    David
    "Help, help, I'm being repressed!"

  7. #17
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    Sep 2019
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    Thanks for a very constructive and helpful reply David. See you have some good points and I’ll continue reading and be happy about the fact that I did not cost me a lot so far :-)

    ...for reference reading if there is any specific projector (make/model) suitable for such a small home environment please do let me know.

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