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Thread: Frequent use of DPSS below max power - issues?

  1. #1
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    Default Frequent use of DPSS below max power - issues?

    Here's another "newbie" question for you folks that have been using DPSS lasers (analog modulation) for a while -

    I'm leaning towards purchasing a LOT of extra green for my RGB projector (CNI DPSS) for the occasional beam show use. Most of the time, it will probably have to be dialed back considerably to get decent color mixing with the red and blue.

    Does anyone know of any adverse effects of frequently running these lasers at well below maximum output power?

    Thanks again!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  2. #2
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    The only effect I know of - which is not adverse - is that it will greatly extend its life.
    The harder you run pretty much most lasers the shorter thier life will be. Run them at reduced power treats them well and they will live long and prosper

    Rob
    If you need to ask the question 'whats so good about a laser' - you won't understand the answer.
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  3. #3
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    Cool - my fears put to rest, at least for the moment!

    Thanks!

    Randy
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

  4. #4
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    Does anyone know of any adverse effects of frequently running these lasers at well below maximum output power?
    Yes. Depends on how you plan on running it below max output. If you plan on letting the software handle the balancing then you may have an issue. If you plan on manually changing the driver max current setting, then you wont have a problem. Here's the deal, the linearity of most dpss's I've seen out there is not to good. You may find that you will get no output from the thing until you reach somewhere above 2 volts. So, lets say that using your software for color balancing, you have to dial back your green quite a bit and the max voltage ends up being 3V. So now you may be in a situation where your only dealing with a 1V swing with your fully balanced color pallete. With 8 bit color, each step is about 20mV from 0 to 5V. But now dealing with just 1V swing there are only about 50 steps between which will reduce the overall amount of colors you would be able to display. Its really a minor annoyance, I'm sure as time goes on, dpss drivers will become much better. What I did when I built my dpss projector, was try to get the color balance pretty close to begin with, accounting for typicall losses between dichros, so that with the laser fully on I get a pretty close white beam that way I take full advantage of what little linearity the dpss drivers actually have...

  5. #5
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    Another nice effect of DPSS at lower power, especially if they get their high output by verging on overdrive, is a reduced beam diameter and divergence. That could be useful to allow beamshows at full strength from something with not-great beam quality, but it might be good for graphics when run at lower power to match the rest.

  6. #6
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    DZ has a good point about the reduced resolution in color (50 steps as opposed to 255 steps).
    However, my experience with my CNI green is that the output power versus input voltage curve is highly non-linear, it even has a power dip neer the end ( negative dP/dV where P = output power) . My blue CNI has a nicer curve, at least seems to have a dP/dV curve that is positive along the whole curve but the dP/dV does seem to shallow out closer to max power.

    OK, coming to the point here: a small part from the whole curve in the lower power region usually approximates linear behavior. So that is another good effect at the sacrifice of resolution.

  7. #7
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    Well, since I've definitely got a bit to learn yet when it comes to voltage curves and related topics, I'll just throw this out there and request recommendations on whether my choices would work or not -

    My RGB projector will be using a Pangolin FB3 as the controller. I already have a set of the dual red Maxy modules on order, and will be ordering CNI LP-series lasers for the remainder. I want to be able to do graphics and decent beam shows, so I'm thinking about adding the CNI 150mw 473 nm blue and CNI 500 mw 532 nm green lasers - which pretty much maxes out my hobby budget for the foreseeable future!

    I plan on the typical (recommmended) 90-degree optics installation, with the green bouncing off 1 mirror and passing through two dichros prior to reaching the scanners. I'll probably be using LivePro as my primary software package.



    So, will I be able to "dial back" the green and still get decent color-matching for graphics, but have the full power available for beam shows?

    Thanks!
    RR

    Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
    1979.
    Sweet.....

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