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Thread: Yellow Orange Purple

  1. #1
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    Default Yellow Orange Purple

    Hi:

    The first (and perhaps only) time I saw a pro laser show what struck me was the colors which didn't correspond to any wavelengths I knew from the scientific lasers with which I was familiar. In particular there was a blazing lemon-yellow (not the yellow-green Kr-ion 568nm, but true yellow), and purple colors which particularly puzzled me because they didn't look like anything which could happen with a pure spectral color.

    At the time my understanding of color mixing was non-existant, so it didn't occur to me that the yellow and purple were simply the result of mixing colors from the Ar and Kr laser wavelengths that I knew. (This was before DPSS had become commonplace). I've also spent some time studying the CIE x,y color space, so I now undertand the difference between purple and violet.

    In recent weeks I've viewed quite a few images on this site of RGB projectors based on DPSS & diode lasers emitting typically 635nm, 532nm, and 473nm. What puzzles me now is that I have yet to see solid yellow, orange, and purple colors. All the rainbow-like color sweeping beam effects I've seen appear dominated by RGB, with narrow transitions between the colors that don't give any strong impression of a bold orange & yellow between the red and green, nor a good purple. (Though, I have seen a bit more purple than the yellow and orange).

    I wonder what is going on here? Is it that the photographic processes are not responding well to the colors because the wavelengths defining the color gamut don't agree with the RGB filter properties in the cameras? (I doubt this is the issue). Or is there a linearity problem with the analog modulated lasers? Or perhaps there aren't really many analog lasers out there, and most are TTL?

    The linearity question is my greatest interest. Has anyone put their laser on a high-quality wide-bandwidth photodiode receiver and fed the laser a triangle or sawtooth waveform to see how linearly the output varies with input voltage? This will be one of my first tests once I get my next laser - a 473nm variety.

    I hope to produce well balanced rainbows of colors with clearly defined oranges, yellows, and purples once I get my projector together.
    Have a good day!

  2. #2
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    Supposedly, you can get any color you want by varying the amount of red green and blue. These whitelight lasers dont contain equal continuum spectral properties like the old mixed-gas ion lasers. Buying yellow/orange, blue-green: 487-488nM, and violet laser diodes alone could cost 10X the amount for present RGB assembled lasers with standard 473,532 and ~650 nM colors.

  3. #3
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    Hi OPO,

    when working with analog modulated DPSS laser you have to expect that the output level corresponds in a non-linear way with the input signal. Besides that the output power wil vary on the duty cycle of the laser to some degree. And there also seems to be quite a bit of variation in beahvior from laser to laser, even from the same manufacturer (speaking of far-east manus).

    So can your color dream come true? yes but you have to be prepared to manipulate the signal you send to the laser so that you get the output that you want. Lasershow software should give some control over this but I only know mamba basic and it only allows the range to be set, nothing more advanced like linearity.

    If you are writing you own code you have full control software-wise but you can also manipulate the analog signal with a circuit inbetween DAC and laser. see the thread here.


    I'm working on that same color dream too see my pics here for some yellow and orange.

    cheers.

  4. #4
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    Quote Originally Posted by Zoof View Post
    Hi OPO,
    when working with analog modulated DPSS laser you have to expect that the output level corresponds in a non-linear way with the input signal. Besides that the output power wil vary on the duty cycle of the laser to some degree. And there also seems to be quite a bit of variation in beahvior from laser to laser, even from the same manufacturer (speaking of far-east manus).
    So can your color dream come true? yes but you have to be prepared to manipulate the signal you send to the laser so that you get the output that you want. Lasershow software should give some control over this but I only know mamba basic and it only allows the range to be set, nothing more advanced like linearity.
    If you are writing you own code you have full control software-wise but you can also manipulate the analog signal with a circuit inbetween DAC and laser. see the thread here.
    Yeah, I expect that I will be needing some compensation curves in the rendering processor. I'll be making my own with a DSP chip, so shouldn't be too difficult.

    I'm working on that same color dream too see my pics here for some yellow and orange.
    cheers.
    Ooh, that is the best color stuff I've seen yet! Very nice yellow and orange. I wish I could afford 457nm, but the prices are freakin' 6x as much as for 473nm. I hope in the future we can get the 445nm diodes for affordable prices. I'd pay $2-3k for 50mW right now.

    Looks like it can all be done with a bit of effort.

    Thanks for the input!
    Have a good day!

  5. #5
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    thanks, that color stuff can be addicting. My green should be on its way back from china by now, hope they solved the problem it being extremely duty cycle dependent output wise - that was really messing up good color control.

    Quote Originally Posted by OPO226 View Post
    Yeah, I expect that I will be needing some compensation curves in the rendering processor. I'll be making my own with a DSP chip, so shouldn't be too difficult.
    I implemented a simple gamma curve correction which works OK for now. A 4 or 5 point curve would be nicer.


    [QUOTE=OPO226;25371
    Ooh, that is the best color stuff I've seen yet! Very nice yellow and orange. I wish I could afford 457nm, but the prices are freakin' 6x as much as for 473nm. I hope in the future we can get the 445nm diodes for affordable prices. I'd pay $2-3k for 50mW right now.
    [/QUOTE]

    Actually 400 mW 442nm is available for around 5.5k US$ from HB-Laserkomponenten. Would be cool the first one here to have a 442nm diode (isn't it tempting you )

  6. #6
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    I'd rather have a Ti:Sapphire pumped tapered fiber supercontinuum with ALL wavelengths @ minimum 1W ea dream on eh...pppht.. oh well..
    If youre gonna dream...
    (see above avitar-- only $55,000usd)

  7. #7
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    That certainly falls within the dream category hmmmmmmm zzzzzzzzzz

    How would you modulate such a laser anyway???

  8. #8
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    Pcaom or prism or maybe just beam-shows with no blanking- just the rainbow of colors would be enough for me to stare at for hours

  9. #9
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    Cool

    yeah... a 1,000,000 channel PCAOM!

    Seriously though, I think the best you can get is 8 channels right now, right? So you get 8 wavelengths out of all the millions that the super-continuum laser produces... What a waste.

    Beams would be cool, but again, how to select the colors? You'd end up with a whitelight beam.

    I guess a prism could be used to give you one color at a time (or a slowly changing range of colors), but fast color modulation isn't going to be possible that way, which leads you right back to a PCAOM and 8 wavelengths.

    Don't get me wrong... The Super-Continuum laser is very cool. But I don't see how you'd adapt it for light show use without wasting nearly all the colors that it's capable of producing. (Eh, maybe someone can produce a 1,000,000 channel PCAOM for it. Hell, so long as we're dreaming about a $55,000 laser, why not budget another $50,000 for custom high-speed color selection!)

    Adam

  10. #10
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    Uh --yeah--
    I'm dreamin- but just give me some non-conventional scientific equipment and optics and I'll do some experimentin' --I'll let you know what happens
    No "TDK" or "Greek" signs on the side of a building tho..
    Purely abstract..
    Last edited by steve-o; 07-10-2007 at 03:28.

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