When Is One Pixel Cooler Than Millions?

On vacation, we went to see a laser show – one of the old school variety that combines multiple different lasers of many different colors together into a single beam, modulates them to create different colors, and sends it bouncing off galvos to the roof of a planetarium. To a musical score, naturally.

When I was a kid, I had no idea how they worked, but laser shows were awesome. As a younger grownup hacker, and after some friends introduced me to the dark arts, I built my own setup. I now know how they work from the deepest innards out, and they are no less awesome. Nowadays, you can get a capable set of galvos and drivers for around a hundred bucks from the far east, it’s fair to say that there’s no magic left, but the awesome still remains.

RGB laser
“laser show” by Ilmicrofono Oggiono

At the same time, lasers, and laser shows, are supremely retro. The most stunning example of this hit me while tearing apart a Casio projector ages ago to extract the otherwise unobtainable brand new 455 nm blue laser diodes. There I was pulling one diode out of an array of 24 from inside the projector, and throwing away the incredibly powerful DSP processor, hacking apart the precision optical path, and pulling out the MEMS DLP mirror array with nearly a million little mirrors, to replace it with two mirrors, driven around by big old coil-of-wire electromagnets. Like a caveman.

But still, there’s something about a laser show that I’ve never seen replicated – the insane color gamut that they can produce. It is, or can be, a lot more than just the RGB that you get out of your monitor. Some of the colors you can get out of a laser (or a prism) are simply beautiful in a way that I can’t explain. I can tell you that you can get them from combining red, blue, green, cyan, and maybe even a deep purple laser.

What you get with a laser show pales in comparison to the multi-megapixel projectors in even a normal movie theater. Heck, you’ve really got one pixel. But if you move it around fast enough, and accompany it with a decent soundtrack, you’ve still got an experience that’s worth having while you still can.

[Banner image from a positively ancient RGB laser hack. We need more! Send us yours!]

14 thoughts on “When Is One Pixel Cooler Than Millions?

  1. I have to admit that I’ve been to the Floyd too.

    hello, hello… are coherent photons in here? Please answer interfering. Is your spin that way, or are you just a wave?

    There is no Higgs boson, I’m massless. Time has no meaning in my frame. Entropy has nothing more to say! I…. have become- have become, polarized numb

    (In other words, support your local planetarium!)

  2. “Some of the colors you can get out of a laser (or a prism) are simply beautiful in a way that I can’t explain.” The Colour out of Space, or Octarine?

  3. One thing of these laser colors is, that they are so clear i.e. nearly only one wavelength, stays focussed (one sharp beam of light throug the night) and also coherent (that matters if you see it e.g. projected on a wall).

    1. Yeah, right?

      I didn’t want to get into it in the piece, because it’s a tangent, but the way we see color, right? Three sets of receptors that are roughly sensitive to a single wavelength each. So whether the same “color” is made up of a mixture of wavelentghts (RGB, natural pigments) or or a single one (like with lasers) shouldn’t make any difference as long as its stimulating our nerves the same.

      But I swear that I can tell the difference between the way especially some greens and purples look when on RGB and when from a single wavelength source.

      Wonder if I’m nuts or if there’s science there…

      1. There is science there.

        The sensitivity ranges of the cones overlap: https://en.wikipedia.org/wiki/Photoreceptor_cell#Humans

        A red at the high end of the red spectrum will also activate the green receptors a good bit

        A red at the low end of the red spectrum will activate the green receptors less.

        The exact combination you see depends on where the single wavelength source is located, and how much it activates the overlapping receptors.

      2. I think that using a single wavelength is the most superior way to get the sensation of pure (saturated) color, despite our ability to combine wavelengths at our receptor peaks to simulate it. I never thought about it until now, and the commenter before me, but it makes sense. I’ve seen colors so brilliant that surpass anything any graphic display has yet reproduced, even though science has found phosphors/filters nearly matching our receptor peaks. I’ve heard of some displays incorporating yellow pixels, for example, and I wondered “what’s the point?” but now I realize. It’s because our receptors have some overlap, there’s no perfect band limit, as mentioned before me.

      3. I think that using a single wavelength is the most superior way to get the sensation of pure (saturated) color, despite our ability to combine wavelengths at our receptor peaks to simulate it. I never thought about it until now, and the commenter before me, but it makes sense. I’ve seen colors so brilliant that surpass anything any graphic display has yet reproduced, even though science has found phosphors/filters nearly matching our receptor peaks. I’ve heard of some displays incorporating yellow pixels, for example, and I wondered “what’s the point?” but now I realize. It’s because our receptors have some overlap, there’s no perfect band limit, as mentioned before me. For example, mixing red and green typically looks like yellow, and should be indistinguishable from the yellow wavelength. However, the green in the first case stimulates the blue receptors much more than the actual yellow from the second example would, adjusting for intensity contributions of the sources for the same final effect. Therefore the sensation of yellow from the actual yellow source would still appear somewhat more vivid/pure than mixing red/green, and I’m not sure there’s a way around that. I’ve seen vivid pinks and others in real life I’ve never seen replicated on any display, for example.

  4. The future will bring us affordable and compact RGB laserd evices that would be able to be driven byt laserMame or anything that can emulate a Vectrex/Vector arcade machine byt outputing XY values for R, G and B. Can’t wait for the future

  5. One of my favorite laser anomaly can be witnessed anytime a coherent beam is fired into a non-reflective target. One sees little snippets of rapidly appearing dark areas in the pool of light where it hits the target. These little snippets of thread that are dark is the only time you will witness light that is out of phase by 180′ cancelling the collimated laser output. Like connecting a pair of transducers on the same plane – one 180′ out of phase from the other.

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