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Thread: Anaglyphic 3D with Lasers

  1. #11
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    On some broadband dielectric coated galvo mirrors (well, most), polarization angle can be changed with angle of the galvo shaft, The traditional cure is overcoated aluminum reflective coatings on the galvo mirrors. There are tricks with left and right hand circular polarization that might help, but I have not tried that yet. Before anyone says. "how can that be?", the path length through the 16 or so dielectric coating layers changes with angle of incidence, thus changing phase of the light between the coatings.

    You only have RGB, maybe RGBV in a modern low cost projector, but Chromadepth(tm) glasses do not depend on polarization.

    The patent on using Chromadepth(TM) in laser shows has most likely expired.

    A good pair of galvos has a small angle jump bandwidth of DC to 2000 Hz, maybe 2400 Hz. Large jumps have a much lower bandwidth. Keep you scan angle low and you can work magic. Widen it out and life gets interesting.

    3D Laser faded out because the Chief engineer of a major laser show software producer is not a fan. HIs former partner, however, Was.

    In the past some hardware outputted a dedicated Z signal that could allow you to generate X and X-Prime, for two scan heads. Anaglyph, Polarization, Active Polarization Rotation, field flipping with LCD glasses have all been done. When we use Ion lasers mixed gas or mixed pair, with PCAOM (our term for multi-line AOTF) we have eight or more colors for Chromadepth(tm), of which maybe 5 are far apart enough in wavelength to be significant (457, 488, 504,514,530, 568,647, 676)

    A WARNING, higher power solid state laser projectors almost always use polarization cubes / waveplates for combining arrays of laser diodes for higher power. You have to know what your getting into if you buy a laser that does not use single mode diodes.

    Single mode diodes for RGB at low powers are available from DTR Lasers for reasonable cost, but get glass collimation lenses to aid in maintaining polarization if you go that route.
    Multimode high power diodes can have a low power side mode at a different polarization state that gets annoying.

    A single mode RGB system of one polarization restricts you to smaller images at around 450 mW of available power. In other words, very small images in room light.

    These challenges for a laser hobbyist, tough. These challenges for an Engineer willing to learn, not that bad. Some place I have some 3D images in Pangolin Format on an old hard drive from the planetarium days, I'll see if the drive is still valid.

    Steve
    Last edited by mixedgas; 12-31-2022 at 13:46.
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  2. #12
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    I did some experimenting with the ILDA connector on the Laserworld CS-500RGB KeyTEX tonight. The Shutter and Intensity inputs do absolutely nothing, and the R, G, and B inputs are on/off rather than the voltage-controlled brightness I was expecting! Oh well.

    I guess I will have to do PWM of some kind to control the brightness. The red LED is too bright and shows through the blue lens of the 3D glasses too much. I need to experiment with some PWM. Any suggestions for chips or frequency?

    Tonight I was driving the X and Y voltages with audio signals from Reaktor. That mostly works, but I need to have Reaktor turn the LEDs off, then change the mirror positions, then wait, then turn the LEDs back on. Shapes with sharp angles have extra curved lines as the mirrors slew to the new position. That's doable.



  3. #13
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    I got it mostly working:

    http://www.marksmart.net/VectorStuff...JcoqihhFOTPyzo

    In real life, the cubes are constantly visible instead of flashing on and off like they are in this video. The frame rate of the camera makes it look wrong for some reason.

    Today I'm going to try PWM controlling brightness. If I can do the PWM in Reaktor instead of building circuits, that will save a ton of work and add a lot of creative possibilities. But I could also have it switch to CV outputs if I am hooked to a projector with RGB implemented like in the ILDA spec!

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    It is outputting sound as well, I just didn't have it audible in the video.

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    Here it is with sound: https://www.youtube.com/watch?v=4AtjZAmS8Gk Right at the end I kick in the PWM. It makes dotted lines but is still a useful effect. All the lines represent what you are hearing EXCEPT with the PWM for volume. That is a very unpleasant sound so I made it audible as a volume change instead. That PWM is at about 10 KHz. That's about where the sound card refuses to do pulses anymore. LOL I might try external hardware for PWM at a higher frequency.

  6. #16
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    I used my phone to make these. Maybe if I use a real video camera, I can adjust the frame settings so it will look like it does in person.

  7. #17
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    Quote Originally Posted by marksmartus View Post
    I used my phone to make these. Maybe if I use a real video camera, I can adjust the frame settings so it will look like it does in person.

    i use the "filmic pro" app on my iphone. it has controls for iso / frame rate / shutter speed. very handy for filming lasers.
    suppose you're thinkin' about a plate o' shrimp. Suddenly someone'll say, like, plate, or shrimp, or plate o' shrimp out of the blue, no explanation. No point in lookin' for one, either. It's all part of a cosmic unconciousness.

  8. #18
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    15 degrees, huh? OK. Yeah I can do that with Reaktor easily.

  9. #19
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    Do you think PWM at a higher frequency like 50K would get rid of the dotted lines and make the brightness fade in and out? I am thinking of building an external box with a ramp oscillator (running way above audio rate) and 3 comparators for RGB, to be controlled with 0-5V analog control voltages from the MOTU sound card.

  10. #20
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    OK. I bought a galvanometer and driver board off of Ebay before I realized that the ILDA connector was analog (I had previously thought it was a digital communications protocol like MIDI) and I could do this with an off-the-shelf projector. We'll see if I get dissatisfied enough to pair the galvo with that LED module.

    I will be controlling the synth from a Haken Continuum and a MIDI keyboard with a lot of knobs and sliders. In the video I'm just using LFOs and buttons, but the MIDI control is easy to add since I have already built it.

    Using the size of the shape to control volume is also a nice way to do dynamics. I'll keep you posted!

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