• Laser Cyanotypes for Recalculating Route

    Owen Trueblood • 06/05/2026 at 13:59 • 0 comments

    I recently showed some artwork related to my rollerblade street scans in an NYC Lower East
    Side gallery. Those were made with lidar so I thought it would be fitting to use laser beams to make cyanotype images based on the data. Below I’ll take you through what I learned while hacking together the process and how I put together the final laser plots.

    Laser Projector

    Many years ago I built a rudimentary laser projector from an XY galvo kit off of Amazon and a BeagleBone driving 12 bit MCP4725 DACs through some op amps. The DACs were what I had laying around but were very slow so I couldn’t accomplish persistence-of-vision for any interesting graphics. I made some long exposure photographs and then put it in a box. But for this project I had the perfect excuse to dig those parts back out, because I would be moving the laser very slowly anyway to get sufficient exposure time for the cyanotypes.

    I quickly but roughly blocked out the parts in CAD and got a basic layout together. Then I laser-cut the bottom plate and 3D-printed the laser galvo assembly. The image above shows the last version but initially I had the mount set up for a much smaller laser. The laser shines in through a hole in a shroud (made transparent in the render) onto the first galvo mirror and then bounces off that and the second mirror out the larger hole on the front.

    Not very pretty but functional enough- I was trying to be as functionally lazy as I could to save time. The Arduino is in a plastic bag to prevent it shorting out against the board holding the DACs and amps and the galvo power supply. There’s a AA battery pack tucked in for a 5mW red laser that I used while testing the software.

    Laser


    40 minute circle exposed with 5mW UV laser.

    Initially I tried a 5mW(?) UV laser of unknown provenance that I had in one of my junk bins. This did work but only barely. It took 40 minutes to expose a small circle. I was going to need to go much faster to have any chance of getting the final work before the show, let alone the many tests I knew I was going to need to do to get something I was happy with. So I went on Amazon and bought a 250mW 405nm laser intended for laser engraving.

    Laser Safety

    Every human who values their eyesight should fear lasers. They are very effective at damaging eyes even at low power. With very low power visible light lasers you might be protected by your blink reflex before serious damage occurs. But at powers >1mW or with lasers outside the visible range exposure can mean essentially instant blindness. Even if you get lucky there can be other kinds of deleterious effects. Damage from UV light exposure accumulates over your lifetime and can lead to cataracts later on.

    The laser came with cheap plastic safety glasses but I wouldn’t trust those. Initially I ran tests by putting everything in my apartment’s windowless bathroom and only powering it on with the door closed and me in another room. I used webcams to watch what was happening remotely. But when I went to make larger scale plots I was struggling because the laser dot wasn’t in focus. I didn’t see a quick way to set it up to adjust the focus remotely so I needed some way to protect my eyes while I did the focusing by hand.

    Please don’t ever do this just because it worked for me. I sealed the light leaks in my Quest 2 with foam and taped it all over with aluminum duct tape to avoid any chance of light unexpectedly leaking through plastics or cracks (image above shows it partway through the process). Then I used passthrough to see what I was doing via the cameras on the headset.

    This ended up being more useful than I expected when used in combination with a bit of software I wrote to pipe video from webcams into the Quest’s browser. It let me set up a camera with a tiny aperture that was zoomed in at a tiny spot on the work and watch the live feed in augmented reality while focusing the laser dot. And then I could switch over to a webcam with a wider shot...

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