Category: specular holography

Robin found some copper flashing at the hardware store. Hell yeah I’ll etch it.

The glint is good, but it comes with a traveling vertical line that reflects the light source. I need to see if I can treat the surface to avoid that before etching. By happenstance I found that a rectilinear light source (office neon) perpendicular to the etching works better than a single light source pointed at it. It covers more vertical angles of viewing while not diffusing the horizontal effect. Running it parallel, much like a diffuse light source, ruins everything. I should draw how this stuff works a bit.

My office is a little small and barely able to contain all the machines I’ve accumulated. The 3D printer I turned into an etcher for specular holograms was obnoxiously tall, and really doesn’t need much vertical range. I chopped the aluminum extrusions so it would fit in an unused corner of the room. I’ve been doing occasional tests here and there, nothing worth showing yet. Results are very hit and miss, and finding good subjects is hard too.

lots of trials, lots of refinements, 4 days on the etcher bed. The load cell addition makes for the most precise etching.

Without light

with light

It feels different in person. What’s funny with this specular stuff, is how enthralled I was with it when I didn’t understand how it works. But now I kind of don’t see what the big deal is. I have to remind myself it’s really cool to keep forging ahead.

Since I can control pressure, I’m trying all sort of materials and pressures. I’m literally throwing under the tip any garbage that looks like it could yield a glint, and getting good surprises. I’m of course trying the classics like acrylic and aluminum with various pressures, again to find the best parameters.

I’ve had mitigated results with my specular holographs, I ran several trials, and only one was really worthy so far. I’ve learned a few lessons, but I’ve had enough success that I want to spend time and resources refining. The way the tip action worked so far was very blunt, I rigged a servo on a 3D printer which could instead have 2 steppers driving the pen up & down action. But that was an easier first step for my plotter stack. So the obvious thing to refine first is to replace the servo with the existing steppers, which is more of a programming challenge. And that part wasn’t too bad. What was much harder though, is how to move the tip so that it presses against the medium with defined and reproducible pressure. With the variations I can’t just “count steps”, and some media (acrylic) require very little pressure, unlike aluminum which was more forgiving. So I know I want to experiment with tip pressure, which means getting a load cell. And that on the other hand was a whole can of coding worms. I won’t go into the boring details, what matters is that it’s etching!

I have the tip go very carefully down until it reaches a pressure of 20g, and then it tries to maintain it while moving. Between the incessant taring, and the slow motions, it’s made everything a thousand times slower. I don’t care though, I can do other things while it works.

The machine makes really cool noises with all the extra stuff to find the right pressure. Simply keeping an ear out while doing other things has been a great tool to debug and improve algorithms.

A few iterations & trips to the hardware store and they’re starting to look decent.