3 ms·

The lazy nerd in me wonders if he can abuse sth like a dot-matrix printer to automate this.

by VMG 10y ago

captainmuon 10y ago
This is actually something I did as a university project. We calculated computer generated holograms (CGH). To print them out, we found a ultra-high-DPI fotographic slide printer and got special small-grain film to print on. Then we printed the holograms, shone coherent light through the slides, and... nothing. I think we never found out why it didn't work, probably the contrast was not high enough. However, as a last effort, we used a simple 600dpi inkjet printer on overhead slides, and it actually worked! It seems there is actually enough information in the low-frequency part of the hologram to reconstruct an image. A couple of things we printed were simple geometric objects, 3d models of ants, and the USS enterprise :-). It was pretty cool, unfortunately I don't have the material any more. One thing I'm wondering is why nobody is trying to create a 3D holographic display (the Microsoft HoloLens isn't holographic AFAIK). TFT displays are getting in the dpi range where it should be possible. You could easily render the holograms with modern GPUs. (We actually investigated this back then (~2005) and it was then possible by abusing textures and doing things like putting two complex numbers in one ARGB texture. However we did not have more time for the project, and there was no benefit over just running on our cluser. This was before shaders, so it should be even easier now.)
- VMG 10y ago
  The inkjet method sounds like it has reasonable cost. Maybe there is a way to use a laser printer. Thanks!
  - wbeaty 10y ago
    Back in the old "Circuit Cellar" magazine era, they made a printer-hologram by photographing it onto film transparency. I recall that it was a "binary hologram" 300dpi covering a full 11" page, then reduced to a few-mms-wide patch on monochrome slide film. Obviously the main challenge would be in getting the darned thing in focus, so the fine pattern doesn't blur out into gray. Then, print out a feet-wide paper copy, so the pattern ends up as a few-cm hologram on your slide film.

The lazy nerd in me wonders if he can abuse sth like a dot-matrix printer to automate this.

by VMG 10y ago

The lazy nerd in me wonders if he can abuse sth like a dot-matrix printer to automate this.

This is actually something I did as a university project. We calculated computer generated holograms (CGH). To print them out, we found a ultra-high-DPI fotographic slide printer and got special small-grain film to print on. Then we printed the holograms, shone coherent light through the slides, and... nothing. I think we never found out why it didn't work, probably the contrast was not high enough. However, as a last effort, we used a simple 600dpi inkjet printer on overhead slides, and it actually worked! It seems there is actually enough information in the low-frequency part of the hologram to reconstruct an image. A couple of things we printed were simple geometric objects, 3d models of ants, and the USS enterprise :-). It was pretty cool, unfortunately I don't have the material any more. One thing I'm wondering is why nobody is trying to create a 3D holographic display (the Microsoft HoloLens isn't holographic AFAIK). TFT displays are getting in the dpi range where it should be possible. You could easily render the holograms with modern GPUs. (We actually investigated this back then (~2005) and it was then possible by abusing textures and doing things like putting two complex numbers in one ARGB texture. However we did not have more time for the project, and there was no benefit over just running on our cluser. This was before shaders, so it should be even easier now.)

VMG 10y ago
The inkjet method sounds like it has reasonable cost. Maybe there is a way to use a laser printer. Thanks!
- wbeaty 10y ago
  Back in the old "Circuit Cellar" magazine era, they made a printer-hologram by photographing it onto film transparency. I recall that it was a "binary hologram" 300dpi covering a full 11" page, then reduced to a few-mms-wide patch on monochrome slide film. Obviously the main challenge would be in getting the darned thing in focus, so the fine pattern doesn't blur out into gray. Then, print out a feet-wide paper copy, so the pattern ends up as a few-cm hologram on your slide film.