Scratch holograms

[glajciorz]

Good day.

Some of my scratch holograms made with CD-boxes, ruller and a compass.
Instructions can be found on Bill's site:
http://amasci.com/amateur/holo1.html











greetings
Adam

[JohnFP]

WOW, there are some cool designed there. I like the spiral from the circle and that stary shape from the pie. Cool!

[glajciorz]

The most wonderful thing about those scratchy pictures is that by turning the plate around you can watch 3D shape emerging from the plate (and under it) from ALL sides

Pity that making even simple one (like the spiral) takes some 45mins...

Dodecahedron took me almost 3 hours of scratching and there are still not enough points. I sticked the plate to a computer monitor that displayed 30 cross-sections and scratched only 7-8 points each time.

Some automation of the process would be nice thing.

greetings
Adam

[RaulBSP]

It is a good thing to bring that topic to the forum. I also want to share some of my 1-2 years ago work on scratch holograms.
They were drawn in a acetate ovehead transparency size A4, top-front lit at 3m distance,and back mirror.




Photos aren't so good, in real life they look more impressive.

[glajciorz]

Raul did you try making scratchograms with XY plotter? I know few people tried it, but I can't find a program converting a stereopair into scratches. I'd like to try another approach - after creating scratches and printing them they would be transferred to glass plate and etched.
Or I could use plotter just to touch spinning plate with a needle in a specific points - instead of trying to draw them directly with plotter.

greetings
Adam

[RaulBSP]

Raul did you try making scratchograms with XY plotter?

I didn't try, but I think the plotter should be of a great resolution because
the grooves have to be smooth enough to not to ruin the light scattering.
Even smallest staircase plotting will be too bad.

I know few people tried it, but I can't find a program converting a stereopair into scratches.

I wrote a program that takes a 3D-Studio file and converts its 3D Objects into scratches, that can be printed. It also generate patterns that serve as a guide to make scratches manually. I used it to make sphere and ADN
double helix scratch holograms.
Converting stereopair is a bit more difficult. First we have to create a deep map from stereopairs. I tried some free programs on Internet that
claim to do this job, but they don't seem to work well or don't work at all.
It is not a trivial task that involves some Artificial Intelligence processing.

Or I could use plotter just to touch spinning plate with a needle in a specific points - instead of trying to draw them directly with plotter.

In that case how do you plan to move plate rotation center to make a scratch for every point? Rotating plate around a single point and moving
XY coordenates of plotter head to touch the plate with needle in certain points, will give you a hologram of a single line rising from the plate, or going deep into it.

Saludos,

Raúl.

[glajciorz]

I didn't try, but I think the plotter should be of a great resolution because the grooves have to be smooth enough to not to ruin the light scattering. Even smallest staircase plotting will be too bad.

That's why I think photolitography is the simplest way.

I wrote a program that takes a 3D-Studio file and converts its 3D Objects into scratches, that can be printed. It also generate patterns that serve as a guide to make scratches manually. I used it to make sphere and ADN double helix scratch holograms.

Good news

In that case how do you plan to move plate rotation center to make a scratch for every point? Rotating plate around a single point and moving XY coordenates of plotter head to touch the plate with needle in certain points, will give you a hologram of a single line rising from the plate, or going deep into it.

Of course you're right
Both the scratching pen and the spinning plate should be XY-movable.
Another reason to try photolitography.

greetings
Adam

[Tom B.]

Wonderful pictures! My interest in this approach has been renewed. I think the key problem here is how to produce, from computer calculation, many smooth V-groove arcs of varying center and radius on a shiny material. I had a fantasy about a photoresist coated plate exposed to light from a laser with a conical line beam expander mounted on an XYZ stage above the plate. Moving in XY adjusts the origin of the arc, up down adjusts the radus. Then it is merely a matter of processing the plate so the unexposed resist is removed and then etching to produce a mirror-smooth arc profile

It would also be interesting to to see what resolution would be needed to instead directly print the arc patterns as a dot matrix (assuming that etching was feasible), and what the noise/resolution tradeoff is. I expect that this has been explored but wouldn't know where to begin to look.

[glajciorz]

I had a fantasy about a photoresist coated plate exposed to light from a laser with a conical line beam expander mounted on an XYZ stage above the plate. Moving in XY adjusts the origin of the arc, up down adjusts the radus. Then it is merely a matter of processing the plate so the unexposed resist is removed and then etching to produce a mirror-smooth arc profile

Good day.

Maybe photoresist wouldn't be necessary - what if we coated glass plate with dichromate emulsion and make exposure with contact mask ?
After swelling we'll get scratches made of gealtine which refractive index differs from glass. If difference is not enough - we load stripes with silver nitrate, soak in formaldehyde and get silvery lines.
Or let's print the scratches on a transparency, transfer to glass/copper-coated laminate and (maybe not necessarily) etch with HF/HCL+H2O2.

What do you think ?

greetings
Adam

[Tom B.]

Maybe photoresist wouldn't be necessary - what if we coated glass plate with dichromate emulsion and make exposure with contact mask ?
After swelling we'll get scratches made of gealtine which refractive index differs from glass.

So here the scratches/grooves would be surface relief features created because the hardened gelatin swells less? Maybe it could be aluminized or plated somehow as is done to make those shiny metallic embossed holos...

[glajciorz]

So here the scratches/grooves would be surface relief features created because the hardened gelatin swells less? Maybe it could be aluminized or plated somehow as is done to make those shiny metallic embossed holos...

I hope they will look like this. As I look at the stripes of photoresist 5-20um wide and 2-4um thick - they are shiny and reflective. So maybe it could work with gelatine stripes alone too.

greetings
Adam