A better way to make holograms | Hacker News Reader

A better way to make holograms

economist.com

39 pointssohkamyung14 comments

>Instead of the laser, Dr Menon starts with multiple images, taken from different directions, of the object to be holographed.

I don't think it's a hologram if it's not created with a laser.

But semantics aside I think there are some practical points not addressed by the article:

1. A hologram created by a laser is capturing the light field of the object and so real holograms can be later viewed under microscope and contain said microscopic detail

2. If you split a real hologram in half both half will contain the whole hologram, and continue cutting the hologram into pieces and each piece will contain the whole hologram from the perspective of the viewing angle of the piece

3. Finally the article said laser holograms require a laser to see the image, but that's only true of transmission holograms (laser hits object then emulsion). Reflective holograms (laser hits emulsion then object) are viewable in white light without need for a laser.

I just started studying and creating holograms, and my goals would be: a). Bring holography out of the dark room (which this does but without the laser); and b.) develop the first laser hologram video

That's very interesting, thanks for sharing. What resources would you recommend to start understanding these points for a layman?

Quick background: https://www.holographer.com/history-of-holography/

Books:

"Practical Holography”, by Graham Saxby

“Holography Handbook” by Fred Unterseher

Unfortunately, sort of became a lost art. most of the hologram art and community (sellers of film and plates) all seem to be directly connected to a School for Holography in California that closed in the 70's and 80's. It's the only art form I know that includes lasers, emulsions and chemical development processes...I can't recommend it enough.

The school was in Emeryville, between Oakland and Berkeley, Fred Unterseher and Peter Miller were the primary instructors, I was a student. Fred's book was published while I was there. I still have several glass plate holograms I made while there. We thought we were going to change the world with Holography, how mistaken we were.

You accurately describe properties of a fairly narrow class of holographic displays.

There's a larger class of display types out there. For example:

White light transmission holograms (Benton or rainbow holograms), invented in the 1970s, work by eliminating vertical parallax. Holographic stereograms relax the requirement for recording the subject in coherent light, but may use holography for the output display device. Recent advances in computation have allowed non-optical generation of diffractive structures that produce a light field when illuminated (something this research partially covers).

(Source: developed computer generated holographic stereograms and taught holography at Steve Benton's Spatial Imaging Group at the MIT Media Lab).

> I don't think it's a hologram if it's not created with a laser.

At university, we calculated the microscopic pattern of holograms and printed them in high resolution on transparent foil. It worked surprisingly well.

Back then, we investigated doing the calculation on GPUs (~2005). You could store the complex numbers needed in RGBA textures, and then had to combine a large number of textures, each one a Fourier transform of a point source or primitive object. We ended up doing it on the CPU for simplicity, but now with general-purpose shaders, it should be revisited.

Also, someone should really try to combine computer generated holograms with high-DPI displays!

FYI, LASER's are not needed to make a Hologram. Dennis Gabor's original discovery of holography occurred years before Lasers, and was based on monochromatic sodium or mercury light passed through a pinhole... From: http://amasci.com/amateur/holo3.html

But Gabor's holograms were not display holograms of the type we think of. The long coherence length of the laser was essential to display holography as pioneered by Leith and Upatnieks at University of Michigan in the mid 1960s.

Submitted article extremely light on details, and conflates the researcher's incremental improvements in holography with long established techniques such as holographic stereograms.

See actual paper for better signal to noise:

https://www.nature.com/articles/s41598-017-06229-5

And no, we aren't any closer to virtual 3D objects in free space, no matter what the Economist says. Physics.

Reminds me a bit of the "caustic design" papers in recent SIGGRAPHs in that they're both optimizing a lens's shape so that it produces a particular output lightfield -- although the hologram needs to incorporate diffraction and produce a much more constrained lightfield.

(Caustic video: https://www.youtube.com/watch?v=R00IvqcI9jU&feature=youtu.be... )

Dead butterflies

Context: https://news.ycombinator.com/item?id=14460013

Can't unsee it now.

The author used the word "quotidian"... I hope they feel better now.

... but I love the sound of that word, I wish I could use it every day, LOL.

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