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Better Holographic Data Storage
Pinlighter writes "Optical holographic data storage has the potential of providing better storage densities and access rates than the magnetic media used today. However, the technology has problems, mostly because the information tends to get a bit scrambled each time it is reread. According to the
link, a group of Japanese scientists have now developed a material which is stable for hours and across multiple rereadings. The material also allows easy erasure (by UV light) and rewriting."
I am no expert at this, but maybe the continuous, analog nature of holograms causes a problem here?
If you have a holographic picture, we usually have smooth surfaces; if you view a program as a picture, it looks (more or less) like randomly set pixels. Having a 3D representation is only going to make things worse.
Of course the goal is to increase the precision of the holograms, which will solve this problem; but unlike transistors, holograms do not have the kind of inherent "noise immunity" that silicon memory chips have. There is still a long way until we have data crystals à la Babylon 5.
it currently seems to have more in common with the B5 data crystal things. imo of course :)
-Yarn - Rio Karma: Excellent
The materials they're talking about are hideously expensive to manufacture.. and I doubt their set-up is very fast at this point. I also have to wonder if they've started testing what normal electron flow, or thermal effects, to the material would cause in the way of intereference.
But they are starting to use angled beams to layer information, which should make the overall construct small, so possibly feasable to systems needing huge storage capacity.. at least short term capacity.. I also have to wonder if the beam disturbs areas that it's just 'passing through' and not trying to read.. in that case I hope the IRS adpots this technology in the near future.. I can just imagine what wholesale data degredation would cause some 'interesting' activity..
Until you get down to about 10^-7m you can consider everything analogue. Memories have a continually varying number of electrons held in a capacitor. Its the thresholding of the charge that defines a 0 or a 1.
.3 its a 0".
You can do the same with holograms, "if the reflected intensity is >0.7 (relative intensity) its a 1, if its
-Yarn - Rio Karma: Excellent
Apparently these new iron memories would change in one clock cycle, but would then hold the state. (I can't recall the exact details of how it works, it was too late when I read it last night.) I got the impression that it could be used like EEPROM or flash-EEPROM, except sufficiently fast and inexpensive to be used for main memory.
So I am a little confused. It appears holographic storage merely uses a material that has optical memory properties (the electrons move to the light) to record a hologram on. So what is the benifit of holographic storage.
It would appear you could get just as high an information density using lasers not in any holographic projection system. So what is the benifit of holographic storage.
Marriage is the "pseudo-ethics" that cloaks the messy truth of sexuality in the raiment of propriety -- it's "Don't Ask,
I did undergraduate research on iron-doped lithium niobate. While LiNb03 *could* be used to store data holographically, organic polymers do a much better job at lower cost.
LiNb03 is fragile (it's a crystal, drop it and your data's dead) and very expensive to produce. The crystals are grown using the same? process as silicon but has a much more complex crystal structure and is much harder to produce consistent crystals of good quality). A crystal about 5 cm x 5 cm x 1 mm cost several hundred dollars.
Here's a project that some people are working on up here at Syracuse University.
:-) Okay, not exactly, but it's fun to call it that. A very small rectangular cube (about 0.5" by 0.5" by 1.5" or so) is filled with a protein substance suspended in a solution. It is primed by hitting the substance with a laser, and it denatures the protein. Then, a laser is shot through on an X plane, and a different laser hits on certain points on the Y plane. The protein is denatured where the two meet. This substance is a three dimensional memory system. You read back by a similar method, but with a lower power laser beam. The laser doesn't pass through the points that are denatured, and produces a grid of binary numbers essentially. Of course, the protein cube requires no power, so it's perserved when off. Imagine being able to take the ram out of one machine and put it in a different machine, without changing the contents.
:-)
Jello RAM.
These small cubes can hold about 4 gigabytes of data, and last price I heard was $20 (the cubes are practically nothing. They're cheap to make. It's the read/write equipment that costs a bunch). It has decent access speeds, cheap, and very small.
This is all very experimental lab stuff right now, so the size and speed can change. The goal is to make very cheap, small, random access memory. Might be good to replace tape drives. It's several years off though, but money keeps coming in and development continues. Should be nice stuff, keep on the lookout for it.
I saw development stuff in use a year ago when touring that laboratory, so I reserve the right to be incorrect or inaccurate with some of the statements in this post.
Mike DeMaria
It's the FBI, we're being raided!
Quick, break out the spoons! Eat the evidence!
No, it is rewritable.
Perhaps denatured isn't an accurate description. I'm not exactly sure of the specifics as I can't remember, but it does involve either a specific protein or organic creature (bacterial maybe).
Whatever it is, the substance is rewritable and in a sealed container. Degradation is a valid concern, I don't know the status of that.
Mike DeMaria
I remember reading an article in the New York times around ten years ago, talking about how holographic storage was going go be the Next Big Thing. They talked about 1-cm cubes holding a gigabyte (GASP!) of storage. Of course, this was when a 65 MB 5-1/4" hard drive was large. Hopefully we'll eventually see some actual holo storage technology in common use... eventually. I'd hate for this technology to become yet another of those things we always hear about but never get to have.
"Destroy science and religion. Science would re-emerge exactly the same; but not religion." - Penn Jillette, paraphrased
I have recently written a paper on this area for a photonics course. The inherent problems of 3D data storage are numerous to say the least. The only way currently to write the data is by way of laser, which also creates a problem of cross talk between the layers of the lattice structure of the recording medium. There is currently research being performed to eliminate this problem by utilising a dual-laser writing technique that would create only constructive interference at the position of recording.
The other major problem is the type of laser used. A pulse laser writes and retrieves data faster, yet is known to damage the recording medium. The solution is to use a high-powered contiuous-wave laser, which is being looked into.
The real decider in whether holographic memory is whether or not a certain compression of data can be reached. Off the top of my head I think it is somewhere around 10 megabits of data per square cm. Last I knew, I believe it was somewhere near 1 megabit per square cm. This is a really facinating topic, and I encourage all to look into it for themselves.
Ciao.
nahtanoj
Volumetric storage, where data is stored all through the volume rather than just on the surface, is a obvious idea that's been tried a few times but has never really worked. DVDs have a little of this, with several layers accessed by adjustable focusing. The coincident-beam laser scheme is attractive in theory, but requires beam-steering, which is mechanically messy. Still, mechanically messy concepts have been turned into mass-market technology before; look at the innards of a VCR.
Stable, write-once volumetric storage might be useful as a backup and distribution medium. That may be a more promising direction than something that degrades with time.
Corning Glass once built a computer display device using a photochromic plate for image storage. The plate was written with a UV CRT, erased with a bank of IR lamps, and read with a green light. It looked like a microfilm viewer, with rear projection. A few units were built and the idea dropped. This is one of the few products, other than photosensitive sunglasses, ever to use photochromic technology.
But one thing you can do very efficiently with photorefractive crystals is comparing images (at some Terabit/s). This is because to calculate the correlation of two images (which tells you if two images are similar or where a smaller image is located in an image) you need fourier transform the images. Optically you can do a Fourier transformation very efficiently simply with a lens (in 10^-10 s = 100 ps): at the focus of the lens you have the Fourier transformation of the image and the time you need is just the time the light has to cover the distance of a few centimeters. A good image comparing system can be useful for military applications (guided missiles), security checking (fingerprints, face and voice recognition), person tracking, internet traffic filtering,... All dreams for the NSA, horror for me!