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3D pics made using visible light
Danny Rathjens writes "David Brady of the University of Illinois at Urbana-Champaign and colleagues combined two kinds of technology --
computed tomography (CT), which is used to scan the inside of the body, and interferometry, which makes it possible to see
an image without focusing on it, to make 3D pictures using visible light. "
Why is it that computer folks do not understand the true meaning of 3D? Remember the View-Master you had when you were a child? *That* was 3D. Any image that is projected on a single monitor cannot possibly be 3D. It may be a 2D projection of a conceptual 3D image that you can rotate to view from different 2D perspectives, but it cannot be 3D. For true 3D, you need either an actual 3D physical object, a hologram, or a stereoscopic view--a slightly different view from each eye, like the View-Master. There are some nice, inexpensive 3D viewers available on the market for viewing images of nature and other things. Check them out at http://www.3dstereo.com. (I have no connection with these guys.)
Russ
[closeup of you, 10 years from now, you're at your desk maintaining the www.microsoft.mil website. Suddenly the phone rings..]
"Hello? .. Hi! What's up? .. .. uhh. .. hmm .. but .. .. .. Honey, she was only a few beams of light to me. Honest! .. .. No, no.. There's no need for the magnet.. Consider her deleted. Today. I know. Love you, bye.. *click*" .. Damn you David Brady! Damn you University of Illinois at Urbana-Champaign! aahhhh!
[you run out of your office and into the street where you are hit by a bus]
Moral: Good technology also has a bad side.
This can only be considered good if you're on the same side as the SWAT team... and remember, the cops aren't necessarily the good guys... especially in, say, China...
They were shining light thru skin and measuring some parameter X that was correlated with sugar level... Could the kind of interferometry described here give better results? ie better correlation?
Another $5e6 idea... nah! nobody cares ;)
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"Hasta la victoria siempre!" El Comandante
Oh well, replace $5e6 by $5e-6 in my previous post ;)
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"Hasta la victoria siempre!" El Comandante
Reconstructions based on X-rays depend on the fact that everything allows at least a little of the X-rays through, so you can always get some information from each ray. Fillings are pretty much opaque to X-rays, and the result is huge regions of the scan covered in streaks where the contents could not be reconstructed. Since the real world is full of objects that are opaque to visible light, I'm guessing that the technique at work here is pretty dissimilar to X-ray CT.
--
Employ me! Unix,Linux,crypto/security,Perl,C/C++,distance work. Edinburgh UK.
Xenu loves you!
I have heard several rumors about a Swedish company that should be developing remote virtual retina projectors... that could project laser images on multiple people's retinas at once from a distance of a couple of meters. A friend of mine actually claimed having met one of the people who were working on it. I have no other information, sorry.. but it should be thrustworthy because I have multiple sources. Is there anyone who knows more about this than I do who can tell me more?
"We mustn't be caught by surprise by our own advancing technology" -- Aldous Huxley
We're not by any means ready for holodecks yet. But this is certainly another step towards that...
Step 1 was photography.
Step 2 was holography on those little silver things.
Step 3 was the "matter laser" (so far working but still experimental, it works similarly to a laser but with matter waves)
Step 4 was the 3-D camera.
Step 5 is 3-D television; getting it working without glasses and whatnot.
Step 6 is synthesizing matter with the matter laser.
The last step is doing 3-D TV with the matter laser, allowing for solid holograms.
So we still have a way to go, but nevertheless this is a significant advance.
I thought I saw this on the Hash mailing list about a week ago, pretty cool stuff.
-Ben
bensmith@biz1.net
Brady's research was funded in part by the Department of Defense Advanced Research Projects Agency (DARPA), which he said would like to use it for military applications.
A camera that worked without having to focus would be ''smarter,'' he said. ``They have cameras spread throughout the world -- a lot more cameras than people,'' he said. These include camera viewing from satellites.
Got that warm and fuzzy feeling, uh-huh.
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DNA just wants to be free...
If the technology ever hits the commercial market, it'll likely be a bag of several hundred little marble-like sensors that you scatter around the area you want to film. They'd communicate using RF or IR or something wireless, and you'd have a receiver hooked up to your box that would collect the data from all of them.
Then, you'd run the happy little proprietary number-crunching software and it'd build the 3d models for you. Probably not in realtime, for a desktop machine.
One difficult thing, though, is that you need to know the relative locations of all the sensors at recording time to some decent level of precision (i.e. they need figure out where they all are relative to each other, or you need to indicate their positions somehow, in 3d yet), or the data is pretty worthless. You could I suppose lay them out on a gridded mat or similar, but that's not convenient for filming in a lot of settings.
By the way, if USB were still involved, while USB is kind of complex to hack, the groundwork for Linux generic USB support is pretty much laid now. It might not be as bad as you think.
Not like it matters; most of the magic here is in the user-land signal-processing software, not the device drivers. (don't think the algorithms aren't patented; fat chance seeing libre software doing this anytime in your lifetime)
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DNA just wants to be free...
Read my speculations on how it works:
Hrm; I just discovered these people's site on a post below, too... it looks like my conjectures were pretty dead on:
http://www.phs.uiuc.edu/4Is/
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DNA just wants to be free...
They were shining light thru skin and measuring some parameter X that was correlated with sugar level...
Could the kind of interferometry described here give better results? ie better correlation?
No, just more accurate measurements. Which might improve results, but not the correlation you're measuring. The actuall degree of correlation doesn't change. There's an analogy in applied statistics: more careful measurements don't help if your samples aren't any good.
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DNA just wants to be free...
One shot, and they've got my whole house mapped out, right down to the ant crawling on the floor. When they come to bust be for hacking my grades on the school's system, I'll have no where to hide.
Screw petty computer criminals; think of the potential this has for suppressing those nasty political dissidents!
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DNA just wants to be free...
I suspect the way it works, since they brought interferometry into it, is that they have a large number of small sensors (mini-cameras) scattered around and throughout the area being "filmed".
You'd have to apply algorithms similar to those used for CT to reconstruct the a 3d model from the data from the sensors, and interferometry comes in to play to compensate for the low spatial resolution of the individual sensors (as well as removing the need for them to be "focused" -- the more sensors, the sharper the detail).
Of course you'd still have problems with opacity, but with enough sensors scattered around that wouldn't be such an intractable problem. You just couldn't see the insides of stuff that you didn't have a window of some kind into and couldn't put a sensor inside of.
Stuff wouldn't need to be in full view of all of the sensors, either -- just, the fewer sensors that can see a feature, the more fuzzy ("out of focus") it'd be.
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DNA just wants to be free...
Big deal, FreeBSD and NetBSD have working USB stacks already; what happened to Linux's leading edge? ;)
*obvious flamebait*
no no no :-) On the hash mailing list it was 3D scanning using a PENCIL :-)
i ndex.html
http://www.vision.caltech.edu/bouguetj/ICCV98/.
oooh and theres code as well . MSoft Boo !!!
no, a pinhole camera 'focuses' from nearly zero out to infinity. those disposables foucus from around a meter or two out to infinity.
this is because the pinhole is very small, while the camera lens is relatively wide. it gives great depth of field.
and to all those saying that IR cameras can see through walls, you must have awfully thin walls!
Everything should be made as simple as possible, but not simpler. -- A.E.
"Help me obiwan kenobi... you're my only hope!"
_______
2B1ASK1
Okay, when will gtk and qt have widgets for this?
A Government Is a Body of People, Usually Notably Ungoverned
Hate to freak you out even more, but they can already do that using infrared cameras. Your local police force probably has a few.
It would be illegal to do it without a warrant, just like tapping a phone.
Does anyone know where to get rolls of Mylar on
the web? I want to make some huge solar
furnaces this summer.
We've finally made it to good 3-d 2-d images (Quake being the obvious example). The next step is some type of "actual" 3-d image. The possible uses for this are amazing with as much media as we (U.S) process in this county. How many of you thought "holodeck" about halfway through this story? How about watching and being able to walk around the set? Entertainment seems to be the next step (after we find better ways to kill each other). Looks good, anybody knows where we can see samples?
+&x
The group has a site at http://www.phs.uiuc.edu/4Is/
It includes a pretty spiffy mpeg of one of their scans. Cool.
Point the bastard at it's viewing station. Have it figure out what a complete picture of the world looks like.
Variation. Switch the audio and video cables.
Must include Pentium processor with Floting Point Division bug.
The ship sank. Get over it. (This sig was cut out from another's shirt and painstakingly hand-posted)
Is this implying that a laser is not visable light.
..
I know what they mean, but it could have been stated _much_ better.
I couldn't tell if you were experimenting with poor-man's cryogenics or looking for the orange sherbet.
I want to know when Logitech is going to release this technology in a quick cam (hopefully not USB so it's easier for the guru's to try to hack a linux driver for it)
Tell a man that there are 400 Billion stars and he'll believe you
Say the Gov't COULD take a 3D Ir or Microwave snapshot of my house; how would this impact privacy and search 'n siezure laws? Say I don't let the nice FBI agents in because they don't have a warrant; so what......POOF, they just took a detailed picture of my place down to the last square inch. Was that an illegal search or not?
Hmm. Ah, everyone needs a big brother!!!
~Any apparent grammatical or typographic errors are caused by defects in your display device.
Hubec wrote: "It would be illegal to do it without a warrant, just like tapping a phone."
Ahh, but they are supposed to obtain a warrant to do that as well; that is why the wiretap laws become ever more dilute!
~Any apparent grammatical or typographic errors are caused by defects in your display device.
The news article motivating this thread arises from this article in yesterday's issue of Science: "Visible Cone-Beam Tomography With a Lensless Interferometric Camera," by D. L. Marks, R. A. Stack, D. J. Brady, D. C. Munson Jr., and R. B. Brady, Science Jun 25 1999: 2164-2166 There is a better news article in describing the work in Science itself: "3D Camera Has No Lens, Great Depth of Field," by Daniel Radov, Science Jun 25 1999: 2066-2067. These are available through Science's web site, but a subscription is required. Science offers a 1 day subscription to the web site.
The paper uses a combination of interferometric imaging algorithms (which image with infinite depth of field ) and computer tomography algorithms ( which combine infinite depth of field images to produce 3D models) to produce a 3D image of a plastic toy. Opacity is not a problem due to the linearity of the imaging process.
As several posters have noted at this site, pinhole cameras also have infinite depth of field. We wrote an paper about using pinhole cameras for tomography in Optics Letters last year. Unfortunately, the depth of field of a pinhole camera comes at the expense of resolution. This is not true of interferometric cameras.
"Interferometric" refers to measurements of cross-correlation functions to isolate intensity contributions from different points in the object space. The algorithms used are very similar to those used in radio astronomy.
"Tomography" means slice (tomo) plotting. "Computer" is the C in CAT scan or CT. Current usage applies tomography to most 3D imaging schemes. "Coherence tomography" is a point by point scanning scheme which, ironically, is not tomographic at all. Tomography allows parallel data acquisition, which ultimately leads to real-time 3D video and holodecks. Real-time 3D was not demonstrated in the Science article, however, because it requires a dense sensor array. See http://www.phs.uiuc.edu/Beowulf for progress on this front.
Concern about DARPA and big brother issues is unnecessary. A sensor array has no better chance of seeing inside opaque objects than a single camera. Anyway, why should big brother waste a lot of effort to get information people will volunteer in exchange for supermarket dicount cards.