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Visible Light 'X-Ray' Sees Through Solid Objects
disco_tracy writes "Some day we may not need X-rays to see inside people, thanks to a new way to decipher light that passes through opaque surfaces. Normally visible light becomes too scattered to detect after passing through opaque surfaces. But scientists in France have developed a way to reconstruct images from light passing through such surfaces by deciphering just how the material makes the light scatter. In the short term the research will help improve the strength of telecommunications signals and fiber optics cables, but years from now the technology could supplement or even replace traditional ultrasounds for baby imaging and X-rays for weapons detection at airports."
This will make the "xray" threads on /b/ waaay more interesting.
There's no -1 for "I don't get it."
This is a pretty cool idea, but it will probably not take the place of x-rays. X-ray is cheap, easy, accurate, and relatively harmless (in small doses).
This sounds expensive, requires a large amount of processing capability, isn't very portable, and relies on light actually passing through the object. For some applications this may be useful, but for the vast majority of imaging tasks that require visualizing the internals of an object, x-rays will be the better solution.
Now, an x-ray scanner that didn't require film plates. That would be good!
How does visible light make its way through an opaque object?
I want to delete my account but Slashdot doesn't allow it.
How does visible light make its way through an opaque object?
I know you aren't supposed to read TFA, but ""It's like putting a flashlight behind your hand," said Sylvain Gigan... "You cannot see an image, but you can still see a faint glow.""
That's exactly what I thought. It's a poor choice of words, in my opinion. Opaque by definition means that it blocks light from passing through it, but I just figured it was some kind of quantum mechanical thing, just like all the other physics I don't understand.
Funny may not give karma, but +5 Informative never made anyone snort coffee out their nose.
No. Reading is useless without understanding. The OP was correct in asking. Your hand is not opaque, it is translucent.
"National Security is the chief cause of national insecurity." - Celine's First Law
I say why stop at x-rays. Gamma rays are too good for them.
I know you aren't supposed to read TFA, but "'It's like putting a flashlight behind your hand,' said Sylvain Gigan... 'You cannot see an image, but you can still see a faint glow.'"
I think it would help if TFA included an actual example image, and not just a photo of someone holding their hand up behind a shower screen and a note to the effect that the actual technology might produce images sort of like that one.
"...always new atoms but always doing the same dance, remembering what the dance was yesterday." -Richard Feynman
Not likely (in the US at least). Kyllo V United States established that using IR to peer into a home requires a warrant, and that's a pretty strong precedent. A key issue of the case was that using IR didn't even need to penetrate the house (it just "recorded" what was being emitted) and yet was STILL not allowed without a warrant. Anything that "peers in" will be just as illegal.
I live in constant fear of the Coming of the Red Spiders.
I guess the first question is whether something can be truly opaque (zero light travels through) or whether all things are translucent if you've a sensitive enough detector.
Assuming that there are genuinely opaque objects, are there enough objects that are translucent (though not to the unaided eye) to make this technique interesting?
My guess is that almost everything will be translucent, though not everything. If the gaps between atoms is on the scale of the wavelength of light, then the atoms will act as a diffraction grating. Given the number of such gratings light has to pass through for any meaningful object, that's going to make a serious mess of the observations.
In order to be truly opaque, two criteria must be met - every photon has to intersect a particle and for every such intersection, the particle has to be able to absorb the photon. Since matter is mostly empty space, you'd need an awful lot of particles to absorb all photons. However, I can see no obvious reason why it would be impossible to have such an arrangement.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
unless wikipedia is wrong, which is impossible
You make me want to go and edit the elephant entry again. ... Or maybe go and randomly edit something I know nothing about basing all my information off of other wikipedia articles, quoting them for authority. I think I might combine something about army ants, satellite antennas, and low-end computer speakers. Or maybe I'll just add the word "not" in front of a significant statement in one of the articles related to a student's upcoming paper to see if they bite the poison apple. Anyone else with me?
Amazing! A friend of mine has done his Ph.D. in exactly this field. He was shining a beam of light right THROUGH an opaque sheet of material (paper, I think) already a few years ago, and published about it in 2008. I think it's pretty much the same idea, from what I understand of it (but keep in mind, I chose the evil path of Business instead of Science, so I have no brain).
Anyway; on his page there's a much better explanation, with cute pictures and all that, of the same idea.
Simple, on exit from the opaque object, the light has turned invisible. This new device can see the invisible light.
I've had this idea for a while now that low-heat, very bright LEDs are available as light sources: 1. take an existing CAT scanner: Xray source, detector, mounting system (with the rotating arm) and image processing software. 2. replace the Xray source with a bank of LEDs 3. replace the Xray detector (a scintillation screen? whatever it is) with a CCD 4. start scanning Obviously there's a whole bunch of experimentation needed to calibrate diffusion due to different types of tissue/bone/marshmallow but the software should be mostly unchanged, the mechanical mounting system would be mostly unchanged, and we'd be replacing a radioactive source with a low-power, low-heat light. Is anybody working on this? I've asked a couple of professor at a biomedical engineering department but much silence ensued. The ability to use off-the-shelf components seems like a big plus to me... There would also be a need to check at what intensity cold light is detrimental to cells (and other small issues like that)
The actual "FA" is here, with images. Gigan, et al. say, "opaque materials."
Credo sim. - I think I am.
Thanks to quantum tunneling nothing is ever completely opaque. A particle's path from A to B doesn't necessarily have to pass through all the points in between. Some tiny fraction of the photons will always act as though the object isn't even there.
"The state is that great fiction by which everyone tries to live at the expense of everyone else." - Bastiat
Nowadays, "illegal" doesn't mean you can't do it -- it's just not admissable in court.
You can get your last dollar they still do it, but then need to come up with a pretense for anything involving the courts.
Remember, they can now slap a GPS device onto your car with absolutely no court oversight. Just imagine all of the illegal things they do and cover with sealed court proceedings.
Lost at C:>. Found at C.
The idea is that you send light against an opaque medium, the photons getting blocked or scattered is a statistical process. Some of them, simply as a matter of probability, "sneak through" in a straight line.
To get around the low probability, you use a strong light source, modulate it (if you modulate the light, you can pick it out with a tuning circuit, so that you can screen out background light), and then average over a long period of time.
Eventually, you get enough ballistic photons through that you can map out an image.
Ultrasound is for listening to sounds inside the body, such as the faint heartbeat of an unborn human.
No it isn't. Ultrasound is ultrasonic, by definition. (Higher frequency than normal sound.) Ultrasound is often used for imaging; the resulting images are called sonograms. Ultrasound can detect heartbeats through movement (Doppler shifting the ultrasound waves). It's not for listening to normal sound waves originating from inside the body. That's just a stethoscope (or fancier variant thereof).
It just so happens that your object here is only MOSTLY opaque. There's a big difference between mostly opaque and all opaque. Mostly opaque is slightly transparent. With all opaque, well, with all opaque there's usually only one thing you can do.
It's called Ballistic light.
Eventually, you get enough ballistic photons through that you can map out an image.
And if you get the light strong enough, you resolve the opacity issue permanently, once the smoke clears.
A sonogram is the image produced by an ultrasound machine. Ultrasound imaging is called "ultrasonography."
Listening to sounds within the body is called auscultation.
"This is a double edged sword."
As is every single piece of technology that ever has, and ever will be, invented. Any progress in any field of study has both benevolent and malevolent purposes. Fire is used for cooking, also for arson. The wheel is used to transport goods, also make off with stolen goods. The hammer helps build things, and bash skulls in. Etc.
This new visible light "x-ray" can be used for spying or legitimate medical purposes.
The trick is to ensure that those in power do not abuse this technology. This is done by not allowing them to keep secrets. This is done by forcing information out of them, by deadly force if necessary.
-1 disagree is not a modifier for a reason. -1 troll, flaimbait, redundant, overrated are NOT acceptable substitutes.
Eventually, you get enough ballistic photons through that you can map out an image.
Physicists don't actually use terms like "opaque" very often. We are more likely to talk about material that is "highly absorbing" or "highly scattering". The human body contains lots of both.
One area where people have tried to apply this is in optical mamography: women's breasts are primarily fatty tissue that is highly scattering but very weakly absorbing, so you get a surprisingly large fraction of transmitted light. You have to do a huge amount of processing to deconvolve the scattering kernel, but when I worked in the area in the late '90's it was getting close to useful.
For people reading this who are female or who have wives or girlfreinds willing to go along, go into a dark room and hold a flashlight under your (partner's) breast. You'll be amazed by the amount of veinous structure and whatnot you can see. Squeeze the breast flat to get more detail. Insert joke here about how now you're in a dark room with a woman who has at least one breast exposed so you know what comes next...
Very athletic women with smaller breasts may not see much: the chest muscles are highly absorbing and any any photon that scatters into them is lost.
High-speed computation is making visible light a more useful medium of detection all the time, and the work described in TFA is an interesting step along the way.
Blasphemy is a human right. Blasphemophobia kills.
For the moment at least, a 4th amendment violation is still a 4th amendment violation even if they do not bother admitting any evidence they find into court. The court sanction of inadmissibility of evidence does not mean law enforcement is free to search and seize when they do not plan on admitting evidence. This came up in the past couple years when some jurisdiction started pulling people over for driving safely and giving them reward cards or coupons or something. It was still a seizure without warrant or probable cause and when this was pointed out they stopped since they were inviting a civil rights lawsuit.
If they gathered IR data without a warrant or probable cause and that lead them to further evidence gathering, the later evidence would also be inadmissible in court. As you point out of course, they can (and I am sure do) gather the IR data secretly and hide this from the court and the defense.
The circuit courts are split on the GPS tracking matter so it is likely just a matter of time before the supreme court gets involved. The secret court proceedings and administrative actions are more insidious to my mind.