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By now, many of you have heard the grand flap about infra red security cameras, and how they let you see in the dark. Fine, fine.
What about making a security camera which allows you to spot microwave radiation. Since it has a shorter wavelength than infra red or visible light, you could get better
resolution with the same size lens.
Since cell phones operate on microwaves, they should help to illuminate the area rather nicely, especially now that they are increasingly popular, and if not, well, supposedly that sort of radiation is "safe," so a few microwave emitters could light up the room if need be.
OK. so, better resolution with cameras the same size, or smaller cameras with the same resoluton. That's nice, but why am I so hot for microwave cameras?
Well, first off, with this sort of camera, a cell phone that hasn't been turned off would blaze out like a forest fire. That could be useful in high security areas where cell phones are not permitted, as well as in libraries and schools.
Secondly, the human body is partially transparent to microwave radiation, but metal is pretty much opaque to it. Thus, a simple camera might provide enough of an image to spot guns, knives, and... umm... stolen hardware... on a person without making them pass through a metal detector, and without pumping x-rays all over the place.
BAE + roke: CELLDAR™
http://www.roke.co.uk/press/38.php
This came out in 2002, but hasn't really been written about much after 2003. I don't know whether they got anything to work. [jutta, May 25 2007]
Wikipedia: Passive radar
http://en.wikipedia.../wiki/Passive_radar
The overall genre, without limiting oneself to cellphone microwaves. [jutta, May 25 2007]
Space-time Microwave Imaging (MIST)
http://www.warf.ws/...5&casecode=P01386US
"Because the intrinsic contrast between malignant and normal breast tissue is much greater at microwave than at X-ray frequencies, MIST could allow detection of extremely small (i.e. millimeter size) breast tumors, and reduce the number of false-negatives associated with conventional X-ray mammography." [jutta, May 25 2007]
Microwave imaging technique
http://www.freepate...ne.com/5248977.html
A microwave lens is a set of waveguides. [Ling, May 25 2007]
Annotation:
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i like it, but how would you build the image? glass is transparent to microwaves. maybe some sort of passive radar? could you make the system just plain old 'ping' radar, and lower the power? you'd probably need some sort of phased-array to shift the beam without moving parts. |
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also, i thought microwaves were longer than visible light waves. wouldn't that mean a lower resolution? maybe better to use gamma rays - that would not only illuminate the subject pretty well, but allow you to see his chemical composition. |
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//Secondly, the human body is partially transparent to microwave radiation// |
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Which is why you can't cook human flesh in the microwave oven, right? |
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Nice how $DIETY created us with a different cell structure than every other living thing on the planet, all of which can be cooked in microwave ovens. We are unique in that we are transparent to microwaves.(-) |
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Hey! The poster *did* write "partially". |
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Google "terahertz imaging" |
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The signal processing side of this looks hard - with all the scattering and reflections, this isn't just another flavor of X-ray. Looks more like waving an antenna around, not exposing a piece of electronics or chemistry. (But see Ling's link for a way of translating one to the other, maybe.) |
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//Nice how $DIETY created us with a different cell structure than every other living thing on the planet, all of which can be cooked in microwave ovens// |
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I take it that your microwave oven only cooks the outside of your meat? My microwave operates more efficiently than a conventional oven because the energy is radiated into the food, and does not need to be conducted through from the surface area. |
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Lenses will admittedly be difficult. However, in a reasonably small area with several doors... or anywhere that is likely to see a lot of "harmless" metal moving around, this idea still might be more logical than a bunch of four thousand dollar metal detectors. |
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Microwaves also have lovely effects on conductive items especially those in thin films, like compact discs and credit cards. Toss a CD in the microwave for a few seconds and see what I mean. I recommend you use one that you don't like anymore. |
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My initial point was that compounds of water and fats are far from transparent to microwaves, which will rarely penetrate past the first few centimeters. And they are not reflective of these rays at all. I suspect your imaging system would have to settle for muddy shadows of people dancing through your room as they leap about and scream from all their metal accessories heating up. |
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//I suspect your imaging system would have to settle for muddy shadows of people dancing through your room as they leap about and scream from all their metal accessories heating up.// |
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That'll certainly keep folks with metal weapons away. However, I predict, that since I do not leap about in agonizing pain from my metal accessories when I use my cell phone, it must require a certain minimum level of radiation before such problems occur... or perhaps the exact wavelength that cell phones use reacts with water far less than the wavelength used to cook food. |
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In the mean time, clothing is generally less than a few centimeters thick, and lacks most of the water molecules that cause problems with organic tissues, but metal, any way you cut it, interacts with microwave radiation differently from organic materials. |
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The real question then is whether we can get a workable picture with a level/wavelength of radiation low enough to prevent undesirable effects. |
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//Since it has a shorter wavelength than infra red or visible light, you could get better resolution with the same size lens// |
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Rubbish. Microwaves are longer wavelength than visible light. Resolution is worse. |
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Well spotted [custardguts] - don't know how that howler snuck under the radar. [-] |
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