Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
Not so much a thought experiment as a single neuron misfire.

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



Heated License Plates

CCDs deal poorly with heat
  (+9, -3)
(+9, -3)
  [vote for,

This idea presumes that red light infraction cameras use digital, or CCD imagers. I know some use film and this invention won't work for film.

I propose a heating element be adhered to the backside of the license plate to heat the plate to 200-300°F above ambient temperature. Maybe more....

If a license plate is strongly heated, the resulting digital image of the plate will be blown out, overexposed, because CCDs are sensitive well into the IR range.

Depending on how much IR filtering is present at the imager--and most have IR filters but can't completely eliminate IR--the license plate may be unreadable.

As a do-it-yourself proof point: If you have a digital camera or camcorder point it at, say, a candle, and see that a large vertical spike of light surrounds the hot spot and that the candle flame itself has virtually no detail. It is upon this observation that I base this idea.

Yes, the idea has weaknesses. It requires experimentation to see if it works and, if widely adopted countermeasures could be implemented, but it would also be virtually undetectable by visual inspection.

bristolz, Oct 15 2005

WA Post: "Drivers Try an Anti-Photo Finish" http://www.washingt...A222-2004Jul20.html
Talks a bit about this subject and some of the thing people are trying as well as the gist of the laws that govern license plate legibility. [bristolz, Oct 16 2005]

About.com: "License Plate Brackets - Can You or Can't You?" http://austin.about.com/b/a/028567.htm
An article talking about Texas law prohibiting many license plate frames and all covers. [bristolz, Oct 16 2005]


       Good idea but bad solution. You could indeed flood the camera with IR light and the best way to do this would be to inset lots of IR LED's into the plate. The type they use in remote controls would be perfect. On the picture you would just see a bright spot and with human eyes you would see nothing. Heating the plate to create this amount of IR light would take a lot of energy from your alternator and the police would spot the heat-wave/melting plastic miles away!
AliMon, Oct 15 2005

       But they wouldn't notice all the holes drilled in the plate for the LEDs?
bristolz, Oct 15 2005

       A small point, but could we maybe use these to defeat speed cameras instead of red light infraction cameras. Jumping red lights strikes me as being just the wrong side of too dangerous - maybe because I live in London. Interesting plan though, cameras such as these have proven fairly simple to fool in the past.
wagster, Oct 15 2005

       no need to drill holes.. just a plastic cover layer - I don't have any holes drilled in my tv 'information panel' the leds just shine through. To look at its just a piece of plastic
AliMon, Oct 16 2005

       But plastic covers are illegal in many--most--jurisdictions.
bristolz, Oct 16 2005

       During a Canadian winter the steam alone may be enough to obscure the picture.   

       No, I don't get out much lately. I have, however, often wondered how to defeat cameras in general and know that IR sensitivity is an Achilles heel in digital imaging systems and a weakness I have witnessed myself. As one example, many camcorders are able to "see" their remote control unit's light signals and show them as a vaguely bluish light in their resulting video. Really, though, this is just speculation posited as an invention idea and I haven't any real practical experience or knowledge to back up my claims.   

       In better cameras there is an IR filter applied directly in front of the CCD itself but they are not anywhere near 100% effective and can be overcome through sheer volume of heat.   

       Another approach might be to use powerful strobes which could be IR or visible to illuminate--blowout--the license plate and that are triggered sympathetically by the flash on a speed or traffic camera. It'd be an electronic showdown of sorts and, if fast enough, could severly overexpose the image.
bristolz, Oct 16 2005

       Could someone break this down for me dummy? I have no clue what is being discussed. I mean, I'm not totally raisin brained, but this time, just add some flakes, and I'm there.
blissmiss, Oct 17 2005

       In normal photography if you flood an object with really strong light, that object will be overexposed and will have very little or no detail captured in the image.   

       In infrared imaging heat (well, IR) essentially replaces visible light as the thing that creates the image, or photo.   

       Digital cameras are sensitive to both the visible light of normal photography and, to a lesser extent, to infrared light (heat).   

       So, this idea takes advantage of a digital camera's infrared sensitivity by flooding the object of the photo with a very "bright" source of heat with the intent of causing overexposure and loss of any detail.   

       A heated license plate will perhaps blind the camera but remain essentially undetectable to humans (police).   

       Flakey enough, bliss?
bristolz, Oct 17 2005

       The candle experiment is flawed - it is probably not heat that is causing the CCD charge to leak, but some of the short wavelength IR from the point-source - don't forget you'll get a broad spectrum from a candle. The sorts of wavelength (long) associated with heat are usually pretty effectively stopped by the camera's glass optics. Try pointing your camera at an electric hot-plate on a cooker.

It is possible to buy Wratten IR filters (87 A-C) that look to the eye to be opaque, but are transparent to the short wavelength IR used by traffic camera illuminators.
For a UK licence plate, if you cut the numbers and letters from this material and stick them to a standard retroreflective backing material, you'll get a pretty good IR-invisible plate.
Yes, I tried it in a lab with a real traffic camera (Pearpoint) and illuminator, and it worked.
Won't work with film-based or non-IR TV systems though. You could put a bank on IR LEDs behind the filters for dazzle, but that wouldn't then work for film or IR cameras!
Haven't tried the slave-flash approach. Bun for a kindred spirit.
coprocephalous, Oct 17 2005

       Sure bris, sure. (Coming from someone who forgot to _put_on_ her_ front plates this year, sure bris).
blissmiss, Oct 17 2005

       I thought there were already penalties for using hot license plates?   

       But seriously, while this does seem to have a good chance of working, I always wonder about "solutions" to traffic violation problems: what's wrong with not jumping red lights in the first place?
DrCurry, Oct 17 2005

       // I thought there were already penalties for using hot license plates?//   

       I've been waiting for that.
skinflaps, Oct 17 2005

       DrC it's just an invention idea. You can argue against any invention idea by suggesting that people just not do whatever it is that the invention is designed to do or assist in doing but where's the fun in that?   

       Maybe the addition of a dither generator could help smear the image too. Might be too noticeable, though.   

       [coprocephalous] Do you know what the shutter speed of the typical speed/traffic camera is? Maybe it'd just be altogether simpler to vibrate (dither) the plate using a small motor and an eccentric shaft with the plate mounted on short springs? If the dither distance was great enough and the frequency high enough maybe the results would be unreadable.
bristolz, Oct 17 2005

       I did say I thought it would work, and my croissant is sitting there somewhere up top - I just have this "least effort" preference for problem-solving, and was wondering if there were more pressing problems this might help with (paparazzi, for example). Less importantly, I also think that if any measure designed to beat the law is effective then it will, like radar detectors, itself be outlawed.   

       Perhaps I should post my idea for a shoplifter's bag.
DrCurry, Oct 17 2005

       Point taken. It may be outlawed.   

       There are paparazzi camera beating systems making their way through research now.
bristolz, Oct 17 2005

DrCurry, Oct 17 2005

       How about just designing some very bright IR LEDs to replace those little license plate lights some cars have?
Worldgineer, Oct 17 2005

       I liked my approach simply because it isn't visually obvious.
bristolz, Oct 17 2005

       Ah, but these custom LEDs would have the shape of regular bulbs, and even contain a regular incandescent filiment to disguise their true purpose.   

       Perhaps yours is more elegant, however.   

       (picturing a mirror image of a license plate seered to a garage wall)
Worldgineer, Oct 17 2005

       [half] I doubt the finish could withstand the heat but, hey, nothing's perfect.
bristolz, Oct 18 2005

       bris, is there anyway to make this more, well, dazzling? Or is this practical, and/or, god forbid, useful?   

       I admit to still not having a grasp on the idea, but I will bow to yer brilliance as always. Just this time though, you...you buggarly brilliant beacon of brightness. (And no, you don't get to ask what buggarily means, it's a secret.)
blissmiss, Oct 18 2005

       bliss, short of having you sit on the trunk, perhaps naked, waving at the traffic camera, this one is a bit dazzle free (unless you can see into IR).
bristolz, Oct 18 2005

       That may work too. I doubt anyone would remember to give you a ticket. Watch out for the hot license plate though.
Worldgineer, Oct 18 2005

       we'll see.
bristolz, Oct 18 2005

       Lord help us.
bristolz, Oct 18 2005

       Maybe you could just make the lettering the same colour as the background....
wagster, Oct 18 2005

       Actually, that is precisely what bristol's scheme will do, except the color is in the infrared.
DrCurry, Oct 18 2005

       It seems, to me, that an Infra Red flash unit might be useful. Strangely enough, I have never seen one.   

       By the way, at work I can take photographs of steel slabs at 1100 degrees C, using a Sony digital camera.   

       What can cause a problem is local over-exposure on the CCD. If the slab covers the whole CCD area, the exposure is OK.
Ling, Oct 19 2005

       [Ling], you keep giving us these nuggets of information about furnaces and large amounts of very hot metal. What exactly do you do?
wagster, Oct 19 2005

       //What exactly do you do?// Makes stealth numberplates for very large cars?
coprocephalous, Oct 19 2005

       [wagster], I work at a place that has furnaces and large amounts of very hot metal ;^)   

       More commonly known as a Steelworks.
Ling, Oct 19 2005


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle