Part of the show Combating Climate Change
What you Need
What to do
First of all, this experiment has a high probablility of damaging your webcam beyond repair, so please use an old webcam and don't complain to us if it breaks.
The sensor in a webcam is sensitive to both visible and infra red (IR) radiation so the manufacturer adds a filter to stop the IR, otherwise it would produce unexpected results when it took photos. So we want to remove this filter and replace it with one that stops visible light but allows IR through.
What may happen
As we have seen in another kitchen science, a remote control looks different in the infra-red. This adapted camera is much more sensitive and so you get a fascinating view of the world...
First we had a look at some light sources:
Objects in the Near Infra Red
Then we had a look at some objects...
As is possibly obvious, we at the Naked Scientists found this absolutely fascinating, and I would strongly recommend you opening up a old webcam if you have one you are not attached to!!
Why does it happen?
Your webcam has a sensor behind the lens which is sensitive to most colours of light and IR (and also ultra violet). It has a filter on the front which stops the IR, and then a series of filters on the sensor chip itself to only allow one colour through to each sensor on the chip so they can detect different colours.
When we just let IR into the camera by putting our filter on the front it will pass through all the coloured filters to slightly varying degrees, as these filters are not designed to stop it.
Why is my webcam sensitive to IR anyway?
Webcams detect light by having lots of small sensors on a piece of silicon. Each of these sensors is a small diode - a one way valve for electricity, and the electronics is trying to push electricity the wrong way through this diode.
This normally doesn't work because a diode is designed so that there are no free electrons to carry an electric current when you try and push electricity the wrong way. But if a photon of light with enough energy hits the middle of the diode it will knock an electron off a silicon atom which can now move and carry electric current. The electronics then measures this current and so how much light has hit the sensor.
Any colour of light above the mid infra red (so near IR, visible, UV etc) will have enough energy to do this, so your camera is sensitive to infra red light. More expensive CCD chips found in real digital cameras work slightly differently but on the same principle, so they are also sensitive to IR.
I've lots of experience with infra-red cameras. Most black and white "security" cameras don't have any IR-blocking filter, so you don't need to take them apart. Just add a visible-blocking filter (black exposed negative film etc) as described.
I'm a science teacher, this is a fantastic thing for me in the classroom. Works great! thanks guys. One word of warning if any other teachers plan to use it in class. I pointed it at my wife and her bra showed up straight through her otherwise opaque top. Might get yourself into some trouble and cause some significant embarrassment if you go pointing it at girls. Suggest if using it in class you keep it away from the girls.
Monochrome Infra-red film for 35mm cameras is available while stocks last ...
Old webcam stripped down and ready, now i only have to find the drivers for it!
I have no idea what the software is doing. What does the result look like? Does it work when the room is dark and you illuminate something with a remote control, or is it just an aesthetic thing? daveshorts, Tue, 29th Jan 2008
I have a 'night vision' on my webcam, but all that is is a row of leds beneath the camera that illuminate the subject, so there is no actual light detection outside the visible spectrum. I cannot say if this is anything like what your webcam is doing. another_someone, Tue, 29th Jan 2008
I also bought a cheap 'night vision' webcam. All it is, is a webcam with some high intesity LEDs that kick in when it gets dark.
At long last, I have my infra red camera working...and working well.
I have noticed that the infrarred light of the TV remote control can be seen as a blue light on with my digital camera, but...why blue and not red?. It is strange that IR light excites de same detectors or cross the same filters as blue light, instead of exciting the red ones. Pedro, Wed, 23rd Sep 2009
Hehe. This is deeply cool. You should all do this ;) rosy, Thu, 5th Nov 2009
This is aweosme, but is it possible to detect UV with a webcam like this, I am looking at measuring combustion efficiency looking at flames through a webcam..tIs there a lower wavelength limit just like the upper wavelength limit for the commercially available webcams? Thanks and regards Gopakumar.S Gopakumar, Tue, 17th Nov 2009
hi, great topic i want to turn a still camera to use in nighttime for animals i was told i can remove a IR filter, have you done this before and could you explain to me how, regards Ron Ron, Sun, 3rd Jan 2010
I tried it with my salvaged CCD security cameras. One thing to note is the change in focal distance. After removing the filter (I tried to grab the filter with pliers, and got crushed glass in my eye, that was stupid of me - a slight push to the side was enough) a regular 3.5mm lens could not focus the image, so I used a 6-60mm zoom lens. It works great (seeing in the dark, through clothes and dark transparent plastic). You can still see light from my small IR torch (12 small IR LEDs) without removing the filter, yet when you remove it's 100 times stronger :) I'd thought my IR torch was weak, but it was just the filter. Thank you for this article. Technoshaman, Thu, 30th Sep 2010
@Gopakumar: As far as I know, the sensor of the webcams are limited to the VIS & IR range only. You can get lucky by using the sensor of a DSLR which captures a tiny bit, and then using long exposure to get pics. E, Thu, 13th Jan 2011
Glad to see it is here! I work in forensics and the near infra-red (NIR) is used to distinguish pen inks that look the same to the naked eye but are different under NIR... like a few zeros added to a cheque with a different pen. ....Of course ... for bank notes... Dyes are transparent to NIR but not pigments. Dyes get their color from being in solution while pigments have their color just as being a solid. Chlorophyll in plants gets its color from being in solution. It is a dye and this is why green plants look white in NIR.
I was shown this page after having just completed this hack on a webcam myself! It's great fun isn't it? Am now wondering how easy this would be to do with mobile phones.. I love the explanation and examples here - and the £5 trick is really cool! Works with a £20 too... ;) Matt, Thu, 12th Apr 2012
If you have an LCD microscope or one with a USB camera, switch it to B&W mode then put flower petals on the specimen stage and illuminate it with a remote control. You will see wonderful markings and designs that only Bee's and Hoverflies ever see! They are awesome. Insects also are seen in a new "light" pun intended. See the pics below!