Kitchen Science Experiments

Make an Infra Red Camera

Sun, 20th Jan 2008

Part of the show Combating Climate Change

What you Need

A webcam

An old webcam you are not fond of

Polariser

2 Pieces of polariser, or a totally black exposed negative

Some Odd Tools

Some odd tools

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.

Removing the Case

Sensor Assembly

First take the case apart, how to do this will depend on your webcam.

You should find inside a circuit board with a camera assembly on top. There should be a piece that holds the lens, this may screw in and out.

The sensor

Extracting the Filter

If you unscrew the lens you should reveal the sensor chip, this is the part that converts the image projected on it into electrical signals. Keep this safe and clean.

You are now looking for the IR filter this is a small piece of glass with a reddish or greenish tinge. If you are lucky it will just come off but in this case it is in front of the lens. We had to push the lens out using a soft pencil protecting the lens with some soft polythene.

Filter, Lens and Aperture

Put it back together

The filter (top left), lens (top right), and aperture (bottom).

Now you want to put the camera back together in the reverse order you took it apart, without the filter.

Polariser

Webcam

You now want a visible light filter instead. you can use a very heavily exposed piece of negative (the parts of a film you exposed when loading the film), or two pieces of polariser aligned so they are opaque to visible light.

Attach the filter to the front of your camera, with some tape, or make some sort of holder for them if you have the technology.

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...

Light Sources 

First we had a look at some light sources:

Ben

Ben in IR

Here we have Ben pointing a remote control at his head.

As you can see in the IR the room is very dark, but the remote control acts just like a torch

CFL

Two bulbs

In the visible range, turning on this very low powered lamp has virtually no effect on the brightness of the room, compared to the light in the ceiling.  The table lamp uses a conventional light bulb, but the ceiling light uses a compact fluorescent, or energy-saving, bulb.

CFL Bulb in IR

Two bulbs in IR

In the infra red the compact fluorescent is very dim, it doesn't even light up the room. It isn't wasting energy producing light you can't see.

The conventional light bulb on the other hand is probably brighter in the infra red than the visible, so it is is great for our purposes but not very efficient.

A Candle

A Candle in IR

A candle is also not very bright in the visible.

But very bright in the infra red, another not very efficient light source.

Objects in the Near Infra Red

Then we had a look at some objects...

A shaver

A shaver in IR

Plastics that have been coloured with certain pigments become very transparent allowing you to see into this shaver for example.

Bottle of Coke

Coke in IR

Similarly cola is relatively transparent at these wavelengths so you can see right through it. If you look at a light through a glass of cola it looks a very deep red, which tells you it's becoming more transparent at the red end of the spectrum, so we shouldn't be surprised that it transmits infra-red light.

Computer

Computer in IR

Seeing as a laptop screen depends on polarisers to work, which IR ignores, and it is lit by a fluorescent tube it is unsurprising you can't see a picture.

A hand

A Hand in IR

Veins being blue are much more obvious in the IR, it has even been suggested that nurses should use IR cameras to help them find veins to take blood.

A Hedge

A Hedge in IR

If we look outside, most things look similar, but vegetation is much brighter than normal.  Plants can't use IR for photosynthesis so they may as well reflect it to avoid overheating.

A varigated bush

A varigated bush in IR

Looking at this variegated bush you can see that the presence of green chlorophyll has no effect on the colour of the leaves in the IR.

A Fiver

A Fiver in IR

A perfectly normal 5 pound note.

In the IR you can see that the queen is not all there. It has been printed with two different inks which look identical in visible light, but one of which is transparent to IR as another measure to make them harder to forge.

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.

Camera working normally

Our camera

In a webcam the IR is stopped by the filter, and then there are coloured filters in front of each pixel so the camera can determine colour.

If we put a visible light filter on the camera only the IR can get through which goes through all the coloured filters.

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.

A sensor

Light on Photodiode

Most webcams use photodiodes as sensors, these have an area in the centre with no fee electrons to carry current.

If light hits the photodiode it knocks an electron off an atom, which can now move carrying electric current

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.

Dave Ansell

Multimedia

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Comments

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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.

Other possible visible-blocking filters include most transparent-but-dark-coloured plastics, including theatrical "gels", or even Quality Street wrappings (although the optical quality won't be so good).

Colour cameras invariably have IR-cut filters built in (usually the green-cyan coloured chip of glass) as the red/green/blue "colour" filters within the CCD are all IR-transparent so without the IR-cut filter you'd get a colourless black-and-white (infra-red) image.

I didn't know about the banknote ink before though. Cool!
techmind, Wed, 23rd Jan 2008

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.

Again Thanks very much great job.  Cameron Lapworth, Mon, 28th Jan 2008

Monochrome Infra-red film for 35mm cameras is available while stocks last ...

http://en.wikipedia.org/wiki/Infrared_photography RD, Mon, 28th Jan 2008

Old webcam stripped down and ready, now i only have to find the drivers for it!

In the meantime, a quick question. If webcams have the filter fitted, how do software programmes work where you can view the image in 'nightvision / IR' mode'? paul.fr, Tue, 29th Jan 2008

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



My own thinking was that it was simply aesthetic, applying a reddish tinge to the image, i was hoping to be wrong. I will  post/take some pictures when it gets dark.

I can say that it does not give an image like the one you posted above. paul.fr, 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.

What I really need is a webcam that works like my security cameras...that is, it works like a normal camera during the day and then switches infra red when it gets dark.

I have a web cam that runs 24-7 (but has been having problems recently) that shows the garden to the world. During the winter months there is not much daylight.

http://www.gadgetreview.com/2006/01/genius-videocam-trek-310-infrared.html I might try one of these.

I did see some pages where you removed a filter in the webcam...and then the camera became 'infra red'. I have taken a few cameras apart and not found this filter.
turnipsock, Tue, 29th Jan 2008

At long last, I have my infra red camera working...and working well.

http:\\turnipsock.camstreams.com

You can see the dogs bowl and me playing with telescopes on a clear night. During the day, you get a view of the garden...and the dogs bowel. turnipsock, Sun, 24th Feb 2008


It must be an endoscope  .
http://news.bbc.co.uk/1/hi/technology/4145984.stm
RD, Thu, 28th Feb 2008

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.

  As for experiments, I have done all the above. I like dark clothing or dyed hairs that appear white in NIR .. Even with my digital camera and a two layer exposed color film
I can take NIR pictures in full sunlight.

Near infra-red is also called 'actinic' infra-red because it behaves more like light than heat.. Kodak had a nice booklet on infra-red photography ...

You can get infra-red luminescence .... Excitation of some materials with a strong blue light devoided of NIR may produce infra-red luminescence. Powerful Blue diodes do work or .... incandescent lamp (bulb with filament) light filtered by a copper solution (copper wires half way into vinegar- few days)  that absorb the NIR; best test subject is brown-orange Cadmium sulfide from a photo-resistive cell (very strong)..

Marcel
  Marcel dot, Wed, 14th Mar 2012

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!
RE.Craig, Mon, 11th Feb 2013

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