Using your mobile phone, you can see infrared radiation – a normally invisible part of the electromagnetic spectrum. Ken’s Tech Tips looks at some of the physics of electromagnetic waves and explains how you can see this invisible world – and you don’t need anything more than the mobile phone in your pocket.

What is infrared radiation?

Infrared is a form of electromagnetic radiation. Other forms of electromagnetic  radiation (EM radiation) include visible light, x-rays, microwaves (the EM waves that wi-fi networks use and also the waves that cook your food in microwave ovens) and radio waves. The difference between all these different forms of radiation are the wavelength of the EM wave. We can illustrate this electromagnetic spectrum (CC-licensed image from Wikipedia):

What is the difference between visible light and infrared?

Visible light and infrared are both forms of electromagnetic radiation but with different wavelengths. Visible light has a wavelength of between 400nm and 700nm (a nanometer is so small that we can fit 100,000,000 in just 1 meter). We can only “see” the EM radiation in this range. At 700nm and longer, we enter the realm of infrared radiation.

Why can mobile phone cameras “see” infrared?

golden waterfall
Creative Commons License photo: paul (dex) busy @ work

Most cameras are designed to capture an image of what people can see. Hence a good camera would only detect EM radiation in the visible light spectrum (between 400nm and 700nm).

Yet the charged couple devices used within cameras are typically manufactured to pick up EM radiation between 350nm and 1000nm. This means they are capable of detecting infrared light too (between 700nm and 1,000nm is infrared).

To improve image quality, camera manufacturers typically add films and filters to block out infrared light and ensure only visible light reaches the CCD. If the infrared radiation was recorded by the camera and appeared in our photos, the photos would not be an accurate representation of what we can see – i.e. what we want to photograph!

Mobile phone cameras tend to be produced a lot cheaper than proper digital cameras and hence the vast majority of mobile phone cameras have a much thinner film/filter to block out infrared light. The lack of infrared filter is one reason photographs taken on mobile phones don’t look as good as those taken on proper digital cameras but it also provides us with an opportunity to use our mobiles to “see” in infrared.

How can I harness this fact?

Simply point your mobile phone camera towards a infrared light source and you can begin to see this new invisible infrared world!

For example, stick your phone camera in front of a television remote control and start pressing some buttons: you’ll see a few flashes of light (your remote uses invisible IR radiation to communicate with your TV – you wouldn’t normally be able to see this radiation as our eyes are not sensitive to the infrared wavelengths used by the remote). If you’ve got a Nintendo Wii, point your phone camera at the sensor bar. You’ll notice the sensor bar emits invisible IR radiation (this is how the Wiimotes track your movement).

Unfortunately, you won’t see the world in true infrared. Your mobile phone camera is sensitive to visible light too – and fortunately (although unfortunately in our case) this always registers much brighter on the CCD and drowns out the infrared image. If you’re really serious about seeing the world in infrared, you can pick up an infrared filter from Amazon. These filters will block out visible light and hence allow you to get a better image of the invisible infrared world.

Your Comments 15 so far

We'd love to hear your thoughts and any questions you may have. So far, we've received 15 comments from readers. You can add your own comment here.

  • Eberhardt Kalmar Huhn said:

    If I use a device such as this, will I be able to use my smart phone camera monitor to see whatever the infrared light illuminates in an environment that is pitch black to the unaided human eye?

    • Hi there,
      This looks like it’s essentially an infrared torch? If you have a smartphone camera that’s able to pick up infrared light, it’s possible this could help you. However, it’s worth double checking how sensitive your phone really is to infrared light (newer smartphones may be less sensitive than early cameraphones from back in 2010) – and I’ve never used an infrared illuminator so not really able to comment very much on this!
      Ken

  • B. Mapatwana said:

    Apart from infrared is there any other invisible (to the naked eye) parts of the colour/visual spectrum that can be found /seen with a digital/phone camera, and how if different from above mentioned techniques?

    • Hi there,
      I believe it’s normally just infrared you’re able to see on some phone cameras. If you’d like a bit more information, you can search Google for “camera sensor response curve” – this shows the amount of light captured by sensors at different wavelengths.
      Ken

  • Miriam Akinyi said:

    Hi, i like the article but would wish to ask some questions
    there is an agricultural test that i want to do but do not want to use a portable spectrometer. i intend to use a phone camera but the test requires a wavelength of between 1500 and 2600nm.

    Are there phones that have incoporated spectrometer to boost the wavelength?
    how can i up the wavelength of my phone camera?

    • Hi Miriam,
      As far as I’m aware, smartphones-based cameras are unable to pick up this range of frequencies. It’s likely you’ll need some specialist equipment for this, particularly if you’d like to get accurate spectrometer results.
      Sorry!
      Ken

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