How do Thermal Cameras work?

SURE24 are an Official UK Distributor of the popular range of FLIR Cameras. Thermal Cameras have been in the news a lot in the past year or so, as their increased popularity and more efficient manufacturing methods have allowed costs to reduce significantly. High end police and military cameras are still available, but there is a new generation of affordable cameras such as the FLIR One or the FLIR Scout TK. Thermal imaging can product some useful and interesting imaging, and has applications in almost any industry. If you've ever wanted to know exactly how the technology works, we've put together some information. If you need any more detail, you can call our knowledgeable staff on 01949 836 990

What is infrared?

How FLIR works

In 1800, William Herschel – a British astronomer - conducted a famous experiment measuring the difference in temperature between the colours in the visible spectrum. He used a prism to separate sunlight into the visible spectrum and then put thermometers within each colour. The results showed an increase in temperature from blue to red. Herschel then moved the thermometer just outside the spectrum and noticed an even warmer temperature measurement. Herschel had discovered infrared light. This was the first discovery that there were forms of light not visible to the human eye. This Infrared light can be used in covert cameras, as the light is invisible to the human eye but some cameras have the no IR filter, so they can see this light.

You can see more with this (slightly cheesy) video below.

Infrared radiation is also emitted by heat. In fact, the primary source of infrared radiation is heat.

We experience infrared radiation every day. The heat that we feel from sunlight is infrared and all objects with a temperature above absolute zero emit infrared radiation, and it’s this heat radiation that can be picked up by FLIR Thermal cameras. The below images both shows two cups, one containing ice water and one containing hot water.

FLIR Hot and Cold 1 FLIR Hot and Cold 2

How does Thermal Imaging work?

As we’ve said, all objects emit some kind of radiation as a function of their temperature. FLIR Cameras detect this infrared radiation instead of visible light.

Human eyes are detectors that have evolved to detect only electromagnetic radiation that is in the visible light spectrum. All other forms of electromagnetic radiation, such as infrared, are invisible to the human eye. Infra-red is not visible to the human eye because its wavelength is too long to be detected. But special cameras such as those made by FLIR can detect these wavelengths. To put it another way: FLIR Cameras can see heat. The cameras detect heat radiation and convert that information into a visible image we can see and understand. FLIR can show you this image in a number of ways – black & white, where the white images are warmer, or the reverse of this where hot objects appear black, or you can highlight just the hottest areas with the unique InstAlert feature. This makes it easy to spot suspects in the thermal image.

FLIR Thermal Imaging Cameras

Thermal imaging cameras have lenses, just like visible light cameras. But in this case the lens focuses waves from infrared energy onto an infrared sensor array. Thousands of sensors on the array convert the infrared energy into electrical signals, which are then converted into an image.

The diagram below shows how FLIR Cameras work. Infrared energy (A) coming from an object is focused by the optics (B) onto an infrared detector (C). The detector sends the information to sensor electronics (D) for image processing. The electronics translate the data coming from the detector into an image (E) that can be viewed in the viewfinder or on a standard video monitor or LCD screen.

How FLIR Works

See the FULL Range of FLIR Thermal Cameras here



Posted in FLIR By

Joe Marshall