how do thermal cameras even work
In: Technology
You know how hot things glow?
This is called blackbody radiation, it’s essentially something of a given temperature giving out “light”. This still happens with cooler things, they still give out a form of “light”, just one that we can’t see.
Infrared cameras can see this though, and the more advanced ones can see the wavelength of the light and know the temperature from that.
Edit – this is separate from IR emitters and the associated footage. There it’s all a light source just outside visible range being used to illuminate something. This is then monochromatic as a single “colour” (spectrum/wavelength) was being used.
This gives much sharper images than the blackbody IR as it’s a shorter wavelength and closer to visible light.
Heat is light. A thermal camera has a photo-receptor tuned to those wavelengths instead of red, green, blue…
Once the light is captured, we just translate it into colors we can see before we display it on a screen.
Heat is basically the same as light or any other electromagnetic radiation. Light is just in another frequency range. Thermal cameras have sensors (pretty similar to those in a normal digital camera) which pick up those frequencies and translate them into a picture humans can see.
Everything hot emits radiation, infrared radiation which is a form of light that is invisible to us, but it is still light.
Thermal cameras can see this light though, they have lenses that focus that light onto an array of sensors, these lenses are often made from something like germanium. They focus the IR light onto an array of sensors called “microbolometers”, these sensors are made from materials that are very sensitive to heat, often made from elements like vanadium oxide, when they react to heat they convert it to an electrical signal that can be converted to an image by a computer, each reaction from one of those sensors is treated as a pixel and converted to an image by a computer.
In summary, thermal cameras focus IR light onto sensors that send electrical signals to a computer that converts that to an image.
Everything is electromagnetic wave. From radio waves to microwaves to infrared radiation to visible light to ultraviolet radiation to X-rays to Gamma rays. Radars, WiFi, cellphone signals, TV signals, lasers and so forth.
All those things receive, broadcast or are sensitive to particular frequency of that wave.
Sensors in thermal cameras are simply sensitive to infrared radiation (portion of EM wave). They’re basically like any other device, just tuned to react to this particular frequency (and turn it into electric signals which lights up pixels on the screen). While sensor in your smartphone (photo camera) reacts to visible light and antenna in phone reacts to electromagnetic signals between 700 MHz and 2.6GHz, commonly known as 4G and 2.4GHz and 5GHz which we use for WiFi internet.
Radio is radio is radio. It’s just what you’re trying to catch and how you can use it.
For example, our eyes are just like digital photo cameras, optic cells in eyes generate electric signals when hit with frequencies of visible light of an electromagnetic wave and send those signals via nerves into our brains. If they were tuned just a bit different to accept frequencies of infrared, we could have thermal vision (pretty sure that’ll be a matter of surgery or robotic implants in the future). Some animals (some beetles, bats and snakes) can actually see thermals.
On the level of the device, a thermal camera is just a camera, like any other, just optimised for a wider range infrared light rather than primarily visible. But the basic principle is the same, you have a sensor that detects light and makes an image. Many regular camera sensors actually need infrared filters to block out infrared loght, that’s how similar they are.
Now, why that makes it a “thermal” camera. EVERYTHING made of atoms emits light. We don’t normally notice that because the frequency of that light (or more specifically, the range of frequencies, not just one) is related to its temperature, hence “thermal radiation”, which for our everyday temperatures is some shade of infrared. But that’s also why really hot things visibly glow.
And importantly, that relationship between temperature and frequencies of light is really well established, to the point where we can just plainly tell the temperature of something by the thermal radiation it emits.
Note, this is in contrast to non-thermal radiation, light emitted by some other mechanism, for example an LED, coloured fireworks or fluorescent paint. So you can confuse a thermal camera by pointing it at a bunch of LEDS.
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