Can We Utilize an Infrared Camera to Detect a Fever?

Infrared Camera

One of the most helpful things about infrared (IR) cameras is that you can point them at a location and visualize how hot or cold things are. The good thing is, it wouldn’t require any physical contact, and you get an almost instantaneous reading. You might have noticed handheld IR devices called temperature guns being used in some locations. IR devices are also used in factories to monitor the equipment’s temperature without stopping or going near them.

However, there are some challenges with using this technology to screen people for illness. To do it well, you need to understand how infrared sensors work. Besides, the physics are just super exciting.

All Objects emit light, and mostly we can’t see these lights.

In science, you don’t always get what you want. But if you try harder, you get something even better. This is what happened to William Herschel, a scientist who lived in 1800. While testing light filters, Herschel used a prism to split sunlight into various color lights. Then he set up some thermometers to measure the temperature for each color. He already knew that light falling on an object would heat the object, but he wanted to measure the temperature of each color separately.

He noticed something strange. A thermometer kept at the end, beyond the red color (one that wasn’t even in the light), also warmed up. The reason for that was there was light hitting that thermometer that cannot be seen with human eyes. That was the discovery of the infrared light.

There’s more. You can use the wavelength of light emitted by an object to determine its temperature. You’ve seen this when you use an electric kitchen oven. When the heating element gets good and hot, say around 2,000 degrees Fahrenheit, it glows a reddish-orange color. 

When you’ve just turned on the oven, say after a couple of minutes, it might look black to our healthy eyes. But it’s already hot enough to burn you. What if we take a picture with an infrared camera? The infrared camera would show a color image of the heated element. As our eyes can’t detect infrared light, the camera translates, using visible colors to represent different wavelengths in the infrared range.

Measuring Body Temperature

Can we use an infrared camera to see if someone has an elevated body temperature? Well, there is a problem there. The IR camera looks at the outer surface of things called skin temperature. The internal body temperature of a healthy human is around 37 C (98.6 F), but the outside skin temperature is lower than that. If you play around with measurements at different spots on my face, and the highest temperature you could find would be 95.3 F, in the inner corner of my eye. If you check in the Hence IR camera manufacturers recommend focusing on the tear duct. The temperature is still about 3.3 F variance between tear duct temperature and internal temperature. However, it would be a consistent 3.3 F variance.

Need to Remove Your Glasses

If you want to measure the tear duct temperature, then anyone wearing glasses would have to remove them. Why? As it turns out, while the glass is transparent for visible light, it blocks infrared light. Infrared from the eyes will be blocked from reading when using regular glass, not even sunglasses.

Will It Work?

Human bodies have a high emissivity. An excellent infrared camera can distinguish small variances in temperature. The one real challenge is that it only measures the surface temperature of the skin. However, this might be fine if you compare people and look for outliers that are warmer than others.

Hence we could use an IR camera to screen individuals with relatively elevated body temperatures. That doesn’t necessarily mean they have Covid-19. Maybe they have ordinary flu. Maybe they’re hot from exercising. There are many methods you can get false positives and false negatives with the IR camera.

Does that mean it is useless? No, it’s a temperature screen, not a clinical diagnostic test. It is not perfect, but it could be a quick, inexpensive, non-invasive way of surveying large groups. It helps to flag people with a higher probability of being infected for follow-up questioning.

An oral thermometer is much more accurate. However, you can not imagine stopping each person outside a grocery store to stick a thermometer in their mouth and wait for a reading? People just would not like that.


Mobodexter’s BodyTemp is an Elevated Body Temperature (EBT) Measurement Kiosk.

Protecting yourself, your staff, and other visitors and patrons from the spread of contagious diseases begin with identifying, quarantining, and treating infected individuals. BodyTemp’s thermal sensor technology provides an accurate and affordable solution to alert individuals of heightened temperature status while protecting others in and around your facilities. Mobodexter’s BodyTemp can capture analytics that ensures your operational, compliance, and HR requirements (optional client consent). AI enabling of response customization, analytics, networking, and synchronizing of BodyTemp anomaly alerts, as well as compliance logs for legal audit trails, are made available.


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