# How do modern microbolometer cameras measure absolute temperature of an object?

I recently started working with thermal cameras and I was surprised to learn that they don't give you the temperature value of the object you are looking at for each pixel. So I did some reading. I read all the topics on it I could find here. Then some papers I found online. I talked to FLIR. Then I started looking into how they work. Now I think I understand that the microbolometer gives you a value for the temperature of each element of its pixel array. In other words, how much the object it is looking at has heated up each pixel. That's why you can see relative temperature easily.

But then I don't fully understand how you go from that to taking accurate temperature measurements of the object you are looking at. I'm guessing it has to do with understanding the emissivity of the object you are looking at, the temperature of the room, and temperature of the sensor. And then some sort of calibration procedure involving sources (blackbodies?) at known temperatures. I did read through a paper on calibrating, but I left with about the same understanding as when I started.

Anyway I'm really curious how some systems claim to be able to read the temperature of objects using a thermal camera with less than 1C of accuracy. I thought the answer was a camera with a radiometric function, but the expensive ones I look at only measure in one spot! And with +/- 20C of accuracy which isn't much help.

• "some systems claim..." - Can you post an example of a system that claims this, so we can maybe figure out what the difference is? Commented Mar 5, 2020 at 14:12
• @probably_someone oh sure sorry. I was thinking of two things. One I have seen that FLIR cameras like the A20M have "sensitivity" to temperature variations as low as 0.12C. Then I was thinking about this virus/fever scanning system someone showed me. thermoteknix.com/products/oem-thermal-imaging/… Commented Mar 5, 2020 at 14:26
• They don't publicly list their temperature range, but it is supposed to be tight enough to discriminate a few degrees for someone with or without fever. (If it really works that is :) ) Commented Mar 5, 2020 at 14:27
• Or even like this FLIR handheld camera. It's measuring temperature all over it's image area. docplayer.net/… Commented Mar 5, 2020 at 14:30
• This one claims accuracy of 0.1C and full radiometric data. infraredcameras.com/wp-content/uploads/datasheets/… Commented Mar 5, 2020 at 15:17