I'm wondering what the difference is between a thermal imaging sensor array such as these: https://www.melexis.com/en/product/MLX90640/Far-Infrared-Thermal-Sensor-Array and an infrared camera such as the Raspberry Pi NoIR.

Of course the sensor array actually outputs temperature values for the pixels whereas with the camera I would have to do imaging math. I want to do non-contact temperature measurement of a sleeping person. Thanks.

 

Infrared cameras like the NoIR respond to what is called near-infrared, just beyond the visible spectrum past the red end. They do not respond at all to the much longer (like 10X longer) wavelengths associated with thermal imaging. Using imaging math with the NoIR camera isn't going to change that.

 

What the NoIR is is just a normal camera sans the IR blocking filter, so it can see things like IR remotes and stuff. As Obiwan0549 said, the wavelength of thermal radiation in the normal range of temperature is too far away from what that camera can sense.

 

And now that I think of it, even if the camera were sensitive in the heat infra red, it would not be able to distinguish between hotter and colder pixels, and definitely not do anything that could correlate to their temperature. The RGB cells are simply not capable of doing that.