Questions About FLIR Temp Inversion Model and OD/2 Assumption

[juanvon]

1.May I ask if your paper has been published? I am currently working on thermal calibration and have encountered some difficulties. I would like to study FLIR’s temperature inversion process, and I believe your paper would be very helpful for my work.

2. In raw2temp.R, line 72 says the thermal window is assumed to be at the mid-point (OD/2) between the object and the camera. Why is that assumption made?

When using an IR camera, the object distance is usually much larger than the lens-to-sensor distance, so I thought using the full object distance OD would make more sense.

Is there a specific reason for using OD/2 for the atmospheric transmission calculation?

Reference:https://flir.custhelp.com/app/answers/detail/a_id/3321/~/flir-cameras---temperature-measurement-formula
The atmospheric parameters and the distance used for attenuation in that link seem different from those in your formulas. I’ve seen many Python implementations derived from your R version, so I traced it back to you and wanted to ask for clarification.

[juanvon]

[gtatters]

Sadly, I haven't written this up as a paper yet. too many other things on my plate.

The assumption of OD/2 above is practical. None of the flir software allows for you to indicate where the window is with respect to the object, and for my own applications I was keeping the window ~ half way between camera and object.

Yes, for many electrical/high temperature applications, I expect that the window is much closer to the camera. From the link you sent where FLIR provided some information, they simply assume that tau is similar on either side of the window, but the equation to estimate tau includes distance, so it is not clear that the flir link is providing full details anyway.

But if you want, you could check Minkina and Dudzik's book to see if I simply derived the OD/2 from there.