Another smartphone thermal imager from i3

[CatalinaWOW]

This may be a real optical effect and reflects the energy that is reaching the focal plane by reflection off the side walls of the housing, scattering from dust and surface imperfections on the lens and other similar sources.  It is not being focused so an image is not formed, just a large blurry region of different intensity.  You can map these effects by looking at a cold uniform background and moving an intense point source to different angles from the lens centerline but at a constant distance from the lens.  A hot soldering iron pointing directly at the camera is probably good enough for the purpose.

High end cameras put a lot of thought and effort into optics and baffle design to minimize these effects.  You might be able to make some improvements with external baffles (like the sun shield sold for visible cameras), lens cleaning and judicious application of non-reflective paint.

[Conure]

Could someone explain how calibration works on TE cameras (or in general)? My experience is that everytime I start up the app I need to calibrate against a flat surface to minimize the noise. Usually the noise is constantly being updated but after a few minutes the noise starts to look static and I have to calibrate again. I notice that calibration highly affects the temperature numbers shown as well.

This is in contrast to my seek compact which does calibration automatically once every 5 seconds or so with it's internal shutter thing.

I have had times where my TE-Q1 gets 1 or 2 weird spots in the image that goes away after calibration but slowly creeps back.

[joe-c]

Could someone explain how calibration works on TE cameras (or in general)? My experience is that everytime I start up the app I need to calibrate against a flat surface to minimize the noise. Usually the noise is constantly being updated but after a few minutes the noise starts to look static and I have to calibrate again. I notice that calibration highly affects the temperature numbers shown as well.

The NUC was stored in Ram and need therfore to be refreshed each time.

I have had times where my TE-Q1 gets 1 or 2 weird spots in the image that goes away after calibration but slowly creeps back.

maybe this are defect pixels, see attachment.
hope it helps,
best wishes

[bugi]

The bad pixel data is saved to a file, so that data usually does not need to be refreshed after first run, though it will be checked every time the offset calibration is done, too. (Add compile-decompile-understanding -issues caveats here, but it seems the SDK has small bug on that user bad pixel update, which might make it stop working on a session after a number of runs of calibration). Unlike the manual states, there is no need keep pressing anything for long time.. short tap is enough, it'll do it, at least did for me.

Note also that if one has multiple cameras, the same saved bad pixel file will be used, so deleting it when switching camera could be useful.

The calibration stored in the camera flash is made at certain target temperatures at certain time of operation and at certain ambient temperature(s). Since the camera's pixel performance varies over time, even if the calibration time situation could reproduced, the shown view would not be exactly as good.

The offset-part of the user calibration is indeed not saved to a file, so start of the app (and possibly detach/attach of the camera) is enough to reset the user calibration.

The SDK does user calibration by averaging 7 frames for offset compensation, and uses one more frame for bad pixel scan.

The software (SDK/app) tries to compensate for initial warmup and sensor's temperature changes, and something about ambient, too, but those compensations are estimates.

Thus, for best results, it is best to just start the app, let the camera warm up (say, 10-15 minutes, if not more, the old reverse engineering thread has some nice info on how the values change over time), then do the user calibration. By that time the drifts and weird spots should have mostly stabilized.


In my unit, after a short while, there is quite wide darker vertical stripe on the left, but not perfectly limited to specific columns. The user calibration gets rid off it, though in the early minutes it slightly creeps back, less so later (with warmed camera).


That the calibration would affect the temperature numbers, too, I don't know about. I haven't yet deciphered the user offset calibration effects fully (or tested in practice).

[nikoum]

The User Dead Update manual says to press the calibration button for 8 seconds and then a message pops up saying " Dead Update Please close the lens with the lens cup and press the start button "
It also says that the file is saved on the phone memory as i3cam/dead.txt
Well in my TE Q1 plus camera it does not work this way. No matter if I touch the calibration button for 8 seconds or just touch it once, the following message comes up :
" Image Calibration Please close the lens with the lens cup and press the start button "
And the file is saved on the phone memory as i3cam/dead.bin (not txt). It can be that the manual is old and they have changed the process in the newer apps.
The thing that matters is that every time I connect the camera I have to do calibration because the image is full of dark vertical lines and lot of noise that disappear after the calibration (see attachments with lens cup on). After some use the noise appears to come back to a lesser degree and needs to be calibrated again. So for me it has to be calibrated right after connection to the phone and, depending on the usage time, about every 8-10 minutes. Another thing is that regardless of the calibration, if you use the min/max, point or alarm features,  the temperatures detected in the first 5-8 minutes are off by 2.5-3.5 degrees in the range of 25-35  C, so you cannot depend on them. I have compared the camera readings of a human face (usually 35.5-36.5 C) to those of an expensive ir thermometer and verified those differences. Only after 10 minutes of usage, temperatures get closer to reality but they still deviate by 0.5 - 1.5 C.
Can others verify the above ?

[Kilrah]

That is standard for pretty much every thermal camera. The calibration you're doing with a short press is an FFC, which equalizes the whole image with a known uniform source. It needs to be done regularly especially after power up, until the camera's operating temp is reached.
Some cameras include a mechanical shutter they can close/open automatically to perform a regular FFC, and some also warn you that the temp readings aren't valid until the camera is warm. These features aren't present there, but the tech is the same and thus it works the same, up to you to deal with it.