Temperature legend with the Lepton® longwave infrared (LWIR) imager

[Francis Dominic]

Hi

I am using the Lepton thermal camera (https://www.sparkfun.com/products/13233?_ga=1.86908827.2056822439.1439952903)

with the Raspberry Pi 2 computer.

The requirement of my projects is that I need to know the temperature on the output obtained from the camera

Similar to this http://i.ytimg.com/vi/8Oxky0qyOuw/mqdefault.jpg

What changes in teh code will help me get a similar interface or at least the temperature scale in the side of the window

 

[Justin Lee]

Hi Francis

Obtaining external temperatures from the Lepton is actually not a trivial task.  The Lepton would need to be calibrated.  To do so, you will need to point the Lepton at a uniform black body and calibrate the Lepton to heat sources of known temperatures.  This calibration data and temperature data is then used to create a polynomial function that maps the 14 bit data from the Lepton into a temperature.

Regards,
Justin

[Francis Dominic]

Thanks Justin

I have a image of temperature scale and would like to ask if its possible to insert it onto the GUI?

If yes could you pls provide the codes and where the changes need to be made.

[captainmoron]

Hi Francis,

obtaining Temperature data from the Lepton without calibration is not that easy. There are some approaches in this group to measure a linear funtion by mapping raw values of the Lepton with known temperatures. In this thread https://groups.google.com/forum/#!topic/flir-lepton/GWHD1KMVYaE Mark Ricklick wrote:

"I did a rough calibration of the Lepton, taking images of a piece of copper painted black, and mounted against a heater. 

My first calibration turned out the following linear relationship: y = 0.05872x - 479.22999

Where, Y is the target temperature - the camera temperature. All in Fahrenheit. 

Or Target (F) =  0.05872x - 479.22999 + Camera (F). "

I haven't did not look into it yet, how accurate it is, but for a start the results looked promising. For the temperature scale I would say, you should look into Qt, with which the Lepton demo has been made.

Best Regards,
Peter

[Justin Lee]

Peter, that seems to be a great resource for people who are interested in thermal temperatures.  I may be poking around that thread for some useful information.

I have not tried Mark's calibration, but if it works, it should be a pretty decent approximation of temperatures for starters.  I believe a more effective function would be a polynomial function (rather than linear).  Also, I don't think that calibrations from one Lepton will carry over precisely to another Lepton due to slight deviations in manufacturing and external factors (ex. placing a Lepton closer to a battery would probably skew some data).

[Justin Lee]

Francis, I have not tried it myself.  But I'm sure that if you want to overlay text onto the thermal image, you can find a C library that works with it.  Otherwise, you can probably add some sort of widget.  Currently, raspberrypi_video has a button that allows you to perform an FFC.  If you want to reference that and add a widget like that, you can reference main.cpp in raspberrypi_video and search for the block of code under the comment "create a FFC button".  

Regards,
Justin

[Francis Dominic]

Hi Justin

I tried including the image by including some codes but I need to sharpen them.

[Francis Dominic]

Hi Peter

Thanks so much for this valuable piece of information

I will convert it into codes so that they go well with the GUI 

And also could you pls tell me the operating range of the thermal camera

[robert hyde]

Hi Francis did you manage to create a working code?

[Francis Dominic]

Hi

I tried but then found that its unnecessary

is it possible to run the thermal camera in Arduino UNO as the package comes with its example codes.

[Ankur Parashar Dutta]

pardon my stupidity, but, what does "x" in 0.05872x stand for?

[Max Ritter]

I implemented this for my DIY-Thermocam project (www.diy-thermocam.net):

The full source code is on Github, and you can find the calibration related stuff there: https://github.com/maxritter/DIY-Thermocam/blob/master/Thermal/Calibration.h

I am giving the Lepton some kind of warmup time (60s), because the relationship is only stable afterwards due to self-heating of the sensor. 

[黄昌军]

Hello Max,

How do you draw the color bar?
Is according the minValue and maxValue of each frame and refresh frequently?

Thanks and Regards,
Jakebo