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Today i come to you to ask you for your help because this is not my domain. I am a computer vision engineer and i want to monitor a WAAM (wire arc additive manufacturing) process using an OPTRIS PI 1M thermal camera.

The problem is when i try to record the welding process(arc is on) i get an image with white stripes/bands on the imageBad quality image . When i turn the arc off this is what i get Good quality image

When i asked the camera's manufacturer he told me that it's due to the recording frequency so i have to play with it until i find the best setup(he didn't suggest wheather the frequency should go up or down). I tried doing that but the image kept on getting worse.

In my humble opinion, I think it's due to the arc's light and i started looking for a filter to block the latter but unfortunately there are very few documents talking about thermal camera filters.

So here i am kindly asking you guys: have you ever encountered this problem ? How did you fix it ? What do you think the problem can be ? Any leads, suggestion, help ?

Thank you very much for your time.

Note: 1- The arc's is on(during welding process), its temperature value is always saturated (max value of 1800°). 2- I can eliminate this problem if i modify the reference bar (color scale of the image) by getting bigger the reference temperature (min temperature) (i make the reference temperature more than 950°C). Here is an image of the reference barReference bar

I tried modifying the recording frequency but it didn't work.

I modified the reference barreference bar and the arc's light almost disappear.

I'm currently looking for a filter to block the arc's light.

I'm open to all suggestions.

Kert
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  • This question is obviously not related to programming, and therefore not suitable for this site. Here is a list of all the sites on the network, I hope you’ll find one where this question would be on topic: https://stackexchange.com/sites#answers – Cris Luengo Jun 20 '23 at 13:26
  • Thank you i didn't know any other website where i could publish my question. – Kert Jun 20 '23 at 14:36

1 Answers1

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I don't think this is just "classical" saturation by overillumination. The stripes that you see come, I guess, from the way, the CMOS chip reads out the data. Somewhat from the bottom to the top in a striped fashion. Then during exposure, the other pixels see too much light. This could explain the repeated gradient.

Also I noticed, that you are on the very top end of the camera's temperature range: 1800°C should be the max according to the manufacturer, so maybe your process is too hot?

What I would try is:

  1. Decrease the aquisition time of the camera further if this is possible
  2. Increase the distance between object and camera (factor 2?), so it sees less light
  3. Using a filter is a good idea, but I would assume that it changes the spectrum and hence you will get a different temperature reading.
R. C.
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  • First of all thank you for your time. The process is indeed too hot (it is a welding process so the saturated point's temperature should be at 3300°) but i don't see how that could be the problem ? . 1- For the aquisition time aka exposure time i don't have the option to modify it on my camera it uses the default exposure time set by the manufacturer. 2- I did try to increase the distance (multiplied the ditance by 2) but the problem persisted. 3- About filters, i don't know much about physical filters so i'm just going to try a IR filter that block all visible light and hope for the best. – Kert Jun 20 '23 at 14:50
  • Welding may also be creating a ton of EMF interference, which could be interfering with your camera. Look at how it is shielded from that, and also probably some IR filters. – Pete Jun 20 '23 at 15:01
  • @Pete do you have any suggestions to handle this problem ? – Kert Jun 22 '23 at 07:51
  • @Kert for the EMF I would do everything I can to reduce that energy from getting to the camera's electronics. Use shielded grounded cables, put the camera in a grounded box or cage if possible, ferrites, etc. I'm not an expert in this area, you'd want to talk to an EE than knows what to do. For the IR filter, you probably want to talk to an optics engineer, but failing that, you could go buy a set of filters and try them. I'm assuming you of course already tried to modify the camera's exposure time and gain settings as well? – Pete Jun 22 '23 at 15:29