InfraRed Projector/Emitter always on (won't shut down)

#1

Hello there,

I have been playing with depth sensors for some time now. Not so long ago I received my first Orbbec, the Astra Stereo S U3.

I am having some trouble manipulating it but specifically, I am surprised that whenever I plug it via USB to my Windows machine, the IR projector switches ON automatically and stays on for as long as the device is connected, resulting in a considerable heating when it is plugged for some time. It won’t shut down anytime.

Is this really how it is intended to work?? Or is it a bug or an error from my sample?? Other depth sensors I have like the RealSense cameras only switch on the IR projector on demand.

Hope someone can answer,
Best regards!

#2

Hello nachollorca,

I’m using an Astra stereo S.
The Astra steros S I have also heats up.
If you take a picture of the depth sensor with your smartphone camera, you can see that the IR part is flickering.
The Astra steeo S seems to work that way.

Best regards!

#3

Hi jaewoong!

Thanks for answering! I was expecting that the topic would go unheard as many others in this forum.

Your info is useful but I am still concerned: the infrared projector in my orbbec device is always flickering when it is connected to the computer, not only when I take a depth picture. it doesn’t turn off until I disconnect the camera.

Is that also the case for you, or your infrared emitter only switches on and flickers when you take the depth stream although it is connected to a smartphone/computer?

Thanks again!

#4

This might be intentional, because the stereo dot pattern changes slightly as the laser depth module heats up. However, I don’t know if this affects the depth data for the Stereo S. That depends on whether the dot pattern is used only to add texture to a featureless surface (this is how the RealSense cameras operate), or if the precise positioning of the dots is used for depth calculations.

For the structured light cameras (Astra Mini / Astra Pro / Astra +), the accurate positioning of the dot pattern is very important. There is a temperature-dependent “tilt” to the scans, which changes as the depth camera heats up. So it is advantageous to let it reach a stable temperature (i.e. leave it connected for > 10 minutes) before making measurements that demand a lot of accuracy.

I can’t say if that same thermal (in)stability effect is applicable to the Stereo S. It is probably intended behaviour, because that is how the structured light cameras need to operate.

#5

@nachollorca what SDK are you using? We saw a similar issue using the OpenNI2 SDK where after calling shutdown the IR emitter would stay on. May or may not be related to this issue.

#6

Thanks for the detailed info @AaronG !

And @natel : I did read your post when looking for solutions. The thing is that our IR emitter stays on even when no start has been called. No SDK used, no anything. I plug it into the computter with the USB wire and it automatically switches on. That is what I want to know, if it is normal or unintended behaviour.

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