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Infrared wavelength

    Question

  • Hi there,

    maybe I missed it somehow: What is the wavelength of the IR flash coming from the new Kinect V2?

    (I need to know because of other devices using IR light as well)

    Cheers

    Wednesday, January 14, 2015 8:09 AM

All replies

  • others have measured this, but we do not have that information. Others have stated it is in the ~827-850nm range. It doesn't just operate at one frequency since there are 3 emitters and the way time of flight works. This is the same sensor as an Xbox One, so typical consumer devices should not interfere with its operation since we do active IR filtering.

    Carmine Sirignano - MSFT

    Wednesday, January 14, 2015 9:06 PM
    Owner
  • thanks, at least some information. Is it a big secret or why is there no official data about the IR range?
    Friday, January 16, 2015 2:06 PM
  • No secret since it can be measured, just not official. That is operational information that you may want but is internal implementation detail not necessary to the operation and use of the SDK. As a Kinect SDK developer that is abstracted away by the driver/runtime to take care of.

    Take some hypothetical future that a firmware update happens and changes the operation of how the sensor operates. If you wrote your Kinect application with our SDK that change would not effect your application.


    Carmine Sirignano - MSFT


    Friday, January 16, 2015 6:20 PM
    Owner
  • I have tested that Kinect V2 might not use the IR in ~827-850nm range. 

    I use a IR light source of 850nm wavelength, Kinect V1 saw a very bright scene, but Kinect V2 saw a very dark scene, especially the centre of the light source is a black hole, and the outer ring of the light kept blinking.

    It seems that the Kinect V2 have a filter which makes the 850nm light blocked. And to my knowledge, there's an shutter in front of the IR sensor which is used for measuring the light travelling time, it keeps opening and closing,  I guess this makes the outer ring of the light blinking, but I'm not sure.

    I want to capture the IR image using an independent IR light source with the Kinect V2 IR emitter blocked. Further more, I want to detect the checkerboard on the IR image  for calibration purpose, I failed to do that with the Kinect V2's IR emitter. Is there a way to do that? Is another IR light source of different wavelength needed? 

    Saturday, March 04, 2017 2:02 PM
  • The IR image you see is not a direct single illumination frame, it is an addmixture of 9 frames (3 triplets from the 3 different frequencies). The Kinect v2 samples at 300 Hz but 10 IR frames are needed to calculate 1 depth image, see this video for some visuals of what I mean. https://www.youtube.com/watch?v=X_Wv-55Ulv8 What is probably happening is that your light source is completely saturating some of the phase encoded raw IR images, so the one that is displayed to you at the end is not reliable. 

    Libfreenect2 has some ways to expose the raw IR frames if you dont mind digging around a bit.

    Saturday, March 04, 2017 4:18 PM
  • Thank you for your help, I learned a lot when digging. 

    I modified the source code of Libfreenect2 to get single phase image, but the single phase image still seems noisy with Kinect V2 's original IR emitter, at least it's not clear enough to detect a checkerboard. By the way, I use iai_kinect2 's calibration procedure to detect chessboard. 

    I also captured the single phase image of the independent 850nm IR light source, it still blinks, the not matched wavelength might be the reason. 

    I have found the wavelength of Kinect V2 is 860nm, this is stated in the paper  

    3D reconstruction using Kinect v2 camera

    but I have not tested it.

    • Edited by leoujz Monday, March 06, 2017 1:15 AM
    Sunday, March 05, 2017 3:01 PM