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Strange white spot on IR frames when reflective objects in field of view RRS feed

  • Question

  • Hi,

    Playing around with my Kinect v2, I noticed that when I target a reflective object (white board, metallic surfaces, etc), I get a big white circle in my Infrared Stream.

    At first I though it was simply caused by reflection on these surfaces, but then I noticed that the white spot remains at the same place on the reflective object even if I turn the camera around.

    it is very round and pretty much always at the same place on the camera's field of view, which makes me think more and more that it is not a reflection.

    If I translate the camera, the white spot follows my translation, but when I rotate the camera, the white spot remains at the same place.

    Can someone tell me what this white spot is?

    Thursday, March 5, 2015 5:13 PM

Answers

  • The white spot you are seeing is reflected light from the Kinect's IR emitter, bouncing back directly onto the IR receiver. This spot will always occur on any reflective object that us upright and parallel to the Kinect emitter. The color is white because its intensity maps into the white range of the false-color palette for your on-screen IR display. Rotation does not affect the spot because it corresponds to whatever light is bouncing straight back into the Kinect receiver (regardless of the direction where the light originated).
    Friday, March 6, 2015 4:29 AM

All replies

  • Hard to understand what it looks like without seeing some screenshots.

    Could it be a reflection of the IR illuminators from the sensor in your object?


    Brekel

    Thursday, March 5, 2015 7:26 PM
    Moderator
  • This sounds like the reflection but it can be a little counter-intuitive because the emitter is attached to the camera. We aren't used to thinking about the implications for this when it comes to specular reflections so it can trick you. As far as screenshots I would recommend using imgur and just linking to them. Does the bright spot stay at the same place in the image if you move the sensor left to right when it is perpendicular to the reflective material? If so I would blame the reflection from the emitters. 
    Friday, March 6, 2015 2:44 AM
  • The white spot you are seeing is reflected light from the Kinect's IR emitter, bouncing back directly onto the IR receiver. This spot will always occur on any reflective object that us upright and parallel to the Kinect emitter. The color is white because its intensity maps into the white range of the false-color palette for your on-screen IR display. Rotation does not affect the spot because it corresponds to whatever light is bouncing straight back into the Kinect receiver (regardless of the direction where the light originated).
    Friday, March 6, 2015 4:29 AM