Kinect Hacking 104: Is the Kinect IR Projector Modulated or Synced?

Some people have been wondering if the IR projector is somehow synced to the camera that does 3D estimation.

Short answer: No.

Long answer
:
The easiest way to visualize a modulated signal is to use an oscilloscope. I got out my trusty Hameg and hooked up a photodiode to it. This photodiode has a peak response at 850nm, plenty close to the IR coming out of the projector on the Kinect.

I connected the photodiode to my ‘scope probe.

As a sanity check, hold it under a CFL bulb. You can clearly see the bulb oscillating on the ‘scope.

Holding the same photodiode in front of the Kinect IR projector gets…. flatline. As far as I could observe, the projector is never modulated — during capture, or when capture is not running but the Kinect is on.

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3 Responses to Kinect Hacking 104: Is the Kinect IR Projector Modulated or Synced?

  1. Marco says:

    Are you sure it’s not modulated? It’s very hard for a 3D-CMOS ToF sensor to make an estimation of the distance without pulses…

  2. admin says:

    Marco, it’s not ToF. The Kinect exploits speckle to produce 3D, not ToF. Check the Primesense patent applications.

  3. admin says:

    And yes, I’m sure it’s unmodulated.

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