Interference problem of multiple Kinects (2)

For the time multiplexing method, currently there is not software feasible way to do it. The Kinect SDK doesn't allow to toggle the laser but can only turn off the laser without knowing the speed. Several hardware methods has been implemented using shutter and revolving disk. The hardware time multiplexing implementations are complicated for this project, as micro-controller are needed for motor synchronisation.

For the polarization method, which polarise the light by putting a filter in IR emitter camera, there is a discussion on the issue available here. In the discussion, someone points out that: the polarization isn't well preserved when reflected on arbitrary surfaces. Furthermore, the luminance of IR light is reduced for better separation which results in a decreased SNR (signal to noise ratio).

Based on the hardware information of Kinect (link), infrared laser diode of Kinect is working at 830nm (I guess not perfect but centred at ~1.2 MHz). Therefore, if we want to use frequency multiplexing method, we may need to physically change laser diode (working at other frequency) of Kinect, and put matching filters in front of the IR camera. It is an expensive and invasive way which requires a complete disassembly of every single device.

A comprehensive ppt about MS Kinect is available here, in which it is pointed out that the interference is minimal with two Kinects. I did some experiments and found out that if shared area shown as holes in one Kinect, it is possibly visible in the other Kinect.

Figure 1 Depth frame captured by two Kinects faced to same area (upper row) with interference and (lower row) without interference.

Figure 2 Depth frame of box captured from two view points by Kinect shows that  the holes  are complementary in another frame (indicated by red rectangles)

Overall, I suggest to use more noninvasive method such as introduce vibration to Kinect or skip the interference problem at this time and come back later if the reconstruction results is not satisfied.