Polarization of two Kinects for interference

In this post, I will describe a more completed experiment on 'how different filtering directions of the polarization filters affect the interference'.
For each polarization filter I defined two orthogonal directions in 2-D space: up and right. The light cannot pass through both directions at the same time. Each Kinect there are two filters in same direction attached to IR emitter and camera respectively. Therefore, there are 16 combinations exist (2 directions for each emitter or camera), and results are shown in following table. The K1-E represents IR emitter of the first Kinect and K2-C represents IR camera of the second Kinect. The results from both Kinects have been recorded for each experiment and coloured based on the level of interference.

	K1-E	K1-C	K2-E	K2-C
1	→	→	→	→
	Bad		Moderate
2	→	→	→	↑
	Bad		Moderate
3	→	→	↑	→
	Very Bad		Good
4	→	→	↑	↑
	Very Bad		Good
5	→	↑	→	→
	Bad		Moderate
6	→	↑	→	↑
	Bad		Moderate
7	→	↑	↑	→
	Very Bad		Good
8	→	↑	↑	↑
	Very Bad		Good
9	↑	→	→	→
	Good		Bad
10	↑	→	→	↑
	Good		Bad
11	↑	→	↑	→
	Moderate		Moderate
12	↑	→	↑	↑
	Moderate		Moderate
13	↑	↑	→	→
	Good		Bad
14	↑	↑	→	↑
	Good		Bad
15	↑	↑	↑	→
	Moderate		Moderate
16	↑	↑	↑	↑
	Moderate		Moderate

Here is a figure briefly shows how different interference levels are classified into Good, Moderate and Bad.

Figure 1 Upper: good; Middle: moderate; Lower: Bad

From the table we see that there isn't existed a case in which both Kinects can achieve good interference results. More importantly, good result only happens when up direction filter is attached to the Kinect and right direction filter is attached to the opposite one.

Hence, we can infer that the good result doesn't caused by the filters on same Kinect but the IR light from opposite Kinect is blocked by the filters in orthogonal direction (in this case right). Refer to some discussions online (link), the light produced by the emitter of Kinect has already been polarized (in my case more up direction).

Then I put one Kinect 90 degrees from another and add the filters as well. So one Kinect produced horizontally polarized light and another Kinect produced vertically polarized light. However, there isn't noticeable improvement from both Kinect sensors. It is possibly caused by the fact that the polarization would be ruined once the light reflects off arbitrary surfaces.