I believe there is a plate with LEDs on both sides that is rotating. When you look at that plate from the side, it obscures the stuff behind it. That's why you see more "shadow" the closer you get to the center. In this video, you can see the effect:
Around the 10 seconds mark, the camera rotates around the display and then you can see a glowing laptop screen move behind the VX2. And there you can see that the center of the VX2 has something blurry but solid which obscures the background. That's the rotating plate with the LEDs on it, I believe.
https://www.youtube.com/watch?v=2I0sjF9NuTU
Around the 10 seconds mark, the camera rotates around the display and then you can see a glowing laptop screen move behind the VX2. And there you can see that the center of the VX2 has something blurry but solid which obscures the background. That's the rotating plate with the LEDs on it, I believe.