Yeah, Yeah what does this have to do with Nikon.
It relates because Nikon and canon have used this before and might possibly again. Basically a Pellix or Pellicle mirror is kind of like a two way mirror. Instead of having the mirror flip up and down it stays put. Light can reach the sensor AND be directed up into the viewfinder at the same time. So you can have fast auto focus will shooting video. Or very high frames per second because the mirror isn't in the way.
The down side is that the viewfinder is a bit dimmer but perhaps Sony have solved that. Very interesting patent nonetheless.