The Shirai Lab at the Kanagawa Institute of Technology have developed a way to simultaneously display 2D and 3D video on the same screen without producing a blurry double image. The technology is called 2x3D or Scritter. It uses two projectors to beam the videos and graphics processors that cancel out one of the videos being displayed, so that the 2D video can clearly be seen with the naked eye. The 3D video will become visible once the viewer wears a polarized filter on his right eye.
Kanagawa Institute of Technology Associate Professor Akihiki Shirai noted that their technology also has many other practical applications beyond displaying 2D and 3D video at once. 2x3D can be used to display text in different languages or show different layers of an object, e.g. superimposing the different systems of the body. The drawback to 2x3D is that it results in videos with relatively low contrast, but Shirai also said that that may be countered by using more projectors.
You can learn more about 2x3D on Shirai Lab’s website.