The optical laboratory of Beijing University of Posts and Telecommunications has invented a kind of auxiliary device such as bid farewell to 3D glasses and helmets. It can directly use the naked eye to watch 3D objects suspended in the air. That is, you can directly view 3D movies. The traditional display screens are flat, and the 3D stereoscopic display effect of the 3D movie in the cinema needs to rely on stereoscopic glasses. The naked-eye 3D display solves the problem that there is no need for other auxiliary devices, such as 3D glasses, helmets, etc., as well as three-dimensional display effects. However, these conventional image displays cannot project images into space.