We propose a large screen 3D display which enables multiple viewers to see 3D image superimposed on real objects behind the screen. In previous study, large screen 3D displays using multiple projectors are proposed, and multi projection 3D display with seethrough property is also proposed. However, using many projectors makes installation and adjustment difficult. Our new 3D display exploiting time-division multiplexing is composed of single highspeed projector and an active see-through screen which has a seethrough property and a motion mechanism for scanning light beam from the projector. The screen consists of multiple vertically-long half mirrors which swing around vertical axis direction. The half mirrors reflect light beam from the projector diffusely in vertical direction and specularly in horizontal direction. It is possible to display different images for multiple viewpoints by changing projection image corresponding to reflection direction. To confirm the principle of the proposed method, we conducted a computer simulation and confirmed that proposed system displays 3D image which has appropriate parallax.