Rear projector and rear projecting method

The invention relates to a projecting device and projection method. Providing at least one projection screen, at least two a two-way connection; each three-throw connection with a field view at least one viewing direction, and projects of the view the projection screen the rear end, farther comprising at least between the transparent state and expanding status and switch is connected to the switch, each transparent state three-throw connecting with different field view, the three-throw in a condition connection with a field view.