A projector is an output device that can take images generated by a computer or Blu-ray player and reproduce them onto a screen, wall, or other surface. Typically, the surface projected onto is large, flat, and lightly colored. For example, you could use a projector to show a presentation on a large screen so that everyone in the room can see it. Projectors can produce either still (slides) or moving images (videos).
short-throw projector has a ratio of less than 1, down to about 0.4, meaning you could fill a 8-feet screen with the projector as little as 3.5 feet away. Most are in the 0.6 to 0.8 range. Ultra-short-throw projectors have a throw ratio of less than 0.4.
Ultra Short Throw Projection. The Ultra Short Throw projector delivers vivid imagery within an exceptionally short distance of the projection surface. Set it just 5 inches away to get 60 inches of bright, vivid viewing, or go farther to get images up to 100 inches
3D projectors filling screens typically from 92″ diagonal to 130″ diagonal, is a game changer. Like in a theater, you are immersed in 3D, not looking at some small 3D box. 3D projectors are now being used for home theater, for 3D gaming, in education, and for specialty business and scientific applications
interactive Projector's are whiteboard on any surface where the image is projected. This allows the presenter to interact with the projected image using an electric or mechanical stylus and often simply a finger.