What are Overhead Projectors?
Simply stated, an overhead projector displays images to an audience. Overhead projectors typically consist of a large box containing a very bright light-source, a fan for cooling the box, and a large lens that focuses the light. Above the box, typically on a long and folding arm, is a mirror that redirects the light forward instead of up. Page sized sheets of transparent film are placed on top of the lens for display. The light from the lamp travels though the transparency and into the mirror where it is reflected onto a viewing screen. The mirror allows both the presenter and the audience to see the image at the same time, with the presenter looking down as if writing and the audience viewing the screen. Overhead projectors were once a common fixture in most classrooms and business meetings. Increasingly overhead projectors are being replaced by larger computer monitors or LCD projectors. Critics feel that these newer systems are more expensive, much more prone to failure and have a s
