Projectors receive data from a computer or video source and
project this data onto a screen via internal light sources,
power sources and converters. Projectors include electronic
devices that display video and computer-based images or
presentations and transparency devices that use a light source
and lens to project an image from a transparent film medium.
Projectors are commonly used in classrooms and conference rooms
for presentations. A slide projector is an opto-electronic
projector that uses a light source – usually a fan-cooled light
bulb, a reflector, a slide holder, a focusing lens, and a
condensing lens. Light from the bulb passes through the
transparent slide and focusing lens and the image is projected
on a screen or wall. The most common slide projector is a
carousel projector that uses a stepper motor to advance the
carousel and load the slide into the holder in succession. An
overhead projector is also a transparency projector that uses a
bright light source and lens to collimate the light. Ove