An Overhead Projector is one of the most widely used equipment in laboratories and other fields for projecting enlarged images of pictorial or written material onto a screen or wall. It uses a transparency placed horizontally below the projector and lighted from below to cast image on the screen.

Construction of an Overhead Projector
The display system consists of a large box containing a very bright bulb and a fan to cool it, A large lens is placed on top collimating the light. A long arm mirror is placed on top of the box for redirecting the light forward.

Working Procedure
Transparent acetate sheets or transparencies are kept on top of the lens for display. The light from the bulb travels through the transparency sheet onto the mirror where shines forward onto a screen for display. The mirror is used for enabling both the presenter and the audience to see the image simultaneously.

Overhead projectors have an edge over multimedia projectors in terms of cost. These projectors are are available in a number of models can range from simple models to very stylish and technologically advanced used in corporate. These equipment are portable and convenient to use. Various models are available having either single lamp or twin lamps

Use of an Overhead Projector
The display device is extensively used in:

• School
• College
• Corporate Presentations
• Physics Laboratory