A projector or image projector is an optical device that projects an image onto a surface, commonly a projection screen.
More scientifically it can be stated as,
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).
Today, most projectors use either an HDMI
cable or VGA
cable from a computer as their input
To make a home made projector we require some materials. But a simple home made projector will not take input from computer or any electronic devices. It only projects simple images drawn by us. For a high tech projector seen in classrooms require more parts which is not that much easy to be made in home.
For more details of home made projector, go to the below given link.