How to Make a Projector Out of Cardboard and a Magnifying Glass

by Charles Clay

A basic projector works by passing light through a lens, focusing it into a picture which can be projected onto a wall or screen. While most modern projectors create this picture internally, the same effect can be achieved by focusing the picture of any television or computer screen through a magnifying glass lens. The main challenge is to properly position the lens and prevent any light coming between the picture on the screen and the lens. With some care, this may be done using a pair of cardboard boxes and plenty of duct tape.


Line the inside of the boxes with black construction paper or paint the insides of the boxes black. Minimizing sources of reflection inside the boxes will result in a brighter, clearer picture.


Cut a hole in the bottom of the large box just large enough for the small box to fit into using a utility knife. The hole should be cut as near to the center of the large box as possible and the small box should fit snugly inside the hole.


Cut a hole in the bottom of the small box just large enough for the magnifying glass lens to fit into. The hole should be cut as near to the center of the small box as possible and the magnifying glass should fit snugly inside the hole.


Place the large box directly in front of the screen you intend to project. If you are using a double-concave lens, the screen will need to be turned upside down. Use duct tape to fix the box to the front of the screen and seal off any seams through which light may enter the box from outside.


Turn on the screen. Slide the small box in and out to adjust the focus of the projector until you have a clear picture on a flat, smooth surface.


  • check A blank white wall or a smooth sheet make good projection screens. The rougher the surface, the harder it will be to achieve a clear picture. This projector will perform best in a dark room, as ambient light can overwhelm the light coming from the projector.


  • close Make sure your projector does not cover any of the screen's ventilation slits. Blocking these slits can cause the screen to overheat and may cause damage.

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