A slide projector uses a light source to shine light through a photographic slide and focus the image through lenses to project it onto a wall or screen. It uses the same principle as a movie projector, but with the still images of slides. With a small light source like a flashlight and the right focusing lenses, you can build your own homemade slide projector.
Instructions
1. Take a flashlight and remove the lens in front of the light bulb. Tie the flashlight to a wood plank or other small, portable surface. Make sure the flashlight is parallel to the surface, so the beam doesn't shine at an angle when laid flat. You may need to make small wood support posts with a saw or knife and glue them on the plank for the flashlight to balance on.
2. Attach a concave lens (one that curves inward and is thinner in the middle than the edges) to the other end of the surface and a convex lens between the first lens and the flashlight. They must be placed so the flashlight beam shines through both lenses. Telescopes and binoculars use concave lenses, while magnifying glasses use convex. Don't permanently attach the lens posts to the surface yet, as you'll need to adjust their positions.
3. Construct one more post for the projector's surface. This one needs a groove chipped or dug into the top where a slide can fit into it. This post also should not be permanently affixed yet.
4. Place a photographic slide into the appropriate post. Make sure it can easily be slid side-to-side through the groove. Turn on the flashlight and make sure the beam shines through the slide and both lenses and projects the image onto a wall. Adjust the focus of the light beam with the lenses and position of the slide until you find the best spots to project a clear, sharp image.
5. Secure all small posts to the wood surface with wood glue. Make sure you know how far your projector was from the wall when projecting the image. This is the approximate distance at which the projector should be set whenever you use it (though it may have to be adjusted for certain slides).
6. Take a set of slides you will view together and tape them side by side into a string or loop. Fit one slide into the slide-holder groove on the projector and turn on the flashlight bulb (with the room lights off) to view the slide. You should be able to move each slide sideways through the groove so the next one fits in place for viewing.
Tags: slide into, beam shines, beam shines through, both lenses, light source
