DIY: Fresnel TV Projector

Written by shoaib khan
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DIY: Fresnel TV Projector
Build an inexpensive projector to enjoy movies and shows on a big projection. (27082008 image by Andrey Efimov from Fotolia.com)

You can build a simple TV projector to watch movies and TV shows on a big projection screen. While a homemade projector may have certain limitations in terms of sharpness, brightness, contrast and overall picture quality, you can build one that is capable of delivering an adequate image quality for home use. Building a simple homemade projector entails placing a magnifying glass (lens) in front of the TV screen, and projecting the magnified image onto a wall. The lens used in this assembly is a Fresnel lens, which eliminates distortion of the projected image. A Fresnel lens is composed of several concentric circles, which makes it flatter than a standard lens. The foremost priority is to design the projector that projects all the light being emitted from the TV screen. If not, the resulting projection will be distorted, dull and colourless.

Skill level:
Moderate

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Things you need

  • Ruler
  • Cardboard or plywood
  • Tape
  • Glue
  • Black matt spray paint
  • Fresnel lens

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Instructions

  1. 1

    Measure the dimensions of your TV. You need to know the length, width and breadth of the TV set, and not just the dimensions of the screen. Use a ruler to measure each side, taking care not to scrape the surface of the screen. Write down the measurements.

  2. 2

    Construct a box frame, without a top or bottom, matching your TV's dimensions. The TV should fit inside the box. Use cardboard or thin plywood to make the sides, and then tape or glue the sides to one another. This is the first of two boxes you need for the projector. Once the box is constructed, slide the TV into it. The rear of the TV will jutting out the back of the box.

  3. 3

    Build a smaller box, one that fits inside the larger box from the front. Use the same method and materials as for the first box. Slide the small box about halfway into the larger box. The small box should fit snugly, but able to slide in and out. This assembly lets you focus the projection size, by moving the small box in and out of the first box. Attach a front panel to the small box, and cut a hole in the centre of it to mount the lens.

  4. 4

    Remove the TV out from the larger box. Stand the two boxes upright and spray the inner walls with matt black paint. This eliminates internal reflections from interfering with the projected display. Once the paint is dry, slide the TV back inside the large box.

  5. 5

    Install the lens in the centre of the front panel of the small box. Push the lens into the circular frame so that it is held firmly. If the lens does not go in all the way, make the hole a little larger. For best picture quality, use a Fresnel lens; using a normal double-convex lens will distort the projection.

  6. 6

    Slide the small box inside the large one. Position the entire assembly so it faces a bare, untextured wall or projection screen. Turn on the TV, and check the projected display.

  7. 7

    Configure the projection. Slide the small box in and out until the display is focused. Move the projector nearer or farther from the screen to adjust the size of the projection.

Tips and warnings

  • Having a high gain projection screen will improve the quality of projection significantly. You may spray the screen area with ordinary metallic silver enamel paint to get maximum image brightness. Spray several light coats over an untextured surface.

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