LCD Projector

By: Britney Cattan

History of projector

  • The idea of projecting an image on a surface is a drawing by Johannes de Fontana from 1420. The drawing was of a nun holding something that might be a lantern. The lantern had a small translucent window that contained an image of a devil holding a lance. Leonardo da Vinci also made a similar sketch in 1515. These drawings are likely to have inspired the creation of the earliest image projector, a device called a magic lantern.
  • In the 17th century, the first magic lantern was developed. With pinhole cameras and camera obscura it was only possible to project an image of actual scene, such as an image of the sun, on a surface. The magic lantern on the other hand could project a painted image on a surface. There has been some debate about who the original inventor of the magic lantern is, but the most widely accepted theory is that Christiaan Huygens developed the original device in the late 1650s

How does it work?

  • There are two basic kinds of projection. If the light is behind you and the screen is in front of you, you make an image through front projection. Shadows of people dancing around on their blinds as they walk around inside brightly hit homes, the light source and the object being projected are behind the screen (the blinds) and you're looking from the opposite direction in what's known as back projection.
  • In an LCD projector, a very bright light shines through a small LCD screen into a lens, which throws a hugely magnified image of the screen onto the wall.
Big image

How it works?

  • The light source is placed at the centre of curvature of a converging or concave mirror.
  • A concave mirror is used to reflect light back in fairly parallel rays.
  • The condenser is made up of 2 converging lenses that refract the light so all parts of the slide are illuminated with parallel rays of light.
  • The projection or converging lens provides a real, larger and inverted image. It must be real to be projected on a screen
  • The slide (object) must be placed between F and 2F in order to produce a real, larger, and inverted image.
  • Because the image is inverted, the slide must be placed upside down and laterally inverted so we can see the image properly.

Enhanced Our Life

  • The LCD has enhanced our daily life by bringing movie watching to the next level. In the past, we had drive-in movie theatres, without the projector they would not be able to have such a large image projector on a screen. Moving further into the future we have the movie theatre which uses a front projection.
  • We do use back projection in our television, phones, computers, etc.
  • Portable projector has made family life fun and exciting, you can bring your projector anywhere and have your own in home movie theatre


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