eli5 How do projectors work?
In: 3
Lenses focus an image on a screen, the image usually is a transparent LCD screen. Some use a color wheel so the different color components are alternated in projection, the LCD keeps in pace with the color wheel as to render the right color.
If you mean a DLP projector, it works like this:
There’s a chip full of microscopically tiny mirrors and a light source aimed at it. The mirrors can turn to reflect a varying amount of of light through the lens. Each mirror represents a pixel. On its own, this technology van only create greyscale images. To achieve color output, the projector alternates between a red, green and blue image for every frame. A color wheel, which is syncronized to the output, is used to color the sub-images accordingly. To the human eye it seems like the projector is displaying one full color image at a time. If you wave your hand in front of the projection, you can actually see the projector alternate between the different colors.
Have you seen a film projector? It works by shining a bright light through the colored film. You need lenses to properly project on the wall from any distance and be in focus (sharp, not blurred).
LCD projectors are basically the same, except the film is replaced by an LCD panel. The LCD is like the film: it blocks and colors the light partially. (LCD TVs are the same, they have a backlight panel behind the LCD, just no “projecting” setup)
DLP projectors are a bit more complicated. They usually have a spinning color wheel with RGB colors, and instead of shining through an LCD panel, the light is directed at a surface that has millions of tiny mirrors. These mirrors can move a bit, so they can direct a light either out through the projector lens, or elsewhere, to block light in that part of the image. You get gray by moving the mirror in a cycle: half cycle on, half off gives you gray.
By cleverly timing the color wheel rotation with the fast moves of the mirrors, you get a full-color image projected on your wall, which is usually brighter than the one shining through a 3-layer (for the 3 base colors) LCD. However, some people can see a kind of “rainbowing” effect because the colors don’t appear at the same time, rather in series after eachother.
There are also solutions to split the light and color it before sending it to 3 different LCD or mirror panels, then combining it again. This removes the need for color wheels.
Laser projectors only differ in the light source.
There are some more interesting technologies in the world of image projection, but these are the basics.
Latest Answers