How Projectors Work

There are two major types of projectors in use as of this writing (things change pretty fast in the field). Projectors come with many features, strengths, or weaknesses, but most will run on either LCD or DLP technology. LCD is the older technology, but this does not mean that it is becoming obsolete by any means.

LCD stands for Liquid Crystal Display. The way this places an image on a screen is fascinating and not nearly as complex as you might imagine. A bulb is set up to shine a fairly powerful light through a prism. The prism splits the light into its component colors and these are sent through small LCD screens. The screens themselves are sent signals to allow just so much of the light through at specific pixel locations. The light is then beamed through a lens onto a screen where the images can be seen by the human eye.

Diagram of How LCD Projectors Work

DLP, or Digital Light Processing is a bit more complex. This time the light is shined through a spinning color wheel onto a chip that is mounted with hundreds of thousands of tiny mirrors. The mirrors are turned off or on by electronic impulses according to the need for the color at that moment. Even though only one color is shown at a time, one color follows another so quickly that the primary colors seem to blend into the appropriate color. The image appears to be constantly lit, when in fact small parts of it are constantly flickering. This technology was developed by Texas Instruments and is based on an older technology that was used for color television in the 1950s.

Diagram of How DPL Projectors Work

Knowing the difference between these two types of projectors can be important, as LCD is considered better for static or high-contrast images. DLP, with its more vivid colors, is thought to be better for video. Some DLP projectors, have been known to manifest a rainbow effect. This can happen when white objects move on a dark background. Small shadows of red, blue, or green may be seen. Most modern DLP projectors have overcome this problem with multiple chips and higher rotation rates for the color wheel.

So to what uses can we put these amazing machines?

< Projectors | Projectors: Uses >

Interesting Fact:

LCD is used in most computer screens, tvs and cellphones. It allows viewing on a flat screen.

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