Demystifying Projectors (Three- part series)

Posted on Posted in Home Theater, Visuals

A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Typically, projectors create an image by shining a light through a small transparent lens, but some newer types of projectors can project the image directly, by using lasers.
There are four types of projectors in use; DLP Projectors, LCD projectors, LED projectors, LASER Projectors.

We will cover each one of them in a 3 part series about projectors, starting with DLP Projectors in this post.

Digital Light Processing is a proprietary system developed by Texas Instruments, they have a single chip instead of glass panels through which light is passed, and this chip has a reflective surface composed of thousands of tiny mirrors which correspond to individual pixels. These mirrors can move back and forth when light is beamed onto the chip to direct the light from individual pixels either towards the projector lens or away from it. In order to define colours, DLP projectors have a colour wheel that consists of red, green and blue filters. This wheel spins between the light source and the DLP chip and alternates the colour of the light hitting the chip between red, green and blue. The mirrors tilt away from or into the lens path depending on how much of each color is required for each pixel at any given moment.

Advantages of DLP include

  • Portability: DLP projectors tend to be smaller and easier to transport since they have one chip compared to the LCD’s 3 panels.
  • Higher Contrast: The deep blacks achievable with DLP projectors make them very popular for home cinema applications.
  • Reduced Pixilation: This is especially noticeable in comparisons of lower-end LCD and DLPs, and makes DLP a popular choice for smooth video applications.
  • Reliability: DLPs tend to fail less often due to fewer parts and are less expensive to repair. DLP projectors have sealed optics, making them ideal for use in dusty environments.

DisAdvantages of DLP include

  • The Rainbow effect: When looking away from the projected image of a DLP `projector to an off-screen object, or when looking quickly from one side of the screen to the other, you may experience a “rainbow” effect – a momentary flash of rainbow-coloured stripes around brighter objects. This is typically only a problem in older DLP projectors without modern, faster 6-colour wheels.
  • Light leakage: Some people may also experience “light leakage” from their DLP projector in the form of a grey band around the outside of the image. This is caused by stray light reflecting off the edges of the mirrors on the DLP chip. This can be avoided by installing black borders around the screen. Again, light leakage is generally only a problem in older DLP projectors.

The next posts will cover LCD, Laser, and LED Projectors. Also, follow us on Thasmai’s FB Page for more cool stuff!