The Differences between LCD and DLP Projector Technology

LCD Projectors vs. DLP Projectors - Which is right for you?

When shopping for a digital projector, your first question might well be:

 “Which type of projector technology is the best, and what is the difference?”

The two main contenders are Liquid Crystal Display (LCD) projectors and Digital Light Processing (DLP) projectors. These terms refer to the mechanism the projector uses internally to compose images. It can be a hard decision as both projection technologies have strengths and weaknesses, and it is important to know the differences so you can choose which technology matches your needs. In this Bamboo AV Advice article we will explain the technology behind LCD and DLP projectors, and then compare them so you are better placed to make a decision on which type of projector to buy.

How does LCD technology work?

LCD projectors project light onto mirrors which split it up into its 3 primary colours: red, green and blue. The colours then pass through three separate glass panels (actually prisms), which is why this technology is referred to as 3LCD. When light is projected through the LCD panels, individual pixels are opened or closed to allow light through or block it. The separate colours are then converged using another prism and projected on to the screen.

How LCD Technology Works

How does DLP technology work?

Digital Light Processing is a proprietary system developed by Texas Instruments, and works differently to LCD projection. Most DLP projectors 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.

How DLP Technology Works

The two technologies are therefore quite different, and so it is not surprising that LCD and DLP projectors differ in terms of their performance and their usefulness for different applications.

What are the advantages of LCD Projectors?

LCD projectors have historically had three main advantages over DLP projectors.

More accurate colours

  • DLP projectors often have a clear section in their colour wheel which boosts brightness but reduces colour saturation. LCD projectors do not have a colour wheel.

Sharper image

  • LCD projectors have a slightly sharper image than DLP projectors at equal resolutions. This can actually be a drawback which we will come to below.

More light-efficient

  • This means that the same wattage lamp in an LCD and DLP would produce a brighter image in the LCD.

The disadvantages of LCD Projectors

The historical disadvantages of LCD are more relevant to video than data applications.

Screen door effect

  • The sharper image produced by LCD projectors can actually be a disadvantage, since the more precise focusing makes the pixilation (“chicken wiring” or “screen door effect”) of an image more obvious.

Contrast

  • LCD contrast may not be as good compared to DLP, meaning that LCDs cannot produce completely black images. Both of the above are less of a problem with newer, higher resolution 3LCD models.

Portability

  • LCD projectors have more parts and so are bulkier and less portable than DLPs.

Image degradation

  • More parts means more parts which can go wrong. LCD panels can experience long term image degradation where colour balance shifts and overall contrast is reduced. LCD panels can be expensive to replace.

Dead pixels

  • Dead pixles can become a problem in LCD projectors, where one or more pixels turn permanently on or off. With one pixel, the effect is hardly noticeable, but it can become an annoyance if this happens in clusters of pixels.

What are the advantages of DLP Projectors?

DLP projectors are a favourite amongst road warriors and home theatre enthusiasts for several reasons:

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.

The disadvantages of DLP Technology

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.

Which technology is right for you?

The various advantages and disadvantages of LCD and DLP projectors mean that each is suited to different applications. Lighter, less bulky DLP projectors are favored by presenters on the road. DLP projectors are also very popular with home theatre enthusiasts due to the higher colour saturation, better contrast and image stability. Entry level DLP home theater projectors are also very affordable.

LCD projectors are often more affordable, making them attractive for education organizations. Their higher light output make them well suited for classrooms and larger conference facilities, as does their increased image sharpness which makes them good for displaying data-rich presentations such as spreadsheets and graphs.

In terms of market share, LCD projection technology is currently leading DLP technology due to the larger number of projectors using the LCD system. Sony and Epson are the largest LCD manufacturers, along with Hitachi and Sanyo. Optoma, InFocus and BenQ, on the other hand, use DLP technology.

The Future of LCD and DLP enhanced technology

Advances in LCD technology have mainly been aimed at reducing the “screen door” problem. These include:

  • Higher resolutions
  • Reductions in the gap between pixels
  • The use of Micro-Lens Array (MLA) to boost the efficiency of light transmission through XGA-resolution LCD panels

The latest major DLP innovation is a projector system with 3 DLP chips instead of the usual one. The three-chip DLP is similar to LCD technology in that the light is split up into red, green and blue by a prism and then each colour has a separate DLP chip off which the light is reflected. Three-chip DLP projectors are widely recognised as having the best looking images of all projector technologies, however they are also by far the most expensive.

We hope that this Bamboo AV advice section on LCD and DLP technology has been useful to you!

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