DLP and LCD Projector Technology Explained at Projectors UK

DLP and LCD Technology Explained

Projectors can be broadly catogorised into two technologies, DLP (Digital Light Processing) or LCD (Liquid Crystal Display). This refers to the internal mechanisms that the projector uses to compose the image.

LCD and DLP each have unique advantages over one another, which is why its important to understand what each of the technologies has to offer.

DLP Projector Technology

Digital Light Processing™ is the world's only all-digital display solution. DLP™ technology uses an optical semiconductor, known as the Digital Micromirror Device, or DMD chip to recreate source material.

Advantages of DLP

Less 'chicken wire' (or 'screen door') effect because pixels are much closer together. This doesn't make so much difference with data, but it produces smoother images for video.

A comparrison of an LCD and DLP projection to illustrate the 'screen door' or 'chicken wire effect on LCD projections.

Higher contrast achievable.
DLP projectors are generally more poratable as fewer components are required.
It has been claimed that DLP projectors last longer than LCD projectors please click here to view the article.

Disadvantages of DLP

Less colour saturation (more of a problem with data than video)
The 'rainbow' effect, appearing as a momentary flash of rainbow-like striping typically trailing the bright objects when looking from one side of the screen to the other, or when looking away from the projected image to an offscreen object. Only some people see this effect, or you can create it for yourself by moving your eyes very quickly across the screen. There are two types of DLP projector - the old ones had four segments on the colour wheel, the new ones have six and spin faster, which means less rainbow effect and more saturated colour.
The 'halo' effect (or 'light leakage'). It may bother some people using their projector for home cinema. Basically it's a grey band around the outside of the image, caused by stray light being bounced off the edges of the tiny mirrors on the DLP chip. It can be a distraction, but can be overcome by having a black border a few inches wide around the screen, so the halo falls on to the border. However the halo effect is less evident in the newer DLP chips such as the DDR chip
Generally, DLP is a better technology for home theatre than LCD . Some of the more home theatre-oriented projectors have virtually no halo effect.

LCD Projector Technology

LCD (liquid crystal display) projectors contain three separate LCD glass panels, one for red, green, and blue components of the image signal being transfered to the projector. As the light passes through the LCD panels, individual pixels can be opened to allow light to pass or closed to block the light. This activity modulates the light and produces the image that is projected onto the screen.

Advantages of LCD

LCD is generally more 'light efficient' than DLP (ie. the same wattage lamp in both an LCD and DLP would produce a brighter image through the LCD).

LCD tends to produce more saturated colours. However, the colours being more saturated makes people perceive the projector to be brighter overall, even though the DLP white may be brighter.

Hence, with a data signal, if you put a 1000 lumen LCD next to a 1200 lumen DLP and showed a colour image people would probably prefer the LCD for brightness.

LCD tends to produce a sharper image (ie. more precisely focused). This can actually be a bit of a disadvantage for video, where it makes the pixellation more obvious.

Disadvantages of LCD

Chicken wire effect causing the image to look more pixellated.

Generally more bulky, as there are more internal components.

'Dead Pixels' - Pixels can become permanently on or permanently off, while this is barely noticeable with one dead pixel, if the projector develops multiple dead pixels it can be a irritation.

LCD panels can fail, and are very expensive to replace. DLP chips can also fail but as there are fewer parts in a DLP projector this is relatively rare.

Conclusion

DLP projector technology is generally preferred for home cinema and portablity. LCD projectors are generally better where colour reproduction is critical.