Like many technology niches digital projectors also have competing technologies; Liquid Crystal Display (LCD) and Digital Light Projection (DLP). Both technologies have their own strengths and weaknesses which better suit differing consumer circumstances.

LCD Projectors

LCD projectors use the transmissive light projection method. Early projectors had a single panel but, three panels are now standard. The light source is split into red, green and blue light beams which travel to their respective panels. The hundreds of thousands of small pixels in the LCD panels block varying amounts of the primary colored light (like light valves). Light leaving each of the primary color panels is then recombined by a prism and passes through a lens and on to the projection screen.

DLP Projectors

With DLP, a proprietary Texas Instruments technology, pixels are represented by one of the many thousands of micro-electromechanical mirrors on an optical semiconductor chip (Digital Micro-mirror Device – DMD) surface. The mirrors modulate to either direct light through the lens or away from it. Expensive DLP projectors can have three DMD chips one for each of red, green and blue (sometimes white also) light beams.

In less expensive DLP projectors color is produced by a rotating color wheel placed between the light source and the DMD mirror chip. The chip mirrors modulate to provide the correct proportion of each color for the composite color required. For example, by tilting a mirror toward the light source only when red or blue light is falling on it, the DMD chip can produce the color purple. The viewer’s brain is relied upon to combine the sequential flashes of red and blue to produce purple. Various color wheel designs are used including ones with more color segments and some with additional colors.

Performance Differences

LCD and DLP projectors are both imperfect with differing strengths and weaknesses. Consumers need to match their specific requirements with these known strengths and weaknesses to obtain the best projector selection possible.

LCD Strengths

• Better color saturation (more vibrant colors).
• Slightly sharper images at any resolution.
• More light efficient producing significantly higher ANSI lumen output for the same wattage as DLP.

LCD Weaknesses

• Visable pixelation (ability to see individual pixels on screen)
• Screendoor effect due to interpixel spaces.
• Lesser contrast and black levels capability

DLP Strengths

• Smaller size (chips vs panels in an LCD)
• Better contrast and black levels

DLP Weaknesses

• Rainbow effect (colors separating out to produce color artifacts due to color wheel sequential color updating viewer dependent – not a problem with three chip DLP projectors)

Closing the LCD and DLP Performance Gaps

While there are differing strengths and weaknesses between LCD and DLP technologies, competitive pressures have been steadily reducing them. So one needs to assess the features of the current LCD and DLP projector models in regard to your particular requirements. Some recent developments which are closing the gap are:

• DLP projectors greatly reduced the incidence of color separation artifacts through increasing the refresh rate through faster spinning color wheels and/or more color segments on the color wheel
• Color saturation of DLP projectors has improved through dropping the white segments in the color wheels used by earlier projectors to boost light output.
• The inter-pixel gaps on LCD panels have been reduced and physical resolution–the number of pixels on the screen–has been increased.
• The addition of dynamic aperture control is has boosted contrast on LCD projectors.