LCD chip
DLP chip
The last issue of the Inland Broadcaster included an article discussing LCD and plasma technologies. The educational article was well received and we had requests for a similar article discussing DLP and LCD technologies.
As DLP and LCD have evolved quickly, differences between the two technologies have narrowed. There are still differences that, depending on the situation, may be significant.
DLP projectors employ an optical semiconductor (DLP® Chip) which was invented in 1987 by Texas Instruments. Each DLP Chip contains up to 2 million hinge-mounted mirrors. The mirrors reflect the projectors light source through the projector lens. These moving mirrors create the image. The more time that a mirror is turned away from the light source, the darker the projected image.
A single chip DLP system employs a colour wheel that filters the reflected light from the mirror and adds the required colour. A three chip DLP system uses a prism to divide the projected white light into its red, green and blue components (RGB) with 3 DLP Chips (RGB) dedicated to reproducing the associated final colour. See the two illustrations below of single DLP and 3 DLP projection process.
images from dlp.com
The DLP mirror system displays contrast very well. The contrast is most noticeable when viewed in a darkened room. The "pixel fill" is also very good with DLP projection. The pixels are very close together (1 µ) so the image appears to be natural.
The downside of DLP is that there can be some video noise in the dark area of images. 1 Chip DLP projectors can display a "rainbow" effect. The rainbow effect is a brief streak of red, blue and green colour caused by the spinning wheel and the sequential process of how the shades of colour are created.
Each Liquid Crystal Display (LCD) panel is comprised of hundreds of thousands of pixels. Each pixel is comprised of 2 glass filters with liquid crystal material between the two filters. A small electrical charge is applied to the liquid crystal which allows light to pass through the first filter, the liquid crystal and the second filter.
The image below illustrates the projection process in a 3 LCD projector. The light is split into its RGB components and then passes through the 3 LCD panels (R, G and B). The RGB components are then recombined in a prism and the light is sent through the projection lens.
image from 3lcd.com
LCD projectors reproduce colours very well. When comparing different technologies look at the reproduction of orange, pink and yellow colours, as well as how whites are reproduced. LCD is a good choice when the viewing conditions have high levels of ambient light. LCD technologies also deliver very sharp images.
The main downside of LCD technology is the "screen door" effect. There is more space between the LCD pixels than the DLP pixels so the image does not appear as natural as a DLP image. The black reproduction is generally not as deep when compared to DLP images.
When considering the smaller and lighter requirements of the "road warrior" DLP used to be the preferred technology. The latest generation of LCD projectors have become lighter and smaller though a DLP projector of the same weight as an LCD projector is usually a bit smaller.
As both LCD and DLP technologies have pros and cons, it is not really a matter of which technology is best: the question is what technology is best for your specific application?
For a more in depth look at how LCD projectors are structured, please see the 3LCD.com website.
For more information on DLP projection technology , please see the dlp.com website
For more information on what technology is best for your situation, call your Inland AV location and discuss with our Presentation Systems Sales staff.
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