May 20, 2011
Technology Used in Projection Televisions
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A rear projection TV is a less expensive alternative option for big screen plasmas and liquid crystal displays. All that one would need to install a rear projection TV is some free space on the floor.
The name itself indicates that the picture in this type of TV is produced by reflecting the light from behind the screen unlike the general traditional projection systems of the past in which the projector is placed in front of the screen like in movie theatres.
The construction of it involves five elements altogether and they are as follows.
- A projection system which is typically used for producing images and videos on the screen is the first component.
- The second most important component is the type of lens assembly used to create magnified images for projection.
- The positioning and the requirement of employing a mirror in the set up to reflect the image projected.
- Another obvious requirement for a rear projection TV is a display screen on which the projected images are being displayed.
- Last but not the least is the requirement of a seal box to contain all the above said components intact.
- CRT (Cathode Ray Tube projection technology) - This method was used by the earlier models of a rear projection set. In this technology three small cathode ray tubes were used represent each color in the RGB series.
These tubes are then coupled with lens that magnify light and this whole setup projects a color image onto the mirrors which is one of the components of rear projection sets and then reflected back to display images onscreen.
- LCD (Liquid Crystal Display projection system) - There is a transparent LCD chip which is made up several small pixels and they are used in this technology. When light passes through this chip it the images are projected and magnified after which they are reflected on to the screens.
This technology is not used these days in the rear projection sets but can be mostly found in the sets which have been sold in recent years.
- DLP (Digital Light Processing projection system) - This technology is the latest innovation in the processing of images in the rear projection systems. Its working is similar to the liquid crystal display projection where in the image is being projected on a chip.
The only difference would be that the chip used in a DLP rear projection sets are entirely different than that used in a LCD rear projection sets. The chip used in the sets is termed as DMD (digital micromirror device) which contains many aluminum mirrors to reflect light and hence the resolution in the DLP sets is high.
At first, the image is produced in the form of a gray scale and then colors are added to the picture as the image passes through the high speed color wheels.
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