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LCD Vs. LCoS: Projector Technology Face-off

LCD Vs. LCoS: Projector Technology Face-off

The technology used for projection plays an important role in determining the quality and resolution of an image. Though most consider LCoS to be a new technology, it is actually a derivative of LCD technology. By providing the main differences, this Techspirited article helps you decide which among the two, LCD or LCoS projector, is better.
Bindu swetha
Did You Know?
General Electric was the first company to demonstrate the concept of LCoS in 1970, while in 1972, the first active-matrix LCD panel was produced in the United States!
Liquid crystal displays (LCDs) are one of the oldest and most popular methods of projecting an image. This display, or the technology behind projecting an image through this display, took the market by storm, and is today used in consumer as well as business products. On the other hand, liquid crystal on silicon (LCoS) is a derivative of the LCD method itself.

Though LCoS has been around for some time now, it is only recently that the micro-display technology is being used in consumer and business markets. Though LCoS is a derivative, it is different in more ways than one from its parent technology. So, as a consumer, it can be slightly confusing to determine the better of the two. This Techspirited article will try to enlist the major differences between LCoS and LCD, and also take a look at the pros and cons of both display technologies.
The Differences
Parameter LCD LCoS
Contrast Ratio Medium Medium
Viewing Angle 160°+ 180°
Weight (lbs) Light Heavy
Power Use Low Medium
Pixel Density Low High
Brightness High Low
Cost Cheap Costly
LCD Technology Explained
LCD projectors have liquid crystals for every pixel. It contains three separate liquid crystal mirrors, one for red, blue, and green, each. These mirrors are preceded by polarizing filters. Light from the source passes through a polarizing filter, which aligns the light waves into a single beam. The flow of light depends on the voltage applied to liquid crystal, and this voltage changes the amount of light passing through each crystal. This beam is applied to the color filter which develops each color according to the amount of light that passes through the crystals. From here, the individual pixels will allow or block the light to pass. This light charges the transistors in the matrix which, in turn, controls the amount of light reaching the individual color filters, and then, are fed to the front polarizing filter. The front polarizing filter is placed right before the screen. Hence, the liquid crystal display technology is also known as 'transmissive' technology.
lcd projector technology
Pros:
  • Good color saturation
  • Have higher light output, i.e. increased brightness level
  • No distortion at native or zoom levels
Cons:
  • Dead pixels visible in native resolution
  • Being organic in nature, they exhibit problems if used for more than 8 hours/day
  • Highly sensitive to dust spots
LCoS Technology Explained
Here is an overview of the LCoS technology. As stated earlier, the LCoS technology is the derivative of LCD, while it can also be termed as an hybrid of DLP (Digital Light Processing) and LCD.

The LCoS technology combines the liquid crystals from LCD technology and uses the same as reflective mirrors like the DLP technology does. Thus LCoS is a reflective technology like the DLP technology. Like LCD projection, LCoS also uses three LCoS chips that will modulate light in the red, blue, and green channels. The light from the source is passed through dichroic mirror which reflects only a select few wavelengths of light, while lets others pass. This mirror splits the white light into yellow and blue light. This yellow light is further fed to another dichroic mirror which splits it into red and green light. The red, blue, and green light is allowed to pass through polarizing filters, and sent to the three LCoS chips (prisms). Certain wavelengths from each light are reflected by individual prisms, while others are allowed to pass. The reflected light is again fed to a dichronic prism which recombines these light waves, and converts them into visible light.
lcos projector technology
Pros:
  • High color saturation and contrast
  • Smooth and sharp images due to high resolution
  • High resolution, starts at SXGA
Cons:
  • Extremely pricey
  • Dead pixels problem exists
  • Has higher heat dissipation as compared to LCD technology
Our Verdict
Even though both display technologies provide bright and sharp images, due to the high cost of LCoS technology, it is not commonly found. Leaving aside the longevity problem of LCD, the technology is best-suited for all your home and business needs. As LCDs are cheaper, they are commonly found. Our verdict says, though LCoS is an amazing mixture of DLP and LCD, it will take a few more refinements to the display technology to make it suitable for the consumer market. Theoretically, you cannot question LCoS's abilities, but practically, LCD is the technology to stick around with.