Cutting Display Costs - Color Field Sequential Technology

Color Field Sequential Technology (CFST) is a maturing technology made possible by recent developments in solid state backlighting for example, LED backlighting products.

Justification for the development of Color Field Sequential Technology stems mainly from its potential to eliminate the need for color filters in LCD displays but, also from a range of other advantages. Eliminating color filters delivers both production cost reductions and reduced power consumption in the display products produced. Toshiba Matsushita Display Technology Co are of the opinion that in LCDs more than 70% of back light brightness is absorbed by color filters.

CFST relies on the rapid sequential firing red, green and blue LED backlights. When a particular backlight color in firing, only the LCDs corresponding to pixels requiring that color (for the frame being displayed) are opened to pass the correct amount of primary color for the desired combined color. The perception lag of the human eye works to combine the rapid sequence of colors into a blended color. As a minimum, displays must pulse colors faster than the flicker fusion threshold for the light to be perceived as continuous. The flicker fusion threshold varies between individuals but, is generally over 75Hz.

Samsung demonstrated a 32 inch, LED backlit, field sequential color display at the FPD International in October 2005. The color gamut was 110 percent of NTSC for a power consumption was only 82 watts. However, Ken Werner reported that not everybody was impressed as there was a readily noticeable flicker in the display. An aberration indicative of a technology yet to mature.

In April 2006, Toshiba Matsushita Display Technology Co announced the development of a new TFT-LCD which realized goals of high transmittance, wide viewing angle and high speed response by combining two technologies, Optically Compensated Bend (OCB) and Field Sequential. The new screen technology was displayed at the Society for Information Display (SID) Exhibition in June.

Summary of Field Sequential Technology Advantages

high light transmittance from back light source to screen - As some 70% or more of a back lights beam is absorbed by color filters, their removal greatly boosts the amount of light making it to the screen.
lower power consumption - As more light makes it to the screen rather than being absorbed by color filters the backlight’s wattage (brightness) can be reduced yet, still achieve the same display brightness level.
faster response times - Faster response times are a consequence of the operation of this new technology. As LED lighting is occurring in a sequence of three colors, the display needs to be driven at three times the speed compared to a conventional filtered back light source. Toshiba Matsushita Display Technology Co have quoted a response time of 3.3ms.
higher resolution - Because lighting of display pixels takes place in sequence, the sub-pixels required for normal back lighting techniques are not required. If each sub-pixel is converted to a normal pixel, the resolution is boosted by a factor or three (3). It should be noted that resolution increase can occur with no increased risk of defective pixels (LCD elements). This fact gives manufacturers a productivity boost as display resolution can be increased while yields remains static. The result is potential display price reductions.

» Cutting Display Costs - Color Field Sequential Technology

September 6, 2006

Cutting Display Costs - Color Field Sequential Technology

Summary of Field Sequential Technology Advantages

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