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triple twist

A supertwist variation that twists crystals to 260 degrees for improved clarity. See LCD.


(Liquid Crystal Display) A screen display technology developed in 1963 at the David Sarnoff Research Center in Princeton, NJ. How LCDs work is quite amazing. Sandwiched between polarizing filters and glass panels, rod-shaped molecules of liquid crystals flow like water and bend light like crystal. The overwhelming majority of TVs and computer screens are LCD (see LED TV). Mobile devices are also LCD but are switching to organic LED (OLED), which is increasingly becoming mainstream (see OLED). See liquid crystal.

Twisting and Straightening
The center segment of the "8" in the seven-segment display above shows how liquid crystal molecules twist to let light flow through (image courtesy of LXD, Inc.). Seven-segment displays are the simplest LCDs. All video screens use pixels made up of three LCD subpixels with light shining through color filters. For example, in a 4K TV set, there are 24 million subpixel segments. For a more in-depth explanation, see LCD example and LCD subpixels.

Reflective Vs. Backlit
In low-cost calculators and readouts, a reflector bounces ambient light back to the viewer (bottom of illustration). However, reflective displays may be unreadable in dim light. With backlit LCDs, a light below the reflector beams toward the viewer for a bright screen indoors (see transmissive LCD). Passive displays may be reflective or backlit, but active matrix TV and computer screens are always backlit (see LCD types and LED TV). See flat panel display, LCD vs. plasma, LCoS and indium.

Seven-Segment LCD Watch
Because it took so little power to move crystal molecules, LCD wristwatches and other monochrome LCD displays began to flourish in the late 1970s. By the 1990s, color LCDs helped laptop sales boom, and LCD computer monitors outsold CRTs for the first time in 2003. (Image courtesy of the private collection of Peter Wenzig.)

LCDs and LEDs are widely used in combination as in this printer panel. Readouts are LCDs, but the indicator lights on billions of products are LEDs. LCD TVs use LED backlights (see LED and LED TV).

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