Liquid crystal display technology works by blocking light. Specifically, an LCD is made of two pieces of polarized glass (also called substrate) that contain a liquid crystal material between them. A backlight creates light that passes through the first substrate. At the same time, electrical currents cause the liquid crystal molecules to align to allow varying levels of light to pass through to the second substrate and create the colors and images that you see.
Active and Passive Matrix Displays
Most LCD displays use active matrix technology. A thin film transistor (TFT) arranges tiny transistors and capacitors in a matrix on the glass of the display. To address a particular pixel, the proper row is switched on, and then a charge is sent down the correct column. Since all of the other rows that the column intersects are turned off, only the capacitor at the designated pixel receives a charge. The capacitor is able to hold the charge until the next refresh cycle.
The other type of LCD technology is passive matrix. This type of LCD display uses a grid of conductive metal to charge each pixel. Although they are less expensive to produce, passive matrix office monitors are rarely used today due to the technology's slow response time and imprecise voltage control compared to active matrix technology.
LCD displays offer super sharp pictures and great color. But do the pros outweigh the cons when it comes to LCD TV displays? Before deciding on a thumbs up or thumbs down, you should understand how an LCD display works.
Poor reproduction of blacks: Compared with direct-view tube displays, LCDs do a poor job of reproducing black images. Darker screen images never show up as true black, but rather as various shades of gray, and actions happening in these darker areas are difficult to discern.
Limited viewing angle: Although they are getting better due to some intensive efforts by manufacturers, LCDs typically have a poor viewing angle. If you are not sitting almost directly in front of the screen, such as 21.5 inch screen pc, or 24 inch screen pc, you don’t get a good picture.
Limited brightness: Because LCDs use a backlight shining through the liquid crystal, most of the light is absorbed. As a result, the LCD displays have lower contrast and are harder to view in a brightly lit room (the picture appears washed out), compared with plasma TVs. LCD TVs with LED backlights do better in this regard.
LED vs. LCD TVs explained: What’s the difference?
Despite having a different acronym, LED TV is just a specific type of LCD TV, which uses a liquid crystal display (LCD) panel to control where light is displayed on your screen. These panels are typically composed of two sheets of polarizing material with a liquid crystal solution between them. When an electric current passes through the liquid, it causes the crystals to align, so that light can (or can’t) pass through. Think of it as a shutter, either allowing light to pass through or blocking it out.
Since both LED and LCD TVs are based around LCD technology, the question remains: what is the difference? Actually, it’s about what the difference was. Older LCD TVs used cold cathode fluorescent lamps (CCFLs) to provide lighting, whereas LED LCD TVs used an array of smaller, more efficient light-emitting diodes (LEDs) to illuminate the screen.
Since the technology is better, all LCD TVs now use LED lights and are colloquially considered LED TVs. For those interested, we’ll go deeper into backlighting below, or you can move onto the Local Dimming section.
