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Archive for June, 2010

LED-backlit LCD TV

LED TV. That is how manufacturers called it.

At first, I was thinking LED TV as a new breed of OLED display technology. OLED display is widely used as a screen in smaller devices such as mobile phones and portable media players (the current trend used active-matrix addressing, here comes the name AMOLED). My own Sansa Clip+, for example, uses the simple two color yellow and blue OLED screen, while Zune HD uses colorful and bright AMOLED screen that looked fantastic.

LED OLED display uses arrays of organic light-emitting diodes (LEDs). If you have no idea what LED is, you can easily found the simple LED usually as power indicator in electronic devices. The nature of LED, that is “light-emitting”, suggests that this kind of display is self-illuminating, conclusively.

LCD with LED

LCD display is different. It does not emit light directly, therefore it needs a light source. Modern LCD displays (TVs, computer monitors, mobile phones displays) are built with an internal light source and it backlights from ‘backside’ of the display panel.

The conventional one is using cold-cathode fluorescent lamp (CCFL). CCFLs are placed on edges of the display panel. This kind needs a diffuser to spread the light from the edge sources. See picture below.

561px-Lcd-ccfl.svg

CCFL backlighting is still widely used for notebook displays, computer monitors, and LCD TVs.

Modern one is using LED backlighting.  LEDs are placed right before the display to illuminate it. They can be white LEDs backlight or RGB LEDs backlight.

LEDs can also be placed around the perimeter of display, just like the old conventional CCFL backlighting.

Image courtesy of Sony

They are NOT LED TVs

Seriously, they are not. They are LCD TVs using LEDs to illuminate the screen. Although ASA (Advertising Standard Authority) of UK stated that the term “LED TV” does not object to the use of this term, ASA still requires the term to be clarified in any advertising about the term. But I’ve never heard any clarification from manufacturers, at least until I saw the advertising of LG LED LCD Monitor E2250V. LG is honest enough about its product name, but LG still does not give proper clarification.

Update (20 June 2010)

I got it right! Today I saw Samsung LED TV advertisement on TV, they have added caption saying “LCD TV with LED backlight technology”, something I’ve never seen before.

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