Special light-blocking materials are used in selective lighting to control particular parts of the backlight, decrease light bleed, and increase user input. It’s particularly useful for capacitive touch screen applications that demand a high level of user response and image quality.
In recent years, LCDs with LEDs getting more and more advanced. One of the functionalities of LCDs with LEDs is local dimming. The LED-backlight adapts to the displayed picture, enhancing the difference between dark and bright areas. It provides a better picture quality with improved contrast and colors.
There are two main types of LED’s backlights
- edge-lit with LEDs on the edges of the screen, pointing inward; there are four schemes – each edge, just right and left, just top and bottom or just top or bottom,
- direct-lit with LEDs behind the screen, pointing towards the viewer.
What is the difference between edge-lit and direct-lit?
The key factor is the precision of local dimming.
There is a simple rule – the more lights, the better effect. Even in the most precise of edge-lit LCDs with LEDs on each edge, there is a noticeable blooming around the bright objects (unfortunately, it is always bond to the edges of the screen). No doubt, the most precise local dimming has been achieved in LCDs with LEDs behind the screen (also called full-array). In this solution, the LEDs are divided into the ‘zones’ that correspond to accurate spots on the display.
What is more, the local dimming is energy-efficient. All in all, we rarely watch scenes that are completely brightened, so only some areas of the screen have to be lit. The selective backlighting reduces power consumption.
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