Whether it’s a TV, computer monitor, human machine interface (HMI) or any other liquid-crystal display (LCD), a backlight must be used to illuminate the liquid crystals. Without a backlight, you wouldn’t be able to see images on the display device. Unless you’re familiar with backlighting technology, though, you might be wondering how it works exactly.

Overview of LCD Backlights

The purpose of backlights in an LCD is to illuminate the liquid crystals. In the past, backlights weren’t always needed with display device. Cathode ray tube (CRT) display devices, for example, create their own illuminate, thereby eliminating the need for backlights. Light-emitting diode (LED) displays also produce their own lighting using an array of many small LEDs. But LCDs don’t have the ability to produce their own lighting, so manufacturers must design them with a separate, built-in light source. Known as a backlight, it’s essential to an LCD’s operation. It projects light from behind the liquid crystals, illuminating the display so that you can see colored images depicted on the screen.

Backlights May illuminate From the Side As Well

Based on the name “backlight,” you may assume that they always illuminate liquid crystals from the rear. While true for most LCDs, though, this isn’t always the case. Some LCDs are designed with backlights on the side of the liquid crystals. It’s an alternative configuration that allows for ample illumination while conserving space in the process. Configuring an LCD with backlights on the side creates a lower profile, thus allowing for slimmer LCDs. With that said, some LCDs are configured with lights on the front. These aren’t technically backlights, however. Rather, they are referred to as “frontlights.

Different Types of LCD Backlights

All LCD backlights are characterized by their ability to illuminate the liquid crystals in an LCD. However, there several different types of LCD backlights, each of which uses a different light source. LEDs have become one of the most popular and widely used backlights for LCDs. They are energy efficient, long-lasting, produce minimal heat and highly reliable.

Another common type of backlight used in LCDS is electroluminescent (EL). EL backlights have been around for decades. And although they lack the energy-efficient properties of their LED counterparts, they are still a viable option to consider.

In addition to LED and EL, other backlights used in LCDs include cold cathode fluorescent lamps (CCFLs), hot cathode fluorescent lamps (HCFLs) and external electrode fluorescent lamps (EEFLs).