Many of us hear the terms LED LCD and OLED and assume that they are pretty much the same thing, and some people might not even know the difference between LCD T.V’s and LED LCD T.V’s. One reason for all of this confusion is the way that manufacturers market their products and how they refer to the new “technology” that they put into their devices.
A liquid crystal display (LCD) does not emit light itself, it requires some type of back light in order to see whatever is on the screen. LCD screens basically control light, sometimes they let it through and sometimes they don’t, this is what produces the image we see. Using voltage and transparent conductors, each pixel can be controlled precisely.
When LCD screens first came on to the market they were primarily backlit by CCFL or Cold Cathode Fluorescent Lamps. These CCFL lamps are usually positioned at the edges of the LCD screen and then a light diffuser is used to spread the light across the entire screen. This method of backlighting works really well but dose not produce a very good black. The reason this method doesn’t produce a good black color is because the CCFL lamps remain at full intensity even when displaying the darker part of images, which results in a glowing effect on the screen. Often we hear commercials for T.V’s mention that they have blacker blacks, they are referring to the contrast ratio which is directly related to how backlighting is managed.
More recently, manufacturers have been using small LED lights to illuminate the LCD screen. The LED’s can be placed at the edges of the screen and the light they produce can be diffused just like the CCFL back lighting method. LED lighting uses much less electricity and are much smaller than CCFL’s, which mean you can have a thinner, lighter, and more energy efficient display panel.
In order to achieve a better contrast ratio manufacturers began to dim the backlighting when darker images appear on the screen but this method only helps when the majority of the screen is dark, which is rare in most cases and means that the contrast ratio is basically the same for the majority of what your watching since the display almost never dims. So, how can we get a better contrast ratio for every image that appears on the screen? This is where WLED comes into play. WLED uses an entire array of LED lights that span the entire area of the LCD display. WLED allows for dimming in very specific locations of the screen which results in a very good contrast ratio. Another variation of WLED backlighting involves using RGB LED lighting instead of pure white LED’s. RGB LED backlight screens produce superior color compared to an all white WLED display and also have a solid contrast ratio.
So now that we have a basic understanding how how LCD screens are illuminated we can start to look at why OLED is actually quite different.
Organic Light Emitting Diode or OLED technology, as the name suggests, is an LED that uses organic compounds that emit light when electrical current is applied to them. As we mentioned before LED LCD T.V’s use and LCD screen that is backlight by LED lighting, with OLED displays, the OLED itself is the display, which means there is no need for a backlight. Since OLED displays lack a backlight they offer extremely dark blacks and very vivid and precise colors. OLED’s are basically flat in comparison to traditional LED’s which resemble little bulbs. With OLED’s being so small, manufactureres are able to make extremely thin and even flexible displays. OLED is relatively new and still has a lot of issues including saturation problems. OLED is also quite expensive at this time due to a difficult manufacturing process.
So where does Apple’s Retina display fit in? Well Apple does utilize LED backlight LCD screens that are similar to other displays, except Apple has squeezed in more pixels which creates a higher pixel density, so high that Apple claims the human eye can not see pixelation from a normal viewing distance.
So next time you head out to buy a new display, you can walk into the store with confidence now that you have a better understanding of how todays display technologies work.