Why do LED screens use the virtual pixel technology, and what exactly is it? The virtual pixel is a video-management feature that allows a 400% increase in image quality. LED screen manufacturers use it to show better quality, realistic-looking images.
But why do LED screens need to increase the image quality through a video-management feature in first place? It's pretty simple: despite its huge size, an LED screen usually has many less pixels than the common computer screen you are looking at right now. How is that possible? Because on an LED display, the distance between two pixels can be up to 30mm or even more. As a result, on a normal computer screen, you have 1024x768 physical pixels or more while on a 4x3 meters LED wall you have 192x144 physical pixels. Big difference!
So how can we actually see anything on an LED screen with a resolution of only 192x144 (27.648 physical pixels total)? Easy! Thanks to the virtual pixel technology, we can double the number of pixels in length and in height. Therefore we can increase the number of pixels perceived by the human eye by four times. So the same screen with virtual pixel technology will have a perceived resolution of 384x288 pixels (or 110.592 pixels). Isn't that beautiful?
Now you are probably asking how is that possible? Well, there are two different types of virtual pixels: geometrical/squared and interpolated. In Part 1 of this article we will discuss the geometrical/squared virtual pixel technology.
This technology is based on pretty simple geometrical concepts. If you have two identical shapes placed next to each other, by taking half of each shape you can create other two identical shapes. For example, if you have two identical pixels lying next to each other, by taking half of each pixel, you can create two more pixels identical to the first two, doubling the number of pixels from two to four. Now imagine to double the number of pixels you have in length, and with the same technique double the number of pixels you have in height: to increase the number of pixels (and therefore the image quality) by 400%.
There are some limitations and side effects of this technology, especially when compared with the interpolated technology. The geometrical/squared virtual pixel technique uses half of two adjacent pixels to create other two. It is pretty easy and straightforward once you understand the mechanism, but there is one limitation.
We just saw how two adjacent pixels can create another two by "switching" the side LEDs of each pixel. In this case everything worked fine because the distance between the LEDs is the same distance between the pixels. But let's say for example that I have an LED screen with a bigger pixel pitch for higher viewing distances. What happens if the distance between LEDs and pixels is not the same anymore? In this case the virtual pixel is not identical to the real pixel anymore. The virtual pixels are more stretched than the real ones and therefore the overall image quality will be affected.
Over the past 15 years some manufacturers developed a technology that allows going beyond these limitations and guaranteeing a superior image quality with any resolution. Does it mean that the geometrical/squared virtual pixel is not a good technology? Well, let's just say that it is definitely not the most recent one. Some LED wall manufacturers still use it, so when considering your LED screen supplier, make you check how their virtual pixel technology works.
Part 2 of this article will be featured in an upcoming Live Design Projection Now eWire.
Fabio Aversa is marketing manager for Euro Display LED screens, an LED screen manufacturer and supplier founded in 1978.