Sunlight Readable Displays for Outdoor Applications
Posted on May 15, 2022
Using a computer outdoors can be tricky. The screens aren’t really built to be visible in direct sunlight, making it hard to see anything on the display. This is especially a problem for embedded computers with LCD screens deployed in outdoor locations.
Computers meant to be deployed in outdoor scenarios need a different feature set than normal. This is why we have rugged PCs, built to operate efficiently in high temperatures and dust.
But the board isn’t the only component affected by outdoor conditions. Harsh sunlight overrides the luminosity of the display too, making it difficult to see on it. The solution? Sunlight readable displays.
Why LCDs Cannot Deal With Sunlight
Liquid Crystal Displays (LCDs) do not produce any light of their own, relying on a backlight to illuminate the screen. While this works well enough in a darkened room, it doesn’t hold up well against the glare of the midday sun.
Even LEDs, for all their technical superiority, are vulnerable to the same problem. The diodes can produce only so much light, and being subjected to powerful external lighting (like the sun) can make it very difficult to see anything on such a display.
Most monitors are calibrated to work well in indoor environments only, and simply raising their brightness cannot compensate for sunlight. For that, you need a display capable of higher output.
How Sunlight Readable Displays Work
There are two ways of making a display readable in sunlight – either you increase the brightness to exceed the glare of the sun, or reduce the reflectance on the top surface. The idea is to ensure that the light being emitted from the backlight is not overpowered by external rays.
Increasing the internal brightness is the simplest and by far the most common method, as it just requires a more powerful backlight rather than modifying the materials of the display itself.
Normally, LCDs possess a brightness in the range of 200 to 400 nits. To remain visible in direct sunlight, the backlighting needs to be at least 700 nits. Obviously, it is better if the display is capable of raising its brightness above that, as it allows for adjustment for different lighting conditions.
Applications of a Sunlight Readable Display
Sunlight-readable displays are mostly useful in scenarios where an embedded PC needs to be deployed outdoors and needs a prominent display as well.
Smart kiosks, for example, fit the bill perfectly. They are usually set up in publicly accessible spots without air-conditioning or a covered roof. Apart from a fanless computer, these systems need a sunlight-readable display to be able to function during daytime hours.
Such displays are also used in the interfaces controlling outdoor machinery. This includes agriculture, airport, and maritime operations, apart from things like ATMs.
Why Aren’t All Displays Sunlight Readable?
If sunlight-readable displays are so useful, why isn’t the feature built into every LCD screen? The reason is simple: price.
The addition of stronger backlights pushes up the cost factor of these displays, making them a poor choice when that additional power is unnecessary. Besides, the extra brightness is impractical for an indoor display anyways, as normal LCDs work well enough in these scenarios.
There have been some efforts made to achieve sunlight-readable displays using different materials that reflect more sunlight and reduce interference. And while these screens are usable in both high and low light environments, they tend to be even more expensive.
Computer displays used in outdoor locations need to be different than the norm to be readable in sunlight. Usually, this is achieved by simply increasing the brightness of the backlight until it is strong enough to overpower the ambient lighting.
Sunlight-readable displays have brightness levels ranging from 700 nits to 1500 nits, giving them enough luminosity to function even under direct sunlight. On the flip side, it makes them too bright for indoor applications, where a normal screen would be more practical.
Whether you are setting up smart kiosks are outfitting an industrial setup, a sunlight-readable screen is a must to ensure that the system can be used during the day.