How an Electronic Sun Visor Works

The center console can feel a little crowded nowadays. Ever since consumers decided that every electronic control requires a touchscreen panel, and auto designers complied with those wishes, a car's center stack is beginning to feel a little complicated. We've seen these screens dominate cockpits from luxury sedans and SUVs all the way down to budget compacts. If you've got a car with one of these in-dash computer systems, you might be wondering what's left to deck out. And if you've got an older or less expensive car, you might be searching for affordable alternatives.

So, it's inevitable that electronics designers would start eyeing a previously underutilized bit of surface area -- the sun visor. And, hey, a sun visor can be made just big enough to cram in a 7-inch LCD monitor and a DVD drive. Problem solved!

Some of these aftermarket electronic sun visors can be had for less than $100, and manufacturers claim they're pretty easy to install in most cars, by simply swapping out the stock sun visor (but only on the passenger side, please!) and hooking up the new one. They come in a range of neutrals -- plastic black, plastic gray and plastic beige -- to coordinate (somewhat) with most interiors, and some even include additional features like USB input slots and GPS systems.

DVD player sun visors appear to have been invented to solve a problem that's about two decades old -- how to enjoy film and television in a moving vehicle (on a very tight budget). But hey, the bulkiness and heft of the plastic might block out a bit more sun than the old visor, right?

At best, this is a super inexpensive way to get a DVD player in your car -- that is, if you've got an older car and a desperate passenger, and watching movies on an iPod, smartphone or tablet isn't an option for whatever reason. At worst, well ... it's a sun visor and it's electronic, but in terms of what we need a sun visor to do, it just isn't the kind of electronic sun visor anyone really had in mind.

In theory, some of the technologies used for smart windows would be applicable. Photochromatic glass, which darkens when exposed to sunlight, seems like it would be a good way to make windshields more effective. And it's true that photochromatic technology and other similar smart glass products are already being used in cars. But auto manufacturers seem hesitant to employ anything more complicated -- after all, the main purpose of a windshield is safety, and the strength and shatter-resistant properties of the glass can't be compromised.

However, a solution known as suspended particle devices could be adapted for use in sun visors. Suspended particle devices function like a valve that lets light pass through. Millions of these particles float in a material between two panes of glass (or plastic, in some cases). A control module allows the user to decide how much light to allow to pass through. If full light is desired, the particles are arranged in rows so the sun's rays have a pathway through. To block light, the particles are scattered.

Some companies have tried to put similar ideas into effect. One such product that was once in development was a clear electronic panel that could descend from the car's regular sun visor. In addition to blocking the sun at the brightest times of day, it was also designed to be used at night to reduce headlight glare from surrounding traffic. YES Invent, a development firm based in Israel, claims their visor monitors the driver's eyes to figure out how much glare reduction is necessary and then automatically adjusts accordingly. The price was projected to be less than $300, and YES Invent hoped it would be widely adopted by automotive manufacturers ... but it hasn't happened yet.

Back in 2007, Popular Mechanics and some blogs reported that Volkswagen was working on another system, kind of a combination of the two aforementioned concepts. It used the same sunlight sensors and driver's-eye sensors as the YES Invent's anti-glare visor, but the components were actually embedded into the windshield itself to offer protection in the areas that a regular sun visor simply can't block. It produced a dark spot in the glass that reacted swiftly to changing light and could even move when the car turned. It's reasonable to assume that the system, if ever completed, would have ended up in the Volkswagen group's more upscale models (like Audi, for example) but so far, the electronic matrix sun visor (as it was called back then) has yet to be seen.