There are many different screens. From gigantic vacuum-tube TVs to the flattest of the flat home theater displays, TVs come in all shapes and sizes.
LCD: Liquid Crystal Display – Big Screen, Little Equipment
LCDs, or liquid crystal displays, are what they sound like: a material that has traits of both liquids and crystals is manipulated with an electric current, using a panel behind the crystal panel. Then, an LED panel behind that lights it up so the colors are visible. LCD displays don’t handle heat well, and they’re fragile. You can’t put them next to or above a fireplace, and you can’t clean them with most regular cleaners as a rule. You especially can’t drop them. Videos of people running into their TVs with an AR headset on or throwing a Wii remote into the TV during a virtual bowling game demonstrate the spiderweb effect even minor impacts can cause on-screen.
But the screens are getting massive. A more delicate device is a tradeoff many people are fine with making, if the trend of larger, sleeker smartphones is any indication. For example, a projection screen TV is probably the closest someone in the 1980’s could get to the modern flat screen TV. At 50 inches, and adjusted for inflation to today, it costed about $3,100.
An 82 inch TV from LG currently costs about $1,500 on Amazon. Technology!
LED: Light-Emitting Diodes
The Sphere in our local Las Vegas is currently the largest LED display in the world! LED displays are a common choice for external signs. They’re cheap and easy to manage outdoors, so they’re a great choice for light-up billboards – here in Las Vegas, most casinos on the Strip have one outside for their advertising. However, since the individual components making up each ‘pixel’ or each little square of colors are pretty large, they’re not usually the first choice for indoor, TV electronics – the gaps between each diode cluster are big enough to be visible, and they put out a lot of light.
OLEDs are becoming more popular as a screen choice because the gaps are eliminated, but if an image is going to be displayed on it long term, they can be prone to ‘burn in’ – where the image becomes permanently etched into the screen. As a result, LCD displays are more popular in cases like digital menus and airport queues.
LEDs don’t have many weaknesses that aren’t also shared by LCD screens – the major one is that screen burning, but for big displays like the Casino signs, that’s not an issue. Panels going out and creating wrong-colored squares in the middle of the board are, but thanks to the modular design of LED panels, minor problems don’t kill the entire screen.
Plasma Screen
A plasma screen TV works by exciting little pockets of ionized gas to create plasma, which makes colors. These were all the rage for a while, but they’re also sensitive to heat – and when LCDs caught up, they were cheaper to make and easier to dispose of, so plasma screens dipped in popularity. They’re still high-definition, they’re still sold in stores, so nowadays it comes down to a matter of preference, not price or size.
Rear Projection TV: Big Screen, Big Equipment
These screens were huge, and the speakers were built in to face the viewer at the bottom of the screen. Rear projection TVs were the intermediate step between CRTs and LCDs, and they worked by beaming light from the source of choice to the screen using a system of lenses, magnifying the image. CRTs had reached their max size, but LCD panels weren’t anywhere near large enough by themselves yet – the rear projection TV smoothed the transition between the two while also providing a larger screen than previous TVs. The one I grew up with was gigantic, even at the time we had it. Scratches in the fabric covering the speaker area were the only worry. The TV itself was nigh indestructible, and impossible to knock over.
Over time, the screen we had became outdated. It didn’t have enough ports for all the adaptors it would have taken to keep it in line with new plugins: VCRs and DVRs had different requirements, and so did the Xbox and the Xbox 360. Eventually a smaller (but much thinner) screen won out. Everything could just be directly plugged into the TV instead of screwing with the jack hydra the rear-projection required. The price of progress.
CRTs and Degaussing
With the development of iron ships, navigators discovered a problem – large quantities of iron could mess with the compass, and other tools relying on the Earth’s magnetic poles to function. Even worse, with WWII on the horizon, the magnetic signature of the ship meant that weapons could be designed around it. Underwater mines, specifically, were geared to detect the field and then go off. Degaussing was invented! De-magnetizing the ship meant mines could no longer rely on it as a trigger.
Cathode Ray Tubes displays (or CRT displays for short) are easily disturbed by magnets. The colors turn funny shades when you hold a magnet too close. The same technology used to protect ships was then used to degauss the CRT display and return it to its former full color glory. Eventually, degaussing coils were included within the device, which causes that “Thunk” and then hum when the screen is flipped on. It resets every time the device is turned on, which keeps the image from gradually degrading if it’s kept near other devices with magnetic fields as well.
That doesn’t mean CRTs are immune to breakage: flicking the switch on and off repeatedly and too quickly may break the mechanism that does the degaussing, and you’re back to using an external degausser.
Sources: https://www.doncio.navy.mil/Chips/ArticleDetails.aspx?ID=3031
http://www.thepeoplehistory.com/80selectrical.html
