Digital displays are everywhere. Chances are you don’t spend a single day without looking at one. (You are looking at one right now.) There are several types of them. The different names and acronyms used to describe them can be a little overwhelming. The following answers from the internet will clear things up for you once and for all.
So these are terms that refer to some fundamentally different things. I’ll throw a few other terms in the mix that will hopefully clarify things.
- Cathode ray tube (CRT) where an electron beams is used to excite colored phosphors on the inside of a glass screen. You may have heard it referred to as a “tube TV”. This is pretty old stuff, and is the earliest display technology for TVs.
- Plasma displays, where a gas inside each pixel is made to glow. This is now pretty outdated, but still way newer than CRTs. It was especially common back when LCD TVs were new, and lower quality than they are today.
- LCD (liquid crystal display). This is the most common type of display tech for televisions. There are three different colors of pixels (red, green, and blue) that can be made more or less opaque to let through light being created by a backlight behind the screen. The combinations of red, green, and blue can be used to form millions of different colors.
- AMOLED (active matrix organic light emitting diode). Each pixel is made of of individual little lights that don’t need a backlight. This is newer, and is being used in a lot of newer phones, but is still very expensive for large TVs.
Note that backlights are only needed for LCD displays
- Cold cathode. This uses a light similar to the overhead fluorescent lights used in stores and office buildings.
- LED. This uses LEDs (light emitting diodes) to provide the backlight. Newer TVs will have hundreds of individual LEDs to provide even lighting and the ability to dim different sections of the screen to provide better contrast
- Retina Display. This is just a fancy Apple buzzword for having lots of pixels that are really tiny, so you can’t see the individual pixels on the screen even when you look pretty closely.
Retina Display is not a technical designation, it’s a marketing term. There are numerous display resolutions available in PCs (FHD, QHD UHD, etc.) and Apple wanted to have a trademarked way to describe their display resolution that nobody else could legally use to make it sound like a unique offer.
Depending on the device and screen size the term “Retina Display” can refer to significantly different resolutions and varying pixel density, though generally it means the pixel density is high enough that you cannot make out individual pixels at standard viewing distance. The Microsoft version of this is “PixelSense”, which is again a marketing term rather than anything that has technical meaning.
Retina display refers to a display with pixels small enough that the human eye is physically incapable of distinguishing the difference between adjacent pixels, at a given distance. This is kind of funky because our eyes don’t work with pixels but it’s probably a decent approximation.
LCD stands for liquid crystal display and basically works by having pixels made of liquid crystals and by applying a certain voltage they will let through different amounts of red green and blue light. The light comes from a backlight (typically one or many LEDs these days).
OLED stands for organic light emitting diode and has tiny colored LEDs in each pixel. This is why a black pixel can emit zero light unlike an LCD which just attempts to block all light from the backlight.
(AMOLED means “Active Matrix Organic Light Emitting Diode”.)
Active matrix refers to how the pixels are arranged on the display. “Organic” refers to the materials used to produce the pixels.
Here’s an interesting tidbit, Samsung is the industry leader in AMOLED displays for many years now, they’ve been manufacturing their own AMOLED displays, using them in their own flagships and selling them to their competitors too for almost a decade now. They also have the best quality AMOLED displays (Currently the Note 8 seems to have the best display of any phone) in the market, LG being the only other company that’s even remotely close to them.
Reports came out this year that Google has almost a Billion dollars invested in LG’s OLED operation, and that Apple is also going investing upwards of 2.5B dollars in LG’s OLED division. The purpose for this is to help LG break Samsung’s ‘monopoly’ on the AMOLED business.
Apple has been putting off moving to AMOLED displays (They used IPS LED displays in all their previous phones) for their iPhones because no company could handle their requirement until this year when they finally started using Samsung’s AMOLED displays in their iPhone X, which also meant paying a much higher price. Samsung is reportedly making over a $100 per iPhone X sold, because of the AMOLED display, while Apple only paid around half of that when they used LED displays.
Google didn’t opt for using Samsung’s AMOLED displays in their Pixel 2 devices this year went with LG’s OLED panels instead and there have been many reports of various kinds of issues with those displays.
There’s a whole bunch of different display technologies out there today. LCD (liquid crystal display) being the most common. As the name suggests, you have some electrically sensitive crystals that can polarize light when you pass a current through them. Sort of like a high tech Venetian blind. LCDs don’t produce light on their own though. (Think the original Gameboy.) So they need a backlight to make the screen visible. Originally they used bulky CCFLs (sort of a cross between a neon lamp and a florescent tube), but were eventually replaced with LEDs. These were marketed as LED TVs to differentiate them, and make an easier upsell. The main advantage with LEDs is you can make thinner, more energy efficient displays. Nearly all LCD displays use them now.
The problem with LCDs is they can’t display true black. The best ones can block most, but not all light from the backlight. So blacks will always look a bit washed out, resulting in reduced contrast ratio and colour accuracy. CRT and plasma displays can produce true black, but they have their own shortcomings in regards to size and power consumption. OLED is the next gen technology to replace them.
OLED stands for organic light emitting diode. They’re tiny LEDs made using an organic material that emits light in response to electrical current. An AMOLED display is a matrix of these, with each sub pixel (the red, green, or blue bits of a pixel) being its own individual OLED. They generate their own light, so a backlight isn’t needed. And since you can turn them off completely, it can display true black. Hence better colour accuracy and contrast. Using organic materials also allows for thin and flexible displays. They do have some shortcomings though. They consume more power than LCD panels when showing a lot of white, like a text document. There’s also lifespan issues with blue OLEDs. Lastly, they’re quite a bit more expensive than LCD displays. Though prices have dropped significantly in the last 10 years.
A Retina display is just a marketing term Apple used when the iPhone 4 first came out, to differentiate it from older devices. Basically anything with a 264ppi (pixels per inch) display or higher. Which is basically every phone now. At that point, the individual pixels are so small that that the average person would be unable to see the individual pixels at the closest comfortable viewing distance. A lot of low resolution LCD displays had a noticeable “screen door” effect, including early iPhones and the OG iPad, which is what the high PPI displays sought to address.