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NOTE:  Items highlighted in RED are defined elsewhere in this Glossary, while items highlighted in BLUE are site links for further information.

NOTE:  Over the past decade, screen technology has progressed at an astounding rate.  You’ll notice that even TV shows like NCIS have progressed from CRT screens to flat screens, following everyone else.  And the newer flat screens use less power, are far larger and are higher resolution, continuing the trend.  Therefore, much of the discussion here is historical:

SCREENS.  They’re everywhere.  Televisions. Computers. Cell phonesE-book readers. Smart phones. TabletsPrinters. Each of these devices requires that the user view some sort of video screen to view and sometimes input data.  (Desktop computers use monitors, while the term “screens” is more generic to encompass all electronic devices, like phones, tablets, printers, etc.)  They are interchangeably called screens, monitors, displays, tablets. pads and many other names, but they all serve the same purpose:  To graphically display to the user the data within the device.

But, of course, it isn’t that simple.  There are many different types of screens.  This is primarily because these ubiquitous color displays consume considerable battery and electric power the more they are used.  And each new generation of smartphone, tablet and computer finds more and more ways to suck up energy - viewing movies, playing games, video phone calling.  So the goal is to constantly provide the clearest possible display with the longest possible battery life.

How is this done?  One way is to keep the display in black and white (like the original Kindle e-book reader) and not color (like, for example, the color Nook or the Amazon Fire).  Another way is to increase the battery size and speed up the charging process.  Also, by changing the battery type (e.g. from NiCad to LioN), increasing efficiency.  But by far the best process has been the steadily progressive technology, making the screens thinner and less power hungry.

CRTscrt monitor

The original TVs and computers relied on the bulky, heat-emitting cathode ray tube (“CRT”) technology.  These displays required full electrical power and could not be used with batteries. Essentially, the CRT shoots an electron beam through a vacuum at a glass screen, the interior of which is coated with phosphors. As the beam passes through a magnetic field which varies in strength according to an electronic “display controller” and then a mask (or “mesh”) which defines the individual pixels and the resolution (see LINK about “dot pitch”) on the screen (either an “aperture” grille (thousands of holed) or a “shadow mask” (vertical slots)), the electrons are sorted by colors (red-green-blue, the so-called “phosphor triad”) and the individual phosphors light up in analog color, which is interpreted by the video card for display.  CRT screens must be degaussed periodically.

cathode maskdot pitch

Here’s an interesting fact: Your color TV  and the old CRT (a/k/a “RGB”) monitors display the color white by displaying the red, green and blue pixels at the same time, an optical illusion which fools your eyes into seeing only white, because most human eyes have three color sensors, red, green and blue (“RGB”) [some people have a fourth sensor, which changes the results for those few people].  So, for the majority of humans, true white makes all three RGB sensors respond.  If you view the screen with a magnifying glass, you will verify this, according to Richard Muller, Prof. of Physics, UC Beerkeley.

LCDs

CRTs became extinct when users discovered LCD screens, the thin, flat panel monitorlight and cool monitors that made room on a desk and looked sleek rather than clunky. Generally, these screens were lumped into the description “Flat Panel Displays.” 

LCDs, short for Liquid Crystal Display, became immediately used on watches, TVs and computer monitors.  Developed in 1963 at RCA’s Sarnoff Research Center in Princeton, NJ, LCD displays use two sheets of polarizing material with a liquid crystal solution sandwiched between them.  When an electric current is passed through the liquid, the crystals align so that light cannot pass through them.  Each crystal is like a shutter, either allowing or blocking light.  Color LCD displays use two basic techniques for producing color: Passive-Matrix (including CSTN and DSTN technologies); and the much more popular Active-Matrix (a/k/a thin-film transistor or “TFT”).  Most LCD screens used in laptop computers are backlit, or transmissive, to make them easier to read.  Most popular these days in phones and computers are TFT-LCD screens, which usually have four layers:  a backlight, a TFT color filter, a touch-sensor panel and an outer glass screen.

 

       CREDIT:  www.bit-tech/net

lcd2

 

Naturally, LCD screens have different considerations from CRTs.  First comes “contrast ratio.”  Although there is no official standardized measure defining this ratio, it is generally accepted as the comparison of the brightest possible white compared to the darkest possible black, expressed as a ratio.  The higher the ratio, the better the screen. For example, if the maximum white brightness is 500 and the minimum black is 1cd/m2 (see brightness, below, for explanation), then the ratio is expressed as 500:1.  This becomes necessary because the backlight on the screen can’t filter out all of the light for a true black, which sometimes appears more gray, while turning down the backlight will conversely make the black blacker while reducing the brightness of white at the same time.  Common ratios are 300:1 to 600:1 for computer monitors (TVs can be up to 800:1 to 1200:1) because viewers typically sit several feet away, not just a few inches as they do with a computer.

The brightness ratio is also a consideration.  Because LCD screens have a backlight that provides the luminance that lights the entire screen, the peak luminance is a hardware issue.  Typical white luminance (which is actually a product of the red, green and blue luminance components) for a notebook computer is about 150-400 candela per square meter (“cd/m2”).  But this measure dramatically drops off when the screen is viewed from an angle, and also depends on the components of the LCD that it must pass through (diffuser, polarizer, filter, etc.); it can start at 3000 cd/m2 and end at only 150 - 300 cd/m2!

In an effort to make LCDs faster, some manufacturers have reduced what is known as “bit depth.”  Beware of this if you’re doing graphic design.  Normal quality dictates 8 bits of color per RGB channel, resulting in a total of 16.7 million colors.  But if the bit depth is reduced to 8 bits, color may be compromised, requiring “dithering,” which is the use of software to “fake” the missing colors.  [By the way, this is NOT the same thing as the 32-bit color in your video card and your computer desktop, which is almost always fully usable.]

Next, consider “refresh rates.”  Most older monitors have adjustments for this.  Refresh rate is the number of times per second that the screen is refreshed.  The higher the better.  If it’s too low, the screen image starts fading before it’s renewed, causing that annoying “flicker.”  60Hz resolution is a minimum on a smaller screen with less lines to renew, but 100Hz is best on larger screens.  However, on LCD screens you should be more concerned with “response time,” which isn’t the same thing.  In LCDs, this is the amount of time in which a liquid crystal can twist, then untwist, to either pass or block the light for each pixel.  The faster they can accomplish this, the quicker the screen.  Response times are stated in milliseconds - below 16ms is pretty good, but you can get and will want 8, 4 even 2 milliseconds if you’re a gamer.  LCD/LED TVs can have either 60Hz, 120Hz or 240Hz refresh rated.  The more action or sports you view, the higher the refresh rate should be to prevent “chattering” during fast movements.  Unless you are a die-hard sports fan, 120Hz is more than sufficient.

Finally, LCD and later types of screens changed the square shape which were the universal property of the CRT screens, which was necessary due to the nature of the cathode ray tube technology.  Screens became wider but less tall, allowing users to view more on the sides of their screens, even (starting with Windows 7) viewing two windows side by side on the same screen.  For more about this principle of “aspect ratio” see the display format LINK.

Aspect Ratio 32Aspect ratio 169

PLASMA

About the same time, PLASMA technology emerged.  This plasma display panel (“PDP”) technology is primarily used in large-screen (42” or greater) televisions.  Plasma is similar to LCD technology but, instead of liquid crystal, the display is created by thousands of tiny tubes filled by inert ionized gas in a plasma state between the panels to provide the image.  Because of this construction, plasma is very light and flat, permitting hanging TV screens directly on a wall.

LED

The next generation of screens, used on laptops, but more on cell phones and TVs, uses light-emitting diodes (“LEDs”) originally used for electronics indicators and low voltage display lighting.  A diode is a semiconductor device (a solid electronic component that conducts electricity under specific conditions) that emits light when an electric current passes through it.  The difference between LCD and LED is this:  LCD chips do not produce their own light.  Rather, they have to be backlit, either through fluorescent edge lighting (not as good)  or full array backlighting (much better, especially if it employs “local dimming,” which independently turns off certain areas of the screen, providing control over brightness/darkness in those areas).  LED chips use LEDs to backlight the LCD pixels.  LEDs are brighter than LCDs, which is why the contrast ratio is over the 150k:1 ratio for LCDs.  LEDs are quite thin and light, use less power and light up each individual pixel and show more colors and better dark colors, but also can create some loss when viewed from a side angle.  Most computer monitors work quite well at the default 60Hz refresh setting.  If you’re looking as a consumer TV, however, you will require at least 120Hz or even 240Hz, because action films or sports will become choppy if viewed at the lower rates.  These days, many large screen TV’s have both LCD and LED screens, which provide an enhanced viewing experience.

LED/LCD RELATIONSHIP

In actuality, every screen is an LED LCD screen.  That’s because LED and LCD actually refer to completely different parts of a TV or computer screen.  While LCD refers to the technology for the screen, LED only refers to the LCD screen’s backlight.  They work together.  LCD alternatives are either plasma (pretty much extinct) or OLED (still rather expensive, used mostly in smart phones).  And LED is used almost universally because it’s brighter, more energy efficient and lasts longer.  So these days, almost all TVs and monitors are LED/LCD technology.

OLED

After that, LED technology progressed to the newer, OLED (organic LED), which is a display technology based on the use of an organic substance, typically a polymer, as the semiconductor material in light-emitting diodes.  An OLED display is created by sandwiching organic thin films between two conductors.  When an electrical current is applied to this structure, it emits a bright light.  OLEDs don’t require backlighting, can be thinner and weigh less than other display technologies,  offer a wide viewing angle (up to 160 degrees), have less video blur and use less power (only 2 - 10 volts). They are consequently quite popular on TVs, laptops, and PDAs.  [For this reason, the brightness and contract ratio formulas discussed above don’t apply].  But they do have some problems with glare and readability in direct sunlight, even relative to LCD screens.   To be expected, there have been several types of OLEDs.  Just like LCDs, OLEDs can be either AMOLED (“active matrix LED,” where each pixel is driven separately, using two transistors and one capacitor) and PMOLEDS (“passive matrix OLEDs,” which drive the pixels by row and column (x-y) coordinates).

2017 UPDATE:  The obvious trend over the past few years has been to move from LCDs and LEDs to OLEDS in cell phones, TV screens and even light bulbs and OLEDS will probably replace these earlier devices.

Samsung has introduced the Super Amoled screen, which is “super” because the touch screen display integrates the touch sensors with the glass surface panel, eliminating at least one layer of glass and, with it, a layer of air. It also enhances readability, reducing the glare problems experienced with AMOLED.

Amoled

There are also several rather expensive technologies in the market, but they have not become as popular as Super AMOLED:  Super LCD, Super IPS and Advanced SuperView.  Basically, each phone manufacturer uses its screen(s) of choice.  You have to select your carrier, then your phone, considering the screen that you think will be best for you.

FOLED & FUTURE DISPLAYS

The newer OLED technology has morphed to include the FOLED (flexible organic LED), which is built into a portable, roll-up display.  The newest LEDs are being created using ultrathin inorganic LEDs which are brighter and more versitile (bendable; think human body or building displays). 

Even more recently, companies like Plextronics (founded by Richard D. McCullough) have been perfecting electronic “ink,” a flexible polymer that can be printed on anything, even a magazine page.

In the further future, expect ultra-thin, flexible screens made of graphene, a carbon-based “wonder material” 100 times stronger than steel and so thin that a single ounce of it could cover 28 football fields.  The American Chemical Society says graphene is currently in development for use in solar panels covering, for example, the entire outside of a building.  Cell phones, touch screens and other appliances will be sure to follow.  Someday, cell phones may be as thin as a piece of paper and foldable enough to fit into a pocket; and, because of their strength, they would still be nearly unbreakable.

 

BUT WAIT...NOW THERE ARE QUANTUM DOTS!

 

On smaller screens, at least, OLED screens produce vibrant, richly hued images, and are much more efficient than liquid crystal displays (LCDs), although they’re still quite expensive to make in larger sizes.  Now a handful of start-up companies are attempting to improve on the LCD by adding “quantum dots,” the light-emitting semiconductor nanocrystals that shine pure colors when excited by electric current or light.  When integrated into the back of ordinary LCD panels, the quantum dots promise to cut power consumption in half while generating 50% more colors.  Quantum dot developer Nanosys says that an LCD film that it developed with 3M is now (2012) being tested and that a 17 in. notebook incorporating the technology should be available by the end of the 2013.  (UPATE:  Haven’t heard much about this.  Maybe it didn’t make it.]

TOUCH

Finally, there is an entire generation of touch sensitive screens, whether full size ones used for input in business like restaurants, to the smaller smartphone and pad links on modern iPads, iPhones and Windows devices like phones and the Surface pad, which allow resizing, typing and selection.  (Like the Amoled design shown above.)   (See also, Leap.) But the underlying resolution and technology are still based on the distinctions discussed above.  Some people don’t like the fact that touch screens can be quite unhygienic, a recent report finding that the touch screens on mobile phones, tablets and public (e.g. ATM) touch screens can have twenty times more germs than a toilet seat.

FREQUENTLY ASKED QUESTION:  Are those computer screens shown on TV, like CSI and Hawaii-Five-O real?  You know, the ones where the investigator flicks a screen or pad and the content whooshes to the huge wall monitor?  Yes, they do.  The multitouch technology is made by DoubleTake’s FlickIT, which lets a user “flick” data or content from one touch screen to another, as from a pad or desktop screen to a wall mounted monitor.

 

CONNECTORS AND PORTS

As with any other peripheral, desktop computer monitors rely on cables, connectors and hardware cards (built in to the motherboard or riser cards) in order to function.  Depending on the purpose of the computer (e.g. gaming, server or simple use), the video card, connector and capacity will vary.  Click HERE for more discussion.

THE FUTURE

What’s in store for the future?  Holographic and 3D projection is  possibility.  But that hasn’t been widely accepted in the television industry, so it might not make it with computer screens either.  A possible alternative is Displair, a projection company owned by Russian designer Max Kamanin, the future may be projection 3D images onto sheets of mist, giving the illusion of a hologram.  These “screen-free” displays respond to gestures and can be scaled to be much larger.  And more hygienic, too (see touch screens, above).   Google, Coke and Pepsi are testing these displays in advertising right now.

And in 2014 Samsung introduced TV and other screens that are curved (105 inch Ultra HD) as well as “bendable” screens (85 inch UHD). So did LG, a 55 inch version at $5,999.  While they won’t be inexpensive and they’re huge, at least it introduces a trend with new screens.  Same for cell phones like the LG Flex.  The reviews are out about whether these curved screens really provide a better “experience”.  Generally, the TVs are more favorably reviewed than the smart phones, which may be easier to hold, but more difficult to operate with only one hand or even two.  We’ll see if they take off, or follow in the footsteps of 3D TV screens.  Photos below:

 LG Flex PhoneFlex screen TV

It’s important to have some, but certainly not all, of the information above if you’re purchasing a device with a screen.  It matters what you’ll be using it for, how much battery life you’ll require, how much color you need, how clear or bright the display has to be.  You may not always have a choice on these matters, as your carrier or monitor manufacturer may not offer everything.  But at least you know what to avoid and what the standards are. [Rule of thumb for TVs:  An LCD/LED display, 4K if you can afford the upgrade, with 1080dpi and a 120Hz refresh rate should do the trick for most users.  Built-in internet is almost a must, particularly if you’re cutting the cord. ]  For more about TVs, click HERE and also read FAQs 44 and 46.]

Wait for a few months.  Something new will probably come along.  But, like everything else, only buy what you think you’ll need and actually use, otherwise it’ll be a waste!

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