# Monitors
## CRT

CRT stands for Cathode-ray tube, this type of monitor was the most widely used until the release of LCD monitors (and TVs), the same technology employed was the same as the one used in common televisions screens. The Cathode ray projects a series of electrons onto a screen to ultimately produce an image, however the process of electrons to an image is much more tedious than a simple conversion.
CRT monitors soon became inexpensive and have been always easy to maintain, even more if compared with newer technologies. But in a competitive world, TVs and monitor had to changed over the years. Today many companies have halted their production of CRT monitor due to drastic decrease in revenue due to tighter energy standards and new competing technologies. Most companies have recorded a decrease of half of what CRT monitors used to bring. More companies are focusing on big demand of the new LCD monitors. It is a changing world and you have to change with it.
The biggest advantage of the CRT is that it is cheaper to manufacture which enables the poor countries to afford such a product the another, still unmatched, other advantages are the capacity for brightness, the color precision (CRTs still provide richer color in a fuller variety than most LCDs, here they will have a lasting niche market), a rapid refresh rate (important for fast changing graphics), an increased viewing angle (CRT provides the same brightness and color from a variety of different viewing angles), multiple resolutions and a lower purchase price.
Some negative points of CRT monitors is that they are power hungry (most was wasted as heat) and take more material to construct, they tend to be heavy and large. The CRT screen also lacked the newer technologies, glare from the surroundings could cause reflection, resulting in a poor quality for viewing.

### History of the CRT

This type of monitor was possible due to a German scientist named Karl Ferdinand Braun that in 1897 invented the first cathode ray tube. Braun introduced a CRT with a fluorescent screen, known as the cathode ray oscilloscope - an oscilloscope is an electronic display device containing a cathode ray tube (CRT), used to produce visible patterns that are the graphical representations of electrical signals. The screen would emit a visible light when struck by a beam of electrons.
A Russian scientist, named Boris Rosing, in 1907 used a CRT in the receiver of a television system. Rosing also transmitted crude geometrical patterns onto the television screen and was the first inventor to do so using a CRT. The first practical signal generating tubes were invented by Vladimir K. Zworykin and Philo T. Farnsworth.
Only in the 1940’s were the first CRT produced in the form of Televisions. Even though it was developed over hundred years ago, scientists have improved its picture quality over time. But it still runs on the same basic principles. Today the way a CRT tube works seems very simple and is used still in most TV screens and, in lowering numbers, as PC monitor.

## LCD

LCD or liquid crystal display screens are the newest and sharpest screens. Even though the use of LCD screens have been around for a long time, the technology has only been recently incorporated into the use of both televisions and computer monitors. The LCD screen uses rare characteristics that make it much more appealing than conventional CRT monitors. One of the key characteristics of LCD screens are the size advantage compared to a conventional CRT screen, a LCD screen does not employ the use of a cathode ray. But instead layers of filters and glass which polarize light and project onto liquid crystals which reveal sharp quality and excellent detail of the picture. Another interesting aspect of LCD screens is that there is almost no reflection of light from the surroundings into the screen.

##### Other Advantages of the LCD Monitors

* Brightness- the LCD monitor has a brightness of 250 to 300 nits
* No flicker- there is no flicker on a LCD, because it has a constant source of light over the whole screen
* Power consumption- consumes less power than the CRT, approximately one-third
* Ergonomics- the dimensions and the weight of the LCD permit it to consume less space. Example: mounting it on a wall
* Low emissions- LCDs cause no electromagnetic interference
Disadvantages of the LCD Monitor
* Blurry images outside native resolution
* Motion blur on fast moving images
* Some models have reduced color clarity Touch screen tablets are compact and user-friendly.

## Plasma Displays

Plasma displays are a type of flat-panel display. They have a comparable look to LCD displays and also use layered technology. However, instead of using liquid crystals like the LCD, plasma displays utilize a layer of gas between two glass plates. In plasma displays a phosphor-coated screen is used. Each pixel in the display is comprised of three cells encompassing the primary colors of visible light. Electronic charges are applied to make the gas atoms light up the phosphors to generate the image on the screen. In general, plasma displays tend to have a better contrast ratio, wider viewing angles, and less motion blur compared to LCD screens. On the other hand, plasmas are apt to use up greater electricity and older generation displays were more susceptible to screen burn-in and image retention.

## Touch Screens

A touch screen is monitor-like peripheral that allows a user to input information into a computer without using a mouse or keyboard. Just like its name- you simply touch the screen to make a selection. Touch screens are found in a variety of places: personal computers, tablets, self-checkouts, ATMs, cell phones and even some cars. Touch screens are generally compact and can be stored in various places. Some are mounted on walls, held up by brackets or built into countertops. There are disadvantages to touch screens for people with certain disabilities. People who are blind or have limited mobility may not be able to full access and use a touch screen to the same level as others.

## Electronic Paper

Have you seen the Amazon Kindle or Sony E-Reader? If you have, you’ve noticed that the screen looks almost exactly like a printed sheet of paper. That’s because these devices use electronic paper (e-paper) for their display. An electronic paper display uses a technology called electrophoretics that was developed by E Ink Corporation. The technology uses tiny charged white and black ink particles to simulate the look of paper. An applied voltage pulls either the white or black beads to the top of the screen, while the opposite beads fall to the bottom, thus giving the contrasting look of the words versus background on the screen. The technology requires much less power than other flat panel display technologies because there is no back-light needed and no power required to maintain the display, only to change the display. Devices using this technology are much easier to read in direct sunlight as well.

## OLEDs

Organic light emitting diode (OLED) a type of flat-panel display that may one day replace LCD technology. OLED displays use layers of organic material which emits light when electric current is applied. OLEDs are more energy efficient than LCDs because they don’t use backlighting which also lengthens the battery life of portable devices. Other advantages of OLEDs is that they are thinner than LCDs and have a wider viewing angle, so the display is visible from all angles. Another advantage of OLEDs is that they support new technologies such as flexible OLED (FOLED) in which the display is built on a flexible surface, allowing is to roll up when the device is not in use, and transparent OLED (TOLED) where the part of the display that doesn’t have an image is totally transparent. This could open up possibilities such as the use of displays on windows, auto windshields, and other transparent items.

## Digital Vs Analog

Analog and digital signals rely on two very different ways of translation. Analog is initially a digital signal that becomes translated by a graphics card into an analog signal which is then used for the display of the monitor. However the problem in this process is that quality and definition becomes “lost” in the translation from digital to analog, resulting in less sharpness and depth. Now a digital signal when properly connected to a DVI or digital video interface allows the digital signal to be directed right to monitor with no translation. DVI provides a high-speed digital interface through Transition Minimized Differential Signaling (TMDS). A transmitter on the video adapter transfers digital data to a receiver in the monitor. TMDS accepts the signal from the video adapter, determines the resolution and refresh rate that the monitor is using, and spreads the signal out over the available bandwidth to optimize the data transfer from computer to monitor. This results in a higher quality picture that appears more crisp and clean.
* ↑ Information found in Chapter 3 of Understanding Computers: Today and Tomorrow, 13th Edition by Deborah Morley and Charles S. Parker.