Monitors

(Georgia Tech 2003)

 The Cathode Ray Tube

A few TVs in use today rely on a device known as the cathode ray tube, or CRT, to display their images. LCDs and plasma displays are other common technologies. It is even possible to make a television screen out of thousands of ordinary 60-wattlight bulbs! You may have seen something like this at an outdoor event like a football game. Let's start with the CRT, however.

The terms anode and cathodeare used in electronics as synonyms for positive and negative terminals. For example, you could refer to the positive terminal of a battery as the anode and the negative terminal as the cathode.

In a cathode ray tube, the "cathode" is a heated filament (not unlike the filament in a normal light bulb). The heated filament is in a vacuum created inside a glass "tube." The "ray" is a stream of electrons that naturally pour off a heated cathode into the vacuum.

Electrons are negative. The anode is positive, so it attracts the electrons pouring off the cathode. In a TV's cathode ray tube, the stream of electrons is focused by a focusing anode into a tight beam and then accelerated by an accelerating anode. This tight, high-speed beam of electrons flies through the vacuum in the tube and hits the flat screen at the other end of the tube. This screen is coated with phosphor, which glows when struck by the beam.

(Brain, M. (n.d.))

You probably use items containing an LCD (liquid crystal display) every day. They are all around us -- in laptop computers, digital clocksand watches, microwave ovens, CD players and many other electronic devices. LCDs are common because they offer some real advantages over other display technologies. They are thinner and lighter and draw much less power than cathode ray tubes (CRTs), for example.

But just what are these things called liquid crystals? The name "liquid crystal" sounds like a contradiction. We think of a crystal as a solid material like quartz, usually as hard as rock, and a liquid is obviously different. How could any material combine the two?

We learned in school that there are three common states of matter: solid, liquid or gaseous. Solids act the way they do because their molecules always maintain their orientation and stay in the same position with respect to one another. The molecules in liquids are just the opposite: They can change their orientation and move anywhere in the liquid. But there are some substances that can exist in an odd state that is sort of like a liquid and sort of like a solid. When they are in this state, their molecules tend to maintain their orientation, like the molecules in a solid, but also move around to different positions, like the molecules in a liquid. This means that liquid crystals are neither a solid nor a liquid. That's how they ended up with their seemingly contradictory name.

So, do liquid crystals act like solids or liquids or something else? It turns out that liquid crystals are closer to a liquid state than a solid. It takes a fair amount of heat to change a suitable substance from a solid into a liquid crystal, and it only takes a little more heat to turn that same liquid crystal into a real liquid. This explains why liquid crystals are very sensitive to temperature and why they are used to make thermometers and mood rings. It also explains why a laptop computer display may act funny in cold weather or during a hot day at the beach.

(James (n.d.))

LG 42” 1080p LCD HDTV

Televisions were available since around the 1920’s. They started out in black and white colour. Now they’ve moved to HD full colour. TV’s have been used for many things. We use them for many things: from watching the latest news, to the recent movie that just came out, to playing video games.

To describe how far TV’s have gone, we’ll use the example of a LG 42” 1080p LCD HDTV. First of all, the screen has a Liquid Crystal Display (better know was LCD). This allows for a very energy efficient and compact TV. Furthermore the picture it gives has no geometric distortion. Second 1080p gives you a high definition picture.

The future of Television is 3D TV. We’ll be able to watch all are every day shows in 3D without glasses. Also we’ll be able to attach systems to it with such clear picture it looks real to the touch, and almost smell. What I like about these new TV’s is the clarity of the picture. Making you feel right in the action. For example, when watching a game you see the people and the puck moving at exact speed. You can make your own judgment on offside calls.

(James (n.d.))

Refresh rate is for Cathode-Ray tubes (CRT) monitors.

Response time is for Liquid Crystal Display (LCD) monitors. 

With LCD only the altered Pixels are changed, not the entire display like with CRT.

VGA Timings

The following table lists timing values for several popular resolutions.(martin.hinner.info)

Monitor Resolution

Resolution is the number of pixels the graphics card is describing the desktop with, expressed as a horizontal by vertical figure. Standard VGA resolution is 640×480 pixels. This was pretty much obsolete by the beginning of the new millennium, when the commonest CRT monitor resolutions were SVGA and XGA – 800×600 and 1024×768 pixels respectively.

Monitor Refresh Rate

Refresh rate, or vertical scanning frequency, is measured in Hertz (Hz) and represents the number of frames displayed on the screen per second. Too few, and the eye will notice the intervals in between and perceive a flickering display. It is generally accepted – including by standards bodies such as VESA – that a monitor requires a refresh rate of 75Hz or above for a flicker-free display. A computer’s graphics circuitry creates a signal based on the Windows desktop resolution and refresh rate. This signal is known as the horizontal scanning frequency, (HSF) and is measured in KHz. A multi-scanning or autoscan monitor is capable of locking on to any signal which lies between a minimum and maximum HSF. If the signal falls out of the monitor’s range, it will not be displayed.

Calculating Maximum Refresh Rate

Where VSF = vertical scanning frequency (refresh rate) and HSF = horizontal scanning frequency the formula for calculating a CRT monitor’s maximum refresh rate is:

VSF = HSF / number of horizontal lines x 0.95

So, a monitor with a horizontal scanning frequency of 96kHz at a resolution of 1280×1024 would have a maximum refresh rate of:

VSF = 96,000 / 1024 x 0.95 = 89Hz.

If the same monitor were set to a resolution of 1600×1200, its maximum refresh rate would be:

VSF = 96,000 / 1200 x 0.95 = 76Hz.

DVI Connectors

Using twisted pins on a 45 degree angle, DVI Single Link handles resolutions up to 1920x1080 at 60 Hz. DVI Dual Link display adapters are required for 2048x1536 and 2560x1600 monitors. See screen resolution.

(pctechguide.com 2015)

WHAT ARE SINGLE AND DUAL LINKS ?

The Digital formats are available in DVI-D Single-Link and Dual-Link as well as DVI-I Single-Link and Dual-Link format connectors. These DVI cables send information using a digital information format called TMDS (transition minimized differential signaling). Single link cables use one TMDS 165Mhz transmitter, while dual links use two. The dual link DVI pins effectively double the power of transmission and provide an increase of speed and signal quality; i.e. a DVI single link 60-Hz LCD can display a resolution of 1920 x 1200, while a DVI dual link can display a resolution of 2560 x 1600.

(datapro.net)

What is HDMI?

Technically speaking, HDMI (which stands for High Definition Multimedia Interface) is a global connectivity standard developed by a consortium of major electronics manufacturers including Hitachi, Panasonic, Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. HDMI establishes a "future-proof" foundation for the transmission of high-definition video and multichannel audio among a wide variety of audio, video and computer products. Today, more than 800 companies have adopted the HDMI standard and are building HDMI into their products.

For you, this means that there is a high-quality, single-cable, all-digital solution you can use to interconnect all the components of your home entertainment system, regardless of manufacturer. And because HDMI is a two-way platform, it also means that your individual components can "talk" to each other, exchanging critical information that allows optimizations and adjustments to be made automatically for easy, trouble-free operation of multiple components.

(Bestbuy 2015)

Video memory

Video memory is memory located on the video card, in some cases located on the motherboard, that is accessible by the video and computer processor. With more video memory, the video card and computer are capable of handling more complex graphics at a faster rate.

As can be seen in the above picture video memory is usually an IC that is integrated into the video card and not a removable memory module like the memory in your computer. Video card memory may be as low as 8MB on older video cards and up to several gigabytes on newer video cards.

(computerhope.com 2015)

Touch-screen monitors have become more and more commonplace as their price has steadily dropped over the past decade. There are three basic systems that are used to recognize a person's touch:

Resistive

Capacitive

Surface acoustic wave

The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot. The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse's movements into a click or a drag.

In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch-screen driver software. One advantage that the capacitive system has over the resistive system is that it transmits almost 90 percent of the light from the monitor, whereas the resistive system only transmits about 75 percent. This gives the capacitive system a much clearer picture than the resistive system.

On the monitor of a surface acoustic wave system, two transducers (one receiving and one sending) are placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflectors -- they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity).

Another area in which the systems differ is in which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object -- except hard and small objects like a pen tip.

(computer.howstuffowrks.com 2015)

Dual Monitors

With a single monitor, every time a new window is brought up on the screen, your eyes and brain need to reorient themselves. These seconds of mental processing can add up. In fact, The University of Utah determined that workers could save up to 2.5 hours per day when using larger (24”) or dual monitors[3]. That means in an 8.5-hour workday, your employer will benefit from over an extra day of productivity per week from you, while you’ll enjoy more screen real estate and easier working. It’s a win-win.

Consider having your email up on one screen and a document you are working on up on the other. Do you IM a lot with coworkers about projects? Try reserving a screen for chats so you can still check email simultaneously. Or try using one screen to pull up websites or other documents you need to refer to, eliminating the need to print out materials. Simply sweep the mouse and files move from one screen to the other, enabling maximum efficiency.

(viewsonic.com 2012)