Chapter 19 Display Technologies (220-901)

Contrast Ratio

Contrast ratio is the difference between the darkest and lightest spots that the monitor can display.

Lumens

The brightness of a projector is measured in lumens. A lumen is the amount of light given off by a light source from a certain angle that is perceived by the human eye. The greater the lumen rating, the higher the brightness. The best lumen rating depends on the size of the room and the amount of light in the room.

Display Adapters

The display adapter, or video card, handles the video chores within computing devices processing info from the CPU and sending it to the display. The display adapter contains its own CPU and RAM.

Adjustments

All monitors obviously have an off/on switch. They also have a menu setting that lets you adjust the contrast, brightness, etc.

LCD Monitors

Almost every computing device today uses liquid crystal display (LCD) as the primary output component. LCDs work very differently than CRT.

Response Rate

An LCD panel's response rate is the amount of time it takes for all of the sub-pixels on the panel to go from pure black to pure white and back again. Manufacturers measure response rate in milliseconds, with lower being better. A typical lower end or older LCD has a response rate of 20-25 ms. In recent years, you can find many monitors with now 2-4 ms.

Software

Configuring your video software is usually a two step process. First you need to load drivers for the video card. Then you go to open the Control Panel and go to the Display applet (7/8/8.1/10) or Personalization applet (Vista) to make your adjustments.

Installing and Configuring Video

During the physical installation of a video card, watch out for three things: long cards, the proximity of the nearest expansion card, and the presence of power connectors. Some high-end video cards simply won't fit in certain cases or will block access to needed MOBO connections such as the SATA sockets. There is no fix for this other than changing the video card, MOBO, or case. High-end video cards often come with a video card power connector.

Adapters and Converters

If you have one port that is different than the other (example an HDMI TV with a DVI Video card) you can use a special adapter for making the connection. This is for any port that is copper wire based and I think it works the same for fiber. However, you cannot convert an HDMI to LC because they are two different connection types. One is copper based and one is light based. So in that case you would need a bridge.

For Standard Monitors

Most standard monitors use DVI or VGA. Many Apple Mac desktop models use a DisplayPort connection for connecting to a monitor. Dell offers support for DisplayPort as well. More recent Apple offerings, such as the Mac Pro, MacBook Pro, and MacBook Air, use a Thunderbolt connection for monitors. Thunderbolt offers astounding versatility especially with a multi monitor setup.

LCD Monitors with CCFL Backlights

One on the greatest challenges to LCD power stems from the fact that the backlights need AC power while the electronics need DC power. Most LCD's use a cold cathode fluorescent lamp (CCFL) technology, popular for its low power use, even brightness, and long life. CCFLs need AC power to operate, but given that the transformer converts the incoming AC power to DC, each CCFL backlight needs a device called an inverter to convert DC power back into AC.

PCI

PCI was a big change for the PC industry. The original PCI ran at 33 MHz and was 32 bits. PCI was also plug in play, meaning that you could plug in a device to it without having to install any drivers. If the OS or board has the drivers, it will install it for you.

PCIe

PCIe was developed to replace PCI and AGP. This slot is incredibly fast and can handle an enormous amount of bandwidth. All PCIe video cards use the x16 connector.

Lamps

The bane of every projector is the lamp. Lamps work hard in your projector, as they must generate a lot of light. As a result, they generate quite a bit of heat, and all projectors come with a fan to keep the lamp from overheating. When you turn off a projector, the fan continues to run until the lamp is fully cooled. Lamps are also quite expensive and can be a few hundred dollars.

Integrated GPUs

A lot of current MOBOs have have integrated GPUs or are ready for a CPU with an integrated GPU. The MOBO GPU can be a separate chip attached to the MOBO or can be built into the Northbridge chip. Intel has long integrated the Intel Graphics Media Accelerator (GMA) into its chipsets. With an integrated GPU, the CPU circuitry is getting pretty crowded. A single AMD APU chip, for example, integrates two to four CPU cores, a memory controller that support DDR3 for system memory, cache memory, and a GPU that can handle advanced 3-D graphics.

Throw

A projectors throw is the size of the image at a certain distance from the screen. All projectors have a recommended minimum and maximum throw distance that you need to take into consideration.

Connections

A very common connection for monitors is VGA-15. This is a D shaped connector that has 3 rows of 5 pins. VGA is a analog connection though. Controlling a CRT requires an analog signal from the video card, meaning the signal rises and falls in waves like a series of Ss on their side. LCDs and computers on the other hand, use digital signals, on or off, one or zero. The info on the video card is digital. Video cards include a special chip called the random access memory digital-to-analog converter (RAMDAC). The RAMDAC takes the digital signal from the video card and turns it into an analog signal for the analog CRT. RAMDACs make sense for analog CRT monitors. If you want to plug an LCD monitor into a regular video card, however, you need circuitry on the LCD monitor to convert the signal from analog to digital. Many LCD monitors use exactly this process. These are called analog LCD monitors. The monitor isn't really analog; it's digital, but it takes a standard VGA input. New LCDs and video cards, support fully digital connections, the most common is DVI. DVI has three different connectors that look alike. DVI-D (digital), DVI-A(Analog) and the DVD-A/D or DVI-I (interchangeable) accepts either analog or digital. DVI-D and DVI-I come in two varieties, single link and dual link. Single link has a smaller throughput than dual link.

AGP

AGP was a dedicated slot for video cards. It had a direct connection to the Northbridge.

LCD Resolution

All LCD monitors have a native resolution, such as 1920 x 1080, that enables them to display the sharpest picture possible. Pixels are fixed and you cannot run an LCD monitor at a resolution higher than the native one. You also can't run at a lower than native resolution without severely degrading image quality. Always set the LCD at native resolution.

Drivers

Just like any other piece of hardware, your video card needs a driver to function. Video card drivers install pretty much the same way as all of the other drivers: either the driver is already built into Windows or you must use the installation media that comes with the card. Video card makers are constantly updating their drivers. Odds are good that any video card more than a few months old has at least one driver update. If possible, check the manufacturer's Web site and use the driver located there if there is one. If the Web site doesn't offer a driver, it is usually best to use installation media. Always avoid using a built in Windows driver because it tends to be the most dated.

How LCDs Work

LCD technology has been around for a long time but it is now becoming very popular for flat-screen computer monitors and televisions. It can provide a much better, brighter image than the old CRT (Cathode Ray Tube) monitors and TVs. Here is a very basic summary of how LCD works. There is a set of two transparent panels with a liquid crystal solution between them. Light is shined from behind the panels. Each crystal either allows light to pass through or blocks the light. The configuration of the crystals forms the image. There's a little more to it than that... The two transparent panels are polarized, which means they will only pass light waves in one plane. These two polarized panels at 90 to each other so that light filtered from one plane cannot get through the other panel because it only lets light through in a plane at 90 to the first plane. So the panel appears to be "black" (or at least very dark). However, when electricity is applied to one of the segments of liquid crystals (segments are switched on and off to form the images you see on the screen). The crystals line up in such a way as to make the light turn through 90 in between the two panels. So now the light "TWISTS" through the panels and is visible on the other side. Does having a "Super-Twist" display mean more to you now? Actually, LCD images are inferior to CRT images, colour uniformity, image sharpness and viewing angle are poor compared to a CRT and fast moving images appear blurred because the crystals can't quite keep up and react quickly enough. They are getting better, but will never beat the image quality of a CRT. But obviously are smaller and lighter, so it's worth having one anyway.

LED Monitors

Manufacturers also use several types of light-emitting diode (LED) light for backlighting, either directly illuminating pixels from behind or flooding the panel from the edges of the bezel. Manufacturers often to refer to LED as a display type but all it is a form of backlighting for LCD monitors. Using LEDs for backlighting reduces the thickness of the panels and reduces the overall electricity usage. LEDs don't need AC power, so there is no inverter to get involved in lighting the panel. Many smaller devices, such as smartphones and tablets, use LED backlights to save battery use.

Plasma Display

Plasma display panels (PDPs) are a popular technology for displaying movies, competing with LCD screens for the flat-panel space. They offer a wider viewing angle and richer picture than the typical LCD and cost less. They weigh alot more and produce more electricity compared to LCDs though. Unfortunately, plasma TVs have two issues that make them a bad choice for PC use. First is burn in- the tendency for a screen to leave a "ghost" image even after the image is off the screen. Plasma TV makers have virtually eliminated burn-in, but even the latest plasma displays are subject to burn-in when used as PC displays. The second issue is overscan, a problem that can affect LCD-based TVs as well. Overscan is when the TV blows up the image, cropping off the edges of the picture. TVs do this for historical reasons, but the side effect is that when used with a PC, things like your taskbar get cut off. I advise against using a plasma display as a monitor.

Projectors

Projectors enable you to display computer images to an audience. There are two ways to project an image on a screen: rearview and front view. Rearview projectors shoot an image onto a screen from the rear. Rearview projectors are self enclosed and were once very popular for televisions, but are virtually unheard of in the PC world. A frontview project shoots the image out the front and counts on you to put a screen in front at the proper distance. Frontview projectors connected to PCs running Microsoft PowerPoint have been the corner stone of every meeting almost everywhere.

Projector Technologies

Projectors that connect to PCs have been in existence for almost as long as PCs themselves. The first generation of projectors used CRTs. Each color used a separate CRT that projected the image onto a screen. These have long since been abandoned. Given that light shines through an LCD panel, LCD projectors are a natural fit for front projection. LCD projectors are light and expensive compared to CRTs but the lack of image quality. LCD projectors have a specific native resolution.

Resolution

Resolution is the amount of pixels on the screen. Your resolution is represented by the amount of pixels on the horizontal and vertical row. For example, 1920x1080 is HD resolution (1920 is the pixels on the horizontal row and 1080 is the pixels on the vertical row).

Graphics Processor

The graphics processor handles all of the heavy lifting of taking commands from the CPU and translating them into coordinating and color information that the monitor understands and displays. Most techs today refer to the device that processes video as graphics processing unit (GPU). Many companies make video cards but the main companies are Intel, AMD, NVIDIA.

Motherboard Slot

The oldest expansion slot, PCI, is used today only to support extra monitors on older systems. Slightly newer, but still old, is AGP. Every current video card plugs into a PCIe slot on MOBO. Finally, many motherboards have have the display adapter built-in.

Refresh Rate

The refresh rate for an LCD monitor is described using numbers similar to those used to describe the refresh rate for a CRT monitor, such as 60 Hz. The refresh rate for an LCD monitor refers to how often a screen can change or update completely.

Brightness

The strength of an LCD monitor's backlights determines the brightness of the monitor. The brightness is measured in nits. LCD panels vary from 100 nits on the low end up to over 1000 nits or more on the high end. Average LCD panels are around 300 nits, which most people would consider excellent brightness.

LCD Components

The typical LCD monitor is composed of three main components: the LCD panel, the backlight(s), and the inverters. The LCD panel creates the image, the backlights illuminate the image so you can see it, and the inverters send power to the backlights.

Connector Types and Associated Cables

There are many types of connector types on video cards, plus variations within those types. Standard monitors connect through one of six connectors: -VGA -DVI -DB-15 -DisplayPort -Thunderbolt -HDMI Video cards offer other connector types for connecting to things like television set, camcorders, and other multimedia devices: -RCA -BNC -Mini-DIN

For Multimedia Devices

Video cards can have one or more standard connections plus non-standard connections for hooking the PC to a multimedia device, such as a television, DVD or Blue-ray Disc player, or video camera. The earliest type of connector commonly found is the mini-DIN for attaching an S-video cable. This provides decent quality video output or, is some cases, input. You will sometimes find a proprietary round connector that supports S-video and a proprietary dongle that adds support for video through either composite connections. The 220-901 exam refer to the mini-DIN used with S-video as miniDIN6. Most techs refer to the port as an S-video port. A composite connector provides a video signal through a single cable that plugs into a standard RCA jack, whereas a component adapter provides a split signal, red, green, and blue. The best connections for outputting to television are the High Definition Multimedia Interface (HDMI) connectors. Some devices offer HDMI output directly, while other video cards support HDMI through a special adapter. HDMI comes in three sizes: Standard, Mini, and Micro. Plus there is the E connector used exclusively for automobile video systems. Standard HDMI is what you will find on video cards and television. Most contemporary tablets use Mini-HDMI.

Video Memory

Video memory (GDDR) is crucial to the operation of a PC. It is probably the hardest working set of electronics on the PC. Most of the graphics rendering and processing is handled on the card by the video processor chip rather than by the CPU. GDDR3 SDRAM: Similar to DDR2 but runs at faster speeds GDDR4 SDRAM: Upgrade of GDDR3;faster clock GDDR5 SDRAM: Successor to GDDR4; double the input/output rate of GDDR4