Module 11- Section 2-narrated

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Module 11- Section 2:

Video Displays Module 11- Section 2 1

Display Devices :

The primary output device of a computer is the monitor. Today, the most commonly used type of monitor is the flat panel or LCD monitor. LCDs quickly replaced CRT monitors as soon as the price came down! Display Devices 2

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CRT stands for Cathode Ray Tube. LCD stands for Liquid Crystal Display. The two main components of the Video Subsystem are: The monitor The video adapter 3

CRT Monitor:

CRT Monitor CRT- Cathode Ray Tube Same as a picture tube on an old-style TV Main Components: Electron Gun Deflection Plates Phosphorus Coating Shadow Mask

CRT Monitor Safety:

CRT Monitor Safety Typically, monitors are replaced or sent out for servicing. High voltage capacitors inside the monitor are dangerous. NEVER wear an ESD device while working on a monitor

General Video Terms:

General Video Terms Pixel : smallest picture element (sometimes called a pel) Pixel Pitch: the distance between adjacent pixels, the smaller the distance the better the image.

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Vertical Refresh Rate : number of times image is scanned onto screen per second The refresh rate is measured in Hz (cycles per second). The refresh rate can be set in Display Properties. The faster the refresh rate, the better the response time. In CRT monitors, if the refresh rate is too low the image will flicker.

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Non-interlaced : a monitor whose electron beam scans consecutive rows Interlaced : monitor’s electron beam scans first odd rows then even, causes screen flicker (avoid)

Resolution- general:

Resolution- general Resolution: defines the number of pixels displayed horizontally and vertically. H x V 640 x 480 or 800 x 600 (for example) 1024 x 768

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Resolution is set from within the operating system. IN Win XP: Control Panel>Display from Display Properties select the Settings tab An Alternate way to get to Display Properties: Right-click the Desktop select Properties, then when the Display Properties opens, select the Settings tab

Win 7:

Win 7 12

Win 7:

Win 7 13

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A major difference between CRT monitors and LCD monitors is that LCD monitors have a “native resolution” and CRTs do not. The native resolution is based on the position of the liquid crystals on the panel. Two LCD panels that have the same size may have different native resolutions.

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The position of pixels are fixed on LCD panel. Common “ native resolution ” for an LCD panel would be XGA which is 1024 x 768 or SXGA+ which is 1400 x 1050. Changing resolution on an LCD panel causes a type of distortion known as scaling.

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To prevent the problem of scaling: Use the native resolution setting of the monitor Or choose a resolution that has the same aspect ratio (minimizes scaling effect) The aspect ratio describes the proportion of the images width to height. 4:3 is standard (square) 16:9 is wide screen.

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Higher resolution leads to smaller images May need to select large icons to view Desktop icons (For Win XP: Display Properties>Effects tab check Use Large Icons)

Vista/Win7 – resize icons:

Vista/Win7 – resize icons 19

Video Resolution:

Video resolution may also be called display modes. The A+ Certification exam expects you to know these display modes that apply to LCD panels : (but I don’t) XGA, SXGA+, UXGS, WUXGA Video Resolution 20

LCD Panels:

The main component of the LCD panel is the liquid crystal. Thin film transistors (TFT) control pixel elements. Each pixel has three colors (RGB) which are also called subpixels. Each pixel is controlled by one transistor. LCD Panels 21

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Liquid crystals respond to electrical signals and change structure to allow more or less light through Filters and alignment determine color that is displayed

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The liquid crystal elements of each pixel are arranged so that in their “normal” state the light coming through the passive filter is blocked. Thus, a blocked pixel produces a dark spot on the screen.

Flat Panel Monitors:

Flat Panel Monitors

Backlighting :

Backlighting on an LCD panel is used to brighten the display. Two methods of backlighting: CCFL: cold cathode fluorescent light LED: light emitting diode Backlighting 26

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LED Display: An LED display is an LCD display that uses LED backlighting as opposed to fluorescent backlighting LED backlighting offers a better contrast ratio and is more energy efficient. 27

More Flat Panel Terms:

More Flat Panel Terms Screen Size: A 15.1” LCD panel = 17” CRT Contrast ratio: Max and min values for brightness CRT: 500:1 (typical) LCD: 250:1 (minimum)

Terms (cont):

Terms (cont) Viewing Angle: Angle at which contrast ratio drops to 10:1 Good viewing angles are 120 degrees or more Response Time: max time for image to change Typical is 20 – 30 ms May cause “smudging” on fast action video

LCD Specifications::

LCD Specifications: Native Resolution Response Time (LOWER is better) Contrast Ratio (higher is better) Viewing Angle (higher is better)

Advantages of LCD Over CRT:

Advantages of LCD Over CRT No flicker Better Focus Conserves Power Size and Weight Takes up less room Many have built in speakers

Disadvantages of LCD over CRT:

Disadvantages of LCD over CRT Viewing angle Contrast Response Time Lack of flexibility setting resolution

Other Types of Monitors:

OLED: organic light emitting diode: a layer of thin organic compound which emits light in response to an electric current. The main advantage of the OLED is that is has a must higher contrast ratio than the LCD display. Other Types of Monitors 33

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Plasma: The central element in a plasma display is a gas that has many free-floating negatively charged ions that light up in response to an electric current (think of a neon sign). The gases used in a plasma display are xenon and neon. The main advantage of plasma over LCD is that it can be used to formulate a very large, thin screen. 34

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A disadvantage of plasma is that when used with still images it can “burn in” the image. 35

Video Expansion Slots:

Video Expansion Slots Common: AGP (on older machines) PCI Express (PCIe x16- standard today) PCI (on older machines- becoming hard to find) This is the end of section 2 of Module 11.

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