Chapter 4 Display Devices Flashcards by Rida Shaikh

Video Display Types

Ch. 4- pg.199

CRT, Liquid Crystal Display (LCD), LED Displays, Plasma, OLED, Projection systems

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CRT Displays

Ch.4- pg.199-200

Has a device called an electron gun that shoots a beam of electrons toward the backside of the monitor screen.
Color CRT guns use three guns (for red green and blue)
Back of monitor screen is coated with a special chemical (phosphors).
Beam of electrons scans from left to right (as we face it)
A screen (shadow mask) has holes spaced and angled.
Glow of the phosphors decays quickly

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Dot Pitch (CRT Displays)

Ch.4- pg.200

The measurement between the same spot in two vertically adjacent trios. (it’s the height of the trio added to the distance between the closest extremes of it and the next trio above or below it.
- Expressed in millimeters or dots per pinch it tells you how “sharp” the image can be, (the lower the measurement in mm the more dots per inch)

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Resolution (CRT Displays)

Ch.4- pg.200

Measures how many pixels are used to draw the screen

The higher the resolution the more information can be displayed on the screen. The objects or text displayed at a higher resolution appear smaller and might be harder to see
Resolution indicates how many rows and columns of pixels are used to draw the screen
- Example: 1024x768= 786,432 ( 1024 Across(columns) and 768 down (rows))

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Liquid Crystal Displays (LCD)

Ch.4- pg.201

Was made for portable computers
First application of LCD was the LCD watch
As the elements got smaller the detail of the patterns became greater
LCD are now on both laptops and desktops
External LCD is available in either analog or digital interfaces

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Active-Matrix (LCD)

Ch.4- pg.201-202

Made up of several independent LCD pixels, with a transistor at each pixel location
the transistor activates 2 opposing electrodes that align the pixels crystals and alter the passage of light at that location to produce hundreds or thousands of shades
Very crisp, does not need constant refreshing
Requires lots power

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Passive-Matrix (LCD)

Ch.4- pg.202

Doesn’t have a dedicated transistor for each pixel or sub-pixel but instead a matrix of conductive traces
To change the color of a pixel a signal is sent to it using a x- and y- coordinate traces

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Dual Scan (LCD)

Ch.4- pg.202

Variation of the passive matrix display

- Each half is refreshed separately leading to increased quality

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LED Displays

Ch.4- pg.203

LED displays are LCD panels with light emitting diodes (LEDs) as a light source instead of the fluorescent light blubs.
- For laptops with LED Displays, there is no need to change the DC power to the AC power

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Plasma Displays

Ch.4 - pg.203-204

Plasma- a cloud of ionized (charged particles)

the electrical imbalance is used to create light from the changes in energy levels as they achieve balance
Plasma Display panels (PDPs) do this by putting a gas, like neon in a sealed chamber with vaporized mercury and placing electrodes in front and behind the chamber.
Refresh rate is 600Hz
PDP produce a deeper black than LCDs

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OLED Displays

Ch.4- pg.204-206

Organic light emitting diodes (OLED)

they are self-contained cells that use the same principle to create light as …
OLED displays and supply the light source

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PMOLED ( Passive-Matrix OLED)

Ch.4- pg.205

Displays can not be made smaller because of tern limitations, such as needing to gang up the electrodes for the OLED

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AMOLED ( Active-Matrix OLED)

Ch.4- pg.205-206

Better quality than PMOLED, but need more electrodes

- Two developments in the AMOLED created the Super AMOLED and Super AMOLED Plus

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Projection Systems

Ch.4- pg.206

Can be thought to be a condensed video display units with a lighting system that projects the VDU’s image to a flat surface for group viewing

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Rear Projection (Projection Systems)

Ch.4- pg.206

A projector built into a cabinet behind a screen on to which the image is projected in reverse so that the people in the front can view it correctly
Ex: TV, Home theater units

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Brightness (Projection Systems)

Ch.4- pg.206-207

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Measures in lumens (lm). Lumen is the unit of measure for the total amount of visible light based only by the human eye
60W light bulb produces about 800lm
lux- a derivative of lumen measuring how much the projector lights up the surface on which it is focused

Adjusting Display Settings

Ch.4- pg.209

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Important Terms:

Refresh Rate
Resolution
Multiple displays
Degauss

Refresh Rate (Adjusting Display Settings)

Ch.4- pg.209

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Is the vertical scan frequency and specifies how many times in one second the scanning beam of electrons redraws the screen in CRTs
Measured in Hertz
The refresh rate must be supported by your graphics adaptor and your monitor