Chapter 4 Display Devices Flashcards
Video Display Types
Ch. 4- pg.199
CRT, Liquid Crystal Display (LCD), LED Displays, Plasma, OLED, Projection systems
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
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)
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))
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
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
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
Dual Scan (LCD)
Ch.4- pg.202
- Variation of the passive matrix display
- Each half is refreshed separately leading to increased quality
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
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
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
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
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
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
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
