1.2 Compare & contrast the display components of mobile devices Flashcards
2 common types of displays used in mobile devices?
- LCD
- OLED
Meaning of LCD?
Liquid Crystal Display
Meaning of IPS?
In-Plane Switching
Meaning of TN?
Twisted Nematic
Meaning of VA?
Vertical Alignment
Meaning of OLED?
Organic Light-Emitting Diode
What do LCD pixels consist of?
Subpixels with their own transistor to control its intensity
This creates the display’s color range
Meaning of TFT?
Thin Film Transistor
3 main types of LCD TFT technology?
TFT technology is a type of LCD technology that uses thin-film transistors to improve image quality and performance
- TN
- IPS
- VA
How do TN TFTs work?
Uses crystals that twist or untwist
It twists/untwists in response to the voltage level
Advantage of TN TFTs?
Faster response times
What does fast response times help reduce?
Ghosting & motions trails in high frame rate input
What is refresh rate?
Speed at which the whole image is redrawn
What is refresh rate measured in?
Hertz (Hz)
What should the refresh rate be a multiple of?
Video frame rate
i.e. if a vid has a framerate of 30fps, its ideal for the display to have a refresh rate of 60Hz (30fps * 2 = 60Hz). This synchronization helps ensure smoother & more consistent motion on the screen, reducing issues like stuttering or tearing
What is response time?
The time taken for a pixel to change color
what is response time measured in?
Milliseconds (ms)
How do IPS TFTs work?
Using crystals that rotate
Main benefit of IPS TFTs?
Better color reproduction at wider viewing angles
What type of LCD is best for gaming & graphics/design work?
IPS
How do VA TFTs work?
Using crystals that tilt
Main benefits of VA TFTs?
Has a wide color gamut & best contrast-ratio performance
i.e. where a high-end IPS panel might support a 1200:1 contrast ratio, a VA panel would be 2000:1 or 3000:1
What is contrast ratio?
Difference in shade between black & white pixels
Main drawback of VA LCDs?
Viewing angles are worse than IPS & response times are worse than TN
This makes a VA panel more prone to motion blur & ghosting
What are modern TFT LCDs illuminated by?
LED backlight
What type of LED arrangement is used on most phone/tablet screens?
Edge lighting arrangement
The LEDs are positioned at the screen’s edges, with a diffuser ensuring uniform brightness.
What backlight did older laptops use?
CCFL
Meaning of CCFL?
Cold Cathode Fluorescent
What power do CCFL bulbs require?
AC power
Why do CCFL-backlit laptops need an inverter?
To convert DC power to AC power
How do OLEDs work?
Each pixel has its own LED, requiring no backlight
4 benefits of OLED displays?
- Better contrast ratios
- Thinner
- Lighter
- Consumes less power
Which display type can be curved to different shapes?
OLED
2 main drawbacks for OLEDs?
- Lower brightness than LCDs
- More susceptible to burn-in
What is a burn-in?
When LEDs retain an image due to displaying a static image for many hours
Purpose of digitizers/touchscreens?
Converts analog input to digital instructions
What kind of digitizers do modern mobile devices use?
Capacitive digitizers
What do capacitive digitizers support?
Multitouch
gestures like “pinching” the screen can be interpreted as events & responded to by software in a particular way
What does airplane mode do?
Disables some/all wireless features
Cellular data, Wi-Fi, GPS, Bluetooth, & NFC
On some devices, some services can be selectively re-enabled while still in airplane mode
