Display Technologies

What it is Collection of parts and software designed to put a picture on a screen Monitor shows you what is going on with software (and OS) Primary output device for PC Video card, or Display Adapter handles communication between CPU and monitor

Phosphor Coating on inside of tube CRT Monitors A LOT of high voltage, resist the urge to take it apart! Electron Beam Electron Guns (3) Shadow Mask Yoke Phosphor Coating on inside of tube

How it works Electron gun fires a beam of electrons Path of electrons is shaped by the yoke (bent) Electrons strike the phosphors and make them glow Phosphors have persistence so they continue to glow after electron beam stops

Refresh Electron beams sweep from left to right – across then down to next line Raster Line Horizontal Refresh Rate KHz Vertical Refresh Rate Hz

Adjustments Try not to do it; the manufacturer knows better than you do. The video card “pushes” the monitor – that’s where changes are made

Resolution Number of horizontal pixels by the number of vertical pixels 640x480 800x600

Aspect Ratio Ratio of horizontal to vertical pixels 4:3 for CRT and many LCD monitors 16:9 for wide-screen monitors (same as theaters use)

Dot Pitch One significant measure of value of monitor: more expensive = lower number Dot Pitch In millimeters Dot pitch of .28 or less gives a nice, sharp image. At .35 it seems like you can see the dots (TV image)

LCD (Passive) Monitors Light travels in waves (one definition) Liquid crystals tend to align with grooved surface or electric field. Aligned crystals will allow light to pass through (no electrical potential) Apply electrical potential and no light passes through This is digital, rather than analog of CRTs

LCD Pixels

Passive Matrix Wires in “Y” and “X” directions Voltage on wires allowed light to pass Slow response: “smeared” image Laptops for early years and watches today

Thin Film Transistor (TFT) Also called Active Matrix Vast improvement over Passive Matrix One, or more, transistors control each color dot Twisted nematic gives fair display for reasonable price – use 18 bits, not 24 In-Plane switching (IPS) gives true picture Brighter, better contrast, faster, more colors and wider viewing angle

LCD components LCD panel (what you see) Backlights (so you can see the display in low-light conditions) – cold cathode fluorescent lamp (CCFL) Inverters send power to the backlights (DC-AC) 3-row, 15-pin connector is analog and must go through a analog to digital converter; DVI and HDMI are digital

LED monitors Light-emitting diode Another form of backlighting Can be an array across the screen or around the edges Don’t need AC power, so no inverter(s)

Resolution LCDs have a native resolution – looks best there Mine is 1280x1024 @ 60 Hz (19”) Can run lower resolution, but picture sharpness suffers – even with edge-blurring (anti-aliasing) Object size does not “grow” quite as quickly as monitor size

Other Measures Contrast Ratio: Bright to dark 700:1 Brightness: 400 nits or 400cd/m2 Response time: 4 ms Refresh rate: 24Hz for movies, 60 Hz for monitors which leads to 120Hz monitors

Projectors Lumens = brightness of projected image Throw = size of image at a certain distance from projector Lamps get hot quickly, need a fan to cool them and are expensive to replace

Plasma Display PDP – Plasma Display Panel Wider viewing angle and richer picture than LCD panels Use a lot of electricity Suffered from “burn in” issues where image “ghosts” on the screen Overscan (picture larger than display) can cut off the taskbar Not a good choice for PC monitor

Monitor Size CRT’s are smaller (for same size) than LCDs Viewable image size 15.5” Screen Size CRT LCD Monitor size 17” 15” screen size

Graphics Processing Unit Connections CRTs only use analog, 15-pin connector LCDs can use either analog or digital connector – DVI-I Video cards use RAMDAC to convert digital to analog for display Graphics Processing Unit

Power Conservation Turn off the CRT to reduce power consumption or when you walk away Burn-in of image is a long lost art. Used to happen on older monitors. Typical CRT uses 120-200 watts; LCD’s use 40-75 watts

Adjustments On/Off switch Brightness and contrast buttons (CRT) Menu activate/select button for on-board menu system Seldom is there a “reset” button, so be careful

Video Cards Or Display Adapters Three parts: Video RAM, video processor circuitry and RAMDAC Early cards just shuffled BIOS bit-maps to the screen (put a dot here, and one there) Used small amounts of RAM 80 characters by 24 rows

Color Depth 16 colors = 4 bits 256 colors = 8 bits 64k colors = 16 bits 16.7 million colors = 24 bits VGA mode is 640x480 @ 16 colors

AGP (PCI – 32-bits at 33MHz) Accelerated Graphics Port Single slot, never two 66 MHz, 32-bits wide Uses strobing for 2x, 4x and 8x transfers on each clock cycle 21

On its own bus

Video RAM VRAM – Video RAM – allowed read/write at same time WRAM – Windows RAM – optimized for moving windows around – died quickly Replaced with DDR, DDR2, GDDR3 and GDDR4, GDDR5 SDRAM

Graphics Processor Can be done by CPU (for on-board graphics) but not efficient ATI and NVIDIA make most GPUs New GPUs come out often; a challenge to keep up with models More dollars = newer GPU CPU with GPU = Accelerated processing unit (APU)

PCIe x16 Serial communication 16 “lanes” or channels Replacement for PCI bus as cards become available (x1 and x4 variants) SLI – its either Scan Line Interleave or Scalable Link Interface – two video cards (matched set)

Display Port and HDMI Mac desktop models and some Dell Big brother is the Thunderbolt connector High Definition Multimedia Interface (HDMI) – video output like DP

Installation Read the install manual first, not later! Remove old drivers first. Reset system to VGA mode on existing card Install new drivers Install new card Finish driver installation Try to keep other cards away from video

Name tags Vista: Personalization 7 and later: Display and Personalization

Display Applet

Drivers Windows can crash and require a re-install of OS simply by installing a new video card and not uninstalling the old video drivers first. Go to Add/Remove Programs to uninstall video driver. (Step 1) Insert CD for new card and start driver installation. (Step 2) Stop system where directed and install card. (Step 3) Finish driver installation.

If the Card went bad Can’t get to Add/Remove programs. Have to install card to get working display. Start up in Safe Mode; you can delete drivers in this mode. Load drivers for new card.

Color Correction Also called color temperature Device that fits on monitor and looks at the display Graphic artists use these so they can set colors exactly.

3-D Games Started with sprites – still images of an object; multiple images used to create depth True 3-D uses vertices to define points on an object which are then “edged” with flat polygons Last step is to cover the edges with texture(s) Takes a lot of computing horsepower

3-D Video Cards Graphical Processing Units (GPU) to do the 3-D rendering tasks Lots of RAM to store textures We need standardized command sets to allow communication between game and video card: OpenGL for UNIX, then PC’s DirectX API (Application Programming Interface) from Microsoft

DirectX Supports Video, Sound, Network connections and Input devices Provides common interface for games – don’t have to write to specific video card Vista/7 wants DirectX 10, not 9.0c which most had in XP Dxdiag to determine version of DirectX and other stuff about DirectX 4

Troubleshooting Cards Video cards seldom fail, but might Often a driver issue – Windows cares about video card, but not monitor You can go to Programs and Features to delete video driver Try Safe Mode to see if problem “goes away” – then you know it is driver (or setting) Try another monitor – often a hassle, but well worth the time Check the settings for resolution, refresh & color

Troubleshooting CRTs Try another monitor, then get another monitor – don’t try to fix them, the dollars don’t work out Check the signal cable connections – loose cable will color the screen or miss colors Client with no video turned out to be failure to start up

And Now… Plasma Display Panels Digital Light Processing (DLP) Large screen sizes Miniature florescent lights – three per pixel Uses as much power as CRT First ones had bad habit of burning out Digital Light Processing (DLP) One mirror for each pixel Don’t know how they move, but they do