CSC103 How Computers Work

Notes 6

1. Video Displays

2. • Raster display (vs. vector)
   • VRAM (video RAM), Frame Buffer: e.g., 24 bits of RGB color per pixel
   • Video Controller; DAC
   • CRT
     • Electron gun: control-accel-focus-deflect
     • Phosphors: Persistence: ~10 microsec
     • => 60/sec x 10 microsec = 6 ms
   • Color: 3 guns
   • Refresh rate: 60 Hz
   • Fusion frequency
3. LCD
   • Light polarization; demo?
   • Nematic molecules
     
   • Active-matrix display
   • Flat Panel displays
4. Plasma
   • Gas bubbles, coated with phosphors.
   • Current causes plasma inside specific bubbles to radiate.
   • Ultraviolet rays causes phosphor coating glow.
5. DLP Projectors
   • Spinning color wheel
   • Millions of tiny, tilting mirrors

6. Scanners

7. • Photocell
     • silicon insulates
     • phosphorus: "extra" loose electron
     • boron: missing electron
     • photon of light: kicks extra into hole
     • result: little electric current.
   • Scanner operation
     • light captured by head,
     • bounced through mirrors onto photocell row, RGB filtered
     • converted into image, one row at a time

8. Digital Camera

9. • Charge Coupled Device: CCD
   • how the charges are moved off the chip
   • colors?
   
   • Filter the light.
     • one method: three sensor arrays
     • another: rotate filters quickly onto one sensor array
     • cheaper: checkboard color filter array
     • more green than red & blue because our eyes are more sensitive to green
   • LCD screen to preview results
   • image stored on flash memory

10. Dismantling a PC

    • preparation