2 - Display Technology

ucla | CS 174A | 2024-01-11 19:06

Table of Contents

Output Devices

Cathode Ray Tube (CRT)

  • electrons strike a Phosphor coating and emits light
  • electron gun launches electrons
  • electron direction controlled by deflection plates to target a direction on the Phosphor coating
  • random-scan, calligraphic, or vector CRT displays - just draw lines cant fill
  • refresh rate of 60 hz - 85 hz
  • issue - cant rasterize images - cant create solid shapes

    Raster CRTs

  • framebuffer depth:
    • 1 bit = b/w image either filled or not
    • 8 bit = grayscale with 256 possible shades of b/w
    • 8 bit per RGB = 16M colors
    • 12 bits per color = HD
  • 3 colored electron guns shoot into a raster mask that creates pixels as triads
  • guns scan line by line of “pixels” so frame buffer holds the LxWxD, here it is 3 bit color
  • refreshing is done at least 30 hz and line by line, so it can produce rasterized images, BUT now has aliasing due to atomic pixel size
  • interlaced displays (most commercial) - signals sent to so that each refresh does every odd/even lines then interlace between every 2 refreshes
  • single vs double buffering
    • to prevent read write clash from reading and writing to the same pixel in the buffer, implement double buffers and swap after reading

      Display Memory Calculations

  • $n\times m$ pixel resolution
  • $r$ Hz refresh rate
  • $b$ bits/pixel (all colors so RGB is 3 bytes=24 bits per pixel)
  • Memory space per second: \(= \frac{n\cdot m\cdot r\cdot b}8\space \text{bytes}\)
  • Non-interlaced Memory Read Time: \(=\frac1{n\cdot m\cdot r}\space\text{s/pixel}\)
  • interlaced is \(\frac2{n\cdot m\cdot r}\space\text{s/pixel}\)

    Other displays

  • Flat screens
    • raster displays: active matrix with transistors at grid points
    • LEDs
    • LCDs: polarization of liquid crystals
    • OLED
    • Plasma: energize gases to glow
  • VR
    • stereoscopic
    • foveated rendering: HD where focused, low res where not
  • anamorphic LED displays
  • holographic real time displays
  • spherical displays