CS488 - Introduction to Computer Graphics - Lecture 2
Comments and Questions
- Combination to graphics lab.
- News group: uw.cs.cs488.
- Location of TAs: DC2303.
- Class cancelled: May 18, 2007.
- Existence of personal CS488 web pages.
Output Devices
Main device from the beginning was the colour cathode ray tube (CRT)
CRT
Main components
- Electron beam
- Focussing and acceleration electrodes
- Beam steering electrodes
- Phosphor
Operational principle -- Persistence of vision
- Visual persistence time: 30 milliseconds.
- Television - 30 frames per second
- Movies - 24 frames per second
Types of CRT
- Vector, aka calligraphic
- Raster -- operational principles
- Finite resolution of vision
- 30 cycles per degree
- 60 pixels per degree, aka 3600 pixels per radian
- at 72 cm viewing distance, 5 pixels per millimeter
- Scan pattern
- Getting pixels out of memory
- Colour raster -- operational principles
- Three colour primaries ==> three frame buffers
- Shadowmask technology
Benefits of CRT
- Very inexpensive
- Good resolution
- Easy colour calibration
- High contrast
- Good field of view
- Comet-free motion
- Adjustable focus
Drawbacks of CRT
- Heavy and big
- Power hungry
- High voltage
- Dim
LCD
Key components
- Back light
- Programmable filters -- one per colour primary per pixel
- Each filter a cell of analogue (!!) DRAM
- with liquid crystal (LC) between the plates of the capacitor
- LC rotates polarization depending on the electric field
- polarization-selective filters do the rest
Advantages
- small
- light
- not as power hungry as CRT
Disadvantages - most of these are back light problems
- directional view
- back light consumes power
- not very bright
- poor extinction
- hard to calibrate colour
Others of the past
- Plasma displays
- LC projectors
Others of the future
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