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Graphics hardware
Output devices
Input devices
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Overview
CPU
Hardcopy
DisplayDisplay
processorSystemmemory
Scanner
Inputdevices
LAN
Image capture
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Display devices
Raster displays. CRT. Random (vector) displays LCD Plasma
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Cathode Ray Tube - CRT
Refresh rate Resolution Bandwidth
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Color CRT
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Phosphors spectrum
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Random (vector) display Draws only lines Currently obsolete in computers Advantages:
― Fast refresh for simple scenes― Easy line drawing― No memory requirements
Similar displays are in oscilloscopes
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LCD technology - basics
Randomly polarized light
Crystal molecule
Vertical polarizerAligning glass
Horizontal polarizer
(Color) mirror
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LCD technology - basics
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LCD, reflective vs. backlit Reflective LCD require external light
(watches) Backlit LCD are lit with fluorescent
lamps (laptops)
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Passive LCD
Composed of horizontal and vertical wires A dark spot at (x1,y1) requires –V at x1 and +V at y1. What happens when we want black dots at (x1,y1) and
(x2,y2)? Points are selected in succession (one pixel at a time)
Vertical polarizer
Vertical wires
Liquid
Horizontal wires
Horizontal polarizer
Mirror
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Active LCD
Transistor attached to every grid point: Attached capacitors are able to hold the charge Fast response time Better grey level accuracy To display color filters are added
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LCD
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LCD vs. CRT comparison table CRTLCD
PowerFairExcellent
Screen sizeExcellentFair
DepthPoorExcellent
WeightPoorExcellent
BrightnessExcellentGood
ContrastExcellentFair
ColorExcellentGood-Excellent
Viewing angleExcellentPoor
Response timeExcellentGood
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Plasma Two panels of glass that hold tiny cells of neon and
xenon Pros
― Fast response― No need to refresh― Great color gamut― Bright― Wide viewing angle
Cons― Price― Power consumption― Contrast
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Hardcopy devices - terms
Dot size Inter-dot spacing Resolution – number of distinguishable lines per inch Colors at a point
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Hardcopy devices Plotter
― Moves pen across the surface― Vector graphics― Later plotters are raster― Used for technical and CAD style plots― High resolution over very large paper sizes
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Hardcopy devices
Dot matrix printer― Print head with 7 to 24 pins (piece of wire)― Each pin can be fired to strike a ribbon against the paper
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Hardcopy devices Ink jet printer
― Spray microscopic dots of ink through small holes to form dots on paper. 4 colors (CMYK) in standard and up to 8 in photo printer are used.
Thermal wax― Creates colors by attaching wax paper to material and
melting it. Used for special materials (shirts, plastic,…). Dye sublimation
― Creates continuous tones by heating dye until they turn into gas (sublimate) and fuses into the paper.
― Larger color gamut― High cost per image
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Hardcopy devices – Laser printer
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Hardcopy devices – Laser printer The drum is positively charged by corona wire Laser discharges points Printer coats the drum with positively charged
toner powder Paper is given strong negative charge to pull the
toner from the drum and then discharged Finally the paper passes through the fuser (a pair
of heated rollers) that melts the powder Color – 4 times through the process
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Standard input devices
Keyboard― Alphanumeric
Mouse― Relative movement
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2-D input devices
Joystick― Controlled by potentiometer ― Provides relative movement
Digitizer / Tablet― Controlled by electromagnetic or sonar sensing― Provides absolute location
Touch screen― Different technologies that detect pressure / contact
with the screen surface Light pen
― Synchronized with CRT, it can locate position on the screen
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3D input device
Wired glove Head mounted display Space ball Haptic devices
― Force / vibration feedback
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Image capture
Digital cameras― Capture by CCD― High resolution, up to 10Mp
Video cameras― CCD― Lower resolution
Scanner― Digitizes a hardcopy image with CCD― High resolution
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Image capture Ultrasound
― High frequency waves― Measures distance and intensity of the
return way― Standard ultrasound is 2D― 3D image is built from several 2D images
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Thermal imaging Non visible by human eye IR range mapped to visible range
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3D scanners
CT / MRI― 3D imaging ― Radiation on tissue
3D range scanner― Non contact― Geometry and color texture digitizer― Uses laser-light triangulation