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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