Input/Output DevicesGraphical Interface Systems

Dr. M. Al-Mulhem

Feb. 1, 2008

Display Devices

Display Devices• Vector display

– Draws only lines– Also known as random scan

• Raster display– Discrete grid of elements (frame buffers pixels)– Shapes drawn by setting the “right” elements– Frame buffer scanned (one line at a time) to preserve image– on CRT

• LCD – liquid crystal display– Polarizing light– Crystals react to current

Vector vs. Raster

• Vector – Easy to draw lines– Can display only lines– Refresh time depends on scene complexity– Old fashioned – Very uncommon today

• Raster– Hard to draw smooth lines– Displays a discrete approximation of any shape– Refresh the entire frame buffer– Used practically everywhere

Terminology

• Pixel: Picture element– Smallest accessible element in a picture– Usually rectangular or circular

• Aspect Ratio: – Ratio between physical dimensions of a pixel

(not necessarily 1)

• Dynamic Range: – Ratio between minimal and maximal light

intensity emitted by display pixel.

Terminology (cont).

• Resolution: The maximum number of pixels that can be displayed without overlap on the screen.

• 1024×768 pixels

• Screen Space: A discrete 2D Cartesian

coordinate system of the screen pixels.• Object Space: The 3D Cartesian

coordinate system of the universe.

Hardcopy Devices

• Plotter

• Dot Matrix Printer:

• Laser Printer:

Color Printing Technologies

• Ink Jet– Sprays microscopic dots of ink through small holes to form dots

on paper.

• Thermal Wax– Creates colors by melting and bonding color wax dots onto

special paper.

• Dye Sublimation– Creates continuous-tone by heating dyes until they turn into gas

(sublimate), that fuses into the paper.

• Film Recorder– A camera in front of a designated B&W CRT. RGB channels are

sent one at a time through an appropriate filter.

Standard Input Devices

• Keyboard– For alphanumeric input.

• Mouse/Trackball– Provides relative

movement information.

2D Input Devices

• Joystick– Provides relative movement

information.

• Digitizer/Tablet– Provides absolute position information.

• Touch Screen– A CRT screen that can sense pressure

on its surface.

• Light Pen– Synchronized with the CRT scan, it can

locate a position on screen.

3D Input Devices

• Dataglove– Sensors to detect hand and finger

motions– Used to grasp a virtual objec.t

• Head mounted Display– Used to interact with the

environment.

• Space Ball– Position and orientation is measured

by the pressure applied to the ball.

Image Capture

• Digital Cameras– High resolutions.

• Video Camera– Low resolution.

• Scanner– High resolution.

More Image Capture Devices

• Thermal imaging– Non visible images

• Ultrasound– High frequency sound waves

are converted to form an image.

3D Scanners

• CT / MRI– 3D Imaging

• 3D Range Scanner– Geometry and color texture

digitizer