Computer Graphics
CSE 5280 Course


Physical Input Devices

I. Tablet
II. Mouse
III. Trackball
IV. Joystick
V. Touch Panel
VI. Light Pen




Function keys are the most common form of choice devices. Other choice devices include buttons on a mouse or puck. Choice devices are used to enter commands or select menu options.

Speech or Voice Recognition Systems

Conversa Web is a voice-enabled Web browser that lets you travel anywhere on the Internet without relying on a mouse or keyboard

Display Technologies

Cathode Ray Tube (CRT)

The most important component of the monitor is the Cathode Ray Tube (CRT) or picture tube. A CRT essentially an oddly-shaped, sealed glass bottle with no air inside. It begins with a slim neck and tapers outward until it forms a large base. The base is the monitor’s ‘screen’ and is coated on the inside with a matrix of thousands of tiny phosphor dots

See: History

Shadow Mask Characteristics

A shadow mask is a thin metal plate located in front of the phosphor layer on the picture tube surface, carefully aligned so that the electron beams for Red Green and Blue hit only one type of phosphor dot. Allow each gun to irradiate only one color of phosphor.

Delta pattern

Trinitron vs. Traditional Shadow Mask Technologies

The Trinitron technology uses an aperture grille. This grille, designed with long, unbroken slits, allows more light and color to reach the screen, resulting in purer and more colorful images. The Shadow Mask uses a mesh-like, darker screen that creates a color shift ("doming") distortion and prevents color purity. Trinitron tubes lay their colored phosphors down in uninterrupted vertical stripes. See figures below.
Aperture Grille (Trinitron)


Currently the most popular alternative to the CRT is the Liquid Crystal Display (LCD). LCDs are organic molecules that, in the absence of external forces, tend to align themselves in crystalline structures. But, when an external force is applied they will rearrange themselves as if they were a liquid. Some liquid crystals respond to heat (i.e. mood rings), others respond to electromagnetic forces.

When LCDs are used as optical (light) modulators they are actually changing polarization rather than transparency (at least this is true for the most popular type of LCD called Super-twisted Nematic Liquid crystals). In their unexcited or crystalline state the LCDs rotate the polarization of light by 90 degrees. In the presence of an electric field, LCDs behave like a liquid and align the small electrostatic charges of the molecules with the impinging E field.

See: LCD vs. CRT Reference

New Display Technologies