Output Devices

Presented by - Chaitrali Ahire

Output devices translates information processed by the

computer into a form you can understand. Can you guess which of these devices are OUTPUT devices?

Output devices can be divided into two categories: SOFTCOPY output devices and HARDCOPY output devices.

SOFTCOPY HARDCOPY

Monitors (VDUs) Printers

Projectors

Speakers

Video Graphics Card

SOFTCOPY OUTPUT DEVICES

• Monitors – these are also called Visual Display Units (VDUs). There are two types of monitors. These are Cathode Ray Tube (CRT) and Flat Panel Displays.

visual display unit

• A VDU (Visual Displaying Unit) is the monitor that is used to display the output of the computer.

• It comprises the circuitry, display device and an enclosure.

• The VDU in modern monitors is a thin film transistor liquid crystal display thin panel, but the older monitors use a cathode ray tube that is as deep as the screen size.

Visual devices - VDUs

Visual Display Unit

(Monitor)(Screen)

Liquid Crystal Display(LCD)

Types of Visual Display Unit

Mainly there are 4 types of VDU’s as follows :-

• (CRT) Cathode Ray Tube • Plasma• (LCD) Liquid Crystal Display• (LED) Light Emitting Diode

1) Cathode Ray Tube

A cathode ray tube (CRT) is a specialized vacuum tube in which images are produced when an electron beam strikes a phosphorescent surface.

How CRTs work & display?

• When electricity is supplied to this, the filament heats up and a stream or "ray" of electrons pours off of it.

• The negatively charged electrons are attracted to positively charged "anodes" which focus the

particles into three narrow beams, accelerating them to strike a phosphor-coated display screen.

Flat Panel Display

• It refers to a class of video devices that have reduced volume, weight and power requirements compared to a CRT.

• Thinner than CRT’s.

1) PLASMA Display

• The basic idea behind the plasma technology is to illuminate tiny colored fluorescent lights to create image pixels.• Each pixel is made of three such fluorescent lights red, green and blue lights. • To create a wide range of colors, intensity of these lights is varied accordingly.

Plasma displays are manufactured by companies such as Panasonic, Fujitsu, and Pioneer.

Working of PLASMA monitor :-

2) LCD

• A Liquid Crystal Display (LCD) is a flat panel display that uses the light modulating properties of liquid crystals which do not emit light directly.

• Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters, perpendicular to each other.

• With no actual liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second.

Working of LCD monitor :-

4) LED•When light emitting diode is forward biased e- within device releasing energy in the form of photons .• This is called luminescence LED displays based on injection of it.

• Edge LED monitors

• Direct LED Monitors

Edge LED monitors have diodes placed all around the edge of the screen to light up the display.

This technique is very effective and gives each area of the screen its own diode, which can be on or off. Still using white light, the direct LED screens can produce massive contrast ratio's making the difference between the lights and the blacks appear almost perfect.

CRT

LEDLCD

PLASMA

Thank You