SPECIAL THANKS First of All I am greatly thanks to ALLAH Whose give me ability to courage and power to complete the presentation without blessing mercy and favor I am not able to do this work.

Topics Liquid Crystal Displays ( LCD ) Light Emitting Diode ( LED )

What’s Liquid Crystals (LC) intermediary substance between a liquid and solid state of matter. e.g. soapy water light passes through liquid crystal changes when it is stimulated by an electrical charge.

Introduction to Liquid Crystal Displays Consists of an array of tiny segments (called pixels) that can be manipulated to present information. Using polarization of lights to display objects. Use only ambient light to illuminate the display. Common wrist watch and pocket calculator to an advanced VGA computer screen

Operating Principle The parallel arrangement of liquid crystal molecules along grooves When coming into contact with grooved surface in a fixed direction, liquid crystal molecules line up parallel along the grooves.

Molecules movement . Operating Principle Offline (no voltage is applied) Along the upper plate : Point in direction 'a' Along the lower plate : Point in direction 'b‘ Forcing the liquid crystals into a twisted structural arrangement. (Resultant force)

Operating Principle Light movement Offline (no voltage is applied) Light travels through the spacing of the molecular arrangement. The light also "twists" as it passes through the twisted liquid crystals. Light bends 90 degrees as it follows the twist of the molecules. Polarized light pass through the analyzer (lower polarizer).

Operating Principle Molecules movement Online (voltage is applied) Liquid crystal molecules straighten out of their helix pattern Molecules rearrange themselves vertically (Along with the electric field) No twisting thoughout the movement Forcing the liquid crystals into a straight structural arrangement. (Electric force)

Advantages of LCD Technology Energy efficient, low-power Excellent contrast Lightweight and compact Sharp resolution Superior resolution Used in battery-powered electronics Uses a smaller pixelated format

Disadvantages of LCD Technology The color and contrast from various viewing angles is inconsistent Features poor black on dark imagery Pixel-based display may be stuck on screen Fixed resolution Newer technology costs more Imagery not as good with analog interface

Light Emitting Diode ( LED )

What is an LED? Light-emitting diode Semiconductor Has polarity

Negative electrons move one way and positive holes move the other way LED: How It Works When current flows across a diode Negative electrons move one way and positive holes move the other way

Therefore when a free electrons falls it losses energy LED: How It Works The wholes exist at a lower energy level than the free electrons Therefore when a free electrons falls it losses energy

LED: How It Works This energy is emitted in a form of a photon, which causes light The color of the light is determined by the fall of the electron and hence energy level of the photon

Inside a Light Emitting Diode Transparent Plastic Case Terminal Pins Diode

Kinds of LEDs

Benefits of LED Lighting Long Life Energy Efficiency Ecologically Friendly Durable Quality Design Flexibility Light Dispersement Low-Voltage

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