LED, LCD and Touchscreens

Technology of the new Era

Group Members

Sheeraz Reg. # 15-CP-54 Hamza Irfan Reg. # 15-CP-58 Sikandar Rafique Reg. # 15-CP-70

LED’sLight Emitting Diodes

Content's

What are LED’s? History Working of LED Applications of LED Advantages of LED

What are LED’s?

LED’s are semi-conductors which emits monochromatic light when operated on forward biased direction.

LED’s convert electrical energy into light energy.

LED

History The first visible-spectrum (red) LED was developed in

1962 by Nick Holonyak Jr., while working at General Electric Company.

M. George Craford invented the first yellow LED and improved the brightness of red and red-orange LEDs by a factor of ten in 1972.

In 1976, T. P. Pearsall created the first high-brightness, high-efficiency LEDs for optical fiber telecommunications.

Working of LED LEDs create light by electroluminescence in

a semiconductor material. LED’s are basically P-N junction being operating in

forward biased direction. E.P.E is converted into E.M.E With each recombination of a negative and positive

charge a quantum of E.M.E is emitted in the form of a photon of light

Working of LED’s

Structure of LED

Applications of LED

Sensor applications Mobile applications Signal applications Illuminations

Sensor applications

Medical instrumentation Bar Code readers Color and Money sensors Optical switches Fiber Optic Communication

Bar code reader

Optical fiber

Color mark sensor

Mobile applications

Mobile phones PDA’s Tablet’s LED Flat screens Laptops

Mobile Phone

LED TV

Laptop

Signal applications

Traffic lights Rails Tower lights Runway lights Neon signs

Tower lightsTraffic Signs

Runway lights

Illuminations

Retail displays Flashlights Bulb replacements Emergency lights(exit signs)

Flashlight

LED Bulbs

Emergency signs

Advantages of LED

They're tiny and relatively inexpensive. They're easy to control electronically. They last virtually forever. That makes them brilliant

for traffic signals. The typical LED requires only 30-60 milliwatts to

operate. They are reliable that’s why they are soldered

directly I electric circuits.

Queries are openly accepted

Liquid Crystal Displays

Prepared & Presented by:Hamza Irfan {15-CP-58}

What is LCD?

• A Liquid Crystal Display is a slim, flat-panel mostly used to display text, pictures, videos, etc.

• This display is commonly used in laptops.

• Also available in desktop versions.

• Problems faced in CRT are solved by LCD.

What is LCD?

Fig. 1.0 LCD MonitorFig. 1.1 Calculator LCD

Brief History

• The history of LCDs starts with the discovery of liquid crystals in 1888 by Friedrich Reinitzer.

• Further works on liquid crystals were performed by Otto Lehmann in 1904.

Brief History• Later on, in 1963, Richard Williams along with George Heilmeier,

suggested using liquid crystals for making a display device.

• Dynamic Scattering method DSM was used to create first operational LCD by RCA (1968).

Brief History

• First LCD using Twisted Nematics (TN) was produced in 1971.

Fig. 4.0 Twisted Nematics

Development of LCDs

• In 1970s, first commercial LCD came into existence, and this technology was first used in quartz watch and in calculator displays.

• 1990s color LCDs were used in digital cameras and computer monitors.

Fig. 5.0 Digital Camera LCD

Development of LCDs

• 2000s Larger LCDs were used as home theatre. Full HD 1080p displays were produced.

Did you know?The largest LCD panel today is 110”.

Overview

• It is a type of light modulating display device. • Doesn’t directly emit light to create visualizations.

• Modifies the transmission of light to represent images.

• Rapidly gained popularity.

Did you know?Nearly 33% of all TVs sold in North America were LCDs

Working of LCD

Types of LCDs

• LCDs are characterized into two types:Passive Matrix LCDActive Matrix LCD

Fig.10.0 Passive Matrix vs. Active Matrix driving of LCD Monitors

Passive Matrix LCD

• Pixels are activated indirectly.

• Not so much expensive.

• Uses grids of Indium Tin Oxide (ITO).

• Pixels don’t refresh quickly.

• Animation might be blurry.

• Has a narrow viewing angle.

Active Matrix LCD

• Each pixel is activated directly.

• More expensive than passive ones.

• Uses thin film transistors.

• Animation is sharp, crisp and clean.

• Pixels have 4 transistors.

• Used in computer displays.

Advantages of LCDs

• Brightness - Produces very bright images due to high peak intensity.

• Emissions - Produces considerably lower fields than CRTs do.

• Distortions - No geometric distortion at default resolution.

• Power Consumption - Energy efficient and consumes 1/3 the power of a CRT.

• Size - Takes less desk space than CRTs do.

• Screen shape - Completely flat screen.

Disadvantages of LCDs

• Aspect ratio - The aspect ratio and resolution are fixed.

• Black level - Doesn’t show good result for black and dark gray colors.

• Contrast - Lower contrast than CRTs.

• Cost - Considerably more expensive in purchase than CRTs.

• Viewing angle - Viewing angle has restrictions. For clear vision, one must sit in front of the screen.

• Sensitivity - Can be more fragile than CRTs.

Queries are openly accepted!

Thankyou

Technology & Applications TOUCH SCREENS

Points to Discuss

Introduction History Components Working of Touch screen Types Comparison Applications

Introduction

A touch screen is a display that can detect the presence and location of a touch within the display area.

Interact

Fig:1.1Touch Screen

History

In 1965 ,the first touch screen was a capacitive touch screen developed by E.A. Johnson at the Royal Radar Establishment, Malvern, UK.

In 1971 ,a resistive touchscreen was developed by American inventor Samuel Hurst(founder of Elographics).

E.A Johnson Samuel Hurst

Components

A basic touch screen has three main components

Touch sensorControllerSoftware driver

Fig:2.2:Touch Screen

Fig:2.3:Controller

Fig:2.1:Driver

Working Of Touch Screen

Fig:3.1:Working Of Touch Screen

Types of Technology

Resistive Touch Screen Capacitive Touch Screen Surface Acoustic Wave Touchscreen Infrared Touch Screen Optical Touch Screen

Resistive Touch Screen

Fig:4.1:Resistive Touch Screen

1. Pet Film2. Top Circuit Layer3. ITO Conductive coating4. Space Dot5. ITO Conductive coating 6. Bottom circuit Layer7. Glass

Capacitive Touch Screen

Fig:5.1:Capacitive Touch Screen

1. Dust Cover Glass LENSE2. One optical adhesive3. ITO layer X-axis4. One optical adhesive5. ITO layer Y-axis6. Display

Surface Acoustic Wave Touchscreen

Fig:6.1:Surface Acoustic Wave Touchscreen

1. Transducers emit sound waves along sides2. Sound wave reflector3. Sensor4. Touch absorbs some energy from sound waves5. Controller

Optical/Infrared Touch Screen

Fig:7.1:Infrared Touch Screen

Optical-touch systems use an array of infrared (IR)light-emitting diodes (LEDs) on two adjacent edges of a display, with photo sensors placed on the two opposite edges to analyze the system and determine a touch event.

Optical Imaging

Fig:8.1:Optical Imaging

ComparisonTechnology Capacitive SAW Infrared Resistive

Transparence Very good >92%

Very good >92%

Very good >92%

75%~85%

Resolution Good Good Limited due tospacing of IRsensors

good

SurfaceContaminants/durability

Resistant tomoisture andother surfacecontaminants

Adversely affected bymoisture orSurfaceContaminants

Potential forFalse

activationor dead zonesFrom SurfaceContaminants

Unaffected by Surfacecontaminants.Polyester topsheet is easilyscratched

Display size 8.4"-21" 10.4"-30" 10.4"-60" up to 19"

Touch method Human touch finger, glovedhand or soft

tip

Can use any pointing

device

Can use any pointing

device

Table:1.1:Comparison between Capacitive ,SAW ,Infrared & Resistive

Applications

Tourism displays, Trade show display Stores, Restaurants, ATMs, Airline ticket terminals

and Transportation hubs. Digital jukeboxes, Computerized gaming, Student

Registration systems, Multimedia software , Scientific applications etc.

… Any Question

…THANK YOU