Display devices and TOUCH SCREEN TECHNOLOGY

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  • Display devices and TOUCH SCREEN TECHNOLOGY

    1. 1. Display Devices And Touch Screen TechnologyPresented By:- Abhishek Pal
    2. 2. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT(Cathode Ray Tube) Displays 2. LED Displays 3. LCD Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    3. 3. Introduction of Display Devices• A display device is an output device for presentation of information in visual or tactical form• One of the earliest electronic displays is the cathode ray tube (CRT), which was made commercial in 1922• Since then electronic display devices based on various principles are developed.
    4. 4. Types of Display devices• Active display devices are based on luminescence. • Luminescence • Photo-luminescence • Cathodo-luminescence • Electro-luminescence• Passive display devices reflect or modulate light.
    5. 5. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LED Displays 3. LCD Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    6. 6. CRT (Cathode Ray Tube) Displays• The Cathode Ray Tube (CRT) was invented by German physicist Karl Ferdinand Braun in 1897.• Cathode Ray Tube (CRT) contains four basic parts: • Electron gun, • Evacuated glass • Focusing and accelerating systems, • Deflecting systems,
    7. 7. CRT Displays Principles• Display principle • Raster Scan Display Principle  In this system the screen is scan in vertically and horizontally • Random Scan Display Principle  Here the electron gun of CRT illuminates point and/or straight lines in any order• The frequency at which a picture is redrawn on the screen is referred to as the “Refresh Rate”.• The maximum number of points that can be displayed on a CRT is referred to as the “Resolution”.
    8. 8. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LED Displays 3. LCD Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    9. 9. LED Display• An LED display is a flat panel display, which uses light-emitting diodes as a video display.• A cluster of red, green, and blue diodes is driven together to form a full-color pixel, usually square in shape.• Matrix of diodes is arranged to form pixels and picture definition is stored in refresh buffer.• Information is read from refresh buffer and converted into voltage levels that are provided to diodes, thus producing light patterns in the display.
    10. 10. Techniques UsedThree techniques are used in making LED displays:-1. Edge-Led :- It is done around the rim by using a special diffusion panel to spread the light evenly behind the screen.2. Full-array Led :- The are arranged behind the screen and their brightness are not controlled individually.3. Dynamic „Local Dimming‟ Led:- This type of back-lightning allows dimming of specific areas of darkness on the screen.
    11. 11. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LED Displays 3. LCD Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    12. 12. LCD Displays• George H. Heilmeier invented LCD in 1964• The heart of all liquid crystal displays (LCDs) is a liquid crystal itself.• Produces pictures by passing polarized light through liquid- crystal material.• There are three basic types of liquid crystals which are termed 1. Nematic 2. Chiral 3. Smetic
    13. 13. Basic Design of LCD Display
    14. 14. Working Principle Off State1. Surrounding light is polarized on the upper plate.2. Light moves along with liquid crystals and twisted at right angle3. Molecules and lights are parallel to the lower analyzer.4. Light passes through the plate and thus screen appear transparent.
    15. 15. Working Principle ON State1. Surrounding light is polarized on the upper plate.2. Light moves along with liquid crystals which moves straight along the electric field.3. Molecules and lights are perpendicular to the lower analyzer.4. Light cannot pass through.5. Screen appear dark.
    16. 16. Comparison CRT LCD LEDPOWER High power is consumes 50-70% consumes 30-40%CONSUMPTION consumed less energy as of less power than compared to CRT LCDPICTURE High contrast ratio Poor picture Superior than CRTQUALITY quality than LED and LCDCOST Low cost High cost Very high cost (~2 times of CRT) (~4 times of CRT)
    17. 17. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    18. 18. TOUCH SCREEN TECHNOLOGY
    19. 19. Introduction• First described by E.A Johnson in his work on capacitive touchscreen in 1967.• A Touchscreen is basically a input device so it should be combined with a display device and a computer.• A Touchscreen basically includes:- 1. Touch Screen Sensor 2. Controller 3. Software Driver
    20. 20. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    21. 21. ComponentsTouch Screen Sensor• A touch screen sensor is a clear glass panel with a touch responsive surface.• The sensor generally has an electrical current or signal going through it.• Voltage change determine the point of touch. 21
    22. 22. Components Controller• The controller connects between the touch sensor and the PC.• The controller determines what type of connection you will need on the PC.• Controllers are available that work with DVD players and other devices. 22
    23. 23. Components Software Driver• The driver allows the touchscreen and computer to work together.• Most touch screen drivers today are a mouse-emulation type driver.• This allows the touchscreen to work with existing software. 23
    24. 24. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    25. 25. Introduction• In 1971, the first "touch sensor" was developed by Doctor Sam Hurst• A touch screen is an Electronic Visual Display.• The touch screen is one of the easiest to use and most intuitive of all PC interfaces• This touch screen works on the principle of voltage dividers. 25
    26. 26. Resistive TechnologyV=Voltage (Volts) A difference in electrical potentialI=Current (Amps) A flow of electric charge which (by convention) flows from a higher to a lower voltage potentialR=Resistance (Ohms) Resists the flow of electric currentI = V/R Current flow proportional to Voltage and inversely proportional to resistance
    27. 27. Potential Divider VI RR R1 R2 VI R1 R2V V1 V2V2 IR2 VV2 R2 R1 R2 R2V2 V R1 R2
    28. 28. Potentiometer V2 is proportional to the position of the arrow. At the top V2=V and at the bottom V2=0
    29. 29. Resistive Touch Sensor• The sensor panel consists of several layers, the most important of which are two thin, transparent layers separated by thin space.• Top screen has coating on the underside surface..• Voltage is applied to one layer and sensed by the other.• Generally a 4-wire technology is used.
    30. 30. 4-Wire Technology• It consists of 4 resistances arranged so indicate X and Y Cartesian axis.• When the screen is touched the conductive coating on the coversheet connects with the coating on the glass.• The controller reads the X and Y positions.
    31. 31. Calculation of Touch PositionCalculation of Y-Position X-Position
    32. 32. 5-Wire and 8-Wire Technology
    33. 33. Advantages & Disadvantages ADVANTAGES• Force activated so can use finger even with a glove, stylus or any other (non sharp) prodding device.• Tolerates dust/dirt, rain and insects. DISADVANTAGES• Conductive coating reduces display brightness.• Continual flexing of outer layer causes microscopic cracks so affects linearity of resistance (other processes can overcome this)
    34. 34. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    35. 35. Capacitive Touch Screen• It is an all glass touch screen with a transparent metallic conductive coating.• It is made up of all-glass material with transparent conductive coating.• The transparent conductor used is Indium Tin Oxide.
    36. 36. Working principle
    37. 37. Working principle• The basic idea is the consideration of human body to be conducting.• Whenever the screen is touched a small amount of current is attracted by the finger causing change in the capacitance.• These are of 2 types:-1. Surface Capacitive2. Projected Capacitive
    38. 38. Surface Capacitive Touchscreen• It consists of uniform conductive coating on one side of the glass panel.• Electrodes around the panel edge evenly distribute a low voltage around the conducting layer.
    39. 39. Surface Capacitive Touchscreen
    40. 40. Projected Capacitive Touchscreen• It have front and protective glass to provide additional optical and strength enhancements options.• Its middle layer consists of laminated sensor grid of micro-fine wires.
    41. 41. Projected Capacitive Touchscreen • The screen is divided into small grids of unit cell. • Whenever a touch occurs, the finger disturbs the electric field projected by sensor by conducting electric current. • The location is calculated by checking the capacitance at each point on the grid regularly.
    42. 42. Advantages & Disadvantages ADVANTAGES• It has high resolution and Image clarity.• Immune to surface contaminants like dirt, grease or moisture.• Durable and resistant to scratches. DISADVANTAGES• Will work only when touched by a conductive device.• Some capacitive touches can have erratic behavior when touched by more than one input.
    43. 43. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    44. 44. SAW Touchscreen Technology • It have a glass overlay with transmitting and receiving piezoelectric transducers. • Transmitting transducer, converts the electric signal into ultrasonic waves within the glass. • These waves are reflected across the screen by reflectors.
    45. 45. Working Principle
    46. 46. Advantages and Disadvantages ADVANTAGES• It provides superior image clarity, resolution, and higher light transmission.• It has the highest durability factor. DISADVANTAGES• It must be touched only by finger, gloved hand, or soft-tip stylus.• It is not completely sealable, can be affected by large amounts of dirt, dust, and / or water in the environment.
    47. 47. Outline• Introduction of Display Devices• Types of Display Devices 1. CRT Displays 2. LCD Displays 3. LED Displays• Introduction of Touch Screen Technology• Components of Touch Screen• Types of Touch Screen Technology 1. Resistive Touchscreen 2. Capacitive Touchscreen 3. Saw Touchscreen 4. Infrared Touchscreen
    48. 48. Infrared Touchscreen Technology• In 1983, the computer manufacturing company, Hewlett- Packard introduced the HP-150.• The HP-150 had a built in grid of infrared beams across the front of the monitor which detected finger movements.
    49. 49. Working Principle
    50. 50. Advantages & Disadvantages ADVANTAGES• It can detect essentially any input including a finger, gloved finger, stylus or pen.• It have better durability and optical clarity. DISADVANTAGE• It is sensitive to dirt/dust that can interfere with the IR beams.• It suffer from parallax in curved surfaces and accidental press.
    51. 51. References

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