Touchscreen Technology

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Basic overview of different types of touchscreens

Basic overview of different types of touchscreens

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  • 2. RESISTIVE TOUCHSCREEN The two sheets are coated with resistive substance, usually a metal compound called Indium Tin Oxide (ITO). The ITO is thinly and uniformly sputtered onto both the glass and the PET (Polyethylene terephthalate) layer. Tiny bumps called spacer dots are then added to the glass side, on top of the resistive ITO coating, to keep the PET film from sagging, causing an accidental or false touch. When the PET film is pressed down, the two resistive surfaces meet. The position of this meeting (a touch) can be read by a touchscreen controller circuit.
  • 5. Advantages: • Most widely used touch technology • Can be activated by bare finger, gloved hand, or stylus • Low cost Disadvantages: • Top sheet is highly susceptible to scratches, cuts and cigarette burns • Layer is a flexing mechanical element coated with a conductive ceramic which wears with every flex • Transmission typically in 80% to 85% TOUCHSCREEN TECHNOLOGY
  • 6. SURFACE CAPACITIVE TOUCHSCREEN • Four multi-layer glass. • The two sides of the glass substrate are coated with uniform conductive ITO (indium tin oxide) coating. • The thickness of 0.0015 millimeter silicon dioxide hard coating are coated on the front side of ITO coating layer. • There are electrodes on the four corners for launching electric current. TOUCHSCREEN TECHNOLOGY
  • 7. WORKING PRINCIPLE Small amount of voltage is applied to the electrodes on the four corners. A human body is an electric conductor, so when you touch the screen with a finger, a slight amount of current is drawn, creating a voltage drop. The current respectively drifts to the electrodes on the four corners. Theoretically, the amount of current that drifts through the four electrodes should be proportional to the distance from the touch point to the four corners. The controller precisely calculates the proportion of the current passed through the four electrodes and figures out the X/Y coordinate of a touch point. TOUCHSCREEN TECHNOLOGY
  • 8. Advantages: • Can be used to register touch on a sensor surface through a glass window. • Capacitive touch screen withstand contaminants such as grease, dirt, water, running liquid, harsh chemicals and can be NEMAsealed. • The life expectancy is over 225 million mechanical touches. • Capacitive technology transmits around 90% percent of the light from the screen. • Life span of more than more than 50 million touches in one location. • Technology with fastest touch response time Disadvantages: • Limited to 1 resolvable touch point • Can only register the touch of ungloved fingers or tethered stylus on a sensors surface. • Sensitive for electromagnetic interference. • Severe scratch can affect operation within the damaged area TOUCHSCREEN TECHNOLOGY
  • 9. PROJECTED CAPACITIVE TOUCH: Projected Capacitive Touch (PCT) technology is a capacitive technology which permits more accurate and flexible operation, by etching the conductive layer. An XY array is formed either by etching a single layer to form a grid pattern of electrodes, or by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form the grid (comparable to the pixel grid found in many LCD displays). TOUCHSCREEN TECHNOLOGY
  • 10. WORKING PRINCIPLE Applying voltage to the array creates a grid of capacitors. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field. The capacitance change at every individual point on the grid can be measured to accurately determine the touch location. The use of a grid permits a higher resolution than resistive technology and also allows multi-touch operation. The greater resolution of PCT allows operation without direct contact, such that the conducting layers can be coated with further protective insulating layers, and operate even under screen protectors, or behind weather and vandal-proof glass. TOUCHSCREEN TECHNOLOGY
  • 11. Advantages: • Touch function operates through customer-installed materials, including vandal-resistant glass up to 18 mm thick. • Works outdoors-in rain, snow, ice, and dust. • True flat front surface possible with no bezel. • Works with fingers, gloved hands or conductive stylus. • Works even if glass is scratched or broken. Disadvantages: • More complex electronics and sensor construction when compared to other technologies • Does not have full stylus independence support TOUCHSCREEN TECHNOLOGY
  • 12. SURFACE ACOUSTIC WAVE With Surface Acoustic Wave (SAW,) piezoelectric transducers located at different positions of the screen are used to turn the waves of mechanical energy of a touch (vibration) into an electronic signal. The waves are spread across the screen by bouncing off reflector arrays along the edges of the overlay and are detected by two "receivers". The acoustic wave weakens when the user touches the glass with their finger, gloved hand or soft stylus. The coordinates are then determined by the controller circuitry that measures the time at which the amplitude declines. TOUCHSCREEN TECHNOLOGY
  • 13. WORKING: When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. When sound waves are transmitted across the surface of the display, the following sequence of events occurs: • Each wave is spread across the screen by bouncing off reflector arrays along the edges of the overlay. • Two receivers detect the waves. • When the user touches the glass surface, the user's finger absorbs some of the energy of the acoustic wave and the controller circuitry measures the touch location. TOUCHSCREEN TECHNOLOGY
  • 14. Advantages: • No touch overlay or coating required, so no layers that can be worn. • No brightness or contrast loss, SAW offers superior image clarity and high light transmission. • Screen can be operated by with a finger, gloved hand (cloth, leather, or rubber), leather or soft stylus. Something hard like a pen doesn't work. • Durable, scratch-resistant glass surface, continues to work if scratched. • Vandalism proof, when protected glass is used. • Antiglare glass option. • Very long life span. Tested on more than 50 million touches at a single location. Disadvantages: • The touch screen is not completely sealable, can be affected by large amounts of dirt, dust, and/or water in the environment. • Display surface needs to be slightly sunk from its mounting bezel TOUCHSCREEN TECHNOLOGY
  • 15. Acoustic pulse recognition Acoustic pulse recognition (APR) utilizes one pane of glass with one transducer in each corner. When touch occurs, mechanical energy (bending waves) radiates from the touch location and is detected by the transducers. The transducers pinpoint the touch location by generating a unique sound for that location on the glass. TOUCHSCREEN TECHNOLOGY
  • 16. WORKING The acoustic pulse recognition (APR) consists of a glass overlay with four piezoelectric transducers attached to the back surface. The transducers pick up the acoustic wave generated upon a touch, and convert it to an electronic signal. The signal is then digitized by the controller and compared to a prerecorded acoustic profile for every position on the glass. The cursor position is instantly updated to the touch location. TOUCHSCREEN TECHNOLOGY
  • 17. Advantages: • • • • • • • • • • • • Optics and durability of pure glass Works with finger, glove, pen, credit card, fingernail Resistant to water, dust, grease No wear-out mechanism Works even with scratches Excellent drag performance Sealable to NEMA 4/IP65 standards One time factory calibration, no drift Thin borders—only 5mm True flat surface Disadvantages: Small and large sizes Palm rejection • Touchscreen Mounting Essential • Not a True Multi-Touch TOUCHSCREEN TECHNOLOGY is
  • 18. OPTICAL TOUCH Optical touch is the technique of using infrared (IR) LED lighting to irradiate a sensing area. Intersecting the area reflects back the IR light to camera to detect fingers. Via precise calculation, system will get the coordinates of the fingers caught by camera. This technique is very suitable for large scale touch displays. With this technology, the accuracy and system speed is perfect, and multi touch function is also available.
  • 19. WORKING Working in concert, optical sensors located around the perimeter of the screen track the movement of any object close to the surface by detecting the interruption of an infra-red light source. The light is emitted in a plane across the surface of the screen and can be either active (infrared LED) or passive (special reflective surfaces). At the heart of the system is a printed circuit controller board that receives signals from the optical sensors. Its software then compensates for optical distortions and triangulates the position of the touching object with extreme accuracy. TOUCHSCREEN TECHNOLOGY
  • 20. Advantages: • 100% light transmission (not an overlay) • Accurate • Can be retro-fitted to any existing large format LCD or Plasma display • Can be used with finger, gloved hand or stylus • Requires only one calibration • Plug and play - no software drivers Disadvantages: • • • • Susceptible to “Ghosting” (Motion blur) Can Be Affected by Direct Sunlight Frame increases overall depth of monitor Cannot be fitted to plasma and LCD displays with integrated speakers TOUCHSCREEN TECHNOLOGY
  • 21. INFRARED TOUCH Infrared technology relies on the interruption of an IR light grid in front of the display screen. The touch frame or opto-matrix frame contains a row of IR-light emitting diodes (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The frame assembly is comprised of PCBs on which the opto electronics are mounted and are concealed behind a IR-transparent bezel which shields the opto’s from the operating environment whilst allowing the IR beams to pass through. When touching the screen one or more of the beams are obstructed resulting in an X and a Y coordinate being sent to the control electronics to indicate the exact touch point. TOUCHSCREEN TECHNOLOGY
  • 22. Advantages: • • • 100% light transmission since no overlay covering the display screen (protected glass is optional). Almost all kinds of stylus materials can be used in Infrared Touch Screen. Infrared is the earliest and most reliable touch screen technology, due to the improvement of LED materials. The lifetime of Infrared Touch Screen is much longer and more stable in operation. Disadvantages: • • • • • Low resolution Exhibits worst parallax problem of all technologies for CRT use since light beams do not follow curvature of CRT faceplate May cause unintended activation of target prior to finger contact with CRT caused by IR light beam location above surface of CRT Pressure hose down may cause unwanted target selection Dust, oil or grease buildup on frame that impedes light beam may cause malfunction TOUCHSCREEN TECHNOLOGY
  • 23. DISPERSIVE SIGNAL TECHNOLOGY Dispersive Signal Technology, specifically developed for interactive digital signage applications, sets new large-format touch standards for fast, accurate repeatable touch response. In addition, Dispersive Signal Technology’s operation is unaffected by contaminants, static objects or other touches on the touch screen. Other key characteristics of this patented technology are exceptional optics, ease of integration, and input flexibility. TOUCHSCREEN TECHNOLOGY
  • 24. WORKING TOUCHSCREEN TECHNOLOGY • Dispersive Signal Technology determines a “touch point” by measuring the mechanical energy (bending waves) within a substrate created by a finger or stylus touching the surface of the glass. • When the touch implement impacts the screen, bending waves are induced that radiate away from the touch location. • As the wave travels outwards, the signal spreads out over time due to the phenomena of dispersion. Piezoelectric sensors positioned in the corners on the backside of the glass convert this smeared mechanical impulse into an electrical signal. • The distance from each sensor determines the extent to which the signal is dispersed. The further away the “touch point” is from the sensor, the more the signal is smeared.
  • 25. Advantages and Disadvantages: • Because the bending wave travels within the glass substrate, objects or hands resting on the screen or onscreen contaminants do not affect the bending wave and therefore, do not affect the performance of the touchscreen. • 3M DST can be activated by bare finger, fingernail, stylus, and pen or basically anything that create the bending wave in the glass Substrate. • A downside is that after the initial touch, the system cannot detect a motionless finger. TOUCHSCREEN TECHNOLOGY
  • 26. MULTI-TOUCH In computing, multi-touch refers to a touch sensing surface's (track pad or touchscreen) ability to recognize the presence of two or more points of contact with the surface. This plural-point awareness is often used to implement advanced functionality such as pinch to zoom or activating predefined programs. TOUCHSCREEN TECHNOLOGY
  • 27. Multi-touch has been implemented in several different ways, depending on the size and type of interface. The most popular form are mobile devices, tablets, touchtables and walls. Both touch-tables and touch walls project an image through acrylic or glass, and then back-light the image with LEDs. TOUCHSCREEN TECHNOLOGY
  • 28. TYPES: • Capacitive Technologies: • Surface Capacitive Technology or Near Field Imaging (NFI) • Projected Capacitive Touch (PCT) • Mutual capacitance • Self-capacitance • In-cell: Capacitive • Resistive Technologies: • Analog Resistive • Digital Resistive or In-Cell: Resistive • Wave Technologies: • Surface Acoustic Wave (SAW) • Bending Wave Touch (BWT) • Dispersive Signal Touch (DST) • Acoustic Pulse Recognition (APR) TOUCHSCREEN TECHNOLOGY
  • 29. • Optical Technologies: • Optical Imaging or Infrared technology • Rear Diffused Illumination (DI) • Infrared Grid Technology (opto-matrix) or Digital Waveguide Touch (DWT)™ or Infrared Optical Waveguide • Frustrated Total Internal Reflection (FTIR) • Diffused Surface Illumination (DSI) • Laser Light Plane (LLP) • In-Cell: Optical • Force-Sensing Touch Technology TOUCHSCREEN TECHNOLOGY
  • 30. The upcoming in-cell and on-cell technologies WHAT ARE THESE TECHNOLOGIES? • Manufacturers of touch screen devices usually use three layer. • This is because LCD manufacturers produce the LCD panel, touch sensor manufacturers produce the touch screen layer and glass manufacturers (such as Corning) produce the protective outer glass. • But instead we can actually move the touch technology onto the outer glass layer. This is called on-cell or G2. • We can also choose to put the touch sensors into the actual display panel. This is called in-cell. Both layers are perfectly suited for the touch electrodes. TOUCHSCREEN TECHNOLOGY
  • 31. WHY WE NEED THEM? • With both in-cell and out-cell technologies, the thickness of smartphones, tablets etc. considerably reduces. • With both on-cell and in-cell we can expect better color saturation as light has to pass through fewer layers. • Depending on the implementation it can even make touch feedback more accurate. • And lastly, on-cell and in-cell makes it feel like we are actually touching our phone’s display instead of an outer glass layer. TOUCHSCREEN TECHNOLOGY