TOUCH SCREEN SENSOR TECHNOLOGY BY GANESH SHAGA MTECH(EI) 94003 GANESH SHAGA (94003)
CONTENTS • Introduction • How does a touch screen sensor work • Touch screen technology • Comparison • Microsoft surface • Applications GANESH SHAGA (94003)
INTRODUCINGTHETECHNOLOGY • A touch screen is an input device that allows users to operate a PC by simply touching the display screen. • The display screen has a sensitive glass overlay placed on it and we could give the desired input by touching it. • A touch screen is based on CRT (Cathode Ray Tube) technology, that accepts direct onscreen input. • The touch screen needs to be combined with a display and a PC or other device to make a complete touch input system . GANESH SHAGA (94003)
HOWDOESATOUCHSCREENWORK? Main touch screen components: • Touch sensor • Controller • Software driver GANESH SHAGA (94003)
TOUCHSENSOR • A touch screen sensor is a clear glass panel with a touch responsive surface which is placed over a display screen so that the responsive area of the panel covers the viewable area of the display screen. • The sensor generally has an electrical current or signal going through it and touching the screen causes a voltage or signal change. This voltage change is used to determine the location of the touch to the screen GANESH SHAGA (94003)
CONTROLLER • The controller is a small PC card that connects between the touch sensor and the PC. It takes information from the touch sensor and translates it into information that PC can understand. • Controllers are available that can connect to a Serial/COM port (PC) or to a USB port. GANESH SHAGA (94003)
SOFTWARE DRIVER • The driver is a software that allows the touch screen and computer to work together. It tells the operating system how to interpret the touch event information that is sent from the controller. • Most touch screen drivers today are a mouse-emulation type driver. This makes touching the screen the same as clicking mouse at the same location on the screen. GANESH SHAGA (94003)
Touchscreen Technology • Resistive touch screen • Capacitive touch screen • Infrared touch screen • Surface acoustic wave (SAW) touch screen • Microsoft surface GANESH SHAGA (94003)
Resistive touchscreen • Structure Resistive touch screens consist of a glass or acrylic panel that is coated with electrically conductive and resistive layers made with indium tin oxide (ITO) .The thin layers are separated by invisible spacers. GANESH SHAGA (94003)
Continued… • Resistive touch screen monitor is composed of a flexible top layer and a rigid bottom layer separated by insulating dots, attached to a touch screen controller. • The inside surface of each of the two layers is coated with a transparent metal oxide coating • Pressing the flexible top sheet creates electrical contact between the resistive layers, producing a switch closing in the circuit. • The controller gets the alternating voltages between the two layers and converts them into the digital X and Y coordinates of the activated area. GANESH SHAGA (94003)
VS20UA CONTROLLER • Supply Voltage 5.0V DC • Maximum Current 20mA • Resolution 12-bit GANESH SHAGA (94003)
Resistive touchscreen • Characteristics: • Cost effective solutions • Activated by a stylus, a finger or gloved hand • Not affected by dirt, dust, water, or light • 75%~85% clarity • resistive layers can be damaged by a very sharp object GANESH SHAGA (94003)
CAPACITIVETOUCHSCREENS Surface Capacitive • It has a an uniform conductive coating on a glass panel. • During operation, electrodes around the panel's edge evenly distribute a low voltage across the conductive layer & creates an uniform electric field. • A finger touch draws current from each corner. • Then the controller measures the ratio of the current flow from the corners and calculates the touch location GANESH SHAGA (94003)
Projected CapacitiveTouchscreen 3layers:-front and back protective glass provides optical and Strength enhancement options & middle layer consists of a laminated sensor grid of micro-fine wires GANESH SHAGA (94003)
Continued… • During a touch, capacitance forms between the finger and the sensor grid. • The embedded serial controller in the touch screen calculates touch location coordinates and transmits them to the computer for processing. GANESH SHAGA (94003)
Capacitive touchscreen • Characteristics: • Durable and resistant to scratches for demanding applications • Faster and more responsive • Immune to surface contaminants • Superior optical clarity, brighter display and less surface reflection • Must be touched by finger, will not work with any non-conductive input GANESH SHAGA (94003)
Infrared touchscreen • Infrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame contains a row of IR-light emitting diode (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger, enters the grid, it obstructs the beams. One or more photo transistors from each axis detect the absence of light and transmit signals that identifies the x and y coordinates.
SURFACE WAVE TECHNOLOGY • It has a transmitting and receiving transducers for both the X and Y axes. • The touch screen controller sends a 5 MHz electrical signal to the transmitting transducer, which converts the signal into ultrasonic waves within the glass. • These waves are directed across the front surface of the touch screen by an array of reflectors. • Reflectors on the opposite side gather and direct the waves to the receiving transducer, which reconverts them into an electrical signal—a digital map of the touch screen.
Continued… • When we touch the screen, we absorb a portion of the wave traveling across it. The received signal is then compared to the stored digital map, the change recognized, and a coordinate calculated. . The digitized coordinates are transmitted to the computer for processing.
2701RSU CONTROLLER • Voltage +5 VDC • Baud Rate 9600 (default) and 19200 • Touch Resolution 12bit, size independent • Conversion Time 10 ms per coordinate set
Microsoft Surface “Microsoft Surface represents a fundamental change in the way we interact with digital content. With Surface, we can actually grab data with our hands, and move information between objects with natural gestures and touch. Surface features a 30-inch tabletop display whose unique abilities allow for several people to work independently or simultaneously. All without using a mouse or a keyboard.”
How does it work? • The Surface is not a touch-sensitive screen device… The screen itself is not electronic. • The Surface uses multiple infrared cameras beneath the screen/table top to sense objects, physical touch, etc. • The Surface “recognizes objects based on shape or by using domino-style identification (domino tags) on the bottom of the objects.” • This information is processed and displayed using “rear projection”. (1) Screen: Diffuser -> ”multitouch" screen. Can process multiple inputs and recognize objects by their shapes or coded "domino" tags. (2) Infrared: The ”machine vision" is aimed at the screen. Once an object touches the tabletop -> the light reflects back and is picked up by infrared cameras. (3) CPU: Uses similar components as current desktop computers -> Core 2 Duo processor, 2GB of RAM and a 256MB graphics card. Wireless communication -> WiFi and Bluetooth antennas (future -> RFID). Operating system -> modified version of Microsoft Vista. (4) Projector: Uses a DLP light engine ( rear-projection HDTVs).
How is the Surface used? • Wireless! Transfer pictures from camera to Surface and cell phone. “Drag and drop virtual content to physical objects.” • Digital interactive painting • At a phone store? Place cell phone on the Surface and get information, compare different phones, select service plan, accessories, and pay at table! • Play games and use the Internet. • Watch television • Browse music, make play lists.
CLOSING THOUGHTS Though the touch screen technology contains some limitations it’s very user friendly, fast, accurate, easy for the novices & fun to operate. It has been widely accepted..
REFERENCES:  S. D. Desiano. “Touch Screens,” [Online], [cited 2007 Sept. 2] Available HTTP: http://www.bookrags.com/research/touch-screens-csci-02 “Calibration in touch-screen systems,” Analog ApplicationsJournal, [Application Notes] 3Q, (2010Aug.), Available HTTP: http://focus.ti.com/lit/an/slyt277/slyt277.pdf  Tyco Electronics, “Touch Technologies,” [Company Website], [2007 Sep. 1], Available HTTP: http://elotouch.com/Technologies/default.asp  Mass Multimedia, Inc., “Introduction to Touch Screen Systems,” Website], [cited 2007 Sep. 1], Available HTTP: http://www.touchscreens.com/introduction.html  New Directions in Human-Computer Interaction Education, Research and Practice. Interactions, Vol. 2 , No. 1, pp. 69 – 81. GANESH SHAGA (94003)
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