MULTI TOUCH TECHNOLOGYBY: Robert McGrellis

SELF INTRODUCTION Senior Undergraduate Student at Wright

State University

Major Field of Study: Electrical Engineering

Minor: Computer Science

OVERVIEW

TOPIC INTRODUCTION State of the Art Report on Multi Touch Screen

technology

Technology used in Apple iPhone, iTouch, and in wall and table displays.

Jefferson Han founder of Perceptive Pixel

SCOPE My Research will focus on three techniques

Resistive Capacitive (projective capacitive) FTIR (Frustrated Total Internal Reflection method

Will not cover SAW (Surface Acoustic Wave technology) Optical Infrared touch screens Surface Capacitive touch screens Computer Programming aspects

HISTORY OF MULTI TOUCH

1972: PLATO IV Touch Screen Terminal (Computer-based Education Research Laboratory, University of Illinois, Urbana-Champain)Touch screens started to be developed in the second half of the 1960s.

1982: Flexible Machine Interface (Nimish Mehta , University of Toronto). The first multi-touch screen developed. This screen is called a resistive touch screen and requires finger pressure to sense touch.

HISTORY OF MULTI TOUCH 1983 Bell Labs

Bell Labs at Murray Hill published a comprehensive discussion of touch-screen based interfaces.In 1984 Bell Labs engineered a touch screen that could change images with more than one hand.

Fingerworksa Newark-based company run by University of Delaware John Elias and Wayne Westerman2005: Fingerworks was acquired by Apple Inc.

HISTORY OF MULTI TOUCH 2005: Jeff Han: consulting research scientist at New York University starts

developing Multi Touch technology

2006: Perceptive Pixel  Very elegant implementation of a number of techniques and applications on a table format rear projection surface.In 2005 Han published a paper on Multi-Touch Sensing through Frustrated Total Internal ReflectionFormed Perceptive Pixel in 2006 in order to further develop the technology in the private sector

2007: Apple Inc. introduced the iPhone, marking the first time multi-touch technology was

used on a phone. The iPhone includes such components as a web browser, music player, video player, and a cell phone without the use of a hard keypad or stylus.Following the release of the iPhone, Apple also expanded its use of multi-touch computing with the new iPod Touch,

STANDARD TOUCH SCREENS Resistive two layers of indium tin oxide are printed on a thin sheet of plastic

film with an air gap in between them. The touch location is detected when finger pressure forces one ITO layer onto the other and the X and Y coordinates are measured.

Capacitive electrodes at corners of the provide a uniform AC voltage field. When the screen in pressed the field is disrupted. The controller connected to the touch screen measures the change in current flowing form each corner and calculates the X and Y coordinates.

RESISTIVE TOUCHSCREEN THEORY Voltage Divider (Model of Resistive Touch method) In electronics, a voltage divider is a simple linear circuit that

produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage division refers to the partitioning of a voltage among the components of the divider.

RESISTIVE TOUCH SCREEN

Rx denotes the x-axis resistance of the coating and Ry denotes the y axis resistance of the coating. When the conductive coating is pressed against the resistive coating

RESISTIVE TOUCH SCREEN 4-wire technique

Figure 1 Shows the exploded view showing the layers of a touch screen

CAPACITIVE TOUCHSCREEN THEORY Capacitive Coupling the transfer of energy within an electric circuit

by means of the capacitance between circuit nodes.

Capacitance a measure of the amount of electric charge

stored (or separated) for a given electric potential.

Insulator is a material that does not allow the flow of electric current through them

Electric fieldThe space surrounding an electric charge. Exerts a force on other electrically charged objects. The concept of an electric field was introduced by Michael Faraday.

CAPACITIVE TOUCH SCREEN•Uses a single sheet of glass with multiple sheets with conductive coating.

coated with a material, typically indium tin oxide, that conducts a continuous electrical current across the sensor. The sensor therefore exhibits a precisely controlled field of stored electrons in both the horizontal and vertical axes - it achieves capacitance.

•An electrode pattern on multiple ITO layers surrounding the screen produces an AC voltage field across the coating. When a finger touches the screen a capacitive coupling effect occurs between your finger and the screen.

•Detects the position by measuring the distribution of change in the signals between X and Y electrodes

CAPACITIVE TOUCH SCREEN

Mutual capacitance touch-screen contains a grid of sensing lines and driving lines to determine where the user is touching.

PERCEPTIVE PIXEL Jefferson Han founder of Perceptive Pixel Inc

Demoed display first at TED (Technology Entertainment Design Conference) Feb 2006

The displays use infrared light emitting diodes along with an infrared camera to determine the point of contact. Han envisions large collaborative spaces that will allow multiple users to work and interact. Perceptive Pixel’s technology is currently being utilized, in the form of the Multi Touch collaboration wall, by CNN and an unspecified government contractor

Building large multi touch screens that can sense up to 20 or more fingers

Company is doing research to expand the capabilities of multi touch technology they are developing new applications as you saw in the video clips.

Getting away from the standard mouse and keyboard computer user input

TOTAL INTERNAL REFLECTION Total internal reflection is an optical phenomenon that

occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary no light can pass through, so effectively all of the light is reflected. The critical angle is the angle of incidence above which the total internal reflection occurs.

•As the angle of incidence increases, the amount of light transmitted decreases until total reelection occurs shown by the blue line

FTIR INTERNAL REFLECTION Frustrated Total Internal Reflection

•Display surface is 6 mm piece of clear acrylic with infared LEDs on the edges

•Light travels predictable paths within the acrylic, when uninterrupted because of total internal reflection •When the screen is pressed the light

diffuses, deviates from straight trajectory. This changes the path of the internal reflection.

•A camera below the acrylic surface captures the diffusion and sends information to an image processing software, which translates the information.

SUMMARY Many ways to implement Multi Touch Technology

3 methods for Multi touch Resistive Capacitive FTIR (Frustrated Total Internal Reflection

Jeff Han, founder of Perceptive Pixel uses the FTIR method. His research focuses on expanding the capabilities of the Multi Touch technology

CREDITS

Baker, Bonnie. "Reach out and touch." EDN 52.20 (2007): 24-24.

Fritz, Mark. "Keys to the Kiosk." EMedia 13.4 (Apr. 2000): 28. Academic Search Complete. EBSCO.17 Feb. 2009http://search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=3050170&site=ehost-live

Philipp, Hal. "Please Touch! Explore The Evolving World Of Touchscreen Technology Electronic Design 56.8 (2008): 60-61. “

"How It Works." Popular Mechanics 186.1 (2009): 29-29.

"PRODUCT RESEARCH." Control Engineering 53.4 (2006): 65-65.

"Resistive touchscreens." Machine Design 80.5 (2008): 52-52.

Special thanks to Phil Flynn

Research

•Pictures www.technologyreview.com www.apple.com www.perceptivepixel.com