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SURFACE COMPUTING&

MULTI-TOUCH DISPLAY DEVICES

Introduction

Surface computing is the term for the use of a specialized computer GUI in which traditional GUI elements are replaced by intuitive, everyday objects. Instead of a keyboard and mouse, the user interacts directly with a touch-sensitive screen.

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Description

The multi-touch device is a user interface device that will allow a user to interact with a computer through use of a multi-touch display. Thus, it is a substitute to the keyboard and mouse. In this user can directly interact with the system with their fingers and not only this but with multiple touches at the same instant.

A basic touch-screen has three main

components: 1. Touch sensor; 2. Controller; 3. Software driver. The touch-screen is an input device, so it

needs to be combined with a display and a PC or other device to make a complete touch input system.

How Does a Touchscreen Work? 

Touchscreen Technologies

Resistive Capacitive

Surface Projected

Optical imaging FTIR DI DSI

Resistive Touchscreen

Composed of multiple layers separated by thin spaces Using indium tin oxide (ITO) layers Different standards

4, 5, and 8 wire types Each have advantages

Resistive Touchscreen

User Presses Down Contact is Made Uniform Voltage on

First Screen for X Same on Second

screen for Y Happens

instantaneously

4-Wire design One screen for X

Another screen for Y

Both create voltage gradient.

Uses voltage divider

Advantages & Disadvantages

Works well with fingertip or stylus input

Generally most affordable touchscreen technology

Rugged/Durable Has multi-touch

input capabilities

Not as accurate

Multi-touch much more complex

Usually no discretion between stylus and hand

More pressure needed

Capacitive Touch Technology

Consists of: Insulator (glass or

Air) Conductive coating

(ITO) Two types:

Surface projected

Surface Capacitance

Only one side is coated

Electrodes at the edges Distribute voltage

Capacitor forms Current flows

Determine location Controller Ratio of currents

, XY coordinates

ITOGlass surface Finger

i

iv

AR

1i

R

Surface Capacitance

Projected Capacitance

Two parallel ITO(Indium Tin Oxide ) layers Two sheets of glass

Projected Capacitance E Field is projected

through glass Finger couples with E

field Capacitance changes

ITO

Air

ITO

ITO

Glass Surface

Finger

C1

Ct

Cnew=(C1*Ct) / (C1+Ct)

ITO

Air

ITO

C1 C2 C∞

Ceq C1+C2+……+C∞

DC

Capacitor at each point on the surface

Surface vs. Projected Limited resolution Single touch Operation with direct

contact

High resolution Multi touch Operation with

indirect contact

Multi-Touch Using Infrared

Frustrated Total Internal ReflectionFrustrated Total Internal Reflection

A process by which light is trapped within a medium and can be interrupted by a third medium of higher reflective index to cause light to escape.

Diffused Illumination

Diffused Surface Illumination

Alternative Single-Unit Design

Eliminates rear projectionExpensive Robustness

Software

Surface Capture via Detector Digitized View

Software Cont.

Interpret and Relay Information Assign Objects or gestures with Unique ID# and

location Compare and Execute

DigitizedObject

Application

ProtocolRaw Data Feedback to User

Universal Design Principles

Utility for all users Simple and intuitive

Touchscreens depend on visual feedback in order to use

Improving Accessibility?

Cursor movements

as command shortcuts

Takes place of keyboard shortcuts

Useful in applications where keyboard use is less prominent or undesirable

Pointing Device Gestures

Above: Some possible cursor movement patterns for use in gesture support.

Implementation: Step 1

Filter Input Sampling rate Smooth out input data, get rid of unnecessary

“noise” Simplify data analysis

Implementation: Step 2

Vectorize Separate x- and y-component Compute dominant component and ignore

smaller one Store in array

Implementation: Step 3

Matching Match captured vector array to pre-defined

gesture library If no match, pop smallest vector from array and

repeat matching process

Example

Fig. 1 – User input

Fig. 2 – Captured/filtered pointer data

Fig. 3 – After vectorization

Fig. 4 – Final matching result

Allows for a quicker and more efficient UI Universal Design

Enhances usability for visually-impaired as well as non-impaired

Easily added to existing touchscreen devices, no additional hardware required

Goal

A personal computer with 20 GB free

hard disk space, 1GB RAM and PIV + processor can be efficient enough.

The Windows Vista operating system was chosen because the CCV package is highly supported in Windows.

Computer Subsystem

Many different platforms can be

used to develop multi-touch applications utilizing TUIO events. Such platforms include:

Adobe Flash Java C++ Python

Application Development

Personal Computing Graphics Audio Mixing Video Playing Computer Gaming Slide Presentations

……and many more!

APPLICATIONS