Transcript Multi-Touch Table - Rochester Institute of Technology

MULTI-TOUCH TABLE
Athena Frazier
Chun Lau
Adam Weissman
March 25, 2008
Senior Projects II
Outline of Design Review
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Project Overview
User Interface
Project Subsystems
 Input
 Output
 Cabinet
 Computer
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and Software
Testing
Foreseen Problems
Project Description
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The multi-touch table is a user interface device that
will allow a user to interact with a computer through
use of a multi-touch display.
The application to be demonstrated on the multitouch display will be a game of pong.
User Interface
A user or users will be
able to naturally
interact with the
application by
apparently
manipulating the
workspace.
Project Subsystems
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Input Subsystem
Output Subsystem
Cabinet Subsystem
Computer and Software
Input Subsystem
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To be able to detect
fingers placed on multitouch screen, Infrared (IR)
light will be injected into
the side of a sheet of
polished acrylic.
IR blobs will be formed at
locations of frustration,
which can be detected
using a camera.
Frustrated Total Internal Reflection
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This technique is referred to as Frustrated Total
Internal Reflection (FTIR).
Input System: IR LED Arrays
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To inject IR light into the
acrylic sheet, IR LED
arrays are placed on all
four sides of the acrylic.
Aluminum U-Channel
with holes drilled in it is
used to hold multiple IR
LEDs.
Input Subsystem: Compliant Surface
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A compliant surface will be added to the acrylic
sheet because of its abilities to:
 Protect
the acrylic from scratches
 Block out light interference
 Provide consistent blobs for detection
 Improve the brightness of IR blobs
 Show different touch pressures
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Silicone Rubber was chosen as the compliant surface
because it is transparent and shows all of the above
traits.
Input Subsystem: The Camera
Fire-I Digital Camera Board
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A requirement of the system is that the
camera needs to be able to capture a
screen size of 20” by 35” from less than
3’ away. Therefore, we will use the Fire-I
Digital Camera Board.
The camera’s uncompressed VGA image
capability prevents wasting unnecessary
CPU usage.
One advantage of this camera is that it
uses the Fire Wire interface. Fire Wire
allows for a more consistent speed that is
usually greater than speed of the USB
interface.
Camera Considerations
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Due to the requirements for a wide view capture, a specific
lens is needed. All wide-angle lenses found were fish eye
lenses.
This requires that a distortion correction filter be applied
before the image can be used for blob detection.
An optical band or a high pass filter will be used to block out
visible light.
Sample of the Fish Eye Effect
Image with corrected barrel distortion
Output Subsystem: The Projector
Toshiba TDP-ET20U
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A rear projection setup allows the projector to be placed inside the
multimedia table. However, with the size of the multimedia table in
mind, there is a strict requirement on the “throw” distance of the
projector.
An extremely short throw distance projector was found to overcome
the problem.
The Toshiba TDP-ET20U is able to display 40” diagonal screen
image from a mere 1.7 feet away.
This projector also has a built-in function to invert output images for
rear view projection applications, which prevents the need for
adding a mirror inside the table.
Output Subsystem: Diffusion Layer
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A diffusion layer is needed to provide a surface for
the projected image to be displayed.
To diffuse the projected image through rear
projection a sheet of Rosco Grey Projection Screen
will be used.
Rosco Grey provides the added benefit of blocking
ambient IR light.
Cabinet Subsystem
Acrylic
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To enclose and protect
the system from
ambient light, a
cabinet will be built.
The cabinet is made
of wood and will
include fans in order
to regulate the
internal temperature.
Web camera
Projector
Mac
Cabinet Subsystem cont.
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Two fans and baffles
will be installed on
each side of the
cabinet to increase
ventilation.
Two doors will be
installed to provide
access to the cabinet if
needed.
Computer Subsystem
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The computer to be used will be a Mac Mini.
This computer was selected because of its small form
factor and its ability to run multiple operating
systems. The Mac Mini was also freely available. At
the time of deciding on the computer, the operating
system had not been chosen.
The Windows XP operating system was chosen
because the Touchlib package is highly supported in
Windows.
Programming for the Multi-Touch Table
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Touchlib is an open source C++ software package
that contains code to analyze data from a camera,
detect IR blobs from within the data, interpret that
IR blob data, and generate TUIO events for the
application to interpret.
Since most operating systems only expect one
mouse click at any single time, a new event and
protocol must be used to interpret any number of
touches, the TUIO protocol.
Touchlib: Hardware–Software Interface
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Touchlib acts as a driver for the multi-touch table
device so that the computer embedded inside can
interpret touches from the user or users.
Individual applications can be written to interpret the
data supplied from Touchlib and provide feedback to
the display for the user or users.
Touchlib Calibration
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The Touchlib library
comes with software to
calibrate and test the
blob detection for a
multi-touch setup.
Also, Touchlib comes
with software to
calibrate and test the
camera that will be
used with the multitouch table.
General Application Program Flow
Application Development
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Many different platforms can be
used to develop multi-touch
applications utilizing TUIO events.
Such platforms include:
 Adobe
Flash
 Java
 vvvv
 C++
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At least one demo application will
be developed with one of the
platforms above.
Testing Strategies
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All hardware subsystems will be tested thoroughly and
independently.
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Mechanical components (cabinet)
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LED Arrays
Integration
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Silicone Rubber
Thermal testing
Input System
Output System
Software
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Touchlib
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Hardware integration and blob detection
Applications
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Single touch events
Using table hardware
Foreseen Problems
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Hardware
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Cabinet building
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Thanks Todd (the Mechanical Engineer) for attempting to avoid
some of these problems!
Ambient Light
 Silicone Rubber
 Fan placement
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Barrel Distortion
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Overheating
Fisheye effect
Software
Learning application platforms
 Mac Mini not powerful enough
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Questions?