The objective of this senior design project was to design and build a multi-touch interface device that could allow users to interact with a computer application by directly touching the screen of the device. To demonstrate the table’s multiple-touch abilities, two different application were developed.

What makes this multi-touch table unique is the fact that it is enclosed in a cabinet, using rear projection to display the applications to the user or users. These constraints required much thought in designing the system. Specifically how to deal with ambient light, heat, and space issues.

PROJECT CONCEPT:

HOW IT WORKS:

MULTI-TOUCH APPLICATION:

TEAM MEMBERS:

COST ANALYSIS:

Multi-Touch TableRochester Institute of Technology

Department of Computer EngineeringSenior Design Project Spring 2008

Adam WeissmanAdam Weissman44thth Year MS/BS Year MS/BS

StudentStudent

Athena FrazierAthena Frazier44thth Year MS/BS Year MS/BS

StudentStudent

Chun LauChun Lau55thth Year BS Student Year BS Student

The method used for detecting multiple finger touches on the screen of the multi-touch table, is called Frustrated Total Internal Reflection (FTIR). FTIR allows the computer to detect touches by generating infrared light blobs at touch points which can be detected by the camera. By lining the screen of the multi-touch table with IR LEDs, when a finger touches the screen the IR light reacts differently causing the light to become concentrated. For this table, 80 infrared LEDs were placed around the perimeter of the screen. A camera without an IR filter is able to detect the IR blobs and send their locations to a computer to be used.

To detect the IR blobs, a Fire-I Digital Board Camera from Unibrain was used. The camera needed to be able to capture a large viewing area and also provide quality video without long delays. To display the image on the sheet of acrylic acting as the screen to the multi-touch table was a Toshiba et20u projector. The essential criteria for the projector was the ability to project a large image in a very short range.

The cabinet to hold the hardware was constructed from a wooden frame. The screen was a single sheet of ¾” acrylic. A sheet of Rosco Grey Projection Screen was used to diffuse the projected image making it viewable. To control the heat inside the cabinet, four fans (two for intake and two for exhaust) were incorporated into the design. An ATX power supply was put in the cabinet to provide power to the LEDS and fans.

What makes this multi-touch table project unique is the fact that it was designed using a different design methodology as compared to most senior design projects. This project was designed around the hardware whereas most projects are application, and therefore software, specific. Many of the design decisions were made to allow different software applications to be developed for the same hardware design.

A touch interface photo organization application was developed. To interact with the application, the user must perform different touch movements to accomplish various actions. For example, to resize an image the user must place two fingers on a single image and move his or her fingers apart.

Component Unit Price Our Price Quantity TotalToshiba TDP-ET20U $650 $650 1 $650 Unibrain Fire-I B/W $130 $130 1 $130 1.9mm Lens $30 $30 1 $30 Fan $8 $8 4 $32 Wood $20 $20 3 $60 Caster $8 $8 4 $32 Acrylic $70 $70 1 $70 IR LED $0.42 $0.42 100 $42 Mac mini $599 $0 1 $0 Silicone Rubber $50 $50 1 $50 Rosco Projection Screen $15 $15 1 $15 ATX Power Supply $30 $0 1 $0Various Resistors $.20 $0 10 $0Wire spool $5 $5 2 $10Total     $1,106 Inside of cabinet Dr. Czernikowski using the

photo application

Basic multi-touch application flow diagram

Application showing touch recognition