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System Architecture
EOG HCIElectrooculography Human Computer Interface
• Currently, 12 million people within the U.S require assistance for
ordinary tasks. While computer technology can help individuals with
upper body movement disabilities independently handle a wide range
of activities, they cannot provide computer inputs with a standard
keyboard or mouse. The purpose of this project was to provide these
people with a cost-effective control system for home computers.
• Electrooculography (EOG) is a technique that measures steady state
corneal-retinal potential of the eye balls. EOG signals are collected by
two pairs of surface electrodes placed around the eyes. Compared
with other biological signals, they have larger amplitude and
distinguishable patterns for different types of eye movements.
Furthermore, the signals linearly change as eyes rotate away from the
center.
• Taking advantages of EOG signals, this project developed a low-cost
and power-efficient device, “Eye-Mouse” ,which used eye movements
to control joystick-like movements of the computer cursor in the four
cardinal directions.
Using 3D printer, a set of adjustable goggles
were designed and fabricated to house the
EOG electrodes. Afterwards, a circuit was
designed to provide a differential EOG
signals on the needed range by the ADC
(Analog to Digital Converter) on the
microcontroller unit. The circuit was
prototyped on breadboard, Vector board and
PCB.
Following signals were fed to the ADC on the
vertical and horizontal channels.
Horizontal Movement
Introduction
Implementation Results
12096.15385
2066.769231
3365.307692
0 2000 4000 6000 8000 10000 12000 14000
Eye-Mouse EOG
Verbatim Laser
Logitech Optical
Time (ms)
Comparison of Average Time for 13 Trials
Average Time for Movement
Vertical Movement
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90
Eye-Mouse EOG
Microsoft Opticle
Logitech Laser
R2 Value
Comparison to Minimum Fitts's Law Requirement
Performance of Mouse Minimum Requirement of Fitts's Law
Movement Result Comparison to Conventional Mice
Horizontal 0.264 linear correlation co-efficient 41.1% less performance
Vertical 12096 ms average movement time 77.5% slower movement
R² = 0.1522
R² = 0.7743
R² = 0.264
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 1 2 3
Tim
e (
ms)
Index of Difficulty
Logitech Laser vs Microsoft Optical vs Eye-Mouse EOG
Microsoft Opticle
Logitech Laser
Eye-Mouse EOG
Linear (MicrosoftOpticle)
Linear (LogitechLaser)
Linear (Eye-MouseEOG)
y = 10.049x + 3295
y = -2.2857x + 2082.8
y = 680.68x + 7331.4
0
5000
10000
15000
20000
25000
30000
35000
0 5 10 15
Tim
e (
ms)
Trial
Logitech Optical vs Verbatim Laser vs Eye-Mouse EOG
Logitech Optical
Verbitim Laser
Eye-Mouse EOG
Linear (LogitechOptical)
Linear (VerbitimLaser)
Linear (Eye-MouseEOG)
• User wears EOG goggles.
• A single cable from goggles
connects to The EOG HCI.
• USB cable from EOG HCI
connects to PC.
• Mouse cursor movement is
visible on PC Monitor screen.
• Cross-platform compatibility.
A testing application was designed based on Fitts’s Law.
Performance was compared to two other conventional mice:
Movement time was compared against two other conventional mice
and averages of consecutive movement between the same distance
were recorded:
Top Level ArchitecturePC Monitor
User wearing EOG Apparatus
Electrode Cable
EOG HCI
PC
USB Cable
PC Video Output
User wearing EOG HCI Spectacles
COMPUTER
Multi-Channel ADC
SAM4S ARM MCU
USB
CIRCUIT
Raw EOG Signal
Mouse Movement Algorithm
HID Compliant Mouse Movement
Digital Horizontal and Vertical Values
Mouse Movement Speed and Direction
5V PowerPower Filtering
Power Convertion
Signal Amplification
Signal Filtering
Signal Differentiation
Signal Offset
Analog Difference Signal (between 0V to 1V)
Level-2 Architecture
Digitized signals then are processed on the microcontroller to
determine the eye movements. An algorithm was setup for blinks,
horizontal, and vertical eye movements to associate them with
joystick-like movement of the mouser cursor on the screen.
Since Eye-mouse is detected as a generic USB mouse, it is multi-
platform compatible.