Eye Movement Measuring System

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Eye Movement Measuring System

• April 10, 2002 Group 9
• Bonnie Kroll
• Anica Rothrock
• Lendy Stuber

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Eye Movement Measuring System Project Review

• Project
• 1) Design an optimal magnet/sensor configuration
  to measure eye movement
• 2) Implement an algorithm to output accurate
  coordinates with real-time capabilities

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Eye Movement Measuring System Project Motivation

• Features
• Magnet/sensor system
• Lasts longer than eye coil methods
• Less invasive/faster recovery vs. eye coil
  implantation
• Data conversion
• Currently not available for magnet/sensor system
• Possibly faster and more accurate than coil system

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Eye Movement Measuring System Design Requirements

• System Requirements
• Magnets
• Are ? 1mm x 2 mm x 3mm
• 90 apart
• Sensors
• Array cannot obscure vision or be unsafe
• Optimal if magnets do not pass plane of sensors
• Must surround magnets
• Algorithm
• Samples at a rate of at least 200 Hz
• Accurate to at least 0.2 degrees

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Eye Movement Measuring System Analytic Efforts -
Hardware

• Magnets - Computer modeling of magnetic fields
• To determine relative strength and orientation of
  magnetic fields within modeled system
• Flux at surface 1500 Gauss
• Magnetic field range proportional to 1/r3

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Eye Movement Measuring System Analytic Efforts -
Hardware

• Sensors - Configuration testing in EE lab
• To determine optimal placement and orientation
  for GMR sensors
• Power supply 5 Volts
• Sensitivity Range 20mm

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Eye Movement Measuring System Analytic Efforts -
Hardware

• Sensor Array Mask- Design considerations
• Type of plastic
• Material thickness 3mm
• Proper shape to fit subject
• Dimensions 43mm x 44mm x 27mm
• Attachment of sensors
• Slot dimensions 1.5mm x 5 mm
• Attachment of mask to subject
• Angle of bolt attachment 45º

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Eye Movement Measuring System Analytic Efforts -
Software

• Data Analysis - Acquisition/filtration using
  Spike2

• To compare the sensor output data to known
  position coordinates
• To reduce noise and produce a cleaner signal
• Sampling rate 200 Hz
• Gain 20
• Offset None
• Filters Lowpass 30 Hz

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Eye Movement Measuring System Analytic Efforts -
Software

• Data Analysis - Creation of useable data
• To manipulate data and place it into a table
• To visualize sensor activity in relation to eye
  movement

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Eye Movement Measuring System Analytic Efforts -
Software

• Software development - Implementation of
  algorithm
• To convert the sensor voltage output to X-Y
  position data

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Eye Movement Measuring System Design Details

• Overview of System

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Eye Movement Measuring System Design Details -
Hardware

• Two Magnet Configuration
• NIB Magnets
• Located on outer surface of eye
• Positioned 90º from each other
• Oriented North out
• Optimal position 9mm apart (in 5.5mm radius
  eye)

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Eye Movement Measuring System Design Details -
Hardware

• Four Sensor Configuration
• GMR Sensors
• Located 6-7mm from magnets
• Positioned 14x14mm square
• Oriented perpendicular to magnet dipole

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Eye Movement Measuring System Design Details -
Hardware

• Wires/Connectors
• 34 gauge enamel insulated magnet wire
• CTM-12-03-L-DV 10 pin socket
• FTM-12-03-L-DV 10 pin header
• 30 gauge Kynar insulated wire
• 1/2 inch 28 gauge ribbon cable
• Standard 10 pin 0.1 inch IDC connector
• RG174 coaxial cables
• CPM88 mini coaxial

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Eye Movement Measuring System Design Details -
Hardware

• Amplifier
• NPI DPA2F Amplifier
• AD620 Instrumentation Amplifier
• Data Acquisition box
• CED Power 1401

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Eye Movement Measuring System Design Details -
Software

• Spike2
• To capture and analyze data
• Gives a direct link from the data acquisition box
• Excel
• To create look-up table
• To eliminate false data
• MatLab
• To create and test the proposed algorithm
• Provides a large collection of tools, user
  scripts and mathematical library

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Eye Movement Measuring System Design Details -
Software

• Algorithm
• Step 1. Read data in.
• Step 2. Find nearest neighbor.
• Step 3. Find direction of acquired point in
  relation to nearest neighbor.
• Step 4. Create framing region.
• Step 5. Calculate position in framed region by
  interpolation.
• Step 6. Output position in degrees.

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Eye Movement Measuring System Design Details -
Safety

• DesignSafe
• Main Concern
• Safety of subject
• Other Concerns
• Maintenance of disease-free environment
• General workplace safety
• Proper electrical systems precautions
• Complete HTML and Excel versions available online

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Eye Movement Measuring System Material and
Manufacturing

• Hardware
• NIB Magnets 2.40
• GMR Sensors 40.00
• Versacel Plastic (Mask) 3.00
• Wires/Connectors 20.00
• AD620 or NPI Amplifier 80.00 10,000.00
• CED1401 Data Acquisition Box 7,165.00

• Software
• Spike2 1,900.00
• Matlab 460.00

Total 9,670.40 19,590.40
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Eye Movement Measuring System Material and
Manufacturing

• Overview of Manufacturing Process
• 1. Take subjects measurements
• 2. Form mask out of Versacel plastic (thermoform
  to fit monkey, drill holes for eyes, nose,
  sensors)
• 3. Solder 34 gauge magnet wires to sensors
• 4. Insert sensors into mask
• 5. Make appropriate connections/ transitions to
  connect sensors to amplifier
• 6. Connect amplifier to Power CED 1401 data
  acquisition box
• 7. Connect CED to computer to view data in Spike2

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Eye Movement Measuring System Conclusions

• Did we solve the problem?
• Future directions?
• What did we learn?
• What would we do differently?

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Eye Movement Measuring System Contact
Information

• Group 9-Eye Movement Measuring System
• Bonnie Kroll-presenter
• Anica Rothrock
• Lendy Stuber
• bmegroup_at_cec.wustl.edu
• http//userfs.cec.wustl.edu/bmegroup

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Eye Movement Measuring System Questions