Practical Gaze Tracking
Peter Elliott
CS 498
Spring 2009
Outline
• What is gaze tracking
• Methods
• How does it work
• Current problems
• Applications
• Questions
Gaze Tracking
• Determine what a person is looking at
• Human-computer interaction
• Practical?– Need unobtrusive hardware– Don’t overload the eyes
Sclera Coil
• Contact lens with Copper wire
• Uses changes in magnetic field
http://www.skalar.nl/graphics/fig1.jpg
Sclera Coil
http://mvl.mit.edu/Neurovestibular/Pictures/Shelhamer/EyeCoilNear.jpg
Electro-oculographic Potential
• Electrodes placed on face
• Measures electric charge of the eye
http://www.sciencedaily.com/images/2008/04/080428083418.jpg
Fixed Head Position
• Similar to current technique
• Requires headrest
http://upload.wikimedia.org/wikipedia/en/f/f4/SMI_HiSpeed_EyeTracker.jpg
Finding Gaze Position
• Requires special hardware– Camera and two point light sources (IR)
• Reflections of light stay stationary on the eye
Glints
http://www.innerhealthandbeauty.net/images/Mixed_Iris.JPG
Finding Gaze Position
• Use image processing to extract ellipses of pupil and glints
• Determine 3D position of the eye
• Use geometry to map to screen coordinates
• Calibration
Problems
• Special hardware
• Eye movements
• Accuracy
• Natural feel
Hardware
http://www.tobii.com/Images/contentimages/Produktbilder/tobii-t60-eye-tracker-perspective.jpg
http://www.ecse.rpi.edu/~cvrl/zhiwei/gazetracking/SystemView.jpg
Eye Movements
• Not smooth
• Fixations and saccades
• Eye jitters
http://upload.wikimedia.org/wikipedia/en/b/b9/ReadingFixationsSaccades.jpg
Accuracy
• 16-33 pixels• ~30ms response
time
Natural Feel
• Don’t want to overload eyes
• Sensors, not used for motor control
• Must feel “natural”
• Users must feel free
• Hardware can only go so far, need software
Applications
• Market research
• Surgeons/Doctors
• Disabled users
• Able-bodied users– Future method of human-computer
interaction?
Marketing Application – Heat Maps
http://www.tobii.com/Images/contentimages/pageImages/Mag_spread_Heat_map.jpg
Summary
• How gaze position is found
• New form of human-computer interaction
• Current solutions relatively unobtrusive
• Not without problems– Cost– Accuracy
Questions?