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?