Mobile eye tracker construction and gaze path analysis By Wen-Hung Liao 廖文宏

Outline Introduction Application areas State-of-the-art technology Mobile eye tracker construction Pupil detection and tracking Validation Human computer interface (HCI) applications Gaze path analysis Conclusions

Introduction An eye tracker is a device for measuring eye positions and eye movements.eye movements The most popular variant uses video images from which the eye position is extracted. Input source: visible spectrum vs. infrared

Eye Movements Eye movements are typically divided into fixations (when the eye gaze pauses in a certain position) and saccades (when it moves to another position). Eye movements The resulting series of fixations and saccades is called a scanpath.scanpath

Web Design (U. of Manchester) Heat mapGaze plot

Usability Study: Google Search Evaluation

Gaming

Driving Behavior [Andrew T. Duchowski]

Human-Computer Interface EyeWrite [Andrew T. Duchowski]

Media Research The Poynter Institute : Published first eye track study in More results published in 2000, 2004 and Eyetrack ’07: asp?id= asp?id=105035

Research Communities ACM SIG/CHI Eye Tracking Research and Applications (ETRA) Symposium: COGAIN: Communication by Gaze Interaction References:

State-of-the-art Eye tracking Technology Hi-Speed (SMI iView X™ Hi-Speed) Head-Mounted System Remote tracking Integrated with LCD monitor

Mobile Eye NCCUCS eye camera scene camera

Key Objectives Low-cost (NTD 10,000 vs. 1,000,000) Mobility Easily customized for specific applications Sampling rate? On-line or off-line processing? Accuracy?

System Architecture Eye image Preprocessing Pupil detection Gaze point projection Scene image Calibration 9 pairs of points Calibration process

Pupil Detection (I): extracting feature points

Pupil Detection (II): Ellipse fitting using RANSAC

Pupil Detection (III): checking fitness measure Ellipse model: Number of bright vs. dark points inside and out the perimeter

Results

Another Approach Capture eye image using infrared camera Threshold-based method Pupil Iris

Illustrations

Calibration Process

Validation Procedure

Validation Results Starburst (pixels) Starburst + fitness check (pixels) Threshold-based (pixels) Subject Subject Subject Average error *Resolution: 1024x768

HCI Application: Eye Scrolling

HCI Application: Eye Gaming

HCI Application: Eye Typing

Dynamic Scene

Gaze Path Analysis Recursive intersection Find the similarity between two scan paths Order of scanning is irrelevant Suitable for processing fixation data Modified dynamic time warping Order of scanning is taken into account Can handle both fixation and saccade data

Recursive Intersection Path 2 Path 1

Recursive Intersection: Example

Dynamic Time Warping (DTW)

Modified DTW (MDTW) X-axis Y-axis time

MDTW Result

Summary Low cost eye tracker construction Low cost ($10,000 NTD) Head-mount with mobile functionality HCI applications Sampling rate: depending on the camera’s frame rate Accuracy: suitable for some HCI applications, image viewing tasks, not high enough for reading. Gaze path analysis