Development of an Eye Tracker By Jason Kajon Barrett of the Center for Imaging Science at the Rochester Institute of Technology Advisor: Jeff Pelz

What is an Eye Tracker? A device used to detect eye motion. A device used to detect eye motion. What are they for ? Access for the physically handicapped,Access for the physically handicapped, target variable resolution, target variable resolution, realistic virtual reality environments, realistic virtual reality environments, and increased bandwidth of human-computer interaction. Shannon’s Rule: C = BW log 2 (1 + S/N) and increased bandwidth of human-computer interaction. Shannon’s Rule: C = BW log 2 (1 + S/N)

Types of Trackers: Types of Trackers: mechanical- corneal cover mechanical- corneal cover magnetic- eyeball polarity magnetic- eyeball polarity electric- EMG & EOG electric- EMG & EOG optical- IR illumination optical- IR illumination

What is the Research Design? A device using four IR photodetectors and a microcontroller to detect the onset of rapid eye motion. A PicBasic program to run this device. A device using four IR photodetectors and a microcontroller to detect the onset of rapid eye motion. A PicBasic program to run this device.

Why a microcontroller ? Simple data manipulation, Simple data manipulation, lookup table, lookup table, single upgradable chip, single upgradable chip, cost for device, cost for device, and ease burden on CPU. and ease burden on CPU.

Targets for the Research 500 Hz Sampling Rate 500 Hz Sampling Rate < $300 Project Expense < $300 Project Expense < 4 Degrees Accuracy < 4 Degrees Accuracy

Initial Budget Microcontroller and instructions$ 25Microcontroller and instructions$ 25 Crystal$ 2Crystal$ 2 Power Supply$110Power Supply$110 Comparator$ 7Comparator$ 7 Diff. OP-AMP$ 5Diff. OP-AMP$ 5 Potentiometers$ 20Potentiometers$ 20 IR Emitters$ 67IR Emitters$ 67 IR Detectors $ 45IR Detectors $ 45 Total$281Total$281

Targets for the Research 500 Hz Sampling Rate 500 Hz Sampling Rate < $300 Project Expense < $300 Project Expense < 4 Degrees Accuracy < 4 Degrees Accuracy

Why 500 Hz ? Saccades rapid eye movementsSaccades- rapid eye movements last ms,last ms, cannot be within 100 ms of eachothercannot be within 100 ms of eachother video eye tracking unit at 60 Hz (i.e. 17 ms, half a short saccade.)video eye tracking unit at 60 Hz (i.e. 17 ms, half a short saccade.)

For a 20 MHz PIC16C74A/JW-ND processor Sampling Rate 200  sec / instruction200  sec / instruction 200 instructions200 instructions 40  sec for sample40  sec for sample 50 kHz sample rate50 kHz sample rate

For a 10 MHz PIC16C84 processor Sampling Rate 20  sec / instruction20  sec / instruction 100 instructions100 instructions 2 msec for sample2 msec for sample 500 Hz sample rate500 Hz sample rate

Targets for the Research 500 Hz Sampling Rate 500 Hz Sampling Rate < $300 Project Expense < $300 Project Expense < 4 Degrees Accuracy < 4 Degrees Accuracy

The fovea covers approximately a 1 0 Field of View. Video eye trackers can come to within 1/2 0 for field of view. The main consideration is speed. The fovea covers approximately a 1 0 Field of View. Video eye trackers can come to within 1/2 0 for field of view. The main consideration is speed. Why 4 Degrees?

To get within 4 Degrees: individual calibration will be necessaryindividual calibration will be necessary extensive lookup table creationextensive lookup table creation consecutive ON/OFF state comparison ( provided for by software )consecutive ON/OFF state comparison ( provided for by software )

Sample Calibration Target (with Nine Targets) (with Nine Targets)

Sample Calibration Target (with Seventeen Targets) (with Seventeen Targets)

The Proposed Design ASL Model 210 Eye Movement MonitorASL Model 210 Eye Movement Monitor made from scratch made from scratch single eye measurementsingle eye measurement fit within HMDfit within HMD

Horizontal+ _ Vertical | ? | ASL model 210 eye movement monitor

Horizontal Measurement + _ Negative measurement = leftNegative measurement = left Positive measurement = rightPositive measurement = right

Detector Positions as the Viewer Shifts Their Horizontal Gaze Right Right Center Center Left Left

Vertical Measurement | ? | High measurement = upHigh measurement = up Low measurement = downLow measurement = down

Detector Positions as the Viewer Shifts Their Vertical Gaze Up Up Center Center Down Down

ASL video eye tracker

Long-term Goals of the Research Use in future projects involving eye contingent updating and the study of perception.Use in future projects involving eye contingent updating and the study of perception. Measurement of saccadic eye movements. Measurement of saccadic eye movements.

Conclusions The eye tracker proposed is possible for the proposed expense as there is an adequate sacrifice for accuracy of eye position to increase the speed. The eye tracker proposed is possible for the proposed expense as there is an adequate sacrifice for accuracy of eye position to increase the speed. The resultant code written in PicBasic will satisfy the design proposed. The resultant code written in PicBasic will satisfy the design proposed.