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Contents• Introduction

• Current Techniques

• Eye Tracking system

• Methods of Measuring

• Applications

• Advantages

• Limitations

• Conclusion

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Current Interfacing Techniques

• Normal Interface

• Touch Screen

• Voice

• Wave

• Eye movement

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The Eye

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• Cornea is a transparentstructure that covers the iris andpupil; a part of the focusingsystem of an eye.

• Pupil is the adjustable openingat the center of the iris thatallows varying amounts of lightto enter the eye.

• Lens helps to focus light on the retina.

• Retina includes rods (94%),which are sensitive to light andcones (6%) that capture colors.Cones are concentrated in thecentre of the retina - the fovea

Vision Field

• Vision field is divided in to three regions

o Fovea provides the sharpest vision

o Parafovea previews foveal information

o Peripheral vision reacts to flashing objects and sudden movements

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Types of Eye Movements• Fixation

• Saccade

• Pursuit

• Tremor

• Rotation

• Drift

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Methods for Measuring Eye Movements

• Electronic

• Mechanical

• Optical/Video o Single point

o Two point

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Electronic Method

• The most used method is to place skin electrodes around the eyesand measure the potential differences in eye

• Wide range -- poor accuracy

• Better for relative than absolute eye movements

• Mainly used in neurological diagnosis

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Mechanical Method• Based on contact lenses

with

o mirror planes + reflecting

IR-light

o coil + magnetic field

• Very accurate

• Very uncomfortable for

users who are not used to

wear lenses

o Usable only for lab

studies

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Optical/Video based Method-single point

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• Tracking one visible feature of the eyeball, e.g.:

o limbus (bondary of sclera and iris)

o pupil

• A video camera observes one of the user's eyes

• Image processing software analyzes the video image and traces the tracked feature

• Based on calibration, the system determines where the user is currently looking

• Head movements not allowed

o Bite bar or head rest is needed

Optical/Video based Method-two point

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• The same idea as in the single point

method except now two features of

eye are tracked – typically

o corneal reflection

o pupil

• Uses IR light (invisible to human eye)

to

o produce corneal reflection

o cause bright or dark pupil, which

helps the system to recognize pupil

from video image

Bright pupil

Corneal reflection

Eye Tracking System

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Corneal reflection plus pupil eye tracker

Cont…

• Corneal reflection plus pupil eye tracker

• The pupil camera and illuminator operate along the

same optical axis

• Servo controlled mirror is used to compensate for

the user’s head motions.

• tracks the corneal reflection from an infrared light

shining on eye and the outline of the pupil

illuminated by same light.

• Computes the visual line of eye gaze by relationship

between two tracked points.

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Applications

• Automated drug screening.

• Retail advertising effectiveness.

• Surgical Training

• Training and simulation

• Vision Research

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Advantages

• Eye movement is faster than other current input

media.

• No training or particular coordination is required of

normal users.

• Can determine where the user’s interest is focused

automatically.

• Helpful for usability studies to understand users

interact with their environments.

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Limitations• Equipment is expensive

• Some users can't work with the equipment (if they

wear contact lenses or have long eye lashes)

• Moving one's eyes is often an almost subconscious

act.

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Conclusion

• Emerging Interaction Technique

• Eye tracking is far from “perfect”

• show the intensity of the user’s attention

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Any Questions..

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Thank You

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