Iris Edge Landmark Tracking for Eye Movement Precision

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Solution Overview

Problem

Current eye tracking technologies lack precision in monitoring eye movements, particularly for small-scale movements like micro-tremors, due to reliance on pupil center approximation which is affected by pupil size and shape changes.

Innovation Solution

Utilizing the iris edge as a fixed landmark within the eye's local coordinate system to track both large and small-scale eye movements, including micro-tremors, by digitizing and calculating the iris edge and its center, enhancing accuracy in eye tracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If pupil center approximation is used for eye tracking, then the method is simple to implement, but the measurement precision deteriorates due to pupil size and shape changes

Engineering Contradiction:

Improveease of implementationVSAvoideye position accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent extracts the iris edge as a separate reference feature from the pupil-based tracking system. By isolating the iris edge as a distinct landmark with fixed geometric properties, the system removes the problematic variable (pupil size/shape changes) while maintaining the simplicity of landmark-based tracking.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the reference parameter from pupil center coordinates (which vary with pupil size and shape) to iris edge coordinates (which maintain fixed geometric relationships). This parameter substitution resolves the accuracy issue while preserving the computational simplicity of landmark tracking.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If pupil center approximation is used, then the tracking system works for large-scale movements, but the precision for small-scale movements like micro-tremors deteriorates

Engineering Contradiction:

Improverange of motion coverageVSAvoidmicro-movement resolution

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent substitutes the mechanical approximation method (pupil center as eye center proxy) with a more precise geometric reference system (iris edge landmarks). The iris edge provides a stable geometric framework that enables detection of subtle movements without the blur and uncertainty inherent in pupil-based methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If iris edge landmarks are used for precise tracking, then the measurement precision improves, but the device complexity increases due to additional image processing requirements

Engineering Contradiction:

Improveeye position accuracyVSAvoidimage processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of trying to make the pupil adapt to changing conditions, the patent inverts the approach by using the iris edge as the stable reference and treating the pupil as the variable element. This inversion simplifies the processing logic since the iris edge provides consistent geometric constraints that are easier to detect and track than variable pupil boundaries.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS9655515B2Method of precision eye-tracking through use of iris edge based landmarks in eye geometry

Publication Date: 2017.05.23 NEUROLIGN USA LLC

AI summary

In the field of eye tracking, greater accuracy or resolution in monitoring movement of the eye can be gained by digitizing the eye, and tracking the movement of a landmark with fixed size and a fixed location relative to the eye's local coordinate system. The edge of the iris can be used as such a fixed landmark. Through the location and or establishment of at least a portion of the outer edge of the iris and/or an iris center point, both large and small scale eye movements, including but not limited to micro-tremors, can be traced with a higher degree of accuracy. This will aid in the diagnosis of diseases, assessing state of consciousness, and defining brainstem death.