SMI Eye Tracking for Low-Power High-Speed Gaze Detection

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Solution Overview

Problem

Existing eye tracking technologies, particularly camera-based systems, face challenges in achieving fast and accurate eye movement detection with low power consumption, which is crucial for next-generation head-mounted displays and augmented/virtual reality systems.

Innovation Solution

Utilizing self-mixing interferometry (SMI) sensors to track eye movement, either alone or in combination with cameras, for high-speed and low-power gaze vector determination, enabling precise detection of eye movements such as smooth pursuit, saccade, fixation, and blinking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If camera-based eye tracking is used, then eye movement detection can be achieved, but power consumption increases significantly

Engineering Contradiction:

Improveeye movement detection accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the mechanical/optical camera system with a self-mixing interferometry sensor that uses optical interference patterns to detect eye movements. This substitution eliminates the need for active illumination and image processing, achieving the same measurement function with significantly lower power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The SMI sensor uses the eye itself as the light source through reflective interference patterns. The sensor detects eye movements by measuring changes in the interference pattern generated by light reflecting off the eye surface, eliminating the need for external illumination sources and reducing power requirements.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If camera-based eye tracking is used, then eye position can be determined, but computational cost increases

Engineering Contradiction:

Improvegaze vector determination accuracyVSAvoidcomputational cost

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex image processing algorithms with optical interference pattern analysis. Instead of processing multiple images to determine eye position, the system uses interferometric measurements that directly provide gaze vector information with minimal computational processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts the essential eye movement information directly from the interference pattern signal, eliminating the need for complex image processing steps such as pupil detection, corneal reflection analysis, and feature extraction that are required in camera-based systems.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If camera-based eye tracking is used, then eye movements can be tracked, but latency increases

Engineering Contradiction:

Improveeye movement tracking speedVSAvoidlatency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The SMI sensor continuously measures interference patterns in real-time as the eye moves, providing continuous gaze vector data without the discrete sampling and processing delays inherent in camera-based systems. This continuous measurement approach eliminates latency and enables real-time eye tracking.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent replaces the sequential image capture and processing pipeline with simultaneous optical measurement. The interferometric sensor measures eye movement effects directly in the optical domain without requiring discrete image frames, achieving real-time tracking with minimal latency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

SMI sensors provide high accuracy and low power consumption for eye tracking, allowing for efficient and precise rendering of digital content in near-eye displays by detecting subtle eye movements with minimal power usage.

Implementation Method 1

utilize one or more self-mixing interferometry (SMI) sensors to track eye movement

Methodology Applied

Scientific EffectSelf-mixing interferometry: Interference

Implementation Method 2

emit a set of one or more beams of light toward an eye of a user; to receive a set of one or more SMI signals from the set of one or more SMI sensors

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS12541100B2Eye tracking using self-mixing interferometry

Publication Date: 2026.02.03 APPLE INC

AI summary

An eye tracking device includes a head-mountable frame, an optical sensor subsystem mounted to the head-mountable frame, and a processor. The optical sensor subsystem includes a set of one or more SMI sensors. The processor is configured to operate the optical sensor subsystem to cause the set of one or more SMI sensors to emit a set of one or more beams of light toward an eye of a user; to receive a set of one or more SMI signals from the set of one or more SMI sensors; and to track a movement of the eye using the set of one or more SMI signals.