Wearable Eye Movement Detection Using Differential Electrostatic Sensing
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Solution Overview
Problem
Existing eye-tracking technologies, such as electrooculography (EOG), face challenges including measurement noise from alternating electric currents, noise from head and body movements, artifacts from nearby electrical devices, and errors due to facial muscle contractions and electrode slippage.
Innovation Solution
A wearable device with a triaxial Cartesian system, including a main control circuit and two movement sensors, detects eye movements by measuring cornea-retinal potential variations using electrodes placed around the eye. This device is integrated into an optical support apparatus, such as smart glasses, to accurately track eye movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If EOG measurement technique is used to detect eye movements, then eye movement detection capability is achieved, but measurement noise and sensitivity are reduced due to environmental interference and physiological artifacts
Solution Approach 1:
The patent introduces an intermediary processing system that includes a reference electrode and signal processing circuitry. The reference electrode captures environmental electrical interference (power line noise at 50/60 Hz), and this reference signal is used to subtract the interference from the measurement electrodes' signals, thereby eliminating the harmful environmental factors while preserving the eye movement detection capability
Solution Approach 2:
The patent implements feedback through a multi-electrode configuration where signals from multiple electrodes are continuously monitored and processed. The system uses feedback loops in the signal processing circuitry to detect and compensate for artifacts from facial muscle contractions and electrode slippage, maintaining measurement precision despite these interfering factors
2Measurement precision
If multiple electrodes are placed around the eye for EOG measurement, then eye movement detection coverage is improved, but device complexity and ease of operation are reduced due to electrode placement and maintenance requirements
Solution Approach 1:
The patent designs the electrode system with multi-functionality where a standardized set of electrodes serves multiple purposes: detecting horizontal eye movements, vertical eye movements, and providing reference signals for interference rejection. This universal electrode configuration reduces the need for complex specialized electrode arrangements while maintaining comprehensive eye movement detection capability
Solution Approach 2:
The patent segments the measurement system into functionally distinct electrode groups (measurement electrodes and reference electrodes) that can be independently optimized. This segmentation allows the reference electrodes to be positioned specifically for capturing environmental interference while measurement electrodes focus on eye movement detection, simplifying the overall configuration and placement procedure
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
The wearable device effectively reduces measurement noise and improves sensitivity by using differential measurement techniques and inertial sensors to account for head movements, resulting in more accurate eye movement detection.
Implementation Method 1
electrooculography (EOG) is a technique to measure the cornea-retinal potential (CRP) that exists between the front portion (e.g., including the cornea) and the back portion (e.g., including the retina) of the human eye. The eye acts as an electric dipole where the front pole at the cornea is positive and the back pole at the retina is negative.
Implementation Method 2
two movement sensors, which are configured to detect head movements of the user and generate inertial signals indicative of the head movements
Data Source
AI summary
A wearable device for detecting a user's eye movement having a first movement sensor with electrodes aligned with each other along a first movement axis, a second movement sensor with electrodes aligned with each other along a second movement axis transverse to the first movement axis, and a control circuit coupled to the electrodes and configured to acquire electrostatic charge variation signals indicative of differences between the electrostatic charge variations detected by the electrodes of the movement sensors; detect an event indicative of respective displacements of the eyes along the movement axis; and determine the movement of the eyes based on of the event confirmation.