Eye Tracking via Differential Retroreflection and Optical Filtering
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Solution Overview
Problem
Current eye tracking technologies for devices like smartphones and tablets are limited in their ability to accurately track eye movements and blinking states, especially when integrated into mobile devices, and often rely on complex and unreliable software that provides limited information.
Innovation Solution
The integration of multiple light sources, including LEDs emitting colored or infrared light, with a photodetector module to detect and filter retroreflected light, allowing for the determination of eye position and movement based on differential values, and processing blinking movements as input data for device functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources are used to emit light toward the eye, then measurement precision of eye position is improved, but device complexity increases
Solution Approach 1:
The system divides the light detection task into multiple wavelength channels by using multiple light sources emitting at different wavelengths. Each light source and its corresponding retroreflected light are processed separately, allowing precise determination of eye position through differential values of retroreflections from multiple sources. This segmentation enables accurate measurement while organizing complexity into manageable channels.
Solution Approach 2:
The patent applies different filtering approaches for different types of light interference: bandpass filters are used to reject background light at specific wavelength ranges, while polarizers are used to reject co-polarized light. This localized application of different filtering qualities optimizes the signal-to-noise ratio for each type of interference without unnecessarily complicating the entire system.
2Reliability
If bandpass filter and polarizer are used to filter received light, then reliability of eye tracking is improved, but device complexity increases
Solution Approach 1:
The system converts harmful background light and co-polarized light into beneficial filtering opportunities. By using bandpass filters to block background light and polarizers to reject co-polarized light, the system transforms potential interference into a structured filtering process that enhances the reliability of retroreflected light detection from the eye.
Solution Approach 2:
The patent introduces intermediary filtering components (bandpass filters and polarizers) between the light sources and the photodetector module. These intermediaries selectively transmit the desired retroreflected light while blocking unwanted background and co-polarized light, thereby improving reliability without requiring direct modification of the light sources or detectors.
3Measurement precision
If multiple light sources emitting different colors and wavelengths are used, then measurement precision is improved, but loss of energy increases
Solution Approach 1:
The system employs periodic modulation of light sources at different frequencies to enable temporal separation of signals from multiple sources. By modulating each light source at a distinct frequency and detecting the modulated retroreflected light, the system achieves precise eye position measurement while allowing efficient energy management through controlled activation patterns of the light sources.
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
This approach provides reliable and accurate eye tracking with reduced sensitivity to head movement and distance, enabling efficient control of device functions using eye movements and blinking, enhancing user interaction with mobile devices.
Implementation Method 1
At least a partial retroreflection of the light retroreflected from the eye can be received at the photodetector module
Implementation Method 2
The light sources are polarized by a polarizer
Implementation Method 3
The technique can be used to filter the received retroreflected light to reject background light and co-polarized light
Data Source
AI summary
Methods, systems, and devices are disclosed for optical sensing and tracking of eye movement. In one aspect, a method for tracking the movement of an eye includes emitting light toward an eye of a user using multiple light sources substantially equally spaced from a photodetector module of a device, receiving at the photodetector module at least a partial retroreflection of the light emitted by each of the multiple light sources retroreflected from the eye, and determining a positional parameter of the eye based on differential values of the at least partial retroreflections corresponding to the multiple light sources.