Optical Eye Tracking via Modulated Retroreflection
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Solution Overview
Problem
Existing eye tracking technologies are limited by the need for external devices, sensitivity to head movement, and inability to be integrated into mobile devices like smartphones or tablets, providing limited and unreliable information.
Innovation Solution
The development of an optical sensing system that uses retroreflection of light from the eye to track eye movement, integrated into devices such as smartphones and computer monitors, which emits modulated light and uses a camera to capture images of the eye, determining gaze point and pupil center coordinates to control a cursor on the screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external eye tracking devices are used, then eye tracking functionality is achieved, but device complexity and integration into mobile devices is limited
Solution Approach 1:
The patent combines multiple eye tracking functionalities into a single integrated device. The system merges photodetector-based retroreflection sensing, video-based eye imaging, and screen coordinate mapping into one unified eye tracking device that can be integrated into mobile devices, eliminating the need for multiple external devices.
Solution Approach 2:
The eye tracking device performs multiple functions: it detects retroreflected light for precise eye position sensing, captures video images for eye movement tracking, and maps eye coordinates to screen coordinates. This multi-functional design allows the single device to replace multiple external devices while maintaining comprehensive eye tracking capability.
2Reliability
If traditional eye tracking methods are used, then eye position is detected, but sensitivity to head movement limits reliability
Solution Approach 1:
The patent uses screen center coordinates as an intermediary reference frame. By mapping eye pupil center coordinates to screen coordinates through a coordinate transformation system, the device creates a stable reference that is independent of head movement, allowing reliable eye tracking even when the user moves their head.
Solution Approach 2:
The system transforms the coordinate system from head-centered to screen-centered coordinates. By changing the reference parameter from head position to screen position, the system eliminates head movement sensitivity and achieves head-free eye tracking capability.
3Measurement precision
If multiple light sources are used for comprehensive eye tracking, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the light source functionality into two distinct groups: photodetector light sources for retroreflection-based precise eye position detection, and video light sources for corneal reflection-based eye movement tracking. This segmentation allows each light source group to optimize for its specific function while working together to provide comprehensive eye tracking with high measurement precision.
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
Enables reliable, head-free eye tracking that is not sensitive to head movement, allowing for one-handed operation and accurate control of device functions using eye movements, with potential applications in advertisement management and gaming.
Implementation Method 1
A photodetector module can be used to generate eye tracking signals from retroreflected lights from a user's eye corresponding to the emitted first modulated light
Implementation Method 2
A visual sensor, such as a camera, can be used to capture images of the user's eye including reflection images of the emitted second modulated 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 a first modulated light and a second modulated light toward an eye of a user, wherein the first modulated light and the second modulated light have substantially the same modulation frequency, but the modulation phases of the two modulated lights are substantially opposite to each other; receiving at a photodetector module a returned light including at least a partial retroreflected light from the eye of the user based on the first and second modulated lights; and processing the output signal from the photodetector module to determine positional and dimensional parameters of the eye of the user based at least on the partial retroreflected light corresponding to the first and second modulated lights.