Eye-Tracking Optics for Corneal Reflection Coordinate Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing line-of-sight measurement devices face challenges in accurately obtaining image coordinates of the corneal reflection image and pupil center due to difficulties in distinguishing between disturbance light reflected on glasses and corneal reflection, requiring multiple light sources and complex configurations, leading to increased costs.
Innovation Solution
A line-of-sight measurement device with a simple configuration that uses a single imaging unit and light illumination unit arranged coaxially, employing a corneal reflection method to estimate three-dimensional coordinates of the corneal reflection image and pupil center, incorporating a computer system for image processing to calculate optical axis vectors and image coordinates with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources or changing projection patterns are used to distinguish corneal reflection from glass reflection, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent employs periodic action by sequentially activating multiple light sources at different time points. The controller drives each light source (first, second, third light sources) to emit light in sequence, capturing images at each stage. This temporal separation allows the system to distinguish corneal reflection images from glass reflection images by comparing images taken at different times, achieving accurate measurement without requiring all light sources to be active simultaneously, thus reducing device complexity while maintaining precision.
2Measurement precision
If multiple light sources are used to obtain corneal reflection image, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs periodic action by sequentially activating multiple light sources at different time points. The controller drives each light source (first, second, third light sources) to emit light in sequence, capturing images at each stage. This temporal separation allows the system to distinguish corneal reflection images from glass reflection images by comparing images taken at different times, achieving accurate measurement without requiring all light sources to be active simultaneously, thus reducing device complexity while maintaining precision.
Solution Approach 2:
The patent applies self-service by using the existing camera and image processing capabilities to automatically distinguish between corneal reflection and glass reflection. The controller automatically compares images taken with different light sources and identifies the corneal reflection image based on characteristic features, eliminating the need for additional specialized hardware or manual intervention, thereby reducing manufacturing costs while maintaining high measurement precision.
3Device complexity
If a single light source is used, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish corneal reflection from glass reflection
Solution Approach 1:
The patent employs periodic action by sequentially activating multiple light sources at different time points. The controller drives each light source (first, second, third light sources) to emit light in sequence, capturing images at each stage. This temporal separation allows the system to distinguish corneal reflection images from glass reflection images by comparing images taken at different times, achieving accurate measurement without requiring all light sources to be active simultaneously, thus reducing device complexity while maintaining precision.
Solution Approach 2:
The patent applies copying by creating multiple virtual light sources through sequential activation of physical light sources. The system captures multiple images with different light sources and processes them to generate the equivalent information that would be obtained from multiple simultaneous light sources. This allows the system to achieve the measurement precision of a complex multi-light-source system while using a simpler sequential activation approach, effectively copying the functional outcome without the full hardware complexity.
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 accurate determination of image coordinates of the corneal reflection image and pupil center, facilitating precise line-of-sight measurement without additional hardware, thereby reducing costs and complexity.
Implementation Method 1
A method of using an image obtained by reflection from the front surface of the cornea is a corneal reflection method
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A line-of-sight measurement device (10) includes: an imaging unit (12) that images a face of a subject; a light illumination unit (13) that illuminates light to an eye of the subject; a camera coordinate system eyeball center coordinate calculation unit (30) that estimates coordinates of an eyeball center, from a face image imaged by the imaging unit; a pupil center calculation unit (32) that estimates coordinates of an apparent pupil center, from a pupil center position on the face image; an eyeball position orientation estimation unit (36) that calculates an optical axis vector toward the pupil center from the eyeball center on the basis of the coordinates of the eyeball center and the apparent pupil center; a corneal reflection image calculation unit (40) that obtains coordinates of a corneal reflection image on the basis of the coordinates of the eyeball center, the optical axis vector, and a predetermined eyeball model; and an image coordinate calculation unit (42) that estimates image coordinates of a corneal reflection image on the face image, from the coordinates of the corneal reflection image.