Line-of-Sight Detection Using Adaptive Pupil and Iris Edge Processing
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Solution Overview
Problem
Existing line-of-sight detection methods face challenges in accurately detecting the center of the pupil, particularly in bright and semi-bright pupil states due to reduced brightness differences between the pupil and iris, leading to difficulties in distinguishing the pupil outline and reduced detection accuracy.
Innovation Solution
A line-of-sight detection method that switches processing based on edge detection results, using either the pupil or iris outline detection depending on the presence of edges between the pupil and iris, to accurately determine the pupil center, thereby improving detection accuracy across various lighting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the distance between the illuminating light source and the camera is small, then the illumination intensity is sufficient, but the pupil becomes bright due to retinal reflection, making it difficult to detect the corneal reflection and pupil center
Solution Approach 1:
The system changes the parameter of illumination wavelength by using infrared light instead of visible light. This allows the illuminating light source to be positioned close to the camera (improving illumination intensity) while the infrared illumination does not cause the pupil to appear bright in the captured image, thereby maintaining pupil center detection accuracy
Solution Approach 2:
The patent introduces an infrared bandpass filter as an intermediary component that selectively transmits infrared light while blocking visible light. This filter allows the system to use infrared illumination close to the camera without the visible light effects that cause pupil brightness, thus resolving the contradiction between illumination intensity and detection accuracy
2Measurement precision
If the distance between the illuminating light source and the camera is increased, then the pupil brightness is reduced, but the illumination intensity decreases, making it difficult to capture clear eye images
Solution Approach 1:
By changing the illumination wavelength to infrared, the system can maintain close positioning between the light source and camera, thereby preserving high illumination intensity while avoiding the pupil brightness problem that would occur with visible light at increased distances
3Measurement precision
If the outline of the pupil is used for detection, then the detection accuracy is high in normal states, but the brightness difference between pupil and iris is reduced in bright pupil states, making it difficult to detect the pupil outline
Solution Approach 1:
The patent changes the wavelength parameter of the illumination light to infrared, which fundamentally alters the interaction with ocular tissues. Infrared illumination does not cause the pupil to appear bright, thereby maintaining the brightness difference between pupil and iris even when the light source is positioned close to the camera. This ensures reliable pupil outline detection across all operating conditions
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 method enhances the accuracy of pupil center detection even in challenging conditions by adaptively selecting the appropriate detection processing based on edge detection outcomes, effectively addressing the limitations of existing methods.
Implementation Method 1
an image in which a face of a user is captured by an infrared camera is obtained; detect edge portions in the obtained image, in which the edge portions are based on a difference in brightness
Implementation Method 2
an image in which a face of a user is captured by an infrared camera is obtained
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A line-of-sight detection method includes detecting an eye region of a subject from an image, determining whether a position of a boundary between a pupil and an iris is detected from the image based on a brightness change in the eye region, executing, in accordance with a result of the determining, at least one of first processing in which a position of a center of the pupil is detected based on an outline of the pupil and second processing in which the position of the center of the pupil is detected based on another outline of the iris, and detecting a line of sight of the subject based on the position of the center of the pupil detected by the at least one of the first processing and the second processing.