Gaze Point Detection With Off-Axis Pupil Center Correction
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Solution Overview
Problem
Conventional off-axis sight line detection systems in cameras and head-mounted displays suffer from distortion in the image of the eyeball due to perspective, making it difficult to accurately determine the pupil center, which affects the precision of gaze point detection.
Innovation Solution
A detection device that includes a sight line detector, a processor, and a control method to accurately detect the pupil center by correcting for distortion using the angle between the optical axis and the sight line, considering the pupil diameter and corneal refraction, to enhance gaze point detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If off-axis sight line detection is used, then the sight line sensor can be arranged at an oblique lower side of the user's eyeball to simplify the optical system, but the image of the eyeball becomes distorted due to perspective influence
Solution Approach 1:
The patent applies parameter changes by calculating a correction value based on the angle between the optical axis and the sight line direction. This correction value is then used to adjust the detected pupil center position, transforming the distorted measurement into an accurate one. The correction value is derived from trigonometric relationships involving the angle θ and the distance between the pupil center and corneal reflection point, allowing the system to compensate for perspective distortion while maintaining the simplified off-axis optical configuration.
2Device complexity
If the shape of the pupil is approximated to an ellipse to find the pupil center coordinate, then the detection process becomes simpler, but the ellipse is still affected by perspective distortion making accurate pupil center detection difficult
Solution Approach 1:
The patent introduces an intermediary correction mechanism that uses the corneal reflection point as a reference. Instead of directly working with the distorted ellipse, the system calculates the position of the corneal reflection point (which serves as a stable reference), determines the angle between the optical axis and sight line, and uses this information to compute a correction value. This correction value is then applied to the detected pupil center position, effectively mediating between the simplified detection process and the need for 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 precise detection of the actual pupil center and gaze point even in off-axis configurations, improving the accuracy of sight line detection in devices with off-axis optical systems.
Implementation Method 1
a sight line sensor of the sight-line detection optical system is arranged at an oblique lower side of a user's eyeball. Then, when the sight line is detected, the sight line sensor picks up an image of the user's eyeball from the oblique lower side
Implementation Method 2
a corneal reflection image formed by a cornea and a sight line detection optical system
Data Source
AI summary
A detection device capable of detecting an actual pupil center with high accuracy even in an off-axis sight line detection. The detection device includes an obtainment unit configured to obtain an image of an eyeball of a user, a memory device that stores a set of instructions, and at least one processor that executes the set of instructions to: detect a position of a pupil center of the eyeball from an image obtained by the obtainment unit, detect a direction of a sight line based on the position of the pupil center, and detect a gaze point of the user based on the position of the pupil center and an angle formed between an optical axis of the obtainment unit and the direction of the sight line.