Eye-Tracking Camera Layout to Avoid Eyelid Light Shielding
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Solution Overview
Problem
Existing visual line detecting apparatuses face challenges in accurately detecting visual line directions due to light shielding issues caused by the three-dimensional structure of the eye, particularly the eyelids, and are often hindered by the need for parallel imaging axes that increase device thickness or result in mirror image relationships leading to incomplete detection.
Innovation Solution
The apparatus employs a non-mirror image arrangement of right-eye and left-eye illumination elements and cameras, with different imaging directions and vertical positions, to independently capture visual line directions of both eyes, reducing light shielding effects and enhancing detection probability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the display optical system and camera are aligned with the imaging optical axis direction, then the imaging precision is improved, but the HMD becomes thicker in the imaging optical axis direction
Solution Approach 1:
The patent applies asymmetry by positioning the right-eye camera and left-eye camera at different vertical positions relative to their respective eyes, rather than using a symmetric mirror-image arrangement. Specifically, the right-eye camera is positioned at a first vertical position while the left-eye camera is positioned at a second vertical position that differs from the first, breaking the symmetry to reduce light shielding from eyelids while maintaining imaging precision.
Solution Approach 2:
The patent introduces vertical position differentiation as an additional degree of freedom in the camera arrangement. By varying the vertical positions of the cameras relative to the eyes in addition to their lateral positions, the system achieves better detection performance without increasing the forward thickness of the HMD, effectively utilizing the vertical dimension to resolve the contradiction.
2Length of moving object
If eyeballs are imaged from oblique directions to reduce HMD thickness, then the device compactness is improved, but light shielding from eyelids prevents accurate visual line detection
Solution Approach 1:
The patent uses asymmetry to differentiate the vertical positions of the right-eye and left-eye cameras, creating non-mirror-image arrangements that avoid simultaneous light shielding from both eyelids. This asymmetric positioning ensures that when one eye's detection is blocked, the other eye's detection remains available, maintaining visual line detection accuracy while using oblique imaging directions.
Solution Approach 2:
The patent changes the positional parameters of the cameras, specifically the vertical positions, to optimize the imaging angles. By adjusting these parameters, the system achieves oblique imaging directions that reduce HMD thickness while minimizing light shielding effects from eyelids, thereby maintaining detection accuracy.
3Stability of the object's composition
If mirror image relationship is used for right and left eyeball detection, then the detection symmetry is improved, but light shielding conditions cause both eyes to fail detection simultaneously
Solution Approach 1:
The patent deliberately breaks the mirror-image symmetry by positioning the right-eye camera and left-eye camera at different vertical positions. This asymmetric arrangement ensures that the light shielding conditions for the two eyes are not identical, so when one eye's detection is blocked by its eyelid, the other eye's detection is likely to succeed, thereby improving overall detection reliability while maintaining reasonable symmetry in the detection system.
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 arrangement increases the likelihood of detecting visual line directions on at least one eye side by accounting for three-dimensional eye structures and varying visual line directions, even in cases where light shielding occurs, thereby improving detection accuracy and reducing the number of required illumination elements.
Implementation Method 1
detects the visual line directions of the left and right eyes by capturing images formed by reflected lights from corneas with left and right cameras
Data Source
AI summary
A visual line detecting apparatus includes a plurality of right-eye illumination elements, a plurality of left-eye illumination elements, a right-eye camera configured to capture an image formed by light reflected by the right eye, out of the lights from the plurality of right-eye illumination elements, and a left-eye camera configured to capture an image formed by light reflected by the left eye, out of the lights from the plurality of left-eye illumination elements. An imaging direction of the right-eye camera and an imaging direction of the left-eye camera are different from each other and a position of the right-eye camera relative to the right eye and a position of the left-eye camera relative to the left eye are different from each other in a vertical direction orthogonal to a lateral direction in which the right eye and the left eye are arranged.