Eye Position Tracking via Light Pattern Triangulation
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Solution Overview
Problem
Current eye-tracking systems fail to accurately determine the eye position and viewing direction, particularly in medical applications like laser surgery, due to the challenge of accounting for rapid eye movements and tilting, which leads to positional errors and potential complications such as ametropia.
Innovation Solution
A method and device that project a light pattern onto the eye's surface, using triangulation or stereo vision to determine the spatial coordinates of points at the transition region between the sclera and iris, allowing for precise calculation of the iris plane's position and tilting, without requiring objects on the eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional eye-tracking methods are used to determine eye position, then the system can provide basic pupil tracking, but it fails to accurately account for rapid eye movements and tilting, leading to positional errors
Solution Approach 1:
The patent transitions from 2D pupil tracking to 3D eye position determination by adding depth measurement capability. This is achieved by projecting light patterns onto the eye surface and using triangulation to calculate the third dimension (depth), enabling accurate tracking of eye tilting and rapid movements that conventional 2D methods cannot capture.
Solution Approach 2:
The patent introduces light patterns as an intermediary element projected onto the eye surface. These patterns serve as reference markers that enable the measurement system to track eye position and orientation changes. The light patterns act as a mediator between the eye and the sensor, allowing precise determination of eye movements without direct contact.
2Measurement precision
If markers or objects are placed on the eye to track position, then measurement accuracy can be improved, but the device complexity and invasiveness increase
Solution Approach 1:
The patent makes the eye surface itself serve as the measurement reference by utilizing its natural curvature and structure. The light patterns projected onto the eye interact with the eye's own surface geometry, eliminating the need for external markers or objects. The eye's surface features become the measurement markers through the interaction with projected light.
Solution Approach 2:
The patent uses light patterns with specific optical properties that interact with the eye surface. By analyzing how these light patterns reflect off or are absorbed by different parts of the eye surface, the system can determine eye position and orientation without physical markers. The optical contrast created by the light patterns provides the necessary measurement information.
3Productivity
If high shot frequencies are used during laser surgery to treat rapid eye movements, then treatment speed is improved, but positional errors increase due to eye tilting
Solution Approach 1:
The patent enables continuous real-time monitoring of eye position and orientation during laser treatment. By continuously tracking the light patterns on the eye surface at high frame rates, the system maintains up-to-date knowledge of eye position, allowing the laser system to adjust and compensate for movements continuously throughout the treatment process.
Solution Approach 2:
The patent implements a feedback loop where eye position and orientation are continuously measured using light pattern tracking, and this information is fed back to control the laser system. The real-time feedback allows dynamic adjustment of laser parameters and positioning to compensate for rapid eye movements and tilting, maintaining treatment precision despite high shot frequencies.
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 quick and accurate determination of eye position, viewing direction, and tilting, reducing decentering errors and ensuring precise laser ablation during surgery, even at high shot frequencies.
Implementation Method 1
spatial coordinates of points at which the light pattern intersects with the transition region between sclera and iris are determined by triangulation or by stereo vision
Implementation Method 2
a light pattern on a surface of the eye is projected and imaged there, the light pattern intersecting the transition region between sclera and iris
Data Source
Figure 1
Figure 2~3
Figure 4a~4b
AI summary
The invention relates to a method and device for determining eye position, wherein a light pattern is produced on the surface of an eye (11) by means of a light source (10a) and an image of the light pattern produced on the eye (11) is recorded by means of an image recording apparatus (12), wherein points of the transition region between the sclera and the iris of the eye are determined from the image of the light pattern by means of an image processing apparatus (14). The coordinates of the calculated points are calculated by triangulation or stereovision, and the position of the iris plane or a plane oriented parallel thereto is determined from said coordinates. The limbus of the eye and the center thereof can also be determined in three dimensions.