Eye Position Tracking via Projected Iris Patterns
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Solution Overview
Problem
Current methods for determining the position and attitude of the eye during refractive surgery, such as laser ablation of the cornea, face challenges in accurately accounting for eye movements and variations in eye orientation, particularly in capturing precise spatial and rotational angles.
Innovation Solution
The method involves projecting linear structures onto the iris, capturing images with a camera aligned with the eye, and using image processing techniques like Hough or Fourier transformations to determine the position and orientation of these structures, which are then used to infer the position of the cornea, allowing for more precise laser treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If natural structures on the eye surface are used for image processing, then the determination of eye position and orientation can be performed, but the image processing becomes complex and less precise due to variable and unpredictable geometry
Solution Approach 1:
The patent introduces linear structures as an intermediary element projected onto the iris surface. These structures serve as a mediator between the imaging system and the eye, providing known geometric references that simplify the image processing algorithm while improving measurement precision for eye position and orientation determination
Solution Approach 2:
The patent changes the geometric parameters of the reference structures from natural, variable iris patterns to standardized linear structures with predictable geometry. This parameter change transforms the image processing from dealing with complex, variable natural structures to analyzing simple, well-defined linear patterns, thereby reducing computational complexity while enhancing measurement accuracy
2Measurement precision
If linear structures are projected onto the iris, then image processing is simplified and measurement precision is improved, but additional equipment and processing steps are required
Solution Approach 1:
The patent makes the projection system a universal component that serves multiple functions: it provides illumination, creates reference linear structures for measurement, and enables both 2D and 3D eye position/orientation determination. This multi-functionality justifies the added device complexity by consolidating multiple measurement capabilities into a single integrated system
3Loss of information
If multiple images are captured to determine all eye parameters, then complete eye position and orientation information is obtained, but the measurement time increases
Solution Approach 1:
The patent performs preliminary action by projecting linear structures onto the iris before the actual measurement is taken. This pre-projection establishes known reference patterns that enable all necessary eye parameters (position and orientation) to be determined from a single image capture, eliminating the need for multiple sequential images and reducing measurement time
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 approach provides more accurate and reliable determination of eye position and orientation, enabling precise laser ablation of the cornea by simplifying image processing and improving the detection of features, thus enhancing the precision and effectiveness of refractive surgery.
Implementation Method 1
Linear structures are generated onto the iris of the eye, for example by projection
Implementation Method 2
A first image of the eye with the linear structures on it is captured using a camera
Data Source
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AI summary
The invention relates to a method for determining parameters for the position and orientation of the cornea of an eye and involves the steps of generating linear structures on the iris and/or sclera of the eye, having a camera capture a first image of the eye including the linear structures, and determining, on the basis of the first image, a distance and an orientation of the linear structures in relation to the camera.