Wavefront Aberration Measurement Using Multilayer Eye Model
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Solution Overview
Problem
Conventional wavefront reconstruction algorithms for ophthalmic aberrometry introduce errors due to inaccurate focal light spot distributions and assumptions of single-layer reflection, leading to spurious aberrations and reduced measurement accuracy.
Innovation Solution
A method employing a multilayer eye model and second moment descriptors to optimize wavefront coefficient data and optical parameters, accounting for multiple reflective layers and improving image quality by reducing noise and artifacts in wavefront sensing data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional wavefront reconstruction algorithms assume single-layer reflection, then the algorithm complexity is reduced, but measurement precision deteriorates due to spurious aberrations
Solution Approach 1:
The patent segments the retina into multiple reflective layers (at least two layers: first reflective layer and second reflective layer) instead of assuming a single layer. This segmentation allows the algorithm to separately process and analyze light reflections from different retinal layers, thereby eliminating spurious aberrations caused by the single-layer assumption while maintaining manageable algorithm complexity through structured layer-by-layer processing.
2Productivity
If conventional algorithms process focus light spot data directly, then processing speed is maintained, but measurement precision deteriorates due to noise and artifacts
Solution Approach 1:
The patent applies preliminary action by performing optimization processing on the focus light spot data before wavefront reconstruction. The method optimizes both the wavefront coefficient data and the optical parameters (such as axial separation between reflective layers) simultaneously in a pre-processing stage. This preliminary optimization eliminates noise and artifacts from the data before reconstruction, improving measurement precision without significantly impacting processing speed because the optimization is integrated into the reconstruction workflow.
3Device complexity
If the axial separation between reflective layers is not optimized, then the calculation complexity is reduced, but measurement precision deteriorates due to unknown layer positions
Solution Approach 1:
The patent applies parameter changes by treating the axial separation between reflective layers as an optimizable parameter rather than a fixed known value. The method simultaneously optimizes wavefront coefficient data and optical parameters (including axial separation) during the reconstruction process. This approach determines the actual axial separation that best fits the observed focus light spot patterns, thereby improving measurement precision while managing calculation complexity through efficient optimization algorithms.
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 enhances the accuracy of wavefront aberration measurements by minimizing errors and improving the reliability of vision correction and diagnosis, effectively addressing the limitations of conventional algorithms.
Implementation Method 1
The Shack-Hartmann wavefront sensor consist of an array of lenslets 11 in the plane conjugated to the pupil of the human eye and an optical detector 12 such as a charge-coupled device (CCD). This incoming wavefront light is imaged onto the lenslets array 11 and produces a wavefront sensor image 13,14 as an array of focus spots 13a,14a formed on the focal plane of the optical detector 12
Implementation Method 2
Conventional wavefront reconstruction algorithms assume that the wavefront sensing image is produced by light reflected from a single layer of fundus, which contradicts OCT (optical coherence tomography) results showing multiple layers contribute to the reflection. In fact, the exact position of the point source is not mastered. Indeed, the retina is a rather thick reflector and multilayer and a probe beam is simultaneously reflected by multiple layers of the retina.
Data Source
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AI summary
The invention concerns a method for determining wave-front aberration data of a to-be-tested optical system comprising the steps of: a) providing a wave-front sensing image of light received from the tested optical system; b) providing a model representative of the optical system with at least an optical parameter representative of said model c) optimizing a set of wave-front coefficient data and said at least optical parameter of said model according to a merit function wherein the calculation of said merit function comprises the steps of : -generating a wave-front sensing modeled image of light received from said model by means of said at least optical parameter and said set of wave-front coefficient data; -calculating a criteria based on shape parameter data of the wave-front sensing image and shape parameter data of the wave-front sensing modeled image, so as to obtain wave-front aberration data of the tested optical system.