Wavefront Measurement System Aberration Range
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Solution Overview
Problem
Existing wavefront measurement systems for the eye are limited in their ability to measure a wide range of pupil sizes and aberrations, require complex registration procedures for corneal topography and wavefront analysis, and lack efficient detection of early eye defects like cataracts, leading to increased costs and reduced usability.
Innovation Solution
A wavefront measurement system with independently movable wavefront analysis and accommodation measurement modules, utilizing a short focal length Hartmann Shack lenslet array, off-axis laser illumination, and a Placido disk pattern for corneal reflection reduction, enabling wider pupil size measurement and simultaneous corneal topography analysis, along with advanced image processing for defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Hartmann-Shack lenslet array with long focal length is used, then the system can achieve good measurement precision for small aberrations, but the measurement range for large aberrations and wide pupil sizes is limited
Solution Approach 1:
The patent divides the measurement process into two stages: first using a long focal length lenslet array for precise measurement of small aberrations, then switching to a short focal length lenslet array for measuring large aberrations and wide pupil sizes. This segmentation of measurement functions across different lenslet arrays resolves the contradiction between precision and measurement range.
Solution Approach 2:
The patent implements a dynamic switching mechanism that allows the system to change lenslet arrays based on the measured aberration magnitude and pupil size. The system automatically selects the appropriate lenslet array configuration, making the measurement system adaptable to different measurement conditions and expanding its versatility while maintaining precision.
2Device complexity
If on-axis laser illumination is used, then the optical path is simple, but corneal reflections limit the measurable pupil size and create polarization effects
Solution Approach 1:
The patent employs off-axis laser illumination at a specific angle (e.g., 30 degrees) relative to the optical axis. This asymmetric illumination geometry directs reflected light from the cornea away from the detection path, eliminating the limitation on measurable pupil size and reducing polarization effects while maintaining a manageable optical path through careful design.
3Measurement precision
If separate measurement procedures are used for corneal topography and wavefront analysis, then each measurement can be optimized, but complex registration procedures are required to align the measurements
Solution Approach 1:
The patent combines corneal topography measurement and wavefront analysis into a single integrated measurement procedure. By using the same off-axis laser illumination and detection system for both measurements, the patent eliminates the need for complex registration procedures while maintaining the measurement precision of both techniques through careful optical design and data processing.
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
The system allows for rapid and accurate measurement of aberrations across a wide range of pupil sizes, reduces corneal reflections, and enables early detection of eye defects like cataracts, improving measurement efficiency and reducing costs by integrating multiple ophthalmic tests into a single instrument.
Implementation Method 1
a lenslet array located along an optical path of the wavefront, for receiving the wavefront and for creating a plurality of spot images thereof
Implementation Method 2
a slightly off-axis laser illumination beam, thereby reducing the limitation imposed on the pupil size of the eye that can be measured, and the limited polarization effects generated by the various reflections of the illuminating and reflected beams in their optical paths
Implementation Method 3
a projector for projecting the pattern onto the cornea for reflection by the cornea and a second imaging device for receiving the reflected pattern to determine corneal topography
Data Source
Figure 1
Figure 2~3A
Figure 3B~3C
AI summary
A wavefront measurement system, for measurement of aberrations in the eye, and for measurement of the topography of the cornea of the eye. The system differs from previously available systems in that the wavefront measurement of the eye's aberrations can be performed as a function of eye accommodation. Furthermore, methods for reducing corneal reflection are described. Additionally, the use of a very short focal length Hartman Shack lenslet array enables a very wide range of low order aberrations, up to ±25 diopters, to be measured without any refocusing or motion of the system. Also, methods are described for enabling the presence of defects within the eye to be determined using the aberration measurement system. Another embodiment captures the pupil centering position without any projected illumination pattern being used, so that a subsequent accurate centering and focusing procedure can commence at the initially captured position, thus reducing measurement time.