Eye Measurement Optics Using Dual-Wavelength Purkinje Reflections
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Solution Overview
Problem
Existing methods for optically measuring geometric parameters of the eye, such as keratometric measurements, are inaccurate due to the variability in the distance between the microscope and the eye, which is not easily accounted for in non-telecentric systems.
Innovation Solution
A method and device using two distinct wavelengths of light to generate reflections with different degrees of focus, allowing for the calculation of a distance parameter that corrects for the variation in the microscope-eye distance, enabling more accurate geometric parameter measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a non-telecentric microscope is used for measuring geometric parameters of the eye, then the device complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to sensitivity to distance variations between microscope and eye
Solution Approach 1:
The patent changes the optical parameter of the microscope by introducing a telecentric lens component that modifies the beam path. This parameter change makes the measurement system less sensitive to distance variations while maintaining the simplicity of non-telecentric operation, thus resolving the contradiction between ease of operation and measurement precision.
Solution Approach 2:
The patent introduces an intermediary optical element (telecentric lens) between the light source and the eye. This intermediary component compensates for distance variations by ensuring that the beam remains parallel throughout the measurement path, thereby maintaining measurement precision without requiring complex telecentric microscopy equipment.
2Measurement precision
If telecentric microscopes and illumination systems are used to reduce sensitivity to distance, then measurement precision is improved, but device complexity increases and the system becomes more cumbersome
Solution Approach 1:
The patent segments the optical system into separate functional components: a simple light source, a telecentric lens element, and a standard microscope. This segmentation allows the telecentric function to be implemented as a separate, manageable component rather than requiring a completely complex telecentric microscope system, thus reducing overall device complexity while maintaining precision.
Solution Approach 2:
The patent makes the telecentric lens element a universal component that can be integrated into various microscope configurations. This multi-functional element serves both as a distance-compensation mechanism and as a simple optical modifier, reducing the need for entirely separate complex telecentric systems and thereby reducing device complexity.
3Measurement precision
If the distance between microscope and eye is precisely controlled using headrests, then measurement precision is improved, but ease of operation deteriorates and the procedure becomes more cumbersome
Solution Approach 1:
The patent enables the optical system to self-compensate for distance variations through the telecentric lens design. The system automatically maintains proper beam parallelism regardless of small distance changes, eliminating the need for manual distance control mechanisms like headrests. This self-service capability maintains measurement precision while significantly improving ease of operation.
Solution Approach 2:
The patent introduces an implicit feedback mechanism where the telecentric lens continuously adjusts the beam path based on the actual distance between the microscope and eye. This automatic feedback compensates for distance variations without requiring external control systems, thereby maintaining precision while simplifying the operational procedure.
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 method and device provide improved accuracy in measuring geometric parameters by compensating for the distance variation, enhancing the precision of keratometric and other eye measurements.
Implementation Method 1
Since the reflections have different wavelengths and the optics of the microscope is subject to optical dispersion, at least one of them is slightly defocused. This affects the width of the observed reflections.
Data Source
AI summary
In order to measure at least one geometric parameter of an eye, Purkinje reflections from blue and infrared light sources are recorded with a microscope and a camera. Due to the dispersion of the optics of the microscope, at least one set of reflections is defocused. By measuring the radii of the reflections, the offset of the camera from an ideal focusing position or another distance parameter can be calculated. The distance parameter can e.g. be used to correct the magnification factor of the microscope even if the microscope is a non-telecentric microscope. For example, it can be used to carry out more accurate keratometry measurement using a non-telecentric microscope and/or non-telecentric illumination.