Corneal Topographer Spatial Spectrum Analysis
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Solution Overview
Problem
Current corneal topographers rely on projecting concentric rings or wave-front sensing, which are limited in accurately measuring absolute distances and providing detailed shape information of the cornea, especially without moving parts and with high precision.
Innovation Solution
A compact corneal topographer using standard imaging optics, a chiral optical mask, photo-sensor, and digital processing to analyze the spatial spectrum of Purkinje reflections from the cornea, generating defocus-maps and depth-maps by projecting a pattern light and evaluating the displacement of the spatial spectrum, allowing for precise distance measurements without prior knowledge of the cornea's distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional corneal topographers use concentric rings projection or wave-front sensing, then corneal shape measurement is achieved, but measurement precision of absolute distances is limited
Solution Approach 1:
The corneal surface is divided into multiple sub-regions, with each sub-region illuminated by a distinct spot in the pattern light. The spatial spectrum is separately analyzed for each sub-region to determine local defocus and absolute distance, enabling high-precision measurements across the entire corneal surface through segmented analysis
Solution Approach 2:
The invention transitions from analyzing only the spatial distribution of reflected light (2D pattern) to analyzing the spatial spectrum in the frequency domain (adding a dimensional transformation). By evaluating the displacement of the spatial spectrum, the system extracts absolute distance information that cannot be obtained from simple pattern analysis alone
2Reliability
If a compact device without moving parts is used, then device simplicity and reliability are improved, but measurement precision may be compromised
Solution Approach 1:
The invention replaces mechanical scanning systems with a stationary optical setup using pattern light projection and spatial spectrum analysis. The compact device has no moving parts, yet achieves high measurement precision through digital processing of the spatial spectrum displacement, substituting mechanical complexity with optical-digital integration
Solution Approach 2:
The system changes the parameter being measured from relative pattern distortion to absolute spatial spectrum displacement. By analyzing how the spatial spectrum shifts in response to defocus, the device extracts precise corneal shape information without requiring mechanical movement or prior knowledge of corneal distance
3Measurement precision
If spatial spectrum analysis is used to measure absolute distances, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The chiral optical mask serves multiple functions: it modulates the pattern light to create distinct spatial signatures for each sub-region, and it enables the spatial spectrum displacement analysis that extracts absolute distance information. This single optical element provides multi-functionality, reducing overall device complexity while maintaining high measurement precision
Solution Approach 2:
The chiral optical mask acts as an intermediary between the pattern light source and the corneal surface. It modulates the light in a way that encodes spatial information, allowing the system to measure absolute distances without direct mechanical intervention or complex optical path adjustments
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 accurate defocus and depth mapping of the corneal surface, providing a detailed corneal topogram that can be used for refractive surgery and contact lens fitting, with the ability to adapt for other eye surfaces and wavelengths, enhancing measurement precision and versatility.
Implementation Method 1
An optical element producing chiral, or helical, modulation of the phase of a transmitting or of a reflecting light beam
Implementation Method 2
a photo-sensor converting light into a digital electronic signal
Implementation Method 3
the light reflected by the corneal surface, transmitted by the imaging optics
Implementation Method 4
imaging optics to collect the light reflected by the cornea
Implementation Method 5
a light source to project a pattern light on the corneal surface
Data Source
AI summary
This invention describes a corneal topographer with a light source to project a pattern light on the cornea, imaging optics for collecting the reflection from the cornea and projecting it on to a photo-sensor, an optical mask to modulate the light beam such that focusing error of the corneal image results in displacement of its spatial spectrum relative to a reference spectrum. Defocus maps, depth-maps and a corneal topogram can be constructed by measuring and processing the spectral displacement corresponding different sub-regions of the cornea. The cornea topographer is compact and inexpensive. The corneal topograph can be used in refractive eye surgery and in contact lens fitting.