Corneal Topography Half-Slit Image Alignment via Edge Detection

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Solution Overview

Problem

Existing slit beam systems in ophthalmology face challenges in accurately aligning half-slit images, leading to errors in the reconstruction of eye surfaces and optical power estimates due to manual alignment inaccuracies and patient movement.

Innovation Solution

A corneal topography slit image alignment system that captures and analyzes half-slit images using a camera and edge detector to determine misalignment, allowing for correction of alignment errors in three-dimensional coordinates, thereby improving the accuracy of slit image reconstructions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual alignment of half-slit images is used, then the system is simple to operate, but alignment accuracy deteriorates due to user error and patient movement

Engineering Contradiction:
Improvealignment accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the manual mechanical alignment process with an automated image processing system. The computer captures half-slit images and uses software algorithms to automatically detect edges, calculate misalignment, and determine correction values, eliminating the need for manual visual alignment while significantly improving precision.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system performs self-alignment by automatically analyzing its own captured images. The computer processor independently detects the misalignment of half-slit images and calculates the necessary corrections without requiring external manual intervention, enabling the system to self-correct alignment errors.

Inventive Principle:
Principle #25Self-service

2Measurement precision

If automated image analysis is implemented, then alignment precision improves, but device complexity increases due to additional processing requirements

Engineering Contradiction:
Improvealignment accuracyVSAvoidimage analysis complexity
Core Design Contradiction:
Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent extracts only the critical alignment information from the captured images by focusing on detecting the edges of the half-slit images. Rather than analyzing the entire image data, the system selectively extracts the boundary positions of the slits, simplifies the measurement process while maintaining high precision.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces an intermediary computational process that bridges the captured image and the final alignment correction. The system uses edge detection algorithms and coordinate transformation calculations as intermediate steps to convert raw image data into precise misalignment measurements, making the complex measurement process manageable and accurate.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If manual half-slit alignment is used, then the process is quick, but errors propagate to three-dimensional coordinate calculations

Engineering Contradiction:
Improvecoordinate calculation reliabilityVSAvoidalignment time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary alignment analysis by capturing and analyzing half-slit images before proceeding to the main three-dimensional coordinate calculation. This preliminary step ensures that alignment corrections are determined in advance, preventing error propagation to subsequent calculations while maintaining an efficient workflow.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by using the analyzed half-slit image alignment status to inform and correct the three-dimensional coordinate calculations. The misalignment detection results feed back into the coordinate transformation process, allowing the system to compensate for alignment errors and produce reliable coordinate data.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP1909638B1Corneal topography slit image alignment via analysis of half-slit image alignment
Publication Date: 2010.06.09 BAUSCH & LOMB INC
  • EP1909638B1 patent drawingFigure 1~2
  • EP1909638B1 patent drawingFigure 3~6

AI summary

A corneal topography slit image alignment system 10, includes a half-slit projector 14 for projecting half-slit images onto a patient's eye 16. Half-slit images 28 and 30 are aligned into a single slit image. A camera 18 captures an image of the aligned slit image. Processor 20 including a memory 26 connected to the half-slit projector 12 and the camera 18 analyzes the alignment of the half-slit images 28 and 30. An edge detector 22 detects the edges of each captured half-slit image and determines an amount of misalignment of the half-slit images 28 and 30 relative to half-slit images being aligned into a single slit image. This amount of misalignment allows computer processor 20 to correct the three- dimensional coordinates of the slit images obtained by a slit beam system 14.