Fundus Imaging Aperture Positioning for Corneal Flare Suppression
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Solution Overview
Problem
Existing fundus cameras struggle to suppress flare in fundus images due to corneal reflection, leading to degraded image quality, and existing methods fail to achieve precise suppression of flare with high precision.
Innovation Solution
The ophthalmic apparatus adjusts the relative position of the optical system or moves the imaging aperture to minimize the distance between the imaging aperture conjugate position and the corneal reflection image, using a simple configuration to suppress flare while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the imaging aperture is positioned to capture returning light from the fundus, then the fundus image can be acquired, but corneal reflection light enters the imaging optical system causing flare and degraded image quality
Solution Approach 1:
The patent utilizes the corneal reflection light (harmful factor) as an alignment reference. By detecting the position of the corneal reflection image and calculating the optimal imaging aperture conjugate position based on corneal curvature radius, the system converts the harmful flare source into a useful reference for positioning, thereby suppressing flare while maintaining image quality
Solution Approach 2:
The patent changes the positional parameter of the imaging aperture conjugate position relative to the corneal apex. By adjusting this position to be at a distance of R/2−d from the corneal reflection image position (where R is corneal curvature radius and d is distance from corneal apex to imaging aperture), the system optimizes the balance between capturing fundus light and blocking corneal reflection light
2Object-affected harmful factors
If existing methods change alignment target position according to pupil size, then some flare suppression is achieved, but precise suppression of flare is not attained
Solution Approach 1:
The patent implements a feedback mechanism by detecting the corneal reflection image position and using it to calculate and adjust the imaging aperture conjugate position. This closed-loop approach provides precise flare suppression by continuously referencing the actual corneal reflection position rather than using fixed or pupil-size-based alignment targets
Solution Approach 2:
The patent performs preliminary positioning of the imaging aperture conjugate position before fundus imaging based on pre-measured corneal curvature radius. This preliminary action establishes the optimal position in advance, preventing flare before imaging begins rather than attempting to correct it during or after image acquisition
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 effectively suppresses flare in fundus images with high precision, ensuring high-quality imaging without degrading the image quality, and can be applied to suppress flare in images of other eye sites as well.
Implementation Method 1
flare occurs in the fundus images acquired by such fundus cameras due to the corneal reflection light from the cornea
Implementation Method 2
the imaging optical system having an imaging aperture and being configured to guide returning light from the subject's eye having passed through the imaging aperture to an imaging sensor
Data Source
AI summary
An ophthalmic apparatus includes an optical system having an illumination and imaging optical systems, a movement mechanism, and a controller. The illumination optical system may illuminate a fundus of a subject's eye with illumination light. The movement mechanism may relatively move the subject's eye and the optical system in an optical axis direction of the imaging optical system. When a corneal curvature radius is R and a distance from a corneal apex position to an imaging aperture conjugate position substantially conjugate optically to the imaging aperture is d, the controller may control the movement mechanism so that light amount of the returning light passing through the imaging aperture becomes less than when a distance in the optical axis direction between the imaging aperture conjugate position and a position of a corneal reflection image of the illumination light is (R/2−d).