Scattered Light Correction in Digital Fundus Imaging
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Solution Overview
Problem
Existing methods for imaging the ocular fundus are hindered by scattered light from cataracts, leading to distorted measurements and reduced image quality, with current solutions either reducing illumination, causing motion blur or requiring additional equipment that increases complexity and cost.
Innovation Solution
A method using a digital fundus camera to illuminate the ocular fundus, determine scattered light intensity in non-illuminated areas, average and subtract it from the image to correct for scattered light, allowing for accurate and reliable measurement of both relative and absolute scattered light levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the illumination brightness is reduced to decrease scattered light saturation, then the scattered light effect is reduced, but the image becomes darker and contrast deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring and determining the scattered light characteristics before the actual fundus imaging. The system performs a preliminary measurement phase where it characterizes the scattered light from cataracts, then uses this pre-acquired information to correct the subsequent fundus images, thereby eliminating scattered light effects without compromising image brightness or contrast.
Solution Approach 2:
The patent implements feedback by using the measured scattered light characteristics to adjust and correct the fundus imaging process. The system continuously monitors scattered light levels and uses this feedback information to compensate for scattered light effects in real-time, maintaining optimal image quality while accounting for cataract-induced scattering.
2Illumination intensity
If the exposure time is extended to compensate for reduced illumination, then the image brightness is maintained, but motion blur increases due to eye movements
Solution Approach 1:
The patent replaces the mechanical/time-based solution (extending exposure time) with an optical/mathematical solution (scattered light correction algorithms). Instead of increasing exposure time to maintain brightness, the system uses computational methods to correct scattered light effects, thereby maintaining image sharpness while achieving the desired brightness through alternative means.
3Measurement precision
If additional equipment is added to measure and correct scattered light, then scattered light measurement capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies universality by designing a system where the fundus camera performs multiple functions: it serves as both the primary imaging device and the scattered light measurement instrument. The same optical path and sensor are used for both fundus imaging and scattered light characterization, eliminating the need for separate dedicated measurement equipment and reducing overall system complexity.
Solution Approach 2:
The system applies self-service by using its own resources (the fundus camera's optical system and sensor) to measure and characterize the scattered light it encounters. The fundus camera essentially measures its own imaging conditions and uses this self-acquired information to correct scattered light effects, eliminating the need for external measurement devices.
4Measurement precision
If manual adjustment for cataract severity is implemented, then scattered light correction can be tailored, but ease of operation decreases and requires user expertise
Solution Approach 1:
The patent applies parameter changes by automatically determining scattered light characteristics through measurement rather than requiring manual selection. The system transforms the qualitative, expertise-based manual adjustment into a quantitative, automatically measured parameter set, thereby simplifying operation while maintaining or improving correction accuracy through objective measurement data.
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 enables high-quality, accurate, and reproducible ocular fundus images by correcting for scattered light, allowing for precise evaluation of cataract severity and maintaining image quality without the need for additional equipment or complex procedures.
Implementation Method 1
In every imaging process, cloudiness in the eye lens (cataract), in the vitreous body, and/or in the cornea has a negative impact on image quality in that it scatters both the incident illumination light and the light reflected in the eye.
Data Source
AI summary
A method by which fundus photographs that are corrected for scattered light can be realised by using a digital fundus camera. The fundus is illuminated and a photograph of the fundus is realized. The photographed area is greater than the illuminated are. The scattered light intensity is determined and is used for correction. Measurement points for determining the scattered light intensity are defined in the non-illuminated area. Values of the scattered light intensity determined at the measurement points are averaged. Average-scattered light intensity thus determined is subtracted from the intensity values of the photograph to correct the photograph.