Scanning Laser Retinal Camera Slit Aperture Scatter Reduction
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Solution Overview
Problem
Current retinal imaging devices face challenges in achieving high contrast images of small retinal areas due to long range scatter, require expensive equipment, and are not user-friendly for non-specialists, especially when imaging the central macula, which is crucial for early detection of vision-robbing damage.
Innovation Solution
A portable, cost-effective digital retinal imaging device using a scanning laser with near-infrared illumination and a CMOS detector array with a rolling shutter function, which scans light across the retina through a slit aperture and separates illumination and detection pathways to minimize scatter, allowing for high contrast and multiply scattered light imaging without the need for dilation or advanced optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If flood illumination is used to view the retina, then the entire retinal area can be illuminated, but image contrast deteriorates due to long range scatter
Solution Approach 1:
The patent divides the illumination into multiple discrete laser beams that are scanned across the retinal surface in a raster pattern, replacing continuous flood illumination. This segmentation allows selective illumination of specific retinal regions, reducing scattered light from non-illuminated areas while maintaining comprehensive coverage through systematic scanning.
Solution Approach 2:
The patent employs periodic scanning of laser beams across the retina using galvanometer mirrors that oscillate at controlled frequencies. The illumination follows a rhythmic back-and-forth motion, systematically covering the entire retinal area through repeated periodic cycles, enabling comprehensive imaging while maintaining temporal control over illumination patterns.
2Measurement precision
If confocal apertures are used to eliminate scattered light, then image contrast improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical confocal aperture systems with a simpler scanning laser approach using galvanometer mirrors. Instead of using sophisticated optical apertures and mechanical scanning components, the invention uses electronically controlled laser beam deflection to achieve scattered light rejection through temporal gating and spatial scanning, significantly reducing mechanical complexity.
Solution Approach 2:
The patent changes the illumination parameters by using coherent laser light with specific wavelengths and scanning patterns, replacing incoherent broadband flood illumination. This parameter change enables contrast improvement through temporal coherence gating and spatial selective illumination, achieving confocal-like effects without requiring physical confocal aperture mechanisms.
3Measurement precision
If specialized scanning laser ophthalmoscopes are used to improve image contrast, then retinal imaging quality improves, but ease of operation deteriorates due to specialist operation requirements
Solution Approach 1:
The patent designs a scanning laser ophthalmoscope that can be operated by non-specialists while maintaining high imaging quality. The system incorporates automated scanning control, simplified user interface, and robust alignment tolerances that enable general practitioners and technicians to obtain diagnostic-quality retinal images without specialized training, making the device universally accessible.
Solution Approach 2:
The patent implements automated features including self-alignment mechanisms, automatic scanning pattern generation, and real-time image quality assessment that reduce the need for operator expertise. The system automatically adjusts scanning parameters and compensates for minor misalignments, enabling users to obtain high-quality retinal images through simplified操作流程 without requiring specialized ophthalmic knowledge.
4Measurement precision
If high quality optics are used to reduce scatter, then image contrast improves, but manufacturing cost increases
Solution Approach 1:
The patent uses standard off-the-shelf optical components and commercial galvanometer mirrors rather than custom-designed high-precision optics. The system achieves scatter reduction through scanning methodology and temporal gating rather than relying on expensive specialized optical elements, significantly reducing manufacturing costs while maintaining diagnostic image quality.
Solution Approach 2:
The patent replaces expensive high-precision optical scattering reduction mechanisms with a scanning-based approach using galvanometer mirrors and temporal gating. Instead of using costly specialized optics to physically block or filter scattered light, the system uses controlled beam scanning and timing to selectively detect light from the focal plane, achieving scatter reduction through methodological rather than optical means.
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 device provides high-quality, high-contrast images of the retina, enabling early detection of retinal diseases like diabetic retinopathy and age-related macular degeneration, is user-friendly for non-specialists, and can operate in various conditions, including extreme temperatures and without a power source, while reducing equipment costs and complexity.
Implementation Method 1
The improvements noted above, and methods for successfully imaging small retinal features were combined in United States Patent Application Nos. 60/329,731; 10/493,044; 60/350,836; and PCT Application No. PCT/US02/32787... because infrared light is absorbed less than visible light and scatters over longer distances
Implementation Method 2
The long range scatter problem was identified to occur, not only from out of plane tissues, but also from the biological tissues that are inherently scattering, especially those within and near the retina
Implementation Method 3
The beam separation arrangement is configured to space the illumination path and the return path sufficiently apart to reduce reflections from sources out of the desired focal plane
Implementation Method 4
a detection arrangement disposed to receive light remitted from the target and operative to produce an image
Data Source
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AI summary
A portable, lightweight digital imaging device uses a slit scanning arrangement to obtain an image of the eye, in particular the retina. The scanning arrangement reduces the amount of target area illuminated at a time, thereby reducing the amount of unwanted light scatter and providing a higher contrast image. A detection arrangement receives the light remitted from the retinal plane and produces an image. The device is operable under battery power and ambient light conditions, such as outdoor or room lighting. The device is noncontact and does not require that the pupil of the eye be dilated with drops. The device can be used by personnel who do not have specialized training in the eye, such as emergency personnel, pediatricians, general practitioners, or volunteer or otherwise unskilled screening personnel. Images can be viewed in the device or transmitted to a remote location. The device can also be used to provide images of the anterior segment of the eye, or other small structures. Visible wavelength light is not required to produce images of most important structures in the retina, thereby increasing the comfort and safety of the device. Flexible and moderate cost confocal and fluorescent imaging, multiply scattered light images, and image sharpening are further functionalities possible with the device.