OCT Dynamic Focus Sweeping Windowed Averaging
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Solution Overview
Problem
Conventional OCT imaging systems face challenges in achieving high lateral resolution and sufficient signal intensity when imaging low-reflectance structures such as the vitreous, crystalline lens, choroid, and sclera due to limitations in beam diameter and numerical aperture, leading to reduced transverse resolution and inefficient light reflection.
Innovation Solution
The implementation of dynamic focus sweeping and windowed averaging in OCT imaging, where the focal plane is adjusted during a scan to generate multiple image frames at different focal positions, and these frames are registered and averaged with weighted intensity values to produce a composite image with improved resolution and accuracy across the image range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high numerical aperture system is used to focus light to a smaller spot, then transverse resolution is improved, but the depth range over which the beam maintains acceptable diameter is reduced
Solution Approach 1:
The patent applies dynamic focus sweeping by continuously varying the focal plane position of the illumination beam throughout the imaging depth range. This dynamic adjustment allows the system to maintain high transverse resolution at different depths by adapting the focus position, thereby resolving the contradiction between achieving small spot size (high resolution) and maintaining acceptable beam diameter over long depth ranges.
2Area of stationary object
If a larger illumination beam is used to image small reflective structures, then the beam can cover more area, but the proportion of reflected light returning to the OCT instrument decreases
Solution Approach 1:
The patent employs local quality by dynamically adjusting the illumination beam parameters (focus position and diameter) to match the local characteristics of the tissue being imaged. By adapting the beam properties to the specific depth and tissue type, the system optimizes both the imaging area coverage and the reflected light collection efficiency, resolving the contradiction between large area coverage and sufficient signal return.
3Illumination intensity
If the total light used in diagnostic instruments is increased to compensate for illumination inefficiencies, then signal intensity improves, but safety limits are exceeded
Solution Approach 1:
The patent utilizes parameter changes by dynamically adjusting multiple illumination parameters including focus position, beam diameter, and sweep frequency. These parameter optimizations improve the efficiency of light utilization and signal collection, thereby achieving adequate signal intensity without increasing the total light power to levels that would violate safety limits.
4Manufacturing precision
If dynamic focus sweeping is implemented to maintain high resolution over long image ranges, then transverse resolution is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical focus adjustment mechanisms with electronic control of the illumination source and detection system. By using electronic modulation and digital signal processing to achieve dynamic focus sweeping, the system maintains high transverse resolution over long image ranges while minimizing mechanical complexity and improving system reliability.
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 the generation of high-resolution images with improved signal-to-noise ratio, effectively capturing weak-intensity features like the vitreous and choroid, while maintaining high transverse resolution over a long image range, thereby overcoming the limitations of conventional OCT systems.
Implementation Method 1
OCT is an imaging technique capable of acquiring sub-surface images of a subject at micrometer resolutions
Implementation Method 2
the total light reflected back to the OCT instrument
Implementation Method 3
a high numerical aperture system focuses light to a relatively smaller spot
Implementation Method 4
a lower numerical aperture system has a longer zone in which the beam is narrow
Data Source
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AI summary
During scan capture with an OCT imaging system (100), the focal plane position can be simultaneously shifted over at least a portion of an image range (Zim). As a result, a plurality of image frames respectively corresponding to various focal plane positions (202, 204) is acquired. The image frames can be combined to generate a composite image (914) having suitable resolution throughout the image range, including regions associated with weak-intensity or low-reflectance features. Further, windowed averaging (606, 804) can be performed prior to generation of the composite image so that the composite image incorporates weights (906) given to image data in focus.