Structured Optical Signal Decorrelation for Retinal Flow Velocity
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Solution Overview
Problem
Conventional methods for measuring blood flow, particularly in small and inconveniently positioned blood vessels of the retina, struggle to accurately determine both the direction and speed of blood flow, especially when oriented transversely to the optical axis, due to limitations in optical coherence tomography systems and other techniques.
Innovation Solution
A method and system utilizing a wave interference network with a modally specific photonic lantern to separate propagation modes, generating distinct point spread functions, and calculating a ratio of correlations between scattered signals to determine velocity and direction of objects in a medium, such as blood flow, using Few-Mode Optical Coherence Tomography (FM-OCT) or laser speckle imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical coherence tomography (OCT) systems are used to measure blood flow, then the axial component of velocity can be measured, but the transversal component cannot be measured with acceptable precision
Solution Approach 1:
The patent transitions from single-mode to few-mode optical coherence tomography, adding modal dimensionality to the measurement system. By utilizing multiple propagation modes (LP01, LP11, LP21) instead of a single mode, the system gains additional measurement dimensions that enable direct detection of both axial and transverse velocity components through mode-specific scattering patterns.
Solution Approach 2:
The patent changes the optical parameters by using multiple propagation modes with different spatial distributions and scattering characteristics. Each mode provides distinct information about particle motion in different directions, allowing the system to extract both axial and transverse velocity components by analyzing the decorrelation rates of multiple modes simultaneously.
2Loss of information
If conventional OCT techniques are used, then the system structure remains simple, but the ability to detect both direction and speed of blood flow is limited
Solution Approach 1:
The patent segments the optical signal into multiple propagation modes using a wave interference network with photonic lanterns. Each mode (LP01, LP11, LP21) is separated and detected independently, allowing the system to extract different velocity information from each mode. This segmentation enables complete flow vector reconstruction while maintaining a modular system architecture.
Solution Approach 2:
The wave interference network serves multiple functions: it separates propagation modes, generates distinct point spread functions for each mode, and enables simultaneous measurement of both axial and transverse velocity components. This multi-functionality reduces the need for additional separate measurement systems while comprehensively capturing flow information.
3Measurement precision
If conventional techniques are used for blood flow measurement, then the measurement process is straightforward, but accurate measurement of transverse flow orientation is not achieved
Solution Approach 1:
The patent introduces mode-specific point spread functions as intermediaries between the optical field and the detected signal. Each propagation mode produces a characteristic PSF that encodes information about particle motion in specific directions. By analyzing the decorrelation of these mode-specific PSFs, the system indirectly measures transverse flow components that are otherwise difficult to detect directly.
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
Enables accurate measurement of both lateral and axial components of blood flow velocity, overcoming limitations of conventional techniques by providing reliable results even in complex biological tissues.
Implementation Method 1
inputting a wave into a wave interference network, generating a first point spread function (PSF) and at least one second PSF distinct from the first PSF
Implementation Method 2
collecting, via the wave interference network, a scattered signal from the medium
Data Source
AI summary
A method for determining a velocity of objects in a medium comprises inputting a wave into a wave interference network, generating a first and at least one second point spread function (PSF), outputting at least one propagation mode of the wave to the medium for illuminating the medium therewith, collecting a scattered signal from the medium, acquiring a first signal having the first PSF associated therewith and at least one second signal having the at least one second PSF associated therewith, determining a first correlation of at least one of the first signal and the at least one second signal, and a second correlation of at least one of the first signal and the at least one second signal, determining a ratio between the first correlation and the second correlation, and determining the velocity of the one or more objects in the medium based on the ratio.