Swept Source Interferometry Arbitrary Sweep Patterns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Swept-source interferometric imaging systems suffer from motion artifacts caused by axial motion of scatterers, leading to signal shifts and broadening, which can result in misdiagnosis, especially when imaging the human eye at low sweep rates.
Innovation Solution
Implementing arbitrary sweep patterns where the swept source changes direction or order of wavelength output during the sweep, creating phase instability for moving scatterers, causing their signal to spread and appear as noise, thereby attenuating the signal and reducing artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional continuous sweep patterns are used, then the imaging system can operate at low sweep rates, but motion artifacts occur causing axial shifts and signal broadening
Solution Approach 1:
The patent applies periodic action by implementing a sweep pattern that reverses direction at spectral boundaries, creating a triangular or sawtooth wavelength modulation over time. This periodic reversal causes moving scatterers to accumulate phase errors that spread their signals across multiple depth locations, effectively attenuating their contribution to artifacts while maintaining low sweep rates for high sensitivity imaging
Solution Approach 2:
The patent changes the temporal parameter of wavelength output by using non-monotonic sweep patterns where the wavelength does not continuously increase or decrease but instead reverses direction. This parameter change in the sweep trajectory transforms the phase behavior of moving scatterers, causing their signals to decorrelate and spread rather than concentrate at shifted locations
2Reliability
If arbitrary sweep patterns with direction changes are implemented, then motion artifacts are reduced by spreading moving scatterer signals, but the sweep pattern complexity increases
Solution Approach 1:
The sweep source control parameter (wavelength vs. time relationship) is changed from a simple monotonic function to a piecewise linear or triangular function that reverses direction at predetermined spectral points. This parameter transformation achieves artifact reduction while maintaining relatively simple control logic that can be implemented through standard swept source modulation capabilities
Solution Approach 2:
The patent converts the harmful effect of moving scatterers into a beneficial signal attenuation mechanism. By designing the sweep pattern to cause phase instability specifically for moving targets, the system transforms the Doppler-induced phase shifts that normally create artifacts into a mechanism that spreads and suppresses moving scatterer signals, making them appear as reduced-level noise rather than structured artifacts
3Reliability
If the sweep rate is increased to reduce motion artifacts, then axial shift artifacts are reduced, but the sensitivity of the imaging system decreases
Solution Approach 1:
The periodic reversal of the sweep direction creates a time-varying phase modulation that selectively affects moving scatterers. Static scatterers experience symmetric phase accumulation that cancels out over the complete sweep cycle, while moving scatterers experience asymmetric phase evolution that spreads their signals. This allows maintenance of low sweep rates for high sensitivity while achieving motion artifact suppression through the periodic modulation pattern
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 arbitrary sweep patterns effectively reduce motion artifacts by spreading the signal of moving scatterers as noise, improving image clarity and reducing the risk of misdiagnosis without compromising image quality of static samples.
Implementation Method 1
OCT is an interferometric imaging method that determines the scattering profile of a sample along the OCT beam by detecting light reflected from a sample combined with a reference beam
Implementation Method 2
The axial shift, caused by a Doppler shift proportional to the axial velocity of the moving scatterer, may be the most critical of the three
Data Source
AI summary
Embodiments herein include swept-source interferometric imaging systems employing arbitrary sweep patterns in which a swept-source is swept over a continuous spectral range where the variation of wavelength over time is noncontinuous. Embodiments include sweep patterns that result in reduction of signals from moving scatterers and where the sweep is synchronized with the dead time of the camera.