OCT Clock System Phase Sensitive Interference Sampling
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Solution Overview
Problem
In phase-sensitive Optical Coherence Tomography (OCT) applications, maintaining stability in the frequency of swept optical signals across successive sweeps is crucial for accurate imaging, particularly in Doppler OCT and synthetic aperture imaging, where phase stability is essential to avoid noise subtraction errors.
Innovation Solution
A clock system that generates a k-clock signal and an optical frequency reference sweep signal, ensuring sampling occurs at the same optical frequencies by using a clock/trigger optical module with etalons or interferometers to filter and trigger the swept optical signal, providing an absolute frequency reference for consistent sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed frequency tuning is used to improve imaging speed and reduce motion artifacts, then productivity is improved, but measurement precision deteriorates due to frequency instability across successive sweeps
Solution Approach 1:
The patent implements a feedback mechanism where the actual swept frequency is continuously monitored and used to adjust the sampling clock in real-time. The controller receives frequency information from the swept source and modifies the sampling rate accordingly, ensuring that samples are always taken at the correct optical frequency regardless of sweep rate variations. This closed-loop feedback system maintains measurement precision while allowing high-speed tuning.
Solution Approach 2:
The patent dynamically changes the sampling parameters based on the actual swept frequency characteristics. The sampling clock frequency is adjusted in real-time to match the instantaneous sweep rate, and the sampling points are repositioned in k-space to maintain uniform frequency sampling. This parameter adaptation allows the system to operate at high speeds while preserving frequency stability and measurement accuracy.
2Use of energy by moving object
If tunable lasers are used as swept sources to achieve high spectral brightness, then use of energy by moving object is improved, but device complexity worsens due to requirements for stable frequency sweeping
Solution Approach 1:
The patent introduces an intermediary sampling clock system that acts as a mediator between the swept source and the detector. This sampling clock generates timing signals based on the actual swept frequency characteristics and uses them to control when samples are taken. By inserting this intermediary layer, the system can use simpler swept sources with lower spectral brightness requirements while still achieving stable, repeatable measurements through precise sampling synchronization.
3Device complexity
If filtering or generation in successive optical frequency sampling intervals is used to simplify optical configuration, then device complexity is improved, but measurement precision worsens due to dependence on sweep rate and tuning accuracy
Solution Approach 1:
The patent replaces the mechanical/optical frequency stabilization mechanism with an electronic sampling synchronization system. Instead of relying on the swept source to maintain precise frequency stability through mechanical or optical means, the system uses an electronically controlled sampling clock that adapts to the actual sweep characteristics. This substitution of electronic control for mechanical/optical stabilization simplifies the optical configuration while maintaining or improving measurement precision through flexible, real-time parameter adjustment.
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 ensures that the sampling of interference signals occurs at the same frequency/wavelength on every axial line, enhancing the stability and accuracy of OCT imaging by reducing noise and artifacts, particularly in high-speed imaging applications.
Implementation Method 1
a clock/trigger optical module with etalons or interferometers to filter and trigger the swept optical signal
Data Source
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AI summary
An OCT system and particularly its clock system generates a k-clock signal but also generates an optical frequency reference sweep signal that, for example, indicates the start of the sweep or an absolute frequency reference associated with the sweep at least for the purposes of sampling of the interference signal and/or processing of that interference signal into the OCT images. This optical frequency reference sweep signal is generated at exactly the same frequency of the swept optical signal from sweep to sweep of that signal. This ensures that the sampling of the interference signal occurs at the same frequencies, sweep to sweep.