Tunable Clock System for OCT Frequency Sampling Stability
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Solution Overview
Problem
Current OCT systems face challenges in controlling the relationship between the scanning of swept optical signals and the sampling of interference signals, leading to instability and inaccuracies in frequency tuning, which affects imaging quality and resolution, especially in high-speed applications like in-vivo imaging.
Innovation Solution
A tunable clock system is introduced that allows for adjustable absolute frequencies of the k-clock signals and the initiation of sampling, enabling precise control over the optical frequency sampling interval and sweep start frequency, using a controller with a temperature control system to stabilize the clock system and ensure consistent sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a traditional tunable laser is used as the swept source, then high spectral brightness and simple optical design are achieved, but frequency tuning stability and linearity are difficult to maintain at high sweep rates
Solution Approach 1:
The patent introduces a k-clock signal as an intermediary reference that mediates between the swept source frequency tuning and the detector sampling. This k-clock signal, generated by filtering the swept source output through a narrowband filter, serves as a stable timing reference that compensates for frequency tuning instabilities and non-linearities, enabling accurate spectral sampling even when the swept source frequency drifts or tunes non-linearly
Solution Approach 2:
The system employs feedback by using the k-clock signal to control the sampling rate of the detector. The sampling frequency is dynamically adjusted based on the instantaneous frequency of the swept source as indicated by the k-clock, creating a feedback loop that maintains accurate spectral sampling despite variations in sweep rate or frequency stability
2Productivity
If the sweep rate is increased for high-speed imaging, then motion-induced artifacts are reduced and imaging time is shortened, but frequency tuning accuracy and sampling synchronization become more difficult to maintain
Solution Approach 1:
The patent implements dynamic adaptation by making the sampling frequency variable rather than fixed. The k-clock signal dynamically adjusts the sampling rate to match the instantaneous sweep rate of the光源, allowing the system to maintain accurate spectral sampling even when operating at high sweep rates where fixed-frequency sampling would fail
Solution Approach 2:
The system replaces mechanical synchronization methods with an optical-based k-clock reference. Instead of using mechanical delay lines or fixed timing circuits to synchronize sampling with the sweep, the patent uses an optically-derived k-clock signal that automatically tracks the swept source frequency, enabling high-speed operation without mechanical constraints
3Device complexity
If fixed-frequency sampling is used, then the data acquisition system is simpler to implement, but it cannot compensate for frequency sweep non-linearities and drift
Solution Approach 1:
The system implements self-service by having the swept source generate its own sampling clock reference. The k-clock signal is derived directly from the swept source output through narrowband filtering, meaning the sampling reference is self-generated and automatically tracks the source frequency without requiring external calibration or complex synchronization circuitry
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 solution enhances the flexibility and accuracy of interference signal sampling, reducing motion-induced artifacts and improving imaging resolution by ensuring evenly spaced samples and stable frequency references, thereby enhancing the overall performance of OCT systems, particularly in high-speed imaging applications.
Implementation Method 1
a k-clock spectral filter that filters the swept optical signal based on an optical frequency sampling interval
Implementation Method 2
an optical frequency reference that provides a frequency reference for the swept optical signal... A temperature control system is used for controlling a temperature of the tunable clock system
Implementation Method 3
Optical coherence analysis relies on the use of the interference phenomena between a reference wave and an experimental wave
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. The clock system is also tunable to allow the control or flexibility over the relationship between the scanning of the swept optical signal and the sampling of the interference signal by the data acquisition system. Specifically, the absolute frequencies of the swept optical signal at which the k-clock signals are generated can be adjusted.