Frequency Down Conversion Optical Coherence Tomography System
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Solution Overview
Problem
Conventional swept source optical coherence tomography (SS-OCT) systems face limitations in imaging samples with surface variations exceeding their imaging range due to light attenuation, as they can only effectively image a narrow section along the optical axis, leading to challenges in measuring samples with deeper or more extensive surface features.
Innovation Solution
The implementation of a frequency down conversion optical coherence tomography system that converts high-frequency, narrow-band OCT signals to lower-frequency signals, allowing for extended imaging range and adaptable working distance, enabling the system to image samples with surface variations beyond its conventional range by using a frequency down converter and analog-to-digital converter to maintain the signal within digitization capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional SS-OCT systems are used to image samples, then high resolution images can be obtained for shallow depths, but the imaging range is limited by light attenuation and cannot capture samples with surface variations exceeding the imaging range
Solution Approach 1:
The patent applies parameter changes by converting the OCT signal from high-frequency RF domain to lower-frequency baseband through frequency downconversion. This parameter transformation allows the signal to represent deeper optical path differences without being constrained by the original high-frequency limitations, effectively extending the imaging range while maintaining signal quality despite light attenuation.
2Length of stationary object
If the imaging range is extended to capture samples with larger surface variations, then the system can image deeper features, but the signal frequency becomes too high for effective digitization
Solution Approach 1:
The patent replaces mechanical frequency adjustment (tuning the entire system) with electronic frequency downconversion. By using a mixer to convert the high-frequency OCT signal to baseband electronically, the system achieves extended imaging range without increasing mechanical complexity or requiring physical reconfiguration of the optical path.
3Adaptability or versatility
If mechanical adjustments are made to extend the imaging range, then the system can adapt to different sample depths, but the system complexity and adjustment time increase
Solution Approach 1:
The patent eliminates mechanical adjustment mechanisms by implementing working distance adaptability through frequency downconversion. The electronic signal processing approach allows the system to adapt to different sample depths and surface variations without any mechanical moving parts, thereby maintaining simplicity while achieving versatility.
Solution Approach 2:
The patent uses parameter changes in the signal domain (frequency conversion) to achieve adaptability. By downconverting the OCT signal frequency based on the optical path difference, the system dynamically adapts to different working distances and sample configurations without mechanical intervention, simplifying the overall device architecture.
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 extends the imaging range and adaptability of the OCT system, allowing it to capture detailed images of samples with larger surface variations and uneven surfaces without the need for mechanical adjustments, improving depth mapping and profiling capabilities.
Implementation Method 1
The frequency down converter is configured to receive and down convert the OCT signal to a lower frequency signal
Implementation Method 2
The optical circuit is configured to probe the sample and generate an analog OCT signal representative of the sample
Data Source
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AI summary
An optical coherence tomography (OCT) system for imaging a sample is provided. The OCT system includes an optical circuit (24) and a digitization circuit (40). The optical circuit includes an interferometer (28) and is configured to probe the sample and generate an analog OCT signal representative of the sample. The digitization circuit (40) includes a frequency down converter (41) and an analog-to-digital converter (50). The digitization circuit is configured to receive, down convert and digitize the analog OCT signal, thereby outputting a digitized down converted signal. A method for imaging a sample is also provided. The method includes steps of optically probing the sample to generate the analog OCT signal representative of the sample and processing the analog OCT signal to obtain the digitized down converted signal.