Swept-Source Laser Coherence Revival Artifact Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical coherence tomography (OCT) systems with swept-source lasers suffer from coherence revival artifacts due to back-reflections from optical surfaces, leading to unwanted interference signals that can misinterpret images and are difficult to eliminate.
Innovation Solution
The design of the swept-source laser incorporates phase modulation or optical path length variations to shift the coherence revival interference signal outside the detection bandwidth, using elements like electro-optic or acousto-optic modulators, piezo elements, and fiber stretchers to introduce frequency shifts or Doppler shifts, thereby reducing or eliminating coherence revival artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed laser cavity length is used in swept-source OCT, then the laser operates at discrete longitudinal modes, but this generates coherence revival artifacts when back-reflections occur at integer multiples of the cavity length
Solution Approach 1:
The patent applies dynamics by making the laser cavity length adjustable rather than fixed. The cavity length can be dynamically changed to prevent coherence revival artifacts from occurring at specific path lengths, thereby eliminating the harmful interference patterns while maintaining stable laser operation.
Solution Approach 2:
The patent changes the physical parameter of cavity length to resolve the contradiction. By varying the cavity length parameter, the system avoids the discrete longitudinal mode hopping that causes coherence revival artifacts, while still maintaining stable laser output for OCT imaging.
2Ease of operation
If the laser is swept in wavelength or frequency using a filter, then wavelength selection is achieved, but the laser hops between discrete modes generating a spectral comb function instead of smooth frequency distribution
Solution Approach 1:
The patent makes the cavity length dynamically adjustable during the sweeping process. This dynamic adjustment compensates for the discrete mode hopping, creating a smooth frequency distribution while maintaining ease of wavelength selection through filter-based tuning.
Solution Approach 2:
The patent changes the cavity length parameter in conjunction with filter tuning to achieve smooth frequency sweeping. By coordinating cavity length adjustments with filter wavelength selection, the system eliminates discrete mode effects and achieves continuous frequency distribution.
3Adaptability or versatility
If optical surfaces in the sample arm are present, then the OCT interferometer can be configured, but back-reflections from these surfaces cause unwanted interference signals when path lengths are mismatched by integer multiples of cavity length
Solution Approach 1:
The patent applies dynamics by making the cavity length adjustable in response to different optical configurations. This allows the system to adapt to various optical surface arrangements while dynamically preventing coherence revival artifacts by adjusting the cavity length away from problematic integer multiple relationships.
4Measurement precision
If the cavity length is adjusted to eliminate coherence revival artifacts, then image quality improves, but the tuning speed and flexibility of the laser may be affected
Solution Approach 1:
The patent changes the cavity length parameter in a controlled manner to eliminate coherence revival artifacts. By making small, precise adjustments rather than large changes, the system maintains high tuning speed while improving image quality through artifact elimination.
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 effectively reduces or eliminates coherence revival artifacts, improving image quality by shifting unwanted signals outside the detection bandwidth and allowing for more flexible laser cavity lengths, enabling faster tuning and reduced noise in OCT imaging.
Implementation Method 1
The design of the swept-source laser incorporates phase modulation or optical path length variations to shift the coherence revival interference signal outside the detection bandwidth
Implementation Method 2
using elements like electro-optic or acousto-optic modulators, piezo elements, and fiber stretchers to introduce frequency shifts
Implementation Method 3
using elements like electro-optic or acousto-optic modulators, piezo elements, and fiber stretchers to introduce frequency shifts
Implementation Method 4
introduce frequency shifts or Doppler shifts, thereby reducing or eliminating coherence revival artifacts
Data Source
AI summary
Swept source designs that eliminate or significantly reduce artifacts in optical coherence tomography are presented. One embodiment of the present invention is a source design that frequency shifts the coherence revival interference signal to a frequency larger than the A/D detection bandwidth or the post-processing bandwidth. In another embodiment, the introduced frequency shift is large enough to introduce a Doppler shift of the modes of the laser, which causes a blurring of the comb function, and thus eliminates or reduces mode hopping. In another embodiment, adjusting the cavity optical path length prior to data acquisition depending on the given optical layout configuration to reduce or eliminate coherence revival artifacts is described.