Multimode Swept-Source OCT Illumination for Lower Pixel Cross-Talk
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Solution Overview
Problem
Existing swept-source OCT systems face limitations in power distribution and spatial coherence, leading to pixel cross-talk and coherent artifacts, particularly in line-field and full-field imaging applications.
Innovation Solution
A tunable laser system that supports multiple spatial modes, preserving higher-order modes through free-space or multimode fiber coupling to an interferometer, resulting in a super-Gaussian illumination profile and reduced spatial coherence, which mitigates pixel cross-talk and coherent artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-mode laser source is used in swept-source OCT, then the laser output is highly coherent, but this causes pixel cross-talk and coherent artifacts in line-field and full-field imaging
Solution Approach 1:
The patent changes the spatial mode parameters of the laser source from single-mode to multi-mode operation. By supporting higher-order spatial modes (TEM01, TEM10, etc.) in addition to the fundamental mode, the system transforms the coherence properties of the light to reduce spatial coherence across the beam profile, thereby suppressing pixel cross-talk and coherent artifacts while maintaining temporal coherence for depth resolution
Solution Approach 2:
The patent creates a composite spatial mode structure by combining multiple transverse modes (fundamental TEM00 and higher-order modes) in a single laser beam. This composite mode structure achieves a super-Gaussian intensity profile that provides both high peak intensity and reduced edge coherence, effectively addressing the artifact problem while maintaining imaging performance
2Reliability
If higher-order spatial modes are supported in the laser cavity, then the power distribution becomes more uniform and spatial coherence is reduced, but the laser design becomes more complex
Solution Approach 1:
The patent modifies the laser cavity parameters (ridge width, ridge height, confocal parameter) to support multiple spatial modes. By adjusting these geometric parameters, the system enables higher-order modes without requiring complex additional components, achieving mode diversity through straightforward structural modifications to the semiconductor gain chip and cavity geometry
Solution Approach 2:
The patent transitions from single-mode operation to multi-mode operation by utilizing additional spatial dimensions (transverse modes) in the laser beam. This dimensional expansion provides more degrees of freedom for controlling the intensity profile and coherence properties, achieving uniform power distribution and reduced spatial coherence through natural mode mixing in the extended spatial domain
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
Improves signal-to-noise uniformity and reduces pixel cross-talk and coherent artifacts in OCT imaging, enhancing image quality and detector performance.
Implementation Method 1
a semiconductor gain chip configured during operation to lase in multiple spatial modes
Implementation Method 2
a free-space interferometer with free-space reference and sample arms that combines the sample and reference light to obtain interferometric signals
Data Source
AI summary
A full-field or line-field swept-source optical coherence tomography (OCT) system that uses a tilt-tuned cat's-eye laser whose semiconductor gain chip is dimensioned to lase in multiple spatial modes. The multimode output is preserved by free-space or multimode-fiber coupling from the laser to the interferometer, and is shaped by cylindrical line-forming optics to illuminate the sample with a long aspect-ratio line or across the field. The multimode operation produces a super-Gaussian, near flat-top intensity profile along the line or field and reduces spatial coherence, improving detector uniformity and lowering pixel cross-talk. Example implementations use a single-angled-facet gain chip with ridge width >3 μm and/or active-layer ridge height >2 μm, a thin-film interference filter tilt-scanned by a servoed galvanometer with encoder, and a line-scan camera to acquire parallel A-scans for B-scan formation. The approach maintains OCT advantages while relaxing single-mode constraints on the swept source and improving line-field and full-field image quality.