Coherent Fiber Bundle Coherence Microscopy
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Solution Overview
Problem
Coherent fiber bundles are unsuitable for coherence imaging due to multimode waveguides that scramble the coherence signal, leak light between filaments, and induce modal dispersion, making it difficult to achieve effective subsurface imaging of internal tissues.
Innovation Solution
Reducing the spatial coherence of light before coupling it into the fiber bundle, using a mode scrambler and spatial filtering, and employing a Fizeau interferometer to derive an image of subsurface features by interfering the illuminating and scattered light, while utilizing a substantially monochromatic source with varying wavelength for improved imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent fiber bundles are used for subsurface imaging, then the ability to visualize internal tissue structures is improved, but the coherence signal is scrambled and modal dispersion occurs
Solution Approach 1:
The patent transforms the coherence imaging approach by changing from conventional transverse scanning to longitudinal depth scanning through wavelength modulation. This parameter change allows the system to exploit the fiber bundle's strength in depth resolution while avoiding its weakness in transverse coherence preservation. The longitudinal scanning approach matches the fiber bundle's natural capability to resolve axial distances through modal dispersion rather than treating it as a defect.
Solution Approach 2:
Instead of attempting to preserve transverse spatial coherence through the fiber bundle (the conventional approach), the patent inverts the strategy by deliberately using longitudinal depth information as the primary imaging dimension. The system scans through depth by modulating wavelength rather than scanning across the transverse plane, thereby converting the fiber bundle's modal dispersion from a harmful effect into a useful depth-resolution mechanism.
2Measurement precision
If conventional coherence imaging methods are used with fiber bundles, then subsurface imaging is attempted, but light leaks between filaments and coherence is lost
Solution Approach 1:
The patent extracts the depth-resolution capability from the fiber bundle's modal dispersion特性 and separates it from the transverse imaging function. By using wavelength modulation to scan only the longitudinal dimension, the system extracts useful depth information while ignoring the problematic transverse coherence issues. The imaging process focuses exclusively on axial depth scanning rather than attempting to preserve transverse spatial relationships.
Solution Approach 2:
The patent introduces wavelength modulation as an intermediary mechanism to achieve depth scanning without requiring transverse coherence preservation. Instead of directly scanning the beam across the fiber bundle transverse plane, the system uses wavelength as a mediator to selectively excite different longitudinal depths, thereby indirectly achieving depth scanning while avoiding the coherence loss problem entirely.
3Measurement precision
If transverse scanning is performed to achieve 3-D imaging, then volumetric information is obtained, but the complexity of the scanning apparatus increases
Solution Approach 1:
The patent replaces the mechanical transverse scanning system with a wavelength-based longitudinal scanning mechanism. Instead of using complex mechanical beam-steering apparatus to scan across the transverse plane, the system uses spectral modulation to scan through depth. This substitution dramatically simplifies the scanning apparatus while maintaining volumetric imaging capability through the fiber bundle's inherent depth-resolution特性.
Solution Approach 2:
The patent employs periodic wavelength modulation to systematically scan through different longitudinal depths. By modulating the laser wavelength in a periodic manner, the system achieves systematic depth sampling without requiring complex mechanical scanning. The periodic spectral scanning, combined with Fourier transformation of the interferometric signal, efficiently reconstructs the volumetric image with minimal mechanical complexity.
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
Enables 3-D structure acquisition of internal tissues at micron-scale resolutions in a fraction of a second, compatible with existing visible light imaging systems, and simplifies instrumentation, reducing costs and distortion artifacts.
Implementation Method 1
interfering the illuminating and scattered light to derive an image of subsurface features
Implementation Method 2
The fiber typically consists of a high refractive index core, and a low refractive index cladding, and the light is confined to the core by total internal reflection
Data Source
AI summary
Methods for employing coherent bundles of optical fibers, whether single- or multi-mode, for optical coherence tomography or optical coherence microscopy. Either a substantially monochromatic source or a broadband source is spatially decohered and/or spatially filtered prior to coupling into the fiber bundle for illumination of a sample. A scatter signal from features disposed beneath the surface of the sample is interfered with a reference signal derived, at either end of the fiber bundle, from the identical source of illumination.