Common-Path Integrated Interferometer for Low Coherence Imaging
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Solution Overview
Problem
Existing sub-surface imaging systems based on planar lightwave circuit (PLC) interferometers face challenges with wavelength dependence, chromatic dispersion, and polarization mismatches, which degrade performance and reduce signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).
Innovation Solution
A low-coherence interferometry system utilizing a common-path interferometer with integrated optics, eliminating wavelength-sensitive components and directional couplers, and employing a shared optical path for reference and sample signals to mitigate wavelength dependence and chromatic dispersion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PLC-based interferometers with directional couplers are used, then integrated optics functionality is achieved, but wavelength dependence and chromatic dispersion degrade performance
Solution Approach 1:
The patent removes directional couplers from the PLC-based interferometer system. By extracting these wavelength-sensitive components, the system eliminates the source of wavelength dependence and chromatic dispersion while maintaining integrated optics functionality through alternative coupling mechanisms.
Solution Approach 2:
The patent introduces a common optical path as an intermediary between the sample arm and reference arm. This common path allows both signals to traverse the same optical components, thereby eliminating differential chromatic dispersion and wavelength dependence that plague traditional separate-path configurations.
2Measurement precision
If separate paths for reference and sample signals are used, then interferometric measurement is enabled, but polarization mismatches and chromatic dispersion occur
Solution Approach 1:
The patent merges the reference arm and sample arm into a single common optical path. By combining these previously separate paths, the system ensures that both signals experience identical polarization and chromatic dispersion conditions, eliminating mismatches while preserving interferometric measurement capability.
Solution Approach 2:
The patent creates equipotential conditions for the reference and sample signals by having them traverse the same optical path. This ensures equal exposure to polarization effects and chromatic dispersion, making the optical conditions equivalent for both measurement beams.
3Ease of operation
If wavelength-sensitive components are included, then optical signal routing is achieved, but SNR and CNR are reduced
Solution Approach 1:
The patent extracts and removes wavelength-sensitive components from the optical signal routing path. By eliminating these components, the system achieves signal routing through wavelength-insensitive mechanisms, thereby preserving both routing functionality and high signal-to-noise ratio.
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
The system achieves improved performance with reduced wavelength dependence, enhanced SNR and CNR, and cost-effectiveness by eliminating the need for directional couplers, resulting in compact and efficient sub-surface imaging.
Implementation Method 1
The return signals from the reference and sample arms are combined at a beam combiner to form a signal that generates an interference pattern at a detector. Light that travels the same length in each of the reference arm and sample arm constructively recombines to form high-intensity signals
Implementation Method 2
These 'surface waveguides' typically include a core of a first material that is surrounded by a second material having a refractive index that is lower than that of the first material. The change in refractive index at the interface between the materials enables reflection of light propagating through the core, thereby guiding the light along the length of the waveguide
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A low coherence interferometry imaging system comprising a common-path interferometer that is at least partially integrated as part of a planar lightwave circuit is disclosed. Imaging systems in accordance with the present invention are implemented in integrated optics without the inclusion of highly wavelength-sensitive components. As a result, they exhibit less wavelength dependence than PLC-based interferometers of the prior art. Further, the common-path interferometer arrangement of the present invention avoids polarization and wavelength dispersion effects that plague prior-art PLC-based interferometers. Still further, an integrated common-path interferometer is smaller and less complex than other integrated interferometers, which makes it possible to integrate multiple interferometers on a single chip, thereby enabling multi-signal systems, such as plane-wave parallel OCT systems.