Optical Coherence Tomography Phase Polarization Detection
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Solution Overview
Problem
Optical coherence tomography (OCT) systems face challenges in simultaneously detecting phase and polarization signals due to complex conjugate ambiguity, polarization fading, and the loss of phase information during opto-electronic conversion, leading to image contamination and reduced imaging depth.
Innovation Solution
A method and system for analyzing optical beams in OCT systems, involving splitting input beams into probe and reference beams, manipulating the reference beam's polarization state, and mixing the beams to produce quadrature signal components, utilizing a coherent polarization analyzer with balanced photodetectors to extract phase and polarization information efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full decoding of the output signal is performed to obtain both phase and amplitude information, then measurement precision is improved, but device complexity increases due to the need for polarization quadrature encoding and phase stepping mechanisms
Solution Approach 1:
The patent extracts only the necessary phase information from the interferometric signal using a simplified detection scheme. Instead of fully decoding both polarization and phase components, the system extracts phase information through the phase of the complex signal directly, eliminating the need for complex polarization quadrature encoding and phase stepping mechanisms while maintaining measurement precision for the specific application.
Solution Approach 2:
The patent inverts the conventional approach by not attempting to separate polarization and phase information through complex encoding mechanisms. Instead, it processes the interferometric signal as a complex signal where phase information is directly available, reversing the traditional decomposition approach and simplifying the overall system architecture.
2Ease of operation
If square law detectors are used for opto-electronic conversion, then ease of operation is improved, but loss of information occurs as phase information is lost and only the real part of the signal is obtained
Solution Approach 1:
The patent introduces a complex signal representation as an intermediary that preserves phase information. Instead of directly converting the optical signal to electrical signals using square law detectors that lose phase information, the system uses complex signal processing to maintain and extract phase data, effectively mediating between the optical domain and electrical domain to prevent information loss.
3Productivity
If complex conjugate ambiguity is present in FD-OCT systems, then productivity is improved through spectral domain processing, but measurement precision deteriorates due to image contamination with double images and reduced imaging depth
Solution Approach 1:
The patent employs feedback mechanisms through complex signal processing to resolve the complex conjugate ambiguity. By processing the interferometric signal as a complex signal and using feedback from the phase information, the system can distinguish between positive and negative spatial frequencies, eliminating double images and improving imaging depth while maintaining the high productivity of spectral domain processing.
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 the simultaneous detection of phase and polarization signals with reduced processing overhead, providing robust and flexible integration into various OCT architectures, allowing for real-time imaging and minimizing offline processing.
Implementation Method 1
OCT relies on the coherent interference between a reference wave and a probe wave to measure the distances and thicknesses of a material
Implementation Method 2
manipulating the reference beam into a predetermined polarization state... mixing the return sample beam and reference beam producing a series of mixed beams... analyzing the polarization components of the series of mixed beams
Implementation Method 3
the phase information in the interferometric signal is lost upon detection and only the real part of the signal is obtained... necessitating the use of the full complex signal to remove the ambiguity
Data Source
AI summary
A method of analysis of a sample, including the steps of: (a) splitting an input optical beam into a probe beam and reference beam; (b) utilizing the probe beam to interrogate a sample and obtaining a return sample beam there from; (c) manipulating the reference beam into a predetermined polarization state; (d) mixing the return sample beam and reference beam producing a series of mixed beams; and (e) analyzing the polarization components of the series of mixed beams.