Polarization-Sensitive Optical Coherence Tomography Phase Modulation
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Solution Overview
Problem
Current polarization-sensitive optical coherence tomography (PS-OCT) systems are limited to using two polarization states, which prevents them from measuring the true three-dimensional structure of tissues, such as the sclera, and lacks high-resolution, in vivo imaging capabilities for monitoring myopia progression.
Innovation Solution
A PS-OCT system with a phase modulation system that generates three mutually orthogonal polarization states, allowing for the measurement of the full Mueller matrix of the sample. This system includes an electro-optic modulator, a polarizer at a specific rotation angle relative to the modulator's fast axis, and a signal generator for delivering a driving voltage with a sawtooth waveform, enabling the computation of the Mueller matrix and extraction of birefringence and structure information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current PS-OCT systems use two polarization states for imaging, then the system complexity is reduced and operation is simplified, but the measurement precision of true 3D tissue structure is insufficient
Solution Approach 1:
The patent changes the parameter of polarization state quantity from two to three, and adjusts the orientation angle parameter of the polarizer to specific values (17.6° or 38.1°) relative to the fast axis of the electro-optic modulator. This parameter optimization enables generation of three mutually orthogonal polarization states that provide complete Mueller matrix measurement capability while maintaining system feasibility
Solution Approach 2:
The patent introduces a polarizer as an intermediary component positioned at a specific angle between the electro-optic modulator and the sample arm. This intermediary element mediates the transformation of linearly polarized light into three mutually orthogonal polarization states, enabling full Mueller matrix measurement without directly complicating the core modulation system
2Measurement precision
If ex vivo imaging tools are used to examine sclera structure, then detailed structural information can be obtained, but tissue preparation distortion occurs and in vivo imaging is not achieved
Solution Approach 1:
The patent replaces mechanical/ex vivo imaging methods with an optical-based in vivo PS-OCT system. By using non-invasive optical radiation to probe sclera structure, the system eliminates the need for physical tissue removal and preparation, thereby avoiding tissue distortion while maintaining high measurement precision through polarization-sensitive detection
Solution Approach 2:
The patent performs preliminary calibration and characterization of the electro-optic modulator and polarizer configuration before actual imaging. By pre-establishing the optimal angle relationship (17.6° or 38.1°) between components, the system ensures accurate generation of three orthogonal polarization states during in vivo imaging, enabling direct measurement without subsequent tissue manipulation
3Loss of information
If a full 4×4 Mueller matrix measurement is performed, then complete tissue polarimetry properties are obtained, but the number of required measurements increases to three
Solution Approach 1:
The patent employs periodic modulation of the electro-optic modulator to cyclically generate three mutually orthogonal polarization states. This periodic action allows the system to acquire all necessary Mueller matrix elements through time-multiplexed measurements, completing the full 4×4 matrix measurement while maintaining efficient data acquisition
Solution Approach 2:
The patent uses dynamic control of the electro-optic modulator to switch between three polarization states rapidly. By dynamically adjusting the modulation parameters and utilizing the fast response of the electro-optic effect, the system acquires complete polarimetry information with minimal measurement time, resolving the trade-off between information completeness and measurement speed
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 reconstruction of the three-dimensional structure of the sclera at micron-scale resolution, providing new biomarkers for myopia screening and diagnosis, and improving the understanding of scleral changes in patients in vivo.
Implementation Method 1
an electro-optic modulator; a signal generator for delivering a driving voltage to the electro-optic modulator; wherein the rotation angle and the driving voltage are selected such that the phase modulation system generates three mutually orthogonal polarization states
Implementation Method 2
a polarizer arranged at a rotation angle relative to the fast axis of the electro-optic modulator
Implementation Method 3
an interferometric arrangement comprising a reference arm and a sample arm; a detector arranged to detect a signal generated by interference between a reference beam from the reference arm and a sample beam from the sample arm
Implementation Method 4
Polarization sensitive (PS) OCT produces contrast via the birefringent properties of tissues
Data Source
AI summary
A system for polarization-sensitive optical coherence tomography (PS-OCT) of a sample comprises an interferometric arrangement comprising a reference arm and a sample arm, the sample arm being arranged to emit optical radiation towards the sample; a phase modulation system arranged at an input to the sample arm; and a detector arranged to detect a signal generated by interference between a reference beam from the reference arm and a sample beam from the sample arm. The phase modulation system comprises: an electro-optic modulator; a polarizer arranged at a rotation angle relative to the fast axis of the electro-optic modulator; and a signal generator for delivering a driving voltage to the electro-optic modulator; wherein the rotation angle and the driving voltage are selected such that the phase modulation system generates three mutually orthogonal polarization states.