Complex Master Slave Interferometry Signal Processing
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Solution Overview
Problem
Existing spectral domain interferometry and Master-Slave (MS) interferometry methods face limitations in axial resolution, sensitivity decay with depth, and the need for extensive data resampling, particularly due to phase loss and dispersion issues, which restrict the production of high-quality en-face OCT images and A-scans.
Innovation Solution
The Complex Master Slave (CMS) method processes complex-valued signals by generating Synthesised Complex Masks that conserve phase, allowing for axial complex-valued profiles without resampling, and compensates for dispersion without additional slabs, enabling the production of en-face OCT images and A-scans with improved axial resolution and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fourier transform is used to process interferometry signals, then depth resolved information can be obtained, but data resampling is required which increases processing complexity and loses phase information
Solution Approach 1:
The patent extracts only the necessary information (optical path difference and intensity) directly from the interferometry signal without performing full Fourier transform. By taking out only the required depth resolution data through peak detection in the autocorrelation function, it avoids the complexity of data resampling while maintaining measurement precision.
Solution Approach 2:
The patent introduces an autocorrelation function as an intermediary between the raw interferometry signal and the final depth information. This mediator allows direct extraction of optical path difference without requiring Fourier transform and associated data resampling, thus reducing processing complexity while preserving phase information.
2Device complexity
If Master Slave interferometry is used to avoid Fourier transform, then phase information is lost, but if Fourier transform is used, then phase information is preserved
Solution Approach 1:
The patent changes the processing parameter from intensity-only correlation to complex-valued correlation. By using complex-valued signals that retain phase information and applying it in the autocorrelation function, the system maintains phase information while avoiding Fourier transform complexity, thus resolving the contradiction between processing simplicity and information preservation.
3Reliability
If dispersion compensation slabs are added to the interferometer, then dispersion effects are corrected, but device complexity and alignment difficulty increase
Solution Approach 1:
The patent replaces the mechanical dispersion compensation system (physical slabs in the interferometer) with a computational approach. By using complex-valued signal processing and autocorrelation, dispersion effects are corrected through data processing rather than additional optical components, thus maintaining reliability while reducing device complexity and alignment difficulty.
4Adaptability or versatility
If channelled spectra are acquired at multiple depths, then en-face images can be produced, but the number of measurements increases processing time
Solution Approach 1:
The patent performs preliminary computation by pre-calculating and storing the autocorrelation function of the reference arm signal. When acquiring channelled spectra at multiple depths, this pre-computed autocorrelation is reused, significantly reducing processing time for generating en-face images while maintaining the ability to produce images at any desired depth.
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
CMS achieves enhanced axial resolution and stability by eliminating phase loss and dispersion effects, allowing for any number of en-face OCT images and A-scans with desired depth density, independent of initial measurements, and operates effectively in configurations where channelled spectra acquisition is challenging.
Implementation Method 1
analysing the spectrum of the interference signal produced between optical signal from an object under investigation and a local optical reference signal
Implementation Method 2
a Sp or SS interferometer (OCT) system consists mainly in an interferometer, 1, and a decoder, 10, to obtain depth resolved information from an object 13
Data Source
AI summary
The present invention related to an apparatus and method for master slave interferometry, referred to as Complex Master Slave (CMS). The method and apparatus can be used to provide complex-valued measurements of a signal reflected from an axial position inside an object or of signals reflected from points at several axial positions inside an object.