Refractive Index Measurement via Recessed Substrate Phase Detection
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Solution Overview
Problem
Existing methods for measuring the refractive index of a medium, such as the Abbe refractometer, face challenges including spectral, temporal, and spatial discrepancies, particularly when measuring media that surround cells for digital holographic microscopy (DHM) applications.
Innovation Solution
A method and system for determining the refractive index of a medium by using a substrate with recessed surface portions to propagate optical beams, which are then collected and used to generate signals indicative of the phase changes, allowing for real-time, quasi-real-time, and spatially resolved measurements of the refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an Abbe refractometer is used to measure the refractive index of a medium, then a refractive index value can be obtained, but the measurement is performed at a different wavelength (λAbbe) than the DHM system operating wavelength (λDHM), causing spectral discrepancies
Solution Approach 1:
The patent changes the measurement wavelength parameter from the traditional Abbe refractometer wavelength to the DHM system operating wavelength, enabling direct compatibility between refractive index measurement and DHM imaging without requiring wavelength conversion or correction factors
2Measurement precision
If the refractive index is measured using an Abbe refractometer before cell immersion, then a refractive index value is obtained, but the measurement is not performed at the actual moment when the medium surrounds the cells, causing temporal discrepancies
Solution Approach 1:
The patent enables continuous refractive index measurement of the medium throughout the DHM imaging process, maintaining uninterrupted monitoring of the medium's optical properties from before cell immersion through and after imaging, eliminating temporal gaps in measurement
3Measurement precision
If a conventional refractometer is used, then an average refractive index of the medium is obtained, but spatial variations in the refractive index of the medium surrounding different regions of the substrate cannot be detected
Solution Approach 1:
The patent segments the measurement field into multiple spatial regions corresponding to different areas of the substrate, enabling independent refractive index measurement for each region and revealing spatial heterogeneity in the medium's optical properties that would be averaged out in conventional measurements
4Ease of operation
If an Abbe refractometer is used to measure the refractive index, then a standalone measurement can be performed, but the measurement cannot be integrated into the DHM system, requiring separate measurement and calibration steps
Solution Approach 1:
The patent merges the refractive index measurement function directly into the DHM system by utilizing the DHM's existing optical components (beam splitter, detector array) and substrate structure, eliminating the need for a separate Abbe refractometer and simplifying the overall experimental setup while maintaining measurement capability
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 provides accurate and precise measurements of the refractive index, addressing the spectral, temporal, and spatial limitations of existing methods, and enabling in situ, time-resolved, and locally resolved refractive index mapping.
Implementation Method 1
collecting the first and second optical beams after said propagating and generating first and second signals being indicative of a phase of a respective one of the first and second collected optical beams
Implementation Method 2
determining a refractive index of said medium based on the first and second signals, the given depth, the given wavelength and a refractive index of the substrate
Data Source
AI summary
There is described a method for determining a refractive index of a medium. The method generally has providing a substrate having a surface, the surface having a first surface portion and a second surface portion spaced-apart from the first surface portion and recessed of a depth relative to the first surface portion; receiving the medium at least on the second surface portion; propagating a first optical beam towards the first surface portion and a second optical beam towards the second surface portion; collecting the first and second optical beams after said propagating and generating first and second signals being indicative of a phase of a respective one of the first and second collected optical beams; and determining a refractive index of said medium based on the first and second signals, the depth, a wavelength associated to the first and second optical beams and a refractive index of the substrate.