Polarized Reflection Spectroscopy Without a Reference Path

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Solution Overview

Problem

Existing spectroscopy methods for determining optical properties of sample materials face challenges with intensity noise from light sources, particularly thermal emitters and quantum cascade lasers, which affect sensitivity and require additional reference measurements, introducing further fluctuations.

Innovation Solution

A method and apparatus utilizing polarized light states to determine optical properties by measuring and forming the ratio of intensities in different polarizations, eliminating the need for a reference path and reducing intensity noise through polarisation dependency of light reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If laser sources such as quantum cascade lasers are used, then high intensity and powerful light output is achieved, but intensity noise increases and sensitivity is reduced

Engineering Contradiction:

Improvelight intensityVSAvoidsensitivity

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the measurement parameter from absolute intensity to intensity ratio between two polarisation states. This transformation eliminates the impact of intensity noise and source power fluctuations, allowing the use of high-intensity laser sources without sacrificing sensitivity for detecting low concentrations of analytes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a reference measurement by measuring the intensity in a second polarisation state that serves as a copy of the first measurement path. This reference copy allows normalization of the primary measurement, canceling out common-mode noise and fluctuations from the light source.

Inventive Principle:

Principle #26Copying

2Reliability

If thermal emitters are used, then low intensity noise is achieved, but spectral power density is low and intensity with narrow-band filtering is reduced

Engineering Contradiction:

Improveintensity noiseVSAvoidspectral power density

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

By transforming the measurement to use intensity ratios rather than absolute intensities, the patent enables the use of high spectral power density sources like lasers. The parameter change makes the measurement insensitive to the absolute power level, allowing thermal emitters to be replaced with more powerful laser sources without introducing excessive noise.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If additional reference path is added for balanced detection, then reference measurement is achieved, but device complexity increases and additional fluctuations are introduced

Engineering Contradiction:

Improvereference measurementVSAvoidoptical path complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the single optical path serve dual functions by measuring both the sample signal and the reference signal through different polarisation states. This eliminates the need for a separate reference path, reducing device complexity while maintaining the ability to perform balanced detection and cancel fluctuations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the reference measurement function into the primary measurement path by using polarisation division. Instead of having separate optical paths for sample and reference, both measurements are combined in a single path with different polarisation states, simplifying the overall optical system.

Inventive Principle:

Principle #5Merging (Combining)

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

This approach significantly reduces or eliminates intensity noise, allowing for precise optical property determination without additional reference measurements, enhancing sensitivity and accuracy.

Implementation Method 1

determining a first intensity of light in a first polarisation state that was reflected by the sample material; determining a second intensity of light in a second polarisation state that was reflected by the sample material

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

spectroscopy based on attenuated and/or frustrated total internal reflection (ATR or FTIR)

Methodology Applied

Scientific EffectAttenuated total internal reflection: Total Internal Reflection

Implementation Method 3

different polarisations of the incident light wave and that the different polarisations also have a different phase offset

Methodology Applied

Scientific EffectPolarisation: Polarisation

Data Source

PatentUS12560539B2Method and apparatus for determining optical properties of a sample material

Publication Date: 2026.02.24 VIENNA UNIVERSITY OF TECHNOLOGY

AI summary

A method for determining optical properties of a sample material includes: determining a first intensity of light in a first polarization state that was reflected by the sample material; determining a second intensity of the light in a second polarization state that was reflected by the sample material; forming the ratio between the first intensity and the second intensity, or vice versa. Further, an apparatus for determining optical properties of a sample material, comprising at least one detector device for determining a first intensity of light in a first polarization state that was reflected by the sample material and for determining a second intensity of the light in a second polarization state that was reflected by the sample material and at least one computing unit for forming the ratio of the first intensity and the second intensity, or vice versa.