Raman Spectroscopy Apparatus for Heterogeneous Sample Analysis
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Solution Overview
Problem
Conventional Raman spectroscopy struggles to accurately measure heterogeneous substances with moving particles, as the signal is often contaminated by contributions from both the particles and the suspending medium, leading to reduced accuracy and detection limits due to fluorescence and shot noise.
Innovation Solution
A method and apparatus that utilize an indicator signal for elastic scattering to control the timing of illuminating light pulses and classify Raman scattered light pulses, allowing for the separation of object-related and medium-related spectra, thereby reducing the contribution of the suspending medium and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Raman measurement is used for heterogeneous substances, then the measurement covers both particle and medium contributions, but the measurement precision deteriorates due to signal contamination from the suspending medium
Solution Approach 1:
The patent segments the Raman measurement process by using an auxiliary detector to identify time intervals where only particle signals are present (when particles are in the measurement region but medium is excluded). This temporal segmentation allows separate acquisition of particle spectra and medium spectra, which are then combined to eliminate medium contamination in the final particle measurement.
Solution Approach 2:
The patent extracts the medium contribution from the total signal by measuring it separately during time intervals when particles are absent from the measurement region. This extracted medium spectrum is then subtracted from the combined particle-medium spectrum to obtain the pure particle Raman spectrum, effectively removing the harmful medium contribution.
2Reliability
If temporal averaging is used to measure heterogeneous substances, then the signal represents both components, but the detection limit worsens due to fluorescence and shot noise from the medium
Solution Approach 1:
The measurement process is segmented into two temporal phases: one where particles are present in the measurement region (providing particle signal) and one where particles are absent (providing only medium signal). By processing these segmented measurements separately and combining them through subtraction, the harmful fluorescence and shot noise from the medium are eliminated, improving reliability of particle detection.
Solution Approach 2:
The patent converts the continuously present medium signal, which normally acts as harmful noise, into a useful reference measurement. By intentionally measuring the medium alone during particle-absent intervals, the harmful medium contribution is transformed into a subtractable background signal that can be removed to reveal the pure particle spectrum, thereby improving detection limits.
3Measurement precision
If the measurement includes both particle and medium contributions, then the temporal average signal is obtained, but the measurement precision deteriorates for dilute samples and early cell growth stages
Solution Approach 1:
The patent uses temporal segmentation to isolate particle signals from medium signals. During particle-absent intervals, the medium is measured separately. This allows the system to achieve sufficient measurement precision even for dilute samples by subtracting the medium background, enabling detection of low-concentration particles that would otherwise be lost in the medium noise.
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 enables more accurate chemical analysis of heterogeneous substances by reducing the impact of the suspending medium and improving detection limits, allowing for precise measurement of Raman spectra even in dilute samples and during early stages of cell growth.
Implementation Method 1
an illuminating light source (LS1) and illuminating optics (10) arranged to illuminate a sample region (REG1) with illuminating light pulses (LB0)
Implementation Method 2
a spectral disperser (200) and a detector array (100) for measuring the spectral intensity distribution (I(λ)) of Raman scattered light pulses (LB1R) obtained from the sample region (REG1)
Implementation Method 3
an auxiliary detector (DET2) for providing an indicator signal (S2) indicative of elastic scattering coefficient of the sample region (REG1)
Data Source
AI summary
An apparatus, includes an illuminating light source and illuminating optics arranged to illuminate a sample region with illuminating light pulses, light gathering optics to gather Raman scattered light pulses from the sample region, a spectral disperser and a detector array for measuring the spectral intensity distribution of Raman scattered light pulses obtained from the sample region and an auxiliary detector for providing an indicator signal indicative of elastic scattering coefficient of the sample region. The apparatus is arranged to form a first output spectrum from the spectral intensity distribution of a first group of Raman scattered light pulses. The pulses of the first group of Raman scattered light pulses are obtained from the sample region when the indicator signal indicates that an object is located in the sample region.