Multi-Threshold DSP for Raman Spectroscopy Photon Counting
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Solution Overview
Problem
Raman spectroscopy faces limitations in detecting low-Raman yield samples due to the low intensity of the Raman phenomenon, leading to missed photon contributions when using single-threshold detectors, which limits sensitivity and efficiency, especially in the middle ground between strong and weak scatterers.
Innovation Solution
A multi-photon counting approach using a high-speed data acquisition system and multi-threshold Digital Signal Processing (DSP) algorithm to differentiate photon arrival events by amplitude and time, enabling the detection of multiple photons and improving sensitivity and noise rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-threshold detector is used to discern photon arrivals, then the detection algorithm is simple and binary, but photons in excess of the threshold are ignored and the detector becomes saturated, losing the potential contribution of additional photons
Solution Approach 1:
The patent divides the single threshold into multiple thresholds (first threshold, second threshold, third threshold) to segment the photon detection ranges. This segmentation allows the system to distinguish between different numbers of photons (single-photon, two-photon, multi-photon events) by comparing the output signal against these segmented thresholds, thereby resolving the contradiction between simple detection and accurate multi-photon counting.
2Ease of operation
If a single-threshold detector is used, then the system is easy to operate, but it cannot detect multiple photons arriving within the same time frame, limiting sensitivity
Solution Approach 1:
The patent introduces dynamic adjustment of thresholds and time windows based on signal characteristics. The system dynamically selects which threshold comparison to perform and adjusts the time window for photon arrival detection, enabling flexible adaptation to different photon flux conditions while maintaining ease of operation through automated decision-making.
3Measurement precision
If photon counting is used to assess weak scatterers, then the detection sensitivity for low-Raman yield samples is improved, but the system cannot effectively observe strong scatterers when the detector is saturated
Solution Approach 1:
The patent creates a universal detection system that can handle both weak and strong scatterers through multi-threshold analysis. The same detector and algorithm framework universally applies to all scatterer strengths by selecting appropriate threshold comparisons, eliminating the need for separate optimization regimes and extending the adaptable range from weak to strong scatterers.
4Measurement precision
If the detector operates in photon counting mode for low-Raman yield samples, then the test sensitivity is improved, but the test duration increases due to the need to accumulate sufficient photon statistics
Solution Approach 1:
The patent uses partial action by implementing multiple thresholds rather than requiring complete accumulation of photon statistics. By detecting photon arrivals at different threshold levels, the system obtains sufficient statistical information more quickly, reducing the excessive accumulation time while maintaining sensitivity through the multi-level detection approach.
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 multi-photon counting algorithm increases system sensitivity, allows lower concentration detection, and extends the analysis limit for high Raman-yield compounds, shifting the saturation threshold to higher concentrations, as demonstrated by analyses of nitrate, isopropanol, and rhodamine 6G solutions.
Implementation Method 1
photons that become inelastically scattered by the sample are observed... transmission to a light sensor that assesses the intensity of scattered returns
Data Source
AI summary
A method of determining the contributions of multiple incident photons to an output of a sensor, including providing a photonic sensor having a sensor input and capable of generating an electrical signal proportional to a number of photons interacting with the photonic sensor input as a function of time, calibrating the photonic sensor such that a response of the photonic sensor to a single photon detected is in a waveform having an amplitude and a time, wherein the product of the amplitude and the time is statistically bounded, determining a probabilistic boundary between one or more of electrical, optical, and thermal sources of noise of the sensor, acquiring a response wave form from the photonic sensor through analog-to-digital conversion with a resolution in amplitude and time corresponding to accuracy required in quantifying the response wave form, storing each acquired response wave form, individually, in a format selected from the group consisting of real-time and buffered packets in digital form, and determining a total count of likely photon arrivals for a specific time resolved acquisition.