Fluorescence Measurement with Photon Counting and Background Correction
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Solution Overview
Problem
Fluorescence spectroscopy struggles with fluctuations in light source intensity, jitter, and background light interference, limiting its sensitivity and accuracy in detecting very small amounts of substances, especially in industrial applications where dynamic range and wavelength separation are challenging.
Innovation Solution
A fluorescence measuring device using a continuous light source with rectangular wave modulation, digital signal processing, and a photon counting system to correct for background light, enabling precise quantification by subtracting background photon counts and correcting for excitation light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a high-intensity light source is used to excite many molecules to obtain stronger fluorescence, then the fluorescence signal strength is improved, but the light source fluctuation and jitter increase
Solution Approach 1:
The patent implements a feedback mechanism by detecting the excitation light intensity with a reference detector and using this information to correct the fluorescence signal. The system continuously monitors the light source output and applies real-time corrections to compensate for intensity fluctuations and jitter, thereby maintaining measurement reliability while using high-intensity excitation light.
Solution Approach 2:
The patent introduces a reference detector as an intermediary element that measures the excitation light intensity separately from the fluorescence detection path. This intermediary measurement serves as a basis for correcting the fluorescence signal, allowing the system to maintain both high signal strength and high stability through mathematical correction of the measured values.
2Productivity
If pulsed light is used to increase the probability of transition to the electronically excited state, then the fluorescence excitation efficiency is improved, but the intensity fluctuation and time position jitter increase
Solution Approach 1:
The system uses feedback from the reference detector to measure actual pulsed light intensity and timing variations. By continuously monitoring the excitation light parameters and applying corrections to the fluorescence signal based on these measurements, the system compensates for pulsed light fluctuations and jitter, maintaining both high excitation efficiency and measurement precision.
3Reliability
If a semitransparent mirror is placed to collect reflected light for compensation, then the light source fluctuation correction is improved, but the device complexity and fogging susceptibility increase
Solution Approach 1:
The patent uses a reference detector as an intermediary to measure excitation light intensity without requiring complex optical elements like semitransparent mirrors. This simplified approach directly detects the light source output and uses the measurement for correction, reducing optical system complexity while maintaining effective fluctuation correction.
4Measurement precision
If an analog gate integration system is used for signal processing, then the weak signal detection capability is improved, but the jitter influence and DC level detection problem increase
Solution Approach 1:
The system implements feedback by measuring the actual excitation light parameters with a reference detector and using this information to correct the fluorescence signal processed through the analog gate integration system. This feedback mechanism compensates for jitter and timing variations, maintaining weak signal detection sensitivity while improving signal processing stability.
Solution Approach 2:
The patent replaces purely analog signal processing with a hybrid approach that incorporates digital correction based on reference detector measurements. By substituting some analog processing functions with digital correction algorithms, the system reduces the impact of jitter and timing errors while maintaining the sensitivity benefits of analog integration.
5Measurement precision
If photon counting is used to directly count pulse signals, then the sensitivity for extremely weak light is improved, but the dynamic range is reduced
Solution Approach 1:
The patent implements dynamic switching between photon counting mode and analog DC component measurement mode based on the light intensity level. For extremely weak light signals, the system uses photon counting to achieve high sensitivity, while for stronger signals, it switches to analog measurement to maintain an appropriate dynamic range. This dynamic adaptation allows the system to handle a wide variety of light intensities effectively.
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 device achieves highly sensitive and accurate quantification of trace substances with reduced calibration needs, offering a compact and cost-effective solution by leveraging digital signal processing and continuous light sources.
Implementation Method 1
a rectangular wave modulation circuit that modulates the continuous light source with a rectangular wave corresponding to turn-on and turn-off states
Implementation Method 2
Fluorescence spectroscopy, which obtains molecular information on a substance by measuring the fluorescence emitted when the substance absorbs light of a specific wavelength and is electronically excited and returns from a singlet excited state to the ground state
Implementation Method 3
a fluorescence detection unit that detects fluorescence emitted by the measurement target substance by a photon counting system
Data Source
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AI summary
[Problem to be Solved] Provided is a fluorescence measuring device that suppresses or eliminates fluctuations in a light source, problems of jitter associated with signal processing, and the influence of background light and performs highly sensitive and accurate quantification even when it is difficult to separate fluorescence from scattered light due to time difference or wavelength difference. [Solution] The fluorescence measuring device includes a continuous light source 2, an excitation light irradiation unit 3, an excitation light intensity detection unit 4, a photon counting type fluorescence detection unit 5, a rectangular wave modulation circuit 6 of the continuous light source, a timing circuit 7 that generates a rectangular wave pulse to be supplied to the rectangular wave modulation circuit and a gate pulse for signal processing, a gate counter circuit 8 that counts fluorescence photon pulse signals during the gate pulse period, a physical parameter information acquisition unit 9, and a concentration calculator 10. By digitally processing digital signals with this configuration and accurately digitally calculating and subtracting the current background photon count conversion value, it is possible to perform highly sensitive and highly accurate quantification by appropriately removing the influence of the background.