A detection device and method for extracting weak fluorescent signal in strong light background

Abstract

The application discloses a kind of detection device and method of weak fluorescence signal extraction in strong light background, belong to fluorescence signal detection technical field;The application is through the synergic control mechanism of SPD light path attenuation first-order regulation-control-stepping motor aperture second-order regulation-control-PMT gain voltage third-order regulation-control, in combination with temperature and humidity real-time acquisition and compensation model, realize the adaptive adaptation to dynamic strong light background;While constructing multidimensional signal state judgment logic, under the premise of avoiding photomultiplier tube overexposure, the real intensity of fluorescence is restored by three-level compensation coefficient fusion calculation.The application solves the problem that the existing fluorescence detection equipment is easy to overexposure in strong light environment, and the effective signal is covered, the total response time is controlled to be less than or equal to 300 ms, which significantly improves the sensitivity and reliability of detection, and can be widely applied to water quality algae monitoring, biomedical detection, environmental pollutant analysis and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of fluorescence signal detection technology, specifically relating to a detection device and method for adaptively extracting weak fluorescence signals against a strong light background. It can be applied to all scenarios that rely on fluorescence detection technology, such as water quality algae monitoring, biomedical detection, and environmental pollutant analysis. Background Technology

[0002] Fluorescence detection technology, with its advantages of high sensitivity and high specificity, has become a core technology for detecting weak signals. For example, in water algae monitoring, algae species can be identified and their concentration quantified by stimulating their own fluorescence properties. However, in practical applications, detection systems often face strong light background interference such as direct sunlight and strong artificial light sources, which severely restricts the deployment and use of instruments in daytime outdoor environments.

[0003] Most existing fluorescence detection equipment uses photomultiplier tubes (PMTs) as the core photoelectric conversion device. Most of these devices need to be used in dark rooms or low-light environments. In strong light scenarios, the problem of light intensity overexposure is likely to occur: when the incident light intensity exceeds the linear response range of the PMT, its output signal is fixed at the maximum value, and the subsequent filtering circuit cannot extract the weak modulated fluorescence signal in the form of AC component from the saturated signal.

[0004] Current solutions for strong light interference are mostly single-dimensional control methods, mainly including PMT gain adjustment and fixed attenuator optical path attenuation. While fixed attenuators can reduce incident light intensity, they cannot adapt to dynamic lighting environments, leading to excessive attenuation of the effective signal in low-light backgrounds. Single PMT gain adjustment is limited by the device voltage adjustment range; when the gain voltage is reduced to the minimum value and overexposure cannot be avoided, the control capability is lost. Therefore, there is an urgent need for a multi-dimensional control method that can adapt to dynamic lighting environments to solve the problem of extracting weak fluorescence signals in strong light backgrounds. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a detection device and method for adaptive extraction of weak fluorescence signals against a strong light background. This method achieves precise adaptation to dynamic light environments and complex temperature and humidity environments, preserving the complete information of weak fluorescence signals to the maximum extent while avoiding overexposure, thereby improving the sensitivity and reliability of detection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A detection device for adaptive extraction of weak fluorescence signals in strong light background includes an optical module, a photoelectric conversion module, a signal conditioning module, a data acquisition and control module, and a power supply module. The optical module includes an excitation source, an optical shutter-aperture assembly, an SPD optical attenuation lens, a 680nm narrowband filter, an optical window, and an optical path coupling assembly; the modulation frequency of the excitation source is 1kHz; the 680nm narrowband filter has a bandwidth of 10nm, a cutoff depth of OD06, and a transmittance of >95%; the SPD optical attenuation lens is installed behind the 680nm narrowband filter; the optical shutter-aperture assembly is located between the SPD optical attenuation lens and the photoelectric conversion module; the initial radius of the aperture is 5mm, and the adjustment range is 1~5mm. The photoelectric conversion module uses an H10722 type photomultiplier tube (PMT) with a gain range of 10. 3 -10 7 Maximum output voltage 5V, dark current ≤1nA; The signal conditioning module includes an LM324 operational amplifier with 1x gain, an AD8221 two-stage adjustable gain AC amplifier circuit, and an RC active bandpass filter circuit with a center frequency of 1kHz; the gain adjustment range of the AC amplifier circuit is 20-200 times, and the attenuation rate of the bandpass filter circuit is -20dB / decade. The data acquisition and control module is based on an STM32H743 MCU, equipped with an ADS1256 24-bit ADC, a DAC8552 16-bit DAC, an AHT30 temperature and humidity sensor, and a ULN2003 stepper motor driver chip; the ADC has a sampling rate of 1000 SPS and a resolution of 0.5 μV, and the temperature and humidity sensor has a temperature measurement accuracy of ±0.3℃ and a humidity measurement accuracy of ±2% RH. The power supply module is powered by 12V DC and outputs ±5V and 3.3V voltages via a DC-DC converter. It is also equipped with a dedicated 5V voltage regulator circuit for PMT, with ripple ≤0.001%.

[0007] Preferably, the shutter-aperture assembly adopts a blade-type aperture with a light transmission diameter accuracy of ±0.02mm. The matching micro stepper motor has a reduction ratio of 1:64, a step angle of 1.8°, and a driving voltage of 5V, with each step corresponding to a change in aperture radius of 0.01mm. The SPD optical attenuation lens is of type LSR-1010, with a response wavelength of 400-1100nm, a control voltage of 0-12V, a light transmittance of 0.5%-80%, and a response time of 3μs.

[0008] Preferably, the signal conditioning module divides the PMT output signal into two paths after isolation by an operational amplifier. One path is directly input to the ADC to acquire the DC component, and the other path is input to the ADC to acquire the AC component after DC blocking by a capacitor, AC amplification, and bandpass filtering. The driving circuit of the SPD optical attenuation lens outputs a 0-3.3V signal from the MCU's DAC, which is amplified in phase and then outputs a 0-12V control voltage.

[0009] A detection method for weak fluorescence signals adaptively extracted against a strong light background employs a three-level collaborative mechanism: primary control of the SPD optical path attenuation coefficient, secondary control of the stepper motor aperture, and tertiary control of the PMT gain voltage, combined with real-time temperature and humidity compensation. The method includes the following steps: S1. System Initialization: Start the AHT30 temperature and humidity sensor to collect initial environmental parameters, including the initial SPD transmittance T0 and initial humidity RH0; set the PMT initial gain voltage to 1V, the SPD initial control voltage to adjust the transmittance to 80%, the initial aperture radius to 5mm, and the ADC sampling parameters; complete dynamic calibration through a standard fluorescent light source and an environmental simulation unit to establish a coupled mapping model of PMT gain-voltage-temperature and humidity, and SPD transmittance-voltage-temperature and humidity. S2. Signal and Environmental Parameter Acquisition: The PMT converts the incident light signal into an electrical signal, which is then isolated and buffered by a 1x operational amplifier. The DC component U of the signal is synchronously acquired by a 24-bit ADC. DC With 1kHz AC component U AC The AHT30 collects ambient temperature (T) and humidity (RH) data in real time with a period of 100ms and uploads it to the MCU. S3. Multi-dimensional Status Judgment: The MCU integrates signal characteristics and temperature and humidity data to determine the lighting environment and device status, including: Overexposure to strong light: The signal contains only a DC component and U DC =5V; Too weak fluorescence: U DC <0.5V and AC component amplitude <0.5μV; Signal misalignment: DC and AC components coexist, and the waveform distortion of the AC component is >5%; Extreme overexposure: When the SPD has maximum attenuation, the aperture is at its smallest, and the PMT gain control voltage is 0.5V, U DC Still 5V; S4. Graded Control: For overexposure in strong light conditions, graded control is performed according to the priority of SPD attenuation adjustment > aperture adjustment > PMT gain adjustment, until U DC With a voltage of ≤4.9V and a complete AC component, the distortion is ≤5%. S5. Signal Compensation and Output: Calculate the attenuation coefficient of the three-level control, fuse them to obtain the total compensation coefficient K, substitute it into the fluorescence true intensity calculation formula to obtain the detection result and output it; if an extreme overexposure state is triggered, the overexposure alarm and processing procedure will be started.

[0010] Preferably, in step S4, the primary control is SPD attenuation regulation, specifically as follows: The initial control voltage of the SPD is corrected for temperature and humidity using the following formula: V = V0 × [1 + K] SPDT(T-T0)+K SPDRH (RH-RH0)], Where V is the current voltage; V0 is the initial voltage; K SPDT =0.001 / ℃; K SPDRH =0.0003 / % RH; The MCU increases the SPD control voltage in 0.05V steps at 5ms intervals until U... DC ≤4.9V and 1kHz AC component intact; if overexposure still occurs with a transmittance of 0.5% even when adjusted to the maximum SPD control voltage of 0V, trigger secondary control; otherwise, calculate the SPD attenuation coefficient α. SPD Furthermore, signal compensation is performed in conjunction with temperature and humidity correction coefficients.

[0011] Preferably, the coupled mapping model of SPD transmittance-voltage-temperature and humidity is as follows: T SPD (T,RH)=[T SPD0 -b×(12-V SPD )]×[1+K SPDT ×(T-25)+K SPDRH [×(RH-50)], Among them, T SPD0 T represents the initial transmittance. SPD0 =80%; b is the voltage attenuation coefficient, b=6.625%·V -1 V SPD SPD control voltage, 0V≤V SPD ≤12V; SPD attenuation coefficient α SPD The calculation formula is: α SPD =T SPDtarget (T,RH) / T SPD0 (T,RH), Among them, T SPDtarget The target transmittance of the SPD.

[0012] Preferably, in step S4, the secondary control is aperture adjustment, specifically: The miniature stepper motor rotates counterclockwise in 5-step units to reduce the aperture, with each step corresponding to a radius change of 0.01mm. Each adjustment is spaced 5ms apart, and the PMT signal is acquired until U... DC ≤4.9V; if overexposure persists even after adjusting to the minimum aperture radius of 1mm, trigger level 3 adjustment; otherwise, calculate the aperture attenuation coefficient α. A The signal compensation is completed by combining the SPD attenuation coefficient; The aperture attenuation coefficient α A The calculation formula is: αA =(r / r max ) 2 , Where r is the actual light-gathering radius of the aperture; r max r is the maximum radius of the aperture. max =5mm.

[0013] Preferably, in step S4, the third-level control is PMT gain adjustment, specifically as follows: The initial gain voltage of the PMT is corrected for temperature and humidity reference using the following formula: V = V × [1 + K] T ×(25-T)+K RH [×(50-RH)], Among them, K T =0.005 / ℃; K RH =0.001 / % RH; The MCU gradually decreases the PMT gain voltage in 0.05V steps at 5ms intervals, acquiring the signal in real time; if adjusted to the minimum gain voltage of 0.5V, the corresponding gain is 5×10. 3 At that time, U DC Calculate the PMT gain attenuation coefficient α if the voltage is ≤4.9V and the AC component is intact. PMT The signal compensation is completed by merging the coefficients of the first two levels; if it is still overexposed, an extreme overexposure alarm is triggered.

[0014] Preferably, the coupling mapping model of PMT gain-voltage-temperature and humidity for type H10722 is as follows: G(T,RH)=k×e (a·VG) ×[1+K T ×(T-25)+K RH [×(RH-50)], Where k is the gain coefficient, k = 1152; a is the voltage coefficient, a = 7.4594 V. -1 V G PMT gain voltage, 0.5V≤V G ≤1.2V; PMT gain attenuation coefficient α PMT The calculation formula is: α PMT =G target (T,RH) / G0 (T,RH), Where G0 is the initial state PMT gain; G target This represents the target gain for PMT.

[0015] Preferably, in step S5, the formula for calculating the true fluorescence intensity is: I Ftrue =(UACmeas ·K) / [G0 (T,RH)·T0 (T,RH)·R·T F ], Among them, U ACmeas The measured peak value of the AC component is given; R represents the PMT photosensitivity, R = 6.12 × 10⁻⁶. 8 V / lm; T F T represents the transmittance of the filter. F =95%; T0 is the initial SPD transmittance; Total compensation coefficient K=k PMT ×k SPD ×k A , where k PMT k is the gain compensation coefficient. PMT =1 / α PMT ;k SPD k is the SPD attenuation compensation coefficient. SPD =1 / α SPD ;k A k is the aperture compensation factor. A =1 / α A ; For the state of weak fluorescence, the control method is as follows: reduce the SPD control voltage to 0V in 0.05V steps, open the light shutter to increase the aperture with a micro stepper motor, increase the PMT gain voltage to 1.2V in 0.05V steps, and simultaneously amplify the AC circuit gain. For signal misalignment, the adjustment method is as follows: fine-tune the SPD control voltage to reduce the transmittance, and then reduce the aperture until the AC component waveform distortion is ≤5%.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects: 1. This invention constructs a three-level collaborative control mechanism of SPD-aperture-PMT, breaking through the limitations of existing single-dimensional control. It can adapt to dynamically changing strong light backgrounds and achieve stable detection within a light intensity range of 0~100000 lux, solving the problem of overexposure in strong light and enabling adaptive multi-dimensional control. Simultaneously, this invention establishes coupled mapping models of PMT gain-voltage-temperature and humidity, and SPD transmittance-voltage-temperature and humidity, enabling real-time correction of control parameters. It is adaptable to complex temperature and humidity environments ranging from -5℃ to 60℃ and 0% RH to 100% RH, achieving real-time temperature and humidity compensation and improving the environmental adaptability of the detection.

[0017] 2. This invention, while avoiding overexposure, uses a three-level compensation coefficient fusion calculation to restore the true fluorescence intensity, preserving the complete information of weak fluorescence signals to the maximum extent. The detection resolution can reach 0.5μV, with a relative error ≤3%, exhibiting high sensitivity and high reliability. Furthermore, all three levels of control in this invention employ an incremental stepping algorithm, with optimized control step size and interval, resulting in a total control response time ≤300ms, meeting the requirements for real-time detection.

[0018] 3. This invention establishes judgment and control logic for three non-ideal states: overexposure under strong light, weak fluorescence, and signal inaccuracy, achieving adaptive adaptation across all scenarios without manual intervention. This invention can be widely applied to all fields relying on fluorescence detection technology, such as water quality algae monitoring, biomedical detection, and environmental pollutant analysis. It is especially suitable for on-site detection in strong light environments, possessing extremely high practical and promotional value. Attached Figure Description

[0019] Figure 1 This is an overall framework diagram of the detection device of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] like Figure 1 As shown, a detection device for adaptive extraction of weak fluorescence signals in strong light background includes an optical module, a photoelectric conversion module, a signal conditioning module, a data acquisition and control module, and a power supply module. The optical module includes an excitation source, an optical shutter-aperture assembly, an SPD optical attenuation lens, a 680nm narrowband filter, an optical window, and an optical path coupling assembly; the modulation frequency of the excitation source is 1kHz; the 680nm narrowband filter has a bandwidth of 10nm, a cutoff depth of OD06, and a transmittance of >95%; the SPD optical attenuation lens is installed behind the 680nm narrowband filter; the optical shutter-aperture assembly is located between the SPD optical attenuation lens and the photoelectric conversion module; the initial radius of the aperture is 5mm, and the adjustment range is 1~5mm. The photoelectric conversion module uses an H10722 type photomultiplier tube (PMT) with a gain range of 10. 3 -10 7 Maximum output voltage 5V, dark current ≤1nA; The signal conditioning module includes an LM324 operational amplifier with 1x gain, an AD8221 two-stage adjustable gain AC amplifier circuit, and an RC active bandpass filter circuit with a center frequency of 1kHz; the gain adjustment range of the AC amplifier circuit is 20-200 times, and the attenuation rate of the bandpass filter circuit is -20dB / decade. The data acquisition and control module is based on an STM32H743 MCU, equipped with an ADS1256 24-bit ADC, a DAC8552 16-bit DAC, an AHT30 temperature and humidity sensor, and a ULN2003 stepper motor driver chip; the ADC has a sampling rate of 1000 SPS and a resolution of 0.5 μV, and the temperature and humidity sensor has a temperature measurement accuracy of ±0.3℃ and a humidity measurement accuracy of ±2% RH. The power supply module is powered by 12V DC and outputs ±5V and 3.3V voltages via a DC-DC converter. It is also equipped with a dedicated 5V voltage regulator circuit for PMT, with ripple ≤0.001%.

[0022] The shutter-aperture assembly adopts a blade-type aperture with a light transmission diameter accuracy of ±0.02mm. The matching micro stepper motor has a reduction ratio of 1:64, a step angle of 1.8°, and a driving voltage of 5V. Each step corresponds to a change of 0.01mm in aperture radius. The SPD optical attenuation lens is of type LSR-1010, with a response wavelength of 400-1100nm, a control voltage of 0-12V, a light transmittance of 0.5%-80%, and a response time of 3μs.

[0023] The signal conditioning module divides the PMT output signal into two paths after isolation by an operational amplifier. One path is directly input to the ADC to acquire the DC component, and the other path is input to the ADC to acquire the AC component after DC blocking by a capacitor, AC amplification, and bandpass filtering. The driving circuit of the SPD optical attenuation lens outputs a 0-3.3V signal from the MCU's DAC, which is amplified in phase and then outputs a 0-12V control voltage.

[0024] A detection method for weak fluorescence signals adaptively extracted against a strong light background employs a three-level collaborative mechanism: primary control of the SPD optical path attenuation coefficient, secondary control of the stepper motor aperture, and tertiary control of the PMT gain voltage, combined with real-time temperature and humidity compensation. The method includes the following steps: S1. System Initialization: Start the AHT30 temperature and humidity sensor to collect initial environmental parameters, including the initial SPD transmittance T0 and initial humidity RH0; set the PMT initial gain voltage to 1V, the SPD initial control voltage to adjust the transmittance to 80%, the initial aperture radius to 5mm, and the ADC sampling parameters; complete dynamic calibration through a standard fluorescent light source and an environmental simulation unit to establish a coupled mapping model of PMT gain-voltage-temperature and humidity, and SPD transmittance-voltage-temperature and humidity. S2. Signal and Environmental Parameter Acquisition: The PMT converts the incident light signal into an electrical signal, which is then isolated and buffered by a 1x operational amplifier. The DC component U of the signal is synchronously acquired by a 24-bit ADC. DC With 1kHz AC component U AC The AHT30 collects ambient temperature (T) and humidity (RH) data in real time with a period of 100ms and uploads it to the MCU. S3. Multi-dimensional Status Judgment: The MCU integrates signal characteristics and temperature and humidity data to determine the lighting environment and device status, including: Overexposure to strong light: The signal contains only a DC component and U DC =5V; Too weak fluorescence: U DC <0.5V and AC component amplitude <0.5μV; Signal misalignment: DC and AC components coexist, and the waveform distortion of the AC component is >5%; Extreme overexposure: When the SPD has maximum attenuation, the aperture is at its smallest, and the PMT gain control voltage is 0.5V, U DC Still 5V; S4. Graded Control: For overexposure in strong light conditions, graded control is performed according to the priority of SPD attenuation adjustment > aperture adjustment > PMT gain adjustment, until U DC With a voltage of ≤4.9V and a complete AC component, the distortion is ≤5%. In step S4, the primary control is SPD attenuation regulation, specifically as follows: The initial control voltage of the SPD is corrected for temperature and humidity using the following formula: V = V0 × [1 + K] SPDT (T-T0)+K SPDRH (RH-RH0)], Where V is the current voltage; V0 is the initial voltage; K SPDT =0.001 / ℃; K SPDRH =0.0003 / % RH; The MCU increases the SPD control voltage in 0.05V steps at 5ms intervals until U... DC ≤4.9V and 1kHz AC component intact; if overexposure still occurs with a transmittance of 0.5% even when adjusted to the maximum SPD control voltage of 0V, trigger secondary control; otherwise, calculate the SPD attenuation coefficient α. SPD And combine temperature and humidity correction coefficients to perform joint signal compensation; The coupled mapping model of SPD transmittance-voltage-temperature and humidity is as follows: T SPD (T,RH)=[T SPD0 -b×(12-V SPD )]×[1+K SPDT×(T-25)+K SPDRH [×(RH-50)], Among them, T SPD0 T represents the initial transmittance. SPD0 =80%; b is the voltage attenuation coefficient, b=6.625%·V -1 V SPD SPD control voltage, 0V≤V SPD ≤12V; SPD attenuation coefficient α SPD The calculation formula is: α SPD =T SPDtarget (T,RH) / T SPD0 (T,RH), Among them, T SPDtarget The target transmittance of the SPD; In step S4, the secondary adjustment is aperture adjustment, specifically: The miniature stepper motor rotates counterclockwise in 5-step units to reduce the aperture, with each step corresponding to a radius change of 0.01mm. Each adjustment is spaced 5ms apart, and the PMT signal is acquired until U... DC ≤4.9V; if overexposure persists even after adjusting to the minimum aperture radius of 1mm, trigger level 3 adjustment; otherwise, calculate the aperture attenuation coefficient α. A The signal compensation is completed by combining the SPD attenuation coefficient; The aperture attenuation coefficient α A The calculation formula is: α A =(r / r max ) 2 , Where r is the actual light-gathering radius of the aperture; r max r is the maximum radius of the aperture. max =5mm; In step S4, the third-level control is the PMT gain adjustment, specifically as follows: The initial gain voltage of the PMT is corrected for temperature and humidity reference using the following formula: V = V × [1 + K] T ×(25-T)+K RH [×(50-RH)], Among them, K T =0.005 / ℃; K RH =0.001 / % RH; The MCU gradually decreases the PMT gain voltage in 0.05V steps at 5ms intervals, acquiring the signal in real time; if adjusted to the minimum gain voltage of 0.5V, the corresponding gain is 5×10. 3 At that time, U DCCalculate the PMT gain attenuation coefficient α if the voltage is ≤4.9V and the AC component is intact. PMT The signal compensation is completed by merging the coefficients of the first two levels; if it is still overexposed, an extreme overexposed alarm is triggered. The coupling mapping model of PMT gain-voltage-temperature and humidity for the H10722 type is as follows: G(T,RH)=k×e (a·VG) ×[1+K T ×(T-25)+K RH [×(RH-50)], Where k is the gain coefficient, k = 1152; a is the voltage coefficient, a = 7.4594 V. -1 V G PMT gain voltage, 0.5V≤V G ≤1.2V; PMT gain attenuation coefficient α PMT The calculation formula is: α PMT =G target (T,RH) / G0 (T,RH), Where G0 is the initial state PMT gain; G target For PMT target gain; S5. Signal Compensation and Output: Calculate the attenuation coefficient of the three-level modulation, fuse them to obtain the total compensation coefficient K, substitute it into the fluorescence true intensity calculation formula to obtain the detection result and output it; if an extreme overexposure state is triggered, start the overexposure alarm and processing procedure. In step S5, the formula for calculating the true fluorescence intensity is: I Ftrue =(U ACmeas ·K) / [G0 (T,RH)·T0 (T,RH)·R·T F ], Among them, U ACmeas The measured peak value of the AC component is given; R represents the PMT photosensitivity, R = 6.12 × 10⁻⁶. 8 V / lm; T F T represents the transmittance of the filter. F =95%; T0 is the initial SPD transmittance; Total compensation coefficient K=k PMT ×k SPD ×k A , where k PMT k is the gain compensation coefficient. PMT =1 / α PMT ;k SPD k is the SPD attenuation compensation coefficient. SPD =1 / α SPD ;k Ak is the aperture compensation factor. A =1 / α A ; For the state of weak fluorescence, the control method is as follows: reduce the SPD control voltage to 0V in 0.05V steps, open the light shutter to increase the aperture with a micro stepper motor, increase the PMT gain voltage to 1.2V in 0.05V steps, and simultaneously amplify the AC circuit gain. For signal misalignment, the adjustment method is as follows: fine-tune the SPD control voltage to reduce the transmittance, and then reduce the aperture until the AC component waveform distortion is ≤5%.

[0025] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A detection device for adaptive extraction of weak fluorescence signals against a strong light background, characterized in that: It includes an optical module, a photoelectric conversion module, a signal conditioning module, a data acquisition and control module, and a power supply module; The optical module includes an excitation source, an optical shutter-aperture assembly, an SPD optical attenuation lens, a 680nm narrowband filter, an optical window, and an optical path coupling assembly; the modulation frequency of the excitation source is 1kHz; the 680nm narrowband filter has a bandwidth of 10nm, a cutoff depth of OD06, and a transmittance of >95%; the SPD optical attenuation lens is installed behind the 680nm narrowband filter; the optical shutter-aperture assembly is located between the SPD optical attenuation lens and the photoelectric conversion module; the initial radius of the aperture is 5mm, and the adjustment range is 1~5mm. The photoelectric conversion module uses an H10722 photomultiplier tube (PMT) with a gain range of 10. 3 -10 7 Maximum output voltage 5V, dark current ≤1nA; The signal conditioning module includes an LM324 operational amplifier with 1x gain, an AD8221 two-stage adjustable gain AC amplifier circuit, and an RC active bandpass filter circuit with a center frequency of 1kHz; the gain adjustment range of the AC amplifier circuit is 20-200 times, and the attenuation rate of the bandpass filter circuit is -20dB / decade. The data acquisition and control module is based on an STM32H743 MCU, equipped with an ADS1256 24-bit ADC, a DAC8552 16-bit DAC, an AHT30 temperature and humidity sensor, and a ULN2003 stepper motor driver chip; the ADC has a sampling rate of 1000 SPS and a resolution of 0.5 μV, and the temperature and humidity sensor has a temperature measurement accuracy of ±0.3℃ and a humidity measurement accuracy of ±2% RH. The power supply module is powered by 12V DC and outputs ±5V and 3.3V voltages via a DC-DC converter. It is also equipped with a dedicated 5V voltage regulator circuit for PMT, with ripple ≤0.001%.

2. The detection device for adaptive extraction of weak fluorescence signals under strong light background as described in claim 1 is characterized in that: The shutter-aperture assembly adopts a blade-type aperture with a light transmission diameter accuracy of ±0.02mm. The matching micro stepper motor has a reduction ratio of 1:64, a step angle of 1.8°, and a driving voltage of 5V. Each step corresponds to a change of 0.01mm in aperture radius. The SPD optical attenuation lens is of type LSR-1010, with a response wavelength of 400-1100nm, a control voltage of 0-12V, a light transmittance of 0.5%-80%, and a response time of 3μs.

3. The detection device for adaptive extraction of weak fluorescence signals under strong light background as described in claim 1 is characterized in that: The signal conditioning module divides the PMT output signal into two paths after isolation by an operational amplifier. One path is directly input to the ADC to acquire the DC component, and the other path is input to the ADC to acquire the AC component after DC blocking by a capacitor, AC amplification, and bandpass filtering. The driving circuit of the SPD optical attenuation lens outputs a 0-3.3V signal from the MCU's DAC, which is amplified in phase and then outputs a 0-12V control voltage.

4. A detection method for adaptively extracting weak fluorescence signals against a strong light background based on the detection device described in any one of claims 1-3, characterized in that, A three-level collaborative mechanism is adopted, consisting of primary control of the SPD optical path attenuation coefficient, secondary control of the stepper motor aperture, and tertiary control of the PMT gain voltage, combined with real-time temperature and humidity compensation, including the following steps: S1. System Initialization: Start the AHT30 temperature and humidity sensor to collect initial environmental parameters, including the initial SPD transmittance T0 and initial humidity RH0; set the PMT initial gain voltage to 1V, the SPD initial control voltage to adjust the transmittance to 80%, the initial aperture radius to 5mm, and the ADC sampling parameters; complete dynamic calibration through a standard fluorescent light source and an environmental simulation unit to establish a coupled mapping model of PMT gain-voltage-temperature and humidity, and SPD transmittance-voltage-temperature and humidity. S2. Signal and Environmental Parameter Acquisition: The PMT converts the incident light signal into an electrical signal, which is then isolated and buffered by a 1x operational amplifier. The DC component U of the signal is synchronously acquired by a 24-bit ADC. DC With 1kHz AC component U AC The AHT30 collects ambient temperature (T) and humidity (RH) data in real time with a period of 100ms and uploads it to the MCU. S3. Multi-dimensional Status Judgment: The MCU integrates signal characteristics and temperature and humidity data to determine the lighting environment and device status, including: Overexposure to strong light: The signal contains only a DC component and U DC =5V; Too weak fluorescence: U DC <0.5V and AC component amplitude <0.5μV; Signal misalignment: DC and AC components coexist, and the waveform distortion of the AC component is >5%; Extreme overexposure: When the SPD has maximum attenuation, the aperture is at its smallest, and the PMT gain control voltage is 0.5V, U DC Still 5V; S4. Graded Control: For overexposure in strong light conditions, graded control is performed according to the priority of SPD attenuation adjustment > aperture adjustment > PMT gain adjustment, until U DC With a voltage of ≤4.9V and a complete AC component, the distortion is ≤5%. S5. Signal Compensation and Output: Calculate the attenuation coefficient of the three-level control, fuse them to obtain the total compensation coefficient K, substitute it into the fluorescence true intensity calculation formula to obtain the detection result and output it; if an extreme overexposure state is triggered, the overexposure alarm and processing procedure will be started.

5. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 4, characterized in that, In step S4, the primary control is SPD attenuation regulation, specifically as follows: The initial control voltage of the SPD is corrected for temperature and humidity using the following formula: V=V0×[1+K SPDT (T-T0)+K SPDRH (RH-RH0)], Where V is the current voltage; V0 is the initial voltage; K SPDT =0.001 / ℃; K SPDRH =0.0003 / % RH; The MCU increases the SPD control voltage in 0.05V steps at 5ms intervals until U... DC ≤4.9V and 1kHz AC component intact; if overexposure still occurs with a transmittance of 0.5% even when adjusted to the maximum SPD control voltage of 0V, trigger secondary control; otherwise, calculate the SPD attenuation coefficient α. SPD Furthermore, signal compensation is performed in conjunction with temperature and humidity correction coefficients.

6. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 5, characterized in that, The coupled mapping model of SPD transmittance-voltage-temperature and humidity is as follows: T SPD (T,RH)=[T SPD0 -b×(12-V SPD )]×[1+K SPDT ×(T-25)+K SPDRH ×(RH-50)], Among them, T SPD0 T represents the initial transmittance. SPD0 =80%; b is the voltage attenuation coefficient, b=6.625%·V -1 V SPD SPD control voltage, 0V≤V SPD ≤12V; SPD attenuation coefficient α SPD The calculation formula is: α SPD =T SPDtarget (T,RH) / T SPD0 (T,RH), Among them, T SPDtarget The target transmittance of the SPD.

7. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 4, characterized in that, In step S4, the secondary adjustment is aperture adjustment, specifically: The miniature stepper motor rotates counterclockwise in 5-step units to reduce the aperture, with each step corresponding to a radius change of 0.01mm. Each adjustment is spaced 5ms apart, and the PMT signal is acquired until U... DC ≤4.9V; If overexposure persists even after adjusting to the minimum aperture radius of 1mm, trigger level 3 control; Otherwise, calculate the aperture attenuation factor α. A The signal compensation is completed by combining the SPD attenuation coefficient; The aperture attenuation coefficient α A The calculation formula is: α A =(r / r max ) 2 ， Where r is the actual light-gathering radius of the aperture; r max r is the maximum radius of the aperture. max =5mm.

8. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 4, characterized in that, In step S4, the third-level control is the PMT gain adjustment, specifically as follows: The initial gain voltage of the PMT is corrected for temperature and humidity reference using the following formula: V=V×[1+K T ×(25-T)+K RH ×(50-RH)], Among them, K T =0.005 / ℃; K RH =0.001 / % RH; The MCU gradually decreases the PMT gain voltage in 0.05V steps at 5ms intervals, acquiring the signal in real time; if adjusted to the minimum gain voltage of 0.5V, the corresponding gain is 5×10. 3 At that time, U DC Calculate the PMT gain attenuation coefficient α if the voltage is ≤4.9V and the AC component is intact. PMT The signal compensation is completed by merging the coefficients of the first two levels; if it is still overexposed, an extreme overexposure alarm is triggered.

9. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 8, characterized in that, The coupling mapping model of PMT gain-voltage-temperature and humidity for the H10722 type is as follows: G(T,RH)=k×e (a·VG) ×[1+K T ×(T-25)+K RH ×(RH-50)], Where k is the gain coefficient, k = 1152; a is the voltage coefficient, a = 7.4594 V. -1 V G PMT gain voltage, 0.5V≤V G ≤1.2V; PMT gain attenuation coefficient α PMT The calculation formula is: a PMT =G target (T,RH) / G0 (T,RH), Where G0 is the initial state PMT gain; G target This represents the target gain for PMT.

10. The detection method for adaptive extraction of weak fluorescence signals against a strong light background as described in claim 4, characterized in that, In step S5, the formula for calculating the true fluorescence intensity is: I Ftrue =(U ACmeas ·K) / [G0 (T,RH)·T0 (T,RH)·R·T F ], Among them, U ACmeas The measured peak value of the AC component is given; R represents the PMT photosensitivity, R = 6.12 × 10⁻⁶. 8 V / lm; T F T represents the transmittance of the filter. F =95%; T0 is the initial SPD transmittance; Total compensation coefficient K=k PMT ×k SPD ×k A , where k PMT k is the gain compensation coefficient. PMT =1 / α PMT ;k SPD k is the SPD attenuation compensation coefficient. SPD =1 / α SPD ;k A k is the aperture compensation factor. A =1 / α A ; For the state of weak fluorescence, the control method is as follows: reduce the SPD control voltage to 0V in 0.05V steps, open the light shutter to increase the aperture with a micro stepper motor, increase the PMT gain voltage to 1.2V in 0.05V steps, and simultaneously amplify the AC circuit gain. For signal misalignment, the adjustment method is as follows: fine-tune the SPD control voltage to reduce the transmittance, and then reduce the aperture until the AC component waveform distortion is ≤5%.

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