Portable Raman spectrum measuring device for petroleum heavy metal ion detection

Abstract

The invention discloses a portable Raman spectrum measuring device for petroleum heavy metal ion detection, which belongs to the technical field of petroleum exploitation and processing, and comprises a light source module, a wavelength modulation module, an excitation light path module, a confocal detection module, an imaging module, a data processing module, an image processing module, an automatic focusing module and a portable shell, the fiber bragg grating can accurately adjust the excitation wavelength, and the influence of wavelength deviation on the detection precision is reduced; the contrast ratio and the sensitivity of Raman signals can be effectively improved through multi-wavelength excitation and differential signal processing and a displacement excitation Raman differential spectrum technology; the device provided by the invention can effectively improve the portability, accuracy and experimental efficiency of Raman spectrum detection, is suitable for crude oil pollution detection requirements in oil exploitation and processing processes, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploitation and processing, and in particular relates to a portable Raman spectrum measuring device for detecting petroleum heavy metal ions. Background Art

[0002] As the "blood" of modern industry, oil plays an important role in industrial production, transportation and other aspects. However, the accompanying oil pollution cannot be ignored, among which heavy metal ion pollution in oil is one of the most harmful. During the oil refining and processing process, if the heavy metals (such as nickel, vanadium, lead, mercury, etc.) contained in crude oil, semi-finished oil and finished oil reach a high enough concentration, it will have an important impact on the determination of oil processing plans, the service life of catalysts, wear and corrosion of equipment pipelines, product quality and environmental protection requirements. The impact on the oil processing process is mainly reflected in the following aspects: 1. Impact on catalysts; Catalyst poisoning: Heavy metal ions can have a toxic effect on catalysts used in petroleum processing. During catalytic cracking, hydrocracking and other oil refining processes, heavy metal ions can react with the catalyst surface, causing the catalyst to deactivate, which in turn affects the reaction rate and product yield.

[0003] Reduced catalyst life: Heavy metal ions can damage the active surface of the catalyst, reduce the active sites of the catalyst, thereby reducing its efficiency, shortening the catalyst life and increasing the cost of replacement and maintenance.

[0004] Formation of undesirable by-products: Catalyst poisoning can lead to incomplete or reduced selectivity of some reactions, resulting in the production of some unwanted by-products, which can reduce the quality of refined products.

[0005] 2. Product quality decline; Reduced product stability: Heavy metal ions may react with other components during the petroleum refining process to produce unstable compounds or precipitates, which in turn affect the stability of the final product (such as gasoline, diesel, etc.). For example, lead ions can react with other components in gasoline and reduce the stability of the fuel.

[0006] 3. Equipment corrosion; Mercury can be corrosive to refinery equipment, especially under conditions of high temperature and pressure, which can lead to equipment damage and downtime. For example, mercury reacts with metals in refinery equipment to form amalgams, which accelerates corrosion of equipment.

[0007] 4. Environmental pollution; Heavy metal ions enter the environment through waste gas and wastewater emissions from petroleum refining and processing, causing widespread pollution to the air, water sources and soil. Not only will they contaminate plants and animals through water sources, but they can also be transmitted through the food chain, ultimately affecting human health.

[0008] Traditional methods for detecting heavy metals in petroleum, such as atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, X-ray fluorescence, and inductively coupled plasma spectrometry, have high sensitivity and accuracy. However, these methods require tedious and time-consuming sample pretreatment processes such as digestion, concentration, and separation, which increase the complexity of the operation, may cause sample contamination, and may affect the accuracy. In addition, these methods rely on expensive and bulky equipment and are not suitable for field operations. Therefore, Raman spectrometers are used for real-time, in-situ, high-sensitivity detection of heavy metals in petroleum and to reduce random errors.

[0009] Existing Raman spectrometer solutions usually use multi-wavelength excitation sources or external cavity semiconductor lasers to achieve wavelength modulation, but these solutions have some defects that are not conducive to portable design. Specifically, when using a laser diode array as a multi-wavelength excitation source, multiple independent lasers are required, which makes the system complex and increases the volume, making it unsuitable for portable applications; in addition, when switching wavelengths, the laser diode array has high optical alignment requirements and is prone to errors, which in turn affects the signal quality. Although external cavity semiconductor lasers can achieve wavelength tuning, their mechanical adjustment devices are relatively complex, have a slow response speed, and are easily affected by environmental changes, resulting in poor wavelength stability and difficulty in meeting the needs of fast switching.

[0010] In addition, current portable Raman spectrometers are mainly used for simple chemical analysis (mostly solid blocks or powders), and most of them are in high concentrations, which do not require overly complex optical adjustments and image acquisition, so imaging and autofocus functions are not required. However, when testing petroleum liquids, if current portable Raman spectrometers are used, a series of challenges may be faced. Petroleum liquid samples usually have complex compositions and low concentrations of contaminants such as heavy metal ions, which requires higher detection sensitivity and precise focus control. Due to the poor uniformity of liquid samples and the possible dynamic flow or stratification, traditional portable Raman spectrometers are difficult to accurately locate the area to be analyzed without imaging and autofocus functions, thus affecting the accuracy and reliability of the signal. Petroleum liquid samples are often viscous, and the surface may be uneven or have contaminants. Traditional spectrometers lack autofocus functions and cannot cope with these changes, resulting in focal length deviation, which affects the quality and resolution of Raman signals. Summary of the invention

[0011] In view of the above problems existing in the prior art, the present invention proposes a portable Raman spectrum measuring device for detecting heavy metal ions in petroleum, which has a reasonable design, solves the shortcomings of the prior art and has good effects.

[0012] A portable Raman spectrum measuring device for detecting heavy metal ions in petroleum, comprising a light source module, a wavelength modulation module, an excitation light path module, a confocal detection module, an imaging module, a data processing module, an image processing module, and an autofocus module; The light source module includes a laser and a laser modulation circuit. The laser modulation circuit is used to control the switching operation of the laser and adjust the output power to ensure the stability of the output beam. The wavelength modulation module is used to realize accurate modulation of the wavelength of the optical signal, and includes first and second optical fiber couplers, an optical circulator, a fiber Bragg grating and a piezoelectric driver, wherein the fiber Bragg grating is connected to the piezoelectric driver through a fixture; The excitation optical path module is used to ensure that the laser is accurately focused on the target area of ​​the microfluidic chip, and includes a collimating lens, a narrow bandpass filter, a first dichroic mirror, a focusing objective lens, a microfluidic chip, and a sample stage, and the microfluidic chip is arranged on the sample stage; The confocal detection module is used to collect and detect Raman scattered light generated by the petroleum sample, and includes a second dichroic mirror, a high-pass filter, a coupling objective lens and a fiber optic spectrometer; The imaging module is used to collect images of the microfluidic chip substrate in real time, and includes an imaging lens and a CCD camera; The data processing module is used to process and analyze the collected Raman spectrum data; The image processing module is used to process the collected image of the microfluidic chip substrate to obtain an image clarity evaluation value; The autofocus module is used to analyze the clarity evaluation value of the image and drive the sample stage to move to adjust the focus position of the sample; The laser modulation circuit is connected to the laser, the laser is connected to the first port of the optical circulator through the first optical fiber coupler, the second port of the optical circulator is connected to the second optical fiber coupler and the fiber Bragg grating in sequence, the laser output from the third port of the optical circulator enters the optical path structure, the optical path structure includes an excitation optical path, a signal collection optical path and an imaging optical path, the excitation optical path includes a collimating lens, a narrow bandpass filter, a first dichroic mirror and a focusing objective lens in sequence, the signal collection optical path includes a focusing objective lens, a first dichroic mirror, a second dichroic mirror, a high-pass filter and a coupling objective lens in sequence, and the imaging optical path includes a focusing objective lens, a first dichroic mirror, a second dichroic mirror and an imaging lens in sequence; the laser is focused to the microfluidic chip through the laser optical path, the generated Raman scattered light enters the optical fiber spectrometer through the signal collection optical path in one path, the optical fiber spectrometer is connected to the data processing module, and the other path is focused to the CCD camera through the imaging optical path, and the CCD camera is connected to the image processing module and the autofocus module in sequence.

[0013] Furthermore, the laser modulation circuit controls the start-up and laser output power of the laser to emit a laser light source, which is coupled to the first port of the three-way optical circulator through the first optical fiber coupler, and the optical circulator sends the light beam to the fiber Bragg grating through the second port; The piezoelectric driver applies different stresses to the fiber Bragg grating to modulate the laser wavelength. A part of the spectrum of the light beam is coupled to the optical path in the form of a single-mode fiber through the second fiber coupler, reflected back to the optical circulator, and output from the third port, and another part of the spectrum exits the optical path through the fiber Bragg grating. The laser light source output from the third port of the optical circulator is collimated by a collimating lens, the collimated laser beam is filtered by a narrow bandpass filter, and is focused to the sample on the microfluidic chip by a first dichroic mirror and a focusing objective lens, so as to excite the sample to generate Raman scattered light, and the scattered light contains the spectral information of the sample, that is, characteristic information; The Raman scattered light is collected by a focusing objective lens and then divided into two paths, one of which is filtered by the first and second dichroic mirrors and a high-pass filter, and then coupled to a single-mode optical fiber through a coupling objective lens, and finally detected by a fiber optic spectrometer to generate a Raman spectrum signal; The other path is reflected by the first dichroic mirror and the second dichroic mirror, and then focused to the photosensitive element of the CCD camera through the imaging lens to generate an image of the microfluidic chip substrate; the image processing module calculates the image clarity evaluation value according to the image clarity evaluation algorithm, and feeds the result back to the autofocus module; the autofocus module adjusts the position of the sample stage according to the feedback signal to ensure that the sample is always in the best focus state; The data processing module preprocesses the Raman spectral signals collected by multi-wavelength excitation light. The preprocessing includes filtering, denoising and baseline correction, and then performs differential and spectral restoration processing to obtain Raman spectral signals with high signal-to-noise ratio. Finally, the Raman spectral signals are analyzed.

[0014] Furthermore, the laser is a 785 nm Raman laser, the fiber Bragg grating is embedded in a fixture, the fixture is connected to a piezoelectric driver, and the piezoelectric driver controls the deformation of the fixture through an electrical signal, thereby changing the strain of the fiber Bragg grating.

[0015] Furthermore, the laser modulation circuit includes a microcontroller, a switch control unit, a signal feedback unit, and a power adjustment unit; The switch control unit adopts a field effect tube circuit to achieve fast switching operation of the laser at high frequency and high current under a relatively small control voltage; The signal feedback unit monitors the laser operating current and operating temperature in real time through a photodiode and a thermistor to prevent the laser from being damaged due to overpower or overheating. The image processing module monitors the overexposure of the collected image in real time. The power regulation unit analyzes the feedback signal and integrates the temperature control module and the current control module to realize the temperature control and output power regulation of the laser component.

[0016] Furthermore, the central wavelength of the fiber Bragg grating is 785 nm. By controlling the structural parameters of the fiber Bragg grating, the laser wavelength is adjusted. When the piezoelectric driver does not apply stress to the fiber Bragg grating, the wavelength expression is: (1); in, is the Bragg wavelength, is the refractive index of the optical fiber, is the period of the fiber Bragg grating; When a piezoelectric actuator applies stress to a fiber Bragg grating, the wavelength changes by The expression is: (2); in, is the sensitivity coefficient of refractive index to strain, It's strain. is the thermal expansion coefficient of the silica fiber, is the refractive sensitivity index to temperature, is the amount of temperature change; to minimize thermal effects in the current design, the fiber Bragg grating is bonded to the piezoelectric actuator with an epoxy resin with a low thermal expansion coefficient and low thermal conductivity. In addition, the piezoelectric actuation time and measurement time are very short, thus limiting the heat generated by the unit.

[0017] Furthermore, the first dichroic mirror reflects the excitation light and transmits the Raman scattered light, and the second dichroic mirror transmits the Raman scattered light and reflects the Rayleigh scattered light and other stray light, thereby ensuring that only the Raman scattered light enters the CCD camera for detection.

[0018] Furthermore, the image processing module performs clarity analysis on the collected image according to the image clarity evaluation algorithm, and calculates a clarity evaluation value E; The autofocus module uses a focusing algorithm to accurately adjust the position of the sample stage to ensure that it is always in the best focus state. The focusing algorithm is an improved hill climbing search algorithm, which is implemented by the following steps: Step 1: Set the initial focus position to a preset sample height; Step 2: Capture an image at the initial focus position and calculate the clarity evaluation value; Step 3: The sample stage moves with the initially set step length d. If the clarity evaluation value increases, it continues to move forward; if the clarity evaluation value decreases, it is determined to have passed the focus position and returns to the previous step position with the original step length; Step 4: Reduce the step length to 0.9d, and the sample stage moves forward at the new step length; Step 5: Repeat steps 3 and 4 until the sample stage movement step is less than the set step threshold, and the image is judged to be in the best clarity state, the sample has reached the focal position, and precise focusing is completed.

[0019] Furthermore, in the data processing module, when the piezoelectric driver applies different stresses to the fiber Bragg grating to modulate two lasers of different wavelengths, the differential and spectrum restoration processing is specifically as follows: The total spectral signal detected by the fiber optic spectrometer Including Raman spectrum part and fluorescence background part, the expression is: (3); in, and represent the intensity of Raman light and fluorescence background, respectively. For the Bragg wavelength, ; Differential Raman spectroscopy The formula is: (4); When the excitation wavelength has an extremely narrow bandwidth, the Dirac function Indicates that the spectral signal It is expressed as: (5); Then formula (3) is expressed as: (6); Simplified to: (7); in, is the difference in wavelength of the two excitation lights; make ,but: (8); According to Fourier transform, we get: (9); make , then: (10); Through the inverse Fourier transform, we get: (11).

[0020] Beneficial technical effects brought by the present invention: The fiber Bragg grating is directly integrated into the portable Raman spectrometer, which simplifies the complexity of laser source and optical path alignment, significantly reduces the size of the device, and is suitable for real-time detection on site and convenient for mobile use. The fiber Bragg grating is modulated by mechanical strain technology, which greatly shortens the wavelength switching response time, thereby improving the switching efficiency of the excitation light source; Fiber Bragg gratings can achieve precise adjustment of the excitation wavelength, improve the wavelength stability and accuracy of the laser light source, optimize the excitation efficiency of the Raman signal, reduce the impact of wavelength deviation on detection accuracy, and further improve the reliability of the detection results; Through multi-wavelength excitation and differential signal processing, displacement excitation Raman differential spectroscopy technology can effectively improve the contrast and sensitivity of Raman signals, reduce background noise and interference signals, enhance the detection ability of low-concentration target substances, and ensure more accurate analysis results; Equipped with an autofocus module, the sample stage is accurately adjusted based on the hill climbing search algorithm to ensure optimal focus, improve imaging quality and data stability, and is suitable for high-precision Raman spectroscopy detection; Through the above technical solutions and advantages, the device provided by the present invention can effectively improve the portability, accuracy and experimental efficiency of Raman spectroscopy detection, is suitable for the needs of crude oil pollution detection in oil extraction and processing, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic diagram of a portable Raman spectroscopy measuring device for detecting heavy metal ions in petroleum.

[0022] Figure 2Schematic diagram of the laser modulation circuit architecture in the present invention.

[0023] Figure 3 These are substrate images collected at different positions of the sample stage in the present invention.

[0024] Figure 4 It is a clarity evaluation value curve diagram corresponding to different base images in the present invention.

[0025] Figure 5 This is a flowchart of the automatic focusing in the present invention.

[0026] Figure 6 The Raman spectrum signal intensity of the present invention changes with the mercury ion Concentration variation graph.

[0027] Figure 7 The Raman optical disc signal intensity and mercury ion Calibration curve of concentration.

[0028] Figure 8 The Raman spectrum signal intensity of the present invention changes with the lead ion Concentration variation graph.

[0029] Fig. 9 The Raman optical disc signal intensity and lead ion Calibration curve of concentration.

[0030] Among them, 1-laser; 2-collimating lens; 3-imaging lens; 4-focusing objective lens; 5-coupling objective lens; 6-narrow bandpass filter; 7-first dichroic mirror; 8-second dichroic mirror; 9-high-pass filter; 10-fiber spectrometer; 11-CCD camera; 12-autofocus module; 13-microfluidic chip; 14-sample stage; 15-first fiber coupler; 16-optical circulator; 17-fiber Bragg grating; 18-second fiber coupler; 19-piezoelectric driver. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described below in conjunction with specific embodiments: A portable Raman spectroscopy measuring device for detecting heavy metal ions in petroleum, such as Figure 1 As shown, it includes a light source module, a wavelength modulation module, an excitation light path module, a confocal detection module, an imaging module, a data processing module, an image processing module, an autofocus module and a portable housing; The light source module includes a laser 1 and a laser modulation circuit. The laser modulation circuit is used to control the switching operation of the laser and adjust the output power to ensure the stability of the output beam, thereby optimizing the stability and sensitivity of the light source signal to meet the requirements of high-precision Raman spectroscopy analysis; The wavelength modulation module is used to realize accurate modulation of the wavelength of the optical signal, and includes a first fiber coupler 15 and a second fiber coupler 18, an optical circulator 16, a fiber Bragg grating 17 and a piezoelectric driver 19, wherein the fiber Bragg grating 17 is connected to the piezoelectric driver 19 through a clamp; The excitation optical path module is used to ensure that the laser is accurately focused on the target area of ​​the microfluidic chip, and includes a collimating lens 2, a narrow bandpass filter 6, a first dichroic mirror 7, a focusing objective lens 4, a microfluidic chip 13 and a sample stage 14, and the microfluidic chip 13 is arranged on the sample stage 14; The confocal detection module is used to collect and detect the Raman scattered light generated by the petroleum sample, and includes a second dichroic mirror 8, a high-pass filter 9, a coupling objective lens 5 and a fiber optic spectrometer 10; The imaging module is used to collect images of the microfluidic chip substrate in real time, and includes an imaging lens 3 and a CCD camera 11; The data processing module is used to process and analyze the collected Raman spectrum data; The image processing module is used to process the collected image of the microfluidic chip substrate to obtain an image clarity evaluation value; The auto-focus module 12 is used to analyze the clarity evaluation value of the image and drive the sample stage 14 to move so as to adjust the focus position of the sample; The portable housing is used to house the modules and has battery power supply function.

[0032] The laser modulation circuit is connected to the laser 1, the laser 1 is connected to the first port of the optical circulator 16 through the first fiber coupler 15, the second port of the optical circulator 16 is connected to the second fiber coupler 18 and the fiber Bragg grating 17 in sequence, and the laser output from the third port of the optical circulator 16 enters the optical path structure, which includes an excitation optical path, a signal collection optical path and an imaging optical path. The excitation optical path includes a collimating lens 2, a narrow bandpass filter 6, a first dichroic mirror 7 and a focusing objective lens 4 in sequence, and the signal collection optical path includes a focusing objective lens in sequence. 4, a first dichroic mirror 7, a second dichroic mirror 8, a high-pass filter 9 and a coupling objective lens 5, and the imaging optical path includes the focusing objective lens 4, the first dichroic mirror 7, the second dichroic mirror 8 and the imaging lens 3 in sequence; the laser is focused to the microfluidic chip 13 through the laser optical path, and the generated Raman scattered light enters the fiber optic spectrometer 10 through the signal collection optical path, and the fiber optic spectrometer is connected to the data processing module, and the other path is focused to the CCD camera 11 through the imaging optical path, and the CCD camera 11 is connected to the image processing module and the autofocus module 12 in sequence.

[0033] The working process of the device is as follows: through the laser modulation circuit, the laser 1 is turned on and the laser output power is controlled to emit a laser light source, the laser light source is coupled to the first port of the three-way optical circulator through the first fiber coupler 15, and the optical circulator sends the light beam to the fiber Bragg grating 17 through the second port; The piezoelectric driver 19 applies different stresses to the fiber Bragg grating 17 to modulate the laser wavelength. A part of the spectrum of the light beam is coupled to the optical path in the form of a single-mode fiber through the second fiber coupler 18, reflected back to the optical circulator, and output from the third port. Another part of the spectrum exits the optical path through the fiber Bragg grating 17. The laser light source output from the third port of the optical circulator is collimated by a collimating lens 2, and the collimated laser beam is filtered by a narrow bandpass filter 6 to filter out unnecessary spectral components and only allow excitation light of a specific wavelength to pass through; the excitation light is reflected by a first dichroic mirror 7 and focused by a focusing objective lens 4 onto a sample on a microfluidic chip 13, exciting the sample to generate Raman scattered light, and the scattered light contains spectral information of the sample, i.e., characteristic information; The Raman scattered light is collected by the focusing lens 4 and then divided into two paths, one of which is filtered by the first and second dichroic mirrors and the high-pass filter 9, and then coupled to the single-mode optical fiber through the coupling lens 5, and finally detected by the optical fiber spectrometer 10 to generate a Raman spectrum signal; The other path is reflected by the first and second dichroic mirrors and focused to the photosensitive element of the CCD camera 11 through the imaging lens 3 to generate a microfluidic chip substrate image; the image processing module calculates the image clarity evaluation value according to the image clarity evaluation algorithm and feeds the result back to the autofocus module 12; the autofocus module 12 adjusts the position of the sample stage according to the feedback signal to ensure that the sample is always in the best focus state. The substrate images collected at different positions of the sample stage are shown in FIG. Figure 3 As shown in the figure, the clarity evaluation values ​​corresponding to different base images are calculated as follows Figure 4 As shown; The data processing module preprocesses the Raman spectral signals collected by multi-wavelength excitation light. The preprocessing includes filtering, denoising and baseline correction, and then performs differential and spectral restoration processing to obtain Raman spectral signals with high signal-to-noise ratio. Finally, the Raman spectral signals are analyzed.

[0034] In this embodiment, the laser uses a 785 nm Raman-specific laser, which has an extremely narrow line width, which can effectively improve the purity of the excitation light, thereby improving the signal-to-noise ratio and intensity of the Raman scattering signal. The narrow line width laser can significantly reduce the background noise when exciting Raman scattering, improve the excitation efficiency of the sample molecular vibration mode, and thus ensure clear and reliable Raman signal detection. The laser not only provides high-quality excitation light, but also has functions such as switch control, power regulation, thermal protection, monitoring, and power feedback to ensure the stability of the laser output, thereby improving the accuracy and repeatability of Raman spectroscopy detection.

[0035] The fiber Bragg grating is embedded in the fixture, and the fixture is connected to the piezoelectric driver. The piezoelectric driver controls the deformation of the fixture through electrical signals, thereby changing the strain of the fiber Bragg grating.

[0036] The laser modulation circuit includes a microcontroller, a switch control unit, a signal feedback unit, and a power regulation unit; The switch control unit uses a field effect tube circuit to achieve fast switching operation of the laser at high frequency and high current under a relatively small control voltage; The signal feedback unit monitors the laser operating current and operating temperature in real time through a photodiode and a thermistor. Figure 2 As shown, to prevent the laser from being damaged due to over-power or overheating, the image processing module monitors the over-exposure of the collected image in real time. When the image is over-exposed, it is determined that the power is too large. If it is not over-exposed, it is determined that the power is normal. The power regulation unit analyzes the feedback signal and integrates the temperature control module and the current control module to realize the temperature control and output power regulation of the laser component.

[0037] Fiber Bragg grating (FBG) is used to modulate the laser wavelength. The central wavelength of the fiber Bragg grating is 785nm. By controlling the structural parameters of the fiber Bragg grating (such as grating period, refractive index distribution, etc.), the laser wavelength is adjusted to ensure that the laser output has a high degree of stability and precise wavelength. When the piezoelectric driver does not apply stress to the fiber Bragg grating, the wavelength expression is: (1); in, is the Bragg wavelength, is the refractive index of the optical fiber, is the period of the fiber Bragg grating. By adjusting the period and refractive index of the fiber Bragg grating, the laser wavelength can be precisely adjusted to meet the needs of Raman spectroscopy analysis.

[0038] When a piezoelectric actuator applies stress to a fiber Bragg grating, the wavelength changes by The expression is: (2); in, is the sensitivity coefficient of refractive index to strain, that is, photo-elastic coefficient, It's strain. is the thermal expansion coefficient of the silica fiber, is the refractive sensitivity index to temperature, namely the thermo-optic coefficient. is the temperature change. Strain sensitivity and temperature sensitivity are usually in the range of a few picometers / and a few picometers / °C; to minimize thermal effects in the current design, the fiber Bragg grating is bonded to the piezoelectric actuator with an epoxy resin with a low coefficient of thermal expansion (CTE) and low thermal conductivity. In addition, the piezoelectric actuation time and measurement time are very short, thus limiting the heat generated by the unit.

[0039] The first and second dichroic mirrors are used to separate the excitation light from the Raman scattering spectrum signal. The first dichroic mirror reflects the excitation light and transmits the Raman scattered light, while the second dichroic mirror transmits the Raman scattered light and reflects the Rayleigh scattered light and other stray light, ensuring that only the Raman scattered light enters the CCD camera for detection. The collimating lens 2 and the focusing objective lens 4 are both high-precision optical components that can achieve efficient transmission of the laser beam and the Raman scattering signal, ensuring that the detection system has high resolution and high signal-to-noise ratio.

[0040] The image processing module performs clarity analysis on the captured image according to the image clarity evaluation algorithm and calculates the clarity evaluation value E; the evaluation value is quantitatively analyzed by the image clarity evaluation algorithm to provide accurate image focus optimization feedback.

[0041] The autofocus module uses a focusing algorithm to accurately adjust the position of the sample stage. The microcontroller system drives the stepper motor to control the movement of the sample stage to ensure that it is always in the best focus state. The focusing algorithm is an improved hill climbing search algorithm, such as Figure 5 As shown, this is achieved through the following steps: Step 1: Set the initial focus position to a preset sample height; Step 2: Capture an image at the initial focus position and calculate the clarity evaluation value; Step 3: The sample stage moves with the initial step distance d. If the clarity evaluation value increases, it continues to move forward; if the clarity evaluation value decreases, it is determined that the focus position is crossed and returns to the previous step position with the original step distance. In this embodiment, the initial step distance d is 10 μm. Step 4: Reduce the step length to 0.9d, and the sample stage moves forward at the new step length; Step 5: Repeat steps 3 and 4 until the sample stage moves less than the set step threshold, and the image is judged to be in the best clarity state, the sample has reached the focal position, and accurate focusing is completed. In this embodiment, the step threshold is set to 0.5 μm.

[0042] The data processing module includes a preprocessing submodule, a difference and restoration processing submodule, and an analysis submodule; The preprocessing submodule is used to filter, denoise and baseline correct the Raman spectrum signal; noise filtering uses filtering algorithms, such as wavelet transform or Gaussian filter, to remove background noise and Rayleigh scattering interference in the Raman spectrum; the filtering parameters are adjusted through multiple iterations to ensure the best denoising effect without affecting the peak characteristics of the Raman signal.

[0043] Baseline correction is performed on the Raman spectral data to eliminate baseline offsets caused by instrument drift or slight changes in sample position. Polynomial fitting algorithms or slope optimization methods are used to automatically identify and correct the baseline of the spectrum to ensure the accuracy of the signal peak.

[0044] The differential and restoration processing submodule is used to perform differential and restoration processing on Raman signals at different wavelengths. When the piezoelectric driver applies different stresses to the fiber Bragg grating and modulates two lasers of different wavelengths, specifically: The total spectral signal detected by the fiber optic spectrometer Including Raman spectrum part and fluorescence background part, the expression is: (3); in, and represent the intensity of Raman light and fluorescence background, respectively. For the Bragg wavelength, ; According to Kasha's rule, when the laser wavelength changes slightly, the fluorescence background will not change, while the Raman spectrum will change with a slight change in the central wavelength. The formula is: (4); When the excitation wavelength has a very narrow bandwidth, the Dirac function can be used Indicates that the spectral signal It is expressed as: (5); Then formula (3) is expressed as: (6); Simplified to: (7); in, is the wavelength difference of the two excitation lights; it can be observed that the differential Raman spectral signal is composed of the Raman spectral signal and the two If you want to restore the original Raman spectrum signal from the differential Raman spectrum signal, you need to The function performs deconvolution calculation to achieve this.

[0045] make ,but: (8); Therefore, it is necessary to pass the known and Decoding the target Raman spectrum , according to Fourier transform: (9); make , then: (10); Through the inverse Fourier transform, we get: (11).

[0046] The analysis module is used to analyze the restored original Raman spectral signal, including peak recognition and quantitative analysis, Raman spectrum matching and identification, multi-component analysis, data visualization and report generation.

[0047] Peak recognition and quantitative analysis uses peak recognition algorithms (such as Gaussian fitting, Lorentzian fitting or convolution algorithm) to automatically detect key vibration peaks in Raman spectra, calculate the intensity, position and half-width (FWHM) of the peaks, and quantitatively analyze the concentration or composition of the target substance in the sample by comparing the characteristic peak information in the standard database.

[0048] Raman spectrum matching and identification Based on the known Raman spectrum database, the measured spectrum is compared with the spectrum in the standard spectrum library using a spectrum matching algorithm (such as the least squares method, correlation coefficient analysis or dynamic time warping (DTW) algorithm) to identify the chemical composition and molecular structure of the sample; the chemical composition of the sample can be further confirmed by analyzing the matching degree and spectrum error.

[0049] Multi-component analysis uses multivariate analysis methods, such as principal component analysis (PCA), partial least squares (PLS) or support vector machine (SVM), to perform multi-component analysis of samples. By analyzing the composite response of multiple Raman peaks, the relative concentrations or material distribution of multiple components in the sample can be quantitatively evaluated.

[0050] Data visualization and report generation Generate Raman spectra, concentration distribution diagrams and sample analysis reports based on the real-time analysis results provided above. The report content includes the Raman spectrum data of the sample, target molecule information, analysis conclusions and data processing results, and supports users to save the analysis results in a standard format (such as PDF, CSV or Excel files) for subsequent viewing and archiving.

[0051] The data processing module is also connected to the cloud computing platform or remote server to achieve remote storage, analysis and sharing of spectral data. Users can access the remote server through a dedicated application or Web interface to view analysis results, obtain sample data and conduct further data mining and analysis. This function is particularly suitable for distributed analysis systems, which can achieve data collaborative processing in multiple locations and multiple devices, and improve the application flexibility and efficiency of the system.

[0052] The data processing module further includes a machine learning submodule, which uses deep learning algorithms, such as convolutional neural networks (CNN) or support vector machines (SVM), to train the calibrated Raman spectroscopy data to optimize the accuracy of peak recognition and substance identification. By continuously updating the training data set and optimizing the algorithm model, the machine learning module can gradually improve the accuracy and automation level of sample analysis, and is particularly suitable for Raman spectroscopy analysis of complex samples and multi-component systems.

[0053] The application of the present invention in the detection of heavy metal ions in petroleum demonstrates its excellent on-site detection capability. Through microfluidic chip technology, the device can efficiently process petroleum samples and enrich heavy metal ions (such as mercury, lead, cadmium, etc.) therein. Combined with a 785nm laser light source and displacement excitation Raman differential spectroscopy technology, the device can perform high-sensitivity detection of samples at multiple excitation wavelengths, and improve the signal-to-noise ratio of the Raman signal through differential signal processing technology, ensuring accurate identification of characteristic peaks of heavy metal ions, such as Figure 6 The fiber Bragg grating module further optimizes the laser wavelength to ensure signal stability and excitation efficiency. In the actual detection process, this device can analyze the heavy metal concentration in the petroleum sample in real time, such as Figure 6 and Figure 8 As shown, providing high-precision data, Figure 7 and Fig. 9 The results show an excellent linear correlation, which confirms the excellent qualitative and quantitative detection capabilities of the system. This technology has broad application potential in the fields of oil pollution monitoring, environmental protection, and water quality testing, especially in field detection tasks that require rapid response and high-throughput analysis, showing excellent performance.

[0054] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A portable Raman spectroscopy measuring device for detecting heavy metal ions in petroleum, comprising a light source module, an excitation optical path module, and a confocal detection module, wherein the light source module comprises a laser and a laser modulation circuit, the excitation optical path module comprises a collimating lens, a narrow bandpass filter, a first dichroic mirror, a focusing objective lens, a microfluidic chip, and a sample stage, the microfluidic chip is arranged on the sample stage, and the confocal detection module comprises a second dichroic mirror, a high-pass filter, a coupling objective lens, and a fiber optic spectrometer, characterized in that: It also includes a wavelength modulation module, an imaging module, a data processing module, an image processing module, and an autofocus module; The wavelength modulation module is used to realize wavelength modulation of optical signals, and includes first and second optical fiber couplers, an optical circulator, a fiber Bragg grating and a piezoelectric driver, wherein the fiber Bragg grating is connected to the piezoelectric driver through a clamp; The imaging module is used to collect images of the microfluidic chip substrate in real time, and includes an imaging lens and a CCD camera; The data processing module is used to process and analyze the collected Raman spectrum data; The image processing module is used to process the collected image of the microfluidic chip substrate to obtain an image clarity evaluation value; The autofocus module is used to analyze the clarity evaluation value of the image and drive the sample stage to move to adjust the focus position of the sample; The laser modulation circuit is connected to the laser, the laser is connected to the first port of the optical circulator through the first optical fiber coupler, the second port of the optical circulator is connected to the second optical fiber coupler and the fiber Bragg grating in sequence, the laser output from the third port of the optical circulator enters the optical path structure, the optical path structure includes an excitation optical path, a signal collection optical path and an imaging optical path, the excitation optical path includes a collimating lens, a narrow bandpass filter, a first dichroic mirror and a focusing objective lens in sequence, the signal collection optical path includes a focusing objective lens, a first dichroic mirror, a second dichroic mirror, a high-pass filter and a coupling objective lens in sequence, and the imaging optical path includes a focusing objective lens, a first dichroic mirror, a second dichroic mirror and an imaging lens in sequence; the laser is focused to the microfluidic chip through the laser optical path, the generated Raman scattered light enters the optical fiber spectrometer through the signal collection optical path in one path, the optical fiber spectrometer is connected to the data processing module, and the other path is focused to the CCD camera through the imaging optical path, and the CCD camera is connected to the image processing module and the autofocus module in sequence.

2. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 1, characterized in that: The laser modulation circuit controls the start-up of the laser and the laser output power to emit a laser light source, which is coupled to the first port of the three-way optical circulator through the first optical fiber coupler, and the optical circulator sends the light beam to the fiber Bragg grating through the second port; The piezoelectric driver applies different stresses to the fiber Bragg grating to modulate the laser wavelength. A part of the spectrum of the light beam is coupled to the optical path in the form of a single-mode fiber through the second fiber coupler, reflected back to the optical circulator, and output from the third port, and another part of the spectrum exits the optical path through the fiber Bragg grating. The laser light source output from the third port of the optical circulator is collimated by a collimating lens, the collimated laser beam is filtered by a narrow bandpass filter, and is focused to the sample on the microfluidic chip by a first dichroic mirror and a focusing objective lens, so as to excite the sample to generate Raman scattered light, and the scattered light contains the spectral information of the sample, that is, characteristic information; The Raman scattered light is collected by a focusing objective lens and then divided into two paths, one of which is filtered by the first and second dichroic mirrors and a high-pass filter, and then coupled to a single-mode optical fiber through a coupling objective lens, and finally detected by a fiber optic spectrometer to generate a Raman spectrum signal; The other path is reflected by the first dichroic mirror and the second dichroic mirror, and then focused to the photosensitive element of the CCD camera through the imaging lens to generate an image of the microfluidic chip substrate; the image processing module calculates the image clarity evaluation value according to the image clarity evaluation algorithm, and feeds the result back to the autofocus module; the autofocus module adjusts the position of the sample stage according to the feedback signal to ensure that the sample is always in the best focus state; The data processing module preprocesses the Raman spectral signals collected by multi-wavelength excitation light. The preprocessing includes filtering, denoising and baseline correction, and then performs differential and spectral restoration processing to obtain Raman spectral signals with high signal-to-noise ratio. Finally, the Raman spectral signals are analyzed.

3. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 2, characterized in that: The laser adopts a 785 nm Raman dedicated laser, the fiber Bragg grating is embedded in a fixture, the fixture is connected to a piezoelectric driver, and the piezoelectric driver controls the deformation of the fixture through an electrical signal, thereby changing the strain of the fiber Bragg grating.

4. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 3, characterized in that: The laser modulation circuit includes a microcontroller, a switch control unit, a signal feedback unit, and a power adjustment unit; The switch control unit adopts a field effect tube circuit to achieve fast switching operation of the laser at high frequency and high current under a relatively small control voltage; The signal feedback unit monitors the laser operating current and operating temperature in real time through a photodiode and a thermistor to prevent the laser from being damaged due to overpower or overheating. The image processing module monitors the overexposure of the collected image in real time. The power regulation unit analyzes the feedback signal and integrates the temperature control module and the current control module to realize the temperature control and output power regulation of the laser component.

5. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 4, characterized in that: The central wavelength of the fiber Bragg grating is 785 nm. The laser wavelength is adjusted by controlling the structural parameters of the fiber Bragg grating. When the piezoelectric driver does not apply stress to the fiber Bragg grating, the wavelength expression is: (1)； in, is the Bragg wavelength, is the refractive index of the optical fiber, is the period of the fiber Bragg grating; When a piezoelectric actuator applies stress to a fiber Bragg grating, the wavelength changes by The expression is: (2)； in, is the sensitivity coefficient of refractive index to strain, It's strain. is the thermal expansion coefficient of the silica fiber, is the refractive sensitivity index to temperature, is the amount of temperature change; to minimize thermal effects in the current design, the fiber Bragg grating is bonded to the piezoelectric actuator with an epoxy resin with a low thermal expansion coefficient and low thermal conductivity. In addition, the piezoelectric actuation time and measurement time are very short, thus limiting the heat generated by the unit.

6. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 5, characterized in that: The first dichroic mirror reflects the excitation light and transmits the Raman scattered light, and the second dichroic mirror transmits the Raman scattered light and reflects the Rayleigh scattered light and other stray light, ensuring that only the Raman scattered light enters the CCD camera for detection.

7. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 6, characterized in that: The image processing module performs clarity analysis on the collected image according to the image clarity evaluation algorithm and calculates the clarity evaluation value E; The autofocus module uses a focusing algorithm to accurately adjust the position of the sample stage to ensure that it is always in the best focus state. The focusing algorithm is an improved hill climbing search algorithm, which is implemented by the following steps: Step 1: Set the initial focus position to a preset sample height; Step 2: Capture an image at the initial focus position and calculate the clarity evaluation value; Step 3: The sample stage moves with the initially set step length d. If the clarity evaluation value increases, it continues to move forward; if the clarity evaluation value decreases, it is determined to have passed the focus position and returns to the previous step position with the original step length; Step 4: Reduce the step length to 0.9d, and the sample stage moves forward at the new step length; Step 5: Repeat steps 3 and 4 until the sample stage movement step is less than the set step threshold, and the image is judged to be in the best clarity state, the sample has reached the focal position, and precise focusing is completed.

8. A portable Raman spectroscopic measuring device for detecting heavy metal ions in petroleum according to claim 7, characterized in that: In the data processing module, when the piezoelectric driver applies different stresses to the fiber Bragg grating and modulates two lasers with different wavelengths, the differential and spectrum restoration processing is specifically as follows: The total spectral signal detected by the fiber optic spectrometer Including Raman spectrum part and fluorescence background part, the expression is: (3)； in, and represent the intensity of Raman light and fluorescence background, respectively. For the Bragg wavelength, ; Differential Raman spectroscopy The formula is: (4)； When the excitation wavelength has an extremely narrow bandwidth, the Dirac function Indicates that the spectral signal It is expressed as: (5)； Then formula (3) is expressed as: (6)； Simplified to: (7)； in, is the difference in wavelength of the two excitation lights; make ,but: (8)； According to Fourier transform, we get: (9)； make , then: (10)； Through the inverse Fourier transform, we get: (11)。

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