Double-optical-path spectrum system for turbidity measurement and interference compensation

Abstract

The invention discloses a double-optical-path spectrum system for turbidity measurement and interference compensation, which comprises a double-optical-path spectrum measurement system, and the double-optical-path spectrum measurement system comprises a light source, and an optical path collimation and switching system, a double-optical-path measurement system, a transmission measurement system and a scattering measurement system which are electrically connected, the particle size distribution and extinction spectrum of the water body are reconstructed by combining a spectral analysis algorithm, and turbidity measurement and interference compensation are carried out on the water body. Sampling is carried out by adopting a dual-optical-path technology; scattering signals of a water body to-be-measured sample are measured by combining sampling data with an integrating sphere so as to verify the influence of the scattering signals, particle size distribution of water body particles is reconstructed by utilizing a light total scattering method, and a particle reconstruction wave band is determined by adopting a mode of reconstructing a comparison standard solution in multiple wave bands; secondary inversion of an extinction spectrum is carried out according to a reconstruction result, accumulation correction is carried out by using multiple groups of compensation results of different filter membranes of adjacent gradients, and the accuracy of a later turbidity compensation result is improved.

Description

Technical Field

[0001] The invention relates to a dual-light-path spectrum system, in particular to a dual-light-path spectrum system for turbidity measurement and interference compensation. Background Art

[0002] There are many detection methods for water environment safety. Among them, the UV-visible spectroscopy water quality detection method based on the Lambert-Beer law has the characteristics of no secondary pollution, fast detection speed and low cost. This method uses transmission measurement to evaluate water pollutants, especially the content of soluble organic pollutants, based on the absorbance of water samples at specific light wavelengths. Its solution methods can be divided into three categories: single wavelength method, multi-wavelength method and UV-visible continuous spectroscopy method.

[0003] Although the data processing of UV-visible continuous spectroscopy is difficult, it has high measurement accuracy and good adaptability to different application scenarios, and has become a research hotspot in recent years. There are a large number of solid suspended particles in natural water bodies. The light scattering caused by them during transmission measurement will destroy the applicable conditions of the Lambert-Beer law and seriously affect the detection accuracy of UV-visible spectroscopy. This phenomenon is called turbidity interference.

[0004] When using single-wavelength or multi-wavelength spectroscopy to detect water quality, the absorbance at 350nm is mostly selected as the turbidity correction factor for proportional compensation. However, since turbidity interference presents nonlinear characteristics at different wavelengths, this method has low compensation accuracy and is not suitable for continuous spectra.

[0005] Machine learning water quality detection algorithms represented by neural networks and compensation algorithms based on multivariate scattering calibration models have a certain inhibitory effect on turbidity interference in continuous spectroscopy water quality analysis, but they both require a large amount of prior data support, are unable to adapt to rapid changes in particle concentration, and have unstable compensation effects, making it difficult to achieve ideal results in practical applications.

[0006] The traditional UV-visible spectral turbidity interference compensation algorithm based on Mie scattering theory quantitatively analyzes the influence of particles on the absorption spectrum, reconstructs the particle size distribution of suspended particles contained in the sample by analyzing the total light scattering method, and further inverts its extinction spectrum to correct the interference effect. However, the reconstruction of particle size distribution has certain errors. Summary of the invention

[0007] The invention provides a dual-light-path spectrum system for turbidity measurement and interference compensation, so as to overcome the defect that the measurement light path and the reference light path of water quality online detection in the prior art have poor consistency in the light source and the detector.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] The invention discloses a dual-light path spectrum system for turbidity measurement and interference compensation, comprising a dual-light path spectrum measurement system, wherein the dual-light path spectrum measurement system comprises a light source and an optical path collimation and switching system electrically connected, a dual-light path measurement system, a transmission measurement system and a scattering measurement system; the dual-light path measurement system comprises a measurement light path and a reference light path, wherein the measurement light path comprises a water body to be measured, an automatic membrane changer A, a sampling tube for storing the water body to be measured, a filter membrane A for filtering the water body to be measured and a pump A, and the reference light path comprises a standard solution, an automatic membrane changer B, a filter membrane B for filtering the standard solution and a pump B, and is used to ensure the consistency of the measurement light path and the reference light path on the light source and the detector.

[0010] Furthermore, the optical path collimation and switching system includes a "Y"-shaped incident optical fiber, a collimating lens connected to one end thereof, and a mechanical optical switch.

[0011] Furthermore, the mechanical optical switch includes a light shield and a stepping motor for controlling the light shield to switch the optical path.

[0012] Furthermore, the transmission measurement system includes a total reflection prism, a focusing lens located on one side of the total reflection prism, a "Y"-shaped incident optical fiber located at the front end of the light source, and a spectrometer located behind the focusing lens.

[0013] Furthermore, the middle sections of the measurement optical path and the reference optical path are designed with an integrating sphere, which is used to measure the light scattering interference of particles in the water while the system measures the absorption, and verify the secondary inversion result of the later extinction spectrum.

[0014] Furthermore, the scattering measurement system includes an integrating sphere, a focusing lens, a "Y"-shaped output optical fiber located behind the focusing lens, a scattering detector located on the other side of the total reflection prism, and a spectrometer.

[0015] Furthermore, the incident light is split by the "Y"-shaped incident optical fiber and collimated into two beams of parallel light by a collimating lens. The two beams of parallel light pass through the measurement light path and the reference light path of the open colorimetric cell respectively.

[0016] Furthermore, the total reflection prism is used to turn the transmitted light by 180°, couple it into the output optical fiber through the focusing lens, and collect it into the spectrometer for analysis through the output optical fiber.

[0017] The beneficial effects achieved by the present invention are: the dual optical path technology is adopted to ensure the consistency of the measurement optical path and the reference optical path on the light source and the scattering detector. The scattering signal of the water sample to be tested can be measured in combination with the integrating sphere, and the transmitted absorption signal and the extinction signal obtained in the system algorithm can be compared to verify the influence of the scattering signal. The total light scattering method is used to reconstruct the particle size distribution of the water body, and the multi-band reconstruction comparison standard solution method is used to determine the most suitable reconstruction band under different particle sizes and different parameters, so as to improve the accuracy of the later turbidity compensation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 It is a schematic diagram of the structure of the present invention;

[0020] Figure 2 It is a structural schematic diagram of the automatic membrane changer of the present invention;

[0021] Figure 3 It is the system operation diagram of the present invention.

[0022] In the figure: 1. water body to be tested; 2. standard solution; 3. sampling tube; 4. filter membrane A; 5. filter membrane B; 6. light source; 7. incident optical fiber; 8. stepping motor; 9. collimating lens; 10. light shield; 11. measuring optical path; 12. reference optical path; 13. spectrometer; 14. focusing lens; 15. total reflection prism; 16. pump A; 17. pump B; 18. output optical fiber; 19. scattering detector; 20. automatic membrane changer A; 21. automatic membrane changer B; 22. circulation system. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0024] Example 1

[0025] like Figure 1-3 As shown, a dual-path spectral system for turbidity measurement and interference compensation includes a dual-path spectral measurement system, which includes a light source 6 and an optical path collimation and switching system, a dual-path measurement system, a transmission measurement system and a scattering measurement system connected electrically.

[0026] The optical path collimation and switching system includes a "Y"-shaped incident optical fiber 7, a collimating lens 9 connected to one end thereof, and a mechanical optical switch; the mechanical optical switch includes a light blocking plate 10 and a stepping motor 8 for controlling the light blocking plate 10 to realize optical path switching.

[0027] The dual optical path measurement system includes a measuring optical path 11 and a reference optical path 12. The measuring optical path 11 includes a water body 1 to be measured, a sampling tube 3 for storing the water body 1 to be measured, an automatic membrane changer A20, a filter membrane A4 for filtering the water body 1 to be measured, and a pump A16; the reference optical path 12 includes a standard solution 2, an automatic membrane changer B21, a filter membrane B5 for filtering the standard solution 2, and a pump B17, which are used to ensure the consistency of the measuring optical path 11 and the reference optical path 12 on the light source 6 and the scattering detector 19.

[0028] The transmission measurement system includes a total reflection prism 15 , a focusing lens 14 located at one side of the total reflection prism 15 , a “Y”-shaped incident optical fiber 7 located at the front end of the light source 6 , and a spectrometer 13 located behind the focusing lens 14 .

[0029] The scattering measurement system includes an integrating sphere, a focusing lens 14 , a “Y”-shaped output optical fiber 18 located behind the focusing lens 14 , a scattering detector 19 located on the other side of the total reflection prism 15 , and a spectrometer 13 .

[0030] The xenon lamp emits ultraviolet-visible light with a wavelength of 250 to 1000 nm to the incident optical fiber 7. The incident light is split by the "Y"-shaped incident optical fiber 7, and then collimated by the collimating lens 9 into two parallel beams. The two parallel beams pass through the reference optical path 12 and the measuring optical path 11 using an open colorimetric cell respectively. After the light beam is absorbed by the solution, it is turned 180 degrees by the total reflection prism 15, and then coupled into the output optical fiber 18 through the focusing lens 14. The transmitted light is collected by the output optical fiber 18 and is analyzed in the spectrometer 13. According to the detection principle of the dual-path spectrum probe, the absorption characteristics of the measured solution can be calculated.

[0031] An integrating sphere is designed in the middle of the measuring optical path 11 and the reference optical path 12. The integrating sphere enables the system to measure the light scattering interference of particles in the water while measuring absorption, and verify the secondary inversion results of the later extinction spectrum.

[0032] Operation process: including the measurement of the reference optical path 12 and the measurement of the water body 1 to be measured. The reference optical path 12 is mainly used to configure water bodies with different particle sizes or more adjustable parameters, such as temperature, pH and other parameters, align them for spectral sampling, and then reconstruct the particle size distribution of the system in combination with the total reflection method, and perform a secondary inversion calculator extinction spectrum.

[0033] Different from the traditional method, the inversion band in the present invention is measured by adjusting multiple parameters, fully considering the factors that may affect the particle size reconstruction under different particle sizes and water environment, and calculating to obtain the best reconstructed spectral band range suitable for the corresponding particle size distribution and water parameters, thereby obtaining more accurate extinction spectrum and turbidity compensation.

[0034] After sampling the water body to be tested, switching measurements are performed using filter membranes of different pore sizes to obtain water spectral data under adjacent filter membrane sizes. Combined with the turbidity compensation of different environments obtained by the reference pool, the overall turbidity compensation result can be calculated more accurately, thereby improving the calculation results of water quality parameters such as the chemical oxygen content of the water body.

[0035] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the above embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the above embodiments, or to replace some of the technical features therein by equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. The terms used in the description of this application are only for describing specific implementations, and are not intended to limit the exemplary implementations according to the present application. For ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The techniques, methods and devices known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the techniques, methods and devices should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0037] It should be noted that, in the description of the present application, the orientation or positional relationship indicated by terms such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise stated, these orientation words do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application; the orientation words "inside and outside" refer to the inside and outside relative to the contour of each component itself.

Claims

1. A dual-path spectral system for turbidity measurement and interference compensation, characterized in that: The invention comprises a dual-light path spectrum measurement system, which comprises a light source and an optical path collimation and switching system, a dual-light path measurement system, a transmission measurement system and a scattering measurement system connected electrically; a spectrum analysis algorithm is combined to reconstruct the particle size distribution and extinction spectrum of the water body, and turbidity measurement and interference compensation are performed on the water body. The dual-optical path measurement system includes a measuring optical path and a reference optical path. The measuring optical path includes a water body to be measured, a sampling tube for storing the water body to be measured, an automatic membrane changer A, a filter membrane A for filtering the water body to be measured, and a pump A. The reference optical path includes a standard solution, an automatic membrane changer B, a filter membrane B for filtering the standard solution, a pump B, and a circulation system. The same optical path and synchronous sampling are used to ensure the consistency of the measuring optical path and the reference optical path on the light source and the scattering detector. In the spectral analysis algorithm, the total light scattering method is used to reconstruct the particle size distribution of water particles in multiple bands, the extinction spectrum is secondary inverted based on the optimal reconstruction result, the extinction result is verified and turbidity compensation is performed in combination with the original spectrum and scattering measurement results, and multiple groups of compensation results of adjacent aperture gradient filters are used for cumulative correction to improve the accuracy of the later turbidity compensation results.

2. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 1, characterized in that: The optical path collimation and switching system comprises a "Y"-shaped incident optical fiber with equal power output, a collimating lens connected to one end thereof, and a mechanical optical switch.

3. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 2, characterized in that: The mechanical optical switch comprises a light blocking plate and a stepping motor for controlling the light blocking plate to realize optical path switching.

4. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 1, characterized in that: The transmission measurement system includes a total reflection prism, a focusing lens located at one side of the total reflection prism, a "Y"-shaped incident optical fiber located at the front end of a light source, and a dual-channel spectrometer located behind the focusing lens.

5. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 4, characterized in that: The middle sections of the measuring optical path and the reference optical path are combined with an integrating sphere, which is used to measure the light scattering interference of particles in the water body while the system measures the absorption, so as to verify the secondary inversion result of the later extinction spectrum.

6. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 5, characterized in that: The scattering measurement system includes an integrating sphere, a focusing lens, a "Y"-shaped output optical fiber located behind the focusing lens, a scattering detector located on the other side of a total reflection prism, and a spectrometer.

7. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 2, characterized in that: The incident light is split by the "Y"-shaped incident optical fiber and collimated into two beams of parallel light by a collimating lens. The two beams of parallel light pass through the measurement light path and the reference light path of the open colorimetric cell respectively.

8. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 6, characterized in that: The total reflection prism is used to turn the transmitted light 180 degrees, couple it into the output optical fiber through the focusing lens, collect it into the spectrometer through the output optical fiber, and then send it to the computer for spectral analysis.

9. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 1, characterized in that: The total light scattering method is used to perform spectral analysis in multiple bands to reconstruct the particle size distribution of water particles. The multi-band reconstruction is compared with the standard solution to determine the most appropriate particle size distribution reconstruction band under different particle sizes and different parameters.

10. The dual-light-path spectral system for turbidity measurement and interference compensation according to claim 1, characterized in that: Combined with the optimal reconstruction band result of claim 9, the extinction spectrum is inverted for the second time, and the extinction spectrum and turbidity compensation are obtained by comparing the original spectrum and the scattering measurement results. Multiple groups of compensation results of adjacent aperture gradient filters are used for cumulative correction to improve the accuracy of the later turbidity compensation results.

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