A method and system for cross-instrument Raman shift calibration of Raman spectrometers

Abstract

This invention relates to the field of Raman spectroscopy detection, and particularly to a cross-instrument Raman shift calibration method and system for Raman spectrometers. The calibration method includes identifying a master instrument and at least one slave instrument; performing Raman spectroscopy detection on a standard sample using both the master and slave instruments to obtain spectral data; processing the spectral data to obtain peak position information, including the abscissa value of each characteristic peak on the spectrum; calculating the peak position deviation between the master and slave instrument spectral data based on the peak position information; and fitting and correcting the deviation to obtain the Raman shift calibration parameters of the slave instrument relative to the master instrument. Through the above calculation and processing of peak position information, Raman spectra between different instruments can be standardized and corrected, thereby effectively reducing the irregular Raman shift drift caused by instrument performance and monitoring environment. It is simple and easy to operate, has good versatility, and requires no manual parameter adjustment.

Description

Technical Field

[0001] This invention relates to the field of Raman spectroscopy detection, and in particular to a cross-instrument Raman shift calibration method and system for Raman spectrometers. Background Technology

[0002] Raman spectroscopy is a non-contact spectroscopic analysis technique based on the Raman scattering effect. It reflects the molecular fingerprint spectrum based on the vibrations of chemical bonds in a substance, enabling qualitative and quantitative analysis of the substance's composition. Therefore, it has been widely applied in fields such as liquid security inspection, jewelry testing, explosives detection, drug detection, and pharmaceutical testing.

[0003] With the development of technology, various types of Raman spectrometers have emerged (such as large scientific research spectrometers, portable spectrometers, handheld spectrometers, etc.). However, in the demand for material detection using multiple instruments, the spectra measured by different Raman spectrometers for the same sample can vary due to differences in instrument performance and detection environment, which in turn affects subsequent detection results and applications.

[0004] Currently, methods to eliminate the influence of cross-instrumental factors on the abscissa of Raman spectra include bias-based polynomial function fitting, moving-window fast Fourier transform cross-correlation, and dynamic time warping. However, while directly using polynomial fitting for spectrum calibration is simple, it only yields a calibration parameter with a small overall bias, and irregular fluctuations still exist after calibration. Moving-window fast Fourier transform cross-correlation can correct the spectrum, but this method requires user-defined window size settings, necessitating manual operation. Furthermore, inappropriate window selection may cause Raman peak distortion, which is detrimental to the standardization of other spectra. Dynamic time warping, which stretches and moves the spectrum, suffers from limitations in unidirectional movement and susceptibility to standard peak information, potentially leading to uneven distribution of corrected spectral data points. Summary of the Invention

[0005] To address at least one deficiency in the existing cross-instrument Raman shift calibration methods, this invention provides a cross-instrument Raman shift calibration method for Raman spectrometers, comprising at least the following steps:

[0006] A master instrument and at least one slave instrument are identified; and the master instrument and the slave instrument are used to perform Raman spectroscopy detection on the standard sample to obtain the spectral data of the master instrument and the spectral data of the slave instrument, respectively.

[0007] The spectral data of the master instrument and the spectral data of the slave instrument are analyzed and processed to obtain several first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the abscissa value of each characteristic peak on the spectrum;

[0008] Based on the first characteristic peak position information and the second characteristic peak position information, the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument is calculated; several deviation values ​​are corrected to obtain the Raman shift calibration parameter of the slave instrument relative to the master instrument.

[0009] In one embodiment, the method for analyzing and processing the spectral data of the master instrument and the spectral data of the slave instrument includes at least one data processing method selected from Gaussian fitting, Lorentz fitting, and maximum value method to determine the Raman peak position information.

[0010] In one embodiment, the formula for calculating the deviation of the characteristic peak positions between the spectral data of the master instrument and the spectral data of the slave instrument is as follows:

[0011]

[0012] in, This represents the abscissa value of the i-th characteristic peak in the spectrum of the main instrument; This represents the abscissa value of the i-th characteristic peak in the spectrum of the instrument.

[0013] In one embodiment, correcting the plurality of said deviation values ​​includes the steps of:

[0014] In the numerical region between the first and last deviation values, all Raman shift calibration parameters between the first and last characteristic peaks in the spectrum are obtained by correcting all adjacent deviation values ​​using one or more methods such as arithmetic series fitting, polynomial fitting, or piecewise fitting.

[0015] In the numerical region outside the first and last deviation values, the first deviation value is used as the Raman shift calibration parameter before the first characteristic peak in the spectrum, and the last deviation value is used as the Raman shift calibration parameter after the last characteristic peak in the spectrum.

[0016] In one embodiment, the method further includes the steps of: plotting the Raman shift calibration parameters into a continuous calibration curve; using the same slave instrument to detect the sample to obtain the sample spectrum; and then transferring the calibration curve to the sample spectrum to obtain the abscissa calibration result of the slave instrument relative to the master instrument.

[0017] In one embodiment, the standard sample and the sample to be tested have the same range of distribution regions of the characteristic peaks.

[0018] The present invention also provides a cross-instrument Raman shift calibration system for Raman spectrometers, comprising:

[0019] The spectral detection module, based on a determined master instrument and at least one slave instrument, is used to perform Raman spectral detection on a standard sample using the master instrument and the slave instrument respectively, so as to obtain the spectral data of the master instrument and the spectral data of the slave instrument.

[0020] The spectral analysis module analyzes and processes the spectral data of the master instrument and the slave instrument respectively to obtain several first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the abscissa value of each characteristic peak on the spectrum;

[0021] The peak position calibration module calculates the deviation values ​​of the characteristic peak positions of the master instrument's spectral data and the slave instrument's spectral data based on the first characteristic peak position information and the second characteristic peak position information; and corrects several of the deviation values ​​to obtain the Raman shift calibration parameters of the slave instrument relative to the master instrument.

[0022] Based on the above, compared with the prior art, the cross-instrument Raman shift calibration method for Raman spectrometers provided by this invention can standardize the Raman spectra of different instruments by calculating and processing peak position information, thereby effectively reducing the irregular Raman shift drift caused by instrument performance and monitoring environment. It is simple and easy to operate, has good versatility, and requires no manual parameter adjustment.

[0023] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other beneficial effects of the invention can be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Unless otherwise specified, the positional relationships shown in the drawings in the following description are based on the direction in which the components are drawn in the figure.

[0025] Figure 1 A flowchart of a cross-instrument Raman shift calibration method for Raman spectrometers provided in an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of arithmetic sequence fitting correction for deviation values;

[0027] Figure 3 A flowchart of a cross-instrument Raman shift calibration method for Raman spectrometers provided in another embodiment of the present invention;

[0028] Figure 4 A line graph showing the deviation of the Raman characteristic peak positions measured by the two instruments;

[0029] Figure 5 Schematic diagrams of the spectrum curves of the main instrument and the slave instrument before and after calibration.

[0030] Figure 6 for Figure 5 Line graph showing the deviation values ​​of the corresponding characteristic peaks before and after correction;

[0031] Figure 7 This is a structural block diagram of a cross-instrument Raman shift calibration system for Raman spectrometers provided in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0034] Please see Figure 1Based on the differences in Raman peak positions detected by instruments and the principle that the wavelength is spatially continuous after spectral dispersion in a dispersive Raman spectrometer, this invention provides a cross-instrument Raman shift calibration method for Raman spectrometers, comprising the following steps:

[0035] S10, determine one master instrument and at least one slave instrument; and use the master instrument and the slave instrument to perform Raman spectroscopy detection on the standard sample respectively to obtain the spectral data of the master instrument and the spectral data of the slave instrument.

[0036] Specifically, appropriate master and slave instruments can be selected based on the actual needs of the sample to be tested. For example, a high-precision and high-performance instrument can be selected as the master instrument from different Raman spectrometers, with the others serving as slave instruments. Preferably, the standard sample should have the same range of characteristic peak distribution regions as the sample to be tested. That is, the standard sample can be selected based on the properties of the sample to be tested, and should contain abundant Raman characteristic peaks and strong Raman scattering signals within the Raman spectral range required for calibration. The standard sample can be a single substance, such as acetaminophen, or a mixture of multiple substances, such as a mixture of carbon tetrachloride, acetonitrile, and phenylacetylene; no limitation is made here.

[0037] Furthermore, to ensure the relative stability of the influence between instruments in the same batch of spectral data, this embodiment can obtain spectral data by performing multiple tests on the standard sample under the same detection conditions using the master and slave instruments, thereby effectively improving the accuracy of the subsequently obtained Raman shift calibration parameters.

[0038] S20, the spectral data of the master instrument and the spectral data of the slave instrument are analyzed and processed respectively to obtain a number of first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the horizontal coordinate value of each characteristic peak on the spectrum.

[0039] Specifically, the methods for analyzing and processing the spectral data of the master instrument and the slave instrument include data processing methods such as Gaussian fitting, Lorentz fitting, and maximum value method to determine the Raman peak position information.

[0040] Taking Gaussian fitting as an example, the collected spectral data can be fitted and optimized using Gaussian function and nonlinear least squares optimization LM algorithm, thereby obtaining several characteristic peaks and information such as peak height, peak width and peak position of each characteristic peak from the spectral data.

[0041] It should be noted that, according to the concept of the present invention, those skilled in the art can also use other peak-finding algorithms or data processing methods that can obtain the horizontal coordinate values ​​of each characteristic peak in the spectral data on the spectral graph to analyze and process the spectral data. This embodiment is not limited to the above methods.

[0042] S30, calculate the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument based on the first characteristic peak position information and the second characteristic peak position information; correct several of the deviation values ​​to obtain the Raman shift calibration parameter of the slave instrument relative to the master instrument.

[0043] Specifically, the formula for calculating the deviation between the characteristic peak positions of the spectral data from the master instrument and the spectral data from the slave instrument is as follows:

[0044]

[0045] in, This represents the abscissa value of the i-th characteristic peak in the spectrum of the main instrument; This represents the abscissa value of the i-th characteristic peak in the spectrum of the instrument.

[0046] By calculating the difference in the position information of each set of characteristic peaks, we can obtain the deviation between the master instrument and the slave instrument caused by the instrument itself and various detection environments. Then, we can fit and correct the deviation.

[0047] The correction of several of the aforementioned deviation values ​​includes the following steps:

[0048] In the numerical region between the first and last deviation values, all Raman shift calibration parameters between the first and last characteristic peaks in the spectrum are obtained by correcting all adjacent deviation values ​​using one or more methods such as arithmetic series fitting, polynomial fitting, or piecewise fitting.

[0049] In the numerical region outside the first and last deviation values, the first deviation value is used as the Raman shift calibration parameter before the first characteristic peak in the spectrum, and the last deviation value is used as the Raman shift calibration parameter after the last characteristic peak in the spectrum.

[0050] For example, please see Figure 2 At the offset value Δp i and adjacent offset value Δp i+1 The x-axis can be divided into n segments, and then an arithmetic sequence can be used to calculate Δp. i As the first term, (Δp) i+1 -Δp i) / n is used to construct a tolerance including Δp i and Δp i+1 The system includes n+1 Raman shift calibration parameters. Other adjacent offset values ​​can be fitted and corrected in the same manner.

[0051] It should be understood that, taking the above arithmetic sequence as an example, other polynomial fitting or piecewise fitting can also be corrected accordingly to obtain fitting parameters that gradually change from the offset value to adjacent offset values. Specific algorithms can be selected according to actual needs and are not limited here. It should also be noted that the embodiments of the present invention are not limited to the above fitting methods; other fitting methods used to make the deviation value gradually change towards adjacent offset values ​​all fall within the protection scope of the present invention.

[0052] Furthermore, corrections can be performed in regions outside the first and last deviation values, following both the first and last deviation values. That is, the Raman shift calibration parameters for the outermost peakless regions on both sides of the spectrum can be determined based on the deviation values ​​of their outermost characteristic peaks.

[0053] In other embodiments, please refer to Figure 3 The cross-instrument Raman shift calibration for Raman spectrometers further includes the following steps: S40, plotting the Raman shift calibration parameters into a continuous calibration curve; using the same slave instrument to detect the sample to obtain the sample spectrum, and then transferring the calibration curve to the sample spectrum to obtain the abscissa calibration result of the slave instrument relative to the master instrument.

[0054] That is, by obtaining the Raman shift calibration parameters and calibration curves, the results can be transferred to the spectra obtained from the instrument under the same detection conditions to achieve calibration of the abscissa of the Raman spectrum of the instrument, thereby reducing the difference in Raman spectra measured by different Raman instruments for the same sample.

[0055] To illustrate the above method in detail, this specific example uses a standard sample prepared from a mixture of carbon tetrachloride, acetonitrile, and phenylacetylene. Raman spectroscopy was performed on both the main instrument (a LabRAM HR Evolution Raman spectrometer manufactured by Horiba, France) and the slave instrument (a confocal Raman spectrometer manufactured by Renishaw, UK), and the deviation between the Raman characteristic peak positions measured by the two instruments was calculated as follows: Figure 4 As shown, the Raman shift calibration parameters for each point on the horizontal axis within the spectral interval are obtained using a piecewise linear fitting method. Next, the master and slave instruments described above are used to perform Raman spectroscopy detection on the acetaminophen sample, and the obtained Raman shift calibration parameters are applied to the acetaminophen Raman spectrum measured by the slave instrument, thereby obtaining the following results: Figure 5The spectra before and after correction are shown below, as follows: Figure 6 The image shows a line graph illustrating the deviation values ​​of the characteristic peaks before and after correction. Figure 5 , Figure 6 It can be seen that when the obtained Raman shift calibration parameters are applied to the spectrum of acetaminophen, the peak position and deviation are effectively reduced.

[0056] As can be seen from the above embodiments, the cross-instrument Raman shift calibration method of the present invention can effectively standardize the abscissa of Raman spectra obtained under different instruments and detection conditions. The method is simple and easy to implement, and provides an effective and feasible solution for improving the comparability and standardization of spectra obtained under different instruments and detection conditions.

[0057] It should be noted that although the above embodiments only use one master instrument and one slave instrument as an example to illustrate the calibration method, in actual use, the calibration method provided by the present invention can also be extended to calibration between one master instrument and multiple slave instruments.

[0058] Please see Figure 7 The present invention also provides a cross-instrument Raman shift calibration system for Raman spectrometers, comprising at least:

[0059] The spectral detection module, based on a determined master instrument and at least one slave instrument, is used to perform Raman spectral detection on a standard sample using the master instrument and the slave instrument respectively, so as to obtain the spectral data of the master instrument and the spectral data of the slave instrument.

[0060] The spectral analysis module analyzes and processes the spectral data of the master instrument and the slave instrument respectively to obtain several first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the abscissa value of each characteristic peak on the spectrum;

[0061] The peak position calibration module calculates the deviation values ​​of the characteristic peak positions in the spectral data of the master instrument and the spectral data of the slave instrument based on the first characteristic peak position information and the second characteristic peak position information; and corrects several of the deviation values ​​to obtain the Raman shift calibration parameters of the slave instrument relative to the master instrument.

[0062] The specific implementation methods, functions, and roles of each module can be referred to in the aforementioned embodiments, and will not be repeated here.

[0063] In summary, compared with the prior art, the cross-instrument Raman shift calibration method and system for Raman spectrometers provided by this invention have the following outstanding advantages and technical effects:

[0064] I. To effectively reduce the irregular drift of Raman shift caused by instrument performance and monitoring environment, and to reduce the difference in Raman spectra measured by different Raman instruments for the same sample;

[0065] Second, there is no need to perform any peak identification operation on the Raman peaks obtained from the instrument's detection of the sample. The Raman calibration parameters provided in this embodiment can be used directly to calibrate the Raman shift axis of all spectra of the instrument. This avoids the complex workload caused by peak identification operation and avoids increasing the error between the two instruments.

[0066] Third, it requires no manual parameter adjustment, is simple and easy to operate, and can also be used as a means of standardizing Raman database spectra;

[0067] Fourth, the Raman peak position difference is considered directly from the instrument principle. The Raman shift calibration parameters obtained by calculation are used to reflect the inherent difference in Raman shift between the master instrument and the slave instrument. The accuracy of the correction is high and it can be applied to the correction of all subsequent spectra detected by the slave instrument.

[0068] Fifth, only the peak positions of the Raman spectra used as standard samples need to be analyzed; the intensity axis of the spectrum during migration has no effect on the results.

[0069] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0070] Although this document frequently uses terms such as master instrument, slave instrument, spectral data, characteristic peak, deviation value, Raman shift calibration parameter, standard sample, spectral detection module, spectral analysis module, and peak position calibration module, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention. The terms "first," "second," etc. (if present) in the specification, claims, and accompanying drawings of the embodiments of the invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for cross-instrument Raman shift calibration in Raman spectrometers, characterized in that, Includes the following steps: A master instrument and at least one slave instrument are identified; and the master instrument and the slave instrument are used to perform Raman spectroscopy detection on the standard sample to obtain the spectral data of the master instrument and the spectral data of the slave instrument, respectively. The spectral data of the master instrument and the spectral data of the slave instrument are analyzed and processed to obtain several first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the abscissa value of each characteristic peak on the spectrum; Based on the first peak position information and the second peak position information, the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument is calculated; the formula for calculating the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument is: ； in, The first element in the spectrum of the main instrument is shown. The x-coordinate values ​​of each characteristic peak; This represents the abscissa value of the i-th characteristic peak in the spectrum of the instrument; Correcting several of the aforementioned deviation values ​​to obtain the Raman shift calibration parameters of the slave instrument relative to the master instrument; the correction of several of the aforementioned deviation values ​​includes the following steps: In the numerical region between the first and last deviation values, all Raman shift calibration parameters between the first and last characteristic peaks in the spectrum are obtained by correcting all adjacent deviation values ​​using one or more methods such as arithmetic sequence fitting, polynomial fitting, and piecewise fitting. In the numerical region outside the first and last deviation values, the first deviation value is used as the Raman shift calibration parameter before the first characteristic peak in the spectrum, and the last deviation value is used as the Raman shift calibration parameter after the last characteristic peak in the spectrum.

2. The cross-instrument Raman shift calibration method for Raman spectrometers according to claim 1, characterized in that: The methods for analyzing and processing the spectral data of the master instrument and the spectral data of the slave instrument include at least one of the following data processing methods: Gaussian fitting, Lorentz fitting, and maximum value method, to determine the Raman peak position information.

3. The cross-instrument Raman shift calibration method for Raman spectrometers according to claim 1, characterized in that, The method also includes the steps of: plotting the Raman shift calibration parameters into a continuous calibration curve; using the same slave instrument to detect the sample to obtain the sample spectrum; and then transferring the calibration curve to the sample spectrum to obtain the abscissa calibration result of the slave instrument relative to the master instrument.

4. The cross-instrument Raman shift calibration method for Raman spectrometers according to claim 3, characterized in that: The standard sample and the sample to be tested have the same range of characteristic peak distribution areas.

5. A cross-instrument Raman shift calibration system for Raman spectrometers, characterized in that, include: The spectral detection module, based on a determined master instrument and at least one slave instrument, is used to perform Raman spectral detection on a standard sample using the master instrument and the slave instrument respectively, so as to obtain the spectral data of the master instrument and the spectral data of the slave instrument. The spectral analysis module analyzes and processes the spectral data of the master instrument and the slave instrument respectively to obtain several first peak position information corresponding to the spectral data of the master instrument and second peak position information corresponding to the spectral data of the slave instrument; the first peak position information and the second peak position information include the abscissa value of each characteristic peak on the spectrum; The peak position calibration module calculates the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument based on the first peak position information and the second peak position information; the formula for calculating the deviation value of the characteristic peak position in the spectral data of the master instrument and the spectral data of the slave instrument is: ;in, The first element in the spectrum of the main instrument is shown. The x-coordinate values ​​of each characteristic peak; The abscissa value of the i-th characteristic peak in the spectrum of the slave instrument is represented; the deviation values ​​are corrected to obtain the Raman shift calibration parameters of the slave instrument relative to the master instrument; the correction of the deviation values ​​includes: in the numerical region between the first and last deviation values, correcting all adjacent deviation values ​​by performing one or more methods such as arithmetic sequence fitting, polynomial fitting, and piecewise fitting to obtain all Raman shift calibration parameters between the first and last characteristic peaks in the spectrum; in the numerical region other than the first and last deviation values, the first deviation value is used as the Raman shift calibration parameter before the first characteristic peak in the spectrum, and the last deviation value is used as the Raman shift calibration parameter after the last characteristic peak in the spectrum.

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