A calibration method for a near-infrared spectrometer

Abstract

The present invention relates to instrument calibration technology, and discloses a calibration method for a near-infrared spectrometer. The method solves the problem of inaccurate measurement results caused by light source attenuation during use of the near-infrared spectrometer in the prior art. The method comprises: obtaining the absorbance of the standard plate and the absorbance of the physical sample under a standard state using the light intensity values of a standard white plate, a standard black plate, and a physical sample; and constructing a correlation model between the absorbance of the standard plate and the absorbance of the physical sample using a regression algorithm. When calibration is required, the absorbance of the standard plate and the absorbance of the physical sample under a current state are obtained using the light intensity values of the standard white plate, the standard black plate, and the physical sample; the absorbance of the standard plate under a current state is subtracted from the average value of the absorbance of the standard plate under a standard state to obtain the absorbance change of the standard plate; the absorbance change of the standard plate is then converted into the absorbance change of the physical sample; and finally, the absorbance change of the physical sample is compensated for the absorbance of the physical sample under a current state using the absorbance change of the physical sample.

Description

Technical Field

[0001] The present invention relates to an instrument calibration technology, in particular to a calibration method for a near-infrared spectrometer. Background Art

[0002] Near-infrared spectroscopy utilizes the differential absorption of specific frequencies of light by various material components, combined with chemometric methods, to enable both quantitative and qualitative analysis of material components. Compared to physical and chemical analysis, near-infrared spectroscopy is unique in that it requires no pretreatment, is non-destructive to samples, can simultaneously detect multiple parameters, and is highly rapid.

[0003] When using a near-infrared spectrometer to collect spectra, it is necessary to ensure the stability of the instrument and reduce the impact of changes in the instrument state on the displayed spectrum. In practical applications, after long-term use, the light source of the spectrometer will attenuate to a certain extent. In order to obtain accurate near-infrared spectral data, an effective instrument calibration method is required to analyze the impact of light source attenuation on the spectrum, quantify it, and compensate the current spectrum to ensure accurate and reliable detection work under the condition of light source attenuation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to propose a calibration method for a near-infrared spectrometer to solve the problem in the prior art that the measurement results of the near-infrared spectrometer are inaccurate due to light source attenuation during use.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A near-infrared spectrometer calibration method comprises the following steps:

[0007] S1. Obtain the light intensity values of the diffuse reflectance standard plate and the physical sample respectively using a near-infrared spectrometer under standard conditions (no light source attenuation), and obtain the absorbance of the standard plate and the absorbance of the physical sample under standard conditions;

[0008] S2. constructing a correlation model between the absorbance of the standard plate and the absorbance of the physical sample using a regression algorithm;

[0009] S3. When calibration is required during the actual use of the near-infrared spectrometer, the light intensity values of the diffuse reflectance standard plate and the physical sample are obtained respectively, and the absorbance of the standard plate and the absorbance of the physical sample in the current state are obtained;

[0010] S4. Calculating the absorbance change of the standard plate by combining the absorbance of the standard plate in the current state with the absorbance of the standard plate in the standard state;

[0011] S5. Based on the absorbance change of the standard plate, the absorbance change of the physical sample is calculated using a correlation model between the absorbance of the standard plate and the absorbance of the physical sample;

[0012] S6. Calculate the corrected absorbance of the physical sample based on the absorbance change of the physical sample and the absorbance of the physical sample in the current state.

[0013] Furthermore, the diffuse reflection standard plate includes a black standard plate and a white standard plate.

[0014] Furthermore, in step S1, the light intensity values of the diffuse reflectance standard plate and the physical sample are respectively obtained by a near-infrared spectrometer under a standard state to obtain the absorbance of the standard plate and the absorbance of the physical sample under the standard state, specifically including:

[0015] S11. Use a near-infrared spectrometer under standard conditions to collect near-infrared spectra of a black standard plate, a white standard plate, and a physical sample, respectively, to obtain the standard blackboard light intensity, the standard whiteboard light intensity, and the physical light intensity. By repeatedly collecting each collection target n times, a standard blackboard light intensity sample set, a standard whiteboard light intensity sample set, and a physical light intensity sample set are obtained, which are respectively expressed as

[0016] S12. Calculate the three light intensity sample sets to obtain the standard plate absorbance sample set and the physical absorbance sample set under standard conditions, which are expressed as

[0017] Furthermore, in step S11, the standard blackboard light intensity sample set The data in is represented as Standard whiteboard light intensity sample set The data in is represented as Physical light intensity sample set The data in is represented as Wherein, i=1, 2, ..., n; j=1, 2, ..., m; m is the number of wavelength points sampled by the near-infrared spectrometer in a single sampling, and n is the number of acquisition times;

[0018] Absorbance of standard plate under standard conditions and physical absorbance The calculation method is:

[0019]

[0020]

[0021] Then in step S12 The specific expressions are as follows:

[0022]

[0023]

[0024] Furthermore, in step S2, the use of a regression algorithm to construct a correlation model between the absorbance of the standard plate and the absorbance of the physical sample specifically includes:

[0025] Through a known sample set and Characterization is obtained using least squares polynomial fitting or PLS algorithm Towards The model of the mapping relationship f(x).

[0026] Furthermore, in step S3, respectively obtaining the light intensity values of the diffuse reflection standard plate and the physical sample to obtain the absorbance of the standard plate and the absorbance of the physical sample in the current state specifically includes:

[0027] The spectra of the black standard plate, white standard plate and physical sample are collected by near-infrared spectrometer to obtain a single set of standard blackboard light intensity, standard whiteboard light intensity and physical sample light intensity. The three are set as the current state of the calibration process and are expressed as

[0028] Then calculate the absorbance of the standard plate in the current state and physical absorbance

[0029]

[0030]

[0031] Furthermore, in step S4, the absorbance change of the standard plate is calculated by combining the absorbance of the standard plate in the current state with the absorbance of the standard plate in the standard state, specifically including:

[0032] Standard plate absorbance sample set under standard conditions Average each wavelength point to obtain the absorbance of the standard plate under standard conditions

[0033] Then, the absorbance of the standard plate in the current state Compared with the absorbance of the standard plate under standard conditions Subtract and get the absorbance change of the standard plate Right now

[0034] Furthermore, in step S5, the absorbance change of the physical sample is calculated based on the absorbance change of the standard plate using a correlation model between the absorbance of the standard plate and the absorbance of the physical sample, specifically including:

[0035] The absorbance change of the standard plate Substitute it into the correlation model f(x) to obtain the absorbance change of the physical sample

[0036] Furthermore, in step S6, the absorbance change of the physical sample and the absorbance of the physical sample in the current state are combined to calculate the corrected absorbance of the physical sample, which specifically includes:

[0037] Using the absorbance change of the actual object Absorbance of the object in its current state Compensate and obtain the corrected absorbance of the actual object Right now

[0038] The beneficial effects of the present invention are:

[0039] The present invention uses a diffuse reflection calibration plate as a standard sample. By constructing a correlation model between the standard sample and the physical sample under a standard state, the absorbance change of the standard plate is calculated when spectrometer calibration is required. The absorbance change of the corresponding physical sample is then obtained through the correlation model, and the absorbance of the physical sample measured in the current state is compensated based on the absorbance change. Since the present invention quantifies the influence caused by the attenuation of the near-infrared spectrometer light source, it can eliminate noise in the physical spectrum and improve the authenticity of the physical spectrum data. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of the calibration method of the near-infrared spectrometer in the present invention;

[0041] Figure 2 Schematic diagram of the standard construction process in the near-infrared spectrometer calibration method in an embodiment of the present invention.

[0042] Figure 3 Schematic diagram of the absorbance compensation process of an object in the near-infrared spectrometer calibration method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] This invention aims to provide a near-infrared spectrometer calibration method to address the existing problem of inaccurate measurement results caused by light source attenuation during use. Diffuse reflectance standards provide the highest diffuse reflectance values for any known substance. These durable, chemically inert standards have typical reflectance values ranging from 2% to 99% and exhibit a flat spectrum across the UV-Vis-NIR spectral region. Due to their high stability, diffuse reflectance standards can be used as reference samples for calibrating optical equipment and systems.

[0044] Based on this, the calibration method of the near-infrared spectrometer provided by the present invention is as follows: Figure 1 As shown, it includes the following steps:

[0045] S1. Obtain the light intensity values of the diffuse reflectance standard plate and the physical sample respectively using a near-infrared spectrometer under standard conditions (no light source attenuation), and obtain the absorbance of the standard plate and the absorbance of the physical sample under standard conditions;

[0046] S2. constructing a correlation model between the absorbance of the standard plate and the absorbance of the physical sample using a regression algorithm;

[0047] S3. When calibration is required during the actual use of the near-infrared spectrometer, the light intensity values of the diffuse reflectance standard plate and the physical sample are obtained respectively, and the absorbance of the standard plate and the absorbance of the physical sample in the current state are obtained;

[0048] S4. Calculating the absorbance change of the standard plate by combining the absorbance of the standard plate in the current state with the absorbance of the standard plate in the standard state;

[0049] S5. Based on the absorbance change of the standard plate, the absorbance change of the physical sample is calculated using a correlation model between the absorbance of the standard plate and the absorbance of the physical sample;

[0050] S6. Calculate the corrected absorbance of the physical sample based on the absorbance change of the physical sample and the absorbance of the physical sample in the current state.

[0051] Example:

[0052] In this embodiment, the calibration method of the near-infrared spectrometer is divided into two parts. The first part is the standard construction process (corresponding to steps S1-S2 in the calibration method process), and the second part is the physical absorbance compensation process (corresponding to steps S3-S6 in the calibration method process). The specific description is as follows:

[0053] See also Figure 2 , the standard build process includes:

[0054] Step 101: Obtain a standard light intensity sample set:

[0055] In this step, a near-infrared spectrometer is used to collect the near-infrared spectra of the black standard plate, the white standard plate and the real object, and the standard blackboard light intensity, the standard whiteboard light intensity and the real object light intensity are obtained. The light intensity of these three is set as the standard state of the calibration process. The collection is repeated n times, and multiple groups of samples constitute a standard light intensity sample set, which are respectively expressed as

[0056] In a specific example, a near-infrared spectrometer is used to collect spectra of three samples six times. The intensity data from these six acquisitions is then averaged to produce a single set of intensity data as the acquisition result output. The near-infrared spectrometer samples 50 wavelengths per single acquisition. Therefore, the matrix of the three intensity sample sets has n rows and 50 columns.

[0057] Step 102: Obtain a standard absorbance sample set:

[0058] In this step, the three light intensity sample sets are calculated to obtain the standard plate absorbance sample set and the physical absorbance sample set under standard conditions. The three standard light intensity sample sets are converted into standard absorbance sample sets, which are expressed as

[0059] In a specific example, the absorbance of the standard plate under standard conditions is calculated as follows:

[0060]

[0061] The absorbance sample set of the standard plate under standard conditions is:

[0062]

[0063] The calculation method of the absorbance of the substance under standard conditions is:

[0064]

[0065] Then the physical absorbance sample set under standard conditions is:

[0066]

[0067] Step 103: Establish a correlation model between the absorbance of the standard plate and the absorbance of the actual object:

[0068] In this step, the regression algorithm is used to construct the standard plate absorbance sample set and physical absorbance sample sets In a specific example, the regression algorithm is: through a known sample set and Characterization is obtained using least squares polynomial fitting or PLS algorithm Towards The model of the mapping relationship f(x).

[0069] During the actual use of the near-infrared spectrometer, the light source will attenuate. When the light source attenuates, the near-infrared spectra of the standard plate and the actual object will also change. We can use the absorbance change of the standard plate combined with the mapping relationship model to calculate the absorbance change of the actual object, thereby compensating for the actual absorbance of the current state. For the specific process, see Figure 3 ,include:

[0070] Step 201: Sample spectrum acquisition in the current state:

[0071] In this step, a near-infrared spectrometer is used to collect spectra of the three samples, and a single set of standard blackboard light intensity, standard whiteboard light intensity and actual light intensity are obtained. The three are set as the current state of the calibration process, which are expressed as

[0072] The method for collecting the light intensity data of the three samples is the same as that in step 101, except that the number of collection times in this step is only a single time.

[0073] Step 202: Calculate the absorbance of the standard plate and the absorbance of the object in the current state:

[0074] In this step, the absorbance of the standard plate in the current state is calculated using the above three samples. and physical absorbance The calculation method of absorbance is the same as that in step 102.

[0075] Step 203: Calculate the absorbance of the standard plate under standard conditions:

[0076] In this step, the absorbance sample set of the standard plate under standard conditions is The absorbance of the standard plate under standard conditions is obtained by averaging each wavelength point.

[0077] Step 204: Calculate the absorbance change of the standard plate:

[0078] In this step, the absorbance of the standard plate in the current state is subtracted from the absorbance of the standard plate in the standard state to obtain the absorbance change of the standard plate, that is,

[0079] Step 205: Calculate the absorbance change of the physical sample:

[0080] In this step, Substitute into the model f(x) to obtain the absorbance change of the actual sample

[0081] Step 206: Compensate the absorbance of the physical sample:

[0082] In this step, the absorbance variation of the object is used Absorbance of the object in its current state Compensate and get the actual absorbance Right now

[0083] Finally, it should be noted that the above embodiments are merely preferred implementations and are not intended to limit the present invention. It should be noted that those skilled in the art will be able to make modifications, equivalent substitutions, and improvements without departing from the spirit and scope of the present invention and the claims, all of which should be included within the scope of protection of the present invention.

Claims

1. A calibration method for a near-infrared spectrometer, characterized in that: The following steps are involved: S1. Obtain the light intensity values of the diffuse reflectance standard plate and the physical sample respectively by using a near-infrared spectrometer under standard conditions to obtain the absorbance of the standard plate and the absorbance of the physical sample under standard conditions; S2. constructing a correlation model between the absorbance of the standard plate and the absorbance of the physical sample using a regression algorithm; S3. When calibration is required during the actual use of the near-infrared spectrometer, the light intensity values of the diffuse reflectance standard plate and the physical sample are obtained respectively, and the absorbance of the standard plate and the absorbance of the physical sample in the current state are obtained; S4. Calculating the absorbance change of the standard plate by combining the absorbance of the standard plate in the current state with the absorbance of the standard plate in the standard state; S5. Based on the absorbance change of the standard plate, the absorbance change of the physical sample is calculated using a correlation model between the absorbance of the standard plate and the absorbance of the physical sample; S6. Calculate the corrected absorbance of the physical sample based on the absorbance change of the physical sample and the absorbance of the physical sample in the current state.

2. The calibration method of a near-infrared spectrometer according to claim 1, wherein: The diffuse reflection standard plate includes a black standard plate and a white standard plate.

3. A near-infrared spectrometer calibration method as claimed in claim 2, characterized in that, In step S1, the light intensity values of the diffuse reflectance standard plate and the physical sample are respectively obtained by a near-infrared spectrometer under a standard state to obtain the absorbance of the standard plate and the absorbance of the physical sample under the standard state, which specifically includes: S11. Use a near-infrared spectrometer under standard conditions to collect near-infrared spectra of a black standard plate, a white standard plate, and a physical sample, respectively, to obtain the standard blackboard light intensity, the standard whiteboard light intensity, and the physical light intensity. By repeatedly collecting each collection target n times, a standard blackboard light intensity sample set, a standard whiteboard light intensity sample set, and a physical light intensity sample set are obtained, which are respectively expressed as S12. Calculate the three light intensity sample sets to obtain the standard plate absorbance sample set and the physical absorbance sample set under standard conditions, which are expressed as 4. A near-infrared spectrometer calibration method as claimed in claim 3, characterized in that, In step S11, the standard blackboard light intensity sample set The data in is represented as Standard whiteboard light intensity sample set The data in is represented as Physical light intensity sample set The data in is represented as Wherein, i=1, 2, ..., n; j=1, 2, ..., m; m is the number of wavelength points sampled by the near-infrared spectrometer in a single sampling, and n is the number of acquisition times; Absorbance of standard plate under standard conditions and physical absorbance The calculation method is: Then in step S12 The specific expressions are as follows:

5. A near-infrared spectrometer calibration method as claimed in claim 4, characterized in that, In step S2, the use of a regression algorithm to construct a correlation model between the absorbance of the standard plate and the absorbance of the physical sample specifically includes: Through a known sample set and Characterization is obtained using least squares polynomial fitting or PLS algorithm Towards The model of the mapping relationship f(x).

6. A near-infrared spectrometer calibration method as claimed in claim 5, characterized in that: In step S3, the light intensity values of the diffuse reflection standard plate and the physical sample are respectively obtained to obtain the absorbance of the standard plate and the absorbance of the physical sample in the current state, which specifically includes: The spectra of the black standard plate, white standard plate and physical sample are collected by near-infrared spectrometer to obtain a single set of standard blackboard light intensity, standard whiteboard light intensity and physical sample light intensity. The three are set as the current state of the calibration process and are expressed as Then calculate the absorbance of the standard plate in the current state and physical absorbance 7. A near-infrared spectrometer calibration method as claimed in claim 6, characterized in that: In step S4, the absorbance change of the standard plate is calculated by combining the absorbance of the standard plate in the current state with the absorbance of the standard plate in the standard state, which specifically includes: Standard plate absorbance sample set under standard conditions Average each wavelength point to obtain the absorbance of the standard plate under standard conditions Then, the absorbance of the standard plate in the current state Compared with the absorbance of the standard plate under standard conditions Subtract and get the absorbance change of the standard plate Right now 8. A near-infrared spectrometer calibration method as claimed in claim 7, characterized in that: In step S5, the absorbance change of the physical sample is calculated based on the absorbance change of the standard plate using a correlation model between the absorbance of the standard plate and the absorbance of the physical sample, specifically including: The absorbance change of the standard plate Substitute it into the correlation model f(x) to obtain the absorbance change of the physical sample 9. A near-infrared spectrometer calibration method as claimed in claim 8, characterized in that: In step S6, the absorbance change of the physical sample and the absorbance of the physical sample in the current state are combined to calculate the corrected absorbance of the physical sample, which specifically includes: Using the absorbance change of the actual object Absorbance of the object in its current state Compensate and obtain the corrected absorbance of the actual object Right now

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