Calibration material and calibration method for calibrating spectral responsivity of Raman spectrometer

Abstract

The invention relates to a calibration material and a calibration method for calibrating the spectral responsivity of a Raman spectrometer. A calibration material for calibrating a Raman spectrometer includes a reference material configured to emit a broadband spectrum of luminescent light in response to receiving excitation light; and an additional material that exhibits different Raman bands within a spectral measurement range of the Raman spectrometer. A method of calibrating at least one Raman spectrometer using the disclosed calibration material includes: determining emission spectra of the calibration material at a plurality of temperatures; and calibrating each Raman spectrometer based on the calibration spectrum of the calibration material determined by the Raman spectrometer; the temperature of the calibration material is determined through Raman temperature measurement; and adjusting the determination of the spectral intensity value of the intensity spectrum performed by the respective Raman spectrometer based on the calibration spectrum, the temperature of the calibration material during calibration, and the emission spectrum of the calibration material.

Description

Technical Field

[0001] The present disclosure relates to a calibration material for calibrating the spectral responsivity of at least one Raman spectrometer and a method of calibrating the spectral responsivity of at least one Raman spectrometer using the calibration material. Background Art

[0002] Raman spectrometers are currently used in a large number of different applications, including industrial applications as well as laboratory applications, to determine and provide measurement values ​​of various measured objects of a medium. As an example, Raman spectrometers are used to determine the concentration of components included in the medium, the pH value of the medium, the melt index of the medium and / or the cell motility of the medium.

[0003] Conventional Raman spectrometers generally include a light source that transmits monochromatic excitation light to a medium sample and a spectrometric unit that receives Raman scattered light emitted from the sample and determines and provides an intensity spectrum of the Raman scattered light. The intensity spectrum is provided, for example, to an evaluation unit that determines and generates a measurement value of the corresponding measured object based on a previously determined model for determining a measurement value based on the spectral intensity of the intensity spectrum.

[0004] The model used for Raman spectroscopy to determine quantitative measurements of the measured object can be determined, for example, based on measurements performed on samples that exhibit known values ​​of the corresponding measured object and a detailed mathematical analysis of the sample spectra determined and provided by these measurements. However, the determination of a suitable model is a laborious and time-consuming process, particularly because of the complexity of the mutual correlation between the spectral intensity of the sample spectrum and the known values ​​of the measured variable, and / or due to the influence of other properties of the medium that may affect the spectral intensity and / or the spectral distribution of the measured spectrum. Accordingly, it is desirable to use the same one or more models on multiple Raman spectrometers.

[0005] However, different Raman spectrometers exhibit different spectral responsivities. As a result, the spectral shapes and absolute spectral intensities of intensity spectra of the same sample determined by different Raman spectrometers may differ. Therefore, reusing the same model on multiple Raman spectrometers requires calibrating the spectral responsivities of the Raman spectrometers in a way that ensures that they exhibit at least approximately the same spectral response over their spectral measurement range.

[0006] US 6,351,306 B1 discloses a method for calibrating the spectral responsivity of a Raman spectrometer based on the known emission spectrum of a broadband intensity calibration light source (e.g., a tungsten lamp). According to the method, a calibration spectrum of light emitted by the intensity calibration light source determined using the Raman spectrometer to be calibrated is used to determine the spectral responsivity of the corresponding Raman spectrometer, and then the determination of the spectral intensity values ​​of the intensity spectrum performed by the corresponding Raman spectrometer is adjusted based on the calibration spectrum and the known emission spectrum of the broadband intensity calibration light source.

[0007] However, a disadvantage of this approach is that anything that may change the spectral balance of the light emitted by the broadband intensity calibration light source and its presentation to the spectrometric unit of the corresponding Raman spectrometer will lead to corresponding calibration errors, for example, calibration errors due to incorrect determination and / or incorrect adjustment of the spectral responsivity. As an example, when a tungsten bulb is used as a black body radiator, changes in the drive current supplied to the tungsten bulb as well as aging of the tungsten filament may change the emissivity of the broadband intensity calibration light source. In addition, the light propagation path of the light emitted by the black body radiator may deviate from the light propagation path of the light emitted from the sample of the medium during the spectral measurement of the measured object performed with the corresponding Raman spectrometer. Therefore, differences in the light propagation paths may also contribute to the corresponding calibration errors.

[0008] As an alternative, a spectral responsivity calibration measurement may be performed on a reference material that emits a known emission spectrum in response to being illuminated by the excitation light. In such a method, the reference material is illuminated by the light source of the Raman spectrometer to be calibrated, and the adjustment of the determination of the spectral intensity values ​​of the intensity spectrum performed by the Raman spectrometer is performed based on the calibration spectrum of the reference material determined by the Raman spectrometer and the known emission spectrum of the reference material.

[0009] Reference materials suitable for this purpose include the Standard Reference Materials (SRMs) developed by the National Institute of Standards and Technology (NIST) for many different excitation wavelengths for relative intensity calibration of Raman spectroscopy instruments. These SRMs include specific types of fluorescent glasses that can be used with the published emission spectra of these SRMs.

[0010] Reference materials illuminated by the light source of the Raman spectrometer give a more realistic account of the position of the sample and the corresponding light propagation path. However, a disadvantage of reference materials such as fluorescent glass is that they are temperature sensitive. Accordingly, the known emission spectra of these reference materials are only valid within a narrow temperature range around the reference temperature of the reference material for which the emission spectrum is determined.

[0011] Certain improvements in spectral responsivity calibration relative to calibration spectra performed based on reference materials can be achieved by a method for improving calibration transfer between multiple Raman analyzer devices disclosed in US 11,287,384 B2. According to the method, multiple SRMs are provided, and reference spectra for each SRM sample are generated under factory controlled conditions using the same measuring instrument and measurement parameters. The method also includes calibrating the intensity axis of the Raman spectrometer at multiple Raman analyzer devices based on the Raman calibration spectra of the SRM samples determined by the corresponding Raman spectrometers and the reference spectra of the SRM samples previously determined.

[0012] US 11,287,384 B2 also discloses taking into account the temperature dependence of the emission spectra of these reference materials based on a temperature measurement of the temperature of the SRM sample performed by an additional temperature measuring device, which enables a temperature compensated spectral responsivity calibration. However, a disadvantage is that this method requires a temperature measuring device that may not always be available and that this method can only be applied to Raman spectrometer configurations that allow the temperature measuring device to be positioned near the SRM sample.

[0013] Therefore, further contributions are still needed in this area of ​​technology. Summary of the invention

[0014] As an example, a calibration material and / or calibration method is needed that enables accurate temperature-compensated spectral responsivity calibration of a Raman spectrometer without requiring additional temperature measurement equipment to measure the temperature of the calibration material and / or without requiring the temperature of the calibration material to be controlled so that it occurs within a very narrow temperature range.

[0015] The present disclosure includes a method of calibrating at least one Raman spectrometer, each Raman spectrometer including: a monochromatic light source configured to transmit excitation light having a desired excitation wavelength to a measurement region configured to accommodate a sample of a medium; and a spectrometry unit configured to receive measurement light emitted from the illuminated sample and configured to determine and provide an intensity spectrum of the received measurement light in a spectral measurement range, the method comprising:

[0016] providing a calibration material, the calibration material comprising a reference material configured to emit a broadband spectrum of luminescence light in response to the reference material receiving excitation light having a desired excitation wavelength, and an additional material exhibiting different Raman bands within a spectral measurement range of a Raman spectrometer to be calibrated;

[0017] for at least two different temperatures, in response to the calibration material receiving excitation light having a desired excitation wavelength, determining an emission spectrum of light emitted by the calibration material exhibiting the corresponding temperature; and

[0018] Each Raman spectrometer is calibrated by:

[0019] Determining a calibration spectrum of a calibration material using a corresponding Raman spectrometer;

[0020] determining the temperature of the calibration material by performing Raman thermometry based on the Raman bands included in the calibration spectrum; and

[0021] The determination of the spectral intensity values ​​of the intensity spectrum performed by the respective Raman spectrometer is adjusted based on the calibration spectrum, the temperature of the calibration material of the calibration spectrum and the previously determined emission spectrum of the calibration material.

[0022] The calibration material comprising the reference material and the additional material provides the advantage that the current spectral responsivity of each Raman spectrometer and the temperature of the calibration material during determination of the respective calibration spectrum can be determined based on the calibration spectrum of the calibration material.

[0023] Determining the temperature of the calibration material during determination of the calibration spectrum provides the advantage that a highly accurate calibration of the spectral responsivity of each Raman spectrometer is obtained in a manner taking into account the temperature of the calibration material during calibration and the temperature dependence of the emission spectrum of the calibration material.

[0024] The method also offers the advantage that the calibration material can be used over a wider temperature range than the reference material employed in the prior art and that it requires neither control of the temperature of the calibration material nor measurement by an additional temperature measuring device during determination of the calibration spectrum.

[0025] In certain embodiments, providing the calibration material includes manufacturing the calibration material by melting a reference material and distributing a powder of the additional material in the molten reference material.

[0026] In an alternative embodiment, providing the calibration material comprises manufacturing the calibration material by applying at least one layer of an additional material onto an outer surface of a reference material, or by depositing at least one layer of an additional material onto an outer surface of a reference material by performing a deposition process, a low temperature deposition process or a vacuum deposition process.

[0027] In a first embodiment, for at least one or each Raman spectrometer, the temperature of the calibration material is determined by determining the peak position of a Raman peak associated with a Raman band of an additional material included in the calibration spectrum and based on a previously determined relationship between the peak position of the Raman peak included in the calibration spectrum and the peak position of the Raman peak associated with the Raman band exhibited by the additional material and the temperature of the calibration material.

[0028] Certain embodiments of the method according to the first embodiment also include a method step of determining the relationship between the peak position of the Raman peak associated with the Raman band exhibited by the additional material and the temperature of the calibration material based on the peak position of the Raman peak included in the emission spectrum and the temperature of the calibration material whose emission spectrum has been determined.

[0029] In certain embodiments of the first embodiment, the Raman peak is a Stokes peak occurring in a spectral measurement range of a corresponding Raman spectrometer.

[0030] The present invention also includes a second embodiment, wherein:

[0031] The Raman spectrometer to be calibrated comprises at least one dual-range spectrometer capable of determining an intensity spectrum within a range comprising the spectral measurement range and an additional range; wherein the spectral measurement range is a range covering a Stokes region including spectral lines corresponding to wavelengths longer than the excitation wavelength, and the additional range is a range covering an anti-Stokes region including spectral lines corresponding to wavelengths shorter than the excitation wavelength;

[0032] The emission spectra of the calibration materials are each determined within a spectral range that includes the spectral measurement range and the additional range; and

[0033] For at least one or each of the dual range spectrometers, a calibration spectrum of the calibration material is determined within a spectral range that includes the spectral measurement range and the additional range; and a temperature of the calibration material is determined based on the calibration spectrum by:

[0034] determining a ratio of a peak intensity of a Stokes Raman peak included in the calibration spectrum to a peak intensity of an anti-Stokes Raman peak included in the calibration spectrum, wherein both the Stokes Raman peak and the anti-Stokes Raman peak are associated with Raman bands of the additional material;

[0035] The temperature of the calibration material is determined based on a ratio of a peak intensity of a Stokes Raman peak included in the calibration spectrum to a peak intensity of an anti-Stokes Raman peak included in the calibration spectrum and a previously determined relationship between a ratio of peak intensities of Stokes Raman peaks and anti-Stokes Raman peaks associated with the Raman band and the temperature of the calibration material.

[0036] Certain embodiments of the method according to the second embodiment also include a method step of determining a relationship between a ratio of peak intensities of Stokes Raman peaks and anti-Stokes Raman peaks associated with a Raman band and a temperature of the calibration material based on peak intensities of the Stokes Raman peaks and corresponding anti-Stokes Raman peaks included in the emission spectrum of the calibration material and the temperature of the calibration material whose emission spectrum has been determined.

[0037] In certain embodiments, for at least one or each Raman spectrometer, the determination of the spectral intensity values ​​of the intensity spectrum performed by the corresponding Raman spectrometer is performed by determining, based on the emission spectrum, a reference spectrum exhibited by a calibration material at a temperature that has been determined based on the calibration spectrum, and determining and applying a spectral correction term, a spectral correction factor, or a spectral correction function for correcting the spectral intensity values ​​determined by the corresponding Raman spectrometer, so that the corrected spectral intensity values ​​of the calibration spectrum correspond to the spectral intensity values ​​of the reference spectrum within the entire spectral measurement range.

[0038] In certain embodiments, the at least two different temperatures at which the emission spectra are determined cover a predetermined temperature range, which is a temperature range of 10°C to 50°C or a temperature range of -20°C to 100°C.

[0039] The present disclosure also includes calibration materials for calibrating the spectral responsivity of at least one Raman spectrometer, the calibration materials including a reference material and an additional material, the reference material being configured to emit a broadband spectrum of luminescent light in response to the reference material receiving excitation light having a desired excitation wavelength, the additional material exhibiting different Raman bands within the spectral measurement range of the Raman spectrometer to be calibrated.

[0040] In certain embodiments of the calibration material, the reference material is a standard reference material (SRM) or fluorescent glass.

[0041] In certain embodiments of the calibration material, the additional material is carbon, diamond, sapphire, silicon, calcium fluoride (CaF2), or lithium niobate (LiNbO3).

[0042] The present disclosure also includes embodiments of the calibration material, wherein the additional material is a material that exhibits a single Raman band within the spectral measurement range of the Raman spectrometer, a material that exhibits a narrow Raman band within the spectral measurement range of the Raman spectrometer, and / or a material that exhibits a Raman band having a Raman peak with a full width at half maximum that is less than or equal to a given percentage (a percentage of 10% or a percentage of 1%) of the width of the spectral measurement range of the Raman spectrometer.

[0043] In certain embodiments of the calibration material, the additional material is distributed within the reference material, or at least one layer of additional material each covers an outer surface of the reference material. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The described embodiments and other features, advantages and disclosures contained herein and the manner in which they are obtained will be better understood by reference to the following description of various embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which:

[0045] Figure 1 A Raman spectrometer is shown;

[0046] Figure 2 A flow chart of a calibration method according to the present disclosure is shown;

[0047] Figure 3 A calibration material comprising an additional material distributed in a reference material is shown;

[0048] Figure 4 showing a calibration material comprising an additional material layer on an outer surface of a reference material;

[0049] Figure 5 The emission spectra of the calibration materials at different temperatures are shown;

[0050] Figure 6 The calibration spectrum and the reference spectrum are shown;

[0051] Figure 7 shows the emission spectra of the calibration material at different temperatures within the spectral measurement range and the additional spectral range; and

[0052] Figure 8 The performance in the spectral measurement range and additional range is shown Figure 7 Calibration spectra of calibration materials for which emission spectra are shown. DETAILED DESCRIPTION

[0053] The present disclosure includes a calibration material CM for calibrating the spectral responsivity of at least one Raman spectrometer 100 and a method of calibrating the spectral responsivity of at least one Raman spectrometer 100 using the calibration material CM.

[0054] Figure 1 An example of a Raman spectrometer 100 is shown in . The Raman spectrometer 100 comprises a monochromatic light source 1, such as a laser, which is configured to transmit an excitation light L0 having a desired excitation wavelength λ0 to a measurement region 3 configured to accommodate a sample S of a medium.

[0055] In some embodiments, the excitation wavelength λ0 is, for example, a wavelength in the visible or near infrared wavelength range. As a non-limiting example, the excitation wavelength λ0 may be a wavelength of 785 nm, 532 nm, 405 nm, or another wavelength in the visible or near infrared wavelength range.

[0056] In some embodiments, the Raman spectrometer 100 may include a filter 5 , such as a notch filter, configured to filter out the measurement light LR included in the light L1 emitted from the measurement region 3 .

[0057] The Raman spectrometer 100 further comprises a spectrometric unit 7 configured to receive measurement light LR emitted from the illuminated sample S and configured to determine and generate an intensity spectrum I(λ) of the measurement light LR.

[0058] The intensity spectra I(λ) are determined, for example, in a spectral range including the spectral measurement range Δλ of the Raman spectrometer 100. The spectral measurement range Δλ is, for example, a wavelength range or a wavenumber range corresponding to a range of positive wavenumber shifts of Raman scattered light caused by the excitation light L0 having the excitation wavelength λ0.

[0059] In at least one embodiment, the spectral measurement range Δλ is a range covering the Stokes region of the Raman spectrum including spectral lines corresponding to wavelengths greater than the excitation wavelength λ0, for example, corresponding to a range greater than or equal to 0 cm -1 And less than or equal to 4500cm -1The wavenumber shift of the Raman spectrometer 100 may be a range of a wavenumber shift range, or a sub-range of the wavenumber shift range that is of particular interest relative to the object to be measured using the Raman spectrometer 100 .

[0060] In at least one embodiment, the spectrometric unit 7 comprises: a disperser 9, such as a diffraction or holographic grating, which is suitable for dispersing incident measurement light LR; a detector 11, which is configured to receive the dispersed measurement light LR; and a signal processor 13, such as a microprocessor, which is connected to the detector 11. The detector 11 is configured to generate and provide a detector signal corresponding to the spectral intensity of the incident dispersed measurement light LR. The signal processor 13 is configured to generate and provide an intensity spectrum I(λ) of the measurement light LR based on the detector signal.

[0061] Figure 1 An exemplary embodiment is shown in which the detector 11 comprises an array of detection elements, such as a charge coupled device (CCD) array or a photodiode array, each detection element receiving a portion of the scattered light and generating a detector signal corresponding to the intensity of the received fraction and providing it to a signal processor 13 to determine a spectral intensity value of the intensity spectrum I(λ) based on the detector signal.

[0062] In certain embodiments, at least one or each Raman spectrometer 100 is configured to measure at least one measured object of the medium, for example, to measure the concentration of at least one component included in the medium, the pH value of the medium, the melt index of the medium, the cell viability of the medium and / or another characteristic of interest of the medium.

[0063] During the measurement of the measured object, a sample S of the medium is positioned in the measurement area 3 and illuminated by the light source 1. In this case, the measurement light LR includes Raman scattered light emitted from the illuminated sample S, and the intensity spectrum I(λ) generated by the spectrometry unit 7 is the Raman spectrum of the sample S of the medium. The Raman spectrum thus determined is provided, for example, to an evaluation unit 15, which determines and provides a measurement value mv of the corresponding measured object based on a previously determined model M for determining the measurement value mv based on the spectral intensity of the Raman spectrum generated by the spectrometry unit 7. The evaluation unit 15 is, for example, an integral component of the Raman spectrometer 100 or an external unit configured to receive the intensity spectrum I(λ) determined by the spectrometry unit 7. In either case, the evaluation unit 15 is, for example, connected to the spectrometry unit 7 or communicates with the spectrometry unit 7.

[0064] like Figure 2 As illustrated in the flowchart shown, the method 200 for calibrating at least one Raman spectrometer 100 disclosed herein comprises a method step A1 of providing a calibration material CM for calibrating the spectral responsivity of one or more Raman spectrometers 100 .

[0065] The calibration material CM disclosed herein includes a reference material and an additional material, wherein the reference material is configured to emit a luminescence spectrum in response to receiving excitation light having a desired excitation wavelength λ0 and the additional material exhibiting different Raman bands within a measurement range Δλ of the Raman spectrometer 100 being calibrated.

[0066] Including a reference material in the calibration material CM provides the advantage of enabling calibration of the spectral responsivity of the Raman spectrometer 100 to be performed in the entire spectral measurement range Δλ covered by the broadband emission spectrum of the reference material. Including an additional material in the calibration material CM provides the advantage of enabling determination of the temperature T of the calibration material CM by Raman thermometry. CM Advantages.

[0067] Regarding the reference material, materials used in the art for the purpose of relative intensity calibration of Raman spectroscopy instruments can be used. As an example, in some embodiments, the reference material is a material given by, for example, the SRM developed by NIST. In such an embodiment, the reference material is, for example, a specific type of fluorescent glass. Alternatively, another type of material that emits a broadband spectrum of luminescent light in response to receiving excitation light can be used as a reference material.

[0068] As for the additional material, various Raman active substances can be used, including elements or compounds that exhibit a well-defined Raman signature.

[0069] In some embodiments, the additional material is, for example, a material that exhibits a single Raman band within the spectral measurement range Δλ. Additionally or alternatively, the additional material is, for example, a material that exhibits a narrow Raman band, for example, a narrow band that exhibits a Raman peak with a full width at half maximum or a given percentage (e.g., 10% or, for example, only 1%) of the width of the spectral measurement range Δλ.

[0070] As examples, in certain embodiments, the additional material is, for example, carbon, diamond, sapphire, silicon, calcium fluoride (CaF2), or lithium niobate (LiNbO3).

[0071] Regardless of the type of additional material employed, in some embodiments, the additional material is, for example, distributed in the reference material. In such embodiments, providing the calibration material CM, for example, may include manufacturing the calibration material CM by melting the reference material and distributing a powder (e.g., a finely crushed powder) of the additional material in the molten reference material, for example in molten fluorescent glass. Figure 3 An example of a corresponding calibration material CM is shown, where the additional material distributed in the reference material is indicated by dots.

[0072] In an alternative embodiment, the additional material is included in the calibration material CM, for example in the form of at least one layer 17 of the additional material, each layer 17 covering an outer surface of the reference material 19. In such embodiments, providing the calibration material CM, for example, may include manufacturing the calibration material CM by applying the or each layer 17 of the additional material to a corresponding outer surface of the reference material 19. As an example, each layer 17 of the additional material (for example) is deposited onto an existing reference material 19 (for example, an SRM developed by NIST) using a deposition process (for example, a low temperature deposition process, such as a vacuum deposition process). This manufacturing method provides the advantage that the reference material 19 does not need to be melted. Figure 4 An embodiment of a corresponding calibration material CM is shown, wherein a layer 17 of additional material is applied on an opposing outer surface of a reference material 19 .

[0073] like Figure 2 As shown, the method 200 further comprises determining an emission spectrum E of the light emitted by the calibration material CM for at least two different temperatures Ti. Ti (λ) method step A2, each temperature Ti assumes the respective temperature Ti in response to the calibration material CM receiving excitation light having an excitation wavelength λ0.

[0074] Emission spectrum Ti (λ) are each determined, for example, based on at least one intensity spectrum generated and provided by a spectroscopic measuring instrument, which illuminates the calibration material CM with excitation light having an excitation wavelength λ0, while the calibration material CM exhibits a corresponding temperature Ti and in response determines and generates an intensity spectrum of light emitted by the illuminated calibration material CM. As an example, the emission spectrum E Ti (λ) are each determined, for example, under laboratory conditions, wherein in determining each emission spectrum E Ti During (λ), the temperature Ti of the calibration material CM is controlled and / or measured by a temperature measuring device.

[0075] Since the calibration material CM includes the reference material and the additional material, the temperature-dependent emission spectrum E Ti (λ) each corresponds to the superposition of the temperature-dependent broadband emission spectrum of the reference material and the Raman scattered light emitted by the additional material.

[0076] The superposition Figure 5 , which shows exemplary emission spectra E of the same calibration material CM at different temperatures Ti in the spectral measurement range Δλ. Ti (λ). The exemplary emission spectrum E shown Ti (λ) includes a first emission spectrum E determined at a first temperature T1 T1 (λ), the second emission spectrum E determined at the second temperature T2 T2(λ) and the third emission spectrum E determined at the third temperature T3 T3 (λ), wherein the second temperature T2 is higher than the first temperature T1 and the third temperature T3 is higher than the second temperature T2.

[0077] In certain embodiments, the different temperatures Ti for example cover a predetermined temperature range, such as a temperature range of 10°C to 50°C or for example -20°C to 100°C.

[0078] like Figure 5 As shown, additional materials exhibiting different Raman bands make each emission spectrum E Ti (λ) exhibits a unique Raman peak P associated with the Raman band Ti , which is superimposed on the broadband emission spectrum of the reference material.

[0079] The method 200 further comprises calibrating each Raman spectrometer 100 by performing the following steps: method step A3, which is to determine a calibration spectrum I of the calibration material CM using the corresponding Raman spectrometer 100: CM (λ); Method step A4, which is based on the calibration spectrum I CM The Raman band included in (λ) determines the temperature T of the calibration material CM CM ; and method step A5, which is based on the calibration spectrum I CM (λ), in the calibration spectrum I CM The temperature T of the calibration material CM during the determination of (λ) CM and the previously determined emission spectrum E of the calibration material CM Ti (λ) adjusts the spectral intensity value of the intensity spectrum I(λ) performed by the corresponding Raman spectrometer 100 .

[0080] In method step A3, a calibration spectroscopy I is performed, for example by positioning a calibration material CM in the measurement region 3 of the Raman spectrometer 100. CM (λ) is determined so that the light source 1 transmits the excitation light L0 having the desired excitation wavelength λ0 to the calibration material CM, and by using the spectral unit 7, a calibration spectrum I of the measurement light LR emitted from the illuminated calibration material CM is determined and generated. CM (λ).

[0081] In method step A4, by performing a Raman temperature measurement method, based on the calibration spectrum I CM The Raman band included in (λ) determines the temperature T of the calibration material CM CMAn example of a Raman thermometry method that can be used in method step A4 is described, for example, in the article by David Tuchel entitled “Raman Thermometry” (published on December 1, 2016, Spectroscopy, Volume 31, Issue 12, pages 8 to 13). As outlined in the article, the temperature of a material can be determined based on the ratio of the temperature dependence of the Stokes and anti-Stokes signal intensities for a given Raman band, and the temperature of a material exhibiting a sufficiently narrow Raman band can also be determined based on the temperature-dependent position of the associated Raman peak.

[0082] from Figure 5 The emission spectrum E shown in Ti (λ) It is obvious that when the temperature Ti of the calibration material CM increases, the emission spectrum E Ti The Raman peak P included in (λ) Ti The peak position λp(Ti) of the calibration material CM is shifted to a longer wavelength. Accordingly, the method 200 includes, for example, a first embodiment in which the temperature T of the calibration material CM CM Based on the calibration spectrum I CM The peak position λ of the Raman peak P associated with the Raman band exhibited by the additional material in (λ) P (T CM ) to determine.

[0083] The first embodiment is Figure 6 , which shows the calibration spectrum I of the calibration material CM CM (λ), the calibration spectrum shows Figure 5 The temperature-dependent emission spectrum E Ti In this first embodiment, method step A4 comprises determining a calibration spectrum I of the calibration material CM determined by the Raman spectrometer 100 to be calibrated. CM The peak position λ of the Raman peak P included in (λ) P (T CM ), and based on the calibration spectrum I CM The peak position λ of the Raman peak P in (λ) P (T CM ) and the previously determined relationship between the peak position of the Raman peak associated with the Raman band exhibited by the additional material and the temperature of the calibration material CM to determine the temperature T of the calibration material CM CM (λ).

[0084] In some embodiments, the relationship is based, for example, on the emission spectra E determined for different temperatures Ti in method step A2. Ti In such an embodiment, method 200 includes, for example, determining the relationship based on the emission spectrum ETi The Raman peak ρ included in (λ) Ti The peak position λp(Ti) and the emission spectrum E Ti (λ) is determined by the corresponding temperature Ti of the calibration material CM which has been determined.

[0085] As an alternative, the relationship is determined in the same way, for example based on the emission spectra emitted by the additional material at different temperatures.

[0086] The temperature T of the calibration material CM is determined based on the peak position λp(Ti) of the Raman peak P CM The additional material included in the calibration material CM is particularly suitable in embodiments in which it exhibits a single and / or narrow Raman band within the spectral measurement range Δλ of the Raman spectrometer 100 to be calibrated. Additionally or alternatively, the additional material is, for example, a material that exhibits a high temperature dependence of the peak position. Such a high temperature dependence of the peak position provides the advantage of enabling a temperature determination with a higher measurement accuracy.

[0087] exist Figure 5 and Figure 6 In the depicted embodiment, the measurement range Δλ covers the Stokes region corresponding to wavelengths exceeding the excitation wavelength λ0. Accordingly, the emission spectrum E Ti The Raman peak P included in (λ) Ti and calibration spectrum I CM The Raman peak P included in (λ) corresponds to the Stokes Raman peak associated with the Raman band. The Stokes Raman peak exhibits a higher intensity than the corresponding anti-Stokes Raman peak over a wide temperature range. Therefore, even though the peak intensity of the Stokes Raman peak decreases with increasing temperature, the Stokes Raman peak is used to determine the temperature T of the calibration material CM. CM Rather than the corresponding anti-Stokes Raman peak, it provides the following advantages: CM The Raman peaks P included in (λ) can be easily identified, making their peak positions λp(T CM ) can be accurately determined and the temperature T of the calibration material CM CM It can be accurately determined over a wide temperature range.

[0088] In some embodiments, the Raman spectrometer 100 to be calibrated includes, for example, at least one dual-range spectrometer capable of determining an intensity spectrum I(λ) within a range, the range comprising a spectral measurement range Δλ covering the Stokes region of the Raman spectrum, which includes spectral lines corresponding to wavelengths longer than the excitation wavelength λ0, and an additional range covering the anti-Stokes region of the Raman spectrum, which includes spectral lines corresponding to wavelengths shorter than the excitation wavelength λ0.

[0089] In such an embodiment, the method 200 comprises, for example, determining, for at least one or each dual-range spectrometer, the temperature T of the calibration material CM by determining, based on the ratio of the temperature dependencies of the Stokes and anti-Stokes signal intensities of different Raman bands of the additional material, CM To perform method step A4.

[0090] In such an embodiment, the emission spectra E of the calibration material CM at the different temperatures Ti determined in method step A2 are Ti (λ) and the calibration spectrum I of the calibration material CM determined in method step A3 CM (λ) is determined, for example, in each case in a spectral range comprising the spectral measurement range Δλ and the additional range Δλ2.

[0091] like Figure 7 The diagram shows exemplary emission spectra E of the same calibration material CM at different temperatures Ti. Ti (λ), in this example, the different Raman bands associated with the additional material result in an emission spectrum E Ti (λ), each emission spectrum includes the Stokes Raman peak PS Ti , which is superimposed on the temperature-dependent broadband emission spectrum of the reference material in the measurement range Δλ, and the corresponding anti-Stokes Raman peak PS Ti Occurs in the additional range Δλ2.

[0092] Similarly, if Figure 8 As shown in the figure, it shows Figure 7 The emission spectrum shown in Ti Calibration spectrum of the calibration material CM of (λ) CM Example of (λ), calibration spectrum I determined in method step A3 CM (λ) exhibits a Stokes Raman peak PS superimposed on the temperature-dependent broadband emission spectrum of the reference material in the measurement range Δλ and a corresponding anti-Stokes Raman peak PA appearing in the additional range Δλ2.

[0093] As in the previous example, Figure 7 The exemplary emission spectrum E shown in Ti (λ) includes a first emission spectrum E determined at a first temperature T1 T1 (λ), the second emission spectrum E determined at the second temperature T2 T2 (λ), and a third emission spectrum E determined at a third temperature T3 T3 (λ), wherein the second temperature T2 is higher than the first temperature T1 and the third temperature T3 is higher than the second temperature T2. Likewise, the different temperatures Ti for example cover a predetermined temperature range, for example a temperature range of 10°C to 50°C or for example -20°C to 100°C.

[0094] from Figure 7 The emission spectrum E shown in Ti (λ) Obviously, Stokes peak PS Ti The peak intensity Ips(λ) decreases with the increase of temperature Ti, and the anti-Stokes peak PA Ti The peak intensity Ipa(Ti) increases with the increase of temperature Ti.

[0095] Accordingly, in certain embodiments, for at least one of the dual-range spectrometers, method step A4 comprises, for example, determining a calibration spectrum I within the measurement range Δλ. CM The peak intensity Ips of the Stokes Raman peak PS included in (λ) is related to the calibration spectrum I in the additional range Δλ2 CM The ratio of the peak intensity Ipa of the anti-Stokes Raman peak PA included in (λ). After this determination, the peak intensity Ips of the Stokes Raman peak PS is then compared to the calibration spectrum I CM The temperature T of the calibration material CM is determined based on the previously determined relationship between the ratio of the peak intensity of the Stokes Raman peak to the anti-Stokes Raman peak and the temperature of the calibration material CM. CM .

[0096] In certain embodiments, the relationship between the ratio of the peak intensities of the Stokes Raman peak and the anti-Stokes Raman peak and the temperature of the calibration material CM is based on, for example, the emission spectrum E covering the measurement range Δλ. Ti (λ) and the additional range Δλi determined in method step A2 for different temperatures Ti. In such an embodiment, method 200 comprises, for example, based on the Stokes peak PS Ti The peak intensity Ips(Ti) and the emission spectrum E Ti The corresponding anti-Stokes peak PA included in (λ) Ti The ratio of the peak intensity Ipa(Ti) and the emission spectrum E have been determined Ti The relationship is determined by the corresponding temperature Ti of the calibration material CM of (λ).

[0097] Regardless of the determination of the temperature T of the calibration material CM carried out in method step A4 CM In method step A5, based on the calibration spectrum I determined in method step A3, CM (λ), the temperature T of the calibration material CM determined in method step A4 CM and the emission spectrum E determined in method step A2 Ti(λ) is used to adjust the determination of the intensity values ​​of the intensity spectrum I(λ) to be calibrated, which is performed by the Raman spectrometer 100 .

[0098] In some embodiments, method step A5 comprises, for example, based on the emission spectrum E Ti (λ), determined by the calibration material based on the calibration I CM (λ) Determined temperature T CM The reference spectrum R Tcm (λ). The corresponding reference spectrum R Tcm An example of (λ) is Figure 6 Shown in.

[0099] The emission spectrum E determined in method step A2 Ti (λ) includes the temperature T CM Determine the emission spectrum E Ti (λ), the emission spectrum E Ti (λ) is used as the reference spectrum. Under all other conditions, the reference spectrum R Tcm (λ) For example, by using the emission spectrum E determined previously Ti is determined by interpolating at least two of (λ).

[0100] Subsequently, the calibration spectrum I is obtained by determining and applying a spectral correction term, a spectral correction factor, or a spectral correction function for correcting the spectral intensity values ​​determined by the Raman spectrometer 100. CM The corrected spectral intensity value of (λ) corresponds to the reference spectrum R in the entire spectral measurement range Δλ Tcm The spectral intensity value of (λ) is as follows: Figure 6 As illustrated by the arrows shown in , for example, a determination of the intensity values ​​of the intensity spectrum U(λ) performed by the Raman spectrometer 100 to be calibrated is performed.

[0101] After such an adjustment, the intensity spectrum I(λ) determined and provided by the thus calibrated Raman spectrometer 100 is then replaced by the correspondingly corrected intensity spectrum I cor (λ) is given.

[0102] In some embodiments, the same calibration material CM is used, for example, to calibrate a plurality of Raman spectrometers 100 comprising light sources 1 generating monochromatic light of the same desired excitation wavelength λ0. Such use of the calibration material CM provides the following advantages: Ti (λ) and is used to determine the temperature T of the calibration material CM during each of these calibrations CM The relationship mv only needs to be determined once; and at least one model for determining the measured value mv of the measured object can be used on each such calibrated Raman spectrometer 100 .

Claims

1. A method for calibrating at least one Raman spectrometer (100), the at least one Raman spectrometer comprising: A monochromatic light source (1) configured to transmit excitation light (L0) having a desired excitation wavelength (λ0) to a measurement area (3), the measurement area (3) configured to accommodate a sample (S) of a medium and to illuminate the sample (S) of the medium with the excitation light (L0); and a spectrometry unit (7) configured to receive measurement light (LR) emitted from the illuminated sample (S) and to determine and provide an intensity spectrum (I(λ)) of the received measurement light (LR) in a spectral measurement range (Δλ), the method comprising: Providing a calibration material (CM), the calibration material (CM) comprising: a reference material configured to emit a broadband spectrum of luminescence light in response to the excitation light (L0); and an additional material, the additional material exhibiting a different Raman band within the spectral measurement range (Δλ) of at least one Raman spectrometer (100) to be calibrated; For at least two different temperatures (Ti), in response to receiving the calibration material (CM) with excitation light having an excitation wavelength (λ0), determining an emission spectrum (E ) of light emitted by the calibration material (CM) at each respective temperature (Ti) Ti (λ)); and Each of the at least one Raman spectrometer (100) is calibrated by: Using a corresponding Raman spectrometer (100), the calibration spectrum (I CM (λ)); Based on the calibration spectrum (I CM (λ)), determining the temperature (T) of the calibration material (CM) by performing Raman thermometry CM );as well as adjusting the determination of spectral intensity values ​​of an intensity spectrum (I(λ)) performed by a corresponding Raman spectrometer (100), wherein the adjustment is based on the calibration spectrum (I CM (λ)), the calibration spectrum (I CM The temperature (T) of the calibration material (CM) during the determination of (λ) CM ), and the previously determined emission spectrum (E Ti (λ)).

2. The method according to claim 1, wherein: Providing the calibration material (CM) comprises manufacturing the calibration material by melting the reference material and distributing a powder of the additional material in the molten reference material.

3. The method according to claim 1, wherein: Providing the calibration material (CM) comprises manufacturing the calibration material (CM) by the following steps: applying at least one layer of said additional material to an outer surface of said reference material; or At least one layer (17) of the additional material is deposited onto the outer surface of the reference material (19) using a deposition process, a low temperature deposition process, or a vacuum deposition process.

4. The method according to claims 1 to 3, wherein: For the at least one Raman spectrometer (100), based on the calibration spectrum (I CM (λ)) is determined by the following operation: CM ): Determine the calibration spectrum (I CM The peak position (λ) of the Raman peak (P) associated with the Raman band of the additional material included in (λ) P (T CM )); as well as Based on the peak position (λ P (T CM )) and a previously determined relationship between the peak position of the Raman peak associated with the Raman band exhibited by the additional material and the temperature of the calibration material (CM) CM ).

5. The method according to claim 4, further comprising: Based on the emission spectrum (E Ti The Raman peak (P Ti ) and the emission spectrum thereof (E Ti The relationship between the peak position of a Raman peak associated with a Raman band exhibited by the additional material and the temperature (Ti) of the calibration material (CM) for which the temperature (λ) has been determined is determined.

6. The method according to claims 4 to 5, wherein: The Raman peak (P) is a Stokes peak occurring in the spectrum measurement range (Δλ) of the at least one Raman spectrometer (100).

7. The method according to claims 1 to 6, wherein: The at least one Raman spectrometer (100) comprises at least one dual-range spectrometer, the at least one dual-range spectrometer being configured to determine an intensity spectrum (I(λ)) within a range including the spectrum measurement range (Δλ) and an additional range (Δλ2), wherein the spectrum measurement range (Δλ) is a range covering a Stokes region including spectrum lines corresponding to wavelengths longer than the excitation wavelength (λ0), and wherein the additional range (Δλ2) is a range covering an anti-Stokes region including spectrum lines corresponding to wavelengths shorter than the excitation wavelength (λ0); The emission spectrum (E Ti (λ)) are each determined within a spectral range comprising said spectral measurement range (Δλ) and said additional range (Δλ2); as well as For each of the at least one dual-range spectrometer: The calibration spectrum (I 2 ) of the calibration material (CM) is determined within the spectral range comprising the spectral measurement range (Δλ) and the additional range (Δλ2). CM (λ)); and Based on the calibration spectrum (I CM (λ)) is determined by the following operation: CM ): Determine the calibration spectrum (I CM The peak intensity (Ips) of the Stokes Raman peak (PS) included in (λ) is consistent with the calibration spectrum (I CM (λ)), wherein both the Stokes Raman peak (PS) and the Anti-Stokes Raman peak (PA) are associated with the Raman band of the additional material; and Based on the calibration spectrum (I CM The peak intensity (Ips) of the Stokes Raman peak (PS) included in (λ) is consistent with the calibration spectrum (I CM The temperature (T of the calibration material (CM) is determined by a previously determined relationship between the ratio of the peak intensities (Ipa) of the anti-Stokes Raman peak (PA) included in (λ) and the ratio of the peak intensities of the Stokes Raman peak and the anti-Stokes Raman peak associated with the Raman band and the temperature of the calibration material (CM). CM ).

8. The method according to claim 7, further comprising: Based on the emission spectrum (E Ti The Stokes Raman peak (PS Ti ) and the corresponding anti-Stokes Raman peak (PA Ti ) and the peak intensity (Ips(Ti), Ipa(Ti)) of the emission spectrum thereof. Ti (λ)) and a temperature (Ti) of a calibration material (CM) for which the temperature (λ) has been determined, determining a relationship between a ratio of peak intensities of Stokes Raman peaks and anti-Stokes Raman peaks associated with said Raman band and the temperature of said calibration material (CM).

9. The method according to claims 1 to 8, wherein: Adjusting the determination of spectral intensity values ​​of an intensity spectrum (I(λ)) performed by the at least one Raman spectrometer (100) comprises: Based on the emission spectrum (E Ti (λ)), determined by the calibration material (CM) based on the calibration spectrum (I CM (λ)) to determine the temperature (T CM ) under the reference spectrum (R Tcm (λ)); and Determining and applying a spectral correction term, a spectral correction factor or a spectral correction function for correcting the spectral intensity values ​​determined by the at least one Raman spectrometer (100) so that the calibration spectrum (I CM The corrected spectral intensity value of (λ)) corresponds to the reference spectrum (R Tcm (λ)) of the spectral intensity value.

10. The method according to claims 1 to 9, wherein: The emission spectrum (E Ti The at least two different temperatures (Ti) of (λ)) cover a predetermined temperature range of -20°C to 100°C or a predetermined temperature range of 10°C to 50°C.

11. A calibration material (CM) for calibrating the spectral responsivity of at least one Raman spectrometer (100), the calibration material (CM) comprising: a reference material configured to emit a broadband spectrum of luminescence light in response to the reference material receiving excitation light (L0) having a desired excitation wavelength (λ0); as well as An additional material exhibits a different Raman band within a spectral measurement range (Δλ) of at least one Raman spectrometer (100) to be calibrated.

12. The calibration material (CM) according to claim 11, wherein The reference material is a standard reference material (SRM) or fluorescent glass.

13. The calibration material (CM) according to claims 11 to 12, wherein The additional material is carbon, diamond, sapphire, silicon, calcium fluoride (CaF2) or lithium niobate (LiNbO3).

14. Calibration material (CM) according to claims 11 to 13, wherein The additional material is a material that exhibits at least one of the following: a single Raman band within the spectral measurement range (Δλ) of the at least one Raman spectrometer (100); a narrow Raman band within the spectral measurement range (Δλ) of the at least one Raman spectrometer (100); and Exhibiting a Raman peak having a full width at half maximum that is less than or equal to a given percentage of the width of the spectral measurement range (Δλ), wherein the given percentage is 10% or the given percentage is 1%.

15. Calibration material (CM) according to claims 11 to 14, wherein: The additional material is distributed throughout the reference material; or At least one layer (17) of the additional material covers the outer surface of the reference material (19).

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