CN115372270A - Spectrum integration correction method and multispectral spectrometer - Google Patents

Abstract

The invention provides a spectrum integration correction method and a multispectral spectrometer, wherein the spectrum integration correction method comprises the following steps: providing a multi-spectral spectrometer, wherein the multi-spectral spectrometer comprises a plurality of sub-spectrometers for respectively measuring a plurality of sub-spectra with different wavelength ranges; measuring the spectrum of at least one wavelength correction piece by using a multi-spectral spectrometer, and respectively correcting the detection wavelengths of the sub-spectrometers by using a plurality of known characteristic wavelengths of the spectrum of the at least one wavelength correction piece; and measuring the spectrum of the at least one standard reflector by using the multi-spectrum spectrometer, and obtaining the spectral intensity equivalent of each of the sub-spectrometers by using the known reflectivity of the at least one standard reflector.

Description

Spectrum integration correction method and multispectral spectrometer

Technical Field

The present invention relates to an optical calibration method and a spectrometer, and more particularly, to a spectrum integration calibration method and a multispectral spectrometer.

Background

For a spectrometer using a single photodetector, the wavelength sensing range of the spectrometer is limited due to the material of the photodetector, and the spectrometer cannot widely sense various wavelengths. Therefore, a spectrometer with multiple different photodetectors may be used to sense different wavelength ranges, respectively.

The use of multiple different photodetectors to sense different wavelength ranges can result in multiple spectra of different wavelength ranges, which are difficult to integrate into one spectrum. First, the spectral responses of different photodetectors are different, and thus if the two spectra are combined together, there is a problem that quantitative integration is impossible. In addition, when the switching optical path control mirror is used to switch the detection of different photodetectors, the real-time (real-time) monitoring of the object to be detected is not possible to achieve the real-time distribution of the spectrum input signal.

Disclosure of Invention

The present invention is directed to a spectrum integration calibration method that calibrates a spectrometer to well integrate multiple sub-spectra.

The present invention is directed to a multi-spectral spectrometer that integrates sub-spectra well into one spectrum.

An embodiment of the present invention provides a spectrum integration correction method, including: providing a multi-spectral spectrometer, wherein the multi-spectral spectrometer comprises a plurality of sub-spectrometers for respectively measuring a plurality of sub-spectra with different wavelength ranges; measuring the spectrum of at least one wavelength correction piece by using a multi-spectral spectrometer, and respectively correcting the detection wavelengths of the sub-spectrometers by using a plurality of known characteristic wavelengths of the spectrum of the at least one wavelength correction piece; and measuring the spectrum of the at least one standard reflecting member by using the multi-spectrum spectrometer, and obtaining the respective spectral intensity equivalent of the sub-spectrometers by using the known reflectivity of the at least one standard reflecting member.

An embodiment of the present invention provides a multi-spectral spectrometer for measuring a spectrum of an object to be measured. The multispectral spectrometer comprises a light source, a light splitting element, a plurality of sub-spectrometers and a controller. The light source is used for providing an illuminating light beam to irradiate the object to be measured, wherein the object to be measured reflects the illuminating light beam into signal light. The light splitting element is disposed on a path of the signal light and splits the signal light into a plurality of sub-beams. The sub-spectrometers are respectively configured on the transmission paths of the sub-beams to measure a plurality of sub-spectra with different wavelength ranges. The controller is electrically connected to the sub-spectrometers for converting the sub-spectra into the same spectral intensity equivalent and integrating the converted sub-spectra into a single spectrum.

In the spectrum integration correction method according to the embodiment of the invention, since the wavelengths of the plurality of sub-spectrometers and the spectral intensity equivalents of the plurality of obtained sub-spectra are corrected by the wavelength corrector and the standard reflector, the multi-spectral spectrometer can be adjusted to well integrate the plurality of sub-spectra. In the multispectral spectrometer according to the embodiment of the invention, since the controller converts the sub-spectra into the same spectral intensity equivalent and integrates the sub-spectra into one spectrum, the sub-spectra can be well integrated into one spectrum.

Drawings

FIG. 1 is a schematic cross-sectional view of a multi-spectral spectrometer according to an embodiment of the invention.

Fig. 2 is a flowchart of a spectrum integration correction method according to an embodiment of the invention.

Fig. 3 is an absorption spectrum diagram of the wavelength correcting element of fig. 1.

Fig. 4A and 4B are reflection sub-spectra of the local reflector measured by two sub-spectrometers of the multi-spectrometer of fig. 1, respectively.

Fig. 5A, 5B, 5C and 5D are reflection spectra of the first standard reflector, the second standard reflector, the third standard reflector and the fourth standard reflector in the embodiment of fig. 2, respectively.

FIG. 6 is an integrated spectrum obtained when the sample is measured by the multispectral spectrometer of FIG. 1 calibrated by the spectrum integration calibration method of FIG. 2.

Detailed Description

Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.

FIG. 1 is a schematic cross-sectional view of a multi-spectral spectrometer according to an embodiment of the invention. Referring to fig. 1, the multispectral spectrometer 100 of the present embodiment is used for measuring a spectrum of the object 50. The multispectral spectrometer 100 comprises at least one light source 110 (two light sources 110 are illustrated in fig. 1, but the invention is not limited thereto), a light splitting element 121, a plurality of sub-spectrometers 130 and a controller 140. The light source 110 is used for providing an illumination beam 112 to illuminate the object 50, and the object 50 reflects the illumination beam 112 into the signal light 52. In the present embodiment, the light source 110 is, for example, a tungsten lamp, a halogen lamp, other blackbody radiation source, or other suitable light source with a continuous spectrum.

The optical splitter 121 is disposed on the path of the signal beam 52 and splits the signal beam 52 into a plurality of sub-beams 53. In this embodiment, the multispectral spectrometer 100 further includes a Y-fiber 120, and the light splitting element 121 is the light input end of the Y-fiber 120. The Y-fiber 120 includes at least two sub-fibers 122, which sub-fibers 122 are close together at one end (i.e., the end where the light splitting element 121 is located in fig. 1) and are separated at the other end. The signal light 52 from the object 50 is irradiated to one end of the sub-fibers 122 and enters the sub-fibers 122 respectively.

The sub-spectrometers 130 are respectively disposed on the transmission paths of the sub-beams 53 to measure a plurality of sub-spectra with different wavelength ranges. In the present embodiment, the sub-fibers 122 are respectively connected to different sub-spectrometers 130, so that the sub-spectrometers 130 can respectively measure the sub-beams 53.

In another embodiment, the light splitting element 121 may also be a beam splitter or a beam splitter prism to split the signal light 52 into two sub-beams 53, and the two sub-beams 53 are transmitted to the two sub-spectrometers 130 via two optical fibers, respectively.

In this embodiment, the controller 140 is electrically connected to the sub-spectrometers 130 for converting the sub-spectra into the same spectral intensity equivalent and integrating the converted sub-spectra into a single spectrum. In an embodiment, the controller 140 is, for example, a Central Processing Unit (CPU), a microprocessor (microprocessor), a Digital Signal Processor (DSP), a programmable controller, a Programmable Logic Device (PLD), or other similar devices or combinations thereof, which are not limited in the present invention. Furthermore, in one embodiment, the functions of the controller 140 may be implemented as a plurality of program codes. The program codes are stored in a memory and executed by the controller 140. Alternatively, in one embodiment, the functions of the controller 140 may be implemented as one or more circuits. The present invention is not limited to the implementation of the functions of the controller 140 in software or hardware.

In the multispectral spectrometer 100 of the present embodiment, the controller 140 converts the sub-spectra into the same spectral intensity equivalent and integrates the converted sub-spectra into one spectrum, so that the sub-spectra can be integrated into one spectrum well. Thus, it is helpful for the user to easily determine the characteristics of the object 50 from a single spectrum with a wide wavelength range.

In the present embodiment, the multispectral spectrometer 100 further includes a semi-integrating sphere 150 for covering the object 50 to be measured, wherein the light source 110 and the light splitting element 121 are disposed on a spherical shell of the semi-integrating sphere 150. In addition, in the present embodiment, the multispectral spectrometer further includes a collimating lens 160 disposed on the spherical shell of the half-integrating sphere 150, wherein the collimating lens 160 is configured to transmit the signal beam 52 to the light splitting element 121 in a collimated manner, and to distribute the signal beam 52 to different sub-optical fibers 122 as evenly as possible.

The following description will describe how the multi-spectral spectrometer 100 is calibrated to be a spectrum integration calibration method that can integrate a plurality of sub-spectra into one spectrum well.

Fig. 2 is a flowchart of a spectrum integration correction method according to an embodiment of the invention. Referring to fig. 1 and 2, the spectrum integration correction method of the present embodiment can be used to correct the multispectral spectrometer 100 of fig. 1 and various possible variations thereof. The spectrum integration correction method comprises the following steps. First, step S110 is executed to provide the multi-spectral spectrometer 100, where the multi-spectral spectrometer 100 includes a plurality of sub-spectrometers 130 for measuring sub-spectra of different wavelength ranges, respectively. Next, step S120 is executed to measure the spectrum of the at least one wavelength calibration member 60 by using the multispectral spectrometer 100, and respectively calibrate the detection wavelengths of the sub-spectrometers 130 by using a plurality of known characteristic wavelengths of the spectrum of the at least one wavelength calibration member 60. The wavelength calibration member 60 can be placed at the position of the object 50 to replace the object 50, and the sub-spectrometers can measure the spectrum of the wavelength calibration member 60.

Fig. 3 is an absorption spectrum diagram of the wavelength correcting element 60 of fig. 1. Referring to fig. 1 to 3, the wavelength calibration component 60 is a standard component, and its characteristic wavelength is known, and the characteristic wavelength is, for example, the wavelength of the peak of the absorption spectrum or the wavelength of the trough of the reflection spectrum. The sub-spectrometers 130 measure, for example, the reflectance spectrum directly, but the reflectance spectrum may simply be converted to an absorption spectrum by the controller 140, for example, by subtracting the intensity of the reflectance spectrum at each wavelength from a normalized or higher value. The characteristic wavelength can be seen from the absorption spectrum and also from the reflection spectrum. When a pixel of the image sensor (e.g., a one-dimensional or two-dimensional sensing array) of the sub-spectrometer 130 senses a trough (when corrected by using the reflection spectrum) or a peak (when corrected by using the absorption spectrum) of the characteristic wavelength, the pixel position can be defined as the position of the characteristic wavelength in the spectrum, so that the horizontal axis (i.e., wavelength) of the spectrum can be corrected.

In this embodiment, the correcting the detection wavelengths of the sub-spectrometers 130 further includes performing a numerical interpolation calculation according to the known characteristic wavelengths, and correcting the detection wavelengths of the sub-spectrometers 130 by using the calculated numerical values, so that the wavelength scales of the sub-spectrometers 130 are consistent. In this way, the scales (i.e. the scales of the wavelengths) of the horizontal axes of the different sub-spectrometers 130 can be uniform, so that the sub-spectrums can be integrated into a single spectrum in the future, and the wavelength scales are uniform from the short wavelength to the long wavelength.

In one embodiment, a plurality of different wavelength correction elements 60 may be used to correct different bands of wavelengths. For example, the at least one wavelength calibration element 60 includes a first wavelength calibration element and a second wavelength calibration element, and the maximum characteristic wavelength of the first wavelength calibration element is greater than the maximum characteristic wavelength of the second wavelength calibration element. The first wavelength correcting element can be used for correcting the wavelength in the wavelength band with longer wavelength, and the second wavelength correcting element can be used for correcting the wavelength in the wavelength band with shorter wavelength. The material of the first wavelength calibration member may include oily organic matter, and the material of the second wavelength calibration member may include rare earth metal, but the invention is not limited to the material of the first wavelength calibration member and the second wavelength calibration member, and any standard member formed of a material having a characteristic wavelength within the detection range of the multispectral spectrometer 100 may be used as the wavelength calibration member 60. The calibration standard of the wavelength corrector 60 can be traced back to the NIST standard known to those having ordinary skill in the art, wherein the NIST is entitled "National Institute of Standards and Technology".

Then, step S130 is performed, the multi-spectral spectrometer 100 measures the spectrum of at least one standard reflector 70, and the known reflectivity of at least one standard reflector 70 is used to obtain the spectral intensity equivalent of each of the sub-spectrometers 130. FIGS. 4A and 4B are reflectance sub-spectra of a native reflector measured by two sub-spectrometers of the multi-spectrometer of FIG. 1, respectively. As can be seen from fig. 4A and 4B, the scale sizes of the spectrum intensities on the vertical axis are different, except for the wavelength ranges of the two sub-spectra. At this time, if the two sub-spectra are hard to put together, a continuous spectrum from 900 nm to 2400 nm cannot be formed, but rather a strange and abnormal spectral shape with a step difference in the middle and a spectral intensity that is much smaller after about 1600 nm and almost invisible is formed. In this case, the sub-spectrometers 130 can measure the standard reflector 70, and the reflectivity of the standard reflector 70 at each wavelength is known, so that the spectral intensities of both sub-spectra can be adjusted to the same equivalent. For example, the spectral intensity of at least one of the two sub-spectra may be multiplied by a suitable factor, e.g. the spectral intensities of the two sub-spectra corresponding to 99% reflectivity of the standard reflector 70 should be identical, so that the two spectral intensities are adjusted to be identical, i.e. to be equal in spectral intensity equivalence, by multiplying at least one of the two spectral intensities by a suitable factor. In one embodiment, the standard reflector 70 is made of metal, for example, but the invention is not limited thereto.

Fig. 5A, 5B, 5C and 5D are reflection spectra of the first standard reflector, the second standard reflector, the third standard reflector and the fourth standard reflector in the embodiment of fig. 2, respectively. Referring to fig. 1, 2 and 5A to 5D, the at least one standard reflector 70 includes a first standard reflector and a second standard reflector, and a reflectivity of the first standard reflector is greater than a reflectivity of the second standard reflector. The spectrum integration correction method further comprises the step of calculating the spectrum intensity corresponding to the reflectivity of one hundred percent according to the known reflectivity of the first standard reflector, and calculating the spectrum intensity corresponding to the reflectivity of zero according to the known reflectivity of the second standard reflector. Specifically, in the reflection spectrum of the first standard reflector in fig. 5A, the reflectance of the plateau region is about 0.99, so when the sub-spectrometer 130 measures the spectrum with the plateau region, the spectral intensity of the plateau region can be regarded as the reflectance of 0.99, and the spectral intensity corresponding to the reflectance of 1 can be linearly calculated, for example, the spectral intensity of the plateau region is divided by 0.99 and then multiplied by 1 to obtain the spectral intensity corresponding to the reflectance of 1.

On the other hand, the reflectance of the second standard reflector is about 0.02, so the intensity of the reflection spectrum of the second standard reflector measured in the sub-spectrometer 130 can be regarded as 0.02, and then the intensity of the spectrum corresponding to the reflectance of 0 is linearly calculated, so that the intensity position of the absolute return-to-zero baseline of the sub-spectrometer 130 can be corrected, and the background value of the dark noise return-to-zero is corrected.

In this embodiment, the at least one standard reflector 70 may further include a third standard reflector, the reflectivity of the third standard reflector is between the reflectivity of the first standard reflector and the reflectivity of the second standard reflector, and the spectrum integration correction method further includes calculating the spectrum intensity corresponding to the reflectivity as an intermediate value according to the known reflectivity of the third standard reflector, wherein the intermediate value is between 0 and one hundred percent. For example, the reflectivity of the third standard reflection element varies from about 0.72 to 0.86 with the wavelength, so the intensity of the spectral signal of the third standard reflection element measured by the sub-spectrometer 130 can be regarded as from 0.72 to 0.86 respectively according to the corresponding wavelength, and then the position of the scale mark with the reflectivity of 0.75 can be linearly calculated.

Similarly, the at least one standard reflecting element 70 may further include a fourth standard reflecting element, and the reflectivity of the fourth standard reflecting element varies from about 0.48 to about 0.56 with the variation of the wavelength, so that the intensity of the spectral signal of the third standard reflecting element measured by the sub-spectrometer 130 according to the variation of the corresponding wavelength can be regarded as 0.48 to 0.56, and then the position of the scale mark with the reflectivity of 0.5 can be linearly calculated.

The number of the standard reflecting members 70 is not limited, and the longitudinal axis (i.e., the reflectivity) can be corrected more accurately when the number is larger. After the reflectance of the standard reflecting member 70 is corrected, the spectral intensity corresponding to each scale of the reflectance from 0 to 1, that is, each scale from 0 to 1 is corrected, can be estimated by interpolation or extrapolation. In addition, since the spectral response intensity of the image sensor of the sub-spectrometer 130 and the actual reflectance may show nonlinear changes, and the image sensors of different sub-spectrometers 130 may show different nonlinear changes due to different materials, the use of a larger number of standard reflectors 70 with different reflectances (e.g., the third standard reflector corresponding to fig. 5C or the fourth standard reflector corresponding to fig. 5D, which has a reflectivity closer to the middle level) helps to correct these nonlinear changes, so that the interpolation or extrapolation can be more accurately used to calculate the spectral intensity corresponding to each scale with a reflectivity from 0 to 1. This allows the absolute quantitative change in the sensitivity of the test sample signal to be confirmed.

The calibration standard of the standard reflector 70 conforms to the NIST standard and NVLAP calibration (NVLAP calibration) standard, which are well known to those of ordinary skill in the art, wherein the NVLAP is known under the full name of "National volume Laboratory access Program".

Then, step S140 is executed to convert the sub-spectra respectively measured by the sub-spectrometers 130 into the same spectral intensity equivalent according to the respective spectral intensity equivalent of the sub-spectrometers 130 and integrate the converted sub-spectra. That is, the plurality of sub-spectra are combined into a single spectrum according to the reflectivity corrected in step S130 with the same reflectivity scale, and the single spectrum is a complete good spectrum from short wavelength to long wavelength.

FIG. 6 is an integrated spectrum obtained when the sample is measured by the multispectral spectrometer of FIG. 1 calibrated by the spectrum integration calibration method of FIG. 2. As can be seen from fig. 6, the integrated spectrum obtained by the multispectral spectrometer 100 of fig. 1 is a good spectrum from short wavelength to long wavelength, and the multispectral spectrometer 100 can output a calibration report accordingly. In addition, the multispectral spectrometer 100 may store the above-mentioned correction values in an internal memory or transmit the correction values to a server for reference. Such a sample may also be used to be measured by other multispectral spectrometers 100 to obtain a spectrum from which it can be quickly determined whether the other multispectral spectrometers are well calibrated.

In addition, the wavelength and reflectivity data corrected in steps S120 and S130 of fig. 2 may be stored in the storage through the controller 140, and after the multispectral spectrometer 100 leaves the factory, the data stored in the storage can be directly used to execute step S140, so that the controller 140 converts a plurality of sub-spectra into the same spectral intensity equivalent and then integrates the same into a single spectrum with a wider wavelength range and good quality.

In summary, in the spectrum integration correction method according to the embodiment of the invention, the wavelength correction element and the standard reflection element are used to correct the wavelengths of the plurality of sub-spectrometers and the spectral intensity equivalents of the obtained plurality of sub-spectra, so that the multi-spectral spectrometer can be calibrated to well integrate the plurality of sub-spectra. In the multispectral spectrometer according to an embodiment of the present invention, the controller converts the sub-spectra into the same spectral intensity equivalent and integrates the converted sub-spectra into one spectrum, so that the sub-spectra can be integrated into one spectrum well.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A method for integrated spectrum correction, comprising:

providing a multi-spectral spectrometer, wherein the multi-spectral spectrometer comprises a plurality of sub-spectrometers for respectively measuring a plurality of sub-spectra with different wavelength ranges;

measuring the spectrum of at least one wavelength correcting piece by using the multispectral spectrometer, and respectively correcting the detection wavelengths of the sub-spectrometers by using a plurality of known characteristic wavelengths of the spectrum of the at least one wavelength correcting piece; and

the spectrum of at least one standard reflector is measured by the multi-spectrum spectrometer, and the spectral intensity equivalent of each of the sub-spectrometers is obtained by the known reflectivity of the at least one standard reflector.

2. The method as claimed in claim 1, wherein the calibrating the detection wavelengths of the sub-spectrometers further comprises performing a numerical interpolation calculation based on the known characteristic wavelengths, and calibrating the detection wavelengths of the sub-spectrometers by using the calculated numerical values, so that the wavelength scales of the sub-spectrometers are consistent.

3. The method of claim 1, further comprising converting the plurality of sub-spectra measured by the plurality of sub-spectrometers into the same spectral intensity equivalent according to the respective spectral intensity equivalents of the plurality of sub-spectrometers.

4. The method according to claim 1, wherein the at least one standard reflector comprises a first standard reflector and a second standard reflector, the reflectivity of the first standard reflector is greater than the reflectivity of the second standard reflector, and the method further comprises calculating a spectral intensity corresponding to a reflectivity of one hundred percent based on the known reflectivity of the first standard reflector, and calculating a spectral intensity corresponding to a reflectivity of zero based on the known reflectivity of the second standard reflector.

5. The method according to claim 4, wherein the at least one standard reflector further comprises a third standard reflector having a reflectivity between the reflectivity of the first standard reflector and the reflectivity of the second standard reflector, and the method further comprises calculating a spectral intensity corresponding to a reflectivity of an intermediate value according to the known reflectivity of the third standard reflector, wherein the intermediate value is between 0 and one hundred percent.

6. The method according to claim 1, wherein the at least one wavelength calibration element comprises a first wavelength calibration element and a second wavelength calibration element, and a maximum characteristic wavelength of the first wavelength calibration element is greater than a maximum characteristic wavelength of the second wavelength calibration element.

7. A multi-spectral spectrometer for measuring a spectrum of an object, the multi-spectral spectrometer comprising:

the light source is used for providing an illuminating light beam to irradiate the object to be measured, wherein the object to be measured reflects the illuminating light beam into signal light;

a light splitting element disposed on a path of the signal light and splitting the signal light into a plurality of sub-beams;

the plurality of sub-spectrometers are respectively configured on the transmission paths of the plurality of sub-beams to measure a plurality of sub-spectra with different wavelength ranges; and

and the controller is electrically connected to the plurality of sub-spectrometers and is used for converting the plurality of sub-spectrums into the same spectrum intensity equivalent and integrating the plurality of sub-spectrums into one spectrum.

8. The multispectral spectrometer according to claim 7, further comprising a semi-integrating sphere for covering the object, wherein the light source and the light splitting element are disposed on a spherical shell of the semi-integrating sphere.

9. The multispectral spectrometer of claim 8, further comprising a collimating lens disposed on the spherical shell of the semi-integrating sphere, wherein the collimating lens is configured to transmit the signal light to the light splitting element in a collimated manner.

10. The multispectral spectrometer of claim 9, wherein the light splitting element is an input end of a Y-fiber.

Images