TWI793609B - Spectrum integration calibration method and multi-spectrum spectrometer - Google Patents

Abstract

A spectrum integration calibration method includes: providing a multi-spectrum spectrometer including a plurality of sub-spectrometers configured to respectively measure a plurality of sub-spectra in different wavelength ranges; measuring a spectrum of at least one wavelength calibrator by the multi-spectrum spectrometer and respectively calibrating detecting wavelengths of the sub-spectrometers by a plurality of known feature wavelengths of the spectrum of the at least one wavelength calibrator; and measuring a spectrum of at least one standard reflector by the multi-spectrum spectrometer and obtaining a spectral intensity equivalent of each of the sub-spectrometer by a known reflectance of the at least one standard reflector. A multi-spectrum spectrometer is also provided.

Description

Spectral integration calibration method and multi-spectral spectrometer

The invention relates to an optical correction method and a spectrometer, and in particular to a spectrum integration correction method and a multispectral spectrometer.

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

Using a plurality of different photodetectors to sense different wavelength ranges respectively can obtain a plurality of spectra of different wavelength ranges, but it is difficult to integrate these spectra into one spectrum. First of all, different photodetectors have different spectral responses, so if the two spectra are combined forcibly, there will be problems that cannot be quantitatively integrated. In addition, when the optical path is switched to control the reflector to switch between different photodetectors, it is impossible to monitor the object under test in real-time to achieve real-time distribution of spectral input signals.

The invention provides a spectrum integration correction method, which can adjust the spectrometer to integrate multiple sub-spectrums well.

The invention provides a multi-spectrum spectrometer, which can well integrate multiple sub-spectrums into one spectrum.

An embodiment of the present invention proposes a spectral integration correction method, including: providing a multi-spectral spectrometer, the multi-spectral spectrometer includes a plurality of sub-spectrometers for respectively measuring a plurality of sub-spectra in different wavelength ranges; using the multi-spectral spectrometer to measure at least A spectrum of a wavelength calibration component, and using a plurality of known characteristic wavelengths of the spectrum of at least one wavelength calibration component to calibrate the detection wavelengths of these sub-spectrometers respectively; and using a multispectral spectrometer to measure the spectrum of at least one standard reflector, and The respective spectral intensity equivalents of the sub-spectrometers are obtained using the known reflectance of at least one standard reflector.

An embodiment of the present invention provides a multispectral spectrometer for measuring the spectrum of an object to be measured. The multi-spectrum spectrometer includes a light source, a light splitting element, multiple sub-spectrometers and a controller. The light source is used to provide an illumination beam to irradiate the object under test, wherein the object under test reflects the illumination beam into a signal light. The light splitting element is arranged on the path of the signal light, and divides the signal light into multiple sub-beams. These sub-spectrometers are respectively arranged on the transmission paths of the sub-beams to measure multiple sub-spectra with different wavelength ranges. The controller is electrically connected to these sub-spectrometers, and is used to convert these sub-spectra into the same spectral intensity equivalent and then integrate them into a spectrum.

In the spectral integration correction method of the embodiment of the present invention, since the wavelength of the multiple sub-spectrometers and the spectral intensity equivalents of the multiple sub-spectrums obtained by using the wavelength calibration piece and the standard reflection piece are corrected, the multi-spectral spectrometer can be calibrated into a good integration of multiple sub-spectra. In the multispectral spectrometer of the embodiment of the present invention, since the controller converts these sub-spectra into the same spectral intensity equivalent and then integrates them into one spectrum, multiple sub-spectra can be well integrated into one spectrum.

FIG. 1 is a schematic cross-sectional view of a multispectral spectrometer according to an embodiment of the present invention. Please refer to FIG. 1 , the multispectral spectrometer 100 of this embodiment is used to measure the spectrum of an object 50 to be tested. The multispectral spectrometer 100 includes at least one light source 110 (two light sources 110 are taken as an example in FIG. 1 , but the present invention is not limited thereto), a spectroscopic element 121 , multiple sub-spectrometers 130 and a controller 140 . The light source 110 is used for providing an illumination beam 112 to illuminate the object under test 50 , and the object under test 50 reflects the illumination beam 112 into a signal light 52 . In this embodiment, the light source 110 is, for example, a tungsten filament lamp, a halogen lamp, other black body radiation sources or other suitable light sources with continuous spectrum.

The light splitting element 121 is disposed on the path of the signal light 52 and divides the signal light 52 into a plurality of sub-beams 53 . In this embodiment, the multispectral spectrometer 100 further includes a Y-shaped fiber 120 , and the light splitting element 121 is the light-incident end of the Y-shaped fiber 120 . The Y-shaped optical fiber 120 includes at least two sub-fibers 122, and these sub-fibers 122 are close together at one end (ie, the end where the optical splitting element 121 is located in FIG. 1 ) and separated at the other end. The signal light 52 from the object under test 50 irradiates one end of the sub-fibers 122 and enters into the sub-fibers 122 respectively.

The sub-spectrometers 130 are respectively arranged on the transmission paths of the sub-beams 53 to measure a plurality of sub-spectra with different wavelength ranges. In this 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 can also be a beam splitter or a beam splitter to split the signal light 52 into two sub-beams 53, and the two sub-beams 53 are transmitted to the two sub-beams through two optical fibers respectively. spectrometer 130.

In this embodiment, the controller 140 is electrically connected to these sub-spectrometers 130 for converting these sub-spectra into the same spectral intensity equivalent and then integrating them into a spectrum. In one embodiment, the controller 140 is, for example, a central processing unit (central processing unit, CPU), a microprocessor (microprocessor), a digital signal processor (digital signal processor, DSP), a programmable controller, a programmable The present invention is not limited to a logic device (programmable logic device, PLD) or other similar devices or a combination of these devices. In addition, in one embodiment, each function of the controller 140 may be implemented as a plurality of program codes. These program codes are stored in a memory, and are executed by the controller 140 . Alternatively, in one embodiment, each function of the controller 140 may be implemented as one or more circuits. The present invention does not limit the implementation of the functions of the controller 140 by means of software or hardware.

In the multispectral spectrometer 100 of this embodiment, since the controller 140 converts these sub-spectra into the same spectral intensity equivalent and then integrates them into one spectrum, multiple sub-spectra can be well integrated into one spectrum. In this way, it is helpful for the user to easily interpret the characteristics of the object under test 50 from a single spectrum with a wide wavelength range.

In this embodiment, the multispectral spectrometer 100 further includes a half integrating sphere 150 for covering the object 50 to be tested, wherein the light source 110 and the light splitting element 121 are disposed on the spherical shell of the half integrating sphere 150 . In addition, in this embodiment, the multi-spectral spectrometer further includes a collimating lens 160, which is arranged on the spherical shell of the half integrating sphere 150, wherein the collimating lens 160 is used to transmit the signal light 52 to the spectroscopic element 121 in a collimated manner, And try to evenly distribute the signal beams 52 to different sub-fibers 122 .

The following content will introduce how to calibrate the multispectral spectrometer 100 into a spectrum integration calibration method that can well integrate multiple sub-spectra into one spectrum.

FIG. 2 is a flowchart of a spectrum integration correction method according to an embodiment of the present invention. Please refer to FIG. 1 and FIG. 2 , the spectral integration calibration method of this embodiment can be used to calibrate the multispectral spectrometer 100 in FIG. 1 and the multispectral spectrometer in various possible variant embodiments. The spectral integration correction method includes the following steps. Firstly, step S110 is executed to provide a multi-spectral spectrometer 100 , which includes a plurality of sub-spectrometers 130 for respectively measuring a plurality of sub-spectra in different wavelength ranges. Next, step S120 is executed, using the multi-spectral spectrometer 100 to measure the spectrum of at least one wavelength calibrator 60, and using a plurality of known characteristic wavelengths of the spectrum of the at least one wavelength calibrator 60 to calibrate the detection wavelengths of these sub-spectrometers 130 respectively . The wavelength calibrator 60 can be placed at the position of the object under test 50 to replace the object under test 50 , and is used for these sub-spectrometers to measure the spectrum of the wavelength calibrator 60 .

FIG. 3 is an absorption spectrum diagram of the wavelength correction member 60 of FIG. 1 . Referring to FIGS. 1 to 3 , the wavelength calibration component 60 is a standard component whose 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. What these sub-spectrometers 130 directly measure is, for example, the reflectance spectrum, but the reflectance spectrum can be simply converted into an absorption spectrum by the controller 140, for example, using a normalized value or a higher value to subtract the reflectance of each wavelength spectral intensity. The characteristic wavelength can be viewed from the absorption spectrum or the reflection spectrum. When a certain pixel of the image sensor (such as a one-dimensional or two-dimensional sensing array) of the sub-spectrometer 130 senses the trough (when using the reflection spectrum to correct) or the peak (when using the absorption spectrum to correct) of the characteristic wavelength ), then this pixel position can be defined as the position of the characteristic wavelength in the spectrum, so the horizontal axis of the spectrum (ie wavelength) can be corrected.

In this embodiment, correcting the detection wavelengths of these sub-spectrometers 130 further includes performing numerical interpolation calculations based on these known characteristic wavelengths, and using the calculated values to correct the detection wavelengths of these sub-spectrometers 130, so that these The wavelength scales of the sub-spectrometers 130 are consistent in size. In this way, the scales of the horizontal axes of different sub-spectrometers 130 (that is, the scale of wavelength) can be of the same size, so as to facilitate the integration of multiple sub-spectrums into a single spectrum in the future, and there is a consistent range from short wavelength to long wavelength. wavelength scale.

In an embodiment, a plurality of different wavelength calibration elements 60 can be used to calibrate wavelengths of different bands. For example, the above-mentioned at least one wavelength calibrating element 60 includes a first wavelength calibrating element and a second wavelength calibrating element, the maximum characteristic wavelength of the first wavelength calibrating element is greater than the maximum characteristic wavelength of the second wavelength calibrating element. Wherein, the first wavelength correction element can be used to correct the wavelength in the longer wavelength band, and the second wavelength correction element can be used to correct the wavelength in the shorter wavelength band. The material of the first wavelength calibrator may include oily organic matter, and the material of the second wavelength calibrator may include rare earth metals, but the present invention does not limit the materials of the first wavelength calibrator and the second wavelength calibrator, as long as they are multispectral Standard parts formed of materials with characteristic wavelengths within the detection range of the spectrometer 100 can be used as the wavelength calibration part 60 . The calibration standard of the wavelength calibrator 60 can be traced back to the NIST standard known to those skilled in the art, where the full name of NIST is "National Institute of Standards and Technology".

Then, step S130 is executed, using the multi-spectral spectrometer 100 to measure the spectrum of at least one standard reflector 70 , and using the known reflectance of the at least one standard reflector 70 to obtain respective spectral intensity equivalents of the sub-spectrometers 130 . FIG. 4A and FIG. 4B are reflection sub-spectra of the local reflector measured by the two sub-spectrometers of the multi-spectral spectrometer in FIG. 1 . It can be seen from FIG. 4A and FIG. 4B that, in addition to the wavelength ranges of the two sub-spectrums being different, the scales of the spectral intensity on the vertical axis are also different. At this time, if the two sub-spectra are put together, a continuous spectrum from 900 nanometers to 2400 nanometers will not be formed, but there will be a step difference in the middle and the spectral intensity will be much smaller after about 1600 nanometers. And almost invisible strange and abnormal spectral shape. At this time, these sub-spectrometers 130 can be used to measure the standard reflector 70, and the reflectance of the standard reflector 70 at each wavelength is known, so the spectral intensities of the two sub-spectra can be adjusted to the same equivalent. For example, the spectral intensity of at least one of the two sub-spectra can be multiplied by an appropriate multiple, for example, the spectral intensities corresponding to the 99% reflectance of the standard reflector 70 in the two sub-spectra should be consistent , so at least one of the two spectral intensities is multiplied by an appropriate multiple, and the two spectral intensities are adjusted to be consistent, that is, to be adjusted to the same spectral intensity equivalent. In one embodiment, the material of the standard reflector 70 is, for example, metal, but the invention is not limited thereto.

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 . Please refer to Fig. 1, Fig. 2 and Fig. 5A to Fig. 5D, above-mentioned at least one standard reflector 70 comprises a first standard reflector and a second standard reflector, the reflectivity of the first standard reflector is greater than the second standard reflector reflectivity. The spectral integration correction method further includes calculating the spectral intensity corresponding to the reflectance of 100% based on the known reflectance of the first standard reflector, and calculating the corresponding spectral intensity when the reflectance is zero based on the known reflectance of the second standard reflector. spectral intensity. Specifically, in the reflectance spectrum of the first standard reflector in Fig. 5A, there is a plateau region whose reflectivity is about 0.99, so when the sub-spectrometer 130 measures the spectrum with this plateau region, the spectrum of the plateau region can be Intensity is regarded as a reflectance of 0.99, and the corresponding spectral intensity is calculated linearly when the reflectance is 1. For example, the spectral intensity of the plateau area is divided by 0.99 and then multiplied by 1 to obtain the corresponding spectrum when the reflectance is 1. strength.

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 linearly deduced when the reflectance is 0 Corresponding spectral intensity, in this way, the intensity position of the absolute zero baseline of the sub-spectrometer 130 can be corrected, and the dark noise zero background value can be corrected.

In this embodiment, the above-mentioned 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 In between, and the spectral integration correction method further includes estimating the spectral intensity corresponding to an intermediate value of the reflectance according to the known reflectance of the third standard reflector, wherein the intermediate value is between 0 and 100%. For example, the reflectivity of the third standard reflector changes from about 0.72 to 0.86 with the change of the wavelength, so the spectral signal intensity of the third standard reflector measured by the sub-spectrometer 130 can be divided according to the corresponding wavelength. It is considered to be from 0.72 to 0.86, and then linearly calculate the position of the scale line whose reflectivity is 0.75.

In the same way, the above-mentioned at least one standard reflector 70 may further include a fourth standard reflector, and the reflectivity of the fourth standard reflector varies from 0.48 to 0.56 with the change of wavelength, so the measured value of the sub-spectrometer 130 can be The spectral signal intensity of the third standard reflector is considered to be from 0.48 to 0.56 according to the corresponding wavelength, and then the position of the scale line with a reflectivity of 0.5 is calculated linearly.

The number of the above-mentioned standard reflectors 70 is not limited, and the vertical axis (ie reflectivity) can be calibrated more accurately when the number is large. After correcting the reflectance of the standard reflector 70, interpolation or extrapolation can be used to calculate the spectral intensity corresponding to each scale of the reflectance from 0 to 1, that is, to correct the spectral intensity between 0 and 1. every tick. In addition, since the spectral response intensity and the actual reflectance of the image sensor of the sub-spectrometer 130 may show nonlinear changes, and the image sensors of different sub-spectrometers 130 may be different due to the material, resulting in the above-mentioned nonlinear The change presents different situations, so a larger number of standard reflectors 70 with different reflectivities (for example, corresponding to the third standard reflector of FIG. 5C or corresponding to the fourth standard reflector of FIG. The reflectance) helps to correct these nonlinear changes, and interpolation or extrapolation can be used more accurately to calculate the spectral intensity corresponding to each scale of the reflectance from 0 to 1. In this way, absolute quantitative changes in the sensitivity of the test sample signal can be confirmed.

The calibration standard of the standard reflector 70 complies with the NIST standard and the NVLAP calibration (NVLAP calibration) standard well known to those skilled in the art. The full name of NVLAP is "National Voluntary Laboratory Accreditation Program".

Afterwards, step S140 is executed, according to the respective spectral intensity equivalents of the sub-spectrometers 130 , the multiple sub-spectra measured by the sub-spectrometers 130 are converted into the same spectral intensity equivalents and then integrated. That is to say, according to the corrected reflectance in step S130, multiple sub-spectra are combined into a single spectrum with the same reflectance scale standard, then this single spectrum is a complete good spectrum from short wavelength to long wavelength .

FIG. 6 is an integrated spectrum obtained when the multispectral spectrometer in FIG. 1 measures a sample after being calibrated by the spectrum integration correction method in FIG. 2 . It can be seen from FIG. 6 that the integrated spectrum obtained by the multispectral spectrometer 100 in 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 can store the above calibration values in a built-in memory or transmit them to a server for reference. Such a sample can also be used to be measured by other multispectral spectrometers 100 to obtain spectra, and from the spectra, it can be quickly confirmed whether other multispectral spectrometers are well calibrated.

In addition, the corrected wavelength and reflectance data in steps S120 and S130 in FIG. 2 can be stored in a memory through the controller 140. After the multispectral spectrometer 100 leaves the factory, the data stored in the memory can be directly used. Step S140 is executed to convert multiple sub-spectra into the same spectral intensity equivalent through the controller 140 and then integrate them into a single good spectrum with a wide wavelength range.

To sum up, in the spectral integration correction method of the embodiment of the present invention, since the wavelength of the multiple sub-spectrometers and the spectral intensity equivalents of the multiple sub-spectrums obtained by using the wavelength calibration piece and the standard reflection piece are corrected, the The multispectral spectrometer is tuned to provide good integration of multiple sub-spectra. In the multispectral spectrometer of the embodiment of the present invention, since the controller converts these sub-spectra into the same spectral intensity equivalent and then integrates them into one spectrum, multiple sub-spectra can be well integrated into one spectrum.

50: The object to be tested 52: signal light 53: sub-beam 60:Wavelength correction piece 70: Standard reflector 100: Multispectral spectrometer 110: light source 112: Lighting beam 120:Y type optical fiber 121: Light splitting element 122: sub-fiber 130: sub-spectrometer 140: Controller 150: Half integrating sphere 160: collimating lens S110, S120, S130, S140: steps

FIG. 1 is a schematic cross-sectional view of a multispectral spectrometer according to an embodiment of the present invention. FIG. 2 is a flowchart of a spectrum integration correction method according to an embodiment of the present invention. FIG. 3 is an absorption spectrum diagram of the wavelength correction member of FIG. 1 . FIG. 4A and FIG. 4B are reflection sub-spectra of the local reflector measured by the two sub-spectrometers of the multi-spectral spectrometer in FIG. 1 . 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 . FIG. 6 is an integrated spectrum obtained when the multispectral spectrometer in FIG. 1 measures a sample after being calibrated by the spectrum integration correction method in FIG. 2 .

50: The object to be tested 52: signal light 53: sub-beam 60:Wavelength correction piece 70: Standard reflector 100: Multispectral spectrometer 110: light source 112: Lighting beam 120: Y type optical fiber 121: Light splitting element 122: sub-fiber 130: sub-spectrometer 140: Controller 150: Half integrating sphere 160: collimating lens

Claims (9)

A spectral integration correction method, comprising: providing a multi-spectral spectrometer, the multi-spectral spectrometer includes a plurality of sub-spectrometers for respectively measuring a plurality of sub-spectra in different wavelength ranges; using the multi-spectral spectrometer to measure at least one wavelength calibration component Spectrum, and using multiple known characteristic wavelengths of the spectrum of the at least one wavelength calibration member, respectively correct the detection wavelengths of the sub-spectrometers; use the multi-spectral spectrometer to measure the spectrum of at least one standard reflector, and use the at least The known reflectance of a standard reflector obtains the respective spectral intensity equivalents of these sub-spectrometers; Spectral intensity equivalents are post-integrated. The spectral integration correction method as described in Claim 1, wherein correcting the detection wavelengths of the sub-spectrometers further includes performing numerical interpolation calculations based on the known characteristic wavelengths, and using the calculated values to calibrate the sub-spectrometers The detection wavelength, so that the wavelength scales of these sub-spectrometers have the same size. The spectrum integration correction method as described in claim 1, wherein the at least one standard reflector includes a first standard reflector and a second standard reflector, and the reflectivity of the first standard reflector is greater than that of the second standard reflector The spectral integration correction method further includes calculating the spectral intensity corresponding to 100% reflectance according to the known reflectance of the first standard reflector, and calculating the reflectance according to the known reflectance of the second standard reflector The corresponding spectral intensity when the rate is zero. The spectrum integration correction method as described in claim 3, wherein the at least one standard reflector further includes 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 first standard reflector between the reflectances of the second standard reflector, and the spectral integration correction method further includes calculating the spectral intensity corresponding to a reflectance of an intermediate value based on the known reflectance of the third standard reflector, wherein the intermediate value is between Between 0 and 100 percent. The spectral integration correction method as described in Claim 1, wherein the at least one wavelength correction element includes a first wavelength correction element and a second wavelength correction element, and the maximum characteristic wavelength of the first wavelength correction element is greater than that of the second wavelength correction element The maximum characteristic wavelength of the component. A multispectral spectrometer is used to measure the spectrum of an object to be measured, and the multispectrum spectrometer includes: a light source for providing an illumination beam to illuminate the object to be measured, wherein the object to be measured reflects the illumination beam into a Signal light; a light splitting element is arranged on the path of the signal light, and the signal light is divided into multiple sub-beams; multiple sub-spectrometers are respectively arranged on the transmission paths of the sub-beams to measure multiple sub-spectra; and a controller, electrically connected to the sub-spectrometers, for converting the sub-spectra into the same spectral intensity equivalent and integrating them into a spectrum. The multi-spectral spectrometer according to Claim 6 further includes a half integrating sphere for covering the object to be measured, wherein the light source and the light splitting element are arranged on the spherical shell of the half integrating sphere. The multi-spectral spectrometer as described in Claim 7 further includes a collimating lens disposed on the spherical shell of the semi-integrating sphere, wherein the collimating lens is used to transmit the signal light to the spectroscopic element in a collimated manner. The multispectral spectrometer as claimed in item 8, wherein the light splitting element is the light incident end of a Y-shaped optical fiber.

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