An apparatus and method for automatic calibration of a spectrometer

Abstract

The present application relates to the technical field of measurement, in particular to a kind of spectrometer automatic calibration device and method, comprising: light source, optical isolator, fiber coupler, standard reference light source, adjustable fiber attenuator, first fiber collimator, holographic frequency selection module, electric reflector, volume holographic grating, second fiber collimator, beam splitter, optical interface unit, to be measured spectrometer, photoelectric detector, electric reflector driver, angle-second level angle encoder, control module, communication module, computer and image display unit.The present application utilizes volume holographic grating to select the corresponding relationship between the pixel of spectrometer and wavelength, can continuously select monochromatic light, and the theoretical resolution is consistent with the spectral resolution of light source;Using automatic calibration method, the automatic calibration of spectrometer is realized, pixel-wavelength calibration data can be automatically generated and stored in preset format, which is convenient for automatic calibration and data processing of spectral measurement software, and realizes wavelength-pixel position registration at pixel level.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and more specifically, to an automatic calibration device and method for a spectrometer. Background Technology

[0002] Spectrometers, characterized by high precision, high sensitivity, rapid on-site measurement, wide application, and ease of operation, are essential general-purpose instruments in the fields of precision analysis and measurement. They are widely used in astronomy, biomedicine, substance identification, chemical environment, defense technology, energy materials, and industrial testing. All spectrometers undergo necessary calibration procedures after manufacturing. During use, factors such as environmental vibration, temperature gradients, structural stress release, loose connections, and structural aging can alter the pixel-wavelength correspondence within the spectrometer. In such cases, the previously calibrated pixel-wavelength correspondence becomes inapplicable, introducing measurement errors and necessitating recalibration.

[0003] Currently, spectrometer calibration requires manual intervention, which is cumbersome and lacks precision. Furthermore, when using monochromatic light calibration, the accuracy is difficult to guarantee due to factors such as the spectral bandwidth of the light source, system dispersion, system assembly and adjustment errors, and human error. In scientific measurement, spectral calibration is crucial for determining the input-output relationship of the measurement system, assigning scale values ​​to the system, defining its static parameters, eliminating system errors, and improving the accuracy of the measurement system.

[0004] There are generally two methods to determine the correspondence between wavelength and pixels: one is to derive the correspondence through the structural design of the spectrometer. However, this method is not ideal in practical applications, as the error mainly stems from simplifications in various theoretical calculations. In practice, there are multiple error sources, including design errors, manufacturing errors, and assembly / adjustment errors, making it less helpful for practical applications. The second method is to conduct wavelength calibration experiments. Wavelength calibration experiments typically require obtaining characteristic spectral lines, usually using a standard light source, a frequency-modulated laser, a monochromator, or a filter with a specific wavelength response spectrum. Using lasers or monochromators for calibration is costly, and filter spectral lines have low accuracy. When calibration accuracy requirements are not stringent, a standard light source can be used to provide the calibration spectrum.

[0005] The common practice is to calibrate the spectrometer using monochromatic light of several known wavelengths, and then construct a polynomial to represent the functional relationship between pixel position and wavelength. Wavelength calibration methods for spectrometers include:

[0006] 1) Manual calibration method: By processing the data of known relative intensity of spectral lines, the spectral lines obtained by the spectrometer are matched with the standard spectral lines of the light source to find the correspondence between wavelength and pixel.

[0007] 2) Optical Equation Derivation Method: This method utilizes the structural parameters of the spectrometer and the optical parameters of the lens, and derives the theoretical correspondence between wavelength and pixel using grating equations and geometric optics. However, due to simplifications in various stages of the theoretical calculation and assembly / adjustment errors of optical components, it contains significant errors, making practical applications quite difficult.

[0008] 3) Traditional calibration method: The functional relationship between standard wavelength and pixel is obtained by using polynomial fitting.

[0009] Each wavelength's spectral line has a certain pixel width (determined by the spectrometer's resolution), and the position corresponding to a spectral line covers multiple consecutive pixels. The pixel position corresponding to the peak point of the spectral line is the pixel position corresponding to that wavelength. Traditional calibration methods use manually selected spectral line fitting functions, which result in significant fitting errors.

[0010] The main methods for manually selecting spectral lines for function fitting include: parametric fitting, maximum value method, centroid method, interpolation method, Gaussian fitting method, and polynomial fitting method. The fitting accuracy of parametric fitting is directly related to the selected function; the maximum value method cannot guarantee that the sampling points will capture the peak value of the original spectral line; the centroid method cannot determine the shape and peak position of the original spectral line and has low accuracy; the interpolation method is difficult and prone to errors; the Gaussian fitting method outputs spectral lines whose shape no longer follows the Gaussian function distribution, resulting in errors; and polynomial fitting ignores the detailed shape of the spectral lines. Summary of the Invention

[0011] This invention provides an automatic calibration device and method for spectrometers to solve the technical problem that spectrometers cannot be calibrated automatically and the calibration process is complex.

[0012] According to an embodiment of the present invention, an automatic calibration device for a spectrometer is provided, comprising: a light source, an optical isolator, an optical fiber coupler, a standard reference light source, an adjustable optical fiber attenuator, a first optical fiber collimator, a holographic frequency selection module, an electric reflector, a volume holographic grating, a second optical fiber collimator, a beam splitter, an optical interface unit, a spectrometer under test, a photodetector, an electric reflector driver, an arcsecond-level angle encoder, a control module, a communication module, a computer, and an image display unit; wherein:

[0013] The light source and the standard reference light source emit light under the control of the control module. The control module controls the motorized reflector to continuously scan within a preset angle range according to the minimum division angle increment of the motorized reflector.

[0014] The control module controls the spectrometer under test to acquire scanning spectral signals and uploads them to the computer and image display unit via the communication module for processing, analysis, and display.

[0015] Based on the spectral results displayed by the computer and image display unit, adjust the adjustable fiber optic attenuator so that the maximum value of the spectral signal acquired by the spectrometer under test accounts for 50%-99% of the maximum corresponding signal intensity of the spectrometer under test.

[0016] When the signal collected by the photodetector is at its maximum, the rotation angle of the motorized reflector and the corresponding output wavelength angle are recorded by the arcsecond-level angle encoder.

[0017] The control module acquires the spectral information corresponding to the wavelength collected by the spectrometer under test and the corresponding electric reflector angle information collected by the arcsecond-level angle encoder;

[0018] The control module simultaneously collects the spectral information corresponding to the wavelength acquired by the spectrometer under test and the corresponding electric reflector angle information acquired by the arcsecond-level angle encoder, and uploads them to the computer and image display unit via the communication module for analysis, processing and display, thereby realizing the automatic wavelength calibration of the spectrometer under test.

[0019] Furthermore, the light source is a supercontinuum pulsed laser source, which is electrically connected to the control module and has a spectral range wider than that of a tunable laser, generating a broadband continuous spectrum that covers the measurement range of the spectrometer.

[0020] Furthermore, an optical isolator is a passive optical device that only allows unidirectional light to pass through. It is connected to a light source and an optical fiber coupler to restrict the direction of light transmission, so that light can only be transmitted in one direction.

[0021] Furthermore, the fiber optic coupler is a passive optical component used to combine and split optical signals. It connects to optical isolators, standard reference light sources, and adjustable fiber optic attenuators to couple the light emitted by the light source and the standard reference light source into the system's optical path for calibration measurements.

[0022] Furthermore, the standard reference light source includes one of the following: a He-Ne laser with fiber optic output, monochromatic light within the measurement range of the spectrometer under test, or quasi-monochromatic light with a bandwidth ≤0.1nm. It is positioned between the fiber optic coupler and the control module, connected to the fiber optic coupler via optical fiber, and electrically connected to the control module. It provides narrow-linewidth quasi-monochromatic light of known standard wavelength for calibrating the reference rotation angle of the motorized reflector of the holographic frequency selection module.

[0023] Furthermore, an adjustable fiber optic attenuator is an optical device that can reduce the energy of an optical signal. It is connected to an optical fiber coupler and a first optical fiber collimator to adjust the light intensity of the spectrometer system.

[0024] The first fiber collimator is an achromatic lens or a group of achromatic lenses, which converts the transmitted light in the fiber into collimated light for output. It is connected to the fiber of the adjustable fiber attenuator. The optical axis of the lens or lens group intersects the midpoint of the motorized mirror. The first fiber collimator projects the combined light from the fiber coupler into the reflection area of ​​the motorized mirror of the holographic frequency selection module through free space optical communication collimation and beam expansion.

[0025] Furthermore, the holographic frequency selection module includes an electric reflector and a volume holographic grating, which selects light of a specific wavelength for high-precision micron-level calibration of the spectrometer under test;

[0026] The electric reflector is a type of galvanometer, voice coil motor fast reflector, microelectromechanical deformable reflector, or piezoelectric ceramic reflector. It is electrically connected to an electric reflector driver and an arcsecond-level angle encoder. According to the received signal, it adjusts the pitch angle of the electric reflector and projects the broadband parallel beam projected by the first fiber collimator onto the volume holographic grating at a set angle.

[0027] The second fiber collimator is an achromatic lens or an achromatic lens group, which couples external parallel light into a single-mode fiber, connects to the beam splitter fiber, and communicates with the holographic frequency selection module via free-space optical communication. It is used to receive the reflected light of the corresponding band reflected by the holographic grating.

[0028] Furthermore, a beam splitter is an optical element that splits a beam of light into two or more beams of light. It is connected to the second fiber collimator, photodetector, and optical interface unit fiber, and splits the beam collected by the second fiber collimator according to the light intensity ratio of the photodetector and the optical interface unit.

[0029] The optical interface unit is a fiber optic interface or a free-light alignment system, which is connected to the fiber optic cable of the beam splitter and provides a fiber optic interface or free-light transmission interface to realize the optical connection between the spectrometer under test and the automatic calibration device of the spectrometer.

[0030] The photodetector is electrically connected to the fiber optic cable and control module of the beam splitter, and is used to measure the light intensity of the standard reference light emitted by the standard reference light source, which is separated by the beam splitter.

[0031] Furthermore, the electric reflector driver is an encoder that is electrically connected to the control module and the electric reflector, and is used to receive rotation commands from the control module and drive the electric reflector to rotate.

[0032] An arcsecond-level angle encoder is electrically connected to the control module and the motorized reflector. It returns the current angle value of the object under test to the control module via an electrical signal to measure the rotation angle of the motorized reflector.

[0033] According to another embodiment of the present invention, an automatic calibration method for a spectrometer is provided, comprising:

[0034] The light source and the standard reference light source emit light under the control of the control module. The control module controls the motorized reflector to continuously scan within a preset angle range according to the minimum division angle increment of the motorized reflector.

[0035] The control module controls the spectrometer under test to acquire scanning spectral signals and uploads them to the computer and image display unit via the communication module for processing, analysis, and display.

[0036] Based on the spectral results displayed by the computer and image display unit, adjust the adjustable fiber optic attenuator so that the maximum value of the spectral signal acquired by the spectrometer under test accounts for 50%-99% of the maximum corresponding signal intensity of the spectrometer under test.

[0037] When the signal collected by the photodetector is at its maximum, the rotation angle of the motorized reflector and the corresponding output wavelength angle are recorded by the arcsecond-level angle encoder.

[0038] The control module acquires the spectral information corresponding to the wavelength collected by the spectrometer under test and the corresponding electric reflector angle information collected by the arcsecond-level angle encoder;

[0039] The control module simultaneously collects the spectral information corresponding to the wavelength acquired by the spectrometer under test and the corresponding electric reflector angle information acquired by the arcsecond-level angle encoder, and uploads them to the computer and image display unit via the communication module for analysis, processing and display, thereby realizing the automatic wavelength calibration of the spectrometer under test.

[0040] A storage medium storing a program file capable of implementing any of the above-mentioned automatic calibration methods for spectrometers.

[0041] A processor for running a program, wherein the program executes any of the above-mentioned automatic calibration methods for spectrometers.

[0042] The automatic calibration device and method for spectrometers in this embodiment of the invention utilizes a volume holographic grating to select a specific wavelength to determine the correspondence between spectrometer pixels and wavelengths, enabling continuous accurate selection of monochromatic light with theoretical resolution consistent with the spectral resolution of the light source. The automatic calibration method achieves automatic calibration of the spectrometer, automatically generating pixel-wavelength calibration data and storing it in a preset format. This facilitates automatic calibration and data processing by the spectral measurement software, achieving pixel-level wavelength-pixel position registration. This provides a highly efficient and convenient automatic calibration method for spectrometers. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0044] Figure 1This is a schematic diagram of the structure of an automatic calibration device for a spectrometer according to the present invention;

[0045] Figure 2 This is a schematic diagram of the holographic frequency selection module in this invention.

[0046] Explanation of icon numbers:

[0047] 1-Supercontinuum light source, 2-Optical isolator, 3-Fiber optic coupler, 4-Standard reference light source, 5-Adjustable fiber optic attenuator, 6-First fiber optic collimator, 7-Holographic frequency selection module, 701-Electrically driven mirror, 702-Volume holographic grating, 8-Second fiber optic collimator, 9-Beam splitter, 10-Optical interface unit, 11-Spectrometer under test, 12-Photodetector, 13-Electrically driven mirror driver, 14-Arcsecond-level angle encoder, 15-Control module, 16-Communication module, 17-Computer and image display unit. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0050] To address the challenges of spectrometers not being able to perform automatic calibration and the complexity of the calibration process, this invention provides an automatic calibration device and method for spectrometers, which can achieve pixel-level wavelength-pixel position registration.

[0051] The technical problem to be solved by this invention is to use a volume holographic grating to select a specific wavelength to determine the correspondence between the pixels and wavelength of a spectrometer, which can continuously select monochromatic light with theoretical resolution consistent with the spectral resolution of the light source; and to use an automatic calibration method to realize the automatic calibration of the spectrometer, in which pixel-wavelength calibration data can be automatically generated and stored in a preset format, which facilitates automatic calibration and data processing of spectral measurement software, and realizes pixel-level wavelength-pixel position registration. This invention provides an automatic calibration device and method for spectrometers with high measurement efficiency and simple measurement.

[0052] exist Figure 1 The device for automatically calibrating a spectrometer in this embodiment includes: a supercontinuum light source 1, an optical isolator 2, an optical fiber coupler 3, a standard reference light source 4, an adjustable optical fiber attenuator 5, a first optical fiber collimator 6, a holographic frequency selection module 7, an electric reflector 701, a volume holographic grating 702, a second optical fiber collimator 8, a beam splitter 9, an optical interface unit 10, a spectrometer under test 11, a photodetector 12, an electric reflector driver 13, an arcsecond-level angle encoder 14, a control module 15, a communication module 16, and a computer and image display unit 17.

[0053] The supercontinuum light source 1 is a supercontinuum pulsed laser light source, which is electrically connected to the control module 15. It has a wider spectral range than the tunable laser and its function is to generate a broadband continuous spectrum that covers the measurement range of the spectrometer.

[0054] Optical isolator 2 is a passive optical device that allows only unidirectional light to pass through. It is connected to the supercontinuum light source 1 and the fiber optic coupler 3 to restrict the direction of light transmission, ensuring that light can only travel in one direction. The function of optical isolator 2 is to prevent adverse effects on the light source and optical path system caused by backward-transmitted light due to various reasons in the system's optical path.

[0055] It is understandable that the optical isolator 2 prevents backward transmission light generated in the system's optical path due to various reasons from traveling along the supercontinuum light source 1, control module 15, and communication module 16 to the computer and image display unit 17, thus affecting the results of the computer and image display unit 17 in analyzing and processing the returned signal.

[0056] Fiber optic coupler 3 is a passive optical component used for combining and splitting optical signals. It connects to the optical isolator 2, the standard reference light source 4, and the adjustable fiber optic attenuator 5, coupling the light emitted from the supercontinuum light source 1 and the standard reference light source 4 into the system optical path for calibration measurements. The function of fiber optic coupler 3 is to couple the light emitted from the supercontinuum light source 1 and the standard reference light source 4 into the system optical path for subsequent calibration measurements.

[0057] The standard reference light source 4 includes one of the following: a He-Ne laser with fiber optic output, monochromatic light within the measurement range of the spectrometer under test, or quasi-monochromatic light with a bandwidth ≤0.1nm. It is positioned between the fiber optic coupler 3 and the control module 15, connected to the fiber optic coupler 3 by optical fiber, and electrically connected to the control module 15. It provides narrow-linewidth quasi-monochromatic light with a known standard wavelength for calibrating the reference rotation angle of the motorized reflector 701 of the holographic frequency selection module 7.

[0058] The function of the standard reference light source 4 is to provide narrow-linewidth quasi-monochromatic light of known standard wavelength for calibrating the reference rotation angle of the motorized mirror. Optionally, the standard reference light source 4 can be an fiber-optic He-Ne laser or monochromatic light or quasi-monochromatic light with a bandwidth ≤0.1 nm that can be realized within the measurement range of the spectrometer under test.

[0059] The adjustable fiber optic attenuator 5 is an optical device that reduces the energy of the optical signal. It is connected to the fiber optic coupler 3 and the first fiber optic collimator 6 to adjust the light intensity of the spectrometer system. The function of the adjustable fiber optic attenuator 5 is to adjust the system light intensity and prevent the system from being overexposed due to the light intensity reaching saturation, thus introducing measurement errors.

[0060] The first fiber collimator 6 is an achromatic lens or a group of achromatic lenses, which converts the transmitted light in the fiber into collimated light (parallel light) for emission. It is connected to the adjustable fiber attenuator 5. The optical axis of the lens or lens group intersects the midpoint of the motorized reflector 701. The first fiber collimator 6 projects the combined light from the fiber coupler 3 into the reflection area of ​​the motorized reflector 701 of the holographic frequency selection module 7 using free-space optical communication collimation and beam expansion.

[0061] Optionally, the lens or lens group used in the first fiber collimator 6 is an achromatic lens or an achromatic lens group.

[0062] The holographic frequency selection module 7 includes an electric reflector 701 and a volume holographic grating 702, which selects light of a specific wavelength for high-precision micron-level calibration of the spectrometer 11 under test.

[0063] The electric reflector 701 is a type of galvanometer, voice coil motor fast reflector, microelectromechanical deformable reflector, or piezoelectric ceramic reflector. It is electrically connected to the electric reflector driver 13 and the arcsecond-level angle encoder 14. The pitch angle of the electric reflector 701 is adjusted according to the received signal, and the broadband parallel beam projected by the first fiber collimator 6 is projected onto the volume holographic grating 702 at a set angle.

[0064] Optionally, the electric reflector 701 can be a galvanometer, a voice coil motor fast reflector, a microelectromechanical deformable reflector, or a piezoelectric ceramic reflector.

[0065] The volume holographic grating 702 is set in the optical path that can receive the incident light from the motorized mirror 701 and reflect it to the second fiber collimator 8. It filters the coupled light from the supercontinuum light source 1 and the standard reference light source 4 according to the incident angle θ, and reflects the light of the corresponding band Δλ(θ), which is received by the second fiber collimator 8 and coupled into the fiber optic system.

[0066] like Figure 2 The volume holographic grating 702 reflects light of the wavelength band Δλ(θ) corresponding to the angle θ between the incident light and the k-axis, while transmitting light of other wavelength bands. The function of the volume holographic grating 702 is to select light of a specific wavelength that matches the light incident at a specific angle by the motorized reflector 701, and reflect this specific wavelength light to the second fiber collimator 8, where it is received and coupled into the fiber optic system.

[0067] The second fiber collimator 8 is an achromatic lens or an achromatic lens group that couples external parallel (approximately parallel) light into a single-mode fiber. It is connected to the fiber of the beam splitter 9 and communicates with the holographic frequency selection module 7 via free-space optical communication. It is used to receive the reflected light of the corresponding wavelength band Δλ(θ) reflected by the holographic grating 702. The function of the second fiber collimator 8 is to collect light of a specific wavelength reflected by the holographic grating 702.

[0068] Optionally, the lens or lens group used in the second fiber collimator 8 is an achromatic lens or an achromatic lens group.

[0069] The beam splitter 9 is an optical element that splits a beam of light into two or more beams. It is optically connected to the second fiber collimator 8, the photodetector 12, and the optical interface unit 10, and splits the beam collected by the second fiber collimator 8 according to the intensity ratio of the photodetector 12 to the optical interface unit 10.

[0070] The function of beam splitter 9 is to separate the light beam collected by second fiber collimator 8 according to a preset ratio between 1:1000 and 50:50, where the light intensity incident on photodetector 12 is greater than that incident on optical interface unit 10, and the beam beam is received and measured by photodetector 12.

[0071] The light intensity ratio is 1:99 to 50:50.

[0072] The optical interface unit 10 is a fiber optic interface or a free-light alignment system, connected to the fiber optic cable of the beam splitter 9, providing a fiber optic interface or free-light transmission interface to achieve optical connection between the spectrometer under test 11 and the automatic calibration device for the spectrometer. The function of the spectrometer under test 11 is to provide the calibration system.

[0073] The spectrometer under test 11 is used to decompose complex light into spectral lines and is electrically connected to the control module 15 to provide a calibration system. The function of the spectrometer under test 11 is to provide a calibration system.

[0074] The photodetector 12 is electrically connected to the fiber optic connection and control module 15 of the beam splitter 9, and is used to measure the light intensity of the standard reference light emitted by the standard reference light source 4, which is separated by the beam splitter 9.

[0075] The electric reflector driver 13 is an encoder electrically connected to the control module 15 and the electric reflector 701. It receives rotation commands from the control module 15 and drives the electric reflector 701 to rotate. The function of the electric reflector driver 13 is to receive specific rotation angle commands from the control module 15 and drive the electric reflector 701 to achieve a preset rotation.

[0076] The arcsecond-level angle encoder 14 is electrically connected to the control module 15 and the motorized reflector 701. It returns the current angle value of the object under test to the control module 15 via an electrical signal to measure the rotation angle of the motorized reflector 701. The function of the arcsecond-level angle encoder 14 is to acquire and measure the rotation angle of the motorized reflector 701.

[0077] The control module 15 is an encoder that is electrically connected to the supercontinuum light source 1, the standard reference light source 4, the spectrometer under test 11, the photodetector 12, the electric mirror driver 13, and the arcsecond-level angle encoder 14. It is used to control the operation of the supercontinuum light source 1, the standard reference light source 4, the spectrometer under test 11, the photodetector 12, the electric mirror driver 13, and the arcsecond-level angle encoder 14.

[0078] The communication module 16 is an encoder, which is electrically connected to the control module 15, the computer, and the image display unit 17, and is used to realize data transmission, data reception, and protocol conversion between the control module 15 and the computer and the image display unit 17.

[0079] The computer and image display unit 17 is electrically connected to the communication module 16 and is used to analyze, process and display images of the data collected by the calibration system.

[0080] Calibration method for automatic calibration device of spectrometer:

[0081] Step 1: The supercontinuum light source 1 and the standard reference light source 4 emit light under the control of the control module 15. The control module 15 controls the motorized reflector 701 to move at a preset angle. Within the selectable range (i.e., covering the cutoff wavelength λ emitted by supercontinuum source 1) i (All angles within the range of i = 1, 2) are continuously scanned according to the minimum division angle increment of the motorized reflector 701. Specifically...

[0082] The spectral range of the broadband continuous spectrum generated by the supercontinuum light source 1, which covers the measurement range of the spectrometer 11 under test, is set to [λ1,λ2], and the range of the incident angle of the incident beam on the corresponding volume holographic grating 702 is [θ1,θ2].

[0083] According to the grating equation:

[0084] 2nΛcosθ1=λ1

[0085] 2nΛcosθ1=λ2 (1)

[0086] From geometric relations, we can obtain:

[0087]

[0088] n is the refractive index of the volume holographic grating;

[0089] Λ: The thickness of the holographic layer of the volume holographic grating along the optical axis;

[0090] θ i (i=1,2): These are the reflection wavelengths λ and λ, respectively. i The angle of incidence when (i = 1, 2);

[0091] λ i (i=1,2): These are the cutoff wavelengths of the supercontinuum light source, respectively;

[0092] The angle between the reflecting surface of the electric mirror and the optical axis of the volume holographic grating.

[0093] Step 2: The control module 15 controls the spectrometer under test 11 to acquire the scanning spectral signal and uploads it to the computer and image display unit 17 for processing, analysis and display via the communication module 16.

[0094] Step 3: Based on the spectral results displayed by the computer and image display unit 17, adjust the adjustable fiber optic attenuator 5 so that the maximum value of the spectral signal acquired by the spectrometer under test 11 accounts for 50%-99% of the maximum corresponding signal intensity of the spectrometer under test 11.

[0095] Step 4: Repeat steps 1 and 2. When the signal collected by the photodetector 12 is at its maximum, the rotation angle of the motorized reflector 701 at this moment is recorded by the arcsecond-level angle encoder 14. The angle of the corresponding output wavelength at this time is θ. reference .

[0096] The initial setting angle error of the motorized reflector 701 is set to... According to geometric relations, we have:

[0097]

[0098] Step 5: Repeat steps 1 and 2 2-1000 times, and simultaneously acquire the wavelength λ collected by the spectrometer under test 11 by the control module 15. j The corresponding spectral information and the corresponding motorized reflector angle information acquired by the arcsecond-level angle encoder 14 Then we have:

[0099]

[0100] Step 6: The control module 15 will simultaneously acquire the wavelength λ acquired by the spectrometer under test 11. j The corresponding spectral information and the corresponding motorized reflector angle information acquired by the arcsecond-level angle encoder 14 The data is uploaded via communication module 16 to computer and image display unit 17 for analysis, processing, and display. Computer and image display unit 17 calculates the rotation angle of the motorized reflector 701. The position of the pixel corresponding to the maximum spectral intensity value at that time is the mathematical statistical estimate of the position. when Nearest neighbor integer N j Record the corresponding 701-degree rotation angle of the motorized reflector at this moment.

[0101] Step 7: When N j Record the corresponding 701-degree rotation angle of the motorized reflector when it is closest to the nearest integer. The mathematical statistical expectation of the incident angle of the beam for the corresponding volume holographic grating 702 is: Then we have:

[0102]

[0103] The mathematical expectation of the center wavelength of the incident light collected by the corresponding spectrometer 11 is:

[0104]

[0105] Then the number of pixels N of the acquisition camera of the spectrometer 11 under test j Correspondence between the wavelength of the incident light and the wavelength of the incident light, f(N) j )for:

[0106]

[0107] And the acquisition camera pixel N of the spectrometer 11 under test j Correspondence between the wavelength of the incident light and the wavelength of the incident light, f(N) j The data is recorded in the computer and image display unit 17 to achieve automatic wavelength calibration of the spectrometer 11 under test.

[0108] The beneficial effects of this invention are as follows:

[0109] This invention is used for automatic calibration of spectrometers. Compared with existing measurement and calibration devices, this invention has a simple structure, low cost, convenient operation, high measurement efficiency, stable and reliable measurement results, and can be self-calibrated, and can be widely used.

[0110] 1. The automatic calibration device and method for spectrometers provided by the present invention avoids the fitting of the light source spectrum, the calibration results have no fitting error and are not affected by the shape of the light source spectrum.

[0111] 2. The automatic calibration device and method for spectrometers provided by this invention have free light and fiber optic interfaces, making them more widely applicable.

[0112] 3. The automatic calibration device and method for spectrometers provided by this invention utilizes a volume holographic frequency selection device, which can continuously select monochromatic light, and the theoretical resolution is consistent with the spectral resolution of the light source.

[0113] 4. The automatic calibration device and method for spectrometers provided by the present invention utilizes an automatic calibration algorithm to achieve automatic calibration of the spectrometer. Pixel-wavelength calibration data can be automatically generated and stored in a preset format, which facilitates automatic calibration and data processing by subsequent spectral measurement software.

[0114] 5. The automatic calibration device and method for spectrometers provided by this invention have a high degree of automation and can realize automatic calibration of batch spectrometers.

[0115] 6. The automatic calibration device and method for spectrometers provided by this invention can be integrated into systems that use spectrometers to achieve automated calibration of spectrometers and avoid high-cost manual maintenance.

[0116] 7. The automatic calibration device and method for spectrometers provided by this invention have an automatic calibration function and require no manual maintenance.

[0117] 8. The automatic calibration device and method for spectrometers provided by this invention have a simple structure, low cost, are easy to operate, and require no maintenance.

[0118] 9. The automatic calibration device and method for spectrometers provided by this invention are applicable to the automatic calibration of all spectrometers with dispersive element-camera combinations, and have stronger adaptability and wider versatility.

[0119] A storage medium storing a program file capable of implementing any of the above-mentioned automatic calibration methods for spectrometers.

[0120] A processor for running a program, wherein the program executes any of the above-mentioned automatic calibration methods for spectrometers.

[0121] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0122] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0123] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The system embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of units or modules may be electrical or other forms.

[0124] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0125] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0126] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0127] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A spectrometer auto-calibration device, characterized by, It comprises a light source, an optical isolator, a fiber coupler, a standard reference light source, an adjustable fiber attenuator, a first fiber collimator, a holographic frequency selection module, a second fiber collimator, a beam splitter, an optical interface unit, a to-be-measured spectrometer, a photodetector, an electric mirror driver, an angle-second-level angle encoder, a control module, a communication module, a computer and an image display unit; the holographic frequency selection module comprises an electric mirror and a volume holographic grating; wherein: The light source and the standard reference light source emit light under the control of the control module, and the control module controls the electric mirror to continuously scan in a preset angle range according to a minimum division angle increment of the electric mirror; The control module controls the to-be-measured spectrometer to collect a scanning spectrum signal and upload it to the computer and the image display unit for processing, analysis and display through the communication module; According to the spectrum result displayed by the computer and the image display unit, the adjustable fiber attenuator is adjusted so that the maximum value of the spectrum signal collected by the to-be-measured spectrometer accounts for 50%-99% of the maximum corresponding signal light intensity of the to-be-measured spectrometer; When the signal collected by the photodetector is maximum, the angle-second-level angle encoder records the rotation angle of the electric mirror and the corresponding output wavelength angle at this time; The control module collects the wavelength corresponding spectrum information collected by the to-be-measured spectrometer and the corresponding electric mirror angle information collected by the angle-second-level angle encoder; The control module uploads the wavelength corresponding spectrum information collected by the to-be-measured spectrometer and the corresponding electric mirror angle information collected by the angle-second-level angle encoder to the computer and the image display unit for analysis, processing and display through the communication module, so as to realize automatic wavelength calibration of the to-be-measured spectrometer. The light source is a kind of super-continuous spectrum pulse laser source, which is electrically connected with the control module, has a wider spectrum range than the tunable laser, and generates a wideband continuous spectrum covering the measurement range of the spectrometer.

2. The apparatus of claim 1, wherein, The optical isolator is a kind of passive optical device that allows unidirectional light to pass through, which is connected with the light source and the fiber coupler, and limits the transmission direction of light so that the light can only transmit in one direction.

3. The apparatus of claim 1, wherein, The fiber coupler is a kind of optical passive element, which is used for combining and splitting optical signals, and is connected with the optical isolator, the standard reference light source and the adjustable fiber attenuator, and couples the light emitted by the light source and the standard reference light source into the system optical path for calibration measurement.

4. The apparatus of claim 1, wherein, The standard reference light source comprises a He-Ne laser with fiber output, a monochromatic light in the measurement range of the to-be-measured spectrometer and a quasi-monochromatic light with a bandwidth of ≤0.1 nm, which is connected with the fiber coupler and the control module, is electrically connected with the control module, and provides a narrow linewidth quasi-monochromatic light with a known standard wavelength for calibrating the reference rotation angle of the electric mirror of the holographic frequency selection module.

5. The apparatus of claim 1, wherein, The adjustable fiber attenuator is a kind of optical device that can reduce the energy of optical signals, which is connected with the fiber coupler and the first fiber collimator, and is used for adjusting the light intensity of the spectrometer system.

6. The apparatus of claim 1, wherein, ​ The first fiber collimator is an achromatic lens or an achromatic lens group, which converts the transmission light in the optical fiber into collimated light and is connected with the adjustable optical fiber attenuator. The optical axis of the lens or lens group intersects with the midpoint of the motorized mirror. The first fiber collimator projects the combined light passing through the fiber coupler to the reflection area of the motorized mirror of the holographic frequency selection module through free space optical communication.

7. The apparatus of claim 1, wherein, The holographic frequency selection module selects light of a specific wavelength for high-precision micron-level calibration of the to-be-tested spectrometer. The motorized mirror is one of a galvanometer mirror, a voice coil motor fast mirror, a micro-electromechanical deformable mirror and a piezoelectric ceramic mirror. The motorized mirror is electrically connected with a motorized mirror driver and an angle-second level angle encoder. According to the received signal, the pitch angle of the motorized mirror is adjusted, and the broadband parallel light beam projected by the first fiber collimator is projected onto the volume holographic grating at a set angle. The second fiber collimator is an achromatic lens or an achromatic lens group, which couples the external parallel light into a single-mode optical fiber and is connected with a beam splitter and a holographic frequency selection module through free space optical communication, and is used for receiving the reflected light of the corresponding wave band reflected by the holographic grating.

8. The apparatus of claim 1, wherein, The beam splitter is an optical element for splitting a light beam into two or more light beams. The beam splitter is connected with the second fiber collimator, a photodetector and an optical interface unit, and splits the light beam collected by the second fiber collimator according to the light intensity ratio of the photodetector and the optical interface unit. The optical interface unit is a fiber interface or a free light alignment system, which is connected with the beam splitter and provides a fiber interface or a free light transmission interface to realize optical connection between the to-be-tested spectrometer and the automatic calibration device of the spectrometer. The photodetector is connected with the beam splitter and a control module, and is used for measuring the light intensity of the standard reference light emitted by the standard reference light source and separated by the beam splitter.

9. The apparatus of claim 1, wherein, The motorized mirror driver is an encoder, which is electrically connected with the control module and the motorized mirror, and is used for receiving the rotation command sent by the control module and driving the motorized mirror to rotate. The angle-second level angle encoder is electrically connected with the control module and the motorized mirror, and returns the current angle value of the to-be-tested object to the control module through an electrical signal, so as to measure the rotation angle of the motorized mirror.

10. A method for automatically calibrating a spectrometer using the automatic calibration device for a spectrometer according to claim 1, characterized by, The method comprises the following steps: The light source and the standard reference light source emit light under the control of the control module. The control module controls the motorized mirror to continuously scan in the preset angle range according to the minimum graduation angle increment of the motorized mirror. The control module controls the to-be-tested spectrometer to collect the scanning spectrum signal and uploads the scanning spectrum signal to a computer and an image display unit for processing, analysis and display. According to the spectrum result displayed by the computer and the image display unit, the adjustable optical fiber attenuator is adjusted so that the maximum value of the spectrum signal collected by the to-be-tested spectrometer accounts for 50%-99% of the maximum corresponding signal light intensity of the to-be-tested spectrometer. When the photodetector collects the maximum signal, the rotation angle of the motorized mirror and the corresponding output wavelength angle at this time are recorded by the angle-second level angle encoder. The control module collects the wavelength corresponding spectrum information collected by the to-be-tested spectrometer and the corresponding motorized mirror angle information collected by the angle-second level angle encoder. The control module uploads the spectral information corresponding to the wavelength collected by the to-be-tested spectrometer and the angle information of the corresponding motorized mirror angle encoder collected by the angle-second level angle encoder to a computer and an image display unit via a communication module for analysis, processing and display, so as to realize automatic wavelength calibration of the to-be-tested spectrometer.

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