Automatic calibration device and method for spectrograph

Abstract

The invention relates to the technical field of measurement, in particular to an automatic calibration device and method for a spectrograph. 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 to be tested, a photoelectric detector, an electric reflector driver, an arc second level angle encoder, a control module and a communication module. A computer and an image display unit. The volume holographic grating is used for selecting a specific wavelength to measure the corresponding relation between the spectrograph pixel and the wavelength, monochromatic light can be continuously selected, and the theoretical resolution is consistent with the spectral resolution of the light source; automatic calibration of the spectrometer is realized by using an automatic calibration method, pixel-wavelength calibration data can be automatically generated and stored in a preset format, automatic calibration and data processing of spectral measurement software are facilitated, and pixel-level wavelength-pixel position registration is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement, and in particular, to an automatic calibration device and method for a spectrometer. Background Art

[0002] A spectrometer has high precision, high sensitivity, rapid on-site measurement, wide application, and simple operation, and is an important general instrument in the field of precision analysis and measurement. Spectrometers are widely used in fields such as astronomy, biomedicine, material identification, chemical engineering environment, national defense technology, energy materials, and industrial inspection. After all spectrometers are manufactured, they must undergo necessary calibration procedures. During the use of spectrometers, due to the combined influence of factors such as environmental vibration, temperature gradient, structural stress release, connection loosening, and structural aging, the corresponding relationship between pixels and wavelengths in the spectrometer will change. At this time, the original calibrated corresponding relationship between pixels and wavelengths is no longer applicable, which will introduce measurement errors to the measurement results. Therefore, recalibration is required.

[0003] Currently, the calibration of spectrometers needs to be completed manually, which is cumbersome and has low precision. Moreover, when using a monochromatic light for calibration, affected by factors such as the spectral bandwidth of the light source, system dispersion, system alignment error, and human operation error, it is difficult to guarantee the accuracy of spectral calibration. In scientific measurement, spectral calibration is crucial, which determines the input-output relationship of the measurement system, assigns the scale value to the measurement system, determines the static indicators of the measurement system, eliminates systematic errors, and improves the correctness of the measurement system.

[0004] There are generally two methods to determine the corresponding relationship between wavelength and pixel: One is to deduce the corresponding relationship between wavelength and pixel through the structural design of the spectrometer. However, this method is not ideal in practical applications, and the error mainly comes from the simplification of various theoretical calculations. In practice, there are multiple error sources such as design error, manufacturing error, and alignment error, which has little guiding significance for practical applications. The second method is to conduct a wavelength calibration experiment. In a wavelength calibration experiment, characteristic spectral lines usually need to be obtained, usually by using a standard light source, a frequency-modulated laser, a monochromator, and a filter with a special wavelength response spectrum. Using a laser or a monochromator for calibration has a high cost, and the spectral line accuracy of the filter is low. When the calibration accuracy requirement is not strict, a standard light source can be used to provide calibration spectral lines.

[0005] The usual approach is to use monochromatic lights with several known wavelengths to calibrate it, and a polynomial is constructed to represent the corresponding functional relationship between pixel position and wavelength. The wavelength calibration methods for spectrometers are as follows:

[0006] 1) Manual calibration method: The spectral lines obtained by the spectrometer are corresponded to the standard spectral lines of the light source through data processing of the relative intensities of known spectral lines, and the corresponding relationship between wavelength and pixel is found.

[0007] 2) Optical equation deduction method: Using the structural parameters of the spectrometer and the optical parameters of the lens, the theoretical correspondence between wavelength and pixel is derived by using the grating equation and geometric optics knowledge. Due to the simplification of multiple links in theoretical calculations and problems such as the alignment error of optical elements, there are large errors, and it is difficult to apply in practice.

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

[0009] The spectral line of each wavelength has a certain pixel width (determined by the resolution of the spectrometer). The position corresponding to the spectral line covers multiple consecutive pixel points, and the pixel position corresponding to the peak point of the spectral line is the pixel position corresponding to that wavelength. In the traditional calibration method, manually selecting the spectral line fitting function has a large fitting error.

[0010] The function fitting methods for manually selecting spectral lines mainly include: parameter fitting method, maximum value method, centroid method, interpolation method, Gaussian fitting method, polynomial fitting method, etc. The fitting accuracy of the parameter fitting method is directly related to the selected function. The sampling points of the maximum value method cannot guarantee to sample 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 process of the interpolation method is difficult and the results are prone to errors. The output spectral line shape of the Gaussian fitting method no longer follows the Gaussian function distribution and has errors. The polynomial fitting will ignore the detailed shape of the spectral line. Summary of the Invention

[0011] The embodiments of the present invention provide a spectrometer automatic calibration device and method to solve the technical problems that the spectrometer cannot be automatically calibrated and the calibration process is complex.

[0012] According to an embodiment of the present invention, a spectrometer automatic calibration device is provided, including: 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 mirror, a volume holographic grating, a second optical fiber collimator, a beam splitter, an optical interface unit, a spectrometer to be measured, a photodetector, an electric mirror 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, and the control module controls the electric mirror to continuously scan within a preset angle range according to the minimum division angle increment of the electric mirror;

[0014] The control module controls the spectrometer to be measured to collect the scanned spectral signal and upload it to the computer and the image display unit through the communication module for processing, analysis, and display;

[0015] Adjust the tunable fiber attenuator according to the spectral results displayed by the computer and the image display unit so that the maximum value of the spectral signal collected by the spectrometer under test accounts for 50%-99% of the maximum corresponding signal light intensity of the spectrometer under test;

[0016] When the signal collected by the photodetector is the largest, the angular encoder at the arcsecond level records the rotation angle of the motorized mirror and the corresponding output wavelength angle at this time;

[0017] The control module collects the spectral information corresponding to the wavelength collected by the spectrometer under test and the angle information of the corresponding motorized mirror collected by the angular encoder at the arcsecond level;

[0018] The control module uploads the spectral information corresponding to the wavelength collected by the spectrometer under test and the angle information of the corresponding motorized mirror collected by the angular encoder at the arcsecond level to the computer and the image display unit via the communication module for analysis, processing and display, so as to realize the automatic wavelength calibration of the spectrometer under test.

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

[0020] Further, the optical isolator is a passive optical device that only allows unidirectional light to pass through. It is fiber-connected to the light source and the fiber coupler, restricts the transmission direction of light, and enables light to be transmitted in only one direction.

[0021] Further, the fiber coupler is an optical passive component used to realize the combining and splitting of optical signals. It is fiber-connected to the optical isolator, the standard reference light source, and the tunable 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.

[0022] Further, the standard reference light source includes a He-Ne laser output by fiber, a monochromatic light within the measurement range of the spectrometer under test, and a quasi-monochromatic light with a bandwidth ≤ 0.1 nm. It is set between the fiber coupler and the control module and is fiber-connected to the fiber coupler and electrically connected to the control module, providing a narrow-linewidth quasi-monochromatic light with a known standard wavelength for calibrating the reference rotation angle of the motorized mirror of the holographic frequency selection module.

[0023] Further, the tunable fiber attenuator is an optical device that can reduce the energy of optical signals. It is fiber-connected to the fiber coupler and the first fiber collimator and is used to adjust the light intensity of the spectrometer system;

[0024] The first fiber collimator is an achromatic lens or an achromatic lens group, which converts the transmitted light in the optical fiber into collimated light for output, and is fiber-connected to the adjustable optical fiber attenuator. The optical axis of the lens or lens group intersects the midpoint of the galvanometric mirror. The first fiber collimator projects the combined light passing through the fiber coupler onto the reflection area of the galvanometric mirror of the holographic frequency selection module in a collimated and expanded manner for free space optical communication.

[0025] Furthermore, the holographic frequency selection module includes a galvanometric mirror and a volume holographic grating, which selects light of a specific wavelength for high-precision micron-level calibration of the spectrometer to be measured;

[0026] The galvanometric mirror is one of a vibrating mirror, a voice coil motor fast steering mirror, a microelectromechanical deformable mirror, and a piezoelectric ceramic mirror. It is electrically connected to the galvanometric mirror driver and an angular second-level angle encoder, and adjusts the pitch angle of the galvanometric mirror according to the received signal, and projects the broadband parallel light 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 optical fiber, is fiber-connected to the beam splitter, and communicates with the holographic frequency selection module through free space optical communication, and is used to receive the reflected light of the corresponding wavelength band reflected by the holographic grating.

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

[0029] The optical interface unit is a fiber interface or a free light alignment system, which is fiber-connected to the beam splitter and provides a fiber interface or a free light transmission interface to realize the optical connection between the spectrometer to be measured and the spectrometer automatic calibration device;

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

[0031] Furthermore, the galvanometric mirror driver is an encoder, which is electrically connected to the control module and the galvanometric mirror, and is used to receive the rotation command issued by the control module and drive the galvanometric mirror to rotate;

[0032] The angular second-level angle encoder is electrically connected to the control module and the galvanometric mirror, and returns the current angle value of the object to be measured to the control module through an electrical signal to measure the rotation angle of the galvanometric mirror.

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

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

[0035] The control module controls the spectrometer under test to collect the scanned spectral signal and upload it to the computer and the image display unit through the communication module for processing, analysis, and display;

[0036] According to the spectral result displayed by the computer and the image display unit, adjust the adjustable optical fiber attenuator so that the maximum value of the spectral signal collected by the spectrometer under test accounts for 50%-99% of the maximum corresponding signal light intensity of the spectrometer under test;

[0037] When the signal collected by the photodetector is the largest, the angular second-level angle encoder records the rotation angle of the electric mirror at this time and the corresponding output wavelength angle;

[0038] The control module collects the spectral information corresponding to the wavelength collected by the spectrometer under test and the corresponding electric mirror angle information collected by the angular second-level angle encoder;

[0039] The control module uploads the spectral information corresponding to the wavelength collected by the spectrometer under test and the corresponding electric mirror angle information collected by the angular second-level angle encoder to the computer and the image display unit through the communication module for analysis, processing, and display, realizing the automatic calibration of the wavelength of the spectrometer under test.

[0040] A storage medium stores a program file capable of implementing the spectrometer automatic calibration method described in any one of the above.

[0041] A processor is used to run a program. When the program runs, it executes the spectrometer automatic calibration method described in any one of the above.

[0042] In the spectrometer automatic calibration device and method according to the embodiments of the present invention, a volume holographic grating is used to select a specific wavelength to determine the correspondence between the pixels and the wavelength of the spectrometer. Monochromatic light can be continuously and accurately selected, and the theoretical resolution is consistent with the spectral resolution of the light source. The automatic calibration of the spectrometer is realized by using the automatic calibration method. The pixel-wavelength calibration data can be automatically generated and stored in a preset format, which is convenient for the automatic calibration and data processing of the spectral measurement software, realizing the pixel-level wavelength-pixel position registration, and providing a spectrometer automatic calibration method with high measurement efficiency and simple measurement. Description of the Drawings

[0043] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

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

[0045] Figure 2 It is a schematic structural diagram of the holographic frequency selection module in the present invention.

[0046] Explanation of the reference numerals in the drawings:

[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 - Electric mirror, 702 - Volume holographic grating, 8 - Second fiber optic collimator, 9 - Beam splitter, 10 - Optical interface unit, 11 - Spectrometer to be measured, 12 - Photoelectric detector, 13 - Electric mirror driver, 14 - Angular second-level angle encoder, 15 - Control module, 16 - Communication module, 17 - Computer and image display unit. Specific implementation manners

[0048] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0049] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0050] In order to solve the problem that the spectrometer cannot be automatically calibrated and the calibration process is complex, the present invention provides an automatic calibration device and method for a spectrometer, which can achieve wavelength-pixel position registration at the pixel level.

[0051] The technical problem to be solved by the present invention is to use a volume holographic grating to select a specific wavelength to measure the correspondence between the pixels and wavelengths of a spectrometer, which can continuously select a monochromatic light accurately, and the theoretical resolution is consistent with the spectral resolution of the light source; an automatic calibration method is used to realize the automatic calibration of the spectrometer, and the pixel-wavelength calibration data can be automatically generated and stored in a preset format, which is convenient for the spectral measurement software to automatically calibrate and process data, realizing the wavelength-pixel position registration at the pixel level, and providing an automatic calibration device and method for a spectrometer with high measurement efficiency and simple measurement.

[0052] In Figure 1 this embodiment, the device for automatically calibrating a spectrometer includes: a 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, a motorized mirror 701, a volume holographic grating 702, a second optical fiber collimator 8, a beam splitter 9, an optical interface unit 10, a spectrometer to be measured 11, a photodetector 12, a motorized mirror driver 13, an angular second-level angle encoder 14, a control module 15, a communication module 16, and a computer and image display unit 17.

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

[0054] The optical isolator 2 is a passive optical device that only allows unidirectional light to pass through, fiber-connected to the light source 1 and the optical fiber coupler 3, restricting the transmission direction of light so that light can only be transmitted in one direction. The function of the optical isolator 2 is to prevent the adverse effects on the light source and the optical path system caused by the backward transmitted light generated in the system optical path for various reasons.

[0055] It can be understood that the optical isolator 2 prevents the backward transmitted light generated in the system optical path for various reasons from passing along the light source 1, the control module 15, the communication module 16 to the computer and image display unit 17, affecting the result of the computer and image display unit 17 analyzing and processing the returned signal.

[0056] The optical fiber coupler 3 is an optical passive component used to realize the combining and splitting of optical signals, fiber-connected to the optical isolator 2, the standard reference light source 4, and the adjustable optical fiber attenuator 5, and coupling the light emitted by the light source 1 and the standard reference light source 4 into the system optical path for calibration measurement. The function of the optical fiber coupler 3 is to couple the light emitted by the supercontinuum light source 1 and the standard reference light source 4 into the system optical path for subsequent calibration measurement.

[0057] The standard reference light source 4 includes one of a He-Ne laser with fiber output, monochromatic light within the measurement range of the spectrometer to be measured, and quasi-monochromatic light with a bandwidth ≤ 0.1 nm. It is arranged between the fiber coupler 3 and the control module 15, fiber-connected to the fiber coupler 3 and electrically connected to the control module 15, providing a narrow-linewidth quasi-monochromatic light with a known standard wavelength for calibrating the reference rotation angle of the galvanometric mirror 701 of the holographic frequency selection module 7.

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

[0059] The adjustable fiber optic attenuator 5 is an optical device that can reduce the energy of the optical signal. It is fiber-connected to the fiber coupler 3 and the first fiber collimator 6, and is used 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 to avoid overexposure of the system caused by the light intensity measured by the camera of the spectrometer to be measured reaching the saturation state, thereby introducing measurement errors.

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

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

[0062] The holographic frequency selection module 7 includes a galvanometric mirror 701 and a volume holographic grating 702, and selects light of a specific wavelength for high-precision micron-level calibration of the spectrometer 11 to be measured.

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

[0064] Optionally, the galvanometric mirror 701 is a galvanometer, a voice coil motor fast steering mirror, a microelectromechanical deformable mirror, or a piezoelectric ceramic mirror.

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

[0066] As Figure 2 , the volume holographic grating 702 reflects the light corresponding to the wavelength band Δλ(θ) at the angle θ between the incident light and the k-axis, and transmits the light of the remaining wavelength bands. The function of the volume holographic grating 702 is to select the light of a specific wavelength that matches the light incident at a specific angle by the electro-optic mirror 701, reflect the light of the specific wavelength to the second fiber collimator 8, and be received by the second fiber collimator 8 and coupled into the fiber optic system.

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

[0068] Optionally, the lens or lens group used in the second fiber collimator 8 belongs to 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 of light, is fiber-connected to the second fiber collimator 8, the photodetector 12, and the optical interface unit 10, and splits the light beam collected by the second fiber collimator 8 according to the light intensity ratio of the photodetector 13 to the optical interface unit 11.

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

[0071] Among them, the light intensity ratio is 1:99 - 50:50.

[0072] The optical interface unit 10 is a fiber optic interface or a free light alignment system, is fiber-connected to the beam splitter 9, and provides a fiber optic interface or a free light transmission interface to realize the optical connection between the spectrometer 11 to be measured and the spectrometer automatic calibration device. The function of the spectrometer 11 to be measured is to provide the system to be calibrated.

[0073] The spectrometer 11 to be measured is used to decompose the light with complex components into spectral lines, is electrically connected to the control module 15, and is used to provide the system to be calibrated. The function of the spectrometer 11 to be measured is to provide the system to be calibrated.

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

[0075] The electric mirror driver 13 is an encoder, which is electrically connected to the control module 15 and the electric mirror 701, and is used to receive the rotation command issued by the control module 15 and drive the electric mirror 701 to rotate. The function of the electric mirror driver 13 is to receive the specific rotation angle command issued by the control module 15 and drive the electric mirror 701 to achieve the preset rotation.

[0076] The arcsecond-level angle encoder 14 is electrically connected to the control module 15 and the electric mirror 701, and returns the current angle value of the object to be measured to the control module 16 through an electrical signal to measure the rotation angle of the electric mirror 701. The function of the arcsecond-level angle encoder 14 is to collect and measure the rotation angle of the electric mirror 701.

[0077] The control module 15 is an encoder, which is electrically connected to the light source 1, the standard reference light source 4, the spectrometer to be measured 11, the photodetector 12, the electric mirror driver 13, and the arcsecond-level angle encoder 14, and is used to control the operations of the light source 1, the standard reference light source 4, the spectrometer to be measured 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, 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 the data collected by the calibration system.

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

[0081] Step 1: The light source 1 and the standard reference light source 4 emit light under the control of the control module 15, and the control module 15 controls the electric mirror 701 to be at a preset angle within the selectable range (that is, covering all angles corresponding within the range of the cut-off wavelength λ i (i = 1, 2)) of the light emitted by the light source 1), and continuously scan according to the minimum graduation angle increment of the electric mirror 701. Specifically,

[0082] Set the spectral range of the broadband continuous spectrum generated by the light source 1 to cover the measurement range of the spectrometer to be measured 11 as [λ1, λ2], and the range of the incident beam angle on the volume holographic grating 702 is [θ1, θ2].

[0083] According to the grating equation:

[0084] 2nΛcosθ1 = λ1

[0085] 2nΛcosθ1 = λ2 (1)

[0086] From the geometric relationship, it can be obtained that:

[0087]

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

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

[0090] θ i (i = 1, 2): are the incident angles corresponding to the reflection wavelengths of λ i (i = 1, 2) respectively;

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

[0092] is the angle between the reflecting surface of the motorized mirror and the optical axis direction of the volume holographic grating.

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

[0094] Step 3: According to the spectral results displayed by the computer and the image display unit 17, adjust the adjustable optical fiber attenuator 5 so that the maximum value of the spectral signal collected 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 Step 1 and Step 2. When the signal collected by the photodetector 12 is the largest, the angular encoder 14 at the arcsecond level records the rotation angle of the motorized mirror 701 at this time as The angle corresponding to the output wavelength at this time is θ reference .

[0096] Set the initial setting angle error of the motorized mirror 701 as According to the geometric relationship, there is:

[0097]

[0098] Step 5: Repeat Step 1 and Step 2 2 - 1000 times, and the control module 15 simultaneously collects the wavelength λ collected by the spectrometer under test 11 jThe corresponding spectral information and the corresponding motorized mirror angle information collected by the arcsecond-level angle encoder 14 Then there is:

[0099]

[0100] Step 6: The control module 15 will simultaneously collect the wavelength λ collected by the spectrometer 11 to be measured j The corresponding spectral information and the corresponding motorized mirror angle information collected by the arcsecond-level angle encoder 14 And upload it to the computer and image display unit 17 via the communication module 16 for analysis, processing, and display. The computer and image display unit 17 calculate that the rotation angle of the motorized mirror 701 is The corresponding pixel mathematical statistical estimation position of the spectral maximum intensity value is When The closest neighboring integer N j Record the corresponding rotation angle of the motorized mirror 701 at this time

[0101] Step 7: When N j Is the closest neighboring integer, record the corresponding rotation angle of the motorized mirror 701 at this time The mathematical statistical expectation of the beam incident angle of the corresponding volume holographic grating 702 is Then there is:

[0102]

[0103] The mathematical expectation of the central wavelength of the incident light collected by the spectrometer 11 to be measured is

[0104]

[0105] Then the acquisition camera pixel N of the spectrometer 11 to be measured j The correspondence f(N j ) with the wavelength of the incident light is:

[0106]

[0107] And record the correspondence f(N j Of the acquisition camera pixel N of the spectrometer 11 to be measured with the wavelength of the incident light j ) into the computer and image display unit 17 to achieve automatic wavelength calibration of the spectrometer 11 to be measured.

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

[0109] The present invention is used for automatically calibrating a spectrometer. Compared with the existing measurement and calibration devices, the present 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 promoted and used.

[0110] 1. The spectrometer automatic calibration device and method provided by the present invention avoid fitting the light source spectrum, and the calibration result has no fitting error and is not affected by the shape of the light source spectrum.

[0111] 2. The spectrometer automatic calibration device and method provided by the present invention have free light and fiber optic optical docking interfaces, and have a wider applicability.

[0112] 3. The spectrometer automatic calibration device and method provided by the present invention utilize a volume holographic frequency selection device, which can continuously select a monochromatic light accurately, and the theoretical resolution is consistent with the light source spectral resolution.

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

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

[0115] 6. The spectrometer automatic calibration device and method provided by the present invention can be integrated into the system of the application spectrometer to realize automatic calibration of the automatic spectrometer and avoid high-cost manual maintenance.

[0116] 7. The spectrometer automatic calibration device and method provided by the present invention have an automatic calibration function and do not require manual maintenance.

[0117] 8. The spectrometer automatic calibration device and method provided by the present invention have a simple structure, low cost, are easy to operate, and are maintenance-free.

[0118] 9. The spectrometer automatic calibration device and method provided by the present invention are applicable to the automatic calibration of all spectrometers in the form of a combination of a dispersive element and a camera, and have stronger adaptability and wider versatility.

[0119] A storage medium stores a program file capable of implementing any one of the above spectrometer automatic calibration methods.

[0120] A processor is used to run a program, and when the program runs, it executes any one of the above spectrometer automatic calibration methods.

[0121] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0122] In the above embodiments of the present invention, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0123] In several embodiments provided by the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the system embodiments described above are merely illustrative. For example, the division of units can be a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the couplings or direct couplings or communication connections shown or discussed with each other can be through some interfaces. The indirect couplings or communication connections of units or modules can be in electrical or other forms.

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

[0125] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0126] If the integrated unit is implemented in the form of 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 this 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 for causing a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the methods in the various embodiments of the present invention. The foregoing storage medium includes: USB flash drives, read-only memories (ROMs), random access memories (RAMs), mobile hard disks, magnetic disks or optical discs and other various media that can store program codes.

[0127] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An automatic calibration device for a spectrometer, characterized in that, Including: 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 mirror, a volume holographic grating, a second optical fiber collimator, a beam splitter, an optical interface unit, a spectrometer to be measured, a photodetector, an electric mirror driver, an angular second-level angle encoder, a control module, a communication module, a computer, and an image display unit; 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 within a preset angle range according to the minimum graduation angle increment of the electric mirror; The control module controls the spectrometer to be measured to collect the scanned spectral signal and upload it to the computer and the image display unit through the communication module for processing, analysis, and display; According to the spectral result displayed by the computer and the image display unit, adjust the adjustable optical fiber attenuator so that the maximum value of the spectral signal collected by the spectrometer to be measured accounts for 50%-99% of the maximum corresponding signal light intensity of the spectrometer to be measured; When the signal collected by the photodetector is the largest, the angular 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 spectral information corresponding to the wavelength collected by the spectrometer to be measured and the corresponding electric mirror angle information collected by the angular second-level angle encoder; The control module uploads the spectral information corresponding to the wavelength collected by the spectrometer to be measured and the corresponding electric mirror angle information collected by the angular second-level angle encoder to the computer and the image display unit through the communication module for analysis, processing, and display, realizing the automatic wavelength calibration of the spectrometer to be measured.

2. The automatic calibration device for a spectrometer according to claim 1, characterized in that, The light source is a supercontinuum pulsed laser light source, electrically connected to the control module, having a spectral range wider than that of a tunable laser, and generating a broadband continuous spectrum covering the measurement range of the spectrometer.

3. The automatic calibration device for a spectrometer according to claim 1, wherein The optical isolator is a passive optical device that only allows unidirectional light to pass through, fiber-connected to the light source and the optical fiber coupler, restricting the transmission direction of light so that light can only be transmitted in one direction.

4. The automatic calibration device for a spectrometer according to claim 1, wherein The optical fiber coupler is an optical passive component used to realize the combination and splitting of optical signals, fiber-connected to the optical isolator, the standard reference light source, and the adjustable optical fiber attenuator, and coupling the light emitted by the light source and the standard reference light source into the system optical path for calibration measurement.

5. The automatic calibration device for a spectrometer according to claim 1, wherein, The standard reference light source includes a He-Ne laser with fiber output, a monochromatic light within the measurement range of the spectrometer to be measured, or a quasi-monochromatic light with a bandwidth ≤ 0.1 nm. It is set between the optical fiber coupler and the control module, fiber-connected to the optical fiber coupler, and electrically connected to the control module, providing 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.

6. The automatic calibration device for a spectrometer according to claim 1, wherein, The adjustable optical fiber attenuator is an optical device that can reduce the energy of optical signals, fiber-connected to the optical fiber coupler and the first optical fiber collimator, and is used to adjust the light intensity of the spectrometer system; The first fiber collimator is an achromatic lens or an achromatic lens group, which converts the transmitted light in the optical fiber into collimated light for output, is fiber-connected to the adjustable fiber attenuator, and the optical axis of the lens or lens group intersects with the midpoint of the galvanometric mirror. The first fiber collimator projects the combined light passing through the fiber coupler onto the reflection area of the galvanometric mirror of the holographic frequency selection module in a collimated and expanded manner for free space optical communication.

7. The automatic calibration device for a spectrometer according to claim 1, characterized in that, The holographic frequency selection module includes a galvanometric mirror and a volume holographic grating, which selects light of a specific wavelength for high-precision micron-level calibration of the spectrometer to be measured; The galvanometric mirror is one of a vibrating mirror, a voice coil motor fast steering mirror, a microelectromechanical deformable mirror, and a piezoelectric ceramic mirror. It is electrically connected to the galvanometric mirror driver and the angular second-level angle encoder, and adjusts the pitch angle of the galvanometric mirror according to the received signal, and projects the broadband parallel light beam projected by the first fiber collimator onto the volume holographic grating at a set angle; The second fiber collimator is an achromatic lens or an achromatic lens group, which couples external parallel light into a single-mode optical fiber, is fiber-connected to the beam splitter and communicates with the holographic frequency selection module through free space optical communication, and is used to receive the reflected light of the corresponding wavelength band reflected by the holographic grating.

8. The automatic calibration device for a spectrometer according to claim 1, characterized in that The beam splitter is an optical element that divides a beam of light into two or more beams of light. It is fiber-connected to the second fiber collimator, the photodetector, and the optical interface unit, and divides the light beam collected by the second fiber collimator according to the light intensity ratio of the photodetector to the optical interface unit; The optical interface unit is a fiber interface or a free light alignment system, which is fiber-connected to the beam splitter and provides a fiber interface or a free light transmission interface to realize the optical connection between the spectrometer to be measured and the spectrometer automatic calibration device; The photodetector is fiber-connected to the beam splitter and electrically connected to the control module, and is used to measure the light intensity of the standard reference light emitted by the standard reference light source separated by the beam splitter.

9. The automatic calibration device for a spectrometer according to claim 1, characterized in that The galvanometric mirror driver is a kind of encoder, which is electrically connected to the control module and the galvanometric mirror, and is used to receive the rotation command issued by the control module and drive the galvanometric mirror to rotate; The angular second-level angle encoder is electrically connected to the control module and the galvanometric mirror, and returns the current angle value of the object to be measured to the control module through an electrical signal to measure the rotation angle of the galvanometric mirror.

10. A method for automatically calibrating a spectrometer using the spectrometer automatic calibration device according to claim 1, characterized in that, It includes the following steps: The light source and the standard reference light source emit light under the control of the control module, and the control module controls the galvanometric mirror to continuously scan within a preset angle range according to the minimum division angle increment of the galvanometric mirror; The control module controls the spectrometer to be measured to collect the scanned spectral signal and upload it to the computer and the image display unit through the communication module for processing, analysis, and display; According to the spectral result displayed by the computer and the image display unit, adjust the adjustable fiber attenuator so that the maximum value of the spectral signal collected by the spectrometer to be measured accounts for 50%-99% of the maximum corresponding signal light intensity of the spectrometer to be measured; When the signal collected by the photodetector is the largest, the angular second-level angle encoder records the rotation angle of the galvanometric mirror and the corresponding output wavelength angle at this time; The control module collects the spectral information corresponding to the wavelength collected by the spectrometer to be measured and the angular information of the corresponding galvanometric mirror collected by the angular second-level angle encoder; The control module will simultaneously collect the spectral information corresponding to the wavelengths collected by the spectrometer to be measured and the angular information of the corresponding motorized mirror collected by the arcsecond-level angle encoder, and upload them to the computer and the image display unit via the communication module for analysis, processing, and display, so as to achieve automatic wavelength calibration of the spectrometer to be measured.

Images