Monochromator capable of calibrating wavelength in real time

Abstract

The utility model relates to the technical field of spectrum analysis instruments, in particular to a monochromator for real-time wavelength calibration, which comprises a shell, a light source module, a light splitting module, a signal acquisition module, an auxiliary calibration module and a feedback control unit, and is characterized in that the signal acquisition module is arranged on a + 1-level diffraction light path; the auxiliary calibration module is arranged on a-1-level diffraction light path and sequentially comprises a standard light filter, a second focus lens and an auxiliary detector along the light path; the driving assembly is used for driving the grating to rotate around the normal axis of the grating; the feedback control unit is connected with the auxiliary detector and the driving assembly through a circuit; and the structural member is fixed on the inner side of the shell and extends along the normal plane of the grating so as to physically isolate the + 1-level diffraction light path from the-1-level diffraction light path, and the problem that real-time calibration cannot be carried out in a traditional spectrum calibration mode can be effectively solved.

Description

A monochromator with real-time wavelength calibration Technical Field

[0001] This utility model relates to the field of spectroscopic analysis instrument technology, specifically to a monochromator with real-time wavelength calibration. Background Technology

[0002] Monochromators are important instruments in material detection and chemical analysis, widely used in scientific research and industrial testing. Before use, their wavelengths require precise calibration. For grating dispersive spectrometers, continuous spectral acquisition primarily employs a mechanical structure to drive the grating for scanning. The wavelength and rotation angle are mapped one-to-one, thus transforming wavelength calibration into grating rotation angle calibration.

[0003] Traditional grating dispersive monochromators rely on external calibration light sources (such as mercury lamps or lasers) for wavelength calibration. Due to mechanical and assembly errors, additional system errors can be introduced when switching light sources. Using standard filter absorption peaks for time-division acquisition and calibration wavelengths may cause certain deviations in motor control between the two scans. At the same time, existing wavelength calibration methods will have a certain impact on the signal acquisition optical path, which may interfere with normal signals. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a monochromator with real-time wavelength calibration, which can effectively solve the problem that real-time calibration is not possible in traditional spectral calibration modes.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a monochromator for real-time wavelength calibration, comprising a housing, and a light source module and a beam splitting module disposed within the housing. The beam splitting module includes a grating disposed on the beam path emitted by the light source module and diffracting the incident beam into +1st order diffracted light and -1st order diffracted light. The monochromator further includes: a signal acquisition module disposed on the +1st order diffracted light path, comprising a first focusing lens and a signal detector in sequence along the light path; an auxiliary calibration module disposed on the -1st order diffracted light path, comprising a standard filter, a second focusing lens and an auxiliary detector in sequence along the light path; a driving component for driving the grating to rotate around its normal axis; a feedback control unit connected to the auxiliary detector and the driving component via a circuit; and a structural component fixed inside the housing and extending along the normal plane of the grating to physically isolate the +1st order diffracted light and the -1st order diffracted light paths.

[0006] Preferably, the partition is located on the diffraction angle bisector of the grating.

[0007] Preferably, the standard filter is disposed on the incident light path of the second focusing lens, and its passband center wavelength matches the spectral response peak of the auxiliary detector.

[0008] Preferably, the feedback control unit integrates an angle compensation calculation circuit, the input of which is connected to the auxiliary detector, and the output is connected to the drive chip of the drive component through a PID controller.

[0009] Preferably, the structural component is a plate-shaped structure, and its material is anodized aluminum alloy.

[0010] Preferably, the driving component includes a grating motor and a grating base that receives the drive of the grating motor; the grating is disposed on the grating base.

[0011] Preferably, the signal detector and the auxiliary detector are symmetrically arranged on both sides of the grating, and the optical path lengths of the center of their photosensitive surfaces from the center of the grating are equal.

[0012] Preferably, the partition is serrated or stepped, with the serrations or steps pointing in the opposite direction to the incident light.

[0013] Compared with the prior art, the beneficial effects of this utility model are:

[0014] 1. By setting a signal acquisition module in the +1st order diffraction optical path and an auxiliary calibration module in the -1st order diffraction optical path, and connecting the feedback control unit to the auxiliary calibration module, calibration is performed using the -1st order diffraction optical path based on the characteristics of grating beam splitting, without affecting the signal acquisition of the +1st order diffraction optical path at all. This ensures that the signal acquisition module is not affected and guarantees the accuracy of the acquired signal.

[0015] 2. By setting a partition between the -1st order diffraction beam and the +1st order diffraction beam, the partition completely isolates the +1st and -1st order optical paths in space, avoiding crosstalk between the ±1st order diffraction beams, ensuring the absorption peak positioning accuracy, and improving the measurement accuracy and reliability of the monochromator. Attached Figure Description

[0016] Figure 1 is a schematic diagram of the internal arrangement of the monochromator of this utility model;

[0017] Figure 2 is a schematic diagram of the grating diffraction of this utility model;

[0018] Figure 3 is a schematic diagram of the monochromator calibration principle of this utility model;

[0019] Figure 4 is a flowchart of the monochromator calibration process of this utility model.

[0020] In the figure: 1 Light source, 2 Aperture stop, 3 First focusing lens, 4 Entrance slit, 5 Collimating lens, 6 Grating, 7 Grating base, 8 Second focusing lens, 9 Signal detector, 10 Standard filter, 11 Third focusing lens, 12 Auxiliary detector. Detailed Implementation

[0021] The specific embodiments of this utility model are described in detail below with reference to the accompanying drawings, so that those skilled in the art can more clearly understand how to practice this utility model. Although this utility model has been described in conjunction with its preferred embodiments, these embodiments are merely illustrative and not intended to limit the scope of this utility model.

[0022] Referring to Figures 1-4, in one embodiment of this utility model, a monochromator for real-time wavelength calibration includes: a housing (not shown in the figures) and a light source module, a beam splitting module, a signal acquisition module, an auxiliary calibration module, and a feedback control unit disposed within the housing. The housing is also provided with a signal output interface.

[0023] The light source module includes a light source 1 that provides the light source, and an aperture stop 2 and a first focusing lens 3 that are correspondingly arranged with the light source 1. The aperture stop 2 and the first focusing lens 3 are used to converge the composite beam emitted by the light source 1 and direct it to the beam splitting module.

[0024] The beam splitting module employs a grating dispersion beam splitting mode. The module includes an entrance slit 4, a collimating lens 5, a grating 6, a grating motor (not shown in the figure), and a grating base 7 driven by the grating motor. The entrance slit 4, collimating lens 5, and grating 6 are positioned along the beam path emitted by the light source 1. The grating 6 is fixedly mounted on the grating base 7, and the operation of the grating motor drives the grating 6 on the grating base 7 to rotate. The light emitted from the light source 1 is converged at the entrance slit 4 by the first focusing lens 3. After being intercepted by the entrance slit 4, the light is collimated by the collimating lens 5. The collimated light then strikes the grating 6, thus dispersing into monochromatic light. During grating 6 dispersion, ±1st order diffraction occurs simultaneously. The +1st order diffraction enters the signal acquisition module, and the -1st order diffraction enters the auxiliary calibration module.

[0025] The signal acquisition module includes a second focusing mirror 8 and a signal detector 9. The signal detector 9 is pre-installed with an exit slit for acquiring valid signals. The signal output interface is used to collimate and output the +1st order diffracted light acquired by the signal acquisition module.

[0026] The auxiliary calibration module includes a standard filter 10, a third focusing lens 11, and an auxiliary detector 12. The standard filter 10 is used to obtain sample absorption peak data and input the data into the feedback control unit. Furthermore, the grating motor is equipped with an encoder, and the feedback signal of the encoder can be connected to the feedback control unit.

[0027] The feedback control unit includes a circuit board, an angle compensation calculation circuit, and a PID control chip integrated on the circuit board. Its output is directly connected to the encoder feedback interface of the grating motor via a circuit, and the input of the circuit is connected to the auxiliary detector 12. The feedback control unit is used to calculate the wavelength deviation between the sample absorption peak data and the standard absorption peak data, and convert the wavelength deviation into an angle deviation. The feedback unit controls the motor to adjust the rotation angle in real time for wavelength calibration. Specifically: signal acquisition and conversion: the detector acquires the light intensity signal and converts it into an analog electrical signal, which is then converted into a digital signal by an ADC. After preprocessing by the signal processing module, the signal is input to the controller; encoder value mapping and wavelength calculation: the grating motor reads the encoder value and associates the digital signal with the encoder value through a mapping relationship; the encoder value is converted into a rotation angle using an algorithm, and further converted into the corresponding wavelength to generate a "wavelength-signal intensity" chart; error calculation and correction: the feature value extraction algorithm identifies the feature absorption peak, compares its corresponding actual wavelength value with the standard value of the preset standard filter, and calculates the error; the error value is converted into a control signal that the motor can receive, driving the motor to adjust the input and achieve real-time wavelength correction.

[0028] Furthermore, in practice, when the grating 6 splits the light, since the ±1st order diffracted light is adjacent and has similar energy, the traditional design easily leads to stray light entering the detector (signal detector 9 or auxiliary detector 12). Therefore, in order to eliminate crosstalk between the ±1st order diffracted light, a partition (not shown in the figure) is also provided inside the housing. The partition is fastened to the housing by welding / bolts and is located at the extension of the normal plane of the grating 6 (i.e., the diffraction angle bisector). It can be understood that the signal acquisition module 9 is set at the end of the +1st order diffracted light path, and the auxiliary calibration module 12 is set at the end of the -1st order diffracted light path. The partition extends along the normal plane of the grating 6, completely isolating the +1st and -1st order light paths in space. The material of the partition can be aluminum alloy with an anodized surface and a thickness of 2-5mm. The partition can rigidly isolate the two light paths and suppress light path offset. For example, if the standard filter 10 needs to detect the characteristic absorption peak of the -1st order diffracted light, the partition can block the +1st order stray light interference and ensure the positioning accuracy of the absorption peak.

[0029] The partition enables the monochromator to achieve high-precision and high-reliability real-time calibration. In one embodiment, from the perspective of saving costs or simplifying the internal space of the monochromator, the partition can also be a structural component inside the housing, which is designed to serve the purpose of blocking.

[0030] In other embodiments, the baffle can be designed as a multi-stage baffle, which can be sawtooth or stepped, with the sawtooth or step pointing in the opposite direction to the incident light, which can effectively prevent scattered light from entering the main optical path and contaminating the signal; the baffle is beneficial for heat conduction, increases the heat dissipation area, and ensures that the operating temperature of the equipment is relatively stable.

[0031] Principle description: After the composite light emitted by the light source 1 passes through the aperture stop 2, it is focused by the first focusing mirror 3 onto the entrance slit 4. After passing through the entrance slit 4, the light beam enters the grating spectroscopy system, and the composite light is decomposed into monochromatic light through the diffraction of the grating 6. At this time, both the ±1 diffractions exist simultaneously. The +1-order diffraction is taken as the effective signal and is focused onto the exit slit through the second focusing mirror 8. A signal detector 9 is arranged behind the exit slit, and the signal detector 9 directly outputs the converted signal to a computer or the next-level device after conversion; the -1-order diffraction is taken as the calibration signal, and its optical path structure is basically the same as that of the +1-order diffraction. A standard filter 10 is arranged in the -1-order diffraction optical path. The characteristic absorption peak spectrum can be obtained through the standard filter 10, and the calibration parameter is calculated through the characteristic absorption spectrum and output to the feedback control unit, thereby realizing the wavelength calibration and calibration functions. The feedback control unit is connected to the grating motor on the auxiliary calibration module and the spectroscopy module. The calibration parameter obtained through the auxiliary calibration module is fed back to the grating motor, and the wavelength is calibrated in real time by controlling the grating motor.

[0032] This solution not only provides a monochromator for real-time wavelength calibration, but also provides a calibration method supporting this monochromator. The specific steps are as follows:

[0033] From the grating dispersion equation:

[0034] ... [Equation 1]

[0035] Where m is the diffraction spectrum order, d is the grating constant, α is the grating incident angle, β is the diffraction angle, and the positive and negative signs depend on the positions of the incident angle and the diffraction angle relative to the normal. The same side is positive and the opposite side is negative.

[0036] For a determined system, for the +1-order diffraction, refer to Figure 2:

[0037] ... [Equation 2]

[0038] ... [Equation 3]

[0039] Thus, it can be obtained:

[0040] ... [Equation 4]

[0041] For the -1-order:

[0042] ... [Equation 5]

[0043] ... [Equation 6]

[0044] Thus, it can be obtained:

[0045] ...[Formula 7]

[0046] Where K and K' are calibration constants in the system. When α rotates to a certain angle, the corresponding signal wavelength λ and calibration wavelength λ' can be obtained, and the wavelength values ​​of +1 and -1 levels can be obtained one-to-one.

[0047] ...[Formula 8]

[0048] At this point, the absorption peak of the standard filter in the -1 level is used as the calibration standard value. When the calibration wavelength λ' shifts, the shift is fed back to the feedback control unit to perform real-time calibration of the rotating motor. This allows for synchronous calibration of the signal wavelength λ without needing to determine whether there is a linear relationship between the wavelength and the angle.

[0049] The correspondence between grating wavelength offset and rotation angle calibration:

[0050] Differentiating λ in Equation 4, we get:

[0051] ...[Formula 9]

[0052] Therefore, the relationship between the offset wavelength and the calibration angle is:

[0053] ...[Formula 10]

[0054] As can be seen from the above technical solution, when the grating disperses the composite light, it simultaneously generates ±1st order diffraction light. The +1st order signal acquisition module and the -1st order auxiliary calibration module are separated by an internal partition. The +1st order performs signal acquisition and processing according to the traditional monochromator mode, while the -1st order acts as a feedback calibration module. Its optical path contains a standard filter to obtain the characteristic absorption peak. The wavelength shift between the characteristic absorption peak and the standard absorption peak is then compared in real time. Using the grating equation, the wavelength shift is inverted into an angular shift, which is then fed back to the grating's rotating motor for real-time wavelength calibration. Since ±1st order diffraction exists simultaneously and scans the wavelength along with the grating rotation, only real-time correction of the -1st order is needed to obtain monochromatic light with extremely high wavelength accuracy for the +1st order. Therefore, this solution effectively solves the problem of real-time calibration in traditional spectral calibration modes.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A monochromator for real-time wavelength calibration, comprising a housing, and a light source module and a beam splitter module disposed within the housing, wherein the beam splitter module includes a grating (6) disposed on the beam path emitted by the light source module and diffracting the incident beam into +1st order diffracted light and -1st order diffracted light, characterized in that, The monochromator further includes: a signal acquisition module, which is set on the +1st order diffraction optical path and includes a first focusing lens (8) and a signal detector (9) in sequence along the optical path; an auxiliary calibration module, which is set on the -1st order diffraction optical path and includes a standard filter (10), a second focusing lens (11) and an auxiliary detector (12) in sequence along the optical path; a driving component, which is used to drive the grating (6) to rotate around its normal axis; a feedback control unit, which is connected to the auxiliary detector (12) and the driving component through a circuit; and a structural component, which is fixed inside the housing and extends along the normal plane of the grating (6) to physically isolate the +1st order diffraction light and the -1st order diffraction optical path.

2. A monochromator with real-time wavelength calibration according to claim 1, characterized in that: The structural component is located on the diffraction angle bisector of the grating (6).

3. A monochromator with real-time wavelength calibration according to claim 1, characterized in that: The standard filter (10) is placed on the incident light path of the second focusing lens (11), and its passband center wavelength matches the spectral response peak of the auxiliary detector (12).

4. A monochromator with real-time wavelength calibration according to claim 1, characterized in that: The feedback control unit integrates an angle compensation calculation circuit. The input of the circuit is connected to the auxiliary detector (12), and the output is connected to the drive chip of the drive component through a PID controller.

5. A monochromator with real-time wavelength calibration according to claim 1, characterized in that: The structural component has a plate-like structure and is made of aluminum alloy with anodized surface treatment.

6. A monochromator with real-time wavelength calibration according to claim 1, characterized in that, The drive assembly includes a grating motor and a grating base that receives the drive of the grating motor; the grating (6) is disposed on the grating base.

7. A monochromator with real-time wavelength calibration according to claim 1, characterized in that: The signal detector (9) and the auxiliary detector (12) are symmetrically arranged on both sides of the grating (6), and the optical path between the center of their photosensitive surfaces and the center of the grating is equal.

8. A monochromator with real-time wavelength calibration according to claim 1, characterized in that, The structural component is serrated or stepped, with the serrations or steps pointing in the opposite direction to the incident light.

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