Multi-working-mode switching and closed-loop calibration system and method of near-infrared spectrometer

Abstract

The invention discloses a multi-working-mode switching and closed-loop calibration system and method for a near-infrared spectrometer, and the system comprises an integrated rotary table module, a dual-drive module, a sensing and feedback module, a control and execution module and a wavelength calibration interface module, and achieves the rapid and automatic switching of multiple working modes and the automation of wavelength calibration. The positioning precision of the system is improved through closed-loop control and a differential algorithm; and an automatic error correction function is achieved, and long-term use reliability is guaranteed. And an electromagnetic brake locking mechanism is adopted, so that system jitter in the long exposure process is effectively inhibited, and the reliability of long-term use is ensured. The invention aims to realize rapid and accurate switching among multiple working modes, and has the functions of automatic wavelength calibration and mechanical locking so as to meet the requirements of large-scale astronomical patrol on observation efficiency, system stability and data consistency.

Description

Technical Field

[0001] This invention belongs to the field of spectroscopic analysis instrument technology, and particularly relates to a multi-working mode switching and closed-loop calibration system and method for a near-infrared spectrometer. Background Technology

[0002] To achieve wide-band spectral coverage, traditional grating spectrometers often employ a multi-channel design. While this approach can acquire full-band spectral information in a single operation, it is costly, bulky, and poorly suited for applications with limited space and payload. As a cost-effective alternative, a time-series multi-mode approach achieves wide-band coverage through mechanical adjustment of the operating bands and by utilizing multiple exposures and data stitching, demonstrating significant advantages in reducing cost and system size.

[0003] In existing technologies, the mechanical adjustment methods for achieving mode switching mainly include translating the detector, rotating the grating, or a combination of both. However, these methods all have inherent limitations: translating the detector introduces significant off-axis aberrations, leading to a decrease in image quality at the edges of the field of view; simply rotating the grating changes the direction of the diffraction path, requiring simultaneous adjustment of the detector pose to compensate for image plane shift, otherwise defocusing and coma will occur; while the combined adjustment scheme can balance image quality and grating efficiency to some extent, it increases system complexity and control difficulty.

[0004] To address the aforementioned issues, the applicant proposed a differential rotation structure in its earlier patent application CN202510908128.6. This structure fixes the grating, camera, and detector to the same turntable, achieving mode switching through coordinated rotation. This effectively maintains the relative positions of the optical components and improves system stability. However, this solution still has several key problems: it uses open-loop control, limiting positioning accuracy; it lacks automatic calibration functionality, requiring manual intervention after switching; and it lacks an integrated braking and locking mechanism, making it susceptible to external vibration interference during long exposures.

[0005] For applications such as large-scale astronomical surveys that demand extremely high observation efficiency, data quality, and system stability, existing solutions fall short in terms of accuracy, automation, and long-term reliability. Therefore, this invention proposes a system solution integrating "closed-loop control, automatic wavelength calibration, and braking lock," aiming to achieve rapid switching and precise calibration across multiple operating modes with high accuracy, full automation, and high stability. Summary of the Invention

[0006] Purpose of the Invention: To address the problems of low open-loop control accuracy, the need for manual intervention in wavelength calibration, and the lack of effective braking lock affecting system stability in existing grating spectrometers during multi-mode switching, the purpose of this invention is to provide a multi-mode switching and closed-loop calibration system and method for near-infrared spectrometers. The aim is to achieve rapid and accurate switching between multiple operating modes, and to possess automatic wavelength calibration and mechanical locking functions, thereby meeting the requirements of large-scale astronomical surveys for observation efficiency, system stability, and data consistency.

[0007] Technical solution: The present invention provides a multi-mode switching and closed-loop calibration system for a near-infrared spectrometer, comprising: An integrated turntable module includes a turntable base plate and a working turntable mounted on the base plate via a turntable rotation axis. The working turntable integrates a diffraction grating, a camera, and a detector, forming an integrated optical platform. The dual-drive module includes a rotary motor for the diffraction grating and a rotary motor for the work turntable, which are used to drive the diffraction grating to rotate independently around the central axis and to drive the work turntable to rotate as a whole around the central axis, respectively. The sensing and feedback module includes a grating ruler and a matching reading head mounted on the rotary axis of the turntable for real-time measurement of the absolute angle of the turntable, and an encoder integrated inside the grating rotary motor for real-time measurement of the rotation angle of the diffraction grating. The control and execution module includes a main controller, which pre-stores the target grating angle θ corresponding to at least three working modes. g Angle θ with the target turntable t It is used to synchronously control the coordinated movement of two rotary motors according to the differential algorithm based on the external target mode command; the control and execution module also includes an electromagnetic brake installed at the tail end of the turntable, used to lock the turntable after the angle is reached; The wavelength calibration interface module is used to capture the spectrum through an external calibration lamp or a built-in calibration light source after the mode switch is completed, and return the spectral data to the main controller; the main controller corrects the pixel-wavelength mapping relationship based on a standard spectral template to complete closed-loop calibration.

[0008] Furthermore, the grating ruler is an absolute circular grating, which, together with the reading head, constitutes a turntable angle measurement system for realizing closed-loop feedback and control of the turntable angle.

[0009] Furthermore, the main controller employs a composite control algorithm combining PID control and feedforward compensation to synchronously control the two rotating motors.

[0010] Furthermore, the electromagnetic brake is a power-off holding brake type, used to suppress turntable displacement caused by external vibrations during exposure.

[0011] Furthermore, the main controller reads the actual position of the motor in real time through the grating ruler and encoder, and performs zero-position calibration before each switch, forming an automatic correction mechanism for the accumulated error of multiple switches.

[0012] This invention also discloses a switching and calibration method for a multi-mode switching and closed-loop calibration system of a near-infrared spectrometer, comprising the following steps: S1. System initialization: The main controller reads the current raster angle and turntable angle. S2. Receive the target mode command and call the pre-stored target angle parameter corresponding to θ. g θ t ; S3. The main controller calculates the angle adjustment Δθ between the grating and the turntable based on the differential algorithm. g and Δθ t : Δθ g = θ g _target – θ g _current) Δθ t = (θ t _target – θ t _current) – k×Δθ g Where k is a scaling factor related to the grating equation, θ g _target represents the grating target state angle, θ g _current represents the current state angle of the grating; θ t _target represents the target state angle of the turntable, θ t _current indicates the current state angle of the turntable; S4. The main controller synchronously drives two rotary motors, causing the grating to rotate by Δθ. g At the same time, the turntable rotates Δθ t The differential motion enables precise adjustment of the grating incident angle and re-matching of the diffraction path with the detector. S5. Using the feedback signals from the grating ruler and encoder, when the main controller determines that the angle error is less than the set threshold, the electromagnetic brake is triggered to lock the worktable. S6. Automatic wavelength calibration process: Acquire spectral data of calibration lamp, execute calibration algorithm in main controller, compare measured spectral lines with pre-stored standard spectral template, calculate pixel offset, and correct wavelength-pixel mapping relationship accordingly to complete calibration.

[0013] Furthermore, the proportionality coefficient k ranges from 2 to 4.

[0014] Furthermore, the wavelength calibration algorithm includes: The acquired spectrum is filtered and peaks are extracted. The measured peak position is compared with the corresponding peak position of the standard spectral template to obtain the pixel offset; A correction function is established based on this offset to update the wavelength-pixel mapping relationship in order to reduce wavelength error.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The system achieves rapid automatic switching between multiple working modes and automated wavelength calibration: through pre-stored angle parameters and differential algorithms, the main controller can synchronously drive the two motors to perform coordinated movements, quickly adjusting the optical components to the target working mode; after switching, the wavelength calibration process is started, and spectral acquisition, spectral line intensity analysis and calibration can be completed without manual intervention, greatly improving observation efficiency.

[0016] 2. Improved system positioning accuracy through closed-loop control and differential algorithm: The system uses a high-precision grating ruler and encoder to form a dual-feedback network to monitor the actual angle between the turntable and the grating; the main controller combines this feedback signal with the differential motion model to perform closed-loop control on the two motors, realizing fine adjustment of the grating incident angle and real-time matching of the diffraction optical path, and finally stabilizing the angle positioning accuracy within the set threshold, laying the foundation for high-precision spectral measurement.

[0017] 3. Equipped with automatic error correction function to ensure long-term reliability: Before each switch, the main controller will use the feedback sensor to perform zero-position calibration, actively eliminating the small angle deviation that may be caused by multiple runs, effectively suppressing the accuracy drift that may occur during long-term use, and ensuring that the system can still maintain the initial calibration accuracy and reliability under repeated and frequent mode switching.

[0018] 4. An electromagnetic braking locking mechanism is adopted, which effectively improves the stability during long exposures: After the working turntable is positioned, the system immediately triggers the electromagnetic brake to mechanically lock it, suppressing the turntable displacement caused by external environmental vibration or residual micro-motion of the motor, thereby ensuring the stability of the optical system and the imaging quality during long astronomical exposures.

[0019] In summary, this invention deeply integrates high-precision motion control, wavelength calibration, and mechanical stability design to form a complete solution, enabling the spectrometer to meet the needs of high-end astronomical observation and other application scenarios in terms of efficiency, accuracy, and stability. Attached Figure Description

[0020] Figure 1: Schematic diagram of the system's three-dimensional structure; In the diagram, 1 is the base plate, 2 is the turntable rotation shaft, 3 is the working turntable, 4 is the grating rotary motor, 5 is the turntable rotary motor, 6 is the grating ruler, 7 is the reading head, and 8 is the electromagnetic brake. Figure 2 Schematic diagram of differential motion principle; Figure 3 Control method flowchart; Figure 4 Wavelength calibration algorithm flowchart; Figure 5 Spectral line intensity distribution and wavelength coverage under Mode A; Figure 6 Spectral line intensity distribution and wavelength coverage under Mode B; Figure 7 Spectral line intensity distribution and wavelength coverage in Mode C; Figure 8 : Spectrometer image plane stability test results. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] Example: Multi-mode switching and calibration of LAMOST near-infrared spectrometer This embodiment uses the LAMOST near-infrared spectrometer as the application. The system pre-stores the grating angle θg and turntable angle θg corresponding to three working modes. t The details are as follows: Pattern A: θ g =9.7°, θ t =14.9°, corresponding to a theoretical wavelength coverage range of 860–980 nm; Pattern B: θ g =10.8°, θ t =16.0°, corresponding to a theoretical wavelength coverage range of 954–1073 nm; Pattern C: θ g =11.8°, θ t =17.0°, corresponding to a theoretical wavelength coverage range of 1036–1156 nm.

[0023] Taking switching from mode A to mode B as an example, the specific steps are as follows: 1. The main controller receives the Mode B command and calculates the angular motion: Δθ g = 10.8° - 9.7° = +1.1° Δθ t = 16.0° - 14.9° - 3 × 1.1° = -2.2° The constant k takes the value of 3, and the sign of the angle value indicates the direction of rotation. The specific directional relationship is defined by the system coordinate system.

[0024] 2. The main controller synchronously drives the turntable rotary motor and the grating rotary motor to achieve a grating rotation of +1.1° while the working turntable rotates -2.2°, thus completing the differential adjustment.

[0025] 3. Angle information is fed back in real time through the grating ruler and encoder. When the error is less than the set threshold of 0.01°, the main controller triggers the electromagnetic brake to lock the turntable.

[0026] 4. Automatic wavelength calibration process: control the calibration lamp to light up, capture the calibration lamp spectrum, extract the position of characteristic spectral lines, match them with the standard template, calculate the pixel offset, and update the wavelength-pixel mapping relationship accordingly to achieve closed-loop calibration.

[0027] 5. After calibration, the system records the switching log and enters the observation state.

[0028] To further verify the system stability, image drift tests were conducted on the spectrometer during continuous nights of observation. The results showed that the image plane drift rate was less than 0.01 Å / h, meeting the stability requirements for long-exposure observation.

[0029] like Figure 5 As shown, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents spectral line intensity; (b) is the spectral line intensity distribution of the calibrated lamp spectrum dispersion direction extracted under mode A, and (a) is the wavelength calibration result after matching the spectral line intensity distribution with the standard template. The actual wavelength coverage range under mode A is 853-981 nm.

[0030] like Figure 6 As shown, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents spectral line intensity; (b) is the spectral line intensity distribution of the calibrated lamp spectrum dispersion direction extracted under mode B, and (a) is the wavelength calibration result after matching the spectral line intensity distribution with the standard template. The actual wavelength coverage range under mode B is 945-1072 nm.

[0031] like Figure 7 As shown, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents spectral line intensity; where (b) is the spectral line intensity distribution in the dispersion direction of the calibration lamp spectrum extracted under mode C, and (a) is the wavelength calibration result after matching the spectral line intensity distribution with the standard template. The actual wavelength coverage range under mode B is 1027-1154 nm.

[0032] like Figure 8As shown, the horizontal axis represents time (in hours), and the vertical axis represents wavelength drift (in Å). Within one observation night, the wavelength drift of the spectrometer was accumulated over a continuous 6 hours. The wavelength drift amplitude was within ±0.01 Å, indicating excellent stability.

Claims

1. A multi-mode switching and closed-loop calibration system for a near-infrared spectrometer, characterized in that, include: An integrated turntable module includes a turntable base plate and a working turntable mounted on the base plate via a turntable rotation axis. The working turntable integrates a diffraction grating, a camera, and a detector, forming an integrated optical platform. The dual-drive module includes a rotary motor for the diffraction grating and a rotary motor for the work turntable, which are used to drive the diffraction grating to rotate independently around the central axis and to drive the work turntable to rotate as a whole around the central axis, respectively. The sensing and feedback module includes a grating ruler and a matching reading head mounted on the rotary axis of the turntable for real-time measurement of the absolute angle of the turntable, and an encoder integrated inside the grating rotary motor for real-time measurement of the rotation angle of the diffraction grating. The control and execution module comprises a main controller, which pre-stores target grating angles θ corresponding to at least three working modes g and the target turntable angle θ t and is used for synchronously controlling coordinated movement of the two rotary motors according to a differential algorithm according to an external target mode instruction; the control and execution module further comprises an electromagnetic brake installed at the tail end of the working turntable, which is used for locking the turntable after the angle is in place. The wavelength calibration interface module is used to capture the spectrum through an external calibration lamp or a built-in calibration light source after the mode switch is completed, and return the spectral data to the main controller; the main controller corrects the pixel-wavelength mapping relationship based on a standard spectral template to complete closed-loop calibration.

2. The multi-mode switching and closed-loop calibration system for a near-infrared spectrometer according to claim 1, characterized in that, The grating ruler is an absolute circular grating, which, together with the reading head, constitutes a turntable angle measurement system for achieving closed-loop feedback and control of the turntable angle.

3. The multi-mode switching and closed-loop calibration system for a near-infrared spectrometer according to claim 1, characterized in that, The main controller employs a composite control algorithm combining PID control and feedforward compensation to synchronously control the two rotating motors.

4. The multi-mode switching and closed-loop calibration system for a near-infrared spectrometer according to claim 1, characterized in that, The electromagnetic brake is a power-off holding brake type, used to suppress turntable displacement caused by external vibrations during exposure.

5. The multi-mode switching and closed-loop calibration system for a near-infrared spectrometer according to claim 1, characterized in that, The main controller reads the actual position of the motor in real time through a grating ruler and an encoder, and performs zero-position calibration before each switch, forming an automatic correction mechanism for the accumulated error of multiple switches.

6. A switching and calibration method for a multi-mode switching and closed-loop calibration system based on the near-infrared spectrometer of claim 1, characterized in that, Includes the following steps: S1. System initialization: The main controller reads the current raster angle and turntable angle. S2, receiving target mode instruction, calling pre-stored θ corresponding to target angle parameter g , θ t ; S3, the main controller calculates the angular adjustment amount Δθ of the grating and the turntable according to the differential algorithm g and Δθ t : Δθ g = θ g _target – θ g _current) Δθ t = (θ t _target – θ t _current) – k×Δθ g Where k is a scaling factor related to the grating equation, θ g _target represents the grating target state angle, θ g _current represents the current state angle of the grating; θ t _target represents the target state angle of the turntable, θ t _current indicates the current state angle of the turntable; S4. The main controller synchronously drives two rotating motors, causing the grating to rotate by Δθ. g At the same time, the turntable rotates Δθ t The differential motion enables precise adjustment of the grating incident angle and re-matching of the diffraction path with the detector. S5. Using the feedback signals from the grating ruler and encoder, when the main controller determines that the angle error is less than the set threshold, the electromagnetic brake is triggered to lock the worktable. S6. Automatic wavelength calibration process: Acquire spectral data of calibration lamp, execute calibration algorithm in main controller, compare measured spectral lines with pre-stored standard spectral template, calculate pixel offset, and correct wavelength-pixel mapping relationship accordingly to complete calibration.

7. The method according to claim 6, characterized in that, The proportionality coefficient k ranges from 2 to 4.

8. The method according to claim 6, characterized in that, The wavelength calibration algorithm includes: The acquired spectrum is filtered and peaks are extracted. The measured peak position is compared with the corresponding peak position of the standard spectral template to obtain the pixel offset; A correction function is established based on this offset to update the wavelength-pixel mapping relationship in order to reduce wavelength error.

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