Convergent light path for solar spectral radiometer and method for adjusting coaxiality of optical axis thereof

Abstract

The application discloses a convergent light path for a solar spectrum radiometer and a light axis coaxial adjustment method thereof, and relates to the field of atmospheric measurement devices. The convergent light path comprises a tracking light cylinder and a measurement light cylinder. The tracking light cylinder is composed of a small hole, an adjusting mechanism, a four-quadrant detector and an amplification and acquisition circuit. The measurement light cylinder is composed of a window sheet, an aperture diaphragm, an off-axis parabolic reflector, a field diaphragm, a stray light elimination diaphragm, a meniscus lens, a neutral density filter and a spectrometer. The method constructs a normalized evaluation index by collecting four-quadrant signals and the weighted integral sum of continuous spectrum intensity of multiple preset reference wave bands in the range of 2-6 micrometers, performs local five-point cross scanning with the current locking point as the center, determines an optimal coaxial point and obtains a target locking feature, and triggers coaxial adjustment again when the evaluation index decreases or when the machine is started. The application can improve the consistency of the measurement light path and the tracking light path and the stability of direct measurement.

Description

Technical Field

[0001] This invention relates to the field of atmospheric measurement devices, and more specifically to a converging optical path for a solar spectroradiometer and a method for coaxial adjustment of its optical axis. Background Technology

[0002] Solar radiometers are widely used in solar radiation measurement, atmospheric remote sensing, and related optical parameter inversion. To achieve stable acquisition of solar radiation signals, existing solar radiometers typically employ a measurement optical path and a tracking optical path. The measurement optical path receives solar radiation and performs spectral measurements, while the tracking optical path senses solar deviation information and drives the turntable to complete solar tracking. For mid-infrared solar spectral radiation measurements, the measurement optical path usually needs to utilize methods such as reflection, convergence, field-of-view limitation, stray light suppression, and light intensity attenuation to achieve effective reception and stable measurement of incident sunlight.

[0003] In existing technologies, solar tracking typically relies on a tracking detector to detect the sun's position in real time and achieves target tracking through turntable adjustments. While this method can achieve automatic solar tracking, in practical applications, there are often assembly and adjustment errors, installation errors, and drift errors after long-term operation between the measurement and tracking optical paths. This results in the geometric center position of the tracking optical path not being completely consistent with the optimal receiving position of the measurement optical path. Consequently, even when the turntable has completed normal tracking, the measurement optical path may not be in its optimal receiving state, thus affecting the stability, repeatability, and accuracy of direct sunlight measurements.

[0004] Furthermore, existing coaxial adjustment methods mostly rely on manual adjustment, external auxiliary tooling, or one-time static assembly and adjustment, making it difficult to balance assembly and adjustment efficiency with the need for online correction during operation. Especially in solar radiation measurement, if the axial deviation between the measurement optical path and the tracking optical path cannot be corrected in time, it can easily lead to a decrease in measurement signal, difficulty in repeated adjustments, and deterioration in consistency after long-term use. Therefore, there is an urgent need for a reasonably structured converging optical path and a corresponding coaxial adjustment method to improve the consistency between the measurement optical path and the tracking optical path, and to enhance the stability and reliability of direct solar radiation measurements. Summary of the Invention

[0005] To address the above technical problems, this invention provides a converging optical path for a solar spectroradiometer and a method for coaxial adjustment of its optical axis. By setting a tracking optical tube and a measuring optical tube on the same probe, the tracking optical tube is used to acquire solar deviation information, and the measuring optical tube is used to complete the convergence and spectral measurement of solar radiation signals. In addition, a measurement evaluation quantity is constructed by combining the continuous spectral intensity of multiple reference bands. Local scanning is performed near the current locking point to determine the optimal correspondence between the measuring optical path and the tracking optical path, thereby achieving online coaxial adjustment of the measuring optical path and the tracking optical path.

[0006] The technical solution of this invention is as follows:

[0007] A converging optical path for a solar spectroradiometer includes a turntable base, a turntable, a probe, a tracking optical tube, and a measuring optical tube. The turntable is mounted on the turntable base, the probe is mounted on the turntable, and both the tracking optical tube and the measuring optical tube are mounted on the probe and rotate synchronously with the turntable. The tracking optical tube receives sunlight and outputs a target deviation signal, while the measuring optical tube receives sunlight and converges the incident sunlight before outputting a measurement signal. The tracking optical tube includes a pinhole, a dovetail adjustment mechanism, a four-quadrant detector, and an amplification and acquisition circuit. The measuring optical tube includes a window, an aperture diaphragm, an off-axis parabolic mirror, a field diaphragm, a stray beam diaphragm, a meniscus lens, a neutral density filter, and a spectrometer. The tail slot adjustment mechanism is used to adjust the center of the small hole to match the center of the photosensitive surface of the four-quadrant detector; the small hole is used to limit the incident light beam entering the tracking optical tube; the four-quadrant detector is used to receive the target light spot limited by the small hole and output the signal values ​​of the four quadrants; the amplification and acquisition circuit is used to amplify and acquire the signal values ​​of the four quadrants; after the parallel sunlight enters the measuring optical tube through the window, it passes through the aperture diaphragm, is reflected and focused by the off-axis parabolic mirror, and at the focal position, the stray light outside the field of view is filtered out by the field of view diaphragm, and then the stray light is further suppressed by the stray light elimination diaphragm. After being collimated by the meniscus lens and attenuated by the neutral density filter, it enters the spectrometer.

[0008] A method for coaxial adjustment of the optical axis of the converging optical path includes the following steps:

[0009] Step 1: Perform coarse tracking and preliminary fine tracking of the sun to obtain the current lock point;

[0010] Step 2: Collect signal values ​​from the four quadrants of the four-quadrant detector. ~ and the continuous spectral data output by the spectrometer;

[0011] Step 3: Calculate the measurement evaluation quantity based on the continuous spectral data. And calculate the total signal in the four quadrants based on the signal values ​​in the four quadrants:

[0012] ;

[0013] And construct normalized evaluation indicators:

[0014] ;

[0015] Among them, the measurement evaluation quantity It is the weighted integral sum of the continuous spectral intensities of multiple preset reference bands within the wavelength range of 2–6 μm;

[0016] Step 4: Perform a local five-point cross scan centered on the current locked point to obtain the normalized evaluation index corresponding to each scan point;

[0017] Step 5: Based on the normalized evaluation index corresponding to each scanning point, determine the optimal coaxial point through local quadratic fitting or direct comparison, read the target locking feature corresponding to the optimal coaxial point, and use the target locking feature as the target locking point for subsequent tracking.

[0018] Step 6: Monitor the normalized evaluation index in real time during normal measurement. When the instrument is powered on, or when the normalized evaluation index is lower than the reference value and meets the stability condition, trigger steps 4 to 5 again to achieve repeated coaxial adjustment of the measuring optical tube and the tracking optical tube.

[0019] The beneficial effects of this invention are as follows: By setting up a tracking optical tube consisting of a pinhole, a four-quadrant detector, and an adjustment mechanism, and a measurement optical tube consisting of an off-axis parabolic reflector, a field aperture, a stray beam deflector, a meniscus lens, a neutral density filter, and a spectrometer, stable tracking and effective convergence measurement of sunlight can be achieved; by constructing measurement evaluation quantities based on the continuous spectral intensities of multiple preset reference bands, and further forming normalized evaluation indices, the receiving state of the measurement optical path can be characterized more accurately; by performing a local five-point cross scan near the current locking point and determining the optimal coaxial point, the axial deviation between the measurement optical path and the tracking optical path can be reduced; by triggering coaxial adjustment again when the instrument is powered on or when the evaluation index decreases, online repeatable calibration can be achieved, improving the stability, repeatability, and automation of direct sunlight measurement. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the principle of a converging optical path and a method for coaxial adjustment of the optical axis of the solar spectroradiometer of the present invention.

[0021] Figure 2 This is a schematic diagram of the optical path structure of the measuring optical tube and the tracking optical tube of the present invention;

[0022] Figure 3 This is a schematic flowchart of the optical axis coaxial adjustment method of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0024] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments.

[0025] like Figures 1 to 2 As shown, this embodiment provides a converging optical path for a solar spectroradiometer. It includes a turntable base 1, a turntable 2, a probe 3, a tracking optical tube 4, a measuring optical tube 5, and a sun 6. The turntable 2 is mounted on the turntable base 1, the probe 3 is mounted on the turntable 2, and the tracking optical tube 4 and measuring optical tube 5 are both mounted on the probe 3 and rotate synchronously with the turntable 2. The turntable 2 is used to adjust the azimuth and elevation directions, so that the probe 3, tracking optical tube 4, and measuring optical tube 5 all point towards the sun 6.

[0026] The tracking light tube 4 is used to receive sunlight and output target deviation signals. It includes a pinhole 4-1, a dovetail adjustment mechanism 4-2, a four-quadrant detector 4-3, and an amplification and acquisition circuit 4-4. The pinhole 4-1 is used to limit the incident light beam entering the tracking light tube 4; the four-quadrant detector 4-3 is used to receive the target light spot limited by the pinhole 4-1 and output four quadrant signals; the amplification and acquisition circuit 4-4 is used to amplify and acquire the four quadrant signals; the dovetail adjustment mechanism 4-2 is used to adjust the center of the pinhole 4-1 to be aligned with the center of the photosensitive surface of the four-quadrant detector 4-3, so as to reduce the geometric deviation inside the tracking light tube 4.

[0027] The measuring optical tube 5 is used to receive sunlight and converge the incident sunlight to output a measurement signal. It includes a window 5-1, an aperture diaphragm 5-2, an off-axis parabolic mirror 5-3, a field diaphragm 5-4, a stray beam 5-5, a meniscus lens 5-6, a neutral density filter 5-7, and a spectrometer 5-8. Parallel sunlight enters the measuring optical tube 5 through the window 5-1, passes through the aperture diaphragm 5-2, is reflected and focused by the off-axis parabolic mirror 5-3, and at the focal point, stray light outside the field of view is filtered out by the field diaphragm 5-4. The stray light is further suppressed by the stray beam 5-5, collimated by the meniscus lens 5-6, and attenuated by the neutral density filter 5-7 before entering the spectrometer 5-8.

[0028] The optical axis coaxial adjustment method in this embodiment includes the following steps, such as... Figure 3 As shown.

[0029] Step 1: Perform coarse tracking and preliminary fine tracking of Sun 6 to obtain the current lock point. Specifically, first, use turntable 2 to roughly point probe 3 towards Sun 6, so that sunlight simultaneously enters tracking light tube 4 and measuring light tube 5; then, based on the signal output by quadrant detector 4-3, adjust turntable 2 so that the sunlight spot enters the effective working area of ​​quadrant detector 4-3, and establish the current lock point.

[0030] Step 2: Collect signal values ​​from the four quadrants (4-3) of the four-quadrant detector, and record them as follows: ~ Simultaneously, continuous spectral data output from spectrometers 5-8 are acquired. The total signal in the four quadrants is defined as:

[0031] ;

[0032] Spectrometer 5-8 at wavelength The continuous spectral intensity output at point is denoted as , which is the spectral intensity after dark current subtraction and normalization by integration time.

[0033] Step 3: Calculate the measurement evaluation quantity based on the continuous spectral data. Furthermore, a normalized evaluation index was constructed. In this embodiment, the measurement evaluation quantity The intensity is expressed as a weighted integral of continuous spectral intensity from multiple preset reference bands within the wavelength range of 2–6 μm.

[0034] ;

[0035] in, To preset the number of reference bands, For the first One reference band, These correspond to the weighting coefficients. Preferably, the reference band is selected from sub-bands with high signal-to-noise ratio in the 2–6 μm range and suitable for characterizing coaxial state changes. The normalized evaluation index is defined as:

[0036] ;

[0037] Compared to methods that rely solely on the geometric centers of the four quadrants for tracking, this embodiment utilizes normalized evaluation metrics. It simultaneously characterizes the combined state of the measurement optical path and the tracking optical path.

[0038] Step four: Perform a local five-point crosshair scan centered on the current locked point. Specifically, set positive and negative offsets in the azimuth and elevation directions respectively, record the azimuth and elevation variables of each point, and form the center point. and four neighboring points , , , Five scanning points are used, and the normalized evaluation index corresponding to each scanning point is obtained. Preferably, the scanning step size is 1′ to 3′. Local scanning adopts a center-return scanning path, that is, after completing the measurement of each neighboring point, it returns to the current locked point before measuring the next scanning point. During the scanning process, the total signal in the four quadrants is monitored in real time. When the total signal in the four quadrants is lower than a preset threshold, the current scanning is terminated and the current locked point is returned. The local scanning offset is less than the maximum allowable offset angle of the tracking optical tube 4 in the corresponding direction.

[0039] Step 5: Determine the optimal coaxial point based on the normalized evaluation index corresponding to each scan point. Preferably, the measurement evaluation quantity obtained from local scanning is used. To fit the object, a local quadratic function without cross terms is used for fitting:

[0040] ;

[0041] in, For orientation variables, For pitch direction variable, The optimal coaxial point is determined based on the local quadratic function's maximum value, serving as the fitting coefficient. If the fitting result does not meet the maximum value condition, the point with the largest evaluation value among all scan points is directly determined as the optimal coaxial point. The target locking features corresponding to the optimal coaxial point are read and used as the target locking point for subsequent tracking. The target locking features include lateral normalized features. and longitudinal normalized features They are respectively:

[0042] ;

[0043] ;

[0044] The horizontally normalized features and vertically normalized features corresponding to the optimal coaxial points are denoted as follows: and During normal measurement, with and As the target locking point for tracking optical tube 4, and based on the current and Separately and , The deviation is controlled in a closed loop. That is to say, in this embodiment, the subsequent tracking lock is not the geometric center of the four-quadrant detector, but the non-zero target lock point corresponding to the optimal reception state of the measurement optical path.

[0045] Step 6: Monitor the normalized evaluation index J in real time during normal measurement. Set the normalized evaluation index corresponding to the optimal coaxial point as the reference value. The normalized evaluation indicators collected in real time are then smoothed to obtain... When the following conditions are met: When this is triggered, repeated coaxial adjustment is performed, where, The preset scaling factor is preferably between 0.90 and 0.98. To avoid false triggering caused by sudden changes in illumination, the total signal in all four quadrants must also meet stability requirements within a preset time period.

[0046] ;

[0047] in, The standard deviation of the total signal in the four quadrants. The average value of the total signal in the four quadrants. To preset a stable threshold, a value of 0.02 to 0.05 is preferred. The smoothing time for the normalized evaluation index is preferably 3 to 10 seconds.

[0048] This embodiment uses a tracking optical tube 4 and a measuring optical tube 5 on the same probe 3 to construct a measurement evaluation quantity using the continuous spectral intensity of multiple reference bands. Furthermore, through local five-point cross scanning and optimal coaxial point determination methods, online repeatable coaxial adjustment between the measurement optical path and the tracking optical path is achieved. Compared with existing methods that rely solely on one-time static setup or solely on four-quadrant geometric center tracking, this embodiment can automatically repeat calibration during power-on and when the measurement state declines, thereby improving the stability, repeatability, and automation of direct solar radiation measurements.

[0049] The above description is only a preferred embodiment of the present invention. Any modifications, substitutions and improvements made by those skilled in the art without departing from the spirit and essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A converging optical path for a solar spectroradiometer, characterized in that, The system includes a turntable base (1), a turntable (2), a probe (3), a tracking optical tube (4), and a measuring optical tube (5). The turntable (2) is mounted on the turntable base (1), the probe (3) is mounted on the turntable (2), and the tracking optical tube (4) and the measuring optical tube (5) are both mounted on the probe (3) and rotate synchronously with the turntable (2). The tracking optical tube (4) is used to receive sunlight (6) and output a target deviation signal, and the measuring optical tube (5) is used to receive sunlight (6). The light will converge the incident sunlight and output a measurement signal; the tracking light tube (4) includes a small aperture (4-1), a dovetail groove adjustment mechanism (4-2), a four-quadrant detector (4-3), and an amplification and acquisition circuit (4-4); the measuring light tube (5) includes a window (5-1), an aperture diaphragm (5-2), an off-axis parabolic mirror (5-3), a field diaphragm (5-4), a stray beam diaphragm (5-5), a meniscus lens (5-6), a neutral density filter (5-7), and a spectrometer (5-8); The dovetail groove adjustment mechanism (4-2) is used to adjust the center of the small hole (4-1) to be consistent with the center of the photosensitive surface of the four-quadrant detector (4-3); The aperture (4-1) is used to limit the incident light beam entering the tracking light tube (4), the four-quadrant detector (4-3) is used to receive the target light spot limited by the aperture (4-1) and output the signal values ​​of the four quadrants, and the amplification and acquisition circuit (4-4) is used to amplify and acquire the signal values ​​of the four quadrants. Parallel sunlight enters the measuring optical tube (5) through the window (5-1), passes through the aperture diaphragm (5-2), is reflected and focused by the off-axis parabolic mirror (5-3), and at the focal point, stray light outside the field of view is filtered out by the field of view diaphragm (5-4). The stray light is further suppressed by the stray light suppression diaphragm (5-5), collimated by the meniscus lens (5-6), and attenuated by the neutral density filter (5-7) before entering the spectrometer (5-8).

2. The converging optical path for a solar spectroradiometer according to claim 1, characterized in that, The turntable (2) includes azimuth adjustment function and pitch adjustment function, which are used to drive the probe (3), the tracking optical tube (4) and the measuring optical tube (5) to rotate synchronously.

3. A method for coaxial adjustment of the optical axis of a converging optical path in a solar spectroradiometer according to any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: Perform coarse tracking and preliminary fine tracking of the sun (6) to obtain the current lock point; Step 2: Collect signal values ​​from the four quadrants of the four-quadrant detector (4-3). ~ and the continuous spectral data output by the spectrometer (5-8); Step 3: Calculate the measurement evaluation quantity based on the continuous spectral data. And calculate the total signal in the four quadrants based on the signal values ​​in the four quadrants: ； And construct normalized evaluation indicators: ； Among them, the measurement evaluation quantity It is the weighted integral sum of the continuous spectral intensities of multiple preset reference bands within the wavelength range of 2–6 μm; Step 4: Perform a local five-point cross scan centered on the current locked point to obtain the normalized evaluation index corresponding to each scan point; Step 5: Based on the normalized evaluation index corresponding to each scanning point, determine the optimal coaxial point through local quadratic fitting or direct comparison, read the target locking feature corresponding to the optimal coaxial point, and use the target locking feature as the target locking point for subsequent tracking. Step 6: Monitor the normalized evaluation index in real time during normal measurement. When the instrument is turned on, or when the normalized evaluation index is lower than the reference value and meets the stability condition, trigger steps 4 to 5 again to achieve repeated coaxial adjustment of the measuring optical tube (5) and the tracking optical tube (4).

4. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, The continuous spectral intensity The measured evaluation quantity represents the spectral intensity output by the spectrometer at wavelength λ, after dark current subtraction and normalization by integration time; Represented as: ； in, To preset the number of reference bands, For the first One reference band, These are the corresponding weighting coefficients.

5. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, Step 4, the five-point cross scan, includes: using the current locked point as the center point, offsetting along the azimuth direction (positive), azimuth direction (negative), pitch direction (positive), and pitch direction (negative) to form five scan points, including the center point and its four neighboring points, and obtaining the normalized evaluation index corresponding to each scan point.

6. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, In step 5, the measurement evaluation quantity obtained from the local scan is used. To fit the object, the following local quadratic function without cross terms is used for fitting: ； in, For orientation variables, For pitch direction variable, The fitting coefficients are used to determine the optimal coaxial point based on the local quadratic function's maximum value.

7. The method for coaxial adjustment of optical axis according to claim 6, characterized in that, In step 5, the target locking features include lateral normalized features. and longitudinal normalized features They are respectively: ； ； The horizontal normalized feature and vertical normalized feature corresponding to the optimal coaxial point are denoted as follows: and .

8. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, The local scan in step 4 adopts a center-return scan path. Each scan point is offset from the current locked point, and after the measurement of each scan point is completed, it returns to the current locked point before the measurement of the next scan point is performed. During the local scanning process, the total signal in the four quadrants is monitored in real time. When the total signal in the four quadrants is lower than the preset threshold, the current scan is terminated and the current locking point is returned. The offset of the local scan is less than the maximum allowable offset angle of the tracking light tube (4) in the corresponding direction.

9. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, In step 6, the reference value is the normalized evaluation index corresponding to the optimal coaxial point. The normalized evaluation indicators collected in real time are then smoothed to obtain... Repeated coaxial adjustment is triggered when the following condition is met: ； in, This is a preset scaling factor, and The stability condition is that the fluctuation of the total signal in the four quadrants within a preset time period satisfies: ； in, The standard deviation of the total signal in the four quadrants is given. The average value of the total signal in the four quadrants. A preset stable threshold is used; during normal measurement, the lateral normalized feature corresponding to the optimal coaxial point is used. and longitudinal normalized features As the target locking point for tracking the optical tube (4), and based on the current lateral normalized features With longitudinal normalized features respectively with , The deviation is controlled in a closed loop.

10. The method for coaxial adjustment of optical axis according to claim 3, characterized in that, The reference band is selected from sub-bands with high signal-to-noise ratio in the range of 2 to 6 μm and suitable for characterizing changes in coaxial state.

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