A light path collection system coupled to a sun tracker

Abstract

This invention discloses an optical path acquisition system for a coupled solar tracker, belonging to the field of environmental monitoring technology. The system includes: a solar tracker employing coarse tracking using astronomical formulas and fine tracking via closed-loop feedback from a four-quadrant detector, driving a first and second reflecting mirror to reflect sunlight onto an off-axis parabolic mirror; a beam compression structure, composed of an off-axis parabolic mirror and a collimating parabolic mirror, compressing a 50mm aperture incident light spot into a 24mm aperture parallel beam for output to an interferometer; an interferometer system, including a beam splitter, a solid angle mirror, and a reflecting mirror, for interferometry modulation of the compressed beam; and an output system, including a focusing parabolic mirror with a focal length of 52.5mm, converging the interferometric light into a 1×1mm focal length. 2 The invention utilizes a combination of beam compression and a focusing parabolic mirror to achieve high light throughput and high signal-to-noise ratio solar spectral measurements, making it suitable for ground-based remote sensing observations of weakly absorbing gases.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, specifically relating to an optical path acquisition system coupled with a solar tracker. Background Technology

[0002] In recent years, ground-based remote sensing spectroscopy based on solar light sources has been widely used for monitoring the concentrations of atmospheric greenhouse gases and pollutants. Compared to active light sources, solar radiation has enormous energy and a stable spectrum, making it an ideal source for spectral detection. By collecting solar spectra using surface spectrometers, the concentrations of various trace gases in the atmosphere can be retrieved, providing crucial data support for studying regional emissions, pollution mechanisms, and gas interactions.

[0003] In a spectral acquisition system coupled with a solar tracker, the core challenge in system design is how to efficiently and stably guide sunlight into the spectrometer while achieving high signal-to-noise ratio detection. When the solar altitude angle is high or the sun is moving across the sky, if the reflector cannot track the sun's position in real time, sunlight will be difficult to accurately enter the spectrometer, especially during midday when signal loss is likely to occur. Furthermore, the sun's position in the sky is constantly changing; if the light flux entering the spectrometer is unstable, it will cause fluctuations in the spectral signal-to-noise ratio, resulting in measurement distortion.

[0004] In existing technologies, there are schemes that use a four-quadrant detector combined with a motor drive to achieve closed-loop solar tracking (such as Chinese patent application publication number CN102156098B). This scheme drives the motor adjustment by detecting the position deviation of the light spot on the four-quadrant detector, and can achieve solar tracking with a certain degree of accuracy. Another scheme uses two parallel reflectors and a photodetector to calculate the position of the light spot (such as Chinese patent application publication number CN110989695B), which is suitable for solar tracking on mobile platforms. However, the above-mentioned existing technologies mainly focus on improving the tracking control algorithm, and lack systematic optical path optimization design for issues such as how to efficiently couple the tracked light signal into the spectrometer and how to match the small photosensitive surface of the high-sensitivity detector.

[0005] Specifically, existing solar trackers typically emit large light spots, while the effective photosensitive surface of high-sensitivity detectors (such as MCT detectors) is often only 1mm × 1mm or even smaller. If a large light spot is directly coupled into the spectrometer, most of the light energy cannot enter the detector, resulting in a severe loss of light flux and making it difficult to achieve high signal-to-noise ratio measurements of weakly absorbing gases. At the same time, the traditional optical path transmission between the tracker and the spectrometer lacks targeted compression and convergence design, further exacerbating light energy loss.

[0006] Therefore, how to design a low-loss, high-throughput optical path acquisition system that can efficiently couple sunlight into a spectrometer and converge it to a small photosensitive surface detector, thereby achieving high signal-to-noise ratio solar spectral measurement, while ensuring high-precision solar tracking, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides an optical path acquisition system for coupling a solar tracker. The system uses a beam compression structure to compress the large light spot of the solar tracker and couple it into a spectrometer. A focusing parabolic mirror is then used to focus the light onto a small photosensitive detector, thereby achieving high light throughput and high signal-to-noise ratio solar spectrum acquisition.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An optical path acquisition system coupled to a solar tracker includes:

[0010] The input optical system includes a solar tracker and a beam compression structure. The solar tracker uses a dual-mode control strategy that combines coarse tracking with astronomical formulas with fine tracking with closed-loop feedback from photoelectric detectors to track the sun in real time and reflect sunlight into the beam compression structure.

[0011] The beam compression structure consists of an off-axis parabolic mirror and a collimating parabolic mirror. The off-axis parabolic mirror receives an incident light spot of a first diameter from the solar tracker and reflects it to the collimating parabolic mirror. The collimating parabolic mirror recollides the diverging beam into a parallel beam of a second diameter, wherein the first diameter is larger than the second diameter. The off-axis angle of both the off-axis parabolic mirror and the collimating parabolic mirror is 90 degrees. Beam compression is achieved by adjusting the focal length ratio of the off-axis parabolic mirror and the collimating parabolic mirror.

[0012] The interferometer system receives the compressed beam output from the collimating parabolic mirror and performs interference modulation to generate interference light;

[0013] The output system includes a focusing parabolic mirror disposed at the front end of the detector, used to converge the interference light output by the interferometer system to the photodetector.

[0014] Furthermore, the coarse tracking of the astronomical formula specifically involves: obtaining the time, latitude and longitude information of the observation site based on the Global Positioning System, calculating the solar altitude angle and azimuth angle, and driving the motor to achieve coarse tracking.

[0015] Furthermore, the solar tracker includes a first reflector, a second reflector, a first motor, a second motor, a photoelectric reflector, and a photodetector; both the first and second reflectors are mounted on a fixed base, and are arranged parallel to each other; the first motor is connected to the first reflector and is used to control the first reflector to rotate around a horizontal axis to track the solar altitude angle and reflect sunlight to the second reflector; the second motor is connected to the fixed base and is used to control the fixed base as a whole to rotate around a vertical axis to track the solar azimuth angle.

[0016] Furthermore, the formula for calculating the solar altitude angle is based on the declination angle, the latitude of the observation location, and the hour angle parameter, and the formula for calculating the azimuth angle is based on the declination angle, the latitude of the observation location, the longitude of the observation location, and the hour angle parameter, wherein the declination angle is calculated based on the date, and the hour angle is calculated based on the time.

[0017] Furthermore, the closed-loop feedback fine tracking of the photodetector specifically involves: detecting the positional deviation of the solar spot on the photodetector, wherein the photodetector has four electrodes corresponding to four quadrant regions; when the solar spot illuminates the photosensitive surface of the photodetector, determining the coordinates of the center position of the solar spot based on the proportional relationship between the current values ​​output by the four electrodes; and driving the motor to perform fine adjustments based on the calculated deviation between the coordinates of the solar spot center position and the center position of the photodetector.

[0018] Furthermore, the abscissa of the solar spot center position coordinates is obtained by dividing the difference between the sum of the currents in the two diagonal quadrants and the sum of the currents in the other two diagonal quadrants by the sum of the currents in the four electrodes, and the ordinate is obtained by dividing the difference between the sum of the currents in two adjacent quadrants and the sum of the currents in the other two adjacent quadrants by the sum of the currents in the four electrodes.

[0019] Furthermore, both the first and second reflectors are elliptical plane reflectors with a major axis of 71 mm and a minor axis of 50 mm.

[0020] Furthermore, both the first motor and the second motor are stepper motors and operate independently.

[0021] Furthermore, the interferometer system includes a beam splitter, a third reflecting mirror, a fourth reflecting mirror, a first solid angle mirror, and a second solid angle mirror. The beam splitter receives the compressed beam output from the collimating parabolic mirror and splits the compressed beam into two paths. One path is transmitted to the third reflecting mirror and then reflected to the first solid angle mirror, while the other path is transmitted to the fourth reflecting mirror and then reflected to the second solid angle mirror. The first and second solid angle mirrors reflect the received beams back to the beam splitter, and the two beams interfere at the beam splitter before being output to the output system. The angles between the third and fourth reflecting mirrors and the beam splitter are both 45 degrees, and the first and second solid angle mirrors remain parallel during movement.

[0022] Furthermore, the off-axis parabolic mirror has an aperture of 50 mm and a focal length of 101.6 mm, the collimating parabolic mirror has an aperture of 24 mm and a focal length of 50.8 mm, the focusing parabolic mirror has a focal length of 52.5 mm, and the photodetector is a liquid nitrogen-cooled MCT detector.

[0023] In a second aspect, the present invention provides an electronic device comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned optical path acquisition system method for a coupled solar tracker.

[0024] Thirdly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned optical path acquisition system method for a coupled solar tracker.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention adds a beam compression structure between the solar tracker and the spectrometer. Through the cooperation of an off-axis parabolic mirror and a collimating parabolic mirror, a large-diameter incident light spot is compressed into a small-diameter spot, achieving efficient and low-loss coupling of the optical signal. Simultaneously, a focusing parabolic mirror is placed at the front end of the detector to further converge the compressed beam onto the small photosensitive surface detector. This optical path design effectively solves the light energy loss problem caused by the mismatch between the light spot size and the detector's photosensitive surface size in traditional solutions, significantly improving the signal-to-noise ratio of the spectral signal.

[0027] This invention employs a dual-mode control strategy combining coarse tracking using astronomical formulas with fine tracking via closed-loop feedback from a four-quadrant detector. First, the solar altitude and azimuth angles are calculated based on time and latitude / longitude information to drive the motor for coarse tracking. Then, the four-quadrant detector is used to detect the spot position deviation in real time, driving the motor for fine-tuning. This scheme avoids the feedback delay caused by simple image processing, ensuring that the light flux entering the spectrometer remains constant during the sun's movement, resulting in stable and reliable acquired spectral signals.

[0028] This invention integrates solar tracking, beam compression, interferometric modulation, and focused detection into a single unit, forming a complete ground-based remote sensing spectral acquisition chain, which is particularly suitable for high-precision solar spectral observation of weakly absorbing gases. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the optical path acquisition system of a coupled solar tracker according to the present invention;

[0030] Figure 2 This is a simulation diagram of the optical path acquisition system of a coupled solar tracker according to the present invention;

[0031] Figure 3 This is a schematic diagram of the solar tracker structure of the present invention;

[0032] Figure 4 This is a flowchart of an optical path acquisition method for a coupled solar tracker according to the present invention;

[0033] Figure 5 The results of spectral acquisition using the system of this invention.

[0034] Figure label:

[0035] First reflecting mirror 1, second reflecting mirror 2, off-axis parabolic mirror 3, collimating parabolic mirror 4, first solid angle mirror 5, second solid angle mirror 6, third reflecting mirror 7, fourth reflecting mirror 8, 50 / 50 beam splitter 9, focusing parabolic mirror 10, MCT detector 11, first motor 12, second motor 13, photoelectric reflecting mirror 14, photoelectric detector 15. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] This embodiment provides an optical path acquisition system for a coupled solar tracker, used to measure the infrared solar absorption spectrum in the atmosphere. The system is based on optical path simulation design of the dimensions and optical parameters of a plane mirror, a spherical mirror, and a focusing parabolic mirror. Closed-loop feedback photoelectric tracking is used to accurately track sunlight, and the spherical mirror and focusing parabolic mirror are used to accurately acquire the mid-infrared solar spectrum. The entire optical path acquisition system is as follows: Figure 1 As shown.

[0038] Continue to refer to Figure 1 The optical path acquisition system includes an input optical system, an interferometer system, and an output system. The input optical system includes a solar tracker and a beam compression structure. First, sunlight is incident on a first reflecting mirror 1, and after reflection, it illuminates a second reflecting mirror 2. The second reflecting mirror 2 vertically reflects the sunlight to an off-axis parabolic mirror 3. The off-axis parabolic mirror 3 compresses the beam and reflects it horizontally to a collimating parabolic mirror 4. The beam is then collimated and enters the interferometer system. In the interferometer system, the beam passes through a 50 / 50 beam splitter 9 and reaches a third reflecting mirror 7 and a fourth reflecting mirror 8, respectively. It is then reflected to a first solid angle mirror 5 and a second solid angle mirror 6, respectively. After further reflection by the first solid angle mirror 5 and the second solid angle mirror 6, interference occurs at the 50 / 50 beam splitter 9. Subsequently, the interfering beam enters the output system, is focused by a focusing parabolic mirror 10, and is transmitted to the image plane of the MCT detector 11. The angle between the third reflecting mirror 7 and the fourth reflecting mirror 8 and the 50 / 50 beam splitter 9 is 45°, and the first solid angle mirror 5 and the second solid angle mirror 6 remain parallel during movement.

[0039] In summary, to ensure the rational configuration of the designed system and optical components, it is necessary to simulate the entire optical path. Simulation can determine the optimal installation positions of each component and verify whether the beam can accurately reach the image plane of the detector, thus meeting the design requirements. Specific parameter requirements for the optical system are shown in Table 1. The parameters of the overall optical path system and optical components are input into the simulation software. The entrance pupil diameter is set to 50mm in the system aperture, and the field of view angle is set to 0.1°. (The text continues with further details about the simulation software and its parameters.) Figure 2 As shown in the simulation results, the light can pass smoothly through the input optical system, enter the interferometer system, and finally reach the MCT detector 11 through the focusing parabolic mirror 10, as required by the design.

[0040] Table 1

[0041]

[0042] In this embodiment, the spectrometer coupled to the solar tracker is a Fourier transform infrared spectrometer (FTIR) with a spectral resolution of 0.5 cm⁻¹. -1 Measurement band 700-5000cm -1 It covers multiple detection bands for greenhouse gases and pollutants. The spectrometer uses a KBr beamsplitter, and the detector is a liquid nitrogen-cooled MCT detector 11, with a spectral response range of 600-6000 cm⁻¹. -1 The effective detection area is 1×1 mm. 2 .

[0043] The optical path of the solar tracker is as follows Figure 3As shown, the entire structure mainly consists of a motor, a reflector, a fixed base, a rotating stage, and a photodetector. Specifically, the first reflector 1, the second reflector 2, and the first motor 12 are all mounted on the fixed base, with the first reflector 1 and the second reflector 2 parallel to each other. The second motor 13 and the rotating stage are fixed below the fixed base, with the second motor 13 connected to the rotating stage and controlling its rotation. The first motor 12 controls the first reflector 1 to rotate 360° around the horizontal axis, tracking the sun's altitude angle in real time, and simultaneously reflecting sunlight to the second reflector 2. The second motor 13 controls the entire fixed base to rotate 360° around the vertical axis, calculating the sun's azimuth angle. The sunlight reflected by the second reflector 2 is divided into two parts: most of the sunlight is vertically reflected by the second reflector 2 to the off-axis parabolic mirror 3, ultimately reaching the interferometer system; while a small portion reaches the photodetector 15 through the photodetector 14. Both the first motor 12 and the second motor 13 are stepper motors, operating independently without affecting each other. Based on the field of view of the solar tracking system, it can be calculated that both the first reflector 1 and the second reflector 2 are elliptical plane reflectors with a major axis of 71 mm and a minor axis of 50 mm.

[0044] The overall optical path tracing process is as follows: Figure 4 As shown, when the solar tracker is working, it obtains the time, latitude, and longitude information of the observation site based on GPS, and calculates the solar altitude angle and azimuth angle based on this information, where the solar altitude angle is... and azimuth The calculation formula is as follows:

[0045] ,

[0046] ,

[0047] In the formula Represents the declination angle, and the calculation method is as follows. , Indicates the date of the calculation; Indicates the latitude of the observation location. Indicates the longitude of the observation location; Representing the hour angle, calculation method , Indicates time.

[0048] After calculating the solar altitude angle α and azimuth angle γ, the processor calculates the motor rotation pulses based on these angles and drives the first motor 12 and the second motor 13 to rotate, respectively rotating the first reflector 1 and the second reflector 2. When sunlight is reflected into the photodetector 15, the photodetector 15 determines whether the light path is collimated and simultaneously provides feedback on the position of the solar spot. If the light path is offset, the offset is calculated, and the motor is driven to fine-tune the solar tracker. The photodetector 15 is a four-quadrant position detector, and the position of the solar spot received on its photosensitive surface is calculated by the following formula.

[0049] ,

[0050] ,

[0051] In the formula and Indicates the coordinates of the center position of the four-quadrant detector. This indicates the side length of the effective photosensitive surface of the four-quadrant detector. and They are The current values ​​of the two electrodes in the direction, and They are The current values ​​of the two electrodes are used to determine the direction. The four-quadrant detector calculates the position of the light spot based on the current generated by the detector, and then drives the motor to adjust it, achieving precise tracking of the sun. The center of the four-quadrant position detector is coaxial with the center of the photoelectric reflector 14, and its dimensions are 10 mm × 10 mm. Calculations show that the tracking accuracy of the sun tracker can reach 0.1°, meeting the requirements for stable tracking of the sun.

[0052] To improve optical signal transmission efficiency, a beam compression structure is added between the solar tracker and the FTIR device, namely... Figure 1 The off-axis parabolic mirror 3 and focusing mirror 4 in the interferometer effectively compress the large light spot tracked by the solar tracker into a smaller diameter spot, thus facilitating the focused beam into the spectrometer. This design not only optimizes light transmission efficiency but also helps improve the overall measurement accuracy and performance of the interferometer.

[0053] The beam compression structure mainly consists of an off-axis parabolic mirror 3 and a collimating parabolic mirror 4. The core function of this structure is to change the propagation direction of the beam without inducing optical aberrations. At the same time, thanks to the unique properties of the parabolic mirror, aberration-free reflection can be achieved even if the beam is not incident along the traditional axis of symmetry.

[0054] In the beam compression system, the off-axis parabolic mirror 3, with an aperture of 50 mm, receives the light captured by the solar tracker. Simultaneously, through a spectrometer window, a collimating parabolic mirror 4, with an aperture of 24 mm, serves as a second mirror within the spectrometer for collimation. The off-axis angle between the two mirrors is 90°. Based on the aperture ratio of the off-axis parabolic mirror 3 and the collimating parabolic mirror 4, the focal length of the off-axis parabolic mirror 3 is 101.6 mm, and the focal length of the collimating parabolic mirror 4 is 50.8 mm.

[0055] The beam, collimated by the collimating parabolic mirror 4, enters the interferometer system. Within the interferometer, the beam is reflected by the first solid angle mirror 5 and the second solid angle mirror 6, and after passing through their respective reflection paths, is output from the other end of the beam splitter. The interferometer system employs the standard interference optical path structure of a Fourier transform infrared spectrometer, generating an optical path difference through the movement of a moving mirror, thus forming an interference signal.

[0056] The beam passing through the interferometer system interferes at the 50 / 50 beam splitter 9 and then enters the focusing detection system. While meeting the spot radius requirements of the MCT detector 11, the smaller the focal length of the focusing parabolic mirror 10 placed at the front of the MCT detector 11, the larger the maximum tilt angle of the incident light, and thus the larger the achievable optical signal. However, due to the presence of the FTIR moving mirror, its movement affects the changes in light transmission. Conversely, the larger the focal length of the focusing parabolic mirror 10, the smaller the influence of the moving mirror on the changes in light, thereby improving the overall stability of the system. After comprehensive consideration, this invention sets the focal length of the focusing parabolic mirror 10 to 52.5 mm. By accurately guiding the measurement light into the MCT detector 11 through the focusing parabolic mirror 10, high light flux and high signal-to-noise ratio solar spectrum measurement are achieved.

[0057] This invention utilizes a constructed coupled optical path system to conduct solar spectrum measurements. Under clear conditions, a solar tracker accurately tracks the sun in real time and directs sunlight into a spectrometer, successfully acquiring high-luminous-flux solar spectra. The measured spectra are as follows: Figure 5 As shown, its spectral band is 700-5000 cm⁻¹. -1 The spectral resolution is 0.1 cm⁻¹. -1 .

[0058] The above design, through a ground-based remote sensing spectral acquisition system coupled with a solar tracker, acquired optimal light signal characteristics. Based on the precise tracking of the sun's movement across the sky by the solar precision system, sunlight is reflected into the spectral acquisition equipment in real time, ensuring accurate and stable solar spectra acquisition even as the sun moves across the sky. The accurate coupling of sunlight into the spectrometer using a combination of plane and spherical mirrors increases luminous flux and enhances the spectral signal. A focusing parabolic mirror placed at the front of the detector accurately guides the measurement light into the detector, achieving high luminous flux and high signal-to-noise ratio solar spectral measurements. Actual spectral measurements validated the reliability of the system, demonstrating the feasibility of using this system for observing the solar spectra of weakly absorbing gases.

[0059] In a second aspect, the present invention provides an electronic device comprising: one or more processors; and a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned optical path acquisition system method for a coupled solar tracker.

[0060] Thirdly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned optical path acquisition system method for a coupled solar tracker.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A light path acquisition system for coupling a sun tracker, characterized in that, include: The input optical system includes a solar tracker and a beam compression structure. The solar tracker uses a dual-mode control strategy that combines coarse tracking with astronomical formulas with fine tracking with closed-loop feedback from photoelectric detectors to track the sun in real time and reflect sunlight into the beam compression structure. The beam compression structure consists of an off-axis parabolic mirror and a collimating parabolic mirror. The off-axis parabolic mirror receives an incident light spot of a first diameter from the solar tracker and reflects it to the collimating parabolic mirror. The collimating parabolic mirror recollides the diverging beam into a parallel beam of a second diameter, wherein the first diameter is larger than the second diameter. The off-axis angle of both the off-axis parabolic mirror and the collimating parabolic mirror is 90 degrees. Beam compression is achieved by adjusting the focal length ratio of the off-axis parabolic mirror and the collimating parabolic mirror. The interferometer system receives the compressed beam output from the collimating parabolic mirror and performs interference modulation to generate interference light; The output system includes a focusing parabolic mirror disposed at the front end of the detector, used to converge the interference light output by the interferometer system to the photodetector.

2. The optical path acquisition system for a coupled solar tracker according to claim 1, characterized in that, The coarse tracking of the astronomical formula specifically involves: obtaining the time, latitude and longitude information of the observation site based on the Global Positioning System, calculating the solar altitude angle and azimuth angle, and driving the motor to achieve coarse tracking.

3. The light path collecting system of a coupled sun tracker according to claim 1, wherein, The solar tracker includes a first reflector, a second reflector, a first motor, a second motor, a photoelectric reflector, and a photodetector. Both the first and second reflectors are mounted on a fixed base, and are arranged parallel to each other. The first motor is connected to the first reflector and controls its rotation around a horizontal axis to track the solar altitude angle, reflecting sunlight to the second reflector. The second motor is connected to the fixed base and controls its overall rotation around a vertical axis to track the solar azimuth angle.

4. The optical path acquisition system for a coupled solar tracker according to claim 2, characterized in that, The formula for calculating the solar altitude angle is based on the declination angle, the latitude of the observation location, and the hour angle parameter. The formula for calculating the azimuth angle is based on the declination angle, the latitude of the observation location, the longitude of the observation location, and the hour angle parameter. The declination angle is calculated based on the date, and the hour angle is calculated based on the time.

5. The light path collecting system of a sun tracking instrument according to claim 3, wherein, The closed-loop feedback fine tracking of the photodetector specifically involves: detecting the positional deviation of the solar spot on the photodetector, which has four electrodes corresponding to four quadrant regions; when the solar spot illuminates the photosensitive surface of the photodetector, determining the coordinates of the center position of the solar spot based on the proportional relationship between the current values ​​output by the four electrodes; and driving a motor to perform fine adjustments based on the calculated deviation between the coordinates of the solar spot center and the center position of the photodetector.

6. The light path acquisition system of claim 5, wherein, The x-coordinate of the coordinates of the center position of the solar spot is obtained by dividing the difference between the sum of the currents in the two diagonal quadrants and the sum of the currents in the other two diagonal quadrants by the sum of the currents of the four electrodes. The y-coordinate is obtained by dividing the difference between the sum of the currents in two adjacent quadrants and the sum of the currents in the other two adjacent quadrants by the sum of the currents of the four electrodes.

7. The light path collecting system of a sun tracking instrument according to claim 3, wherein, Both the first and second reflectors are elliptical plane reflectors with a major axis of 71 mm and a minor axis of 50 mm.

8. The light path collecting system of a sun tracking instrument according to claim 3, wherein, Both the first motor and the second motor are stepper motors and operate independently.

9. The light path collecting system of a sun tracking instrument according to claim 1, wherein, The interferometer system includes a 50 / 50 beam splitter, a third reflecting mirror, a fourth reflecting mirror, a first solid angle mirror, and a second solid angle mirror. The 50 / 50 beam splitter receives the compressed beam output from the collimating parabolic mirror and splits it into two paths. One path is transmitted to the third reflecting mirror and then reflected to the first solid angle mirror, while the other path is transmitted to the fourth reflecting mirror and then reflected to the second solid angle mirror. The first and second solid angle mirrors reflect the received beams back to the beam splitter, and the two beams interfere at the beam splitter before being output to the output system. The angles between the third and fourth reflecting mirrors and the beam splitter are both 45 degrees, and the first and second solid angle mirrors remain parallel during movement.

10. The light path collecting system of a sun tracking instrument according to claim 1, wherein, The off-axis parabolic mirror has an aperture of 50 mm and a focal length of 101.6 mm, the collimating parabolic mirror has an aperture of 24 mm and a focal length of 50.8 mm, the focusing parabolic mirror has a focal length of 52.5 mm, and the photodetector is a liquid nitrogen-cooled MCT detector.

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