A wide-band, high-efficiency solar spectrometer

Abstract

The present invention relates to a wide-band, high-efficiency solar spectrometer, which belongs to the field of spectrum measurement technology, and solves the problems of low spectral resolution of prism-type solar spectrometers when covering a wide band, spectral overlap of grating-type solar spectrometers during measurement, long single measurement time, and low work efficiency. The solar spectrometer of the present invention includes a homogenizing element, an incident slit, a visible channel, and an infrared channel. The visible channel includes two holographic concave gratings, two folding mirrors, and a visible detector. The infrared channel includes two holographic concave gratings, two folding mirrors, and an infrared detector. The four holographic concave gratings are mounted on the same set of grating axes, and the bottom surfaces of the holographic concave gratings of the two channels are projected at an angle on a plane perpendicular to the grating axis. The present invention fundamentally solves the problem of invalid scanning of a wavelength scanning mechanism occupying measurement time caused by mismatched start-up wavelengths of each channel, greatly reduces the time of a single measurement, and improves the work efficiency of the solar spectrometer.

Description

Technical Field

[0001] The invention relates to the technical field of spectrum measurement, in particular to a wide-band and high-efficiency solar spectrometer. Background Art

[0002] The sun, as the source of life on Earth, provides energy that is the cornerstone of the Earth's ecosystem. Most of the sun's energy output is transmitted outward in the form of electromagnetic radiation, which has a very wide wavelength range, covering all frequency bands from gamma rays to radio waves. Among them, 97% of the energy is concentrated in the ultraviolet, visible and infrared bands, and the energy in these bands has a particularly significant impact on the Earth's environment.

[0003] Since the 1970s, remote sensing monitoring of solar spectrum radiation changes has been carried out both at home and abroad. Since the solar spectrum covers a wide range, the monitoring of the solar spectrum usually covers the ultraviolet, visible to infrared bands. Common solar spectrometers use gratings or prisms for spectroscopy. The most representative grating spectrometer is the solar spectrometer SOLAR carried on Columbia, which uses a holographic concave grating to measure the irradiance of the solar spectrum, with a wavelength coverage of 165nm-3080nm. The most representative prism spectrometer is the spectral irradiance detector SIM (Spectral Irradiance Monitor) carried on the Solar Irradiance and Climate Experiment SORCE satellite, which uses Fery prisms, sub-collimation and imaging, and uses only one optical element to achieve full wavelength range detection, with a band coverage of 200nm-2700nm, and a spectral resolution ranging from 1nm to 40nm.

[0004] For prism-type solar spectrometers, high spectral resolution cannot be achieved when covering a wide band. For grating-type solar spectrometers, although the spectral resolution is higher than that of prism-type, in solar spectrometers that use gratings for spectrometry, the holographic concave grating is usually driven by a grating axis. For ease of adjustment, several gratings are usually adjusted at the same angle, and the entire spectral range is scanned by rotating the grating. Since the gratings are adjusted at the same angle, the starting wavelength of each channel is not the starting wavelength of the channel during scanning, which results in a large scanning angle, making the time for a single full-spectrum measurement very long, limiting the working efficiency of the solar spectrometer. For gratings, different wavelengths correspond to different angles, but in existing technical solutions, when the grating axis rotates, each grating rotates at the same angle. For different channels, such as visible and infrared, there will be overlapping spectral portions when the grating axis rotates for scanning, such as Figure 1 As shown, this part of the repeated scanning is equivalent to wasting a long scanning time, making the single measurement time very long and reducing the working efficiency of the solar spectrometer. Summary of the invention

[0005] In view of the problem that a prism-type solar spectrometer cannot achieve high spectral resolution when covering a wide band, and a grating-type solar spectrometer has spectral overlap during measurement, resulting in a long single measurement time and low working efficiency, the present invention proposes a wide-band, high-efficiency solar spectrometer.

[0006] To solve the above problems, the present invention adopts the following technical solutions:

[0007] A wide-band, high-efficiency solar spectrometer, comprising a first light homogenizing element, a second light homogenizing element, a first incident slit, a second incident slit, a visible channel and an infrared channel; after passing through the first light homogenizing element and the first incident slit, sunlight enters the visible channel, and the visible channel comprises a first holographic concave grating, a first folding mirror, a second folding mirror, a second holographic concave grating and a visible detector arranged in sequence along the optical path; after passing through the second light homogenizing element and the second incident slit, sunlight enters the infrared channel, and the infrared channel comprises a third holographic concave grating arranged in sequence along the optical path. A holographic concave grating, a third folding mirror, a fourth folding mirror, a fourth holographic concave grating and an infrared detector, wherein the first holographic concave grating, the second holographic concave grating, the third holographic concave grating and the fourth holographic concave grating are mounted on the same set of grating axes, and the bottom surfaces of the first holographic concave grating and the second holographic concave grating are parallel to each other, the bottom surfaces of the third holographic concave grating and the fourth holographic concave grating are parallel to each other, and the projections of the bottom surfaces of the second holographic concave grating and the third holographic concave grating on a plane perpendicular to the grating axes form an angle , angle The value of is determined by the following steps:

[0008] Step 1: Determine the wavelength range of each of the visible channel and the infrared channel according to the target spectral range, including a starting wavelength and an ending wavelength;

[0009] Step 2: Calculate the grating angle ranges corresponding to the visible channel and the infrared channel respectively according to the grating diffraction formula and the wavelength range, including the starting angle and the ending angle;

[0010] Step 3: Calculate the difference between the starting angle of the visible channel and the starting angle of the infrared channel, and use the difference as the angle The value of .

[0011] The beneficial effects of the present invention are as follows: the present invention utilizes a grating axis to drive four holographic concave gratings to rotate to realize a miniaturized design within a wide spectral range, and through the non-parallel adjustment of the gratings, the starting wavelength of each channel is made to be the starting wavelength of the wavelength range of the channel, fundamentally solving the problem of invalid scanning of the wavelength scanning mechanism occupying the measurement time caused by the mismatch of the starting wavelengths of each channel, greatly reducing the time of a single measurement, and further improving the working efficiency of the solar spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the optical structure of the solar spectrometer according to an embodiment of the present invention;

[0013] Figure 2 A schematic diagram comparing the grating adjustment state of the prior art and the grating adjustment state of the present invention;

[0014] Figure 3 A schematic diagram of the spectrum overlap that occurs when measuring with a grating-type solar spectrometer;

[0015] Figure 4 A schematic diagram of the process of obtaining a complete spectrum by a single measurement of the solar spectrometer of the present invention;

[0016] Figure 5 The imaging of the photosensitive surface of the visible detector when the incident light is 285nm;

[0017] Figure 6 This is the imaging of the photosensitive surface of the infrared detector when the incident light is 650nm.

[0018] Explanation of the accompanying drawings: 1. first light homogenizing element; 2. second light homogenizing element; 3. first incident slit; 4. second incident slit; 5. first holographic concave grating; 6. first folding mirror; 7. second folding mirror; 8. second holographic concave grating; 9. visible detector; 10. third holographic concave grating; 11. third folding mirror; 12. fourth folding mirror; 13. fourth holographic concave grating; 14. infrared detector; 15. grating axis. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In order to solve the problem that the grating type solar spectrometer has spectral overlap during measurement, which increases the time of a single measurement and leads to low working efficiency, this embodiment provides a wide-band, high-efficiency solar spectrometer, such as Figure 1 As shown, it includes a first light homogenizing element 1, a second light homogenizing element 2, a first incident slit 3, a second incident slit 4, a visible channel (VIS channel) and an infrared channel (IR channel). Since the grating has much better light splitting uniformity and linearity than the prism, and the use of the grating can achieve high spectral resolution, the solar spectrometer of this embodiment uses the grating as a light splitting device. Among them, the visible channel includes a first holographic concave grating 5, a first folding mirror 6, a second folding mirror 7, a second holographic concave grating 8 and a visible detector 9 arranged in sequence along the optical path. After passing through the first light homogenizing element 1 and the first incident slit 3, the sunlight enters the visible channel, and after being diffracted by the grating and reflected by the folding mirror, it is finally imaged on the visible detector 9. The infrared channel includes a third holographic concave grating 10, a third folding mirror 11, a fourth folding mirror 12, a fourth holographic concave grating 13 and an infrared detector 14 which are arranged in sequence along the optical path. The sunlight enters the infrared channel after passing through the second light homogenizing element 2 and the second incident slit 4, and is finally imaged on the infrared detector 14 after being diffracted by the grating and reflected by the folding mirror.

[0021] In this embodiment, the first holographic concave grating 5, the second holographic concave grating 8, the third holographic concave grating 10, and the fourth holographic concave grating 13 are all mounted on the same set of grating axes 15, and the bottom surfaces of the first holographic concave grating 5 and the second holographic concave grating 8 are parallel to each other, the bottom surfaces of the third holographic concave grating 10 and the fourth holographic concave grating 13 are parallel to each other, and there is an angle between the bottom surfaces of the second holographic concave grating 8 and the third holographic concave grating 10, that is, the projections of the bottom surfaces of the second holographic concave grating 8 and the third holographic concave grating 10 on the plane perpendicular to the grating axis 15 form a preset angle. Comparison of the grating adjustment state in the existing grating type solar spectrometer and the grating adjustment state of the present invention Figure 2 shown.

[0022] The grating bottom angle of the visible channel and the infrared channel is calculated by the following steps 1 to 3 The value of .

[0023] Step 1: First, determine the wavelength ranges of the visible channel and the infrared channel, including the starting wavelength and the ending wavelength, according to the target spectral range.

[0024] For example, according to the overall design requirements of the solar spectrometer, the main design indicators of the optical structure system are obtained, as shown in Table 1.

[0025] Table 1 Design indexes of solar spectrometer optical structure system

[0026] index parameter Spectral range 0.285-0.7μm&0.65-2.4μm Spectral resolution VIS: 1nm&IR≤8nm .

[0027] According to the design indicators, the target spectral range is 0.285-0.7μm and 0.65-2.4μm, so the wavelength range of the visible channel is 285nm~700nm, the starting wavelength is 285nm, and the ending wavelength is 700nm. The wavelength range of the infrared channel is 650nm~2400nm, the starting wavelength is 650nm, and the ending wavelength is 2400nm.

[0028] Step 2: Calculate the grating rotation angle range corresponding to the visible channel and infrared channel respectively according to the grating diffraction formula and wavelength range, including the starting angle and the ending angle.

[0029] The grating diffraction formula is:

[0030]

[0031] in, is the grating diffraction order, is the incident wavelength, is the grating period, is the grating incident angle, is the grating diffraction angle.

[0032] The starting angle and the ending angle corresponding to the wavelength range of each channel can be calculated according to the above grating diffraction formula.

[0033] When the wavelength range is 285nm~700nm, the grating incident angle change corresponding to the visible channel, that is, the grating angle range is 42.283°~60.073°, the starting angle is 42.283°, the ending angle is 60.073°, and the difference between the ending angle and the starting angle is 17.79°, which is recorded as the first angle value.

[0034] When the wavelength range is 650nm~2400nm, the grating incident angle change corresponding to the infrared channel, that is, the grating angle range is 37.318°~55.578°, the starting angle is 37.318°, the ending angle is 55.578°, and the difference between the ending angle and the starting angle is 18.26°, which is recorded as the second angle value.

[0035] Step 3: Finally, calculate the difference between the starting angle of the visible channel and the starting angle of the infrared channel, and use the difference as the angle The value of .

[0036] In the same wavelength range, the existing grating type solar spectrometer has the same grating adjustment angle, so the incident angle changes from 37.318° to 60.073° during scanning, and the grating rotation angle is 22.755°. In this example, the adjustment angle of the grating of each channel is calculated based on the starting rotation angle of the two channels. For example, the angle between the visible channel grating and the infrared channel grating is set during adjustment. It is 42.283°-37.318°=4.965°. When the grating rotates, the wavelength corresponding to the visible channel is 285nm, and the wavelength corresponding to the infrared channel is 650nm, so that the starting wavelength of each channel during scanning is the starting wavelength of the wavelength range of the channel, which fundamentally solves the problem of invalid scanning of the wavelength scanning mechanism occupying measurement time caused by the mismatch of the starting wavelengths of each channel.

[0037] The solar spectrometer of the present embodiment performs spectral scanning. When scanning the entire spectrum, the grating angle or the rotation angle of the grating axis 15 only needs to cover the maximum value of the two channel grating angles, i.e., the first angle value and the second angle value, that is, 18.26°. It is not necessary to rotate 22.755° like the existing grating-type solar spectrometer, thereby saving the time of a single measurement.

[0038] In the existing grating-type solar spectrometer, the gratings of the two channels have the same adjustment angle and are driven by a common grating axis. Therefore, when the grating axis rotates to collect the spectrum, the spectra of the two channels will overlap. In order to collect the spectrum information of each channel, the grating axis rotates at a larger angle, so the single measurement time is longer. The process of obtaining a complete spectrum each time in the existing solution is as follows: Figure 3 As shown. In this embodiment, the gratings are installed according to the actual grating angle corresponding to the starting wavelength of each channel. There is an angle between the gratings of different channels, which greatly reduces the time of a single measurement. The spectral data of each channel in this embodiment are spliced ​​to obtain complete spectral data. The process of obtaining a complete spectrum each time is as shown in Figure 4 shown.

[0039] Since there is no spectral overlap in the present invention, the rotation angle of the grating axis 15 becomes smaller, so the measurement time of a single measurement can be greatly reduced, fundamentally solving the problem of invalid scanning of the wavelength scanning mechanism occupying the measurement time caused by the mismatch of the starting wavelengths of each channel, thereby improving the working efficiency of the solar spectrometer.

[0040] In the present invention, the four holographic concave gratings of the visible channel and the infrared channel share a set of grating axes 15, and the two channels collect spectral information, achieving miniaturization while realizing wide band coverage, and the entire band covers 285nm~2400nm. At the same time, since the holographic concave grating is used as the splitting element, it has high spectral resolution.

[0041] Optionally, the VIS channel in this embodiment uses a JY company's IV type concave holographic aberration correction grating, the grating size is 32mm×32mm, and the line density is 1200g / mm. In the working band range of 285nm~700nm, the grating incident angle changes from 42.283° to 60.073°, and the grating rotation angle is 17.79°.

[0042] Optionally, the IR channel uses a JY company's IV type concave holographic aberration correction grating, the grating size is Ф30mm, and the line density is 300g / mm. In the working band of 650nm to 2400nm, the grating incident angle changes from 37.318° to 55.578°, that is, scanning from 650nm to 2400nm, the grating rotation angle is 18.26°.

[0043] Optionally, according to the target spectral measurement band and spectral resolution, the visible detector 9 uses a Japanese R7378A photomultiplier tube. The infrared detector 14 is intended to use two types of indium gallium arsenide detectors, J22TE2-66C-R03M-1.7 and J23TE2-66C-R02M-2.4, produced by Judson Company, to achieve detection in the 650nm~1650nm band and 1650nm~2400nm band, respectively.

[0044] The visible detector 9 and the infrared detector 14 can also be implemented by other types of linear array or planar array photoelectric detectors with different response bands and different pixel sizes.

[0045] Figure 5 and Figure 6 The images of the photosensitive surfaces of the visible detector 9 and the infrared detector 14 are respectively when the incident light is 285nm and 650nm. Figure 5 and Figure 6 It can be seen that the imaging is located at the center of the detector, which can prove that the solar spectrometer of the present invention can make the starting wavelength of each channel the starting wavelength of the wavelength range of the channel, fundamentally solving the problem of invalid scanning of the wavelength scanning mechanism occupying the measurement time caused by the mismatch of the starting wavelengths of each channel.

[0046] Optionally, the first light homogenizing element 1 and the second light homogenizing element 2 may be diffuse transmission plates, diffuse reflection plates or a combination thereof, which is not limited here.

[0047] The above embodiment only takes one grating axis driving four gratings to rotate as an example to explain the technical solution of the present invention in detail. The grating axis can also drive more gratings to rotate, which will not be described in detail here.

[0048] The above-mentioned components of the solar spectrometer described in the present invention can be modified accordingly according to different design index requirements and replaced with devices with similar functions. This situation should also be considered to fall within the protection scope of the claims of the present invention.

[0049] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0050] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A wide-band, high-efficiency solar spectrometer, comprising a first light homogenizing element (1), a second light homogenizing element (2), a first incident slit (3), a second incident slit (4), a visible channel and an infrared channel; after sunlight passes through the first light homogenizing element (1) and the first incident slit (3), it enters the visible channel, and the visible channel comprises a first holographic concave grating (5), a first folding mirror (6), a second folding mirror (7), a second holographic concave grating (8) and a visible detector (9) arranged in sequence along the optical path; after sunlight passes through the second light homogenizing element (2) and the second incident slit (4), it enters the infrared channel, and the infrared channel comprises a third holographic concave grating (10), a third folding mirror (11), a fourth folding mirror (12), a fourth holographic concave grating (13) and an infrared detector (14) arranged in sequence along the optical path, characterized in that: The first holographic concave grating (5), the second holographic concave grating (8), the third holographic concave grating (10), and the fourth holographic concave grating (13) are mounted on the same set of grating axes (15), and the bottom surfaces of the first holographic concave grating (5) and the second holographic concave grating (8) are parallel to each other, the bottom surfaces of the third holographic concave grating (10) and the fourth holographic concave grating (13) are parallel to each other, and the projections of the bottom surfaces of the second holographic concave grating (8) and the third holographic concave grating (10) on a plane perpendicular to the grating axes (15) form an angle , angle The value of is determined by the following steps: Step 1: Determine the wavelength range of each of the visible channel and the infrared channel according to the target spectral range, including a starting wavelength and an ending wavelength; Step 2: Calculate the grating angle ranges corresponding to the visible channel and the infrared channel respectively according to the grating diffraction formula and the wavelength range, including the starting angle and the ending angle; Step 3: Calculate the difference between the starting angle of the visible channel and the starting angle of the infrared channel, and use the difference as the angle The value of .

2. A wide-band, high-efficiency solar spectrometer according to claim 1, characterized in that: When the solar spectrometer performs spectral scanning, the rotation angle of the grating axis (15) is equal to the maximum value of a first rotation angle value and a second rotation angle value, the first rotation angle value is the difference between the end rotation angle and the start rotation angle corresponding to the visible channel, and the second rotation angle value is the difference between the end rotation angle and the start rotation angle corresponding to the infrared channel.

3. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The size of the first holographic concave grating (5) and the second holographic concave grating (8) is 32 mm×32 mm, and the line density is 1200 g / mm.

4. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The size of the third holographic concave grating (10) and the fourth holographic concave grating (13) is Φ30 mm, and the line density is 300 g / mm.

5. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The visible detector (9) adopts a R7378A photomultiplier tube.

6. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The infrared detector (14) adopts two types of indium gallium arsenide detectors, namely J22TE2-66C-R03M-1.7 and J23TE2-66C-R02M-2.

4.

7. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The first light homogenizing element (1) and the second light homogenizing element (2) are diffuse transmission plates or diffuse reflection plates.

8. A wide-band, high-efficiency solar spectrometer according to claim 1 or 2, characterized in that: The wavelength range of the visible channel is 285nm-700nm, and the wavelength range of the infrared channel is 650nm-2400nm.

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