Water body hyperspectral remote sensing reflectivity measuring system and measuring method thereof

Abstract

The invention provides a water body hyperspectral remote sensing reflectivity measuring system and method, and the system comprises a fiber optic spectrometer which is provided with a light inlet; the optical fiber comprises three connecting ends, a first included angle is formed between the first connecting end and the second connecting end, a second included angle is formed between the second connecting end and the third connecting end, a second included angle is formed between the first connecting end and the third connecting end, the first included angle is smaller than the second included angle, and the first connecting end is connected with a light inlet of the optical fiber spectrometer; the optical fiber attenuator is connected with the second connecting end of the optical fiber; the cosine corrector is connected with the optical fiber attenuator, and the central axis of the cosine corrector is perpendicular to the horizontal plane; the steering engine is connected with the third connecting end of the optical fiber, the third connecting end can rotate along with rotation of the steering engine, the maximum rotation angle of the steering engine is a preset angle, and the angular bisector of the preset angle is parallel to the horizontal plane. According to the invention, the number of spectrometers is reduced, so that the cost is reduced. And the spectrograph can complete radiance measurement at different angles by utilizing steering engine control.

Description

Technical Field

[0001] The present invention belongs to the technical field of spectral measurement, and in particular relates to a water body hyperspectral remote sensing reflectance measurement system and a measurement method thereof. Background Art

[0002] Water spectrum measurement generally uses the above-water measurement method, that is, the water surface (L w ), Sky Light (L sky ) and the incident irradiance on the sea surface ( ), thereby obtaining remote sensing physical quantities such as water-leaving radiance, normalized water-leaving radiance and remote sensing reflectance.

[0003] The related technology provides a convenient water quality monitoring system with high spectral reflectance, including: a portable high spectral acquisition device for collecting high spectral data of the current monitoring point in real time.

[0004] In practice, the above-mentioned solutions require one person to operate a spectrometer and another to adjust the fiber's orientation, measuring the water surface, sky, and standard whiteboard in sequence. Alternatively, three spectrometers must be used to measure each of the three. The former is time-consuming and labor-intensive, requiring human personnel to perform the measurements. The latter is also expensive and difficult to implement. Summary of the Invention

[0005] The present invention provides a water body hyperspectral remote sensing reflectance measurement system and method. These solutions address the practical measurement issues of the aforementioned solutions, which require one person to operate a spectrometer and another to adjust the optical fiber orientation to measure the water surface, sky, and standard whiteboard in sequence; or to use three spectrometers to measure the three separately. The former is time-consuming and labor-intensive, requiring human operators to perform the measurements; the latter is technically difficult to implement due to high equipment costs.

[0006] The technical solution provided by the present invention is as follows: In one aspect, an embodiment of the present invention provides a water body hyperspectral remote sensing reflectance measurement system, the water body hyperspectral remote sensing reflectance measurement system comprising: A fiber optic spectrometer having a light inlet; An optical fiber, comprising three connection ends, wherein a first angle is formed between the first connection end and the second connection end, a second angle is formed between the second connection end and the third connection end, and between the first connection end and the third connection end, and the first angle is smaller than the second angle, and the first connection end is connected to the light inlet of the optical fiber spectrometer; an optical fiber attenuator connected to the second connection end of the optical fiber; a cosine corrector connected to the optical fiber attenuator, wherein the central axis of the cosine corrector is perpendicular to the horizontal plane; A rudder is connected with a third connection end of the optical fiber, and the third connection end can rotate with the rudder, wherein the maximum angle of rotation of the rudder is a preset angle, and an angle bisector of the preset angle is parallel to a horizontal plane.

[0007] In an alternative embodiment, a controller is further included, which is connected with the fiber spectrometer, the fiber attenuator and the rudder, and is used to control the fiber spectrometer, the fiber attenuator and the rudder.

[0008] In an alternative embodiment, the controller controls the rudder to rotate in a sequence of 0°→45°→-45°→0°.

[0009] In an alternative embodiment, the controller controls the rudder to rotate to 45° and -45° respectively, and triggers the fiber spectrometer to sample at the time.

[0010] In an alternative embodiment, the attenuation coefficient of the fiber attenuator is 0 dB~30 dB.

[0011] In an alternative embodiment, a detachable light shield is further included, which is arranged at the end of the rudder.

[0012] In an alternative embodiment, the optical fiber is a Y-type optical fiber.

[0013] In another aspect, the application further provides a water body hyperspectral remote sensing reflectance measurement method, comprising: The fiber attenuator is closed, the rudder is controlled to rotate to 45°, and then the fiber spectrometer is triggered to sample to obtain first sampling data as sky radiance; The fiber attenuator is opened, and the fiber spectrometer is triggered to sample to obtain second sampling data; The difference between the first sampling data and the second sampling data is obtained, and the difference is taken as irradiance; The fiber attenuator is closed, the rudder is controlled to rotate to -45°, and then the fiber spectrometer is triggered to sample to obtain water surface radiance; The remote sensing reflectance of the target water body is obtained based on the first sampling data, the second sampling data, the information of the water surface white cap, the random reflection of the water surface wave to the direct sunlight, the water surface radiance and the air-water interface reflectance.

[0014] In an alternative embodiment, the remote sensing reflectance of the target water body is obtained according to the following formula: = second sampling data - first sampling data wherein, R is the remote sensing reflectance of the target water body, L is the water surface radiance, r is the air-water interface reflectance, Lsky is the sky radiance, Lwhitehat is the information of the water surface white cap, Lg is the random reflection of the water surface wave to the direct sunlight, without any water body information, for the waveless and slight wave environment, Lg is 0.

[0015] The method provided by the embodiment of the application has at least the following beneficial effects: The system provided by the embodiment of the application can complete the measurement of radiance and irradiance by using one fiber spectrometer through the application of the fiber, the fiber attenuator and the cosine corrector, thereby reducing the number of spectrometers and the cost. The rudder control enables the spectrometer to complete the measurement of radiance at different angles. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the figures, exemplary embodiments of the present disclosure are shown.

[0017] Figure 1 A structure schematic diagram of a water body hyperspectral remote sensing reflectance measurement system is shown. Figure 2 A flowchart of a water body hyperspectral remote sensing reflectance measurement method is shown.

[0018] In the drawings, the same reference numbers are generally used to refer to same or similar elements throughout the various figures. 1-fiber spectrometer, 2-fiber attenuator, 3-cosine corrector, 4-rudder, 5-controller. DETAILED DESCRIPTION

[0019] Embodiments of the present disclosure will be described in more detail by referring to the drawings. Although the embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0020] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0021] See Figure 1 On the one hand, an embodiment of the present invention provides a water body hyperspectral remote sensing reflectance measurement system, which includes: a fiber optic spectrometer 1, an optical fiber, a fiber optic attenuator 2, a cosine corrector 3 and a servo 4.

[0022] The optical fiber spectrometer 1 has a light inlet.

[0023] The optical fiber includes three connection ends, wherein a first angle is formed between the first connection end and the second connection end, a second angle is formed between the second connection end and the third connection end, and between the first connection end and the third connection end, and the first angle is smaller than the second angle. The first connection end is connected to the light inlet of the optical fiber spectrometer 1.

[0024] The optical fiber attenuator 2 is connected to the second connection end of the optical fiber.

[0025] The cosine corrector 3 is connected to the optical fiber attenuator 2 , and the central axis of the cosine corrector 3 is perpendicular to the horizontal plane.

[0026] The servo 4 is connected to the third connection end of the optical fiber, and the third connection end can rotate with the rotation of the servo 4, wherein the maximum rotation angle of the servo 4 is a preset angle, and the bisector of the preset angle is parallel to the horizontal plane.

[0027] The method provided by the embodiment of the present invention has at least the following beneficial effects: The system provided by the present invention, including a fiber optic attenuator 2 and a cosine corrector 3, can measure both radiance and irradiance using a single fiber optic spectrometer 1, reducing the number of spectrometers and thus costs. Controlled by a servo 4, the spectrometer can measure radiance at various angles.

[0028] The fiber optic attenuator of the embodiment of the present invention can control whether light enters the optical fiber, and the cosine corrector is used to collect radiation (light) within a 180° solid angle, thereby eliminating the optical coupling problem caused by the geometric structure limitation of light collection and sampling in other sampling devices.

[0029] In an optional embodiment, a controller 5 is further included. The controller 5 is connected to the fiber optic spectrometer 1 , the fiber optic attenuator 2 and the steering gear 4 . The controller 5 is used to control the fiber optic spectrometer 1 , the fiber optic attenuator 2 and the steering gear 4 .

[0030] The controller 5 provided in the embodiment of the present invention may be a host computer. The host computer issues a rotation instruction to the servo 4. For example, the rotation instruction may be to rotate clockwise to 45°, counterclockwise to 45°, or counterclockwise to 90°. The specific rotation angle instruction may be set according to the measurement requirements of the spectrometer.

[0031] In an optional embodiment, the controller 5 controls the steering gear 4 to rotate in a sequence of 0°→45°→-45°→0°. Furthermore, the rotation instruction for controlling the rotation of the steering gear 4 may include rotating 0°, 45°, -45° or 0°. It should be noted that the above-mentioned rotation angle is based on the vertical plane and rotates within the vertical plane, that is, 0° is the horizontal line, 45° is above the horizontal line, and -45° is below the horizontal line. In an optional embodiment, the controller 5 controls the steering gear 4 to rotate to 45° and -45° respectively, triggering the fiber optic spectrometer 1 to perform sampling.

[0032] In an optional implementation, the attenuation coefficient of the optical fiber attenuator 2 is 0 dB to 30 dB.

[0033] In an optional embodiment, a detachable sunshade is further included, and the detachable sunshade is arranged at the end of the steering gear 4.

[0034] In an optional embodiment, the optical fiber is a Y-type optical fiber.

[0035] See Figure 2 On the other hand, the present invention also provides a method for measuring water body hyperspectral remote sensing reflectance, comprising: S1. The optical fiber attenuator is closed, and the steering gear 4 is controlled to rotate to 45 degrees, so that the optical fiber spectrometer 1 performs sampling to obtain the first sampling data as the sky radiance.

[0036] S2, the optical fiber attenuator 2 is turned on, so that the optical fiber spectrometer 1 performs sampling to obtain the second sampling data; S3. Obtain a difference between the first sampling data and the second sampling data, and use the difference as irradiance.

[0037] S4. The optical fiber attenuator is turned off, and the steering gear 4 is controlled to rotate to -45 degrees, so that the optical fiber spectrometer 1 performs sampling to obtain the water surface radiance.

[0038] S5. Obtain the remote sensing reflectivity of the target water body based on the first sampling data, the second sampling data, information about white caps on the water surface, random reflection of direct sunlight by water surface waves, water surface radiance, and air-water interface reflectivity.

[0039] In an optional embodiment, the remote sensing reflectance of the target water body is obtained according to the following formula: =Second sampling data - first sampling data in, is the remote sensing reflectance of the target water body, is the water surface radiance, r is the air-water interface reflectivity, is the sky radiance, For the information of white hat on the water surface, It is the random reflection of direct sunlight by water waves, without any water body information. For no-wave or micro-wave environments, Lg is 0.

[0040] The reflectivity of the air-water interface can be obtained by looking up the table. When measuring, select the time when there is no obvious white cap on the water surface and avoid direct sunlight. wc is 0.

[0041] While various embodiments of the present disclosure have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A water body hyperspectral remote sensing reflectance measurement system, characterized in that: The water body hyperspectral remote sensing reflectance measurement system comprises: A fiber optic spectrometer having a light inlet; An optical fiber, comprising three connection ends, wherein a first angle is formed between the first connection end and the second connection end, a second angle is formed between the second connection end and the third connection end, and between the first connection end and the third connection end, and the first angle is smaller than the second angle, and the first connection end is connected to the light inlet of the optical fiber spectrometer; an optical fiber attenuator connected to the second connection end of the optical fiber; a cosine corrector connected to the optical fiber attenuator, wherein the central axis of the cosine corrector is perpendicular to the horizontal plane; A servo is connected to the third connection end of the optical fiber, and the third connection end can rotate with the rotation of the servo, wherein the maximum rotation angle of the servo is a preset angle, and the bisector of the preset angle is parallel to the horizontal plane.

2. The water body hyperspectral remote sensing reflectance measurement system according to claim 1, characterized in that: It also includes a controller, which is connected to the fiber optic spectrometer, the fiber optic attenuator and the steering gear, and is used to control the fiber optic spectrometer, the fiber optic attenuator and the steering gear.

3. The water body hyperspectral remote sensing reflectance measurement system according to claim 2, characterized in that: The controller controls the steering gear to rotate in a sequence of 0°→45°→-45°→0°.

4. The water body hyperspectral remote sensing reflectance measurement system according to claim 3, characterized in that: The controller controls the steering gear to rotate to 45° and -45° respectively to trigger the fiber optic spectrometer to perform sampling.

5. The water body hyperspectral remote sensing reflectance measurement system according to claim 1, characterized in that: The attenuation coefficient of the optical fiber attenuator is 0 dB ~ 30dB.

6. The water body hyperspectral remote sensing reflectance measurement system according to claim 1, characterized in that: It also includes a detachable sunshade, which is arranged at the end of the steering gear.

7. The water body hyperspectral remote sensing reflectance measurement system according to claim 1, characterized in that: The optical fiber is a Y-type optical fiber.

8. A method for measuring water body hyperspectral remote sensing reflectance, characterized in that: include: The fiber optic attenuator is closed, and the servo is controlled to rotate to 45 degrees, so that the fiber optic spectrometer can start sampling and obtain the first sampling data as the sky radiance; The optical fiber attenuator is turned on to enable the optical fiber spectrometer to perform sampling to obtain second sampling data; Obtaining a difference between the first sampling data and the second sampling data, and using the difference as irradiance; The optical fiber attenuator is closed, and the steering gear is controlled to rotate to -45 degrees, so that the optical fiber spectrometer is sampled to obtain the water surface radiance; The remote sensing reflectivity of the target water body is obtained based on the first sampling data, the second sampling data, information of white caps on the water surface, random reflection of direct sunlight by water surface waves, water surface radiance and air-water interface reflectivity.

9. The method for measuring water body hyperspectral remote sensing reflectance according to claim 8, characterized in that: The remote sensing reflectivity of the target water body is obtained according to the following formula: =Second sampling data - first sampling data in, is the remote sensing reflectance of the target water body, is the water surface radiance, r is the air-water interface reflectivity, is the sky radiance, For the information of white hat on the water surface, It is the random reflection of direct sunlight by water waves, without any water body information. For no-wave or micro-wave environments, Lg is 0.

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