Spectral reflectance measurement method and system

Abstract

The present invention provides a spectral reflectance measurement method and system. The spectral reflectance measurement system includes an ambient light sensing module, a target spectrum acquisition module, and a data processing module. The ambient light sensing module acquires a measured ambient light spectrum at a target measurement time and transmits the measured ambient light spectrum to the data processing module. The target spectrum acquisition module acquires a measured target spectrum at the target measurement time and transmits the measured target spectrum to the data processing module. The data processing module determines the measured ambient light spectrum and the measured target spectrum corresponding to the same target wavelength, determines a measurement reference spectrum based on the measured ambient light spectrum and the determined mapping parameters, and determines the spectral reflectance of the object under test based on the measurement target spectrum and the measurement reference spectrum. The measurement reference spectrum is a spectrum of a second ambient light, and the mapping parameters represent a mapping relationship between the reference spectrum and the ambient light spectrum. The technical solution of the present invention enables accurate calculation of the spectral reflectance of the object under test.

Description

[Technical Field]

[0001] The present invention relates to the technical field of optical processing, and in particular to a spectral reflectance measurement method and system. [Background technology]

[0002] Hyperspectral imaging refers to the combination of imaging technology and hyperspectral technology to acquire two-dimensional geometric space and one-dimensional spectral information of the object under measurement, thereby obtaining continuous narrowband image data with hyperspectral resolution.

[0003] Hyperspectral technology uses very narrow, continuous spectral channels (as opposed to three channels such as RGB (Red, Green, Blue)) to obtain spectral information of an object. This technology collects electromagnetic wave data (i.e., spectral information) from multiple spectral channels of an object and, based on the characteristics of these data, obtains information of interest, such as the molecular composition, relative content, and material type of the object. In the fields of remote sensing and material measurement, spectral information of an object can be obtained based on the reflected light intensity of the object. However, due to the inconsistency in the spectral components of the illuminating light source, the spectral lines obtained under different light sources will not match. Therefore, spectral information of an object cannot be obtained based solely on the reflected light intensity of the object.

[0004] To solve the problem of inconsistencies in the spectral components of the illuminating light sources, which results in inconsistencies in the spectral lines obtained under different light sources, it is possible to incorporate spectral reflectance as an evaluation feature of the object under test, i.e., to obtain spectral information of the object under test in combination with spectral reflectance.Spectral reflectance refers to the ratio of the reflected luminous flux of the object under test in a certain wavelength band to the incident luminous flux of the same wavelength band. Summary of the Invention [Problem to be solved by the invention]

[0005] In conclusion, calculating the spectral reflectance of an object is an important factor in realizing hyperspectral imaging. However, an effective method for accurately calculating the spectral reflectance of an object has not yet been established. [Means for solving the problem]

[0006] The present invention provides a spectral reflectance measurement system including an ambient light sensing module, a target spectrum acquisition module, and a data processing module, the ambient light sensing module is used to collect a measured ambient light spectrum at a target measurement time and send the measured ambient light spectrum to the data processing module, the measured ambient light spectrum being a spectrum of a first ambient light, the first ambient light being the ambient light sensed by the ambient light sensing module; the target spectrum collection module is used to collect a measurement target spectrum at a target measurement time and transmit the measurement target spectrum to the data processing module, the measurement target spectrum being a spectrum of second ambient light reflected by an object to be measured, the second ambient light being ambient light sensed by the target spectrum collection module; the data processing module determines a measurement environment light spectrum and a measurement target spectrum corresponding to the same target wavelength, determines a measurement reference spectrum based on the measurement environment light spectrum and the determined mapping parameter, and is used to determine a spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum, wherein the measurement reference spectrum is the spectrum of the second ambient light, and the mapping parameter represents a mapping relationship between the reference spectrum and the ambient light spectrum; A spectral reflectance measurement system is provided.

[0007] The present invention provides a method for determining a measurement environment light spectrum and a measurement target spectrum corresponding to the same target wavelength, wherein the measurement environment light spectrum is collected at the same time as the measurement target spectrum, the measurement environment light spectrum is a spectrum of a first environment light, and the measurement target spectrum is a spectrum of a second environment light reflected by an object to be measured; determining a measurement reference spectrum based on the measured ambient light spectrum and the determined mapping parameter, wherein the measurement reference spectrum is the spectrum of the second ambient light, and the mapping parameter represents a mapping relationship between the reference spectrum and the ambient light spectrum; determining a spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum; A method for measuring spectral reflectance is provided.

[0008] As can be seen from the above technical solutions, in the embodiments of the present invention, by pre-calibrating the mapping parameters between the reference spectrum and the ambient light spectrum, the spectral reflectance of the object under test can be determined based on the measured ambient light spectrum and the measured target spectrum corresponding to the same target wavelength and the mapping parameters. This allows the spectral reflectance of the object under test to be accurately calculated, thereby realizing fast, real-time, efficient, and accurate acquisition of the spectral reflectance of the object under test. The spectral reflectance of the object under test can be continuously acquired in real time on-site, improving the convenience and real-timeness of acquiring the spectral reflectance of on-site features (i.e., the object under test). During use, a calibration object (e.g., a standard whiteboard) can be used to perform a single calibration (i.e., calibration mapping parameters), eliminating the need to repeatedly collect data on the calibration object. This allows the spectral reflectance to be acquired under different weather conditions and different solar elevation angles. Through solar elevation angle / attitude angle correction, the accuracy of calculating the spectral reflectance in various use cases can be improved. [Brief explanation of the drawings]

[0009] In order to more clearly describe the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention are briefly introduced below. Obviously, the accompanying drawings in the following description are only some of the embodiments described in the present invention, and those skilled in the art can obtain other accompanying drawings based on these accompanying drawings of the embodiments of the present invention. [Figure 1] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 2A] 1 is a schematic diagram showing the layout of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 2B] 1 is a schematic diagram showing the layout of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram illustrating a calibration process of mapping parameters according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram illustrating a calculation process of spectral reflectance according to an embodiment of the present invention. [Figure 5A] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 5B] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 5C] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 5D] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 5E] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 5F] 1 is a schematic diagram illustrating the structure of a spectral reflectance measurement system according to an embodiment of the present invention. [Figure 6A] FIG. 1 is a schematic diagram illustrating a real-life scenario application according to an embodiment of the present invention. [Figure 6B] FIG. 1 is a schematic diagram illustrating a real-life scenario application according to an embodiment of the present invention. [Figure 6C]FIG. 1 is a schematic diagram illustrating a real-life scenario application according to an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic diagram showing the flow of a spectral reflectance measurement method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The terms used in the embodiments of the present invention are for the purpose of describing particular embodiments only and are not intended to limit the present invention. Unless the context clearly indicates otherwise, the singular forms "a," "the," and "said" used in the embodiments and claims of the present invention are intended to include the plural forms as well. It should also be understood that the term "and / or" used herein refers to any and all possible combinations of one or more of the associated listed items.

[0011] In embodiments of the present invention, terms such as first, second, and third may be used to describe various types of information, but it should be understood that such information should not be limited to these terms. These terms are merely used to distinguish the same types of information from one another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. Furthermore, depending on the context, the term "if" may be interpreted as "when," "when," or "in response to a determination."

[0012] An embodiment of the present invention provides a spectral reflectance measurement system, and Fig. 1 is a schematic diagram showing the structure of the spectral reflectance measurement system. As shown in Fig. 1, the spectral reflectance measurement system may include at least an ambient light sensing module 11, a target spectrum collecting module 12, and a data processing module 13.

[0013] The ambient light sensing module 11 is used to collect a measured ambient light spectrum at a target measurement time and transmit the measured ambient light spectrum to the data processing module 13. The measured ambient light spectrum may be a spectrum of a first ambient light, and the first ambient light may be the ambient light sensed by the ambient light sensing module 11. For example, for all ambient lights, the ambient light sensing module 11 may sense a first ambient light that is a part of the ambient light, and the first ambient light has different values ​​at different times. The measured ambient light spectrum is a spectrum corresponding to the first ambient light.

[0014] The target spectrum collection module 12 is used to collect a measurement target spectrum at a target measurement time (i.e., the measurement time of the measurement ambient light spectrum) and transmit the measurement target spectrum to the data processing module 13. The measurement target spectrum may be a spectrum of second ambient light reflected by the object under test, and the second ambient light may be ambient light sensed by the target spectrum collection module 12. For example, for all ambient lights, the target spectrum collection module 12 may sense a second ambient light that is a part of the ambient light, and the second ambient light is different from the first ambient light. The second ambient light has different values ​​at different times. The measurement target spectrum is a spectrum of the second ambient light reflected by the object under test.

[0015] The data processing module 13 is used to determine a measurement ambient light spectrum and a measurement target spectrum corresponding to the same target wavelength, and to determine a measurement reference spectrum based on the measurement ambient light spectrum and the determined mapping parameter. Exemplarily, the measurement reference spectrum may be a spectrum of a second ambient light, and the mapping parameter may be used to represent a mapping relationship between the reference spectrum and the ambient light spectrum. The data processing module 13 can further determine the spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum.

[0016] In one possible embodiment, the ambient light sensing module 11 is used to collect a measured ambient light spectrum for each wavelength in a first wavelength set, and the target spectrum collection module 12 is used to collect a measured target spectrum for each wavelength in a second wavelength set, where the first wavelength set is a subset of the second wavelength set. When the data processing module 13 determines the measured ambient light spectrum and the measured target spectrum corresponding to the same target wavelength, it specifically determines each wavelength in the second wavelength set as a target wavelength, collects a measured target spectrum corresponding to the target wavelength from the target spectrum collection module 12 for each target wavelength, determines whether the target wavelength is present in the first wavelength set, and if so, obtains a measured ambient light spectrum corresponding to the target wavelength from the ambient light sensing module 11. If not, it is used to determine the measured ambient light spectrum corresponding to the target wavelength based on the measured ambient light spectra of at least two wavelengths collected by the ambient light sensing module 11. For example, a first matching wavelength and a second matching wavelength are selected from a first wavelength set, and the measured ambient light spectrum corresponding to the target wavelength is determined based on the measured ambient light spectrum corresponding to the first matching wavelength and the measured ambient light spectrum corresponding to the second matching wavelength, where the first matching wavelength is a wavelength in the first wavelength set that is closest to the target wavelength but smaller than the target wavelength, and the second matching wavelength is a wavelength in the first wavelength set that is closest to the target wavelength but larger than the target wavelength.

[0017] In one possible embodiment, the data processing module 13 is further configured to determine a maximum spectral value in the measured ambient light spectrum and the measured target spectrum. If the maximum spectral value is smaller than a predetermined spectral minimum, the data processing module 13 adjusts the first exposure time currently used by the ambient light sensing module 11 to a second exposure time, controls the ambient light sensing module 11 to collect the measured ambient light spectrum based on the second exposure time, and controls the target spectrum collection module 12 to collect the measured target spectrum based on the second exposure time. The second exposure time is greater than the first exposure time. Alternatively, if the maximum spectral value is greater than the predetermined spectral maximum, the data processing module 13 adjusts the first exposure time currently used by the ambient light sensing module 11 to a third exposure time, controls the ambient light sensing module 11 to collect the measured ambient light spectrum based on the third exposure time, and controls the target spectrum collection module 12 to collect the measured target spectrum based on the third exposure time. The third exposure time is less than the first exposure time.

[0018] In one possible embodiment, the ambient light sensing module 11 can further collect position data and transmit the position data to the data processing module 13. When the data processing module 13 determines a measurement reference spectrum based on the measured ambient light spectrum and the determined mapping parameter, the data processing module 13 specifically determines an angular parameter based on the position data, and determines a measurement reference spectrum based on the measured ambient light spectrum, the angular parameter, and the mapping parameter, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angular parameter.

[0019] For example, if the position data is attitude information of the ambient light sensing module 11, the angle parameter may be an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of the ambient light sensing module 11, the angle parameter may be a zenith angle corresponding to the longitude and latitude information.

[0020] In one possible embodiment, the process of determining the mapping parameters may include:

[0021] The ambient light sensing module 11 collects a calibration ambient light spectrum at a target calibration time and transmits the calibration ambient light spectrum to the data processing module 13. The calibration ambient light spectrum may be a spectrum of a first ambient light, and the first ambient light may be the ambient light sensed by the ambient light sensing module 11.

[0022] The target spectrum collection module 12 collects a calibration target spectrum at a target calibration time and transmits the calibration target spectrum to the data processing module 13. The calibration target spectrum is a spectrum of second ambient light reflected by a calibration object, and the second ambient light is ambient light sensed by the target spectrum collection module 12.

[0023] The data processing module 13 determines a calibration ambient light spectrum and a calibration target spectrum corresponding to the same target wavelength, and determines a calibration reference spectrum based on the calibration target spectrum and a set spectral reflectance of the calibration object. The calibration reference spectrum may be the spectrum of the second ambient light. Furthermore, the data processing module 13 determines a mapping parameter based on the calibration reference spectrum and the calibration ambient light spectrum. The mapping parameter represents a mapping relationship between the reference spectrum and the ambient light spectrum.

[0024] In one possible embodiment, the ambient light sensing module 11 can further collect position data and transmit the position data to the data processing module 13. When the data processing module 13 determines a mapping parameter based on the calibration reference spectrum and the calibration ambient light spectrum, the data processing module 13 specifically determines an angle parameter based on the position data, and determines the mapping parameter based on the angle parameter, the calibration reference spectrum, and the calibration ambient light spectrum, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angle parameter.

[0025] For example, if the position data is attitude information of the ambient light sensing module 11, the angle parameter may be an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of the ambient light sensing module 11, the angle parameter may be a zenith angle corresponding to the longitude and latitude information.

[0026] In one possible embodiment, the ambient light sensing module 11 includes at least a light homogenizing path and a multispectral sensor, the light homogenizing path being positioned opposite the multispectral sensor, the ambient light being homogenized by the light homogenizing path before being transmitted to the multispectral sensor, and the multispectral sensor collecting measured ambient light spectra of multiple wavelengths. Alternatively, the ambient light sensing module 11 includes at least a light homogenizing path, an optical fiber, and an optical fiber spectrometer, one end of the optical fiber being connected to the optical fiber spectrometer and the other end of the optical fiber being connected to the light homogenizing path, the ambient light being homogenized by the light homogenizing path before being transmitted to the optical fiber spectrometer via the optical fiber, and the optical fiber spectrometer collecting measured ambient light spectra of multiple wavelengths. In the above method, the number of wavelengths of the measured ambient light spectrum that can be acquired by the optical fiber spectrometer is greater than the number of wavelengths of the measured ambient light spectrum that can be acquired by the multispectral sensor.

[0027] Illustratively, the ambient light sensing module 11 may further include an attitude sensor and / or a position sensor, where the attitude sensor is used to collect attitude information and the position sensor is used to collect longitude and latitude information.

[0028] In one possible embodiment, the target spectrum collection module 12 includes at least a lens and an optical fiber spectrometer, the lens is connected to the optical fiber spectrometer, the lens collects light after the object under test has reflected the ambient light and transmits it to the optical fiber spectrometer, and the optical fiber spectrometer collects the measurement target spectrum of multiple wavelengths. Alternatively, the target spectrum collection module 12 may include a lens and an imaging spectrometer, the lens is connected to the imaging spectrometer, the lens collects light after the object under test has reflected the ambient light and transmits it to the imaging spectrometer, and the imaging spectrometer collects the measurement target spectrum of multiple wavelengths.

[0029] As can be seen from the above technical solutions, in the embodiments of the present invention, by pre-calibrating the mapping parameters between the reference spectrum and the ambient light spectrum, the spectral reflectance of the object under test can be determined based on the measured ambient light spectrum and the measured target spectrum corresponding to the same target wavelength and the mapping parameters. This allows the spectral reflectance of the object under test to be accurately calculated, thereby realizing fast, real-time, efficient, and accurate acquisition of the spectral reflectance of the object under test. The spectral reflectance of the object under test can be continuously acquired in real time on-site, improving the convenience and real-timeness of acquiring the spectral reflectance of on-site features (i.e., the object under test). During use, a calibration object (e.g., a standard whiteboard) can be used to perform a single calibration (i.e., calibration mapping parameters), eliminating the need to repeatedly collect data on the calibration object. This allows the spectral reflectance to be acquired under different weather conditions and different solar elevation angles. Through solar elevation angle / attitude angle correction, the accuracy of calculating the spectral reflectance in various use cases can be improved.

[0030] Hereinafter, a spectral reflectance measurement system according to an embodiment of the present invention will be described in relation to a specific application scenario.

[0031] Before describing the technical solutions of the embodiments of the present invention, some concepts related to the present invention will be introduced.

[0032] Hyperspectral technology: A technique for obtaining spectral information of an object using very narrow, continuous spectral channels. This technology collects electromagnetic wave data (i.e., spectral information) from multiple spectral channels of the object and, based on the characteristics of these data, can obtain information of interest, such as the molecular composition, relative content, and material type of the object. In the visible to short-wavelength infrared range, spectral resolution can be measured down to the nanometer (nm) level and typically has multiband characteristics. The number of spectral channels can be up to several hundred or more, and each spectral channel is typically continuous. Hyperspectral imaging refers to the combination of imaging technology and hyperspectral technology to obtain two-dimensional geometric space and one-dimensional spectral information of the object, obtaining continuous narrowband image data with hyperspectral resolution.

[0033] Spectral reflectance: Spectral reflectance refers to the ratio of the reflected luminous flux of a feature in a certain wavelength band to the incident luminous flux in that wavelength band. Features selectively reflect electromagnetic waves of different wavelengths and have their own characteristics. A feature is an object (also called a target) on the ground, and in this embodiment, is also called a measured object or a calibration object. A measured object is a feature for which spectral reflectance is to be calculated, and a calibration object is a feature with a known spectral reflectance. Obviously, the formula for calculating spectral reflectance is to divide the target spectrum reflected by the feature by the reference spectrum of incident light received by the feature.

[0034] When a light source strikes the surface of an object, the object selectively reflects electromagnetic waves of different wavelengths. Spectral reflectance is the ratio of the luminous flux reflected by an object in a certain wavelength band to the luminous flux incident on the object, and is an attribute of the object's surface. Spectral reflectance represents the color of the object itself, records information about the object's color, and is information that represents the material of the object's surface. Luminous flux is the radiant power that can be perceived by the human eye and is equal to the product of the radiant energy of a certain wavelength band per unit time and the relative visibility of that wavelength band. The luminous flux in this embodiment can be written as a spectrum, i.e., the luminous flux can be expressed in terms of a spectrum.

[0035] Ambient light sensing: Ambient light refers to sunlight and its scattered light. Ambient light sensing refers to acquiring the incident light flux when the ambient light is incident on a ground object. The incident light flux is usually acquired by a sensor with multiple (hyper)spectral channels, and the incident light flux is used to calculate the spectral reflectance of the ground object.

[0036] Multispectral sensor: A multispectral sensor is a sensor that uses a photosensitive element with multiple broadband (>10 nm) and discontinuous spectral channels to obtain light intensity information of the corresponding channels about an object, i.e., it is used to obtain spectral information.

[0037] Cosine response: When light strikes the imager detector at an oblique angle, the photocurrent output should follow the cosine law: the illuminance in this case should be equal to the normal illuminance for normal incidence of light times the cosine of the angle of incidence.

[0038] In situ: Refers to the location where an event occurs. It refers to the original, normal, natural part or location, and does not change the position of the object being measured or damage the object being measured by transportation, etc.

[0039] Ambient light spectrum: The spectral reflectance measurement system may be provided with an ambient light sensing module 11, which is used to sense the spectrum of the ambient light (i.e., incident luminous flux), and this spectrum is referred to as the ambient light spectrum. Note that the ambient light that the ambient light sensing module 11 can sense is only a portion of the total ambient light, and for ease of distinction, the ambient light that the ambient light sensing module 11 can sense is referred to as the first ambient light, that is, the ambient light spectrum is the spectrum corresponding to the first ambient light, that is, the spectrum generated by the first ambient light.

[0040] Reference spectrum: The spectral reflectance measurement system may be provided with a target spectrum collection module 12, which is used to sense the spectrum of the ambient light after it is reflected by an object (i.e., the reflected luminous flux). The spectrum of the ambient light before it is reflected by an object is the reference spectrum (i.e., the incident luminous flux), and this spectrum of the ambient light (i.e., the reference spectrum) is the spectrum that the target spectrum collection module 12 can sense.

[0041] It should be noted that the target spectrum collection module 12 cannot directly obtain the reference spectrum. The spectrum that the target spectrum collection module 12 can sense is called the reference spectrum. However, what the target spectrum collection module 12 can obtain is the spectrum after the reference spectrum is reflected by the object, that is, it can obtain the spectrum after the reference spectrum is reflected.

[0042] The ambient light that the target spectrum collection module 12 can sense is only a portion of all ambient light, and for ease of distinction, the ambient light that the target spectrum collection module 12 can sense is referred to as the second ambient light, i.e., the reference spectrum is the spectrum corresponding to the second ambient light, i.e., the spectrum generated by the second ambient light.

[0043] It should be noted that the second ambient light that the target spectrum collecting module 12 can sense is different from the first ambient light that the ambient light sensing module 11 can sense, so there is a difference between the reference spectrum and the ambient light spectrum. Because there is a difference between the reference spectrum and the ambient light spectrum and the target spectrum collecting module 12 cannot directly obtain the reference spectrum, it is necessary to calibrate the mapping relationship between the reference spectrum and the ambient light spectrum, so that after the ambient light spectrum is obtained, the reference spectrum can be inferred based on the ambient light spectrum and the mapping relationship.

[0044] Target spectrum: The spectral reflectance measurement system can be provided with a target spectrum collection module 12, which is used to sense the spectrum of the reference spectrum after it is reflected by an object, and this reflected spectrum is referred to as the target spectrum (i.e., reflected luminous flux). Obviously, when the reference spectrum is reflected by an object, the target spectrum is obtained. That is, the target spectrum is equal to the reference spectrum multiplied by the spectral reflectance of the object.

[0045] Because of the above relationship, if the reference spectrum and target spectrum are known, the spectral reflectance of the object can be obtained, and if the target spectrum and spectral reflectance of the object are known, the reference spectrum can be obtained.

[0046] To calculate the spectral reflectance of an object under test, an embodiment of the present invention proposes a spectral reflectance measurement system, which is an in-situ online real-time spectral reflectance measurement system. By pre-calibrating the mapping parameters between the reference spectrum and the ambient light spectrum, the spectral reflectance of the object under test can be accurately calculated, enabling rapid, real-time, efficient, and accurate acquisition of the object's spectral reflectance. For example, by pre-calibrating the spectral reflectance measurement system using a standard reflectance board, the spectral reflectance of the object under test can be continuously acquired in real time on-site, improving the convenience and real-time nature of acquiring the spectral reflectance of on-site features (i.e., the object under test). During use, a single calibration (i.e., calibration mapping parameters) is required using a calibration object (e.g., a standard whiteboard, a standard reflectance board, etc.), allowing spectral reflectance to be acquired without repeatedly collecting data from the calibration object.

[0047] In an embodiment of the present invention, the spectral reflectance measurement system may include an ambient light sensing module 11, a target spectrum collecting module 12, and a data processing module 13. Here, the ambient light sensing module 11 is used to acquire radiation spectra (i.e., ambient light spectra) of a target area at different times and different solar elevation angles, and transmit the ambient light spectra to the data processing module 13. The target spectrum collecting module 12 is used to acquire radiation spectra (i.e., target spectra) reflected by an object after being illuminated by sunlight at different times and different solar elevation angles, and transmit the target spectra to the data processing module 13. The data processing module 13 is used for pre-processing of the ambient spectrum and the target spectrum, exposure control, mapping parameter calibration, spectral reflectance calculation, and data inversion.

[0048] The preprocessing function performs preprocessing, such as filtering, on input data (e.g., the ambient light spectrum and the target spectrum). The exposure control function automatically adjusts the exposure time and the average number of spectral data collections of the ambient light sensing module 11 and the target spectrum acquisition module 12 based on the ambient light spectrum and the target spectrum. The mapping parameter calibration function calibrates the difference in spectral acquisition between the ambient light sensing module 11 and the target spectrum acquisition module 12 and determines the input-output relationship of the spectral reflectance measurement system, i.e., calibrates the mapping parameters between the reference spectrum and the ambient light spectrum. The spectral reflectance calculation function calculates the spectral reflectance of the object to be measured based on the calibrated mapping parameters. For example, the spectral reflectance of the object to be measured is calculated based on the ambient light spectrum of the ambient light sensing module 11, the target spectrum of the target spectrum acquisition module 12, and the mapping parameters. The data inversion function can introduce the calculated spectral reflectance into a material parameter inversion model and perform inversion calculations of specific parameters based on the spectral reflectance of the object to be measured.

[0049]

[0009] Embodiments of the present invention relate to a process for calibrating mapping parameters and calculating the spectral reflectance of a measurement target based on the calibrated mapping parameters. In the process for calibrating mapping parameters, a calibration object can be placed under a spectral reflectance measurement system. The calibration object is an object with known spectral reflectance, and in this case, a mapping parameter between a reference spectrum and an ambient light spectrum is calibrated, as shown in Figure 2A. When calculating the spectral reflectance of the measurement target based on the calibrated mapping parameters, a measurement target is placed under the spectral reflectance measurement system. The measurement target is an object with unknown spectral reflectance, the spectral reflectance of which is to be calculated, as shown in Figure 2B.

[0050] Illustratively, the calibration process of mapping parameters involves an ambient light spectrum, a reference spectrum, and a target spectrum, and for ease of distinction, the ambient light spectrum of the process is referred to as a calibration ambient light spectrum, the reference spectrum of the process is referred to as a calibration reference spectrum, and the target spectrum of the process is referred to as a calibration target spectrum.

[0051] When calculating the spectral reflectance of a measured object based on calibrated mapping parameters, the ambient light spectrum, reference spectrum, and target spectrum are referred to as the measured ambient light spectrum, the reference spectrum of the process, and the target spectrum of the process, respectively.

[0052] The calibration process of the mapping parameters may include the following, as shown in FIG.

[0053] In step 301, the ambient light sensing module 11 collects a calibration ambient light spectrum at a target calibration time and sends the calibration ambient light spectrum to the data processing module 13. The calibration ambient light spectrum may be a spectrum of a first ambient light, and the first ambient light may be the ambient light sensed by the ambient light sensing module 11.

[0054] In step 302, the target spectrum collection module 12 collects a calibration target spectrum at a target calibration time and transmits the calibration target spectrum to the data processing module 13. The calibration target spectrum is a spectrum of a calibration object reflecting second ambient light, and the second ambient light is the ambient light sensed by the target spectrum collection module 12.

[0055] For example, the calibration object is an object with known spectral reflectance, such as a whiteboard or a standard reflectance board. The type of the calibration object is not limited, and in the following embodiments, a whiteboard will be used as an example.

[0056] For example, in an outdoor open environment, it is ensured that the ambient light illuminance in the collection range of the target spectrum collection module 12 is the same as the ambient light illuminance in the sensing range of the ambient light sensing module 11, and that the light environment above and below is not shaded. A whiteboard is placed within the collection range of the target spectrum collection module 12, and the whiteboard must completely cover the collection range of the target spectrum collection module 12. A schematic diagram of the whiteboard placement is shown in FIG. 2A. After the position of the whiteboard is adjusted, the target spectrum collection module 12 and the ambient light sensing module 11 synchronously collect spectra, i.e., collect spectra at the same time (this time will be referred to as the target calibration time). The spectrum collected by the ambient light sensing module 11 is the calibration ambient light spectrum, and the spectrum collected by the target spectrum collection module 12 is the calibration target spectrum.

[0057] The target calibration time may be multiple times, such as time T1, time T2, etc., so that the ambient light sensing module 11 may collect a calibration ambient light spectrum at time T1, the target spectrum collection module 12 may collect a calibration target spectrum at time T1, the ambient light sensing module 11 may collect a calibration ambient light spectrum at time T2, the target spectrum collection module 12 may collect a calibration target spectrum at time T2, etc.

[0058] In step 303, the data processing module 13 determines whether to adjust the exposure time. If yes, adjust the exposure time and instruct the ambient light sensing module 11 to collect a calibration ambient light spectrum based on the adjusted exposure time, i.e., re-execute step 301, and instruct the target spectrum collecting module 12 to collect a calibration target spectrum based on the adjusted exposure time, i.e., re-execute step 302. If no adjustment is required, step 304 may be executed.

[0059] For example, after receiving the calibration ambient light spectrum (which may be multiple calibration ambient light spectral values) and the calibration target spectrum (which may be multiple calibration target spectral values), the data processing module 13 may determine the maximum value among all the calibration ambient light spectra and all the calibration target spectra, which is referred to as the maximum spectral value.

[0060] If the maximum spectral value is smaller than a predetermined spectral minimum value (which may be set empirically), the first exposure time may be adjusted to a second exposure time, which is greater than the first exposure time, i.e., the value of the first exposure time is increased, and the first exposure time is the exposure time currently used by the ambient light sensing module 11 and the target spectrum acquisition module 12. Next, the data processing module 13 sends the second exposure time to the ambient light sensing module 11, which collects a calibration ambient light spectrum based on the second exposure time, i.e., the ambient light sensing module 11 collects the calibration ambient light spectrum at the second exposure time, and the process returns to step 301. Similarly, the data processing module 13 sends the second exposure time to the target spectrum acquisition module 12, which collects a calibration target spectrum based on the second exposure time, i.e., the target spectrum acquisition module 12 collects the calibration target spectrum at the second exposure time, and the process returns to step 302.

[0061] If the maximum spectral value is greater than a predetermined spectral maximum value (which may be set empirically), the first exposure time may be adjusted to a third exposure time, which is smaller than the first exposure time, i.e., the value of the first exposure time is decreased. Next, the data processing module 13 sends the third exposure time to the ambient light sensing module 11, which collects a calibration ambient light spectrum based on the third exposure time, and the process returns to step 301. Similarly, the data processing module 13 sends the third exposure time to the target spectrum acquisition module 12, which collects a calibration target spectrum based on the third exposure time, and the process returns to step 302.

[0062] If the maximum spectral value is not smaller than the predetermined spectral minimum value and not greater than the predetermined spectral maximum value, i.e., if the maximum spectral value is between the predetermined spectral minimum value and the predetermined spectral maximum value, it indicates that the first exposure time currently used by the ambient light sensing module 11 and the target spectrum collection module 12 is appropriate and does not need to be adjusted, and the data processing module 13 may determine not to adjust the exposure time and perform step 304.

[0063] In summary, since the light intensity of sunlight varies greatly depending on the time and weather, it is impossible to use a uniform exposure time to obtain the calibration ambient light spectrum and the calibration target spectrum. Therefore, the data processing module 13 can analyze whether the exposure time is appropriate, i.e., whether to adjust the exposure time. If the exposure time needs to be adjusted, it adjusts the exposure time and instructs the ambient light sensing module 11 and the target spectrum acquisition module 12 to adjust the exposure time.

[0064] In step 304, the data processing module 13 performs spectral pre-processing on the calibration ambient light spectrum and the calibration target spectrum, including, but not limited to, data filtering, dark noise removal, and the like.

[0065] In step 305, the data processing module 13 determines a mapping relationship between the reference spectrum and the ambient light spectrum based on the calibration ambient light spectrum and the calibration target spectrum, and saves the mapping relationship between the reference spectrum and the ambient light spectrum.

[0066] In one possible embodiment, the implementation process of step 305 may include:

[0067] Step 3051: Determine a calibration ambient light spectrum and a calibration target spectrum corresponding to the same target wavelength.

[0068] For example, with respect to the calibration ambient light spectrum and the calibration target spectrum at the target calibration time, the calibration ambient light spectrum may be a calibration ambient light spectrum of multiple wavelengths, and the calibration target spectrum may be a calibration target spectrum of multiple wavelengths. For example, the ambient light sensing module 11 is used to collect a calibration ambient light spectrum for each wavelength in a first wavelength set, and the target spectrum collection module 12 is used to collect a calibration target spectrum for each wavelength in a second wavelength set, where the first wavelength set is a subset of the second wavelength set, for example, the first wavelength set includes wavelength a1, wavelength a3, and wavelength a5, and the second wavelength set includes wavelength a1, wavelength a2, wavelength a3, wavelength a4, and wavelength a5. Of course, the above is just an example, and the number of wavelengths in the first wavelength set may be much greater than 3, for example, tens, and the number of wavelengths in the second wavelength set may be much greater than 5, for example, hundreds. There is no particular limitation to this, and the number of wavelengths may also be referred to as the number of spectral channels, for example, the number of spectral channels may be 3 and 5, etc.

[0069] In summary, the data processing module 13 can obtain multiple calibration ambient light spectra and multiple calibration target spectra at the same target calibration time; for example, the data processing module 13 can obtain a calibration ambient light spectrum b1 of wavelength a1, a calibration ambient light spectrum b3 of wavelength a3, a calibration ambient light spectrum b5 of wavelength a5, a calibration target spectrum c1 of wavelength a1, a calibration target spectrum c2 of wavelength a2, a calibration target spectrum c3 of wavelength a3, a calibration target spectrum c4 of wavelength a4, and a calibration target spectrum c5 of wavelength a5.

[0070] The data processing module 13 may treat each wavelength of the second wavelength set (e.g., wavelength a1, wavelength a2, wavelength a3, wavelength a4, and wavelength a5) as a target wavelength. For wavelength a1, calibration ambient light spectrum b1 and calibration target spectrum c1 are the calibration ambient light spectrum and calibration target spectrum corresponding to the same target wavelength a1. For wavelength a3, calibration ambient light spectrum b3 and calibration target spectrum c3 are the calibration ambient light spectrum and calibration target spectrum corresponding to the same target wavelength a3. For wavelength a5, calibration ambient light spectrum b5 and calibration target spectrum c5 are the calibration ambient light spectrum and calibration target spectrum corresponding to the same target wavelength a5.

[0071] For wavelength a2, since wavelength a2 does not exist in the first wavelength set, a calibrated ambient light spectrum corresponding to wavelength a2 may be calculated based on at least two of calibrated ambient light spectrum b1, calibrated ambient light spectrum b3, and calibrated ambient light spectrum b5. This will be referred to as calibrated ambient light spectrum b2, and this calculation method is not limited to this. For example, calibrated ambient light spectrum b2 may be calculated as follows: A first matching wavelength and a second matching wavelength are selected from the first wavelength set, and the first matching wavelength is a wavelength in the first wavelength set that is closest to wavelength a2 and smaller than the target wavelength, e.g., wavelength a1, and the second matching wavelength is a wavelength in the first wavelength set that is closest to wavelength a2 and larger than the target wavelength, e.g., wavelength a3. Then, a calibrated ambient light spectrum b2 of wavelength a2 is calculated based on the calibrated ambient light spectrum b1 of wavelength a1 and the calibrated ambient light spectrum b3 of wavelength a3, and the calibrated ambient light spectrum b2 is obtained by, for example, performing an interpolation operation, an averaging operation, a weighting operation (the weighting can be set arbitrarily) on the calibrated ambient light spectrum b1 and the calibrated ambient light spectrum b3. As long as the calibrated ambient light spectrum b2 can be obtained, there are no limitations on this calculation method.

[0072] So far, for wavelength a2, the calibration ambient light spectrum b2 and the calibration target spectrum c2 are the calibration ambient light spectrum and the calibration target spectrum corresponding to the same target wavelength a2.

[0073] For wavelength a4, since wavelength a4 does not exist in the first wavelength set, a calibration ambient light spectrum b4 corresponding to wavelength a4 may be calculated. For example, the calibration ambient light spectrum b4 for wavelength a4 may be calculated based on the calibration ambient light spectrum b3 for wavelength a3 and the calibration ambient light spectrum b5 for wavelength a5, and this calculation method is not limited to this. So far, for wavelength a4, the calibration ambient light spectrum b4 and the calibration target spectrum c4 are the calibration ambient light spectrum and the calibration target spectrum corresponding to the same target wavelength a4.

[0074] In summary, a calibration ambient light spectrum and a calibration target spectrum corresponding to each target wavelength can be obtained, and for each target wavelength, subsequent steps can be performed based on the calibration ambient light spectrum and the calibration target spectrum corresponding to the target wavelength to obtain mapping parameters corresponding to the target wavelength and store the mapping relationship, that is, the mapping parameters corresponding to each target wavelength are stored. Hereinafter, for convenience of explanation, one target wavelength will be taken as an example, and subsequent steps will be performed based on the calibration ambient light spectrum and the calibration target spectrum corresponding to the target wavelength.

[0075] Step 3052: For each target wavelength, determine a calibration reference spectrum corresponding to the target wavelength based on the calibration target spectrum corresponding to the target wavelength and the spectral reflectance of the calibration object, where the calibration reference spectrum may be the spectrum of a second ambient light, and the second ambient light is the ambient light sensed by the target spectrum collection module 12.

[0076] For example, since the calibration target spectrum is obtained after the calibration reference spectrum is reflected by a calibration object, if the spectral reflectances of the calibration target spectrum and the calibration object are known, the calibration reference spectrum can be determined, for example, by dividing the calibration target spectrum by the spectral reflectance.

[0077] Step 3053: for each target wavelength, determine a mapping parameter corresponding to the target wavelength based on the calibration reference spectrum corresponding to the target wavelength and the calibration ambient light spectrum corresponding to the target wavelength, and store the mapping parameter, which is used to represent the mapping relationship between the reference spectrum and the ambient light spectrum.

[0078] In one possible embodiment, the mapping relationship between the reference spectrum and the ambient light spectrum satisfies a functional relationship such as y=f(x,k), where f represents a functional relationship that can be set based on experience and f is a function relating to x and k. There is no limitation on the expression of this functional relationship f, and it can be arbitrarily set as f(x,k)=x / k, although of course this is a simple expression form and the functional relationship f will be more complicated in actual applications. y represents the reference spectrum, x represents the ambient light spectrum, and k represents a mapping parameter between the reference spectrum and the ambient light spectrum.

[0079] In the above equation, y represents the reference spectrum and is a known value, i.e., represents the calibration reference spectrum corresponding to the target wavelength; x represents the ambient light spectrum and is a known value, i.e., represents the calibration ambient light spectrum corresponding to the target wavelength; the functional relationship f is preset; and k is an unknown value, i.e., a mapping parameter that needs to be determined. Therefore, the mapping parameter k can be obtained by substituting the calibration reference spectrum y and the calibration ambient light spectrum x into the equation y=f(x,k).

[0080] In one possible embodiment, the ambient light sensing module 11 can further collect position data and transmit the position data to the data processing module 13. In step 3053, the data processing module 13 can determine an angle parameter based on the position data, and determine the mapping parameter based on the angle parameter, the calibration reference spectrum, and the calibration ambient light spectrum, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angle parameter. For example, if the position data is attitude information of the ambient light sensing module 11, the angle parameter can be an attitude angle corresponding to the attitude information. For example, the attitude information is the attitude angle of the ambient light sensing module 11, and the attitude angle of the ambient light sensing module 11 can be directly determined. And / or, if the position data is longitude and latitude information of the ambient light sensing module 11, the angle parameter can be a zenith angle corresponding to the longitude and latitude information. For example, the solar zenith angle can be determined based on the longitude and latitude information of the ambient light sensing module 11. This determination method is not limited. In addition, the angle parameters may include the zenith angle of the calibration object in addition to the zenith angle of the sun. For example, the zenith angle of the calibration object may be set in advance, and the zenith angle of the calibration object may be set to 0 degrees and 90 degrees for vertically downward collection and horizontal collection, for example.

[0081] For example, the mapping relationship between the reference spectrum, the ambient light spectrum, and the angular parameter satisfies a functional relationship such as y=f(x, k, p), where f represents a functional relationship that can be set based on experience and f is a function relating to x, p, and k. The expression of this functional relationship f is not limited and can be set arbitrarily. x represents the ambient light spectrum, y represents the reference spectrum, and k represents a mapping parameter between the angular parameter, the reference spectrum, and the ambient light spectrum.

[0082] p represents an angle parameter, and the angle parameter p includes at least one of the attitude angle p1 of the ambient light sensing module 11, the zenith angle p2 of the sun, and the zenith angle p3 of the calibration object, for example, y = f(x, k, p1, p2, p3), or y = f(x, k, p1, p2), or y = f(x, k, p1, p3), or y = f(x, k, p2, p3), or y = f(x, k, p1), or y = f(x, k, p2), or y = f(x, k, p3), although of course the above are only a few examples and are not limiting. For convenience of explanation, the following explanation will be given taking y = f(x, k, p1, p2, p3) as an example.

[0083] In the above equation, y represents the calibration reference spectrum corresponding to the target wavelength, x represents the calibration ambient light spectrum corresponding to the target wavelength, the functional relationship f is preset, p1 represents the attitude angle of the ambient light sensing module 11, p2 represents the zenith angle of the sun, and p3 represents the zenith angle of the calibration object. It is clear that x, y, p1, p2, and p3 are all known values, and k is an unknown value, that is, a mapping parameter that needs to be determined. Therefore, x, y, p1, p2, and p3 can be substituted into the equation y=f(x, k, p1, p2, p3) to obtain the mapping parameter k.

[0084] In one possible embodiment, the above equation y=f(x, k, p1, p2, p3) may be replaced by the equation y=f(x, z, k, p1, p2, p3), where z represents the spectral reflectance of the whiteboard and is a known value, i.e., x, y, z, p1, p2, p3 can be substituted into the equation y=f(x, z, k, p1, p2, p3) to obtain the mapping parameter k.

[0085] In one possible embodiment, for the calibration process of the mapping parameters, a mapping relationship model may be obtained that can map the ambient light spectrum to the reference spectrum to obtain the mapping parameter k.

[0086] For example, the ambient light sensing module 11 can collect a calibration ambient light spectrum, which can be denoted as x (also denoted as IE), and because the reference spectrum is not equal to the calibration ambient light spectrum x due to discrepancies in many factors in the spectral reflectance measurement system, such as the light homogenization path, the transmittance of the lens, the diffraction efficiency of the splitter element, the detector response, the number of spectral channels, and the spectral reflectance of the whiteboard, it is necessary to calibrate the mapping parameters, i.e., it is necessary to calibrate the mapping relationship model between the reference spectrum y (also denoted as Iref) and the calibration ambient light spectrum x. The mapping relationship model is used to represent the input-output relationship of the spectral reflectance measurement system, and for example, the mapping relationship model can be y=f(x, p1, p2, p3, z, k). In the above equation, the input-output relationship can be expressed as f, where f is related to parameters such as x, p1, p2, p3, z, and k, where x(IE) represents the ambient light spectrum, p1 represents the attitude angle of the ambient light sensing module 11, p2 represents the solar zenith angle, p3 represents the zenith angle of the calibration object, z represents the spectral reflectance of the whiteboard, k represents a mapping parameter, i.e., a value that needs to be determined in the calibration process, and y(Iref) represents the reference spectrum. Obviously, the above mapping relationship model y=f(x, p1, p2, p3, z, k) represents the mapping relationship between the ambient light spectrum and the reference spectrum, and it is only necessary to calculate the mapping parameter k.

[0087] Of course, the above mapping relationship model y=f(x, p1, p2, p3, z, k) is just an example, and in actual applications, it is possible to remove at least one parameter among p1, p2, p3, and z, and this mapping relationship model is not limited.

[0088] After the mapping parameters are obtained, the mapping parameters can be saved, and in subsequent calculations of the spectral reflectance of the object to be measured, there is no need to obtain a reference spectrum using a whiteboard, but the reference spectrum can be obtained by directly mapping using the ambient light spectrum of the ambient light sensing module 11 and the mapping parameters.

[0089] The calculation process of the spectral reflectance of the object to be measured, as shown in FIG. 4, may include:

[0090] In step 401, the ambient light sensing module 11 collects a measured ambient light spectrum at a target measurement time and sends the measured ambient light spectrum to the data processing module 13. The measured ambient light spectrum may be a spectrum of a first ambient light, and the first ambient light may be the ambient light sensed by the ambient light sensing module 11.

[0091] In step 402, the target spectrum collection module 12 collects a measurement target spectrum at a target measurement time and transmits the measurement target spectrum to the data processing module 13. The measurement target spectrum is a spectrum of a second ambient light reflected by a measurement object, and the second ambient light is the ambient light sensed by the target spectrum collection module 12.

[0092] By way of example, the object to be measured is an object whose spectral reflectance is to be calculated, but is not limited thereto.

[0093] The target measurement time may be any time such as time t1, and the ambient light sensing module 11 may collect a measured ambient light spectrum at time t1, and the target spectrum collecting module 12 may collect a measured target spectrum at time t1.

[0094] For example, in an outdoor open environment, it is possible to ensure that the ambient light illuminance in the collection range of the target spectrum collection module 12 is the same as the ambient light illuminance in the sensing range of the ambient light sensing module 11, and that the light environment above and below is not shaded, and the object to be measured is placed in the collection range of the target spectrum collection module 12.

[0095] In step 403, the data processing module 13 determines whether to adjust the exposure time. If yes, adjust the exposure time and instruct the ambient light sensing module 11 to collect a measured ambient light spectrum based on the adjusted exposure time, i.e., re-execute step 401, and instruct the target spectrum collecting module 12 to collect a measured target spectrum based on the adjusted exposure time, i.e., re-execute step 402. If no adjustment is required, step 404 may be executed.

[0096] For example, after receiving multiple measured ambient light spectral values ​​and multiple measured target spectral values, the data processing module 13 may determine the maximum value, i.e., the maximum spectral value, among all the measured ambient light spectra and all the measured target spectra. If the maximum spectral value is smaller than a predetermined spectral minimum value, the data processing module 13 may adjust the first exposure time to a second exposure time, where the second exposure time is greater than the first exposure time, and the first exposure time is the exposure time currently used by the ambient light sensing module 11 and the target spectrum acquisition module 12. The second exposure time is then sent to the ambient light sensing module 11, which collects the measured ambient light spectrum based on the second exposure time, and the second exposure time is sent to the target spectrum acquisition module 12, which collects the measured target spectrum based on the second exposure time. If the maximum spectral value is greater than the predetermined spectral maximum value, the first exposure time may be adjusted to a third exposure time, where the third exposure time is smaller than the first exposure time, and the third exposure time is sent to the ambient light sensing module 11, which collects a measured ambient light spectrum based on the third exposure time, and the third exposure time is sent to the target spectrum collection module 12, which collects a measured target spectrum based on the third exposure time. If the maximum spectral value is not smaller than the predetermined spectral minimum value and not greater than the predetermined spectral maximum value, the first exposure time currently used by the ambient light sensing module 11 and the target spectrum collection module 12 is appropriate, and step 404 is executed.

[0097] In step 404, the data processing module 13 performs spectral pre-processing on the measurement ambient light spectrum and the measurement target spectrum, including, but not limited to, data filtering, dark noise removal, and the like.

[0098] In step 405, the data processing module 13 determines the spectral reflectance of the object to be measured based on the measured ambient light spectrum, the measured target spectrum, and the mapping relationship between the reference spectrum and the ambient light spectrum.

[0099] In one possible embodiment, the implementation process of step 405 may include:

[0100] Step 4051: Determine the measurement ambient light spectrum and the measurement target spectrum corresponding to the same target wavelength.

[0101] In one possible embodiment, the ambient light sensing module 11 is used to collect a measured ambient light spectrum for each wavelength in a first wavelength set, and the target spectrum collection module 12 is used to collect a measured target spectrum for each wavelength in a second wavelength set, where the first wavelength set is a subset of the second wavelength set. The data processing module 13 identifies each wavelength in the second wavelength set as a target wavelength, collects a measured target spectrum corresponding to the target wavelength from the target spectrum collection module 12, determines whether the target wavelength is present in the first wavelength set, and if so, obtains a measured ambient light spectrum corresponding to the target wavelength from the ambient light sensing module 11. If not, determines a measured ambient light spectrum corresponding to the target wavelength based on the measured ambient light spectra of at least two wavelengths collected by the ambient light sensing module 11. For example, the data processing module 13 selects a first matching wavelength and a second matching wavelength from the first wavelength set, and determines a measured ambient light spectrum corresponding to the target wavelength based on the measured ambient light spectrum corresponding to the first matching wavelength and the measured ambient light spectrum corresponding to the second matching wavelength. The first matching wavelength is the wavelength in the first wavelength set that is closest to and smaller than the target wavelength, and the second matching wavelength is the wavelength in the first wavelength set that is closest to and larger than the target wavelength.

[0102] The implementation process of step 4051 is similar to that of step 3051, so it will not be repeated here.

[0103] In summary, the measurement ambient light spectrum and the measurement target spectrum corresponding to each target wavelength can be obtained, and for each target wavelength, the subsequent steps are performed based on the measurement ambient light spectrum and the measurement target spectrum corresponding to the target wavelength to obtain the spectral reflectance corresponding to the target wavelength. For convenience of explanation, one target wavelength is taken as an example, and the subsequent steps are performed based on the measurement ambient light spectrum and the measurement target spectrum corresponding to the target wavelength.

[0104] Step 4052: Determine a measurement reference spectrum based on the measured ambient light spectrum and a mapping parameter (i.e., a mapping parameter between a reference spectrum and an ambient light spectrum), where the measurement reference spectrum may be a spectrum of a second ambient light.

[0105] In one possible embodiment, the mapping relationship between the reference spectrum and the ambient light spectrum satisfies a functional relationship such as y=f(x,k), where f represents a functional relationship that can be set based on experience, y represents the reference spectrum, x represents the ambient light spectrum, and k represents a mapping parameter between the reference spectrum and the ambient light spectrum.

[0106] In step 4052, the mapping parameter k is a known value, and x is the measured ambient light spectrum corresponding to the target wavelength, and since these are also known values, the mapping parameter k and the measured ambient light spectrum x can be substituted into the equation y=f(x,k) to obtain the reference spectrum y, which is the measured reference spectrum corresponding to the target wavelength.

[0107] In one possible embodiment, the ambient light sensing module 11 can further collect position data and transmit the position data to the data processing module 13. In step 4052, the data processing module 13 can determine an angle parameter based on the position data, and determine the measured reference spectrum based on the measured ambient light spectrum, the angle parameter, and the mapping parameter, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angle parameter. For example, if the position data is attitude information of the ambient light sensing module 11, the angle parameter can be an attitude angle corresponding to the attitude information. For example, the attitude information is the attitude angle of the ambient light sensing module 11, and the attitude angle of the ambient light sensing module 11 can be directly determined. And / or, if the position data is longitude and latitude information of the ambient light sensing module 11, the angle parameter can be a zenith angle corresponding to the longitude and latitude information. For example, the solar zenith angle can be determined based on the longitude and latitude information of the ambient light sensing module 11. This determination method is not limited. In addition, the angle parameters may include the zenith angle of the object being measured in addition to the zenith angle of the sun. For example, the zenith angle of the object being measured may be set in advance, and the zenith angle of the object being measured may be set to 0 degrees and 90 degrees for vertically downward collection and horizontal collection, for example.

[0108] For example, the mapping relationship between the reference spectrum, the ambient light spectrum, and the angular parameter satisfies a functional relationship such as y=f(x,k,p), where f represents the functional relationship that can be set based on experience, x represents the ambient light spectrum, y represents the reference spectrum, and k represents the mapping parameter. p represents an angular parameter, and the angular parameter p includes at least one of the attitude angle p1 of the ambient light sensing module 11, the zenith angle p2 of the sun, and the zenith angle p3 of the object to be measured, such as y=f(x,k,p1,p2,p3), or y=f(x,k,p1,p2), or y=f(x,k,p1,p3), or y=f(x,k,p2,p3), or y=f(x,k,p1), or y=f(x,k,p2), or y=f(x,k,p3). However, the above are merely a few examples and are not limiting. For convenience of explanation, the following explanation will be given using y=f(x, k, p1, p2, p3) as an example.

[0109] In the above equation, y represents the measurement reference spectrum corresponding to the target wavelength, x represents the measured ambient light spectrum corresponding to the target wavelength, p1 represents the attitude angle of the ambient light sensing module 11, p2 represents the zenith angle of the sun, p3 represents the zenith angle of the object to be measured, k is a mapping parameter, it is clear that x, k, p1, p2, p3 are all known values, and y is an unknown value, that is, the measurement reference spectrum that needs to be determined, so that x, k, p1, p2, p3 can be substituted into the equation y=f(x, k, p1, p2, p3) to obtain the measurement reference spectrum y corresponding to the target wavelength.

[0110] In one possible embodiment, the above equation y=f(x, k, p1, p2, p3) may be replaced by the equation y=f(x, z, k, p1, p2, p3), where z represents the spectral reflectance of the whiteboard and is a known value, i.e., x, k, z, p1, p2, p3 can be substituted into the equation y=f(x, z, k, p1, p2, p3) to obtain the measurement reference spectrum y.

[0111] Of course, the above mapping relationship model y=f(x, z, k, p1, p2, p3) is just an example, and in actual applications, it is possible to remove at least one parameter among p1, p2, p3, and z, and this mapping relationship model is not limited.

[0112] In the above equation, the attitude angle p1 of the ambient light sensing module 11, the zenith angle p2 of the sun, and the zenith angle p3 of the object to be measured function as parameters for correcting inaccuracies in the measurement reference spectrum calculated due to changes in the attitude of the ambient light sensing module 11, inconsistencies in the attitude of the object to be measured, excessive changes in the zenith angle of the sun, etc., i.e., parameters for obtaining a more accurate measurement reference spectrum.

[0113] In summary, a measured reference spectrum corresponding to a target wavelength is determined based on a measured ambient light spectrum corresponding to the target wavelength and a mapping parameter (mapping parameter between the reference spectrum and the ambient light spectrum) corresponding to the target wavelength.

[0114] Step 4053: Determine the spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum. For example, the spectral reflectance of the object to be measured can be calculated by the formula R=IO / Iref, where IO represents the measurement target spectrum corresponding to the target wavelength, Iref represents the measurement reference spectrum corresponding to the target wavelength, and R represents the spectral reflectance of the object to be measured corresponding to the target wavelength, thereby obtaining the spectral reflectance of the object to be measured.

[0115] In one possible embodiment, after obtaining the spectral reflectance of the object, the inversion of material parameters can also be performed, i.e., the data processing module 13 introduces the spectral reflectance into a corresponding inversion model according to the application scenario, inverts the spectral reflectance, and obtains the parameters of the object related to the spectral reflectance.

[0116] In one possible embodiment, the ambient light sensing module 11 includes at least a light uniformization path and a multispectral sensor, the light uniformization path is disposed opposite the multispectral sensor, the ambient light is uniformized by the light uniformization path and then transmitted to the multispectral sensor, and the multispectral sensor collects ambient light spectra of multiple wavelengths.

[0117] For example, the light homogenizing path can homogenize light rays transmitted at different angles of incidence, and the transmitted light is scattered at multiple angles regardless of the angle of incidence. The homogenized light is transmitted to a multispectral sensor. The multispectral sensor can measure the spectral intensity of multiple wavelength bands and receive the homogenized light. When light rays enter the light homogenizing path at different angles, the photocurrent output of the multispectral sensor follows a cosine response. The multispectral sensor can be a multichannel photodiode, a multichannel spectral sensor, or a single-point fiber optic spectrometer.

[0118] Alternatively, the ambient light sensing module 11 may include at least a light homogenizing path, an optical fiber, and an optical fiber spectrometer, one end of the optical fiber being connected to the optical fiber spectrometer and the other end of the optical fiber being connected to the light homogenizing path, the ambient light being homogenized by the light homogenizing path and then transmitted to the optical fiber spectrometer via the optical fiber, and the optical fiber spectrometer collecting ambient light spectra of multiple wavelengths. Compared with the above method, the multispectral sensor is replaced with the optical fiber spectrometer, the light homogenizing path is connected to the optical fiber spectrometer via the optical fiber, and the other structure is similar to that described above and will not be repeated here.

[0119] In the above-described method, the number of wavelengths of the measurement ambient light spectrum that can be acquired by the optical fiber spectrometer is greater than the number of wavelengths of the measurement ambient light spectrum that can be acquired by the multispectral sensor. For example, the optical fiber spectrometer can collect the ambient light spectrum of hundreds of wavelengths, while the multispectral sensor can collect the ambient light spectrum of tens of wavelengths.

[0120] In one possible embodiment, the ambient light sensing module 11 may further include an attitude sensor (e.g., a gyro sensor) and / or a position sensor (e.g., a GPS), where the attitude sensor is used to collect attitude information (e.g., the attitude angle of the ambient light sensing module 11 relative to the horizontal plane) and the position sensor is used to collect longitude and latitude information.

[0121] In one possible embodiment, the target spectrum collection module 12 may include a lens and a hyperspectral imager. The lens can capture or receive light from the target area and is connected to the hyperspectral imager directly or via an optical fiber. The lens may be an imaging lens or a collimating lens. The hyperspectral imager can obtain spectral information of different wavelength bands reflected or emitted by the target area captured or received by the lens, i.e., the target spectrum. The hyperspectral imager may be a single-point optical fiber spectrometer, a push broom imaging spectrometer, or a staring imaging spectrometer.

[0122] For example, the target spectrum collection module 12 may include at least a lens and an optical fiber spectrometer (e.g., a single-point optical fiber spectrometer), where the lens is connected (directly or via an optical fiber) to the optical fiber spectrometer, and the lens can collect light after the object under test has reflected ambient light and transmit it to the optical fiber spectrometer, which collects target spectra of multiple wavelengths. Alternatively, the target spectrum collection module 12 may include at least a lens and an imaging spectrometer (e.g., a push-broom imaging spectrometer or a staring imaging spectrometer), where the lens is connected to the imaging spectrometer, and the lens can collect light after the object under test has reflected ambient light and transmit it to the imaging spectrometer, which collects target spectra of multiple wavelengths.

[0123] The following describes the connection relationship, structure, and function of the ambient light sensing module 11, the target spectrum collecting module 12, and the data processing module 13 in accordance with some specific application scenarios.

[0124] Application Scenario 1

[0125] As shown in FIG. 5A, 1 is the light homogenization path of the ambient light sensing module 11, which can homogenize light rays transmitted at different incident angles. The transmitted light is scattered at multiple angles regardless of the incident angle, and the homogenized light is transmitted to the multispectral sensor. 2 is the multispectral sensor of the ambient light sensing module 11, which can acquire the spectral intensities of multiple wavelengths and receive the homogenized light. When light rays enter the light homogenization path at different angles, the photocurrent output of the multispectral sensor follows a cosine response, allowing the spectrum of the target area (i.e., the ambient light spectrum) to be collected. 3 is an attitude sensor (e.g., a gyro sensor) and a position sensor (e.g., a GPS), which can acquire information such as the latitude, longitude, and attitude angle of the ambient light sensing module 11. 4 is the lens of the target spectrum collection module 12, which has the function of collecting light. 5 is the optical fiber spectrometer (e.g., a single-point optical fiber spectrometer) of the target spectrum collection module 12, which is directly connected to the lens and can collect the spectrum of the target area (i.e., the target spectrum). 6 is an industrial control board, i.e., a data processing module 13, which controls the multispectral sensor, the attitude sensor, the position sensor, the optical fiber spectrometer, etc., and has the functions of receiving, processing, uploading, and storing data.

[0126] As shown in Figure 5A, the light homogenizing path 1 is positioned opposite the multispectral sensor 2 and is attached facing vertically upward, pointing toward the zenith, with the orientation sensor, position sensor 3, light homogenizing path 1, and multispectral sensor 2 maintained in the same orientation. The lens 4 and optical fiber spectrometer 5 are attached facing vertically downward to collect the spectrum of the area below.

[0127] In some cases, the object to be measured may be the whiteboard of the above embodiment, or may be the object to be measured, as shown in Figure 5A for the object to be measured, and in Figure 5B for the whiteboard.

[0128] Sunlight hits the light homogenization path 1 and the object to be measured simultaneously with the same solar radiation amount. The sunlight passes through the light homogenization path 1 and is received by the multispectral sensor 2, which obtains the ambient light spectrum. The optical signal from the object to be measured is collected by the lens 4 and then dispersed by the optical fiber spectrometer 5, which obtains the target spectrum.

[0129] The industrial control board 6 receives data transmitted from the multispectral sensor 2, the optical fiber spectrometer 5, and the attitude and position sensor 3, and performs exposure control on the multispectral sensor 2 and the optical fiber spectrometer 5. After the exposure is complete, it performs pre-processing of the data. After the pre-processing is complete, it maps the ambient light spectrum to a reference spectrum according to pre-calibrated mapping parameters, and calculates the spectral reflectance based on the reference spectrum and the target spectrum.

[0130] Application scenario 2

[0131] As shown in FIG. 5C , 7 is an optical fiber and 8 is a single-point optical fiber spectrometer. Unlike Application Scenario 1, it is also possible to use a single-point optical fiber spectrometer instead of a multispectral sensor, and the optical fiber spectrometer collects a larger number of channels (i.e., a larger number of channels in the ambient light spectrum). One end of the optical fiber 7 is connected to the optical fiber spectrometer 8, and the other end of the optical fiber 7 is placed in the light homogenization path 1 to collect the ambient light. After being guided through the light homogenization path 1 and the optical fiber 7, the ambient light enters the optical fiber spectrometer 8 and is dispersed therein. Finally, the optical fiber spectrometer 8 obtains the ambient light spectrum.

[0132] In the application scenario, the process of calibration and spectral reflectance calculation remains unchanged and will not be repeated here.

[0133] Application Scenario 3

[0134] As shown in Figure 5D, 9 is an imaging spectrometer. Unlike Application Scenario 1, a single-point optical fiber spectrometer (hyperspectral detector) can be used instead of the imaging spectrometer. The imaging spectrometer 9 can be combined with lens 4 to acquire a hyperspectral image of the entire imaging area. Lens 4 and imaging spectrometer 9 remain attached facing downward to acquire a hyperspectral image of the imaging area below. The imaging spectrometer 9 may be a staring snapshot type, which acquires a hyperspectral image by reconstruction or sorting after a single exposure. The imaging spectrometer 9 may also be a staring adjustable filter type or a time-domain Fourier transform type, which acquires a hyperspectral image by multiple exposures in the time domain. The imaging spectrometer 9 may also be a push-broom type, equipped with an internal or external push-broom device and acquiring a hyperspectral image by multiple exposures of the push-broom in the spatial domain.

[0135] In the above application scenario, the calibration and spectral reflectance calculation processes are similar. The calibration process requires additional extraction of spectral data of the whiteboard area in the hyperspectral image when calculating mapping parameters. The reflectance calculation process provides a hyperspectral reflectance cube instead of a spectral reflectance curve.

[0136] Application Scenario 4

[0137] As shown in Fig. 5E, unlike Application Scenario 1 or Application Scenario 3, it is possible to tilt the ambient light sensing module 11 or the entire spectral reflectance measurement system to operate at a certain angle. Fig. 5E shows a state in which the entire spectral reflectance measurement system is tilted to operate at a certain angle for Application Scenario 3, and it is also possible to tilt only the ambient light sensing module 11 to operate at a certain angle. Alternatively, it is also possible to tilt the entire spectral reflectance measurement system to operate at a certain angle or tilt the ambient light sensing module 11 to operate at a certain angle for Application Scenario 1, but this will not be repeated here.

[0138] The ambient light spectrum can be corrected by acquiring the attitude angle using an attitude sensor (e.g., a gyro sensor). In other words, the mapping parameters in the above embodiments may be related to the attitude angle of the ambient light sensing module 11, and can also be applied to angle changes due to changes in the external environment, such as angle changes due to waves when the spectral reflectance measurement system is mounted on a pontoon or a ship.

[0139] Application Scenario 5

[0140] 5F , unlike Application Scenario 1 or Application Scenario 3, the target spectrum collection module 12 can be mounted horizontally or at another angle and operate to acquire a target spectrum perpendicular to the ground. By acquiring the angle of the object to be measured relative to the zenith, the reference spectrum can be corrected to obtain the spectral reflectance in the current scenario. That is, the above-mentioned mapping parameters may be related to the zenith angle of the object to be measured and the zenith angle of the sun.

[0141] FIG. 5F shows that for application scenario 3, the target spectrum collection module 12 is mounted to operate horizontally or at another angle, and for application scenario 1, the target spectrum collection module 12 can also be mounted to operate horizontally or at another angle.

[0142] Of course, the above application scenarios 1 to 5 are merely examples of the connection relationships and structures of the ambient light sensing module 11, the target spectrum collecting module 12, and the data processing module 13, and are not limited thereto.

[0143] Application scenario 6: Application scenario for in-situ fixed-point water quality monitoring

[0144] As shown in Figure 6A, this application scenario, based on application scenario 2, applies the spectral reflectance measurement system to in-situ fixed-point water quality monitoring. Under sunlight, sunlight hits the light uniformization material and the water body simultaneously with the same solar irradiance. The sunlight passes through the light uniformization path and is received by the optical fiber spectrometer as the ambient light spectrum. It is then mapped using the ambient light mapping relationship model (i.e., mapping parameters) to obtain the reference spectrum for calculating the spectral reflectance. The water body's upstream transpired radiation signal is received by the lens and then received by the optical fiber spectrometer as the target spectrum for calculating the spectral reflectance. The industrial control board calculates the spectral reflectance of the transpired radiation, inputs the spectral reflectance into the pre-installed water body parameter inversion model, and performs water quality inversion on the spectral reflectance to obtain the water quality parameter value for the current water quality. Without any restrictions on the water quality inversion process, all-weather in-situ online water quality monitoring is realized.

[0145] For example, the water quality parameter values ​​of the current water quality are as follows: chlorophyll a: 0-500 ug / L, total nitrogen: 0-20 mg / L, total phosphorus: 0-2 mg / L, transparency: 0-5 m, potassium permanganate index: 0-20 mg / L, turbidity: 0-1000 NTU, ammonia nitrogen: 0-10 mg / L, suspended solids concentration: 0-300 mg / L, CDOM absorption coefficient: 0-30 m -1 , extinction coefficient C550: 0~100m -1 etc. may also be used.

[0146] Application Scenario 7: Application scenario of drone hyperspectral remote sensing

[0147] As shown in Figure 6B, based on application scenario 3, the spectral reflectance measurement system is applied to drone hyperspectral remote sensing. When the drone is under sunlight, sunlight hits the light uniformization material and the target area simultaneously with the same solar irradiance. The sunlight passes through the light uniformization path and is received by the optical fiber spectrometer as the ambient light spectrum. It is then mapped using the ambient light mapping relationship model (i.e., mapping parameters) to obtain the reference spectrum for calculating the spectral reflectance. The optical signal diffusely reflected by the target is received by the lens and then received by the hyperspectral camera (i.e., imaging spectrometer) as the target spectrum for calculating the spectral reflectance. Because it is a hyperspectral camera, the acquired target spectrum is a linear array target spectrum or an area array target spectrum. The industrial control board combines the linear array target spectrum or the area array target spectrum with the acquired reference spectrum to calculate the linear array spectral reflectance or the area array spectral reflectance.

[0148] The spectral reflectance measurement system is applied to drone hyperspectral remote sensing, enabling real-time and stable acquisition of reference spectra, ensuring that the final acquired spectral reflectance cube is not affected by changes in solar irradiance. The mapping relationship calibration process is similar to the above embodiment: a whiteboard is placed within the field of view of the hyperspectral camera, the hyperspectral camera captures one frame of hyperspectral image including the whiteboard, and the ambient light sensing module 11 captures one frame of current ambient light multispectral data. In the preprocessing stage, hyperspectral data of the whiteboard area is extracted from the captured frame of hyperspectral image, and then an ambient light mapping relationship model is constructed to achieve mapping parameter calibration.

[0149] Application Scenario 8: Application scenario of drone hyperspectral remote sensing

[0150] As shown in Figure 6C, based on application scenario 4, the spectral reflectance measurement system is applied to hyperspectral remote sensing of a drone. Figure 6C is a specific embodiment of Figure 6B. When the drone's attitude is tilted, an attitude sensor (e.g., a gyro sensor) senses the drone's attitude and acquires the attitude angle. Based on the acquired attitude angle, the attitude angle information is added to the ambient light mapping model, allowing for an accurate reference spectrum to be acquired and eliminating tilt bias in the calculation of spectral reflectance.

[0151] As can be seen from the above technical solutions, in the embodiments of the present invention, by pre-calibrating the mapping parameters between the reference spectrum and the ambient light spectrum, the spectral reflectance of the object under measurement can be accurately calculated, thereby realizing rapid, real-time, efficient, and accurate acquisition of the spectral reflectance of the object under measurement. The spectral reflectance of the object under measurement can be continuously acquired in situ in real time, improving the convenience and real-timeness of acquiring the spectral reflectance of on-site features (i.e., the object under measurement). During use, a calibration object (e.g., a standard whiteboard) can be used for a single calibration (i.e., calibration mapping parameters), eliminating the need to repeatedly collect data from the calibration object. This allows acquisition of spectral reflectance under different weather conditions and different solar elevation angles, and improves the accuracy of spectral reflectance calculation in various use cases through solar elevation angle / attitude angle correction, etc. The ambient light sensing module and the calibrated ambient light mapping relationship (i.e., mapping parameters) allow efficient and simple acquisition of the reference spectrum of the object under solar radiation. Specifically, by using an ambient light sensing module and a target spectrum collection module, a single calibration can be performed at a single time to obtain reference spectra under different weather conditions and different solar altitude angles, allowing for automatic real-time calculation of spectral reflectance. Furthermore, solar altitude angle / attitude angle correction can be used to improve the accuracy of spectral reflectance calculations for various use cases. The ambient light sensing module is composed of a light homogenization path and a spectral sensor, and has a cosine response characteristic. The photocurrent output of the spectral sensor follows a cosine response. That is, the photocurrent generated at different incident angles is equal to the photocurrent at normal incidence multiplied by the cosine of the incident angle. This eliminates the phenomenon of light being blocked or attenuated at large angles, allowing for the acquisition of solar radiation spectra for a target area at different times and under different solar altitude angles. Spectral reflectance calculations can be achieved using only a single target spectrum collection module and ambient light sensing module, and angle correction using a gyro sensor to acquire attitude angles allows for compatibility with various installation environments.

[0152] Based on the same application concept as the above-described spectral reflectance measurement system, an embodiment of the present invention proposes a spectral reflectance measurement method that can be applied to the spectral reflectance measurement system. FIG. 7 is a schematic diagram showing the flow of the spectral reflectance measurement method, which may include the following steps:

[0153] Step 701: Determine a measurement ambient light spectrum and a measurement target spectrum corresponding to the same target wavelength. The measurement ambient light spectrum is collected at the same time as the measurement target spectrum, and the measurement ambient light spectrum is the spectrum of the first ambient light, while the measurement target spectrum is the spectrum of the second ambient light reflected by the object under test.

[0154] For example, the measured ambient light spectrum includes a measured ambient light spectrum for each wavelength in a first wavelength set, and the measured target spectrum includes a measured target spectrum for each wavelength in a second wavelength set, where the first wavelength set is a subset of the second wavelength set. The step of determining the measured ambient light spectrum and the measured target spectrum corresponding to the same target wavelength may include, but is not limited to, the steps of: determining whether the target wavelength is present in the first wavelength set, and if present, directly obtaining the measured ambient light spectrum corresponding to the target wavelength; and, if not present, determining the measured ambient light spectrum corresponding to the target wavelength based on the measured ambient light spectra of at least two wavelengths. For example, the step of selecting a first matching wavelength and a second matching wavelength from the first wavelength set and determining the measured ambient light spectrum corresponding to the target wavelength based on the measured ambient light spectrum corresponding to the first matching wavelength and the measured ambient light spectrum corresponding to the second matching wavelength. The first matching wavelength is the wavelength in the first wavelength set that is closest to and smaller than the target wavelength, and the second matching wavelength is the wavelength in the first wavelength set that is closest to and larger than the target wavelength.

[0155] In one possible embodiment, a maximum spectral value in the measurement ambient light spectrum and the measurement target spectrum may be determined, and if the maximum spectral value is less than a predetermined minimum spectral value, a currently used first exposure time is adjusted to a second exposure time, and the measurement ambient light spectrum is acquired based on the second exposure time, and the measurement target spectrum is acquired based on the second exposure time, the second exposure time being greater than the first exposure time.

[0156] If the maximum spectral value is greater than a predetermined spectral maximum value, the currently used first exposure time is adjusted to a third exposure time, a measurement ambient light spectrum is collected based on the third exposure time, and a measurement target spectrum is collected based on the third exposure time, the third exposure time being less than the first exposure time.

[0157] Step 702: Determine a measurement reference spectrum based on the measured ambient light spectrum and the determined mapping parameters, where the measurement reference spectrum is a spectrum of a second ambient light, and the mapping parameters represent a mapping relationship between the reference spectrum and the ambient light spectrum, and the mapping parameters are determined and stored in a mapping parameter calibration process.

[0158] In one possible embodiment, position data may be collected, an angular parameter may be determined based on the position data, and a measurement reference spectrum may be determined based on the measured ambient light spectrum, the angular parameter, and the mapping parameter, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angular parameter. Exemplarily, if the position data is attitude information of a spectral reflectance measurement system, the angular parameter may be an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of a spectral reflectance measurement system, the angular parameter may be a zenith angle, e.g., a solar zenith angle, corresponding to the longitude and latitude information.

[0159] Step 703: Determine the spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum.

[0160] In one possible embodiment, the process of determining the mapping parameters (i.e., the calibration process) may include, but is not limited to, the steps of: determining a calibration ambient light spectrum and a calibration target spectrum corresponding to the same target wavelength, wherein the time of collection of the calibration ambient light spectrum may be the same as the time of collection of the calibration target spectrum, the calibration ambient light spectrum may be the spectrum of a first ambient light, and the calibration target spectrum may be a spectrum of a calibration object reflecting a second ambient light; determining a calibration reference spectrum based on the calibration target spectrum and a set spectral reflectance of the calibration object, wherein the calibration reference spectrum may be the spectrum of the second ambient light; and determining the mapping parameters based on the calibration reference spectrum and the calibration ambient light spectrum.

[0161] For example, the calibration ambient light spectrum includes a calibration ambient light spectrum for each wavelength in a first wavelength set, and the calibration target spectrum includes a calibration target spectrum for each wavelength in a second wavelength set, the first wavelength set being a subset of the second wavelength set. The step of determining the calibration ambient light spectrum and the calibration target spectrum corresponding to the same target wavelength may include, but is not limited to, the steps of: selecting each wavelength in the second wavelength set as a target wavelength and, for each target wavelength, obtaining a calibration target spectrum corresponding to the target wavelength; determining whether the target wavelength is present in the first wavelength set; and, if present, directly obtaining a calibration ambient light spectrum corresponding to the target wavelength; and, if not present, determining the calibration ambient light spectrum corresponding to the target wavelength based on the calibration ambient light spectra of at least two wavelengths. For example, the step of selecting a first matching wavelength and a second matching wavelength from the first wavelength set and determining the calibration ambient light spectrum corresponding to the target wavelength based on the calibration ambient light spectrum corresponding to the first matching wavelength and the calibration ambient light spectrum corresponding to the second matching wavelength. The first matching wavelength is the wavelength in the first wavelength set that is closest to and smaller than the target wavelength, and the second matching wavelength is the wavelength in the first wavelength set that is closest to and larger than the target wavelength.

[0162] In one possible embodiment, a maximum spectral value in the calibration ambient light spectrum and the calibration target spectrum may be determined, and if the maximum spectral value is less than a predetermined minimum spectral value, a currently used first exposure time is adjusted to a second exposure time, and a calibration ambient light spectrum is acquired based on the second exposure time, and a calibration target spectrum is acquired based on the second exposure time, the second exposure time being greater than the first exposure time.

[0163] If the maximum spectral value is greater than a predetermined spectral maximum value, the currently used first exposure time is adjusted to a third exposure time, a calibration ambient light spectrum is collected based on the third exposure time, and a calibration target spectrum is collected based on the third exposure time, the third exposure time being less than the first exposure time.

[0164] In one possible embodiment, for the process of determining the mapping parameter, position data may be collected, an angular parameter may be determined based on the position data, and the mapping parameter may be determined based on the angular parameter, the calibration reference spectrum, and the calibration ambient light spectrum, where the mapping parameter represents a mapping relationship between the reference spectrum, the ambient light spectrum, and the angular parameter. If the position data is attitude information of a spectral reflectance measurement system, the angular parameter is an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of a spectral reflectance measurement system, the angular parameter is a zenith angle corresponding to the longitude and latitude information.

[0165] For ease of explanation, the above apparatus is described separately with various functional units. Of course, when implementing the present invention, the functions of the various units can be realized by the same or multiple pieces of software and / or hardware.

[0166] As will be appreciated by those skilled in the art, embodiments of the present invention may be provided as a method, a system, or a computer program product. Accordingly, the present invention may employ embodiments consisting entirely of hardware, entirely of software, or a combination of software and hardware. Furthermore, embodiments of the present invention may take the form of a computer program product embodied in one or more computer-usable storage media (including, but not limited to, magnetic disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.

[0167] The present invention will be described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, whereby the instructions, executed by the processor of the computer or other programmable data processing device, generate an apparatus for implementing the functions specified in one or more flows in the flowcharts and / or one or more blocks in the block diagrams.

[0168] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture that includes an instruction apparatus that implements the functions specified in one or more flows of the flowcharts and / or one or more blocks of the block diagrams.

[0169] These computer program instructions may be loaded into a computer or other programmable data processing device, whereby a series of operational steps are executed on the computer or other programmable device to generate a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more flows of the flowcharts and / or one or more blocks of the block diagrams.

[0170] The above is merely an example of the present invention and is not intended to limit the present invention. Various modifications and variations are possible for those skilled in the art to make to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are intended to be included in the scope of the claims of the present invention. [Explanation of symbols]

[0171] 1. Light homogenization path 2 Multispectral sensor 3 Position Sensor 4 lenses 5. Fiber optic spectrometer 11 Ambient Light Sensing Module 11 Ambient Light Sensing Module 12 Target Spectrum Acquisition Module 13 Data Processing Module

Claims

1. 1. A spectral reflectance measurement system including an ambient light sensing module, a target spectrum acquisition module, and a data processing module, the ambient light sensing module is used to collect a measured ambient light spectrum at a target measurement time and send the measured ambient light spectrum to the data processing module, the measured ambient light spectrum being a spectrum of a first ambient light, the first ambient light being the ambient light sensed by the ambient light sensing module; the target spectrum collection module is used to collect a measurement target spectrum at a target measurement time and transmit the measurement target spectrum to the data processing module, the measurement target spectrum being a spectrum of second ambient light reflected by an object to be measured, the second ambient light being ambient light sensed by the target spectrum collection module; the data processing module determines a measurement environment light spectrum and a measurement target spectrum corresponding to the same target wavelength, determines a measurement reference spectrum based on the measurement environment light spectrum and the determined mapping parameter, and determines a spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum, the measurement reference spectrum being the spectrum of the second ambient light, and the mapping parameter representing a mapping relationship between the measurement reference spectrum and the measurement environment light spectrum; the ambient light sensing module is further adapted to collect a calibration ambient light spectrum at a target calibration time and send the calibration ambient light spectrum to the data processing module, the calibration ambient light spectrum being a spectrum of a first ambient light, the first ambient light being the ambient light sensed by the ambient light sensing module; the target spectrum collection module is further used to collect a calibration target spectrum at a target calibration time and transmit the calibration target spectrum to the data processing module, the calibration target spectrum being a spectrum of a calibration object reflecting second ambient light, the second ambient light being ambient light sensed by the target spectrum collection module; the data processing module is further used to determine a calibration ambient light spectrum and a calibration target spectrum corresponding to the same target wavelength, determine a calibration reference spectrum based on the calibration target spectrum and a set spectral reflectance of the calibration object, and determine the mapping parameters based on the calibration reference spectrum and the calibration ambient light spectrum, wherein the calibration reference spectrum is the spectrum of the second ambient light.

2. the ambient light sensing module is used to collect measured ambient light spectral values ​​for each wavelength in a first set of wavelengths, and the target spectral collection module is used to collect measured target spectral values ​​for each wavelength in a second set of wavelengths, the first set of wavelengths being a subset of the second set of wavelengths; Specifically, when the data processing module determines the measurement environment light spectrum and the measurement target spectrum corresponding to the same target wavelength, Each wavelength in the second wavelength set is a target wavelength, and for each target wavelength: collecting measured target spectrum values ​​corresponding to the target wavelengths from the target spectrum collection module; 2. The spectral reflectance measurement system of claim 1, wherein the system is used to determine whether the target wavelength is present in the first wavelength set, and if present, obtain a measured ambient light spectral value corresponding to the target wavelength from the ambient light sensing module, and if not present, determine a measured ambient light spectral value corresponding to the target wavelength based on the measured ambient light spectral values ​​of at least two wavelengths collected by the ambient light sensing module.

3. Specifically, when the data processing module determines the measured ambient light spectrum value corresponding to the target wavelength based on the measured ambient light spectrum values ​​of at least two wavelengths collected by the ambient light sensing module, selecting a first matching wavelength and a second matching wavelength from the first set of wavelengths; used to determine a measured ambient light spectral value corresponding to the target wavelength based on a measured ambient light spectral value corresponding to the first matching wavelength and a measured ambient light spectral value corresponding to the second matching wavelength; 3. The spectral reflectance measurement system of claim 2, wherein the first matching wavelength is a wavelength in the first wavelength set that is shorter than the target wavelength and is closest to the target wavelength, and the second matching wavelength is a wavelength in the first wavelength set that is greater than the target wavelength and is closest to the target wavelength.

4. the data processing module determines a maximum spectral value in the measured ambient light spectrum and the measured target spectrum; If the maximum spectral value is smaller than a predetermined minimum spectral value, adjust the first exposure time currently used by the ambient light sensing module to a second exposure time, control the ambient light sensing module to collect a measured ambient light spectrum based on the second exposure time, and control the target spectrum collecting module to collect a measured target spectrum based on the second exposure time; If the maximum spectral value is greater than a predetermined spectral maximum value, the first exposure time currently used by the ambient light sensing module is adjusted to a third exposure time, the ambient light sensing module is controlled to collect a measured ambient light spectrum based on the third exposure time, and the target spectrum collecting module is controlled to collect a measured target spectrum based on the third exposure time.

2. The spectral reflectance measurement system according to claim 1, wherein the second exposure time is longer than the first exposure time, and the third exposure time is shorter than the first exposure time.

5. the ambient light sensing module is used to collect location data and transmit the location data to the data processing module; When the data processing module determines a measurement reference spectrum based on the measured environment light spectrum and the determined mapping parameter, the data processing module specifically determines an angle parameter based on the position data, and determines the measurement reference spectrum based on the measured environment light spectrum, the angle parameter, and the mapping parameter, the mapping parameter representing a mapping relationship between the measurement reference spectrum, the measured environment light spectrum, and the angle parameter; 2. The spectral reflectance measurement system of claim 1, wherein if the position data is attitude information of the ambient light sensing module, the angle parameter is an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of the ambient light sensing module, the angle parameter is a zenith angle corresponding to the longitude and latitude information.

6. the ambient light sensing module is used to collect location data and transmit the location data to the data processing module; When the data processing module determines the mapping parameter based on the calibration reference spectrum and the calibration environment light spectrum, the data processing module specifically determines an angle parameter based on the position data, and determines the mapping parameter based on the angle parameter, the calibration reference spectrum, and the calibration environment light spectrum, wherein the mapping parameter represents a mapping relationship between the measurement reference spectrum, the measurement environment light spectrum, and the angle parameter; 2. The spectral reflectance measurement system of claim 1, wherein if the position data is attitude information of the ambient light sensing module, the angle parameter is an attitude angle corresponding to the attitude information, and / or if the position data is longitude and latitude information of the ambient light sensing module, the angle parameter is a zenith angle corresponding to the longitude and latitude information.

7. the ambient light sensing module includes at least a light uniformization path and a multispectral sensor, the light uniformization path is disposed opposite to the multispectral sensor, the ambient light is uniformized by the light uniformization path and then transmitted to the multispectral sensor, and the multispectral sensor collects the measured ambient light spectrum of a plurality of wavelengths; Alternatively, the ambient light sensing module includes at least a light homogenizing path, an optical fiber, and an optical fiber spectrometer, one end of the optical fiber is connected to the optical fiber spectrometer, and the other end of the optical fiber is connected to the light homogenizing path, the ambient light is homogenized by the light homogenizing path and then transmitted to the optical fiber spectrometer through the optical fiber, and the optical fiber spectrometer collects the measured ambient light spectrum of multiple wavelengths; The spectral reflectance measurement system according to any one of claims 1 to 5, characterized in that the ambient light sensing module further comprises an attitude sensor and / or a position sensor, the attitude sensor being used to collect attitude information, and the position sensor being used to collect longitude and latitude information.

8. the target spectrum collection module includes a lens and an optical fiber spectrometer, the lens is connected to the optical fiber spectrometer, the lens collects light after the object to be measured has reflected the ambient light and transmits it to the optical fiber spectrometer, and the optical fiber spectrometer collects the measurement target spectrum of multiple wavelengths; Alternatively, the target spectrum collection module may include a lens and an imaging spectrometer, the lens being connected to the imaging spectrometer, and the lens collecting light after the object to be measured has reflected ambient light and transmitting the light to the imaging spectrometer, and the imaging spectrometer collecting the measurement target spectrum at a plurality of wavelengths.

9. determining a measurement ambient light spectrum and a measurement target spectrum corresponding to the same target wavelength, wherein a time of collection of the measurement ambient light spectrum is the same as a time of collection of the measurement target spectrum, the measurement ambient light spectrum is a spectrum of a first ambient light, and the measurement target spectrum is a spectrum of a second ambient light reflected by an object under test; determining a measurement reference spectrum based on the measured ambient light spectrum and the determined mapping parameter, wherein the measurement reference spectrum is the spectrum of the second ambient light, and the mapping parameter represents a mapping relationship between the measurement reference spectrum and the measured ambient light spectrum; determining a spectral reflectance of the object to be measured based on the measurement target spectrum and the measurement reference spectrum; Including, The process of determining the mapping parameters comprises: Determining a calibration ambient light spectrum and a calibration target spectrum corresponding to the same target wavelength a step of: acquiring the calibration ambient light spectrum at a time corresponding to the time of the calibration target spectrum; The calibration ambient light spectrum is the spectrum of the first ambient light. wherein the calibration target spectrum is a spectrum of the second ambient light reflected by a calibration object. Steps and A calibration target spectrum is calculated based on the set spectral reflectance of the calibration object. determining a reference spectrum, said calibration reference spectrum being a spectrum of said second circle; The spectrum of the surrounding light is a step, The mapping pattern is calculated based on the calibration reference spectrum and the calibration ambient light spectrum. determining a parameter; A spectral reflectance measuring method comprising:

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