Plant sensor device and active plant optical measurement method

Abstract

Provided is a plant sensor device with which it is possible to obtain a parameter relating to the leaf quantity of a plant by means of a simple and low-cost configuration while suppressing the influence of external light of the surrounding environment in order to quantify the growth degree of the plant. A plant sensor device (100) or an active optical measurement method for a plant, comprising: a light source (11) that intermittently irradiates a plant with near-infrared light (NIR); a radiation sensor (21) that is disposed on the opposite side from the light source (11) with respect to the plant, receives transmitted light of the near-infrared light that has passed through the plant, and outputs an output value obtained by photoelectrically converting the transmitted light; and a recording unit (31) that records an output value from the radiation sensor (21), the recording unit (31) records an irradiation period and an extinction period of the near-infrared light from the light source (11), and the recording unit (31) classifies the output value from the radiation sensor as: (1) an NIR output value of the irradiation period of the near-infrared light; and (2) a non-irradiation output value during the extinction period of the near-infrared light.

Description

Technical Field

[0001] The present invention relates to a plant sensor device and a method for active optical measurement of plants. Background Art

[0002] In recent years, with the development of data-related technologies, there is a demand to quantify the growth of plants. As indicators of plant growth, the leaf area index (LAI) and photosynthetically active radiation absorption rate (fAPAR) are known. For example, the leaf area index refers to an index value that represents the sum of the single-sided areas of all leaves of the vegetation above per unit horizontal area. For example, if 1m 2 The total area of ​​leaves on the ground is 2m 2 , then LAI = 2, which means that two leaves overlap when the leaves are arranged on the ground without gaps. The leaf area index of ordinary forest vegetation is around 3 to 7. The leaf area index is an important parameter for evaluating vegetation functions. As an important indicator of the absorption of photosynthetically active radiation, photosynthetic capacity, transpiration, and carbon absorption capacity of vegetation, it is widely used in agriculture, forest science, ecology, earth environment science, etc.

[0003] As a method for obtaining the leaf area index, Patent Document 1 describes an optical vegetation index sensor comprising: a first radiation sensor which, when receiving transmission radiation transmitted through a leaf or a group of leaves, corrects the spectral characteristics of radiation in the visible radiation region of 400 nm to 700 nm for measurement as a photon beam density using a correction filter, and outputs a PAR output representing either photosynthetically active radiance or photosynthetic photon beam density by photoelectrically converting the corrected radiation by a light receiving unit; a second radiation sensor which, with respect to the received radiation, extracts only radiation in the infrared radiation region of 700 nm to 1000 nm using a bandpass filter, and outputs an IR output representing either radiance or photon beam density in a unit common to the PAR output by photoelectrically converting the radiation by a light receiving unit; and a calculation unit which accumulates the PAR output and the IR output over time, divides the accumulated value of the IR output by the accumulated value of the PAR output to calculate a ratio, and obtains the leaf area index corresponding to the ratio.

[0004] In addition, the optical vegetation index sensor of Patent Document 1 applies the well-known correlation relationship between the spectral intensity ratio Y (=800 / 675) of red radiation (wavelength of 675nm) and near-infrared radiation (wavelength of 800nm) after passing through vegetation and the leaf area index X, logY=0.3813+0.0989X, which can be said to be the "transmission NIR / PAR method".

[0005] In addition, Patent Document 1 describes other methods for calculating the leaf area index: the "Fisheye Lens Method", which uses a full fisheye lens and an electronic imaging element to capture images of a specified area for near-infrared radiation and red radiation, respectively, and calculate their brightness value ratios to infer relative solar radiation; and the "Plant Canopy Analyzer" (LAI-2000, etc.) of LI-COR Corporation of the United States, which optically divides the entire sky into five parts in a ring shape and measures the intensity distribution of blue radiation in the entire sky.

[0006] On the other hand, other methods of optically obtaining the growth status are known, not limited to the leaf area index, and are divided into a method using transmitted light as in Patent Document 1, a method using scattered light (Patent Document 2), and a method using reflected light (Patent Document 3).

[0007] Patent document 2 describes a plant community transmitted light sensor unit, which has a visible light sensor for detecting visible light and a near-infrared light sensor for detecting near-infrared light, and is used to determine the growth status of plants. The plant community transmitted light sensor unit includes a transparent tube and a pair of black cover plates that close both ends of the tube. When the tube is erected in a vertical direction, the visible light sensor and the near-infrared light sensor are respectively installed on the lower surface of the upper cover plate and the inner center of the tube with the light receiving surface facing downward.

[0008] Patent document 3 describes a sensor device for plants, comprising: a first light emitting section that emits a first measuring light of a first wavelength to illuminate a growth condition measurement object; a second light emitting section that emits a second measuring light of a second wavelength to illuminate the growth condition measurement object; a light receiving section that receives reflected light of each measuring light from the growth condition measurement object and outputs a light receiving signal; a control section that controls light emission from the first light emitting section and emission from the second light emitting section at different times; an optical path merging unit that merges a first emission optical path of the first measuring light from the first light emitting section and a second emission optical path of the second measuring light from the second light emitting section; and a common emission section that connects the optical path merging unit to an emission section that emits the first measuring light and the second measuring light toward the growth condition measurement object, the emission section having an optical component that has a refractive power in only one direction when observed on a plane perpendicular to the emission optical axis, and the optical component is held so as to be rotatable around the emission optical axis.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2011-133451

[0012] Patent Document 2: Japanese Patent Application Publication No. 2020-198804

[0013] Patent Document 3: Japanese Patent No. 5718153 Summary of the invention

[0014] Problems to be solved by the invention

[0015] However, the optical vegetation index sensor described in Patent Document 1 has a total of two expensive radiation sensors including filters, so further cost reduction is required. The accuracy of the transmission NIR / PAR method depends on the spectral stability of the incident sunlight (solar radiation), but there is a problem that the NIR / PAR of the incident solar radiation varies by more than 10% depending on the conditions of the sky. In addition, in the case of light sources other than sunlight, the NIR / PAR of the incident light varies greatly, which is affected by the surrounding environment in the greenhouse, and it is difficult to use it in an artificial light environment.

[0016] Regarding other methods described in Patent Document 1, the fisheye lens method has the problem of not being able to use images on sunny days. The vegetation canopy analyzer of LI-COR needs to perform measurements both outside and inside the forest on cloudy days, so it cannot be used in environments with large changes in solar radiation or artificial light environments.

[0017] The device described in Patent Document 2 also has a total of two expensive visible light sensors and near infrared light sensors. In addition, in order to detect scattered light, upper and lower black cover plates are required. In the case of a horizontal type, a second cover plate is also required, and the device structure is complicated. In addition, Patent Document 2 records that the data of cloudy and rainy days are cancelled in order to eliminate the influence of solar radiation changes, and there is a problem that it is affected by the external light of the surrounding environment. Therefore, further cost reduction and high precision are required.

[0018] In the device for detecting reflected light using an irradiation sensor (light receiving unit) of Patent Document 3, in order to remove the influence of disturbance light by calculation, two types of measurement lights having different wavelengths are detected by light receiving units formed of 2 to 6 photodiodes. Furthermore, in order to detect reflected light from the two types of measurement lights, the light source (emitting unit) needs to be maintained as an optical component (lens) having a refractive power that can rotate around the optical axis, etc., and the device structure is complicated. Therefore, further cost reduction is required.

[0019] An object of the present invention is to provide a plant sensor device capable of obtaining a parameter related to the leaf amount of a plant with a simple and low-cost configuration while suppressing the influence of external light in the surrounding environment in order to quantify the growth degree of the plant.

[0020] Means for solving problems

[0021] In the present invention, (1) near-infrared light is actively and intermittently irradiated from a light source, and the output values ​​of the near-infrared light from the radiation sensor during the irradiation period and the extinction period are classified and recorded, or (2) near-infrared light is actively irradiated from a light source with two or more levels of intensity, and the output values ​​of the near-infrared light from the radiation sensor during the irradiation period of the first luminous intensity and the irradiation period of the second luminous intensity are classified and recorded, thereby solving the above-mentioned problems.

[0022] The configuration of the present invention and preferred configurations of the present invention are described below as specific means for solving the above-mentioned problems.

[0023] [1] A plant sensor device comprising: a light source that intermittently irradiates near-infrared light (NIR) toward a plant; a radiation sensor that is arranged on the opposite side of the plant to the light source, receives the transmitted light of the near-infrared light after passing through the plant and outputs an output value after photoelectric conversion of the transmitted light; and a recording unit that records the output value from the radiation sensor, the recording unit recording the irradiation period and extinction period of the near-infrared light of the light source, and the recording unit classifies the output value from the radiation sensor into: (1) NIR output value during the irradiation period of the near-infrared light; and (2) non-irradiation output value during the extinction period of the near-infrared light.

[0024] [2] The plant sensor device according to [1], wherein the plant sensor device has a calculation unit that calculates a difference A calculated by (NIR output value)-(non-irradiation output value) and converts the difference A into a leaf area index.

[0025] [3] The plant sensor device according to [2], wherein the leaf area index is a linear function of a logarithmic function with the difference A or a function thereof as a true number.

[0026] [4] A plant sensor device according to [2] or [3], wherein the plant sensor device has a growth unit that controls at least one of fertilizer, water, temperature and humidity so as to inhibit the growth of plant leaves when the leaf area index exceeds a specified range, or promote the growth of plant leaves when the leaf area index is below a specified range.

[0027] [5] The plant sensor device according to any one of [1] to [4], wherein the plant is a leaf group or a plant colony.

[0028] [6] The plant sensor device according to any one of [1] to [5], wherein the light source comprises only a near-infrared light source.

[0029] [7] The plant sensor device according to [6], wherein the near-infrared light source irradiates near-infrared light of a narrow band having a peak wavelength of 750 nm to 1100 nm and a half-value width of 50 nm or less.

[0030] [8] A plant sensor device according to any one of [1] to [7], wherein the radiation sensor has a bandpass filter that filters out light with a wavelength band less than 750nm, and only extracts radiation of near-infrared light with a wavelength band above 750nm.

[0031] [9] A plant sensor device according to any one of [1] to [8], wherein the plant sensor device has a radiation sensor fixing portion for fixing the radiation sensor, and the radiation sensor fixing portion fixes the radiation sensor at a position lower than the measuring portion with the light receiving surface facing the measuring portion of the plant.

[0032]

[10] A plant sensor device according to any one of [1] to [9], wherein the plant sensor device has a light source fixing unit for fixing the light source, and the light source fixing unit fixes the light source at a position above the measuring part of the plant.

[0033]

[11] A plant sensor device according to any one of [1] to

[10] , wherein the plant sensor device comprises: a radiation sensor fixing part, which fixes the radiation sensor; a light source fixing part, which fixes the light source; and a connecting part, which connects the radiation sensor fixing part and the light source fixing part, and the distance from the light source to the light receiving surface of the radiation sensor is 1 cm to 1000 cm.

[0034]

[12] The plant sensor device according to

[11] , wherein the connecting member has a gripping portion.

[0035]

[13] A plant sensor device according to any one of [1] to

[12] , wherein the plant sensor device comprises: a radiation sensor fixing unit, which fixes the radiation sensor; and a light source fixing unit, which fixes the light source, the light source fixing unit fixes the light source at a position below the measuring part of the plant, and the radiation sensor fixing unit fixes the radiation sensor at a position above the measuring part with the light receiving surface facing the measuring part of the plant.

[0036]

[14] A plant sensor device according to any one of [1] to

[13] , wherein the output value from the beginning to the end of the illumination period and the extinction period is set to 100%, and the output value of the intermediate period of 25% to 75% is used as the NIR output value and the non-irradiation output value.

[0037]

[15] The plant sensor device according to any one of [1] to

[14] , wherein the illumination period and the extinction period are both from 1 millisecond to 1 minute.

[0038]

[16] A plant sensor device according to any one of [1] to

[15] , wherein the plant sensor device further comprises a control unit that controls the illumination period and extinction period of the light source to be approximately equally spaced within ±30% of each other.

[0039]

[17] A plant sensor device comprising: a light source for irradiating near-infrared light (NIR) to a plant; a radiation sensor arranged on the opposite side of the plant from the light source, receiving the transmitted near-infrared light after passing through the plant and outputting an output value after photoelectric conversion of the transmitted light; a recording unit for recording the output value from the radiation sensor; and a control unit, the control unit controlling the light source to irradiate infrared light with a first luminous intensity and a second luminous intensity, wherein the second luminous intensity is 1 / n times (n is a positive number) the first luminous intensity, and the recording unit classifies (1) the NIR output value during the irradiation period of the near-infrared light in the output value from the radiation sensor into: (1-1) the first NIR output value during the irradiation period of the near-infrared light with the first luminous intensity; and (1-2) the second NIR output value during the irradiation period of the near-infrared light with the second luminous intensity.

[0040]

[18] The plant sensor device according to

[17] , wherein the plant sensor device has a calculation unit that converts the difference B calculated by (first NIR output value)-(second NIR output value) into a leaf area index.

[0041]

[19] An active optical measurement method for plants, using the plant sensor device described in any one of [1] to

[18] .

[0042]

[20] The active optical measurement method of plants according to

[19] , wherein the active optical measurement method of plants is used for ground truth from remote sensing of the sky or the universe, plant growth measurement in plant growth facilities, vegetation measurement in forests, and leaf mass measurement in plant communities or leaf groups.

[0043] Effects of the Invention

[0044] According to the present invention, it is possible to provide a plant sensor device capable of obtaining a parameter related to the leaf amount of a plant with a simple and low-cost configuration while suppressing the influence of external light in the surrounding environment in order to quantify the growth degree of the plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram showing a cross section of an example of the plant sensor device of the present invention.

[0046] Figure 2 It is a schematic diagram showing a cross section of another example of the plant sensor device of the present invention.

[0047] Figure 3 It is a schematic diagram showing a cross section of another example of the plant sensor device of the present invention.

[0048] Figure 4 It is the spectrum of sunlight and LED light source (peak wavelength is 850nm).

[0049] Figure 5 This is a graph showing the relationship between the time from the start of measurement and the photon flux density (output value) in Example 1.

[0050] Figure 6 (A) is a photograph of the leaves of the plant to be measured in Example 2 and the radiation sensor used. Figure 6 (B) is a photograph of the structure of the plant sensor device of Example 2.

[0051] Figure 7 It is a graph showing the relationship between the leaf area index and the transmittance at 850 nm in indoor and outdoor measurements.

[0052] Figure 8 This is a graph showing the relationship between the time from the start of measurement and the photon flux density (output value) in Example 3. DETAILED DESCRIPTION

[0053] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below is sometimes based on representative embodiments and specific examples, and the present invention is not limited to such embodiments. In addition, in this specification, the numerical range represented by "to" refers to the range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0054] [Plant sensor device]

[0055] The first mode of the plant sensor device of the present invention comprises: a light source, which intermittently irradiates near-infrared light (NIR) to a plant; a radiation sensor, which is arranged on the opposite side of the plant to the light source, receives the transmitted light of the near-infrared light after passing through the plant and outputs an output value after photoelectric conversion of the transmitted light; and a recording unit, which records the output value from the radiation sensor, the recording unit records the irradiation period and extinction period of the near-infrared light of the light source, and the recording unit classifies the output value from the radiation sensor into: (1) NIR output value during the irradiation period of the near-infrared light; (2) non-irradiation output value during the extinction period of the near-infrared light.

[0056] A second embodiment of the plant sensor device of the present invention comprises: a light source that irradiates near-infrared light (NIR) to a plant; a radiation sensor that is arranged on the opposite side of the light source relative to the plant, receives the transmitted light of the near-infrared light after passing through the plant and outputs an output value after photoelectric conversion of the transmitted light; a recording unit that records the output value from the radiation sensor; and a control unit, the control unit controls the light source to irradiate infrared light with a first luminous intensity and a second luminous intensity, the second luminous intensity being 1 / n times (n is a positive number) the first luminous intensity, and the recording unit classifies (1) the NIR output value during the irradiation period of the near-infrared light in the output value from the radiation sensor into: (1-1) the first NIR output value during the irradiation period of the near-infrared light with the first luminous intensity; (1-2) the second NIR output value during the irradiation period of the near-infrared light with the second luminous intensity.

[0057] With these configurations, in order to quantify the growth degree of the plant, the influence of external light in the surrounding environment can be suppressed, and the parameter related to the leaf amount of the plant can be obtained with a simple and low-cost configuration.

[0058] In this specification, the "leaf mass" of a plant includes not only growth levels such as LAI, luxuriance, and aboveground biomass, but also physiological functions such as chlorophyll content, photosynthetic activity, aging, and stress response of the leaves.

[0059] The preferred embodiment of the present invention is described below. The preferred embodiment of the first embodiment of the plant sensor device of the present invention is mainly described below, but the preferred embodiment of the first embodiment of the plant sensor device of the present invention is also the preferred embodiment of the second embodiment of the present invention. Furthermore, the preferred embodiment of the second embodiment of the plant sensor device of the present invention is also the preferred embodiment of the first embodiment of the present invention.

[0060] <Overview of Plant Sensor Device>

[0061] First, the outline of the plant sensor device of the present invention will be described with reference to the drawings. However, the present invention is not to be construed as being limited to the drawings.

[0062] Figure 1 Schematic diagram showing a cross section of an example of a plant sensor device of the present invention. Figure 1 The plant sensor device 100 shown comprises: a light source 11, which intermittently irradiates near-infrared light 12 to a plant 1 (a colony, specifically a leaf group); a radiation sensor 21, which is arranged on the opposite side of the light source 11 relative to the plant 1, receives transmitted light 13 of the near-infrared light after passing through the plant 1, and outputs an output value after photoelectric conversion of the transmitted light 13; and a recording unit 31, which records the output value from the radiation sensor 21.

[0063] exist Figure 1In the plant sensor device shown, the recording unit 31 records the irradiation period and extinction period of the near-infrared light of the light source 11, and the recording unit 31 classifies the output value from the radiation sensor into: (1) NIR output value during the irradiation period of near-infrared light; (2) non-irradiation output value during the extinction period of near-infrared light.

[0064] Figure 1 The plant sensor device shown has a computer 30 that includes a recording unit 31, a calculation unit 32 and a control unit 33, which can be arbitrarily provided. The calculation unit 32 and the control unit 33 can be part of a CPU 34.

[0065] Furthermore, the computer 30 is connected to a display unit 35 which can be arbitrarily provided, and can display arbitrary calculation results, etc. Furthermore, the computer 30 may also be connected to an output unit 36 ​​directed to the outside, and can output data to another PC, a printer, etc.

[0066] In addition, the computer 30 may also have an input unit (not shown). Any program or the like may be stored in the recording unit 31 (memory, etc.) from the input unit. For example, a program for the calculation unit to calculate the growth degree of the plant, a program for the control unit to control the growth unit, etc. may be stored in advance in the recording unit 31. In addition, a program in an external memory, network, or cloud may be operated in the computer 30 via the input unit and the output unit 36 ​​and controlled by the control unit.

[0067] Figure 1 The plant device shown has a growing unit 51 that can be arbitrarily equipped. The growing unit 51 can control at least one of fertilizer, water, temperature and humidity so that for the plant 1, when the leaf area index exceeds a prescribed range, the growth of the leaves of the plant 1 is inhibited, or when the leaf area index is below a prescribed range, the growth of the leaves of the plant is promoted.

[0068] Figure 2 2 is a schematic diagram showing a cross section of another example of the plant sensor device of the present invention. Figure 2 In the example, as plant 1, a group of strawberry leaves is taken as the object.

[0069] Figure 2 The plant sensor device shown in the figure has a light source fixing unit 41 for fixing the light source 11. The light source fixing unit 41 fixes the light source 11 at a position above the measuring part of the plant 1.

[0070] exist Figure 2In the plant sensor device shown, the radiation sensor 21 has a bandpass filter 23 and is fixed to a radiation sensor fixing unit 42. The radiation sensor fixing unit 42 fixes the radiation sensor 21 below the measuring part of the plant 1 with the light receiving surface 22 facing the measuring part.

[0071] Figure 2 The plant sensor device shown has a connecting member 43 connecting the radiation sensor fixing part 42 and the light source fixing part 41, and can arbitrarily adjust the distance L from the light source 11 to the light receiving surface 22 of the radiation sensor 21. In addition, the distance L from the light source 11 to the light receiving surface 22 of the radiation sensor 21 can also be fixed, for example, in the case of a group of strawberry leaves as the object, it can be set to about 50 cm.

[0072] Figure 2 The plant sensor device shown has a grip portion 44 on a connecting member 43 , and is used as a handheld plant sensor device in which a person can grip the grip portion 44 .

[0073] Figure 2 The plant sensor device shown has an integrated structure connected to a display unit 35, and can display the value of LAI externally.

[0074] In addition, Figure 2 In the plant sensor device shown, a recording unit and a CPU (including a calculation unit and a control unit) are omitted.

[0075] Figure 3 It is a schematic diagram showing a cross section of another example of the plant sensor device of the present invention. Figure 3 This is an example of a large-scale device in which a broad-leaved tree is used as the measurement object as the plant 1 and a partial area of ​​the leaf group of the broad-leaved tree is used as the measurement unit 2 .

[0076] Figure 3 The plant sensor device shown is Figure 2 The plant sensor device shown has a structure in which the positional relationship between the light source 11 and the radiation sensor 21 is reversed upside down (the light source 11 is at the bottom).

[0077] In addition, Figure 3 In the plant sensor device shown, a recording unit and a CPU (including a calculation unit and a control unit) are omitted.

[0078] Hereinafter, preferred embodiments of the plant sensor device of the present invention will be described in detail.

[0079] <Plants>

[0080] In the present invention, the plant to be measured is not particularly limited.

[0081] The target plants include trees, grasses, mosses, ferns, and algae, and preferably plants having chlorophyll, and more preferably trees and grasses having flat leaves.

[0082] Examples of trees include deciduous or evergreen coniferous trees and broad-leaved trees. In the present invention, coniferous trees or broad-leaved trees having a low ratio of branches to leaves are preferably used as objects.

[0083] Examples of grasses include weeds, crops (including edible fruit crops such as strawberries and watermelons), horticultural plants (including horticultural plants whose flowers are ornamental), etc., and particularly preferred are vegetables grown in the open field, vegetables and horticultural plants grown in greenhouses, and vegetables and horticultural plants grown using artificial light in vegetable factories.

[0084] The object may be only one plant or multiple plants. Furthermore, when multiple plants are used as the object, the plant species may be only one or multiple. When only one plant is used as the object, a leaf group is preferably used as the object. When multiple plants are used as the object, a leaf group or a plant community is preferably used as the object.

[0085] Only a part of the plant area may be used as the measurement part. In particular, when large plants such as trees, forests, etc. are used as the object, or when a plurality of small plants are used as the object, it is preferable to use only a part of the plant area as the measurement part.

[0086] Plants can be directly measured in the state of vegetation, or a part obtained from the vegetation can be used as the measurement object. In the present invention, it is preferred to directly measure plants in the state of vegetation. That is, in the preferred embodiment of the plant sensor device of the present invention, non-destructive inspection can be performed, which is more preferred than destructive inspections such as the known harvesting method (a method in which all leaves grown on the plant are removed and the leaf area index is calculated based on the total value). In addition, when used as an optical sensor in the food field, commercially available leafy vegetables and the like can also be used as the measurement object.

[0087] <Light Source>

[0088] The first aspect of the plant sensor device of the present invention has a light source for intermittently irradiating near-infrared light to the plant. On the other hand, in the second aspect of the plant sensor device of the present invention, the light source for irradiating near-infrared light to the plant is sufficient, and the irradiation may be continuous.

[0089] The light source only needs to include at least one near-infrared light source. A plurality of near-infrared light sources may be used, or a near-infrared light source and a light source with a wavelength other than near-infrared may be included. However, from the perspective of cost reduction, it is preferred that the light source only includes a near-infrared light source.

[0090] From the viewpoint of easily suppressing the influence of external light in the surrounding environment, it is preferred that the near-infrared light source irradiates near-infrared light with a peak wavelength of 750nm to 1100nm, and in order to suppress the influence on the photoreceptors of the plant and the influence caused by the difference in the water content of the leaves, it is more preferred that the near-infrared light with a peak wavelength of 800nm ​​to 900nm be irradiated. In addition, wavelength components shorter than 750nm should not be included.

[0091] The type of near-infrared light source is not particularly limited, and examples thereof include LEDs and lasers, and LEDs are preferred.

[0092] As a specific preferred near-infrared light source, an LED having a peak wavelength of about 850 nm can be cited. For example, a commercially available LED for surveillance cameras can be used as a near-infrared light source for a plant sensor device. Figure 4 is the spectrum of sunlight and LED light source (peak wavelength is 850nm). Figure 4 As shown, the spectrum of near-infrared light emitted from an LED light source with a peak wavelength of 850 nm ( Figure 4 LED light source) is equivalent to the solar spectrum ( Figure 4 Therefore, LEDs with a peak wavelength of about 850nm are less affected by external light noise from sunlight. In addition, the spectrum obtained by adding sunlight and the LED light source ( Figure 4 The spectrum of the LED light source is well reflected by the insolation + LED output value. Therefore, it is easy to subtract the output value of the insolation only (as a baseline) from the output value of the insolation + LED from the radiation sensor to stably and accurately obtain the difference A calculated by (NIR output value) - (non-irradiation output value).

[0093] On the other hand, near-infrared light with a peak wavelength of 750nm to 1100nm is less affected by the absorption of pigments (chlorophyll, chlorophyll, etc.) contained in plants, and is therefore preferred. Moreover, near-infrared light above 800nm ​​is less affected by the absorption of the light receptors (photosensitive pigments) of plants, and is therefore more preferred. In addition, chlorophyll has two absorption bands, mainly absorbing blue light (400nm to 500nm) and red light (600nm to 700nm). In addition, there are two types of photosensitive pigments, Pr with an absorption wavelength center at 660nm and Pfr with an absorption wavelength center at 730nm, both of which perform light conversion and affect the growth of plants.

[0094] Furthermore, near-infrared light having a peak wavelength of 750 nm to 1100 nm is also preferable from the viewpoint that the influence of external light noise of an artificial light source is small.

[0095] <Radiation Sensor>

[0096] The plant sensor device of the present invention includes a radiation sensor disposed on the opposite side of a plant from a light source, receives near-infrared light transmitted through the plant, and outputs an output value obtained by photoelectrically converting the transmitted light.

[0097] The shape of the radiation sensor is not limited as long as it can receive the transmitted light after passing through the plant. For example, it can be cylindrical so that the transmitted light can be observed from all directions, or it can be hemispherical, or it can be rod-shaped. In the present invention, the transmitted light is used instead of the reflected light, so the properties of a specific part of the vegetation including the average influence of the scattering and reflection of the light in the vegetation can be reflected, and as long as the area of ​​the light source and the radiation sensor is expanded, the measurement range can be expanded to reflect the overall properties of the vegetation.

[0098] The radiation sensor is preferably connected to the recording unit or the computer storing the recording unit via any output cable or wirelessly. The output value can be output as photon flux density (μmol·m -2 s -1 ) or radiance (W·m -2 ), etc., but since the transmittance (ratio) is ultimately used, there is no restriction on the unit used. Here, the radiance is equivalent to the value obtained by converting the amount of photons per unit area (photon flux density) into energy (radiance). Therefore, the output voltage (mV) indicating the change in the amount of charge after photoelectric conversion by the radiation sensor can be converted into photon flux density (μmol·m -2 s -1 ) and radiance (W·m -2 ) and output in any unit. By multiplying the voltage (mV) after photoelectric conversion by the conversion factor (gain adjustment), it can be easily converted to any unit of radiance and photon flux density. When using the unit of one side as the reference, the output can be easily changed from one side to the other by changing the setting. Radiance (W·m -2 ) = photon flux density (μmol·m -2 s -1 )×Avogadro constant (mol -1 )×Planck constant(Js)×speed of light(ms -1 ) / wavelength(m).

[0099] As radiation sensors, commercially available Si photodiodes and solar radiation sensors can be used. Si photodiodes are quantum-type light detectors that generally have high linear sensitivity in the range of 400nm to 900nm. Thus, by using photodiodes as the light-receiving surface (light-receiving part) of the radiation sensor, the radiation sensor can be miniaturized and its price can be reduced.

[0100] Regarding the distance from the light source to the light receiving surface of the radiation sensor, when grass is used as the object, for example, it can be more than 1 cm, preferably 10 cm to 100 cm. On the other hand, when trees or forests are used as the object, the distance can be more than 100 cm, and the upper limit is not particularly limited, for example, it can be 50 m, preferably 10 m (1000 cm) or less.

[0101] (Bandpass filter)

[0102] The radiation sensor preferably has a bandpass filter that filters out light with a wavelength band less than 750nm. In addition, the radiation sensor preferably only extracts radiation of near-infrared light with a wavelength band of 750nm or more. By using a radiation sensor that can filter and remove wavelengths shorter than the wavelength band of the target near-infrared light, it is possible to improve external light noise resistance. In the case where an LED with a peak wavelength of 850nm is used as a light source, the bandpass filter more preferably filters out light with a wavelength band less than 800nm, and particularly preferably filters out light less than 800nm ​​and light above 1100nm.

[0103] In the radiation sensor, in addition to the bandpass filter and the light receiving surface (light receiving portion), a substrate, a light diffusion plate, and other known structures for adjusting the gain of the voltage (detection signal) after photoelectric conversion and outputting it may be adopted.

[0104] <Light source fixing part, radiation sensor fixing part, connecting member>

[0105] The plant sensor device of the present invention preferably includes a light source fixing unit that fixes the light source.

[0106] Furthermore, the plant sensor device of the present invention preferably includes a radiation sensor fixing unit for fixing the radiation sensor.

[0107] In one example of a preferred embodiment of the present invention, the light source fixing unit preferably fixes the light source at a position above the measuring part of the plant. In this case, the radiation sensor fixing unit preferably fixes the radiation sensor at a position below the measuring part with the light receiving surface facing the measuring part of the plant.

[0108] On the other hand, when a large-scale plant sensor device is used, a power supply, a reflector, and an optical system are required. It is assumed that the light source is larger than the radiation sensor. Therefore, from the perspective of the physical stability of the device, it is preferable to flip the device upside down, with the light source fixing part fixing the light source at a position below the measuring part of the plant, and the radiation sensor fixing part fixing the radiation sensor at a position above the measuring part with the light receiving surface facing the measuring part of the plant.

[0109] In addition, the plant sensor device of the present invention can suppress the influence of external light, so in addition to the vertical use in which the light source and the radiation sensor are arranged in the vertical direction relative to the plant, it can also be used horizontally or tilted in which the light source and the radiation sensor are arranged in the horizontal direction or tilted direction relative to the plant. In particular, in the case of a handheld type, the ability to use it horizontally or tilted is an advantage.

[0110] Furthermore, when the plant sensor device of the present invention includes a radiation sensor fixing portion and a light source fixing portion, it is preferable to include a connecting member that connects the radiation sensor fixing portion and the light source fixing portion.

[0111] The connecting member is preferably retractable and retractable. Also, the distance from the light source to the light receiving surface of the radiation sensor can be fixed to a desired distance.

[0112] In the present invention, it is preferred that the connecting member has a gripping portion. The gripping portion is not particularly limited and may be a handle of a fixed shape or a belt.

[0113] <Records Department>

[0114] The plant sensor device of the present invention has a recording section that records output values ​​from the radiation sensor. The recording section functions as a so-called data recorder.

[0115] The output from the radiation sensor is temporarily input and recorded in the recording unit, and then input to the computing unit. However, the recording unit may be integrated into a component common to the control unit and the computing unit, such as a CPU or a control panel.

[0116] In the first aspect of the present invention, the recording unit records the irradiation period and extinction period of the near infrared light of the light source. Furthermore, the recording unit classifies the output value from the radiation sensor into: (1) NIR output value during the irradiation period of the near infrared light; (2) non-irradiation output value during the extinction period of the near infrared light. By classifying and recording the NIR output value and the non-irradiation output value, the calculation unit can use them to calculate the parameter related to the leaf amount of the plant.

[0117] In the second aspect of the present invention, (1) the NIR output value during the irradiation of near-infrared light among the output values ​​from the radiation sensor is classified into: (1-1) the first NIR output value during the irradiation of the first luminous intensity of the near-infrared light; (1-2) the second NIR output value during the irradiation of the second luminous intensity of the near-infrared light. By classifying and recording the first NIR output value and the second NIR output value in this way, the calculation unit can use them to calculate the parameter related to the leaf amount of the plant.

[0118] The recording unit can classify and record the output values ​​during the irradiation period and the extinction period based on the time (timing) measured by the timing unit such as the clock or timer shown in the accompanying drawings. Alternatively, when the control unit controls the irradiation period and the extinction period, the recording unit can classify and record the output values ​​during the irradiation period and the extinction period based on the time synchronized with the control unit.

[0119] In the first aspect of the present invention, when the control unit described later controls the near-infrared light at two levels of the first luminous intensity and the second luminous intensity as in the second aspect, it is more preferred that the recording unit classifies (1) the NIR output value during the irradiation period of the near-infrared light among the output values ​​from the radiation sensor into: (1-1) the first NIR output value during the irradiation period of the first luminous intensity of the near-infrared light; (1-2) the second NIR output value during the irradiation period of the second luminous intensity of the near-infrared light. By classifying and recording the first NIR output value, the second NIR output value, and the non-irradiation output value, when the calculation unit uses these values ​​to calculate the parameter related to the leaf amount of the plant, the external light noise tolerance can be further improved.

[0120] In the present invention, it is preferable that the recording unit stores in advance software, an application program, a program, a conversion formula, a conversion table, etc. for calculating parameters related to the growth degree of various plants.

[0121] <Calculation Unit>

[0122] The plant sensor device of the present invention preferably includes a calculation unit that calculates a difference A calculated by (NIR output value)-(non-irradiation output value) and converts the difference A into a leaf area index.

[0123] like Figure 5 As shown in FIG. 1 , the NIR output value is the output value (NIR) during the irradiation of near-infrared light at a peak in the graph of the relationship between time from the start of measurement and photon flux density (output value). The non-irradiation output value is Figure 5 The output value during irradiation (Non) at a peak of Figure 5 The part shown in A.

[0124] In the present invention, the leaf area index is preferably a linear function of a logarithmic function in which the difference A or a function thereof is a true number.

[0125] The calculation unit can calculate the leaf area index from the difference A using a leaf area index conversion unit. A program as an example of a leaf area index conversion unit calculates LAI from the difference A based on the fact that the natural logarithm Ln(A) of the difference A calculated by (NIR output value)-(non-irradiation output value) is proportional to the leaf area index LAI. Figure 7 In this way, the relationship between the leaf area index LAI and the 850nm transmittance (difference A) is expressed by an exponential function. Figure 7 The indoor result is: 850nm transmittance (difference A) = 90.645e -0.564×LAI , taking the natural logarithm of both sides, it can be calculated by the relational expression (1) Ln(A) = Ln(90.645) - 0.564 × LAI. In other words, the leaf area index LAI is expressed as a linear function of the logarithmic function with the difference A as a true number. If the relational expression (1) is stored in the recording unit and operated, the leaf area index can be calculated from the difference A. In addition, according to Figure 7 It can be seen that R of relation (1) 2 =0.9915, and there is a very strong correlation between LAI and the difference A calculated by (NIR or output value)-(non-irradiation output value). Therefore, the calculation result using this program can be used as an accurate leaf area index.

[0126] Alternatively, a calibration curve or conversion table may be prepared in advance, and the leaf area index may be calculated based on the difference A. A calibration curve for each vegetation may be stored in advance in a recording unit, and the leaf area index corresponding to the calibration curve or the like may be output based on the calibration curve and the difference A calculated by measuring (NIR output value) - (non-irradiation output value).

[0127] In the present invention, in both the first and second modes, when the control unit described later controls the near infrared light at two levels of the first luminous intensity and the second luminous intensity, the calculation unit calculates the difference B calculated by (the first NIR output value)-(the second NIR output value) and converts it into a leaf area index. When this is used to calculate the parameter related to the leaf amount of the plant, the external light noise tolerance can be further improved by the following mechanism.

[0128] When the NIR output value is controlled and recorded in two steps of 100% and 50%, the 50% output value can be used as a baseline for calculation. That is, the calculation unit calculates the difference B calculated by (100% NIR output value)-(50% NIR output value) and converts it into the leaf area index, thereby eliminating the influence of fluctuations in NIR transmission caused by external light that may occur when the non-irradiation output value is used as a baseline.

[0129] By repeatedly turning on and off the near-infrared light source and repeatedly performing measurement in a short period of time as the NIR output value, the influence of fluctuations in NIR transmission due to external light can also be reduced.

[0130] In the calculation unit, it is preferred that the output value from the beginning to the end of the irradiation period and the extinction period is set to 100%, and the output value of the intermediate period of 25% to 75% is used as the NIR output value and the non-irradiation output value. Figure 5 As an example, it is preferred to set the output value of the intermediate period (mid; the period from 27.5 seconds to 32.5 seconds from the start of the measurement) from the beginning of the irradiation period (ini; about 25 seconds from the start of the measurement) to the end (ter: about 30 seconds from the start of the measurement) as 100% (equivalent to about 5 seconds), and use the output value of the intermediate period (mid; the period from 27.5 seconds to 32.5 seconds from the start of the measurement) of 25% to 75% as the NIR output value. The average value per unit time of the output value of the intermediate period can be used as the NIR output value, and the cumulative value (or its average value) of the output value of the intermediate period can also be used as the NIR output value.

[0131] like Figure 5 As shown in FIG. 1 , the beginning of the irradiation period refers to the portion where the peak of the output value starts to rise at a certain peak of the graph of the relationship between the time from the start of the measurement and the photon flux density (output value). The end of the irradiation period refers to the portion where the peak of the output value gradually decreases and reaches the minimum value.

[0132] <Control Unit>

[0133] The plant sensor device of the present invention preferably further includes a control unit.

[0134] The control unit preferably controls so as to repeat a cycle in which a period of irradiation with the light source and a period of extinction are regarded as one cycle.

[0135] The control unit may increase only one of the illumination period and the extinction period of the light source, but preferably controls them to be equally spaced. For example, the control unit preferably controls the illumination period and the extinction period of the light source to be approximately equally spaced within ±30% of each other, more preferably controls them to be approximately equally spaced within ±20% of each other, and particularly preferably controls them to be approximately equally spaced within ±10% of each other. For example, when the illumination period of the light source is set to 5 seconds, the extinction period is preferably 3.5 seconds to 6.5 seconds, more preferably 4 seconds to 6 seconds, and particularly preferably 4.5 seconds to 5.5 seconds.

[0136] The control unit preferably sets the irradiation period and extinction period of the light source to 1 millisecond to 1 minute, more preferably 10 milliseconds to 10 seconds, and particularly preferably 0.1 seconds to 5 seconds.

[0137] In the first embodiment of the present invention, it is preferred that the control unit controls the light source to irradiate infrared light with a first luminous intensity and a second luminous intensity, and the second luminous intensity is 1 / n times (n is a positive number) the first luminous intensity. And, in the second embodiment of the present invention, the control unit controls the light source to irradiate infrared light with a first luminous intensity and a second luminous intensity, and the second luminous intensity is 1 / n times (n is a positive number) the first luminous intensity. By irradiating the light source with two levels of luminous intensity during measurement, external light noise tolerance is improved. For example, when the first luminous intensity is set to 100%, when n=2, that is, the second luminous intensity can be set to 1 / n=0.5 times, that is, 50%. 1 / n is preferably 0.1 to 0.9, more preferably 0.3 to 0.7, and particularly preferably 0.4 to 0.6.

[0138] <Growth Unit>

[0139] The plant sensor device of the present invention preferably has a growth unit that controls at least one of fertilizer, water, temperature and humidity so as to inhibit the growth of plant leaves when the leaf area index exceeds a specified range, or promote the growth of plant leaves when the leaf area index is lower than a specified range.

[0140] The growing unit is preferably controlled by a control unit.

[0141] The growing unit is not particularly limited, and means used in known vegetable factories or smart agriculture fields, etc., can be adopted. The artificial light source of the wavelength band used in the growing unit preferably does not include near infrared light.

[0142] [Optical measurement method of active plants]

[0143] The active optical measurement method of plants of the present invention is a method using the plant sensor device of the present invention. Unlike the passive optical measurement method of plants, the plant sensor device of the present invention can actively irradiate near-infrared light to plants, shorten the measurement period, and suppress the influence of external light in the surrounding environment, and has these advantages.

[0144] The active optical plant measurement method of the present invention is preferably used for ground truth from remote sensing of the sky or the universe, plant growth measurement of plant growth facilities, forest vegetation measurement, leaf volume measurement of plant communities or leaf groups. In other words, these are also preferred uses of the plant sensor device of the present invention.

[0145] Other preferred aspects of the active optical measurement method of plants of the present invention are the same as the preferred aspects of the plant sensor device of the present invention.

[0146] Example

[0147] The present invention is further specifically described by enumerating examples and comparative examples below. The materials, usage amounts, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed restrictively by the specific examples shown below.

[0148] [Example 1: Plant sensor device of the first embodiment]

[0149] The implementation of the plant sensor device of Example 1 was studied.

[0150] The following process was followed Figure 1 The verification experiment of the plant sensor device of Example 1 having the structure described in , confirmed that the leaf area index LAI can be measured in the field.

[0151] As the light source, a near-infrared light source including only an LED having a peak wavelength of 850 nm and a half-value width of 50 nm or less was used. The light source was arranged on the upper side (vertically upward direction) relative to the leaf group.

[0152] As the radiation sensor, a Si photodiode (commercially available solar radiation sensor) was used. The radiation sensor was arranged on the lower side (vertically lower side) opposite to the light source with respect to the leaf group (plant).

[0153] The memory of a PC having a general-purpose CPU is used as a recording unit to record the output value received by the radiation sensor and subjected to photoelectric conversion.

[0154] The CPU of the PC has a calculation unit and a control unit. The calculation unit can use the leaf area index conversion unit (program) stored in the memory to calculate the difference A calculated by (NIR output value)-(non-irradiation output value) and convert the difference A into the leaf area index.

[0155] The control unit controls the light source so that NIR irradiation starts 5 seconds after the start of measurement and NIR is turned off 5 seconds later. This cycle is repeated as one cycle, thereby intermittently irradiating the leaf group with near-infrared light.

[0156] In Example 1, there was no leaf group in the first cycle (reference), a 5-second extinction period and a 5-second NIR irradiation period were set for the first leaf group in the second cycle, and a 5-second extinction period and a 5-second NIR irradiation period were set for the second leaf group in the third cycle. After the third cycle, a further 5-second extinction period was set.

[0157] The radiation sensor receives the near-infrared light transmitted through the leaves and converts the radiation intensity (W·m -2 ) is recorded in the recording unit as the output value after photoelectric conversion. The output value from the beginning (ini) to the end (ter) of the irradiation period and the extinction period is set to 100%, and the output value of the intermediate period (mid) of 25% to 75% is used as the NIR output value and the non-irradiation output value.

[0158] Furthermore, the leaf area index conversion unit (program) stored in the memory is used to calculate the difference A calculated by (NIR output value) - (non-irradiation output value), and then the difference A is converted into the leaf area index. The obtained results are shown in Figure 5 middle. Figure 5 This is a graph showing the relationship between the time from the start of measurement and the photon flux density (output value) in Example 1. The leaf area index conversion unit (program) calculates LAI from the difference A based on the fact that the natural logarithm Ln(A) of the difference A calculated by (NIR or output value)-(non-irradiation output value) is proportional to the leaf area index LAI.

[0159] from Figure 5 It can be seen that the leaf area index of the first leaf group LAI = 1 and the leaf area index of the second leaf group LAI = 2 can be derived. Furthermore, it can be seen that the leaf area index can be obtained even if the measurement time is as short as about several tens of seconds.

[0160] The non-irradiated output value is an output value measured based on external light such as sunlight. The plant sensor device of Example 1 uses the difference A calculated by (NIR output value)-(non-irradiated output value), that is, the change in the output value caused by the irradiation of the NIR light source, to obtain the leaf area index, thereby being able to substantially eliminate the influence of external light in the surrounding environment.

[0161] Therefore, it can be seen that the plant sensor device of the present invention can suppress the influence of external light in the surrounding environment in order to quantify the growth degree of the plant, and can obtain parameters related to the leaf volume of the plant through a simple and low-cost structure (only one irradiation sensor).

[0162] [Example 2: Plant sensor device according to the first embodiment]

[0163] A verification experiment of the plant sensor device of Example 2 was conducted according to the following process, and the measurement results indoors and outdoors were compared.

[0164] Figure 6 (A) is a photograph of the leaves of the plant to be measured in Example 2 and the radiation sensor used. Figure 6 (B) is a photograph of the structure of the plant sensor device of Example 2. In the plant sensor device of Example 2, the same light source and radiation sensor as those of Example 1 are used.

[0165] In a room where no sunlight enters, while increasing the number of leaves to be measured, near-infrared light is irradiated onto the leaves from a light source in the same manner as in Example 1, and the leaf area index is determined.

[0166] On the other hand, in the open air under sunlight, while increasing the number of leaves to be measured, near-infrared light was irradiated onto the leaves from a light source in the same manner as in Example 1, and the leaf area index was determined.

[0167] From the measurement results for both indoor and outdoor use, the values ​​of 850nm transmittance when the leaf area index was 1, 2, 3, or 4 were obtained and plotted on a graph. Then, an approximate curve was created using an exponential function. The obtained approximate curve has the leaf area index as x and the 850nm transmittance (equivalent to the difference A) as y (%). Indoors, y = 90.645e -0.564x , the correlation coefficient R 2 = 0.9915. In the wild, y = 90.557e -0.517x , the correlation coefficient R 2 =0.983. The obtained results are shown in Figure 7 middle. Figure 7 It is a graph showing the relationship between the leaf area index and the transmittance at 850 nm in indoor and outdoor measurements.

[0168] from Figure 7 It can be seen that the results obtained in the indoor and outdoor measurements are almost the same, and there is almost no influence of indoor lights and sunlight. Therefore, it can be seen that the plant sensor device of the present invention can be used in an artificial light environment and an environment with fluctuating sunlight.

[0169] That is, it can be seen that the plant sensor device of the present invention can suppress the influence of external light in the surrounding environment in order to quantify the growth degree of the plant, and can obtain a high-precision parameter related to the leaf amount of the plant with a simple and low-cost structure.

[0170] [Example 3: Plant sensor device according to the second embodiment]

[0171] The plant sensor device of Example 3 was verified by the following procedure, and it was verified that the leaf area index LAI can be measured in the field when the light source is controlled to irradiate infrared light at a first luminous intensity and a second luminous intensity that is 1 / 2 of the first luminous intensity.

[0172] In Example 3, the following calculation unit is used as a calculation unit, and the control unit is controlled as follows. The calculation unit uses a leaf area index conversion unit (program) stored in the memory to calculate the difference B calculated by (first NIR output value)-(second NIR output value), and then converts the difference B into a leaf area index. Example 3 uses a plant sensor device that is the same as Example 1 except for the above content for measurement.

[0173] The control unit controls the light source to start NIR irradiation with the first luminous intensity (100%) 5 seconds after the start of the measurement, and to start NIR irradiation with the second luminous intensity (50% of the first luminous intensity) 3 seconds later, and to turn off the NIR for 4 seconds after 3 seconds. This period is set as 1 cycle, and the cycle is repeated to intermittently irradiate the leaf group with near-infrared light.

[0174] In Example 3, there was no leaf group in the first cycle (reference). In the second cycle, the first leaf group was provided with a 3-second NIR irradiation period of the first luminous intensity, a 3-second NIR irradiation period of the second luminous intensity, and a 4-second extinction period. In the third cycle, the first leaf group was provided with a 3-second NIR irradiation period of the first luminous intensity, a 3-second NIR irradiation period of the second luminous intensity, and a 4-second extinction period.

[0175] The leaf area index conversion unit (program) calculates LAI from the difference B based on the fact that the natural logarithm Ln(B) of the difference B calculated by (first NIR output value)-(second NIR output value) and the leaf area index LAI are in a proportional relationship.

[0176] from Figure 8 It can be seen that the leaf area index LAI of the first leaf group can be derived as LAI = 1, and the leaf area index LAI of the second leaf group can be derived as LAI = 2. Furthermore, it can be seen that the leaf area index can be obtained even if the measurement time is as short as about several tens of seconds.

[0177] Moreover, the plant sensor device of Example 3 uses the difference B calculated by (first NIR output value)-(second NIR output value), that is, the change in output value caused by irradiation of the NIR light source, to obtain the leaf area index, thereby being able to substantially eliminate the influence of external light in the surrounding environment.

[0178] Therefore, it can be seen that the plant sensor device of the second mode of the present invention can also suppress the influence of external light in the surrounding environment in order to quantify the growth degree of the plant, and obtain parameters related to the leaf amount of the plant through a simple and low-cost structure (only one irradiation sensor).

[0179] Description of symbols

[0180] 1: plant; 2: measuring part; 11: light source; 12: infrared light; 13: transmitted light; 21: radiation sensor; 22: light receiving surface; 23: band pass filter; 30: calculator; 31: recording part; 32: calculation part; 33: control part; 34: CPU; 35: display part; 36: output part; 41: light source fixing part; 42: radiation sensor fixing part; 43: connecting part; 44: holding part; 51: growth unit; 100: plant sensor device; L: distance from the light source to the light receiving surface of the radiation sensor; A: difference calculated by (NIR output value) - (non-irradiation output value); NIR: NIR output value; Non: non-irradiation output value; ini: initial period; mid: middle period; ter: final period.

Claims

1. A plant sensor device, comprising: A light source that intermittently irradiates near infrared light NIR toward the plant; a radiation sensor disposed on a side opposite to the light source with respect to the plant, receiving the near-infrared light transmitted through the plant and outputting an output value obtained by photoelectrically converting the transmitted light; as well as a recording unit that records an output value from the radiation sensor, The recording unit records an irradiation period and an extinction period of the near-infrared light of the light source, The recording unit categorizes the output values ​​from the radiation sensor into: (1) NIR output value during the irradiation of the near infrared light; (2) Non-irradiation output value during the extinction period of the near-infrared light.

2. The plant sensor device according to claim 1, wherein: The plant sensor device includes a calculation unit that calculates a difference A calculated by (NIR output value)-(non-irradiation output value) and converts the difference A into a leaf area index.

3. The plant sensor device according to claim 2, wherein: The leaf area index is a linear function of a logarithmic function with the difference A or a function thereof as a real number.

4. The plant sensor device according to claim 3, wherein: The plant sensor device has a growth unit that controls at least one of fertilizer, water, temperature and humidity so as to inhibit the growth of the leaves of the plant when the leaf area index exceeds a specified range, or promote the growth of the leaves of the plant when the leaf area index is below a specified range.

5. The plant sensor device according to claim 1, wherein: The plant is a group of leaves or a plant community.

6. The plant sensor device according to claim 1, wherein: The light source comprises only a near-infrared light source.

7. The plant sensor device according to claim 6, wherein: The near-infrared light source irradiates near-infrared light of a narrow band having a peak wavelength of 750 nm to 1100 nm and a half-value width of 50 nm or less.

8. The plant sensor device according to claim 1, wherein: The radiation sensor has a bandpass filter that filters out light with a wavelength band less than 750 nm, and only extracts radiation of near-infrared light with a wavelength band of 750 nm or more.

9. The plant sensor device according to claim 1, wherein: The plant sensor device includes a radiation sensor fixing portion for fixing the radiation sensor. The radiation sensor fixing unit fixes the radiation sensor at a position below the measuring part so that the light receiving surface faces the measuring part of the plant.

10. The plant sensor device according to claim 1, wherein: The plant sensor device includes a light source fixing unit for fixing the light source. The light source fixing unit fixes the light source at a position above the measuring part of the plant.

11. The plant sensor device according to claim 1, wherein: The plant sensor device includes a radiation sensor fixing portion for fixing the radiation sensor, a light source fixing portion for fixing the light source, and a connecting member connecting the radiation sensor fixing portion and the light source fixing portion. The distance from the light source to the light receiving surface of the radiation sensor is 1 cm to 1000 cm.

12. The plant sensor device according to claim 11, wherein: The connecting member has a grip portion.

13. The plant sensor device according to claim 1, wherein: The plant sensor device includes a radiation sensor fixing portion for fixing the radiation sensor and a light source fixing portion for fixing the light source. The light source fixing unit fixes the light source at a position below the measuring unit of the plant. The radiation sensor fixing unit fixes the radiation sensor at a position above the measuring part so that the light receiving surface faces the measuring part of the plant.

14. The plant sensor device according to claim 1, wherein: The output values ​​from the start to the end of each of the irradiation period and the extinction period are set to 100%, and the output values ​​in the intermediate period of 25% to 75% are used as the NIR output value and the non-irradiation output value.

15. The plant sensor device according to claim 1, wherein: The irradiation period and the extinction period are both from 1 millisecond to 1 minute.

16. The plant sensor device according to claim 1, wherein: The plant sensor device further comprises a control unit. The control unit controls the irradiation period and the extinction period of the light source to be substantially equally spaced within ±30% of each other.

17. A plant sensor device comprising: A light source that irradiates near infrared light NIR toward the plant; a radiation sensor disposed on a side opposite to the light source with respect to the plant, receiving the near-infrared light transmitted through the plant and outputting an output value obtained by photoelectrically converting the transmitted light; a recording unit configured to record an output value from the radiation sensor; as well as Control Department, The control unit controls the light source to irradiate infrared light with a first luminous intensity and a second luminous intensity, wherein the second luminous intensity is 1 / n times the first luminous intensity, where n is a positive number. The recording unit classifies (1) an NIR output value during the irradiation period of the near-infrared light among the output values ​​from the radiation sensor into: (1-1) a first NIR output value during the irradiation period of the first luminous intensity of the near-infrared light; (1-2) A second NIR output value during the irradiation period of the second emission intensity of the near-infrared light.

18. The plant sensor device according to claim 17, wherein: The plant sensor device includes a calculation unit that calculates a difference B calculated by (first NIR output value)-(second NIR output value) and converts it into a leaf area index.

19. An active optical measurement method of plants, using the plant sensor device according to any one of claims 1 to 18.

20. The method for optical measurement of active plants according to claim 19, wherein: The active optical plant measurement method is used for ground truthing from remote sensing of the sky or space, plant growth measurement in plant growth facilities, vegetation measurement in forests, and leaf mass measurement in plant communities or leaf groups.

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