Moisture content measurement device, moisture content measurement method, and program

Abstract

To provide a moisture content measurement device, moisture content measurement method, and program capable of accurately detecting moisture content of a target object located at a distant position.SOLUTION: A moisture content measurement device comprises: a first light emitting unit that radiates light having an absorption wavelength of water; a second light emitting unit that radiates light having a reference wavelength corresponding to the absorption wavelength of water; a light receiving unit that receives reflected light, reflected by the target object, of the light radiated by the first light emitting unit and the second light emitting unit; and a calculation unit that calculates the moisture content of the target object on the basis of an intensity of the reflected light received by the light receiving unit. A half-value angle of the light radiated by the first light emitting unit and the second light emitting unit is 20 degrees or less, and an angle formed between a light emission optical axis of the light radiated by each of the first light emitting unit and the second light emitting unit and a light receiving optical axis of the light received by the light receiving unit is an angle of 0 to 0.5 times the half-value angle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a moisture content measuring device, a moisture content measuring method, and a program. [Background technology]

[0002] For crop growth, it is important to understand the physical properties of the soil, such as the soil crushing rate and moisture content. There are several techniques for measuring soil moisture content, including an embedded method using dielectric constant measurement, a soil sampling method, and a method using the wavelength of water absorption. Of these, the embedded method using dielectric constant measurement has the problem of being unable to move.

[0003] In the soil sampling method, the collected soil is heated and dried, and the moisture content is calculated by comparing the weight before and after heating and drying. This has the problem of taking a long time to measure. Methods that use the absorption wavelength of water include, for example, using a high-power light source such as a tungsten lamp as a light source by dispersing it, or switching optical filters using a rotating mechanism when spectroscopy is performed. Of these, those that use a high-power light source by dispersing it as a light source have the problem of high power consumption, and those that switch optical filters using a rotating mechanism have the problem of mechanical fragility.

[0004] To address this issue, there is a technology that irradiates light such as near-infrared light, obtains the light receiving output of a light receiving section that receives the reflected light of the irradiated light, and detects the moisture content based on the obtained light receiving output. This technology is used in image forming devices such as copiers, facsimiles, and printers (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-034522 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the image forming device disclosed in Patent Document 1 uses a technology for calculating the moisture content of transfer paper that detects the amount of moisture based on the light-receiving output of a light-receiving unit that receives reflected light. Therefore, it is assumed that the object whose moisture content is to be referenced is located at a short distance, such as a few millimeters to a few centimeters. Therefore, if the device is to be mounted on agricultural machinery and used to calculate the moisture content of soil, the distance to the object would be too far, at several tens of centimeters to several tens of centimeters.

[0007] Therefore, the problem that the present invention aims to solve is to provide a moisture content measuring device, a moisture content measuring method, and a program that can accurately detect the moisture content of an object located at a distance. [Means for solving the problem]

[0008] The moisture content measuring device that solves the above problem comprises a first light-emitting unit that irradiates light with a wavelength absorbed by water, a second light-emitting unit that irradiates light with a reference wavelength corresponding to the absorption wavelength of water, a light-receiving unit that receives light reflected from an object from the light irradiated by the first light-emitting unit and the second light-emitting unit, and a calculation unit that calculates the moisture content of the object based on the intensity of the reflected light received by the light-receiving unit, wherein the half-value angles of the light irradiated by the first light-emitting unit and the second light-emitting unit are each 20 degrees or less, and the angle formed by the light-emitting optical axis of the light irradiated by the first light-emitting unit and the second light-emitting unit and the light-receiving optical axis of the light received by the light-receiving unit is 0 to 0.5 times the half-value angle.

[0009] The first light emitting portion and the second light emitting portion may be arranged in a ring shape surrounding the light receiving portion.

[0010] The illumination device may further include a ball lens that condenses the light emitted by the first light emitting unit and the second light emitting unit.

[0011] The illumination device may further include a diaphragm structure that adjusts the irradiation range of the light emitted by each of the first light emitting section and the second light emitting section.

[0012] The device may further include a holding unit that holds the distance to the target object within a predetermined range.

[0013] The holding portion may be provided on an agricultural machine.

[0014] The apparatus may further include a position sensor for detecting the position of the object.

[0015] Furthermore, positional moisture content information that associates the moisture content of the object calculated by the calculation unit with the position of the object detected by the position sensor may be stored in a storage unit.

[0016] The display device may further include a display control unit that displays the position indicated by the positional moisture content information on map information displayed on the display device.

[0017] Furthermore, the range of the inclination angle β of the light receiving optical axis with respect to an orthogonal axis perpendicular to the reflective surface of the object on which the light irradiated by the first light-emitting unit and the second light-emitting unit is reflected may be expressed as β≧θ / 2+φ, using the radiation angle θ of the first light-emitting unit and the second light-emitting unit and the angle φ between the light of the absorption wavelength and the light of the reference wavelength.

[0018] The light source may further include an angle adjustment mechanism that adjusts the inclination of the first light emitting unit and the second light emitting unit relative to the orthogonal axis.

[0019] The angle adjustment mechanism may also adjust the inclination when the moisture content of the object is expected to be high.

[0020] The optical element may further include a first polarizing plate that transmits the light of the absorption wavelength and the light of the reference wavelength, and a second polarizing plate that transmits the reflected light and polarizes the reflected light by 90 degrees relative to the light of the absorption wavelength and the light of the reference wavelength.

[0021] Furthermore, a moisture content measuring method that solves the above problem is a moisture content measuring method in which a computer calculates the moisture content of an object based on the intensity of reflected light received by a light receiving unit that receives light reflected from the object, the light being irradiated by a first light emitting unit that irradiates light of a wavelength absorbed by water and a second light emitting unit that irradiates light of a reference wavelength corresponding to the absorption wavelength of water, and the first light emitting unit and the second light emitting unit are positioned so that the half-value angles of the light irradiated by the first light emitting unit and the second light emitting unit are each 20 degrees or less, and the angle formed by the light emitting optical axis of the light irradiated by the first light emitting unit and the second light emitting unit, respectively, and the light receiving optical axis of the light received by the light receiving unit is 0 to 0.5 times the half-value angle.

[0022] Furthermore, a program that solves the above problem causes a computer to calculate the moisture content of an object based on the intensity of reflected light received by a light receiving unit that receives light reflected from the object, the light being irradiated by a first light emitting unit that irradiates light of a wavelength absorbed by water and a second light emitting unit that irradiates light of a reference wavelength corresponding to the absorption wavelength of water, wherein the first light emitting unit and the second light emitting unit are positioned so that the half-value angles of the light irradiated by the first light emitting unit and the second light emitting unit are each 20 degrees or less, and the angle formed by the light emitting optical axis of the light irradiated by the first light emitting unit and the second light emitting unit, respectively, and the light receiving optical axis of the light received by the light receiving unit is 0 to 0.5 times the half-value angle. [Effects of the Invention]

[0023] According to the moisture content measuring device, moisture content measuring method, and program of the present invention, the moisture content of an object located at a distance can be detected with high accuracy. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a block diagram showing an example of the configuration of a moisture content measuring device 1 of a first embodiment. [Figure 2] FIG. 2 is a perspective view showing the appearance of the optical unit 10. [Figure 3] 1 is an elevational cross-sectional view passing through a first absorption LED 31, a first reference LED 41, and a second reference LED 42 in the optical unit 10. FIG. [Figure 4] 1 is a graph showing the absorption spectrum of water for each wavelength. [Figure 5] 10 is a graph showing the intensity ratio obtained by two-point calibration. [Figure 6] 10 is a flowchart illustrating an example of a process for measuring the moisture content of an object. [Figure 7] 4 is a diagram schematically showing the relationship between the first irradiation light, the second irradiation light, and the light received by the photodiode 70. FIG. [Figure 8] 10 is a graph showing the received light intensity of the reflected light of the first irradiation light and the second irradiation light and the intensity ratio thereof versus the distance from the optical unit 10 to the object. [Figure 9] FIG. 2 is a block diagram showing an example of the configuration of a moisture content measuring device 2 according to a second embodiment. [Figure 10] FIG. 2 is a perspective view of a rotary 80 provided with an optical unit 10. [Figure 11] FIG. 10 is a perspective view showing an example of another mounting mode of the optical unit 10. [Figure 12] 2 is an explanatory diagram illustrating an example of the arrangement of an absorption LED 30 and a reference LED 40 in the optical unit 10. FIG. [Figure 13] 10A and 10B are diagrams illustrating an example of a mode for adjusting the irradiation directions of an absorption LED 30 and a reference LED 40. FIG. [Figure 14] 10 is a diagram schematically illustrating a state in which the optical unit 10 of the third embodiment emits a first irradiation light beam B11 and a second irradiation light beam B12 and receives reflected light beams. FIG. [Figure 15] 10 is a diagram schematically illustrating a state in which first irradiation light B11 and second irradiation light B12 are reflected by soil. FIG. [Figure 16]FIG. 10 is a diagram showing a relationship based on the soil moisture content predicted from the reflectance ratio. [Figure 17] 1 is a graph showing the minimum tilt angle on the vertical axis and the distance from the soil surface to the photodiode 70 on the horizontal axis. [Figure 18] FIG. 10 is a side view of a roller unit 85 provided with an angle adjustment mechanism 95. [Figure 19] 10 is a diagram schematically illustrating a state in which the optical unit 10 of the fourth embodiment emits first irradiation light and second irradiation light and receives reflected light. FIG. [Figure 20] 10 is a diagram schematically illustrating a state in which first irradiation light B11 and second irradiation light B12 that have passed through a first polarizing plate 51 are reflected by soil. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, a moisture content measuring device, a moisture content measuring method, and a program according to the present invention will be described with reference to the drawings.

[0026] (First embodiment) In the moisture content measuring device of the first embodiment, the light having the absorption wavelength of water irradiated by the first light emitting unit and the light having a reference wavelength corresponding to the absorption wavelength of water irradiated by the second light emitting unit are received by the light receiving unit. The half-value angles of the light irradiated by the first light emitting unit and the second light emitting unit are both 20 degrees or less. The angle formed by the light emitting axis of the light irradiated by the first light emitting unit and the light receiving axis of the light received by the light receiving unit is 0 to 0.5 times the half-value angle.

[0027] The moisture content measuring device calculates the moisture content of the object in a calculation unit based on the intensity of the reflected light received by the light receiving unit (received light intensity). The calculated moisture content may be any index related to the moisture contained in the object, and may be, for example, the amount of moisture or the moisture content rate. The moisture content measuring device measures the moisture content by calculating the moisture content in the calculation unit.

[0028] 1 is a block diagram showing an example of the configuration of a moisture content measuring device 1 of the first embodiment. The moisture content measuring device 1 includes, for example, an optical unit 10 and a control device 100. The optical unit 10 includes, for example, a holder 20, an absorption LED (Light Emitting Diode) 30, a reference LED 40, a ball lens 50, an aperture structure 60, and a photodiode 70.

[0029] The absorption LED 30 is an LED that emits light with a wavelength that is absorbed by the target (e.g., water). The reference LED 40 is an LED that emits light with a wavelength that is less absorbed by the target around the target. In the following explanation, when there are multiple components with the same function, they will be separated as necessary by assigning numbers such as 1st and 2nd, by changing the first digit of the symbol, by assigning a sub-number, or by other means.

[0030] Fig. 2 is a perspective view showing the appearance of the optical unit 10. Fig. 3 is an elevational cross-sectional view passing through the first absorption LED 31, the first reference LED 41, and the second reference LED 42 in the optical unit 10. The holder 20 includes, for example, a base member 21, a holding member 22, and an LED holder 23. The base member 21 is disk-shaped. The holding member 22 is provided to protrude from one surface of the base member 21. The holding member 22 is provided with a central holding portion 22A in the center and peripheral holding portions 22B1 to 22B6 that are arranged in a ring shape surrounding the central holding portion 22A.

[0031] The LED holder 23 includes a central LED holder 23A held by a central holding portion 22A, and peripheral LED holders 23B1 to 23B6 held by peripheral holding portions 22B1 to 22B6, respectively. A photodiode 70 is housed in the central holding portion 22A, and the central LED holder 23A holds the central holding portion 22A housing the photodiode 70. The peripheral holding portions 22B1 to 22B6 house the absorption LED 30 and the reference LED 40, and the peripheral holding portions 22B1 to 22B6 hold the peripheral LED holders 23B1 to 23B6 housing the absorption LED 30 and the reference LED 40, respectively.

[0032] The absorbing LEDs 30 include a first absorbing LED 31 and a second absorbing LED 32. The absorbing LEDs 30 are LEDs that emit light with a wavelength absorbed by water, for example, a wavelength of approximately 1.9 μm or 1.45 μm. In this embodiment, an LED with a wavelength of 1.9 μm is used. The first absorbing LED 31 is held by the second peripheral holding part 22B2 together with the second peripheral LED holder 23B2, and the second absorbing LED 32 is held by the fifth peripheral holding part 22B5 together with the fifth peripheral LED holder 23B5. The absorbing LEDs 30 are an example of a first light-emitting part.

[0033] The reference LEDs 40 include a first reference LED 41 to a fourth reference LED 44. As the reference LEDs 40, LEDs that emit light with a wavelength close to the wavelength of the light (hereinafter referred to as the first irradiation light) emitted by the absorbing LEDs 30, for example, 1.6 μm to 2.2 μm when the wavelength of the first irradiation light is 1.9 μm, are used.

[0034] When the wavelength of the first irradiation light is 1.45 μm, an LED that emits light with a wavelength of 1.2 μm to 1.55 μm is used as the reference LED 40. In this embodiment, LEDs that emit light with a wavelength of 1.6 μm are used as the first reference LED 41 and the third reference LED 43, and LEDs that emit light with a wavelength of 2.2 μm are used as the second reference LED 42 and the fourth reference LED 44. The reference LED 40 is an example of a second light-emitting unit.

[0035] The first reference LED 41 and the second reference LED 42 are arranged adjacent to the first absorbing LED 31, and the third reference LED 43 and the fourth reference LED 44 are arranged adjacent to the second absorbing LED 32. The first reference LED 41 is held by the first peripheral holding portion 22B1 together with the first peripheral LED holder 23B1, the second reference LED 42 is held by the third peripheral holding portion 22B3 together with the third peripheral LED holder 23B3, the third reference LED 43 is held by the fourth peripheral holding portion 22B4 together with the fourth peripheral LED holder 23B4, and the fourth reference LED 44 is held by the sixth peripheral holding portion 22B6 together with the sixth peripheral LED holder 23B6.

[0036] 3, a ball lens 50 is disposed at the light emitting portion of the first absorption LED 31, the first reference LED 41, and the second reference LED 42. A ball lens 50 is also disposed at the light emitting portion of the other absorption LED 30 and the reference LED. The ball lens 50 condenses the first irradiation light and the light irradiated by the reference LED (hereinafter referred to as the second irradiation light). A ball lens 50 is also provided at the light receiving portion of the photodiode 70, and the light emitting angle of the absorption LED 30 and the reference LED 40 is made the same as the light receiving angle of the photodiode 70.

[0037] An aperture structure 60 is provided beyond the absorbing LED 30 and the reference LED 40 via the ball lens 50. The aperture structure 60 is formed by drilling and processing the base member 21 of the holder 20. The aperture structure 60 adjusts the irradiation range of the light irradiated by the absorbing LED 30 and the reference LED 40 and emitted by the ball lens.

[0038] The half-power angles of the first irradiation light and the second irradiation light are each 20 degrees or less. The half-power angles are determined by the distances between the absorption LED 30 and the reference LED 40 and the ball lens 50, in other words, the deviations from the focal length. The aperture structure 60 reduces unnecessary reflections and stray light directly incident on the photodiode 70. The aperture structure 60 does not necessarily have to be provided. The angle between the emission optical axis of the first irradiation light (hereinafter referred to as the first emission optical axis) and the reception optical axis of the light received by the photodiode 70 (hereinafter referred to as the PD reception optical axis) is 0 to 0.5 times the half-power angle. The angle between the emission optical axis of the second irradiation light (hereinafter referred to as the second emission optical axis) and the PD reception optical axis is 0 to 0.5 times the half-power angle. The angle between the first emission optical axis and the PD reception optical axis and the angle between the second emission optical axis and the PD reception optical axis are all the same.

[0039] The photodiode 70 receives the reflected light of the first irradiation light and the second irradiation light reflected by the object. The photodiode 70 outputs an intensity signal according to the intensity of the received reflected light to the control circuit 160. The intensity signal includes an intensity signal for each reflected light of a different wavelength. The photodiode 70 is an example of a light receiving unit.

[0040] The optical unit 10 is disposed, for example, facing in the direction in which the first irradiation light and the second irradiation light strike the object. The object may be anything, but is, for example, soil on which agricultural machinery such as a tractor or a rotary pulled by a tractor runs. When the object is soil, the moisture content measuring device 1 measures the moisture content of the soil.

[0041] The first irradiation light and the second irradiation light are reflected by the soil and become reflected light. The reflected light is emitted in a direction including the direction of the photodiode 70 in the optical unit 10. The photodiode 70 receives the emitted reflected light, generates an intensity signal based on the intensity of the received reflected light, and outputs the intensity signal to the control device 100.

[0042] 1, the input / output interface 11 is provided, for example, in a smartphone or personal computer capable of wireless or wired communication with the control device 100. The input / output interface 11 provided in a smartphone is configured, for example, with a touch panel. The input / output interface 11 provided in a personal computer includes, for example, an input interface and an output interface.

[0043] The input interface is realized by, for example, a mouse, keyboard, touch panel, trackball, switch, button, joystick, camera, infrared sensor, microphone, etc. The output interface includes, for example, a display. The display displays various types of information. The display is, for example, a liquid crystal display, a CRT (Cathode Ray Tube), an organic EL (Electroluminescence) display, etc.

[0044] The control device 100 includes, for example, a driver group 110, an amplifier unit 120, a converter unit 130, a communication unit 150, a control circuit 160, and a storage unit 170. The driver group 110 includes a first driver 111 to a sixth driver 116. The first driver 111 to the sixth driver 116 turn on or off the first reference LED 41, the first absorption LED 31, the second reference LED 42, the third reference LED 43, the second absorption LED 32, and the fourth reference LED 44, respectively, based on drive signals output by the control circuit 160.

[0045] The conversion unit 130 converts the current of the intensity signal output by the photodiode 70 so that it can be input to the control circuit 160. The conversion unit 130 outputs the converted intensity signal to the amplification unit 120. The amplification unit 120 amplifies the intensity signal converted by the conversion unit 130, and outputs the amplified intensity signal to the control circuit 160. The communication unit 150 includes a communication interface such as a network interface card (NIC), for example.

[0046] The control circuit 160 includes, for example, an acquisition unit 161, a drive control unit 162, and a calculation unit 163. The control circuit 160 is realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device (non-transitory storage medium) such as an HDD (Hard Disk Drive) or flash memory, or may be stored in a removable storage medium (non-transitory storage medium) such as a DVD or CD-ROM, and installed by inserting the storage medium into a drive device. The program may be updated using a change (update) technology using communication technology (OTA: Over The Air).

[0047] The acquiring unit 161 acquires an intensity signal indicating the intensity of the reflected light that is output by the photodiode 70, converted by the converting unit 130, and amplified by the amplifying unit 120. The intensity of the reflected light included in the intensity signal acquired by the acquiring unit 161 is the reflection intensity that is converted by the converting unit 130 and amplified by the amplifying unit 120.

[0048] When measuring the moisture content of an object, the drive control unit 162 outputs drive signals to the driver group 110 to control the light irradiation by the absorption LED 30 and the reference LED 40. For example, the drive control unit 162 individually lights up the plurality of absorption LEDs 30 and reference LEDs 40 so that the lit absorption LEDs 30 and reference LEDs 40 move sequentially. For example, the drive control unit 162 outputs drive signals to light up the first reference LED 41, the first absorption LED 31, the second reference LED 42, the third reference LED 43, the second absorption LED 32, the fourth reference LED 44, and the first reference LED 41 in this order.

[0049] The calculation unit 163 calculates the moisture content of the object based on the intensity of the reflected light indicated by the intensity signal acquired by the acquisition unit 161.

[0050] Figure 4 is a graph showing the absorption spectrum of water for each wavelength. The absorption spectrum of water is highest at 1450 nm, 1940 nm, and 2900 nm. Therefore, by irradiating an object with light close to the wavelengths where the absorption spectrum of water is highest, and measuring the intensity of the reflected light and the intensity of the reflected light at a nearby wavelength (reference light) with low absorption, the moisture content of the object can be determined from the ratio of these two values.

[0051] For example, the intensity of light reflected from an object with a water content of x and having a wavelength of 1.9 μm irradiated by the absorbing LED 30 is defined as the absorbed reflected light intensity R19(x), and the reflection intensities of light having wavelengths of 1.6 μm and 2.2 μm irradiated by the reference LED 40 are defined as the first reference reflected light intensity R16(x) and the second reference reflected light intensity R22(x), respectively. The calculation unit 163 uses the absorbed reflected light intensity R19(x), the first reference reflected light intensity R16(x), and the second reference reflected light intensity R22(x) to perform a linear approximation by two-point calibration with a known x as shown in the following equation (1): 1-a×R19(x) / (R16(x)+b×R22(x))...(1) where a and b are calibration coefficients.

[0052] Fig. 5 is a graph showing the intensity ratio obtained by two-point calibration. Fig. 5 shows a first curve M1 showing the absorbed reflected light intensity R19, a second curve M2 showing the first reference reflected light intensity R16, a third curve M3 showing the second reference reflected light intensity R22, and a second approximate curve NS2 calculated by equation (1). The calculation unit 163 calculates the moisture content (moisture content) of the object using equation (1).

[0053] Next, a process for measuring the moisture content of an object will be described. FIG. 6 is a flowchart showing an example of a process for measuring the moisture content of an object. In the initial stage, all of the absorption LEDs 30 and reference LEDs 40 are turned off. The drive control section 162 of the control circuit 160 in the control device 100 first turns on the first reference LED 41 and the third reference LED 43 (step S101). When turned on, the first reference LED 41 and the third reference LED 43 irradiate light toward the object. The second irradiation light irradiated by the first reference LED 41 and the third reference LED 43 is reflected by the object and emits reflected light.

[0054] Next, the photodiode 70 receives the reflected light emitted by the object (step S103). The photodiode 70 generates an intensity signal based on the intensity of the received reflected light, and outputs the generated intensity signal to the control device 100 (step S105). The control device 100 converts the output intensity signal using the conversion unit 130, amplifies it using the amplification unit 120, and then acquires it using the acquisition unit 161 of the control circuit 160.

[0055] Next, the drive control unit 162 turns off the first reference LED 41 and the third reference LED 43 (step S107), and turns on the first absorbing LED 31 and the second absorbing LED 32 (step S109). The first absorbing LED 31 and the second absorbing LED 32 are turned on to irradiate light toward the object. The first irradiation light irradiated by the first absorbing LED 31 and the second absorbing LED 32 is reflected by the object and emits reflected light.

[0056] The photodiode 70 receives reflected light emitted by the object (step S111). The photodiode 70 generates an intensity signal based on the intensity of the received reflected light, and outputs the generated intensity signal to the control device 100 (step S113). The control device 100 converts the output intensity signal using the conversion unit 130, amplifies it using the amplification unit 120, and then acquires it using the acquisition unit 161 of the control circuit 160.

[0057] Next, the drive control unit 162 turns off the first absorption LED 31 and the second absorption LED 32 (step S115), and turns on the second reference LED 42 and the fourth reference LED 44 (step S117). When the second reference LED 42 and the fourth reference LED 44 are turned on, they irradiate light toward the object. The second irradiation light irradiated by the second reference LED 42 and the fourth reference LED 44 is reflected by the object and emits reflected light.

[0058] The photodiode 70 receives reflected light emitted by the object (step S119). The photodiode 70 generates an intensity signal based on the intensity of the received reflected light, and outputs the generated intensity signal to the control device 100 (step S121). The control device 100 converts the output intensity signal using the conversion unit 130, amplifies it using the amplification unit 120, and then acquires it using the acquisition unit 161 of the control circuit 160. Thereafter, the drive control unit 162 turns off the second reference LED 42 and the fourth reference LED 44 (step S123).

[0059] Next, the calculation unit 163 determines whether the number of times the series of processes from step S101 to step S123 (hereinafter referred to as measurement process) has been executed has reached 200 (step S125). If it is determined that the number of times the measurement process has been executed has not reached 200, the calculation unit 163 increments (+1) the number of times the measurement process has been executed, and returns the process to step S101. The number of measurements may be more or less than 200. The more the number of measurements is increased, the more the influence of noise can be reduced, and the fewer the number of measurements is, the shorter the measurement time can be.

[0060] When it is determined that the number of times the measurement process has been executed reaches 200, the calculation unit 163 calculates the moisture content of the object (soil) based on the results of the 200 executed measurement processes (step S129). At this time, the calculation unit 163 calculates the moisture content of the object (soil) using the calibration coefficients a and b determined during calibration and equation (1). In this way, the moisture content measuring device 1 ends the process shown in FIG.

[0061] In the moisture content measuring device 1 of the embodiment, the optical unit 10 has a first irradiation light and a second irradiation light each having a half-value angle of 20 degrees or less, and the angle formed by the first light emission optical axis and the second light emission optical axis and the PD light receiving optical axis is 0 to 0.5 times the half-value angle. Therefore, it is possible to measure the moisture content even if the size of the object (distance to the object) varies. The principle behind this is explained below.

[0062] The relationship between the first and second irradiation lights and the light received by the photodiode 70 will now be described. Generally, the light emitted by an LED is not coherent, so the narrower the radiation angle of the light emitted by the LED, the higher the intensity. The first and second irradiation lights both have half-value angles of 20 degrees or less, and it is assumed that the intensity of the reflected light of the first and second irradiation lights is the intensity of the light received by the photodiode 70 required to measure moisture content.

[0063] Furthermore, if the angles formed by the absorbing LED 30 and the reference LED 40 and the photodiode 70 are within half the radiation angle of the LEDs, there will be overlap between the irradiation areas of the absorbing LED 30 and the reference LED 40 and the light receiving area of ​​the photodiode 70. This point will be explained with reference to Fig. 7. Fig. 7 is a diagram schematically showing the relationship between the first irradiation light, the second irradiation light, and the light received by the photodiode 70.

[0064] For example, the first irradiation light B11 is assumed to be emitted from the absorption LED 30 with a spread of the half-value angle. Similarly, the second irradiation light B12 is assumed to be emitted from the reference LED 40 with a spread of the half-value angle. A light-receiving range B21 in which the photodiode 70 can receive the reflected light of the first irradiation light B11 and the second irradiation light B12 has a spread similar to that of the first irradiation light B11 and the second irradiation light B12, and becomes wider as it moves away from the photodiode 70.

[0065] Here, the position where the optical unit 10 is provided is defined as a reference position P0, and at a first position P1 closest to the reference position P0, there are overlapping portions between the irradiation area SA11 of the first irradiation light B11 (hereinafter referred to as the first irradiation area) and the light receiving area SA21 of the photodiode 70 (hereinafter referred to as the PD light receiving area), and between the irradiation area SA12 of the second irradiation light B12 (hereinafter referred to as the second irradiation area) and the PD light receiving area SA21. This makes it possible to measure the moisture content of an object located farther away than the distance from the reference position P0 to the first position P1, and the range farther from the optical unit 10 than the distance from the reference position P0 to the first position P1 is the moisture content measurable range CX1.

[0066] Within the moisture content measurable range CX1, there is a cross point α where three optical axes—the first light-emitting optical axis, the second light-emitting optical axis, and the PD light-receiving optical axis—intersect. When an object is located closer to the optical unit 10 than the cross point α, the accuracy of measuring the moisture content of the object can be improved. Here, if the angle between the first light-emitting optical axis and the PD light-receiving optical axis, and between the second light-emitting optical axis and the PD light-receiving optical axis, is large, for example, exceeding 10 degrees to approximately 15 degrees, then the cross point α becomes too close to the optical unit 10.

[0067] An optical unit 10 with a close cross point α may be suitable for measuring the moisture content of an object at a position close to the optical unit 10, for example, at a position of about several mm. However, when the optical unit 10 is mounted on an agricultural machine to measure the moisture content of soil, for example, the distance from the optical unit 10 to the soil, which is the object, is large, at several tens of centimeters (several hundred mm), and therefore an optical unit 10 with a close cross point α is not suitable for mounting on an agricultural machine to measure the moisture content of soil.

[0068] In this regard, in the moisture content measuring device 1 of the first embodiment, the angle formed by the first and second light emission optical axes and the PD light receiving optical axis is 0 to 0.5 times the half-value angle (0 to 10 degrees). Therefore, the cross point α can be located at a position far from the optical unit 10, for example, at a position about 10 cm away.

[0069] At a second reference position farther from the reference position P0 than the first position P1, the overlapping range of the first irradiation region SA11 and the PD light receiving region SA21 and the overlapping range of the second irradiation region SA12 and the PD light receiving region SA21 are wider than at the first reference position. Furthermore, at the n-th position Pn (n = a positive integer), the overlapping range of the first irradiation region SA11 and the PD light receiving region SA21 and the overlapping range of the second irradiation region SA12 and the PD light receiving region SA21 are wider than at the n-1-th position Pn-1.

[0070] Here, if the angle formed by the first and second light emission optical axes and the PD light receiving optical axis is 0 to 0.5 times the half-value angle, there will be a range where the first illumination area SA11 and second illumination area SA12 overlap with the PD light receiving area SA21 even at infinity. Therefore, the moisture content measuring device 1 of the first embodiment can be mounted on an agricultural machine and made suitable for measuring the moisture content of soil.

[0071] Next, we will explain the light intensity of reflected light received by the photodiode 70. The light intensity of reflected light received by the photodiode 70 varies depending on the distance between the optical unit 10 and the object. Fig. 8 is a graph showing the light intensity of reflected light received of the first irradiation light and the second irradiation light and the intensity ratio thereof versus the distance from the optical unit 10 to the object.

[0072] When the distance from the optical unit 10 to the object is a first distance L1 (the distance from the reference position P0 to the first position P1, P1-P0), the photodiode 70 cannot receive reflected light, and the received light intensity is 0. The first distance L1 is, for example, approximately 50 mm. When the distance from the optical unit 10 to the object exceeds the first distance L1, the received light intensity (hereinafter referred to as the first received light intensity) PL1 of the reflected light of the first irradiation light (hereinafter referred to as the first reflected light) and the received light intensity (hereinafter referred to as the second received light intensity) PL2 of the reflected light of the second irradiation light (hereinafter referred to as the second reflected light) both increase, making it possible to measure the moisture content based on the received light intensity of the reflected light received by the photodiode 70.

[0073] Next, when the distance from the optical unit 10 to the object reaches a second distance L2, both the first received light intensity PL1 and the second received light intensity PL2 decrease, but the received light intensity necessary for measuring moisture content is maintained. The second distance L2 is, for example, approximately 70 mm. Furthermore, when the distance from the optical unit 10 to the object reaches a third distance L3, the noise level NL for measuring the intensity of reflected light is reached. In this case, there is a high possibility that the first received light intensity PL1 and the second received light intensity PL2 will contain a large amount of error. The third distance L3 is, for example, approximately 230 mm.

[0074] Furthermore, when the distance between the optical unit 10 and the object is from the first distance L1 to the third distance L3, the intensity ratio PB of the first reflected light and the second reflected light is 0.1 or more, which is an intensity ratio that can be used to measure moisture content. Therefore, it can be seen that the range from the first distance L1 to the third distance L3 is the moisture content measurable range CX2.

[0075] The moisture content measuring device 1 of the first embodiment receives reflected light of first and second irradiation lights irradiated onto soil, which is an object, and measures the moisture content of the soil based on the intensity of the reflected light. Here, the half-value angles of the first and second irradiation lights are each 20 degrees or less, and the angles formed by the first and second emitted light axes and the PD receiving light axis are 0 to 0.5 times the half-value angles of the first and second irradiation lights. Because the half-value angles of the first and second irradiation lights are 20 degrees or less, high-intensity light beams overlap even at infinity, enabling moisture content measurement even for objects located far from the optical unit 10. Therefore, the moisture content of objects located far from the optical unit 10 can be accurately detected.

[0076] (Second embodiment) Next, a moisture content measuring device according to a second embodiment will be described. Fig. 9 is a block diagram showing an example of the configuration of the moisture content measuring device 2 according to the second embodiment. The moisture content measuring device 2 according to the second embodiment differs from the first embodiment mainly in that the optical unit 10 is provided on an agricultural machine, for example, a rotary, and that a GNSS (Global Navigation Satellite System) device is provided. Furthermore, the moisture content measuring device 2 according to the second embodiment differs from the first embodiment mainly in that a display control unit 164 is provided in the control circuit 160, and that a farm field map 171 is stored in the memory unit 170.

[0077] In the second embodiment, the same members and elements as in the first embodiment are given the same numbers and their description may be omitted. In the second embodiment, the agricultural machine to which the optical unit is attached is a rotary, but the agricultural machine may be a self-propelled machine or a machine (attachment) towed by a tractor or the like, such as a tractor, combine, rotary, plow, trailer, or seed machine.

[0078] FIG. 10 is a perspective view of a rotary 80 provided with an optical unit 10. FIG. 18 shows coordinate axes of an XYZ Cartesian coordinate system. The X axis is an axis in the front-to-rear direction of the rotary 80 that is parallel to the horizontal plane (XY plane). The Y axis is an axis in the left-to-right direction of the rotary 80 that is parallel to the horizontal plane. The Z axis is an axis in the height direction of the rotary 80 that is perpendicular to the horizontal plane. The rotary 80 includes, for example, a rotary body 81 and a roller unit 82. The roller unit 82 is provided at the rear end of the rotary body 81. The roller unit 82 includes a parallel link mechanism 83. A roller 84 is attached to the parallel link mechanism 83. The optical unit 10 is attached to the parallel link mechanism 83 together with the roller 84. The parallel link mechanism 83 maintains the distance from the optical unit 10 to the soil within a predetermined range. The parallel link mechanism 83 is an example of a holding unit.

[0079] The roller 84 travels across the soil in the field as the rotary 80 travels. In principle, the optical unit 10 is placed at a fixed distance from the soil, but the distance varies depending on the size of the soil mass. The optical unit 10 measures the moisture content of the soil in an environment where the distance from the soil varies.

[0080] The GNSS device 90 is attached directly above the optical unit 10. The GNSS device 90 detects its own position by receiving GNSS signals transmitted by GNSS satellites. The GNSS device 90 transmits its detected position to the control device 100 as position information indicating the positions of the rotary 80 and the optical unit 10 attached to the rotary 80. The position of the optical unit 10 corresponds to the position of the soil. The GNSS device 90 detects the position of the soil. The GNSS device 90 is an example of a position sensor. The GNSS device 90 may be attached to the parallel link mechanism 83 in relation to its attachment position, or may be attached to the rotary main body 81 if accuracy is not a high priority.

[0081] The control device 100 may be provided in the rotary 80, for example, near the driver's seat, or, for example, the display of the input / output interface 11 may be provided near the driver's seat and the other components may be provided in other positions on the rotary 80. The control device 100 may also be provided in a position other than the rotary 80, for example, in the farmer's home. In this case, the optical unit 10 and the GNSS device 90 may be provided with a communication device that transmits data to the control device 100, and may transmit information to the control device 100 via a wireless network or the like.

[0082] The acquisition unit 161 in the control circuit 160 of the control device 100 acquires the position information transmitted by the GNSS device 90. When calculating the moisture content of the soil, the calculation unit 163 associates the position information acquired by the acquisition unit 161 when acquiring the light receiving intensity for calculating the moisture content with the moisture content of the soil. The calculation unit 163 generates the moisture content of the soil associated with the position information as position moisture content information and stores it in the storage unit 170.

[0083] The display control unit 164 provides the input / output interface 11 with information for displaying various types of information on a display included in the input / output interface 11. The display control unit 164 reads out the field map 171 stored in the storage unit 170, and displays the position indicated by the positional moisture content information generated by the calculation unit 163 on the field map 171 displayed on the display. The field map 171 is an example of map information. The display is an example of a display device.

[0084] The moisture content measuring device 2 of the second embodiment has the same effects as the moisture content measuring device 1 of the first embodiment. Furthermore, in the moisture content measuring device 2 of the second embodiment, the position information of the optical unit 10 when measuring the moisture content of the soil is associated with the calculated moisture content, and stored in the storage unit 170 as the moisture content of the soil at the position detected by the GNSS device 90. Therefore, it is possible to measure the moisture content of the soil at each position in the field, and to create, for example, a moisture content map of the field.

[0085] Furthermore, the moisture content measuring device 2 of the second embodiment displays the moisture content of the soil at the position detected by the GNSS device 90 on the farm field map 171 on the display of the input / output interface 11. This makes it easier to visually recognize the moisture content in the farm field.

[0086] Other roller units may be attached to the rotary body 81. Fig. 11 is a perspective view showing an example of another roller unit 85. The roller unit 85 includes a parallel link mechanism 83, and the parallel link mechanism 83 has a plurality of rollers 84, for example, two rollers 84, arranged side by side in the direction of travel of the rotary 80. The optical unit 10 is disposed between the two rollers 84, and the two rollers 84 are disposed in front of and behind the optical unit 10, respectively. By disposing the rollers 84 in front of and behind the optical unit 10, the distance from the optical unit 10 to the soil can be accurately maintained within a predetermined range.

[0087] In each of the above embodiments, the optical unit 10 includes two absorbing LEDs 30 and four reference LEDs 40, but the optical unit 10 may include one or more absorbing LEDs 30 and one or more reference LEDs 40. Fig. 12 is an explanatory diagram illustrating an example of the arrangement of the absorbing LEDs 30 and the reference LEDs 40 in the optical unit 10. In the optical unit 10 in each of the above embodiments, as shown in Fig. 12(A), a photodiode 70 is arranged in the center, and the absorbing LEDs 30 and the reference LEDs 40 are arranged concentrically at equal intervals so that the central angle between the absorbing LEDs 30 and the reference LEDs 40 adjacent to the photodiode 70 is 60 degrees.

[0088] For example, when there is one absorbing LED 30 and two different types of LEDs are used as the reference LEDs 40, the absorbing LED 30 and the reference LED 40 may be arranged concentrically at equal intervals so that the central angle between adjacent absorbing LEDs 30 and reference LEDs 40 is 120 degrees, as shown in Fig. 12(B). When there is one absorbing LED 30 and one reference LED 40, the absorbing LED 30 and the reference LED 40 may be arranged concentrically at equal intervals so that the central angle between adjacent absorbing LEDs 30 and reference LEDs 40 is 180 degrees, as shown in Fig. 12(C).

[0089] Furthermore, in each of the above embodiments, the irradiation directions of the absorbing LED 30 and the reference LED 40 are adjusted by the diaphragm structure 60, but the irradiation directions of the absorbing LED 30 and the reference LED 40 may be adjusted by a configuration other than the diaphragm structure 60. Fig. 13 is a diagram illustrating an example of how the irradiation directions of the absorbing LED 30 and the reference LED 40 are adjusted.

[0090] In each of the above embodiments, as shown in Fig. 13(A), the irradiation directions of the absorbing LED 30 and the reference LED 40 are adjusted by providing an aperture structure 60. In contrast to this, as shown in Fig. 13(B), the irradiation directions of the first irradiation light and the second irradiation light emitted by the absorbing LED 30 and the reference LED 40 may be adjusted by adjusting the angle of the LED holder 23 without providing an aperture structure. Alternatively, as shown in Fig. 13(C), the irradiation directions of the first irradiation light and the second irradiation light may be adjusted by shifting the positions of the absorbing LED 30 and the reference LED 40 with respect to the ball lens 50.

[0091] (Third embodiment) Next, a third embodiment will be described. The moisture content measuring device of the third embodiment includes an optical unit 10 similar to that of the first embodiment, but differs from the first embodiment in that the optical unit 10 is used for measuring the object, e.g., soil, with respect to an orthogonal axis perpendicular to the reflective surface of the object, e.g., soil, with respect to the range of the tilt angle β of the light-receiving optical axis relative to the vertical axis, e.g., the vertical axis. In the first embodiment, the light-receiving optical axis is parallel to an orthogonal axis perpendicular to the reflective surface of the soil, e.g., the vertical axis, on which the first and second irradiation lights irradiated by the absorbing LED 30 and the reference LED 40 are reflected, and the tilt angle β of the light-receiving optical axis relative to the vertical axis is 0 degrees. In contrast, in the third embodiment, the optical unit 10 including the absorbing LED 30, the reference LED 40, and the photodiode 70 is disposed such that the first and second irradiation lights irradiated by the absorbing LED 30 and the reference LED 40 are tilted relative to the vertical axis. The tilt angle β of the light receiving optical axis relative to the vertical axis is set within the range shown in the following formula (2) using the radiation angle θ of the first light emitting unit and the second light emitting unit and the angle φ between the light of the absorption wavelength (first irradiation light) and the light of the reference wavelength (second irradiation light). β≧θ / 2+φ (2)

[0092] Fig. 14 is a diagram showing a state in which the optical unit 10 of the third embodiment emits the first irradiation light B11 and the second irradiation light B12 and receives the reflected light B31. Fig. 14 shows a schematic diagram of the relationship between the first irradiation light B11 and the second irradiation light B12 emitted from the absorption LED 30 and the reference LED 40, respectively, and the light-receiving light axis B22 of the reflected light received by the photodiode 70 in a moisture content measuring device in which the light-receiving light axis B22 of the reflected light of the first irradiation light and the second irradiation light of the moisture measuring device is inclined from the vertical axis VA.

[0093] The reflected light received by the photodiode 70 is, for example, light that is irradiated from the first irradiation light B11 and the second irradiation light B12 and reflected by the soil, and that is included in the light receiving range B21 of the photodiode 70. The vertical axis VA is an axis perpendicular to the surface of the soil G, which is the target object. The tilt angle β of the light receiving optical axis B22 with respect to the vertical axis VA is, for example, the angle formed between the light receiving optical axis B22 of the reflected light B31 and the vertical axis VA.

[0094] The radiation angle θ of the first light-emitting unit and the second light-emitting unit is, for example, the spread angle of the first irradiation light B11 (see FIG. 7) emitted by the absorbing LED 30 and the second irradiation light B12 emitted by the reference LED 40. The angle φ between the first irradiation light and the second irradiation light is, for example, the angle between the first irradiation optical axis B11C, which is the optical axis of the first irradiation light B11 emitted by the absorbing LED 30, and the second irradiation optical axis B12C, which is the optical axis of the second irradiation light B12 emitted by the reference LED 40.

[0095] Fig. 15 is a diagram showing a state in which the first irradiation light B11 and the second irradiation light B12 are reflected by the soil. The upper part of Fig. 15 shows a state in which the first irradiation light B11 and the second irradiation light B12 are reflected by the low-water content soil G1 in the moisture content measuring device of the first embodiment shown in Fig. 7, which is installed so that the light-receiving optical axis B22 (Fig. 14) is horizontal to the vertical axis VA.

[0096] The middle part of Fig. 15 shows the state in which the first irradiation light B11 and the second irradiation light B12 are reflected by the high-water content soil G2 in a moisture content measuring device installed in the same manner as in the state shown in the upper part. The bottom part of Fig. 15 shows the state in which the first irradiation light B11 and the second irradiation light B12 are reflected by the high-water content soil G2 in a moisture content measuring device installed with the light-receiving optical axis B22 of the moisture content measuring device tilted from the vertical direction.

[0097] Low-moisture soil G1 is soil with a low (not high) moisture content (water content), for example, less than 30%. High-moisture soil G2 is soil with a high moisture content (water content), for example, 30% or more. In the following description, light absorbed by moisture in soil with little reflection on the surface is referred to as scattered light RL, and light reflected mainly by moisture contained in the soil is referred to as directly reflected light RS.

[0098] As shown in the upper part of Figure 15, when the first irradiation light B11 and the second irradiation light B12 are irradiated onto low-moisture soil G1, almost no direct reflected light RS is generated. Therefore, the proportion of direct reflected light RS contained in the light reaching the photodiode 70 is low, and the reflected light B31 received by the photodiode 70 contains a large amount of scattered light RL. Therefore, when the first irradiation light B11 and the second irradiation light B12 are irradiated onto the low-moisture soil G1, the reflected light B31 contains a high proportion of scattered light RL. As a result, the moisture content measuring device can improve the measurement accuracy for low-moisture soil G1.

[0099] 15, when the first irradiation light B11 and the second irradiation light B12 are irradiated onto the highly water-rich soil G2, the intensity of the reflected light increases. Therefore, the proportion of the directly reflected light RS contained in the reflected light B31 that reaches the photodiode 70 increases. In this case, when the highly water-rich soil G2 is irradiated with the first irradiation light B11 and the second irradiation light B12, the proportion of the directly reflected light RS component increases in the reflected light B31. As a result, the moisture content measuring device tends to have lower measurement accuracy for the highly water-rich soil G2.

[0100] 15, when the first irradiation light B11 and the second irradiation light B12 are irradiated onto high-water content soil G2 from a moisture content measuring device installed so that the light-receiving optical axis B22 is tilted from the vertical, the directly reflected light RS is mainly directed in a direction different from that of the photodiode 70. As a result, the reflected light B31 that reaches the photodiode 70 contains a low proportion of directly reflected light RS, and the reflected light B31 contains a large amount of scattered light RL. Therefore, a moisture content measuring device installed so that the light-receiving optical axis B22 is tilted from the vertical can improve the measurement accuracy for high-water content soil G2.

[0101] FIG. 16 shows the relationship between soil moisture content and predicted moisture content predicted from the reflectance ratio. FIG. 16 shows the relationship between soil moisture content and predicted moisture content for two types of soil, soil type A and soil type B, the calibration curves for both, and the error between the soil moisture content and predicted moisture content for each soil type. The soil moisture content was measured using any measurement method based on, for example, JIS standards. The predicted moisture content was calculated based on the reflectance ratio of reflected light B31 measured using, for example, the moisture content measuring device of the first embodiment.

[0102] As can be seen from Figure 16, when the soil moisture content is low, for example, below 30%, the predicted moisture content for both soil type A and soil type B roughly follows the linear calibration curve, with errors within a range of approximately ±2%. In contrast, when the soil moisture content increases, for example, above 30%, the predicted moisture content for soil type A and soil type B tends to be lower than the soil moisture content. Furthermore, at a moisture content of 38%, liquefaction begins to occur, water becomes visible on the surface, and the surface water begins to spread, causing surface reflections to disrupt the reflectivity. As a result, the predicted moisture content for soil type A and soil type B deviates significantly from the linear calibration curve, and the error between the soil moisture content and the predicted moisture content for each soil type becomes large, ranging from -5% to -10%.

[0103] The above formula (2) can be derived using the distance l between the light-emitting unit (absorption LED 30, reference LED 40) and the photodiode 70, and the distance z0 from the soil surface to the photodiode 70, as shown in Fig. 14. For example, when variables k and k' are defined by formulas (3) and (4), the tilt angle β must satisfy the following formulas (5) and (6). Formula (5) defines the tilt angle β with respect to the first irradiation light irradiated by the absorption LED 30, and formula (6) defines the tilt angle β with respect to the second irradiation light irradiated by the reference LED 40.

number

[0104] FIG. 17 is a graph in which the vertical axis represents the minimum tilt angle and the horizontal axis represents the distance from the soil surface to the photodiode 70. The graph shown in FIG. 17 is for when θ = 10 degrees and φ = 5 degrees. The minimum tilt angle is the minimum value of tilt angle β at which directly reflected light does not enter the photodiode 70. The first graph GF1 in FIG. 17 is a graph of equation (5) in which the inequality sign is replaced with an equal sign, and the second graph GF2 is a graph of equation (6) in which the inequality sign is replaced with an equal sign. The third graph GF3 is a graph of equation (2) in which the inequality sign is replaced with an equal sign.

[0105] 17, when the relationship between the minimum tilt angle and the distance from the soil surface to the photodiode 70 is in the region above the first graph GF1 and in the region above the second graph GF2, directly reflected light does not enter the photodiode 70. The third graph GF3 is included in this region when the distance from the soil surface to the photodiode 70 exceeds about 40 mm. Therefore, it can be seen that directly reflected light can be prevented from entering the photodiode 70 by satisfying formula (2).

[0106] The tilt angle β can be adjusted, for example, by swinging the optical unit 10 around a horizontal axis. The angle of the optical unit 10 is adjusted by swinging it using an angle adjustment mechanism, for example. The angle adjustment mechanism is provided in the same manner as the roller unit 85 shown in FIG. 12. FIG. 18 is a side view of the roller unit 85 provided with the angle adjustment mechanism 95.

[0107] To further explain the roller unit 85, the roller unit 85 includes, for example, a first frame 86 and a second frame 87 that support a set of rollers 84 arranged front to back. The first frame 86 is provided at approximately the same height as the height at which the rotation axes of the rollers 84 are provided, and the second frame 87 is provided above the first frame 86.

[0108] The first frame 86 has a right frame and a left frame, and an angle adjustment mechanism 95 is provided spanning between the right and left frames. The optical unit 10 is attached to the underside of the angle adjustment mechanism 95. The second frame 87 is disposed in a substantially central position between the right and left frames of the first frame 86 when viewed from above. The second frame 87 is provided with a GNSS device 90.

[0109] The angle adjustment mechanism 95 supports the optical unit 10 so that it can swing about an axis (X axis) along the rotation axis of the roller 84 and about an axis (Y axis) perpendicular to the rotation axis of the roller 84 in a horizontal plane. The angle adjustment mechanism 95 adjusts the tilt of the optical unit 10 (the tilt of the absorption LED 30, the reference LED 40, and the photodiode 70) when the moisture content of the soil, which is the target object, is assumed to be high.

[0110] Whether the soil is expected to have a high moisture content may be determined, for example, by an operator visually, or may be determined based on measurement results from the GNSS device 90 or external factors such as the season, temperature, and weather. The angle adjustment mechanism 95 may be provided with a stopper that fixes the swung optical unit 10 at an arbitrary or predetermined swing angle position.

[0111] The moisture content measuring device of the third embodiment achieves the same effects as the first embodiment. Furthermore, in the moisture content measuring device of the third embodiment, the optical unit 10, which includes the absorbing LED 30, the reference LED 40, and the photodiode 70, is tilted with respect to a vertical axis perpendicular to the soil's reflective surface, and the range of the tilt angle β of the light-receiving optical axis with respect to the perpendicular axis is adjusted to the range expressed by the above formula (2). Therefore, even when the soil has a high moisture content, direct reflected light from the absorbing LED 30 and the reference LED 40 can be prevented from being incident on the photodiode 70. Therefore, the moisture content of the soil can be measured using a high proportion of the scattered light component, thereby improving the moisture content measurement accuracy for highly moist soil.

[0112] (Fourth embodiment) Next, a fourth embodiment will be described. The moisture content measuring device of the fourth embodiment is different from the first embodiment mainly in that it includes a first polarizing plate that polarizes the first irradiation light and the second irradiation light emitted by the absorption LED 30 and the reference LED 40 in the optical unit 10, and a second polarizing plate that polarizes the reflected light B31 received by the photodiode 70.

[0113] 19 is a diagram schematically illustrating a state in which the optical unit 10 of the fourth embodiment emits the first irradiation light and the second irradiation light and receives the reflected light. The optical unit 10 of the fourth embodiment includes a first polarizing plate 51 and a second polarizing plate 52. The first polarizing plate 51 is provided below the absorption LED 30 and the reference LED 40, and the second polarizing plate 52 is provided below the photodiode 70.

[0114] The first polarizing plate 51 passes the first irradiation light B11 emitted by the absorption LED 30 and the second irradiation light B12 emitted by the reference LED 40. The second polarizing plate 52 passes the reflected light B31 that is formed when the first irradiation light B11 and the second irradiation light B12 are reflected by the soil G and enter the photodiode 70. The first polarizing plate 51 polarizes the first irradiation light B11 and the second irradiation light B12 in specific directions. The second polarizing plate 52 polarizes the reflected light B31 by 90 degrees relative to the first irradiation light B11 and the second irradiation light B12.

[0115] FIG. 20 is a schematic diagram illustrating the first and second irradiation lights B11 and B12 reflected by the soil after passing through the first polarizing plate 51. The first and second irradiation lights B11 and B12 are polarized in a first direction by the first polarizing plate 51, for example. The scattered light RL reflected by the soil G and the directly reflected light RS reflected by the moisture on the soil surface are also polarized in the first direction. The reflected light B31 contains both the scattered light RL and the directly reflected light RS. The reflected light B31 passes through the second polarizing plate 52. The second polarizing plate 52 polarizes the reflected light B31 90 degrees relative to the first direction. Therefore, the directly reflected light RS component of the reflected light B31 that passes through the second polarizing plate 52 and reaches the photodiode 70 is attenuated, resulting in a higher proportion of the scattered light RL component. As a result, the moisture content measuring device can improve measurement accuracy for low-moisture soil.

[0116] The above describes the form for carrying out the present invention using an embodiment, but the present invention is not limited to such an embodiment, and various modifications and substitutions can be made within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0117] 1,2 Moisture content measuring device 10 Optical unit 11 Input / Output Interface 20 Holder 21 Base member 22 Retaining member 22A Central holding part 22B1~22B6 Peripheral holding part 23 LED holder 23A central LED holder 23B1~23B6 Peripheral LED holder 30 Absorbing LEDs 31 First absorption LED 32 Second absorption LED 40 Reference LED 41 First Reference LED 42 Second Reference LED 43 Third Reference LED 44 4th Reference LED 50 Ball Lens 60 Aperture structure 70 Photodiode 80 Rotary 81 Rotary body 82,85 Roller unit 83 Parallel link mechanism 84 Laura 86 1st Frame 87 2nd Frame 90 GNSS equipment 95 Angle adjustment mechanism 100 control device 110 Drivers 111~116 1st driver~6th driver 120 Amplification section 130 Conversion Unit 150 Communications Department 160 Control circuit 161 Acquisition Department 162 Drive control unit 163 Calculation Unit 164 Display control unit 170 Storage section 171 Field Map B11 1st irradiation light B11C 1st irradiation optical axis B12 Second irradiation light B12C 2nd irradiation optical axis B21 Light receiving range B22 Receiving optical axis B31 Reflected light CX1,CX2 Moisture content measurable range M1 1st curve M2 2nd curve M3 3rd curve NL Noise Level NS1 1st approximate curve NS2 2nd approximate curve P0 reference position P1 1st position PB intensity ratio PL1 First light intensity PL2 2nd received light intensity R16 1st reference reflected light intensity R19 Absorption / reflection intensity R22 2nd reference reflected light intensity SA11 1st irradiation area SA12 2nd irradiation area SA21 PD light receiving area

Claims

1. a first light-emitting unit that irradiates light with a wavelength absorbed by water; a second light emitting unit that irradiates light of a reference wavelength corresponding to the absorption wavelength of water; a light receiving unit that receives reflected light of light irradiated by the first light emitting unit and the second light emitting unit and reflected by an object; a calculation unit that calculates the moisture content of the object based on the intensity of the reflected light received by the light receiving unit, a half-value angle of the light irradiated by the first light-emitting unit and the second light-emitting unit is 20 degrees or less, and an angle formed by an optical axis of the light irradiated by the first light-emitting unit and the second light-emitting unit and an optical axis of the light received by the light-receiving unit is an angle of 0 to 0.5 times the half-value angle; Moisture content measuring device.

2. The first light-emitting unit and the second light-emitting unit are arranged in a ring shape surrounding the light-receiving unit. The moisture content measuring device according to claim 1.

3. a ball lens configured to condense the light emitted by the first light-emitting unit and the light emitted by the second light-emitting unit, The moisture content measuring device according to claim 1.

4. The light source further includes an aperture structure that adjusts the irradiation range of each of the light emitted by the first light-emitting unit and the second light-emitting unit. The moisture content measuring device according to claim 1.

5. Further provided is a holding unit that holds the distance to the object within a predetermined range. The moisture content measuring device according to claim 1.

6. The holding portion is provided on an agricultural machine. The moisture content measuring device according to claim 5.

7. further comprising a position sensor for detecting the position of the object; The moisture content measuring device according to claim 1.

8. storing, in a storage unit, positional moisture content information that associates the moisture content of the object calculated by the calculation unit with the position of the object detected by the position sensor; The moisture content measuring device according to claim 7.

9. a display control unit that displays the position indicated by the positional moisture content information on map information displayed on a display device; The moisture content measuring device according to claim 8.

10. an optical unit including the first light-emitting unit, the second light-emitting unit, and the light-receiving unit is provided inclined with respect to an orthogonal axis orthogonal to a reflection surface of the object on which the light irradiated by the first light-emitting unit and the second light-emitting unit is reflected, The range of the tilt angle β of the light receiving optical axis with respect to the orthogonal axis is determined by using the radiation angle θ of the first light emitting unit and the second light emitting unit and the angle φ between the light of the absorption wavelength and the light of the reference wavelength, β≧θ / 2+φ represented by The moisture content measuring device according to claim 1.

11. an angle adjustment mechanism for adjusting the inclination of the first light-emitting unit and the second light-emitting unit with respect to the orthogonal axis; The moisture content measuring device according to claim 10.

12. the angle adjustment mechanism adjusts the inclination when the moisture content of the object is expected to be high. The moisture content measuring device according to claim 11.

13. The optical system further includes a first polarizing plate that transmits the light of the absorption wavelength and the light of the reference wavelength, and a second polarizing plate that transmits the reflected light and polarizes the reflected light by 90 degrees relative to the light of the absorption wavelength and the light of the reference wavelength. The moisture content measuring device according to claim 1.

14. The computer calculating the moisture content of the object based on the intensity of reflected light received by a light receiving unit that receives light reflected from the object, the light being irradiated by a first light emitting unit that irradiates light with a wavelength absorbed by water and a second light emitting unit that irradiates light with a reference wavelength corresponding to the absorption wavelength of water; the first light-emitting unit and the second light-emitting unit are disposed at positions where the half-value angles of the light irradiated by the first light-emitting unit and the second light-emitting unit are each 20 degrees or less, and an angle formed between an optical axis of the light irradiated by the first light-emitting unit and the second light-emitting unit, respectively, and an optical axis of the light received by the light-receiving unit is 0 to 0.5 times the half-value angle; Moisture content measurement method.

15. On the computer, calculating the moisture content of the object based on the intensity of reflected light received by a light receiving unit that receives light reflected from the object, the light being irradiated by a first light emitting unit that irradiates light with a wavelength absorbed by water and a second light emitting unit that irradiates light with a reference wavelength corresponding to the absorption wavelength of water; the first light-emitting unit and the second light-emitting unit are disposed at positions where the half-value angles of the light irradiated by the first light-emitting unit and the second light-emitting unit are each 20 degrees or less, and an angle formed between an optical axis of the light irradiated by the first light-emitting unit and the second light-emitting unit, respectively, and an optical axis of the light received by the light-receiving unit is 0 to 0.5 times the half-value angle; program.

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