JP2024044397A - plant sensor - Google Patents

Abstract

[Problem] To provide a plant sensor that reduces the number of parts and costs. [Solution] The plant sensor includes a first light-emitting unit 5 that emits a first measurement light 21 including a first wavelength band at a predetermined spread angle, a second light-emitting unit 6 that emits a second measurement light 25 including a second wavelength band at a predetermined spread angle, at least one light-receiving unit 7 that receives the first reflected measurement light and the second reflected measurement light from the measurement object, wavelength-selecting members 8 and 9 that extract the first wavelength band and the second wavelength band from at least one of the measurement light and the reflected measurement light, and a control unit 11 that calculates the growth status of the measurement object based on the amount of each measurement light and the amount of received reflected measurement light, and the wavelength-selecting members 8 and 9 are configured so that a wavelength-selecting film 28 having a recess that increases in thickness in response to an increase in the angle of incidence of each measurement light 21 and 25 or each reflected measurement light on the wavelength-selecting member is formed on at least one of the entrance surface and exit surface. [Selected Figure] Figure 2

Description

The present invention relates to a plant sensor that irradiates agricultural crops with measuring light and analyzes reflected light to measure the growth status of agricultural crops.

Detecting the growth status of plants, especially agricultural crops, is important in the production management of agricultural crops. Conventionally, plants are irradiated with detection light diffused in one direction, and the growth state of the plants is detected based on the detection light reflected from the leaves of the plants. In this case, the reflected detection light also included reflected detection light from soil other than plant leaves, so the detection results contained noise.

In addition, by shining two detection lights of different wavelengths onto the plant and comparing the amount of light reflected from the plant leaves, noise such as reflected detection light from the soil can be eliminated, improving detection accuracy.

However, in order to irradiate detection light of a specific wavelength, the angle of incidence on the wavelength-selective film, such as a bandpass filter, must be constant, which increases the number of parts and leads to increased costs.

JP 2012-247235 A

The present invention provides a plant sensor that reduces the number of parts and costs.

The present invention relates to a plant sensor having a first light-emitting unit that emits a first measurement light including a first wavelength band at a predetermined spread angle, a second light-emitting unit that emits a second measurement light including a second wavelength band at a predetermined spread angle, at least one light-receiving unit that receives the first reflected measurement light and the second reflected measurement light from the measurement object, a wavelength selection member that extracts the first wavelength band and the second wavelength band from at least one of the measurement light and the reflected measurement light, and a control unit that calculates the growth status of the measurement object based on the amount of each measurement light and the received amount of each reflected measurement light, and the wavelength selection member is configured so that a wavelength selection film having a recess that increases in thickness in response to an increase in the angle of incidence of each measurement light or each reflected measurement light on the wavelength selection member is formed on at least one of the entrance surface and exit surface.

The present invention also relates to a plant sensor in which the film thickness of the recess is set so that the transmitted wavelength is constant or approximately constant regardless of the angle of incidence of each measurement light or each reflected measurement light relative to the recess.

Further, in the present invention, the wavelength selection member is arranged on the optical path of each measurement light so as to be orthogonal to the optical axis of each measurement light, and each measurement light selects each wavelength with the incident angle being rotationally symmetrical. The present invention relates to a plant sensor configured to be incident on a selection member.

Further, the present invention provides a deflection optical member provided on a common optical path of the first light emitting section and the second light emitting section, the deflection optical member transmitting one of the measurement lights transmitted through each wavelength selection member, The present invention relates to a plant sensor configured to deflect the measuring light so that its optical axis coincides with the measuring light that is transmitted through the other side.

Further, the present invention provides a deflection optical member that deflects the optical axis of the first measurement light to match the optical axis of the second measurement light on a common optical path of the first light emission section and the second light emission section. The wavelength selection member is disposed so as to be orthogonal to the optical axis of the second measurement light, and each measurement light is configured to coaxially enter the wavelength selection member with the incident angles being rotationally symmetrical. This relates to a plant sensor.

Further, in the present invention, the wavelength selection member is disposed on the optical path of each reflected measurement light and is arranged perpendicular to the optical axis of each reflected measurement light, and the incident angle of each reflected measurement light is rotationally symmetrical. The present invention relates to a plant sensor configured such that the wavelength is incident on the wavelength selection member.

Furthermore, the present invention includes a first light receiving section that receives the first reflected measurement light, and a second light receiving section that receives the second reflected measurement light, and the wavelength selection member selects a wavelength of each reflected measurement light. A plant sensor arranged on the optical path and perpendicular to the optical axis of each reflected measurement light, and configured such that each reflected measurement light enters each wavelength selection member with the angle of incidence rotationally symmetrical. This is related to.

According to the present invention, a first light-emitting unit that emits a first measurement light including a first wavelength band at a predetermined spread angle, a second light-emitting unit that emits a second measurement light including a second wavelength band at a predetermined spread angle, at least one light-receiving unit that receives the first reflected measurement light and the second reflected measurement light from the measurement object, a wavelength selection member that extracts the first wavelength band and the second wavelength band from at least one of the measurement light and the reflected measurement light, and a control unit that calculates the growth status of the measurement object based on the amount of light of each measurement light and the received amount of each reflected measurement light, and the wavelength selection member is configured to form a wavelength selection film having a recess on at least one of the entrance surface and the exit surface, the film thickness of which increases in response to an increase in the angle of incidence of each measurement light or each reflected measurement light on the wavelength selection member, thereby eliminating the need for an optical system for making each measurement light into a parallel beam, and exhibiting the excellent effect of reducing the number of parts and reducing manufacturing costs.

It is an explanatory view explaining an example of use of a plant sensor concerning a 1st example of the present invention. 1 is a schematic configuration diagram of a plant sensor according to a first example of the present invention. FIG. 2 is a side cross-sectional view illustrating a wavelength selection member according to the first embodiment of the present invention. (A) is a graph illustrating the transmission wavelength for each incident angle in a wavelength selection member with a constant film thickness, and (B) is a graph illustrating the transmission wavelength in the wavelength selection member according to the first embodiment of the present invention. It is a graph explaining the transmission wavelength for each corner. 4 is a graph illustrating a curve showing a gradient of a film thickness from the center to the outer periphery of a recess of the wavelength selection member. FIG. 11 is a schematic configuration diagram of a plant sensor according to a second embodiment of the present invention. FIG. 11 is a schematic configuration diagram of a plant sensor according to a third embodiment of the present invention. It is a schematic block diagram of the plant sensor based on the 4th Example of this invention. FIG. 13 is a schematic configuration diagram of a plant sensor according to a fifth embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows an overview of a plant sensor according to a first embodiment of the present invention.

In FIG. 1, numeral 1 indicates a plant sensor held in the hand of a worker. The plant sensor 1 alternately irradiates a measurement object 3 such as a field (for example, agricultural products) with a laser beam (measuring light 2) of two wavelengths. Further, the plant sensor 1 detects the amount of light received for each wavelength of the measurement light 2 (reflected measurement light 4) reflected by the measurement object 3, and measures the reflectance for each wavelength from each amount of received light.

The plant sensor 1 emits two types of measurement light with different wavelengths, and the two types of measurement light are collectively referred to as the measurement light 2. Similarly, the measurement object 3 reflects two types of reflected measurement light, and the pair of reflected measurement light is collectively referred to as the reflected measurement light 4.

The plant sensor 1 can measure the growth status of the measurement target 3 based on the reflectance of each wavelength at the irradiation position of the measurement light 2.

Here, as an example of the two wavelengths used as the measurement light 2, there are 735 nm as the first measurement wavelength band and 808 nm as the second wavelength band. When using the first measurement light 2a having a wavelength near 735 nm, which is the first wavelength band (wavelength in a predetermined range centered around 735 nm), as the measurement light 2, if the measurement target 3 contains nitrogen, Although reflected by the measurement object 3, the amount of reflected measurement light 4 does not change regardless of the nitrogen content.

On the other hand, when the second measurement light 2b having a wavelength in the second wavelength band around 808 nm (a predetermined range of wavelengths centered around 808 nm) is used as the measurement light 2, it is reflected by the measurement object 3 if the measurement object 3 contains nitrogen, and it is known that the reflectance varies depending on the nitrogen content, and the amount of reflected light increases as the nitrogen content increases.

It is also known that crop leaves contain nitrogen, with high nitrogen content when the growing conditions are good and low nitrogen content when the growing conditions are poor.

Note that, in addition to the measurement target 3, for example soil may also contain nitrogen, but the reflectance of soil and leaves is significantly different (soil has a significantly lower reflectance). Therefore, by comparing only the amount of reflected light, regardless of wavelength, it is possible to determine whether the light is reflected by soil or leaves. Therefore, by removing the reflected measurement light 4 that is determined to be reflected by soil, noise can be removed.

As described above, the measurement light 2 is alternately irradiated with the first measurement light 2a having a wavelength near 735 nm and the second measurement light 2b having a wavelength near 808 nm. That is, the first measurement light 2a and the second measurement light 2b are irradiated on the same or approximately coaxial optical axis and irradiated to the same or approximately the same irradiation range. The reflected light amount of the reflected measurement light 4 is affected by the state of the reflecting surface, such as cleanliness or dirt, and changes. However, since the measurement light 2 of two wavelengths is irradiated to the same point on the reflecting surface, the effect of the state of the reflecting surface on the measurement light 2 of each wavelength is the same.

The amount of received light of the second reflected measurement light 4b having a wavelength of about 808 nm is therefore determined to depend on the amount of nitrogen contained, and the nitrogen content ratio of the measurement target 3 can be determined based on the first reflected measurement light 4a and the second reflected measurement light 4b. If the nitrogen content ratio of the leaves of a crop corresponding to the growth status is obtained in advance, the growth status of the crop of the measurement target 3 can be determined.

The nitrogen content ratio of the measurement target 3 can be expressed as the content ratio S = (R2/R1-1) x 100, where R1 is the reflectance in the first measurement wavelength band (near 735 nm) and R2 is the reflectance in the second measurement wavelength band (near 808 nm).

Note that the plant sensor 1 may have a built-in inclination sensor that detects the inclination of the plant sensor 1. The inclination of the plant sensor 1 with respect to the horizontal (or vertical) can be detected based on the detection result of the inclination sensor.

Figure 2 shows a schematic diagram of the plant sensor 1 according to the first embodiment of the present invention.

The plant sensor 1 includes a first light emitting section 5, a second light emitting section 6, a light receiving section 7, a first wavelength selection member 8, a second wavelength selection member 9, a control section 11, a storage section 12, a display section 13, and an operation section. 14, and each component is housed in a housing 15. Further, a window portion 16 having a predetermined opening area is formed in the housing 15.

The first light emitting section 5 has a first measurement light source 17 and a first light amount sensor 18 . The first measurement light source 17 is an LED light source, and the first measurement light source 17 is a first measurement light source having a first wavelength band, that is, a predetermined wavelength range including a wavelength around 735 nm, on the first projection optical axis 19 at a predetermined spread angle, for example, ±25°. It is configured to irradiate light 21. Further, the first light amount sensor 18 is, for example, a photodiode (PD), and receives a part of the first measurement light 21 emitted from the first measurement light source 17, and detects the amount of light emitted from the first measurement light source 17. is configured so that it can be detected in real time. The amount of light detected by the first light amount sensor 18 is transmitted to the controller 11 in real time.

The second light-emitting unit 6 has a second measurement light source 22 and a second light quantity sensor 23. The second measurement light source 22 is an LED light source, and is configured to irradiate a second wavelength band, i.e., a second measurement light 25 of a predetermined wavelength range including a wavelength near 808 nm, on a second light projection optical axis 24 at a predetermined spread angle, for example, ±25°. The second light quantity sensor 23 is, for example, a photodiode (PD), and is configured to receive a part of the second measurement light 25 emitted from the second measurement light source 22 and detect the amount of light emitted by the second measurement light source 22 in real time. The amount of light detected by the second light quantity sensor 23 is transmitted to the control unit 11 in real time.

The light receiving section 7 is a light receiving element provided on the light receiving optical axis 26, such as a photodiode (PD) or an avalanche photodiode (APD). Further, the light receiving section 7 is capable of detecting the amounts of the first reflected measuring light 4a and the second reflected measuring light 4b that are incident along the light receiving optical axis 26, respectively. The amounts of the first reflected measurement light 4a and the second reflected measurement light 4b detected by the light receiving section 7 are each transmitted to the control section 11 in real time as received light amount data.

The first wavelength selection member 8 is disposed on the optical path of the first measurement light 21 so as to be perpendicular to the first light projection optical axis 19, and is configured so that all of the first measurement light 21 is incident on the first wavelength selection member 8. That is, the angle of incidence of the first measurement light 21 with respect to the first wavelength selection member 8 is rotationally symmetric. The first wavelength selection member 8 also has, for example, a bandpass filter, and has optical properties that transmit light with a wavelength near 735 nm and block light with other wavelengths.

The second wavelength selection member 9 is disposed on the optical path of the second measurement light 25 so as to be orthogonal to the second light projection optical axis 24, and all of the second measurement light 25 is directed to the second wavelength selection member. 9. That is, the angle of incidence of the second measurement light 25 on the second wavelength selection member 9 is rotationally symmetrical. Further, the second wavelength selection member 9 includes, for example, a bandpass filter, and has an optical property of transmitting light with a wavelength around 808 nm and blocking light with other wavelengths.

The control unit 11 executes various programs stored in the storage unit 12, which will be described later. Thereby, the control section 11 controls the light emission of the first measurement light source 17 and the second measurement light source 22, and also controls the reflected measurement light 4 received by the light receiving section 7 (the first reflected measurement light 4a). , controls the process of measuring the growth condition of the measurement object 3 based on the second reflected measurement light 4b).

The storage unit 12 stores a sequence for activating the first measurement light source 17 and the second measurement light source 22 to alternately irradiate the measurement object 3 with the first measurement light 2a and the second measurement light 2b. program, a determination program for determining the growth state of the measurement target 3 based on the received light amount data, a noise removal program for removing noise data from the received light amount data, fertilizer according to the growth state of the measurement target 3 A calculation program, etc. for calculating the amount of spraying is stored. Further, the noise removal program includes thresholds necessary for noise determination, such as thresholds related to the amount of received light. Further, the storage unit 12 stores the nitrogen content ratio of leaves corresponding to the growth status of the measurement target 3, which is an agricultural product, and also stores the ratio of the first measurement light 2a in the first measurement light 21. and the ratio of the second measurement light 2b in the second measurement light 25 are stored.

FIG. 3 shows the first wavelength selection member 8. As shown in FIG. Note that since the first wavelength selection member 8 and the second wavelength selection member 9 have the same configuration, the first wavelength selection member 8 will be described below, and the description of the second wavelength selection member 9 will be explained below. omitted.

The first wavelength selection member 8 includes a disk-shaped glass plate 27 and a wavelength selection film 28 formed on both the incident surface and the exit surface of the glass plate 27. The first wavelength selection member 8 has a radius of, for example, 15 mm, and the beam of the first measurement light 21 when the first measurement light 21 is irradiated to the first wavelength selection member 8 with a spread angle of ±25°. The first wavelength selection member 8 is arranged so that its diameter (effective diameter) is 13 mm.

Figure 4 (B) is a graph showing the optical characteristics of the wavelength selection film 28 according to the first embodiment of the present invention. The wavelength selection film 28 is a bandpass filter that selects and transmits wavelengths around 735 nm.

Here, it is known that the transmitted wavelength of a band-pass filter shifts depending on the angle of incidence on the band-pass filter. For example, as shown in FIG. 4(A), when the thickness of the wavelength selection film 28 is constant from the center to the outer periphery, there is a case where the first measurement light 21 is incident at an incident angle of 0°; The transmitted wavelength is different from the case where the first measurement light 21 is incident at an angle of 25°. In other words, the wavelength selective film 28 has a shorter transmission wavelength when the incident angle is 25° (dashed line in FIG. 4(A)) than when the incident angle is 0° (solid line in FIG. 4(A)). It shifts to the side by about 17 nm.

On the other hand, it has also been found that increasing the thickness of the wavelength selection film 28 shifts the transmitted wavelength to the longer wavelength side.

Therefore, in the first embodiment, the thickness of the wavelength selection film 28 is increased in response to an increase in the incident angle of the first measurement light 21, and the thickness of the wavelength selection film 28 is set so that the transmitted wavelength is constant or approximately constant regardless of the incident angle of the first measurement light 21. Note that in FIG. 4(B), for convenience, the wavy line (for an incident angle of 25°) is shifted slightly toward the short wavelength side compared to the solid line (for an incident angle of 0°), but in reality the solid line and the wavy line match or approximately match.

As shown in FIGS. 3 and 5, the wavelength selection film 28 is centered around the first light projection optical axis 19, and has a small film thickness toward the center and increases in film thickness concentrically toward the outer circumference. A recess 29 having a bowl-shaped concave curved surface is formed. The outer diameter of the recess 29 matches or is slightly larger than the diameter of the light beam when the first measurement light 21 enters the wavelength selection film 28 and exits from the wavelength selection film 28. . That is, the recess 29 of the wavelength selection film 28 on the incident side has a smaller outer diameter than the recess 29 of the wavelength selection film 28 on the exit side.

The luminous flux diameter of the first measurement light 21 is taken as an effective diameter, and the effective diameter is normalized to r=1, and the center of the recess 29 (r=0), that is, the recess 29 on the first light projection optical axis 19 (the When the wavelength selective film 28) is standardized to have a film thickness t=1, the recess 29 has a film thickness t=1 when the effective diameter r=0, and a film thickness t=1 when the effective diameter r=1. It is configured so that it becomes .025. That is, the recessed portion 29 is configured such that the film thickness at the outer periphery is 2.5% thicker than the film thickness at the center.

Figure 5 is a graph showing the relationship between the radial position of the recess 29 and the film thickness. Curve 31 in Figure 5 is a curve showing the gradient of the film thickness of the recess 29, and is configured so that the film thickness gradually increases concentrically from the center to the outer periphery, and forms a downward convex curve.

The shape of the curve 31 varies depending on the spread angle of the first measurement light 21, the maximum angle of incidence on the wavelength selection film 28, and the effective diameter. On the other hand, the shape of the curve 31 is always a downward convex curve with respect to a straight line connecting the center and the outer periphery of the wavelength selection film 28. The curve 31 can be defined, for example, as a polynomial of degree two or lower.

In addition, since the effective diameter of the first measuring light 21 differs between the entrance surface and the exit surface of the first wavelength selection member 8, the shape of the curve 31 differs between the recess 29 on the entrance side and the recess 29 on the exit side.

Note that, like the first wavelength selection member 8, the second wavelength selection member 9 is also provided with a wavelength selection film 32 and a recess 33. The wavelength selection film 32 is a bandpass filter that selectively transmits light having a wavelength around 808 nm. The wavelength selection film 32 and the recess 33 have the same configuration as the wavelength selection film 28 and the recess 29 except for the transmission wavelength.

The display section 13 displays the measurement result of the measurement object 3, that is, the nitrogen content ratio of the measurement object 3 in the range irradiated with the measurement light 2. For example, the information is displayed in different colors depending on the nitrogen content ratio. Alternatively, the amount of fertilizer applied to the measurement object 3 is displayed based on the measurement results.

The operation unit 14 is capable of starting and stopping measurement of the measurement target 3. By configuring the display unit 13 as a touch panel, the display unit 13 can be used as the operation unit 14. In this case, the operation unit 14 can be omitted.

Next, a case will be described in which the growth status of the measurement target 3 is measured by the plant sensor 1.

When a start of measurement is input via the operation unit 14 while the plant sensor 1 is being held by the operator, the control unit 11 controls the first measurement light source 17 and the second measurement light source 22. The first measurement light 21 and the second measurement light 25 are alternately emitted in pulses.

The first measurement light 21 enters the first wavelength selection member 8 while being diffused on the first projection optical axis 19 at a predetermined spread angle. Further, the light intensity of the first measurement light 21 is detected in real time by the first light intensity sensor 18, and the detection result is output to the control section 11.

The first wavelength selection member 8 transmits only the first measurement light 2a having a wavelength in a first wavelength band, that is, around 735 nm, and blocks the first measurement light 21 having other wavelengths.

The first measurement light 2 a that has passed through the first wavelength selection member 8 is irradiated onto the measurement object 3 through the window 16 . At this time, since the thickness of the wavelength selection film 28 changes depending on the angle of incidence of the first measurement light 2a, regardless of the angle of incidence with respect to the wavelength selection film 28, Only the first measurement light 2a passes through the wavelength selection film 28.

Note that the distance from the plant sensor 1 to the measurement object 3 is selected, for example, in the range of 50 cm to 5 m. Further, the irradiation area of the measurement light 2 on the measurement object 3 is, for example, φ30 cm when the distance to the measurement object 3 is 1 m.

The first measurement light 2a is reflected at a predetermined reflectance based on the nitrogen content ratio of the measurement target 3, and the first reflected measurement light 4a is received by the light receiving unit 7 through the window 16. The light receiving unit 7 outputs the amount of the first reflected measurement light 4a received to the control unit 11.

Similarly, the second measurement light 25 is incident on the second wavelength selection member 9 while diffusing at a predetermined spread angle on the second light projection optical axis 24. The amount of light of the second measurement light 25 is detected in real time by the second light amount sensor 23, and the detection result is output to the control unit 11.

The second wavelength selection member 9 transmits only the second measurement light 2b having a wavelength in a second wavelength band, that is, around 808 nm, and blocks the second measurement light 25 having other wavelengths.

The second measurement light 2b transmitted through the second wavelength selection member 9 is irradiated onto the measurement object 3 through the window portion 16. At this time, since the thickness of the wavelength selection film 32 changes depending on the angle of incidence of the second measurement light 2b, the wavelength selection film 32 has a thickness that varies depending on the angle of incidence of the second measurement light 2b. Only the second measurement light 2b is transmitted through the wavelength selection film 32.

The second measurement light 2b is reflected at a predetermined reflectance based on the nitrogen content ratio of the measurement object 3, and the second reflected measurement light 4b is received by the light receiving section 7 through the window section 16. . The light receiving section 7 outputs the received amount of the second reflected measurement light 4b to the control section 11.

Therefore, the light receiving unit 7 alternately receives the first reflected measurement light 4a and the second reflected measurement light 4b, and alternately sends each received light amount data to the control unit 11.

The control unit 11 calculates the nitrogen content ratio of the measurement target 3 based on the amount of light of the first measurement light 21 input from the first light amount sensor 18, the amount of light of the second measurement light 25 input from the second light amount sensor 23, the proportion of the first measurement light 2a in the first measurement light 21, the proportion of the second measurement light 2b in the second measurement light 25, and the received amounts of the first reflected measurement light 4a and the second reflected measurement light 4b input from the light receiving unit 7.

Further, the control unit 11 compares the nitrogen content ratio of the leaves of the measurement target 3 corresponding to the growth status obtained in advance with the calculated content ratio, and determines the growth status of the measurement target 3 based on the comparison result. At the same time, the growth status is displayed on the display section 13. Further, the control unit 11 calculates the amount of fertilizer required for the measurement target 3 based on the content ratio, and displays the calculation result on the display unit 13.

When the measurement is completed, the measurement position is changed, and the measurement light is irradiated onto the measurement object 3 again to perform the measurement. The above process is repeated until the measurement of the entire desired measurement range is completed.

As described above, in the first embodiment, the wavelength selection film 28 of the first wavelength selection member 8 and the wavelength selection film 32 of the second wavelength selection member 9 It is configured to increase the film thickness in response to an increase in the incident angle of the second measurement light 25.

Therefore, it is possible to prevent a shift in the transmitted wavelength due to a change in the angle of incidence, so that the wavelength selection film 28 and the wavelength selection film 32 transmit the first measurement light 21 and the second measurement light 25 regardless of the angle of incidence. The wavelengths of the first measurement light 2a and the second measurement light 2b can be made constant.

In addition, since the transmission wavelength is constant, a bandpass filter with a narrow range of transmission wavelengths can be used, so that the light amount of the first measurement light 2a and the second measurement light 2b can be sufficiently secured, and the loss of the light amount of the first measurement light 21 and the second measurement light 25 can be suppressed. In addition, by using a narrow range of measurement light centered on the first wavelength band and the second wavelength band, the measurement accuracy can be improved.

Furthermore, since it is not necessary to make the incident angle of the first measurement light 21 on the wavelength selection film 28 and the incidence angle of the second measurement light 25 on the wavelength selection film 32 the same, the first measurement light 21 and the second measurement light 21 do not need to be aligned. A lens for converting the measurement light 25 into a parallel light beam is not required, and the number of parts and size can be reduced, and manufacturing costs can be reduced.

In the first embodiment, the plant sensor 1 is made portable, and the operator points the plant sensor 1 directly at the measurement target 3 to measure the growth status of the measurement target 3. On the other hand, the plant sensor 1 may be mounted on a moving body such as a tractor or a UAV, and the growth status of the measurement target 3 may be measured by remote control.

In this case, a map of the growth status of the measurement object 3 can be created by providing a position measuring device such as a GNSS device on the moving body and acquiring the measurement position when the measurement object 3 is measured. Measurement can be performed even when the measurement target 3 exists over a wide range.

The transmission wavelengths of the wavelength selection film 28 and the wavelength selection film 32 also change depending on the temperature. Therefore, by controlling the light emission of the first measurement light source 17 and the second measurement light source 22, the shift in the transmission wavelength caused by the temperature of the first measurement light source 17 and the second measurement light source 22 can be suppressed, and the measurement accuracy can be improved.

In addition, a temperature sensor capable of detecting the temperatures of the first measurement light source 17 and the second measurement light source 22 and the air temperature outside the plant sensor 1 may be provided, and the amount of shift in the transmitted wavelength may be calculated based on the detection result of the temperature sensor, and the measurement result may be corrected based on the calculated amount of shift.

Further, in the first embodiment, the first wavelength selection member 8 is formed by the glass plate 27 and the wavelength selection film 28 provided on both the incident surface and the exit surface of the glass plate 27. On the other hand, the first wavelength selection member 8 may be formed by the glass plate 27 and the wavelength selection film 28 provided on either the entrance surface or the exit surface of the glass plate 27. Similarly, the second wavelength selection member 9 may be formed by providing the wavelength selection film 32 on either the entrance surface or the exit surface of a glass plate (not shown). good.

The window 16 may be made of a material that absorbs external light, such as colored glass that absorbs wavelengths in the visible range, or a reflective film may be vapor-deposited onto the window 16. This can prevent external light from entering the light receiving unit 7, improving measurement accuracy.

In the first embodiment, the first light amount sensor 18 is provided near the first measurement light source 17, and the second light amount sensor 23 is provided near the second measurement light source 22. However, the first measurement light 2a and the second measurement light 2b may be irradiated onto a target having retroreflective or diffuse reflective properties, and the amount of light received by the first reflected measurement light 4a and the second reflected measurement light 4b at that time may be obtained in advance. In this case, the first light amount sensor 18 and the second light amount sensor 23 may be omitted.

In the first embodiment, the first measuring light 2a and the second measuring light 2b, and the first reflected measuring light 4a and the second reflected measuring light 4b all pass through the window 16. On the other hand, the window through which the first measuring light 2a and the second measuring light 2b pass and the window through which the first reflected measuring light 4a and the second reflected measuring light 4b pass may be separate members. By separating the windows, it is possible to prevent the first measuring light 2a and the second measuring light 2b (stray light) reflected by the windows from being received by the light receiving unit 7, thereby improving the measurement accuracy.

Next, a second embodiment of the present invention will be described with reference to FIG. 6. In FIG. 6, the same reference numerals are used to designate the same parts as in FIG. 2, and their description will be omitted.

In the second embodiment, the first light-emitting unit 5 and the second light-emitting unit 6 are provided so that the first light-projecting optical axis 19 and the second light-projecting optical axis 24 are perpendicular to each other. In addition, a deflection optical member 35 is provided at the intersection of the first light-projecting optical axis 19 and the second light-projecting optical axis 24, on the common optical path of the first light-emitting unit 5 and the second light-emitting unit 6.

A first wavelength selection member 8 is disposed between the first light-emitting unit 5 and the deflection optical member 35, and the first measurement light 21 is configured to be incident on the first wavelength selection member 8 with an incident angle that is rotationally symmetric. A second wavelength selection member 9 is disposed between the second light-emitting unit 6 and the deflection optical member 35, and the second measurement light 25 emitted alternately with the first measurement light 21 is configured to be incident on the second wavelength selection member 9 with an incident angle that is rotationally symmetric.

The deflection optical member 35 is, for example, a glass plate provided with a dichroic filter on its surface, and has an optical property of transmitting light in the second wavelength band, that is, a wavelength around 808 nm, and reflecting light of other wavelengths. are doing.

The deflection optical member 35 may have optical properties that transmit light in the first wavelength band, i.e., wavelengths around 735 nm, and reflect light of other wavelengths. That is, the first light-emitting unit 5 may be disposed on the transmission side of the deflection optical member 35, and the second light-emitting unit 6 may be disposed on the reflection side of the deflection optical member 35.

Therefore, the second measurement light 2b emitted from the second measurement light source 22 and transmitted through the second wavelength selection member 9 passes through the deflection optical member 35. Also, the first measurement light 2a emitted from the first measurement light source 17 and transmitted through the first wavelength selection member 8 is deflected at a right angle by the deflection optical member 35 so that the first light projection optical axis 19 and the second light projection optical axis 24 coincide with each other.

In the second embodiment, the first measuring light 21 including the first wavelength band is irradiated toward the measurement object 3 (see FIG. 1), and only the first measuring light 2a consisting of the first wavelength band is extracted during the process of passing through the first wavelength selection member 8, i.e., the recess 29, and is reflected by the deflection optical member 35, and then irradiated to the measurement object 3 through the window portion 16.

In addition, the second measurement light 25 including the second wavelength band irradiated toward the measurement object 3 is extracted as it passes through the second wavelength selection member 9, i.e., the recess 33, and after passing through the deflection optical member 35, it is irradiated to the measurement object 3 through the window portion 16.

The first reflected measuring light 4a and the second reflected measuring light 4b reflected by the measurement object 3 are alternately received by the light receiving section 7 through the window section 16. The processing after receiving the first reflected measurement light 4a and the second reflected measurement light 4b is the same as in the first embodiment.

In the second embodiment, the deflection optical member 35 is provided on the common optical path of the first light-emitting unit 5 and the second light-emitting unit 6, and the first measurement light 2a is deflected so that the first light-projecting optical axis 19 and the second light-projecting optical axis 24 coincide with each other.

Therefore, compared to the case where the first measurement light 2a and the second measurement light 2b are irradiated in parallel, the window portion 16 can be made smaller, so the size of the plant sensor 1 can be reduced. Can be done.

Next, a third embodiment of the present invention will be described with reference to FIG. Components in FIG. 7 that are the same as those in FIG. 6 are given the same reference numerals, and their explanations will be omitted.

In the third embodiment, a wavelength selection member 36 is arranged between the deflection optical member 35 and the window 16 so as to be orthogonal to the first light projection optical axis 19 and the second light projection optical axis 24. That is, the first measurement light 21 and the second measurement light 25 enter the wavelength selection member 36 with their incident angles being rotationally symmetrical.

In the third embodiment, the wavelength selection member 36 has a wavelength selection film 37 on at least one of the entrance surface and the exit surface. The wavelength selection film 37 is, for example, a dual pass filter, and has optical properties that select and transmit light in the first wavelength band, i.e., light with a wavelength around 735 nm, and light in the second wavelength band, i.e., light with a wavelength around 808 nm.

Further, the wavelength selection film 37 has a film thickness centered around the first light projection optical axis 19 and the second light projection optical axis 24, the film thickness being small on the center side and increasing in film thickness concentrically toward the outer circumference. A recess 38 having a bowl-shaped concave curved surface is formed. The recess 38 has a size such that the first measurement light 2a reflected by the deflection optical member 35 and the second measurement light 2b transmitted through the deflection optical member 35 can all enter.

In the third embodiment, the first measuring light 21 and the second measuring light 25 are alternately irradiated. The first measuring light 21 including the first wavelength band irradiated toward the measurement object 3 (see FIG. 1) is reflected by the deflection optical member 35, and then only the first measuring light 2a consisting of the first wavelength band is extracted in the process of passing through the wavelength selection member 36, i.e., the recess 38, and is irradiated to the measurement object 3 through the window portion 16.

The second measurement light 25 including the second wavelength band irradiated toward the measurement object 3 passes through the deflection optical member 35, and then passes through the wavelength selection member 36, i.e., the recess 38, where only the second measurement light 2b consisting of the second wavelength band is extracted and irradiated to the measurement object 3 through the window portion 16.

The first reflected measurement light 4a and the second reflected measurement light 4b reflected by the measurement object 3 are alternately received by the light receiving unit 7 through the window 16. The processing after receiving the first reflected measurement light 4a and the second reflected measurement light 4b is the same as in the first embodiment.

In the third embodiment, a common wavelength selection member 36 is provided for the first measurement light 21 and the second measurement light 25.

Therefore, there is no need to provide a wavelength selection member for each measurement light, which reduces the number of parts.

Next, referring to FIG. 8, a fourth embodiment of the present invention will be described. In FIG. 8, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In the fourth embodiment, the wavelength selection member 39 is located not on the optical path of the first measurement light 21 or the second measurement light 25, but on the optical path of the first reflected measurement light 41 and the second reflected measurement light 42, so that the wavelength selection member 39 is located on the light receiving optical axis. 26. That is, the first reflected measurement light 41 and the second reflected measurement light 42 enter the wavelength selection member 39 with their incident angles being rotationally symmetrical. Further, the wavelength selection member 39 has a dual-pass filter that extracts light in a first wavelength band (near 735 nm) and light in a second wavelength band (near 808 nm).

In the fourth embodiment, a first measuring light 21 having a wavelength in a first wavelength band and a second measuring light 25 having a wavelength in a second wavelength band are irradiated toward the measurement object 3 (see FIG. 1) and are alternately irradiated to the measurement object 3 through the window portion 16 while maintaining the wavelength band and light amount.

The first reflected measurement light 41 and the second reflected measurement light 42 reflected by the measurement target 3 are incident on the wavelength selection member 39 through the window portion 16. The wavelength selection member 39 is provided with a wavelength selection film 43 having a recess 44 whose film thickness changes according to the incidence angle of the first reflected measurement light 41 and the second reflected measurement light 42, as in the first to third embodiments.

When the first reflected measurement light 41 passes through the recess 44, only the first reflected measurement light 4a consisting of the first wavelength band is extracted, and when the second reflected measurement light 42 passes through the recess 44, only the second reflected measurement light 4b consisting of the second wavelength band is extracted.

After passing through the recess 44, the first reflected measurement light 4a and the second reflected measurement light 4b are alternately received by the light receiving section 7. The processing after receiving the first reflected measurement light 4a and the second reflected measurement light 4b is the same as in the first embodiment.

In the fourth embodiment, the wavelength selection member 39 is provided on the optical path of the first reflected measurement light 41 and the second reflected measurement light 42, and the wavelength selection member 39 is provided on the optical path of the first reflected measurement light 41 and the second reflected measurement light 42, and It is configured such that only the second measurement light 2b in two wavelength bands is incident on the light receiving section 7.

Therefore, it is possible to suppress external light from entering the light receiving section 7 together with the first reflected measuring light 4a and the second reflected measuring light 4b, and it is possible to improve measurement accuracy.

Furthermore, the concave portion 44 formed in the wavelength selection film 43 makes it possible to suppress a shift in the transmission wavelength of the wavelength selection film 43 based on the incident angle. Therefore, a sufficient amount of light can be obtained even when the transmission wavelength of the wavelength selection film 43 is in a narrow band, so that the effect of suppressing the reception of external light can be further enhanced, and the measurement accuracy can be further improved.

Furthermore, since only one wavelength selection member 39 needs to be provided on the optical path of the reflected measurement light 4, the wavelength selection member 39 can be made smaller, the number of parts can be reduced, and manufacturing costs can be reduced. Can be done.

Next, referring to FIG. 9, a fifth embodiment of the present invention will be described. In FIG. 9, the same parts as those in FIG. 8 are given the same reference numerals, and their explanations will be omitted.

In the fifth embodiment, a first light receiving unit 45 for receiving the first reflected measurement light 4a is provided in correspondence with a first light emitting unit 5 for irradiating the first measurement light 21, and a second light receiving unit 46 for receiving the second reflected measurement light 4b is provided in correspondence with a second light emitting unit 6 for irradiating the second measurement light 25. That is, the same number of light receiving units as the number of light emitting units are provided.

Further, the first wavelength selection member 47 is disposed on the optical path of the first reflected measurement light 41 so as to be orthogonal to the first light receiving optical axis 49, and selects the first reflected measurement light 4a having a first wavelength band from the first reflected measurement light 4a. It has a bandpass filter that extracts from one reflected measurement light 41. The first reflected measurement light 41 enters the first wavelength selection member 47 with the angle of incidence being rotationally symmetrical.

The second wavelength selection member 48 is disposed on the optical path of the second reflected measurement light 42 so as to be orthogonal to the second light receiving optical axis 51, and the second wavelength selection member 48 selects the second reflected measurement light 4b having a second wavelength band from the second reflected measurement light 42. It has a bandpass filter that extracts the measurement light 42. The second reflected measurement light 42 enters the second wavelength selection member 48 with the angle of incidence being rotationally symmetrical.

In the fifth embodiment, a first measuring light 21 having a wavelength in a first wavelength band and a second measuring light 25 having a wavelength in a second wavelength band are irradiated toward the measurement object 3 (see FIG. 1) simultaneously through the window portion 16 to the measurement object 3 while maintaining the wavelength band and light amount.

The first reflected measurement light 41 reflected by the measurement object 3 is incident on the first wavelength selection member 47 through the window portion 16, and the second reflected measurement light 42 is incident on the second wavelength selection member 48 through the window portion 16.

Similar to the first to fourth embodiments, the first wavelength selection member 47 has a recess 52 whose film thickness increases in accordance with an increase in the incident angle of the first reflected measurement light 41. A wavelength selection film 53 is provided, and the second wavelength selection member 48 is provided with a wavelength selection film 55 having a recess 54 whose film thickness increases in response to an increase in the incident angle of the second reflected measurement light 42. ing.

While the first reflected measuring light 41 passes through the recess 52, the first reflected measuring light 4a is extracted and received by the first light receiving section 45. Further, while the second reflected measuring light 42 passes through the recess 54, the second reflected measuring light 4b is extracted and received by the second light receiving section 46 at the same time as the first reflected measuring light 4a. The processing after receiving the first reflected measurement light 4a and the second reflected measurement light 4b is the same as in the first embodiment.

In the fifth embodiment, the first measurement light 21 and the second measurement light 25 can be emitted simultaneously, and the first reflected measurement light 4a and the second reflected measurement light 4b can be received simultaneously. ing.

Therefore, measurement errors due to positional misalignment between the irradiation position of the first measuring light 21 and the irradiation position of the second measuring light 25 can be prevented, and measurement accuracy can be further improved.

1 Plant sensor 2 Measurement light 3 Measurement object 4 Reflected measurement light 5 First light emitting section 6 Second light emitting section 7 Light receiving section 8 First wavelength selection member 9 Second wavelength selection member 21 First measurement light 25 Second measurement light 28 Wavelength Selective film 29 Recess 35 Deflection optical member 41 First reflected measurement light 42 Second reflected measurement light

Claims (7)

A plant sensor comprising a first light-emitting unit that emits a first measurement light including a first wavelength band at a predetermined spread angle, a second light-emitting unit that emits a second measurement light including a second wavelength band at a predetermined spread angle, at least one light-receiving unit that receives the first reflected measurement light and the second reflected measurement light from the measurement object, a wavelength selection member that extracts the first wavelength band and the second wavelength band from at least one of the measurement light and the reflected measurement light, and a control unit that calculates the growth status of the measurement object based on the amount of each measurement light and the received amount of each reflected measurement light, and the wavelength selection member is configured so that a wavelength selection film having a recess that increases in thickness in response to an increase in the angle of incidence of each measurement light or each reflected measurement light on the wavelength selection member is formed on at least one of the entrance surface and exit surface. 2. The plant sensor according to claim 1, wherein the film thickness of the recess is set so that the transmitted wavelength is constant or substantially constant regardless of the incident angle of each measurement light or each reflected measurement light with respect to the recess. The plant sensor according to claim 1 or 2, wherein the wavelength selection members are arranged on the optical paths of the respective measurement lights so as to be perpendicular to the optical axes of the respective measurement lights, and the respective measurement lights are configured to be incident on the respective wavelength selection members with rotationally symmetric angles of incidence. The plant sensor according to claim 3, wherein a deflection optical member is provided on a common optical path of the first light-emitting unit and the second light-emitting unit, and the deflection optical member is configured to transmit one of the measurement lights transmitted through each wavelength selection member and to deflect the other of the measurement lights so that the optical axis coincides with the measurement light transmitted through the other wavelength selection member. The plant sensor according to claim 1 or 2, wherein a deflection optical member that deflects the optical axis of the first measurement light so as to coincide with the optical axis of the second measurement light is provided on a common optical path between the first light-emitting unit and the second light-emitting unit, the wavelength selection member is disposed so as to be perpendicular to the optical axis of the second measurement light, and each measurement light is configured to be coaxially incident on the wavelength selection member with its incident angle rotationally symmetrical. The wavelength selection member is located on the optical path of each reflected measurement light and is arranged perpendicular to the optical axis of each reflected measurement light, and the wavelength selection member is arranged so that the incident angle of each reflected measurement light is rotationally symmetrical. 3. The plant sensor according to claim 1, wherein the plant sensor is configured to be incident on the plant sensor. The plant sensor according to claim 1 or 2, which has a first light receiving section that receives the first reflected measurement light and a second light receiving section that receives the second reflected measurement light, and the wavelength selection members are arranged on the optical paths of the reflected measurement lights and perpendicular to the optical axes of the reflected measurement lights, and each reflected measurement light is incident on each wavelength selection member with an incident angle that is rotationally symmetric.

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