JPH1183628A - Device for measuring optical characteristic of soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for measuring optical characteristic of soil by which the optical characteristic of soil can be measured accurately without the influence of such as shape or structure of soil, quality of soil or irregularity of soil surface. SOLUTION: A white light emitting from a light source 27 is divided by a spectrometer 29 and a measuring light having a specific wavelength is given to soil surface 3 from the inside of an optical integrating sphere 23. The measuring light scattered and reflected by the soil surface 3 is collected in a scattering/ reflecting sphere 23 of spherical shell type where its inner surface has a reflectance of about 100%, and the averaged scattering/reflecting light is received by an optical detector 24 mounted on the inside of the optical integrating sphere 23. The measuring light is scanned in wavelength by a spectrometer 29 and a data processor 25 judges the soil composition on the basis of the optical spectrum of the reflected scattering light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring optical properties of soil. In particular, the present invention relates to an optical property measuring device for measuring optical properties of soil and analyzing components of the soil.

[0002]

2. Description of the Related Art In order to increase the yield of agricultural products, it is necessary to replenish the shortage of organic components and fertilizers in the soil and to homogenize the soil of the whole cultivated land. For that purpose, it is necessary to analyze the components of the soil, and it is particularly desirable to analyze the components in real time.

FIG. 1 shows a known soil component analyzer for this purpose (Soil Organic Mat).
ter, CEC, and Moisture Sensing with a Portable NIR
Spectrophotometer; KA Sudduth, JW Hummel: T
ransactions of the ASAE, 1993 Vol. 36, 1571-158
2). The soil component analyzer 1 includes a plow 2 at the rear of the tractor.
The soil component analyzer 1 is pulled by a tractor to move in the field, and the new soil surface 3 exposed by the plow 2 is analyzed by the soil component analyzer 1 to determine the organic matter content in the soil. And water and the like.

In the soil component analyzer 1, white light emitted from a light source 4 is condensed on one end face of a bundle optical fiber 6 by a condenser lens 5. At this time, the white light condensed by the condensing lens 5 passes through the slit plate 7 and the wavelength selection filter 8 and enters the end face of the bundle optical fiber 6. The wavelength selection filter 8 is provided in the fan-shaped opening 10 of the disk-shaped filter disk 9 as shown in FIG. 2, and the selected wavelength (transmission wavelength) continuously changes along the circumferential direction of the filter disk 9. It is arranged to change. The filter disk 9 is driven to rotate by a rotation motor 11. Since the opening 12 of the slit plate 7 is elongated along the radial direction of the filter disk 9, when the filter disk 9 is rotating, it passes through the slit plate 7 and the wavelength selection filter 8 and passes through the bundle optical fiber 6. The wavelength of the monochromatic measurement light incident on the end face changes continuously. The wavelength selected by the wavelength selection filter 8 is 400
In many cases, ultraviolet light to near-infrared light in the range of ２2500 nm is used. The rotation of the filter disk 9 by the rotation motor 11 is controlled by the motor control unit 13, and the motor control signal is transmitted from the motor control unit 13 to the data processing device 1.
4, the data processor 14 recognizes the wavelength of the measurement light (monochromatic light) incident on the end face of the bundle optical fiber 6. The other end of the bundle optical fiber 6 is guided to the light emitting / receiving box 15, and the measurement light incident from one end face of the bundle optical fiber 6 propagates inside the bundle optical fiber 6 and exits from the other end face, and is emitted from the light emitting / receiving box. 1
The light passes through a quartz window 16 provided on the bottom surface of the slab 5 and is irradiated onto a new soil surface 3 such as a cultivated land exposed by the plow 2.

The monochromatic measuring light radiated on the soil surface 3 is scattered and reflected on the soil surface 3, and the scattered reflected light is reflected on the quartz window 16.
And returns to the inside of the light emitting and receiving box 15 again. A part of the scattered reflected light that has returned into the light emitting and receiving box 15 is received by a photodetector 17 provided near the bundle optical fiber 6 inside the light emitting and receiving box 15. The photodetector 17 transmits a light receiving signal corresponding to the intensity of the received scattered reflected light to the data processing device 14.

Next, as shown in FIG. 3, the data processing device 14 converts the motor control signal received from the motor control unit 13 into wavelength data of the measurement light (S1). An optical spectrum of the scattered reflected light of the soil is created from the received light signal (S2), and data relating to the optical spectrum intensity of the scattered reflected light is substituted into a predetermined regression equation created in advance (S3). The components of the soil are analyzed, and the analysis result is displayed on a display unit (not shown) (S4). The regression equation is created by a procedure known as multivariate analysis.

[0007]

The conventional soil component analyzer irradiates a continuously changing measuring light from a bundle optical fiber onto a new soil surface exposed with a plow as described above.
The light scattered and reflected on the soil surface is received by a photodetector arranged near the bundle optical fiber, and the light spectrum of the scattered reflected light is obtained from the received light intensity.

[0008] However, soil is generally uneven in particle size, structure, and soil quality, and often contains small stones and foreign substances. If such unevenness exists in the soil, even if the measurement light is irradiated on the soil, the scattered reflected light will not be reflected uniformly in all directions, but will be strongly or weakly reflected in a specific direction, and will be reflected unevenly. As a result, the optical characteristics vary depending on the direction of light irradiation and the position of the photodetector, and soil components cannot be accurately analyzed.

Further, there are grooves or dents on the soil surface, and there are cases where grooves or dents which cannot be filled even with a plow remain. At this time, if the irradiation position of the measuring light coincides with a part of the soil surface, the distance between the soil surface and the light irradiator (irradiation side end surface of the bundle optical fiber) becomes longer, or the soil surface and the light detector Or the distance between them becomes longer. In such a case, even if the optical characteristics of the soil are the same, the intensity of the scattered and reflected light becomes weak, and the soil component cannot be analyzed accurately.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and has as its object the purpose of irrespective of the shape and structure of the soil, the variability of the soil properties and the unevenness of the soil surface, and the like. An object of the present invention is to provide a soil optical characteristic measuring device capable of measuring optical characteristics with high accuracy.

[0011]

SUMMARY OF THE INVENTION An optical characteristic measuring apparatus for soil according to the present invention has a light projecting portion for irradiating a measuring light toward the soil surface, an opening for facing the soil surface, and scatters light on the soil surface. A light capturing unit that captures and confine the reflected measuring light, and inside the light capturing unit, a light detector that receives the scattered reflected light, and an optical characteristic of the soil based on the measurement data of the light detector. Analysis means.

In this optical characteristic measuring apparatus for soil,
The measurement light is emitted from the light projecting unit toward the soil surface, and the measurement light scattered and reflected on the soil surface is captured and captured in the light capturing unit. The scattered reflected light confined in the light capturing unit is reflected several times in the light capturing unit and then enters the photodetector. The analysis means analyzes the optical characteristics of the soil based on the measurement data (light reception amount) of the photodetector.

Therefore, according to the present invention, the measuring light scattered and reflected on the soil surface is not directly received by the photodetector, but is scattered and reflected on the soil surface and scattered and reflected at a large solid angle. Can be averaged by capturing light in the light capturing unit and detected by the photodetector, so that it is possible to measure the original optical characteristics of the soil regardless of the soil shape, structure, soil quality, particle size, etc. It is possible to improve the reliability of the measurement data. In addition, since the measurement light scattered and reflected on the soil surface is captured by the light capture unit and received by the photodetector, the measurement area can be enlarged, and the amount of light received by the optical receiver is increased to increase the measurement sensitivity. Can be improved.

As the light capturing section, a substantially spherical cavity having an inner surface with high reflectivity can be used. In such a light capturing unit, the scattered reflected light that has entered the light capturing unit through the opening repeatedly reflects on the inner surface of the light capturing unit and enters the optical receiver regardless of the direction of reflection on the soil surface. The light receiver can detect the average of the intensity of the light reflected in each direction.

A typical optical characteristic measuring apparatus analyzes a soil component by analyzing a spectrum of scattered light reflected on a soil surface. In the configuration of the light emitting portion of the optical characteristic measuring device for soil of such a method,
As described in claim 3, a measurement light having a specific wavelength having a relatively narrow wavelength band is selectively extracted from light emitted from a light source that generates light having a relatively wide wavelength band, and is irradiated on the soil. The wavelength of the measurement light may be scanned over time by changing the wavelength of the measurement light to be applied to the light source. Alternatively, as described in claim 4, the light emitting unit includes a plurality of wavelengths generated by the light source. The measurement light is modulated with different parameters and emitted to the soil surface, and the optical characteristic analyzing means separates the output of the photodetector based on the modulation parameter to obtain the optical characteristics of the measurement light scattered and reflected on the soil surface. The characteristics may be analyzed.

According to a fifth aspect of the present invention, in the apparatus for measuring optical properties of soil according to the first aspect, the measuring light emitted from the light projecting unit is applied to the soil surface from inside the light capturing unit. It is characterized by being directed toward.

According to this embodiment, the measuring light can be irradiated from the inside of the light trapping part and the scattered reflected light can be collected in the light trapping part, so that the distance between the light trapping part and the soil surface can be shortened. As a result, the influence of disturbance light can be reduced.
In addition, the light capturing unit can be brought close to the soil surface, and the emission unit of the measurement light can be brought close to the soil surface, so that the irradiation intensity on the soil surface can be increased. Therefore,
The measurement sensitivity of the optical property measuring device can be improved.

[0018] In particular, when the space between the periphery of the opening provided in the light capturing portion and the soil surface facing the soil surface and the soil surface are surrounded by a light-shielding frame, the disturbance light can be more completely eliminated. The influence can be eliminated, and the measurement sensitivity and reliability can be further improved.

According to a seventh aspect of the present invention, in the soil optical characteristic measuring apparatus according to the first aspect, the measuring light is intermittently irradiated from the light projecting portion toward the soil surface. It is characterized by.

According to this embodiment, since the measuring light is intermittently irradiated, the light receiving data of the photodetector when the measuring light is irradiated and the light detecting data when the measuring light is not irradiated By comparing the received light data, the influence of disturbance light can be corrected.

According to an eighth aspect of the present invention, in the soil optical characteristic measuring apparatus according to the first aspect, a reference plate movable between an opening position of the light capturing unit and a position outside the opening is provided. It is characterized by having.

According to this embodiment, the instability of the optical system (for example, by arranging the reference plate at the opening of the light capturing unit and irradiating the reference plate with measurement light to monitor the optical characteristics of the reference plate) Fluctuations in optical characteristics due to changes in the sensitivity of the photodetector and fluctuations in the light source intensity of the light projecting section can be corrected. The soil surface can be measured by moving the reference plate to a position outside the opening of the light capturing unit.

According to a ninth aspect of the present invention, in the soil optical characteristic measuring apparatus according to the first aspect, a measuring position measuring device for specifying a measuring position is provided.

According to this embodiment, since the measurement position can be specified by the measurement position measuring device, the measurement data can be associated with the measurement position. Therefore, measurement data such as soil components can be comprehensively analyzed in the entire measurement area. Further, when soil improvement is performed later based on the measurement data, the work can be easily performed because the soil is associated with the measurement position.

In particular, according to the embodiment of the present invention, a soil characteristic map can be automatically created from position information and measured data.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 4 is a schematic diagram showing the configuration of a soil optical characteristic measuring device 21 according to an embodiment of the present invention.
The optical characteristic measuring device 21 includes a light projecting unit 22 and a light integrating sphere 2.
3. It comprises a photodetector 24 and a data processing device 25. The light projecting unit 22 irradiates the measuring surface of the specific wavelength to the soil surface 3 from the inside of the light integrating sphere 23, and includes a light source 27, an optical chopper 28, and a spectroscopic device 29. The light source 27 includes a halogen lamp 30 and a reflecting plate 31, and continuously emits white light and sends the white light to the spectroscopic device 29.

The light chopper 28 blocks the white light emitted from the light source 27 at a certain timing.
It has a structure as shown in FIG. That is, the optical chopper 28 includes a light-shielding disk 34 in which light-transmitting portions (windows) 32 and light-shielding portions 33 are arranged at a constant pitch along the circumferential direction.
When the white light is incident on the light transmitting part 32, the white light is transmitted and the white light is incident on the spectroscopic device 29, and when the white light is incident on the light shielding part 33,
The white light emitted from the light source 27 toward the spectroscopic device 29 is blocked. Since the light-shielding disk 34 is rotated at a constant speed by the motor 35, white light is transmitted through the light-shielding disk 34 at a certain timing or cut off. A light-emitting element 36 for monitoring is arranged on one side and a light-receiving element 37 for monitoring is arranged on the other side of the light-shielding disk 34 with the light-transmitting part 32 and the light-shielding part 33 provided therebetween. When the white light from the light source 27 passes through the light transmitting part 32, the light r emitted from the monitoring light emitting element 36 also passes through the light transmitting part 32 and the monitor light receiving element 37 and the light receiving element 37 monitor. 37, and the white light of the light source 27 is
Since the light r emitted from the monitor light-emitting element 36 is also blocked by the light shielding unit 33 when the light is blocked by
The monitoring light receiving element 37 can detect whether the white light of the light source 27 is transmitted or blocked. The light chopper 28 is used to remove the influence of disturbance light such as sunlight (details will be described later).

The spectroscopy device 29 selectively extracts light of a specific wavelength from the white light from the light source 27 as measurement light, and scans the selected wavelength at a constant speed from a predetermined shortest wavelength to a longest wavelength. Such a spectroscopic device 2
As the filter 9, a filter disk 9 provided with a wavelength selection filter (interference filter) 8 and a slit plate 7 as described in the conventional example (FIG. 2) can be used.

Alternatively, as shown in FIG. 6A, a spectroscopic device 29 is constituted by a diffraction grating 38 for dispersing the white light and a slit plate 39, and the spectroscopic device is moved by moving the diffraction grating 38 or the slit plate 39. The wavelength of the measurement light emitted from the light source 29 may be continuously changed. Further, as shown in FIG. 6B, a spectral device 29 is constituted by a prism 40 for dispersing white light and a slit plate 41, and the prism 40 or the slit plate 41 is moved to be emitted from the spectral device 29. The light wavelength may be changed continuously.

Since the light transmission and cutoff timing cycles of the optical chopper 28 are usually sufficiently shorter than the scanning cycle of the selected wavelength in the spectroscopic device 29, the emission wavelength from the spectroscopic device 29 or the light source 27 is output. Is emitted in the form of pulses in which measurement light changes with time and regularly.

The light integrating sphere 23 has a substantially spherical shell shape, and an irradiation window 42 is provided on the lower surface thereof so as to face the soil surface 3. Inside the light integrating sphere 23, a cavity serving as a light capturing unit is provided, and the inner wall surface has a reflectance of almost 100%.
Light-diffusing surface (or mirror surface). On the inner surface of the light integrating sphere 23, a light projecting unit 43 for measuring light is provided at a position facing the irradiation window 42, and the photodetector 24 is provided on the side surface. As the photodetector 24,
A semiconductor light receiving element such as InGaAs, PbS, PbSe, or the like, a silicon photodiode, or the like can be used.

The spectroscopic device 29 and the light projection unit 4 of the light integrating sphere 23
3 is connected by a light guiding means 44 such as an optical fiber bundle (bundle optical fiber), and the measuring light emitted from the spectroscopic device 29 is transmitted through the light guiding means 44 to the light integrating sphere 23.
Of the light integrating sphere 2
The measurement light emitted into the surface 3 passes through the irradiation window 42 and is exposed to the soil surface 3.
Is irradiated. The soil surface 3 is a new soil surface in which the soil has been scraped and exposed by the plow 2 and has a light integrating sphere 23.
And at a nearly constant distance. When the measurement light emitted from the light projection unit 43 scatters on the inner surface of the light integrating sphere 23, the measurement light is received by the photodetector 24, so that the measurement light is collected in the irradiation window 42 by the light projection unit 43. A condensing lens may be provided for light emission, or a convex lens-like processing may be applied to the end face of each optical fiber of the optical fiber bundle.

The measuring light applied to the soil surface 3 is reflected and scattered on the soil surface 3, and most of the measurement light returns from the irradiation window 42 to the inside of the light integrating sphere 23 again. The scattered reflected light returned into the light integrating sphere 23 repeats diffuse reflection without being absorbed inside the light integrating sphere 23, and is scattered reflected light irregularly and unevenly reflected in various directions on the soil surface 3. Are averaged inside the light integrating sphere 23, and the scattered reflected light uniformized in each direction is received by the photodetector 24.

Even if the properties (components) of the soil are the same, if the inclination and unevenness of the surface of the soil, the size of the soil particles, and the like are different, the intensity of the light scattered and reflected from the soil surface 3 due to the distribution depends on the direction to be detected. Variations occur. However, unlike the optical property measuring device 21 of the present invention, the measurement light scattered and reflected on the soil surface 3 is not directly received by the photodetector 24, but is scattered and reflected on the soil surface 3 and emitted at a large solid angle. If the scattered and reflected light in a wide range is averaged by being captured in the light integrating sphere 23 and detected by the photodetector 24, the optical characteristics of the soil can be maintained irrespective of the shape and structure of the soil, the nature of the soil, and the size of the particles. Characteristics can be measured, and the reliability of measurement data can be improved.

Since the measuring light scattered and reflected in a wide area corresponding to the area of the irradiation window 42 of the light integrating sphere 23 can be collected in the integrating sphere, a large amount of measuring light is collected in the optical receiver to increase the amount of received light. And the measurement sensitivity can be improved.

When the scattered and reflected light is received by the photodetector 24 in this manner, a photodetection signal is sent from the photodetector 24 to the data processing device 25. On the other hand, the data processing device 25 receives a signal indicating the wavelength of the measurement light from the spectroscopic device 29 in real time. When the measurement light is reflected by the soil surface 3,
Because the components of the soil absorb light of a specific wavelength,
It shows a unique light spectrum (absorption spectrum) depending on the components of the soil. If the light intensity of the measurement light received by the photodetector is detected while continuously changing the wavelength of the measurement light by the spectroscope 29, the light spectrum of the scattered reflected light can be obtained. By analyzing at 25, the components of the soil can be analyzed.

The measurement light is transmitted from the inside of the light integrating sphere 23 to the soil surface 3.
, The distance between the light integrating sphere 23 and the soil surface 3 can be reduced, and disturbance light such as sunlight is hard to enter from this gap. However, it is impossible to prevent disturbance light from entering the integrating sphere at all.
8 eliminates the influence of disturbance light. That is, when the measurement light is blocked by the optical chopper 28, the output of the photodetector 24 is considered to be due to disturbance light. Therefore, the output of the photodetector 24 when the measurement light is received and the disturbance By determining the difference in output due to light, the influence of disturbance light can be corrected.

FIG. 7 shows a circuit 45 for correcting the influence of disturbance light, and includes a main amplifier (tuning amplifier) 4.
6. A lock-in amplifier 51 including a synchronous rectifier circuit 47, a low-pass filter 48, a reference signal amplifier (tuning amplifier) 49 and a phase shift circuit 50, and an output from the photodetector 24 transmitted through the optical chopper 28. A delay circuit 52 for delaying by half the period of light / interruption and sending the delayed signal to the reference signal amplifier 49;
4 comprises an electronic switch 53 for switching the output between the main amplifier 46 side and the reference signal amplifier 49 side. The electronic switch 53 connects the photodetector 24 to the main amplifier 46 when the light receiving element 37 for monitoring detects the light transmitting state, and detects the light when the cutoff state is detected. Is connected to the reference signal amplifier 49 side. Therefore, in the correction circuit 45, the photodetector 2 using only disturbance light is used.
The four outputs are input to the reference signal amplifier 49 as reference signals, and the output of the photodetector 24 based on the disturbance light and the measurement light is input to the main amplifier 46. The received light signal of the disturbance light and the measurement light is narrowed in the bandwidth by the main amplifier 46, and then the synchronous rectification circuit 47
Sent to The reference signal due to the disturbance light is set to an appropriate phase (0 ° or 90 °) by the phase shift circuit 50 and input to the synchronous rectification circuit 47 in order to detect only a signal component having a certain frequency / phase relationship with the reference signal. You. This output is integrated by a low-pass filter 48 at the next stage, and after removing signal components due to disturbance light, the output is sent to the data processing device 25 to obtain an optical spectrum.

As the light guiding means 44 connecting the spectroscopic device 29 and the light integrating sphere 23, the optical characteristic measuring device 5 shown in FIG.
As shown in FIG. 4, a relay lens 55 for light transmission composed of a plurality of condenser lenses 55a and 55b may be used. If the distance between the condenser lenses 55a and 55b can be adjusted,
The beam diameter of the measurement light can be adjusted.

(Second Embodiment) FIG. 9 is a partially broken sectional view of a soil optical characteristic measuring device 56 according to another embodiment of the present invention. In this embodiment, an optical fiber bundle 57 serving as a light guiding unit 44 connecting the spectroscopic device 29 and the light integrating sphere 23.
Is projected into the light integrating sphere 23 to the vicinity of the irradiation window 42. In this embodiment, since the end face of the optical fiber bundle 57 is close to the soil surface 3, it is possible to irradiate the soil surface 3 with strong measurement light, and to increase the light receiving level of the photodetector 24 to improve the measurement sensitivity. Can be enhanced. On the other hand, in order to prevent the scattered reflected light scattered and reflected on the soil surface 3 and captured in the light integrating sphere 23 from being absorbed by the optical fiber bundle 57 and reducing the amount of light received by the photodetector 24, the light integrating sphere is reduced. Inside the optical fiber 23, a light diffusing substance 58 is coated on the outer peripheral surface except the end surface of the optical fiber bundle 57.

(Third Embodiment) FIG. 10 is a partially cutaway sectional view of a soil optical characteristic measuring device 59 according to another embodiment of the present invention. In this embodiment, a reference plate 60 is provided below the irradiation window 42 of the light integrating sphere 23,
The reference plate 60 can be moved horizontally to a position off the irradiation window 42 along a rail or a guide provided on the lower surface of the light integrating sphere 23. As the reference plate 60, a ceramic plate such as alumina can be used, but at least the upper surface (inner surface) has a reflectance of almost 100%.

According to this embodiment, the reference plate 60 is moved to the irradiation window 42 so that the irradiation window 42 of the light integrating sphere 23 is closed by the reference plate 60, and the reference plate 60 is irradiated with the measuring light, and By monitoring the optical spectrum of the optical system, fluctuations in optical characteristics due to instability of the optical system (for example, fluctuations in the sensitivity of the photodetector 24 and fluctuations in the light source intensity of the light projecting unit 22) are detected, and the measurement data is corrected. Can be used.
The soil surface 3 can be measured by moving the reference plate 60 to a position outside the opening of the irradiation window 42.

The reference plate 60 has one end pivotally connected to the edge of the irradiation window 42 of the light integrating sphere 23 as in an optical characteristic measuring device 61 shown in FIG. The irradiation window 42 may be closed by opening the reference plate 60 and tilting it. In this case, the reflectance on both surfaces of the reference plate 60 is almost 100%.

(Fourth Embodiment) FIG. 12 is a schematic diagram showing a configuration of a soil optical characteristic measuring device 62 according to still another embodiment of the present invention. In the optical characteristic measuring device 62, a plurality of light emitting elements 63a, 63b,... Having different light emission wavelengths and a light emitting element driving circuit for emitting the light emitting elements 63a, 63b,. 64a, 64b,...
Is configured. The light emitting elements 63a, 63b,... Are light emitting diodes (LEDs), semiconductor laser elements (LDs), or the like, and may be individual elements or arrays.

Here, the light emitting elements 63a, 63b, 63
It is assumed that three light sources have different emission wavelengths λ1, λ2, λ3, respectively, and light is emitted by the light-emitting element driving circuits 64a, 64b, 64c by applying intensity modulation at different modulation frequencies f1, f2, f3. Each light emitting element 63
From a, 63b, and 63c, measurement lights of the respective emission wavelengths λ1, λ2, and λ3, which are intensity-modulated at the frequencies f1, f2, and f3, are simultaneously emitted, and the respective measurement lights are collected by the condenser lens 65 of the light projection unit 43. Then, the soil surface 3 is irradiated from the irradiation window 42 of the light integrating sphere 23. The measurement light of each wavelength scattered and reflected by the soil surface 3 returns to the light integrating sphere 23 and is received by the light detector 24. The light receiving signal of the photodetector 24 is discriminated by the filter circuit 66 into signals of frequencies f1, f2, and f3. Each frequency f1, f discriminated by the filter circuit 66
The light receiving signals modulated by 2 and f3 are sent to different demodulating circuits (integrating circuits and the like) 67a, 67b and 67c, respectively.
Each of the demodulation circuits 67a, 67b, 67c converts the signal into an intensity signal, which is output to the data processing device 25.
At 5 the light spectrum is analyzed.

According to such an embodiment, the spectroscopic device 2
9 is not required, and the light emitting elements 63a, 63
By using 3b and 63c, power saving can be achieved. Further, since only a signal of a specific frequency is discriminated by the filter circuit 66, the influence of disturbance light can be eliminated.

In this embodiment, the irradiation window 42 of the light integrating sphere 23 is transparent to the measuring light in order to prevent dirt and soil from entering the inside of the light integrating sphere 23.
A transparent plate 68 such as quartz glass is fitted.

(Fifth Embodiment) FIG. 13 is a schematic view showing a configuration of a soil optical characteristic measuring device 69 according to still another embodiment of the present invention. In this embodiment, a transparent plate 68 such as quartz glass is provided on the irradiation window 42 of the light integrating sphere 23.
An opaque light-shielding frame 70 is provided around the irradiation window 42 so that the lower end of the light-shielding frame 70 is thinly tapered so as to be easily inserted into the soil.

The soil is measured while the light-shielding frame 70 is inserted into the soil and the transparent plate 68 of the irradiation window 42 is pressed against the soil surface 3. When the measurement is performed in this manner, the transparent plate 68 is pressed against the soil surface 3 so that the soil surface 3 can be leveled and measured, and the light integrating sphere 23 can be installed straight on the soil surface 3. The direction of reflection of the scattered reflected light can be made uniform. Further, the light shielding frame 7 is provided around the irradiation window 42.
Since 0 is provided, it is possible to reliably prevent disturbance light from entering from a gap between the lower surface of the light integrating sphere 23 and the soil surface 3.
Further, by inserting the light-shielding frame 70 into the soil, the optical property measuring device 69 can be firmly installed.

The optical property measuring device 69 is moved to a measuring position by a tractor, and presses the transparent plate 68 of the irradiation window 42 against the soil surface 3 so as to automatically maintain a constant pressure, thereby performing soil measurement. I just need. Further, in the case of this embodiment, since it is not necessary to float the light integrating sphere 23 from the soil surface 3, a person carries the optical characteristic measuring device 69, inserts the light shielding frame 70 into the soil at the measurement position, and sets the transparent plate. 68 can be installed so as to be pressed against the soil surface 3 and the measurement can be performed in that state.

(Sixth Embodiment) FIG. 14 is a schematic view showing a configuration of a soil optical characteristic measuring apparatus 71 according to still another embodiment of the present invention. This embodiment is intended for highly accurate measurement. The light source 27 includes a halogen lamp 30, a reflector 31, and a condenser lens 72. As the spectroscopic device 29, an acousto-optic wavelength tuning element (Acoust-Optic Tunable Filter; hereinafter, AOTF)
73) is used.

The AOTF 73 is a band-pass filter that separates monochromatic light from white light and electrically scans the wavelength, and has no movable part. The AOTF 73 is composed of an acousto-optic crystal [for example, one in which the acoustic wave of tellurium dioxide (TeO ₂ ) crystal and the traveling direction of light intersect] 74 and an acoustic wave driver 75, and as shown in FIG. Acoustic Transduce
r) and an absorber (Acoustic Absorber) 77 are attached, and when an electric signal of RF frequency is applied to the transducer 76 from the acoustic wave driver 75, an acoustic wave is transmitted from the transducer 76 to the absorber 77 in the crystal 74. As it passes and the acoustic wave passes, the strain created in the crystal 74 acts like a grating. When the AOTF 73 is irradiated with white light, only monochromatic light is transmitted, and the transmission wavelength can be controlled by the RF frequency. The half-width of this transmission wavelength can be reduced to the order of 1 nm, depending on the wavelength,
The transmittance is high and up to 98% is possible. However, since the transmitted light is separated into 0th-order diffracted light and ± 1st-order diffracted light, FIG.
As shown in FIG. 5, the 0th-order diffracted light and the -1st-order diffracted light (or +
The first-order diffracted light) is cut by the shielding plate 78 so as not to reach the light projecting portion 43 of the light integrating sphere 23.

Thus, the spectroscopic device 2 composed of the AOTF 73
9 is transmitted from the inside of the light integrating sphere 23 to the soil surface 3.
The irradiation wavelength ranges from the shortest wavelength to the longest wavelength (for example, 400 nm to 250 nm) by the acoustic driver 75.
0 nm). AOTF as spectroscopic device 29
If 73 is used, since there is no movable part and the wavelength can be controlled electrically, the wavelength scanning speed can be increased. In addition, the AOTF 73 is
It is possible to control the light transmission and blocking of the AOTF7.
3 and the acoustic wave driver 75 can have the same function as the optical chopper 28, so that the influence of disturbance light in the received light signal can be eliminated. On the other hand, the data processing device 25
The irradiation wavelength is detected by a signal from the acoustic wave driver 75, and the timing of light transmission and cutoff by the AOTF 73 is monitored.

Further, as the photodetector 24 for receiving the measurement light scattered and reflected on the soil surface 3, a light-receiving element having a high response such as an InGaAs element is used.
4 is provided with a temperature control device 79 for keeping the temperature of the photodetector 24 at a constant temperature in order to eliminate fluctuations in sensitivity, output, and the like.

The data processing device 25 has a function of removing the influence of disturbance light by comparing the received light signal of the AOTF 73 at the time of light transmission (measurement) and the light reception signal at the time of cutoff (not measurement), and an optical spectrum from the received light signal. And a function to request. Here, as a method of obtaining the optical spectrum from the received light signal, it is preferable to use Fourier transform type spectroscopy,
In particular, a method using an interferogram is desirable. Here, the interferogram is a change F (x) of the interference light intensity measured and recorded as a function of the optical path difference x when changing the optical path difference of the light beam interferometer. The optical spectrum is obtained by performing the inverse conversion. These interferograms, Fourier transform spectroscopy, and the like are conventional methods for obtaining an optical spectrum, and thus detailed descriptions thereof are omitted.

The optical characteristic measuring device 71 includes a reference plate 60 for correcting a temporal variation of the light projecting unit 22, and obtains a light absorption spectrum in the following order. First, the reference plate 60 is lowered and the irradiation window 42 is closed, and in this state, the irradiation wavelength of the measurement light is scanned to measure the diffuse reflection intensity spectrum R (λ) of the reference plate 60. Then
The reference window 60 is raised, the irradiation window 42 is opened, and the irradiation wavelength of the measuring light is scanned again to obtain the diffuse reflection intensity spectrum S of the soil.
Measure (λ). Then, the light absorption spectrum of the soil is determined from the absorption intensity Abs (λ) = log [R (λ) / S (λ)].

In the optical characteristic measuring apparatus 71 of this embodiment, an AOTF 73, which can electrically perform high-speed and high-precision wavelength scanning and also has a disturbance light correction function (optical chopper function), is used as a spectroscope. High-accuracy soil component analysis is performed by correcting fluctuations of the light projecting unit 22 using the plate 60, stabilizing the characteristics of the light detector 24 by the temperature control device 79, obtaining an optical spectrum by an interferogram, and the like. Making it possible.

(Eighth Embodiment) FIG. 16 is a schematic diagram showing a configuration of a soil optical characteristic measuring apparatus 80 according to still another embodiment of the present invention. This optical characteristic measuring device 80
A measurement position detection device 81 is provided. As the measurement position detection device 81, a positioning system (GP
S: Global Positioning System), a system that detects a position by monitoring a moving direction and a moving amount using a gyro sensor or the like can be used. The position information detected by the measurement position detection device 81 is sent to the map creation unit 82. The map creator 82 associates and accumulates information on the soil component obtained from the data processing device 25 with the measurement position information obtained from the measurement position detector 81, and automatically generates a soil component map for the entire measurement area. The created soil map is stored in a recording medium, displayed on a display, or output from a printer or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of a conventional soil component analyzer.

FIG. 2 is a plan view showing the above filter disk.

FIG. 3 is a flowchart showing a processing procedure in the data processing device.

FIG. 4 is a schematic diagram illustrating a configuration of a soil optical characteristic measuring device according to an embodiment of the present invention.

FIG. 5 is a perspective view showing a structure of an optical chopper used in the optical characteristic measuring device of the above.

FIGS. 6A and 6B are schematic diagrams showing spectroscopic devices having different configurations.

FIG. 7 is a diagram showing a circuit for correcting a light receiving signal of a photodetector by an optical chopper.

FIG. 8 is a schematic sectional view showing another example of the light guide means provided on the light integrating sphere.

FIG. 9 is a partially cut-away schematic cross-sectional view showing an apparatus for measuring optical properties of soil according to another embodiment of the present invention.

FIG. 10 is a partially cut-away schematic cross-sectional view showing an apparatus for measuring optical properties of soil according to still another embodiment of the present invention.

FIG. 11 is a partially cut-away schematic cross-sectional view showing a soil optical property measuring apparatus according to still another embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view showing an apparatus for measuring optical properties of soil according to still another embodiment of the present invention.

FIG. 13 is a schematic sectional view showing a soil optical characteristic measuring apparatus according to still another embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view illustrating a device for measuring optical properties of soil according to still another embodiment of the present invention.

FIG. 15 is an explanatory view schematically showing an acousto-optic wavelength tuning element.

FIG. 16 is a schematic sectional view showing a soil optical property measuring apparatus according to still another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 3 soil surface 22 light projecting part 23 light integrating sphere 24 light detector 25 data processing device 28 light chopper 29 spectroscopic device 42 irradiation window 60 reference plate 63a, 63b, 63c light emitting element 68 transparent plate 70 light shielding frame 81 measurement position detecting device 82 Map creator

Claims (10)

[Claims] 1. A light projecting unit for irradiating a measuring light toward a soil surface, and a light capturing unit having an opening for facing the soil surface and capturing and confining the measuring light scattered and reflected on the soil surface. A light detector for receiving the scattered reflected light inside the light capturing unit; and a means for analyzing optical characteristics of the soil based on measurement data of the light detector. . 2. The soil optical characteristic measuring device according to claim 1, wherein the light capturing unit is a substantially spherical cavity having an inner surface with high reflectance. 3. The light projecting unit selectively emits a light source that generates light having a relatively wide wavelength band and measurement light having a specific wavelength that has a relatively narrow wavelength band from the light of the light source. The soil optical characteristic measuring apparatus according to claim 1, further comprising: means for temporally changing a wavelength of the measurement light. 4. The light projection unit has a light source that generates measurement light of a plurality of wavelengths, and a unit that modulates and emits measurement light of a different wavelength with different parameters, and the optical characteristic analysis unit includes: The optical characteristic measuring apparatus for soil according to claim 1, further comprising a function of separating an output of a photodetector based on the modulation parameter. 5. The optical characteristic measurement of the soil according to claim 1, wherein the measurement light emitted from the light projecting unit is irradiated from inside the light capturing unit toward a soil surface. apparatus. 6. The soil optical characteristic measuring apparatus according to claim 5, further comprising a light-shielding frame surrounding a periphery of an opening provided in the light capturing unit and a soil surface. 7. The soil optical characteristic measuring device according to claim 1, wherein the measuring light is intermittently irradiated from the light projecting portion toward the soil surface. 8. The soil optical characteristic measuring device according to claim 1, further comprising a reference plate movable between an opening position of the light capturing unit and a position outside the opening. 9. The soil optical characteristic measuring device according to claim 1, further comprising a measuring position measuring device for specifying a measuring position. 10. The apparatus according to claim 9, further comprising a unit for creating a soil characteristic map from the position information output from the measurement position measuring device and the measurement data obtained by the optical characteristic analysis unit. Optical property measuring device for soil.