JPH10253528A - Method for spectral reflection factor measurement of plant body, and apparatus therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly accurate and fast measurement of the spectral reflection factor of plant body by turning a plurality of laser lights with different wavelengths to light beams passing on the same optical path and irradiating the plant body, and measuring the reflected light. SOLUTION: Different semiconductor laser lights La -Lc are emitted from light power sources 1a -1c by oscillators 2a -2c of a measuring head A and the respective light beams are made incident on a light dispersing element 3 to irradiate a plant body P passing through the same optical path after receiving a diffraction effect. The respective reflected laser lights La -Lc are cast on a photodetecting unit 8 changing the optical path sequentially passing through a reflection mirror 4, a lens 5, a reflection mirror 6 and a lens 7. In this process, the number of the light detecting unit 8 is one but, for example, the laser light sources 1a -1c are lit sequentially to be separated in terms of the wavelengths and the intensity of each laser light is transduced into an electrical signal to be amplified by a preamplifier 9. The electrical signal thus obtained is converted to a digital signal and the results undergo a data processing to compute a spectral reflection factor of the plant body P thereby enabling highly accurate and fast measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the spectral reflectance of a plant, wherein the spectral reflectance of the plant can be measured with high accuracy and at a high speed by utilizing a laser beam. .

[0002]

2. Description of the Related Art FIGS. 4 and 5 show a conventional apparatus for measuring the spectral reflectance of a plant. This measuring device includes a measuring head A ′ and a measuring device main body B ′. The measuring head A ′ is for detecting the spectral radiance of the plant P, and by the action of the equipped interference filter 31, only the light of a plurality of different set wavelengths different from each other reflected from the plant P is measured. A plurality of types (six types in the illustrated example) of detectors C _{1 to} C ₆ each of which can be detected;
An ultrasonic sensor 32 for measuring the distance (H) between the plant P and the measuring head A ′, and a light source 33 composed of a halogen lamp are provided. When the light source 33 is a halogen lamp, the spectral radiance also changes when the distance (H) between the plant P and the measurement head A ′ changes, even when the light amount is constant. , The distance (H) is measured as one of the basic values for calculating the spectral reflectance.

In each of the detectors C _{1 to} C ₆ , only light having a set wavelength corresponding to the interference filter 31 provided therein is detected. Guided by B ', this measuring instrument body B'
, The reflected light of each set wavelength is calculated as an analog quantity, and the analog quantity related to the reflected light is converted into a digital signal by the A / D converter 35 and then input to an arithmetic unit 36 such as a personal computer. On the other hand, the ultrasonic sensor 3
2, the distance (H) is measured, and is converted into a digital signal by the A / D converter 35.
6 is input. Based on the intensity of the reflected light from the plant P and the distance (H) between the plant P and the measuring head A ', the arithmetic unit 36 calculates the spectral reflectance of the plant P. Is done. The spectral reflectance of the plant is measured in this way mainly for identifying the plant, and the calculated spectral reflectance at a plurality of calculated wavelengths and the previously known spectral reflectance of the plant are measured. By comparing the spectral reflectance at each wavelength, if a plurality or more of the plurality are approximately the same or similar to each other, the plant to be measured is a plant whose spectral reflectance is known in advance. It is determined that there is.

As described above, the conventional spectral reflectance measuring apparatus uses a halogen lamp as a light source and has a low luminance, so that the measurement requires an area of a certain size or more. When the measurement area becomes large, there is a possibility that the spectral reflectance of an object other than the original measurement object may be measured, and as a result, the measurement accuracy is reduced. In addition, if the measurement area is forcibly reduced, the entire light quantity decreases, and there is a problem that a measurement error occurs due to noise.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to measure the spectral reflectance of a plant with high accuracy and at high speed.

[0006]

In order to solve the above-mentioned problems, the present invention employs a method in which a plurality of laser lights having different oscillation wavelengths are transmitted on substantially the same optical path by using a simple optical system such as a light dispersion element. And irradiating the light to the plant body, and measuring the reflected light to obtain the spectral reflectance of the plant body. In addition, a device for realizing this method is to irradiate a plant with a plurality of laser lights having different oscillation wavelengths as light rays passing on substantially the same optical path, and to convert the magnitude of the reflected light into an electric quantity. And a controller for calculating the spectral reflectance of the plant by performing data processing of the electric quantity regarding the reflected light obtained by the measuring head.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail by way of examples. FIG. 1 is a block diagram of a spectral reflectance measuring apparatus according to the present invention. In FIG.
The spectral reflectance measuring apparatus according to the present invention includes a measuring head A for measuring reflected light of laser light applied to the plant P,
A controller B for converting the quantity of electricity related to the reflected light from the plant body measured by the measuring head A into a digital signal, performing data processing on the converted signal, and finally calculating the spectral reflectance of the plant body P It is composed of

The measuring head A is provided with about two to five laser power supplies having different oscillation wavelengths as an internal light source. In the embodiment, three semiconductor laser power supplies having different oscillation wavelengths (hereinafter simply referred to as “laser power supplies”) are used. 1a, 1b, 1c
It has. Each of the laser power supplies 1a, 1b, 1c has an oscillator 2a, 2b, 2c, respectively.
The laser beams La, Lb and Lc emitted from the laser power sources 1a, 1b and 1c are frequency-modulated by b and 2c. Each light beam of the different semiconductor laser beams La, Lb, Lc emitted from each of the laser power supplies 1a, 1b, 1c enters a light dispersion element 3 such as a diffraction grating or a prism, and receives a diffraction effect in the element 3. Later, the plant P is irradiated on the same optical path.

Each of the laser beams La, Lb, and Lc irradiated and reflected (emitted) on the plant body P passes through a condensing optical system such as a reflecting mirror 4, a lens 5, a reflecting mirror 6, and a lens 7, thereby obtaining The light path is sequentially changed, and the light is irradiated on the light detection unit 8 such as a photodiode. In this part of the light detection unit 8,
The intensity of the emitted laser light is converted into a voltage, which is one of the electric signals, and output. The voltage, which is the output signal, is amplified by the preamplifier 9. This light detection unit 8 is one, but the light source is a laser beam, and the frequency of each laser beam La, Lb, Lc emitted from the laser power supply 1a, 1b, 1c by the oscillator 2a, 2b, 2c. By performing modulation or sequentially turning on the laser power supplies 1a, 1b, 1c, an output signal can be separated and extracted from the photodetection unit 8 for each wavelength.

[0010] The controller B is provided with a laser beam La, Lb, Lc from the plant P measured by the measuring head A.
For converting the electric signal of the reflected light into a digital signal, performing data processing on the converted signal, and finally calculating the spectral reflectance of the plant P. The laser light La, Lb, Lc
Each of them includes a lock-in amplifier 11a, 11b, 11c, a multiplexer 12, an A / D converter 13, a central processing circuit (CPU) 14, an interface 15, and the like.

In the example shown in FIG. 1, the laser power sources 1a, 1b, 1c output 532 nm, 670 nm, 7
Each of the laser beams La, Lb, and Lc modulated and emitted to a different frequency of 80 nm is incident on the light dispersion element 3 and, after being subjected to a diffraction effect, becomes a light ray that passes through the same optical path and becomes a plant P. Is irradiated. The reflected light illuminated and reflected on the plant body P is reflected by the above-described reflecting mirrors 4 and 6 and the lens 5.
The light is incident on the light detection unit 8 via a light collecting optical system composed of 7 and the like, and is collected.

The output signal from the light detection unit 8 is
The signals are amplified by the preamplifier 9 and amplified by the respective lock-in amplifiers 11a, 11b, 11c of the controller B for each frequency, and these three types of output signals are digitally converted by the A / D converter 13 to form a central processing circuit. When the data processing is performed by 14, the signal intensity (the value obtained by converting the intensity of the reflected light into a voltage) for each of the three types of wavelengths is obtained. Then, in the controller B, when each signal intensity of the plant P obtained by the above measurement is compared with each signal intensity of the same frequency on the reference white plate as a reference of the reflectance, the above-mentioned measurement object is obtained. The spectral reflectance of the plant P is determined.
The method for measuring the spectral reflectance is as follows.
Then, the spectral reflectance of the plant P is determined by comparing each reflected light with the reference white plate.

Here, since the signal intensity obtained from the plant P to be measured is not its absolute value,
In calculating the spectral reflectance of the reference object, it is necessary to make a correction by comparing with the signal intensity of the reference object. When a white plate is selected as the reference object, the signal intensity of the white plate is set to 100%, and the spectral reflectance M (λ) at the wavelength (λ) of the plant P is set.
Is represented by an equation of M (λ) = T (λ) × [I (λ) / R (λ)]. Here, T (λ) indicates the spectral reflectance at the wavelength (λ) of the reference white plate, and I (λ) indicates the signal intensity at the wavelength (λ) when the plant P to be measured is measured. R (λ) indicates the signal intensity at the wavelength (λ) when the reference white plate is measured.

FIG. 2 is a graph showing the results of continuous measurement of the spectral reflectance of the leaves of A. scrofa for about 10 seconds in the stationary state by using the laser beams of the three different frequencies. It can be seen that the spectral reflectance is measured in a very stable state also at the frequency.

FIG. 3 shows the measurement of the spectral reflectance when the present measurement apparatus is fixed and the leaf of the swelling stone, which is the object to be measured, is moved at a constant distance from the measurement head A at 10 cm / S. It is a figure showing a result. In this measurement example, the spectral reflectance of soil is measured from the start of measurement to a certain time. From this result, it can be seen that even when the measurement device and the measurement target relatively move, their spectral reflectances are continuously measured. Note that the spectral reflectance is 4
Between 0% and 60% is the threshold value of Ezonoseki, which is the object to be measured, and when the spectral reflectance at this threshold value is measured, an output is displayed to that effect.

In the above embodiment, the measuring head A and the controller B are integrated, but the measurement can be performed even if the two are separated. Further, the processing of the measurement data can be transferred to an external personal computer 16 through the interface 15 for processing.

[0017]

According to the present invention, a plurality of laser beams having different oscillation wavelengths are used as the internal light source of the detector, and the plurality of laser beams are focused on the same optical path to irradiate a plant. Since the configuration measures the reflected light, various effects as described below can be obtained as compared with a conventional spectral reflectance measuring apparatus provided with a detector using a halogen lamp as a light source.

(1) Since the brightness of the laser beam, which is the light source of the detector, is extremely high, the spectral reflectance of the object to be measured can be measured even with a small measurement area, and highly accurate measurement is possible. For this reason, the reflectance of each part such as a leaf, a stem, a flower, and a fruit of a plant can be measured with high accuracy. Predict differences and growth stages. In this regard, when the light source is a halogen lamp, the luminance is significantly lower than that of the laser light, so that a large area is required for the measurement. In addition, if the measurement area is forcibly reduced, the total light amount is reduced, which may cause noise to cause a large measurement error.

(2) Since the light source of the detector is a laser beam, continuous high-speed measurement can be performed outdoors. In order to measure the spectral reflectance of a plant outdoors, it is necessary to chop the light source in order to remove the influence of sunlight or disturbance light. In a conventional device using a halogen lamp as a light source,
A mechanical chopper is required, and the chopper (light shield) is moved using a motor, etc.
Motors have their life and maintenance is essential. In the measuring device according to the present invention using laser light as a light source, modulation (changing the frequency) is performed on the laser power supply.
Can be chopped,
A drive unit such as a motor is not required unlike the conventional device. Further, by setting the chopping frequency of each laser power supply to a different frequency, the spectral reflectance of a plurality of wavelengths can be measured by one light detection unit. In this regard, in the conventional apparatus using a halogen lamp as a light source, the number of interference filters and the number of light detection units required for different wavelengths are greatly improved. As described above, in an apparatus using laser light, chopping is performed electrically, so that chopping at a high frequency becomes possible.
In addition, since the number of photodetection units is also minimized, continuous high-speed measurement of spectral reflectance is possible.

(3) According to the spectral reflectance measuring method of the present invention, the influence of the measuring distance can be reduced. The laser light, which is the light source of the detector, can be regarded as a point light source because of its extremely high brightness, and the light can be converted into a light with high parallelism. Even if it changes, the change in illuminance at the irradiated portion is small. As a result,
The influence on the change of the measurement distance is reduced, and in combination with the fact that the above-described measurement area is small, high-precision measurement is possible. This is particularly effective for measuring an object having a large difference in distance or shape. In this regard, when the light source is a halogen lamp, the illuminance at the irradiated portion decreases in inverse proportion to the measurement distance, so that it is necessary to consider the measurement distance when measuring the spectral reflectance of the measurement object. Thus, the above-described distance sensor (such as an ultrasonic sensor) is required.

(4) The spectral reflectance measuring device according to the present invention has low power consumption and a long life. For example, in a semiconductor laser, electric power is efficiently converted to light,
The power consumption of the device is small. In this regard, in a conventional apparatus using a halogen lamp as a light source, light other than a target wavelength is emitted from the light source, so that the power use efficiency is low and the power consumption is large. Further, the semiconductor laser has a longer life than the halogen lamp and can be used stably for a long time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a spectral reflectance measuring apparatus according to the present invention.

FIG. 2 shows that, in a stationary state, the spectral reflectance of a leaf of Ezonogus sylvestris is about 10 by laser beams of three different frequencies.
It is a figure showing the result of having measured continuously over seconds.

FIG. 3 is a diagram showing a measurement result of a spectral reflectance when the present measurement device is fixed and a leaf of Ezonosekigishi, which is a measurement target, is moved at 10 cm / S while maintaining a fixed distance from the measurement head A. is there.

FIG. 4 is a diagram showing the principle of a conventional spectral reflectance measuring device.

FIG. 5 is a bottom view of the measuring head A ′.

[Explanation of symbols]

 A: Measurement head B: Controller P: Plant La-Lc: Laser light 1a-1c: Laser power supply 8: Light detection unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Masahiro Kamei 1-40-2 Nisshin-cho, Omiya City, Saitama Prefecture Within the Research Institute for Biological Sciences (72) Inventor Riki Okura 5-15 Ogikubo, Suginami-ku, Tokyo No. 14 Within Optics Research Co., Ltd. (72) Inventor Mikihiko Masada 2828 Natsumi, Nabari City, Mie Prefecture Inside Taka Kita Corporation (72) Inventor Katsumi Yamazaki 2828 Natsumi, Nabari City, Mie Prefecture Taka Kita Corporation

Claims (2)

[Claims] 1. A method in which a plurality of laser beams having different oscillation wavelengths are converted into light beams using a simple optical system such as a light dispersing element, the light beams are irradiated on a plant, and the reflected light is measured. A method for measuring the spectral reflectance of a plant, comprising determining the spectral reflectance of the plant. 2. An apparatus for irradiating a plant with a laser beam and measuring the spectral reflectance based on the reflected light, wherein the plurality of laser beams having different oscillation wavelengths are converted into light beams passing through substantially the same optical path. A measuring head for converting the magnitude of the reflected light into an electric quantity, and performing data processing of the electric quantity with respect to the reflected light obtained by the measuring head to thereby obtain a spectral reflection of the plant body. A controller for calculating a rate, and a spectral reflectance measuring device for a plant comprising: