CN103674855B - Optical path system used for monitoring crop growth information - Google Patents

Abstract

An optical path system for crop growth information monitoring, which is characterized in that it includes an autonomous light source system, a two-way spectral signal acquisition system and an accurate height measurement system; the two-way autonomous light source system, two-way spectral signal acquisition systems and a set of accurate The height measurement systems are all located in the vertical position, and the three systems form a linear structure. The two autonomous light source systems respectively generate two waveband modulated light signals of 730nm and 810nm to irradiate the leaves of the crop canopy. The precise height measurement system is simple, fast and Intuitively determine the measurement height of the monitoring device and the crop canopy. The self-contained light source system of the present invention adopts central band LEDs and adopts a uniform mixed arrangement, and the output light signal of the light source has good uniformity and high monitoring precision; Small external optical signal interference, improve effective signal-to-noise ratio; few and simple optical components, simple processing, and low cost.

Description

An optical path system for crop growth information monitoring

technical field

The invention belongs to the field of intelligent detection of crop growth information, and is specially used for real-time, accurate, convenient and non-destructive acquisition of farmland crop growth information. It relates to an optical path system for monitoring crop growth information, in particular to an optical path system for non-destructive monitoring of crop growth information based on active light sources.

Background technique

At present, the real-time, fast and non-destructive acquisition of field crop growth information can provide data support for the precise management of field crops. Traditional field crop sampling, drying samples, and chemical analysis methods to obtain crop growth information have the disadvantages of time-consuming, expensive, and destructive, and can only be analyzed and processed in specific professional laboratories. The professional requirements for experimenters strict. With the rapid development of hyperspectral technology, non-destructive monitoring technology based on spectral characteristics has been widely used in ore detection, land and resources survey, lake water quality detection and agricultural remote sensing and other fields.

The non-destructive monitoring technology based on spectral characteristics mainly includes two devices based on passive light source and active light source. Based on the passive light source, that is, sunlight is used as the light source. Existing devices that use passive light sources include the FieldSpec4 back-mounted surface object spectrometer produced by the American ASD company, the FieldSpec HandHeld2 handheld surface object spectrometer, and the SpectroSense2 surface plant spectrometer produced by the British SKYE company. Since the sunlight stability is easily affected by the weather, the accuracy of the monitoring results is often low; based on the active light source, the autonomous light source technology is used to eliminate the influence of sunlight instability, thereby greatly improving the accuracy and stability of the monitoring results. Existing devices using active light sources such as the Crop Circle ACS-470 handheld spectrometer grown by Holland Scientific in the U.S. and the GreenSeeker handheld spectrometer produced by GreenSeeker in the U.S.

Chinese patent 201310180901.9 discloses an active light source type crop canopy reflection spectrum measurement device and method, and proposes a method for spectral reflection measurement of canopies of different scales, but the accuracy of the monitoring results is limited due to the divergence characteristics of the light emitted by the light source There is no relevant report on the detailed design of the optical path system.

The National Agricultural Informatization Engineering Technology Research Center has developed a normalized difference vegetation index (NDVI) measurement system based on active light sources, and proposed the design method of its optical path system, but there are no relevant reports on its structural design and specific implementation.

The design of optical path system is the key technology of non-destructive monitoring device for crop growth information based on active light source. In the design of a non-destructive monitoring device for crop growth information based on active light sources, the energy of active light sources is much smaller than that of sunlight, so it cannot be directly measured by light sensor.

Therefore, it is necessary to design a specific optical path structure, perform corresponding concentrating operations on the output of the light source, and adopt corresponding concentrating and filtering operations on the collected reflected light, so that the output spectrum is convenient for processing and analysis by subsequent devices.

Contents of the invention

The purpose of the present invention is to provide an optical path system for crop growth information monitoring with high monitoring accuracy, no mechanical movement, stable performance, and not restricted by weather factors. The optical path system can realize the real-time and accurate acquisition of reflected light intensity in sensitive bands of crop canopy characteristics. It adopts the standard reflectance correction method and couples the crop canopy spectral data-growth information model to realize the non-destructive monitoring of crop growth information. Precise management regulation provides a source of data.

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized through the following technical solutions:

An optical path system for crop growth information monitoring, characterized in that it includes an autonomous light source system, a two-way spectral signal acquisition system and an accurate height measurement system; the output light of the autonomous light source system 2 illuminates the monitored crop canopy leaves 4, The spectral signal acquisition system 3 collects the reflected light signal of the measured crop canopy blade 4 to the outgoing light of the autonomous light source system 2; the two-way spectral signal acquisition system 3 and a set of accurate height measurement system are all located in a vertical position, and the three systems constitute linear structure,

The autonomous light source system includes an LED array 5, a first lens 7, a second lens 8 and a protective glass 9; the LED array 5 generates approximately parallel light, and the emitted light passes through the first lens 7, the second lens 8 and the protective glass 9 respectively.

The LED array 5 is composed of LED10 with a center wavelength of 730nm and LED11 with a center wavelength of 810nm, each with 13 LEDs 6 uniformly mixed and arranged in two rows, which can produce a uniform mixed spectrum of 730nm and 810nm, wherein the diameter of a single LED 6 is 3mm .

The first lens 7 and the second lens 8 are strip convex lenses, the size of the first lens 7 is 20mm*40mm, the size of the second lens 8 is 10mm*40mm, the right focus of the first lens 7 and the second lens 8. The left focal points overlap, and the output light of the second lens 8 is a strip beam.

The structure of the two-way spectral signal acquisition system is the same, and both include a third lens 15, a specific central wavelength filter 14 and a photodetector array 12; along the incident light path, pass through the third lens 15, the filter 14 and the photoelectric detector array 12 .

The third lens 15 is a circular convex lens with a diameter of 25.5 mm, a thickness of 10 mm, and a focal length of 25 mm.

The central wavelengths of the optical filters 14 are 730nm and 810nm respectively, and the bandwidths are both 10nm.

The photodetector array is a photodiode array composed of six photodiodes 13 in three rows and two columns. The photodetector array 12 is placed at the focal point of the third lens 15, and the diameter of a single photodiode is 3 mm.

The precise height measuring system comprises two red miniature laser lamps 17 and a housing 18; the housing 18 is used to fix the two laser lamps;

The two red miniature laser lamps 17 are identical, and the output light is in the shape of red dots. The distance L16 between the two laser lamps is fixed, and the angle θ19 between the light emitted by the laser lamps 17 and the horizontal direction is fixed, so as to ensure that the instrument is at a fixed measurement height. When H is 20, the exit spots 21 of the two laser lamps overlap.

Beneficial effects of the present invention:

1. An optical path system for crop growth information monitoring of the present invention uses a specific central wavelength LED array as a light-emitting component; the specific central wavelength LED array has the characteristics of easy modulation, high luminous intensity, and good spectral uniformity and stability.

2. An optical path system for crop growth information monitoring of the present invention adopts a combined lens mode in which the first lens and the second lens are combined; the light emitted by the LED array can form a spectrum with good uniformity and high light intensity after passing through the combined lens. The strip modulated light can effectively improve the signal-to-noise ratio and stability of the optical signal received by the spectral signal acquisition system.

3. An optical path system for crop growth information monitoring of the present invention uses a specific central wavelength filter as a spectral band selection component; the specific central wavelength filter can effectively remove non-specific central wavelength optical signals in the incident light, preventing Photodetectors cannot convert effective modulation spectrum signals due to light saturation, and can effectively remove high-frequency electromagnetic wave interference signals in optical signals.

4. An optical path system for crop growth information monitoring of the present invention uses a photodiode array as a photodetector; the photodiode has the characteristics of good frequency characteristics, high sensitivity, low noise, and high photoelectric conversion efficiency, which can effectively ensure the optical path system. stability and reliability.

5. An optical path system for crop growth information monitoring of the present invention adopts an accurate height measurement method with double laser spot overlap; the precise height measurement system with double laser spot overlap can meet the specific requirements of the crop canopy, and is intuitive, simple, Good accuracy and so on.

Description of drawings

Fig. 1 is a structural schematic diagram of an optical system for crop growth information monitoring according to the present invention.

Fig. 2 is a schematic structural diagram of the autonomous light source system in the optical system for crop growth information monitoring according to the present invention.

Fig. 3 is a schematic structural diagram of a spectral signal acquisition system in the optical system for crop growth information monitoring according to the present invention.

Fig. 4 is a structural schematic diagram of the precise altimetry system in the optical path system for crop growth information monitoring according to the present invention.

In the figure: 1. Laser height measurement system, 2. Autonomous light source system, 3. Spectral signal acquisition system, 4. Crop canopy leaves, 5. LED array, 6. Single LED, 7. First lens, 8. Second Lens, 9. Protective glass, 10. LED with center wavelength 730nm, 11. LED with center wavelength 810nm, 12. Photodiode array, 13. Single photodiode, 14. Optical filter, 15. Third lens, 16 . Distance L between two laser lamps, 17. Laser lamp, 18. Shell, 19. Angle θ between laser light emitting light and horizontal direction, 20. Measuring height H, 21. Two laser light emitting light overlapping spot.

detailed description

In order to better implement and understand the present invention, the present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, an optical path system for crop growth information monitoring includes an autonomous light source system, a two-way spectral signal acquisition system and an accurate altimetry system; the output light of the autonomous light source system 2 irradiates the monitored crop canopy leaves 4 , the spectral signal acquisition system 3 collects the reflected light signal of the measured crop canopy leaves 4 to the light emitted by the autonomous light source system 2, and the precise height measurement system 1 simply, quickly and intuitively determines the measurement height of the monitoring device and the crop canopy. Two spectral signal acquisition systems and a set of precise altimetry system are located in the vertical position, and the three systems form a linear structure.

As shown in Figure 2, the autonomous light source system includes a specific central wavelength LED array 5, a first lens 7, a second lens 8 and a protective glass 9; the specific central wavelength LED array 5 produces approximately parallel light, and the outgoing light passes through the first lens 7 respectively , the second lens 8, a protective glass 9, the protective glass 9 is used to protect the lens from physical and chemical damage.

As shown in Figure 2, the LED array (5) with a specific central wavelength is composed of LEDs (10) with a central wavelength of 730nm and LEDs (11) with a central wavelength of 810nm, each of which is composed of 13 LEDs 6 evenly mixed in two rows, and can be arranged in two rows. A homogeneous mixed spectrum of 730nm and 810nm is produced, wherein the diameter of a single LED (6) is 3mm.

The first lens 7 and the second lens 8 are strip convex lenses, the size of the first lens 7 is 20mm*40mm, the size of the second lens 8 is 10mm*40mm, the right focus of the first lens 7 and the second lens 8. The left focal points overlap, and the output light of the second lens 8 is a strip beam.

As shown in Fig. 3, the structures of the two-way spectral signal acquisition systems are the same, all comprising a third lens 15, a specific center wavelength filter 14 and a photodetector array 12; wavelength filter 14 and photodetector array 12.

The third lens 15 is a circular convex lens with a diameter of 25.5 mm, a thickness of 10 mm, and a focal length of 25 mm.

The central wavelengths of the specific central wavelength filters 14 are 730nm and 810nm respectively, and the bandwidths are both 10nm.

As shown in Fig. 3, the photodetector array is a photodiode array composed of 6 photodiodes 13 in three rows and two columns. The photodetector array 12 is placed at the focal point of the third lens 15, and the diameter of a single photodiode is 3 mm.

As shown in Figure 4, the precise height measurement system includes two red miniature laser lamps 17 and a housing 18; the housing 18 is used to fix the two laser lamps;

The two red miniature laser lamps 17 are identical, and the output light is in the shape of red dots. The distance L16 between the two laser lamps is fixed, and the angle θ19 between the light emitted by the laser lamps 17 and the horizontal direction is fixed, so as to ensure that the instrument is at a fixed measurement height. When H is 20, the exit spots 21 of the two laser lamps overlap.

The working principle of the optical path system of the present invention is as follows:

The 730nm and 810nm band spectra are the sensitive bands of the crop canopy leaves, and the reflection spectra of the crop canopy leaves to the 730nm and 810nm band spectra are loaded with the internal structure and component information of the crop canopy leaves. By detecting the 730nm and 810nm spectral reflection information can retrieve crop growth information.

The pre-stage modulation circuit generates a modulation signal with a fixed frequency to control the LED drive circuit to light up the LED with a specific center wavelength. The first lens, the second lens and the protective glass irradiate the leaves of the crop canopy.

The first lens plays the role of concentrating light, gathering the spectral signal generated by the LED with a specific central wavelength as much as possible, and improving the intensity of the outgoing light of the light source system; the second lens plays the role of light collimation, and the spectral signal gathered by the first lens It is adjusted to a parallel light signal to improve the utilization rate of the spectral signal output by the autonomous light source.

The spectral signal acquisition system receives the reflected spectral signals of the crop canopy leaves on the 730nm and 810nm bands, and the reflected spectral signals of the 730nm and 810nm bands respectively pass through the third lens and a specific central wavelength filter, and the central wavelength is 730nm or 810nm, which is detected by photoelectricity The signal collected by the sensor is converted into an electrical signal, and the reflectance spectrum information of the leaves of the crop canopy to 730nm and 810nm is obtained after processing by the post-stage circuit. Because the output spectral signal intensity of the autonomous light source is constant, the reflectance of the crop canopy leaves to the 730nm and 810nm spectra is obtained through modeling, and the canopy reflectance spectral information-crop growth information monitoring model is fused to obtain the crop growth information.

The intensity of the spectral signal generated by the autonomous light source is limited, and the change of the measured height will affect the collection of reflection spectral information by the spectral signal collection system. Therefore, the present invention adopts a fixed-height collection method. Due to the particularity of the crop canopy, the present invention adopts a double laser overlap method; the distance L between the two laser lamps is constant, and the exit angle θ is constant, according to Only at height H as:

The light spots emitted by the two laser lights can overlap to form a light spot, so that the monitoring of crop growth information at a fixed height can be realized simply and intuitively.

Claims (1)

1. An optical path system for crop growth information monitoring, characterized in that it includes an autonomous light source system, a two-way spectral signal acquisition system and an accurate height measurement system; the output light of the autonomous light source system (2) irradiates the monitored crop canopy Layer leaves (4), the spectral signal acquisition system (3) collects the reflected light signal of the measured crop canopy leaf (4) to the light emitted by the autonomous light source system (2); two spectral signal acquisition systems (3) and one The sets of precise height measuring systems are located in vertical positions, and the three systems form a linear structure; the autonomous light source system includes an LED array (5), a first lens (7), a second lens (8) and a protective glass (9); The LED array (5) produces approximately parallel light, and the outgoing light passes through the first lens (7), the second lens (8) and the protective glass (9); the LED array (5) is composed of LEDs with a center wavelength of 730nm ( 10) LEDs (11) with a center wavelength of 810nm are composed of 13 LEDs (6) uniformly mixed in two rows, which can produce a uniform mixed spectrum of 730nm and 810nm, wherein the diameter of a single LED (6) is 3mm; The first lens (7) and the second lens (8) are strip convex lenses, the size of the first lens (7) is 20mm*40mm, the size of the second lens (8) is 10mm*40mm, the first lens (7) The right focus of the second lens (8) coincides with the left focus of the second lens (8), and the output light of the second lens (8) is a strip beam; the structure of the two spectral signal acquisition systems is the same, including the third lens (15), a specific center A wavelength filter (14) and a photodetector array (12); along the light incident light path, passing through the third lens (15), the filter (14) and the photodetector array (12); the third lens ( 15) is a circular convex lens with a diameter of 25.5mm, a thickness of 10mm, and a focal length of 25mm; the central wavelengths of the filters (14) are 730nm and 810nm respectively, and the bandwidths are both 10nm; the photodetector array is selected from A photodiode array composed of 6 photodiodes (13) in three rows and two columns, the photodetector array (12) is placed at the focal point of the third lens (15), and the diameter of a single photodiode is 3 mm; the precise height measuring system It includes two red miniature laser lamps (17) and a housing (18); the housing (18) is used to fix the two laser lamps; the two red miniature laser lamps (17) are identical, and the output light is in the form of red dots , the distance (16) between the two laser lamps is fixed, and the angle (19) between the emitted light of the laser lamp (17) and the horizontal direction is fixed, so as to ensure that when the instrument is at a fixed measurement height (20), the emitted light spots (21) of the two laser lamps coincide.