Arrangement for the contactless determination of vegetation in a field

0001The invention relates to a device according to the The preamble of claim 1.

0002Such devices are described in the literature in many described manner or known in practice.

0003The field of application of this device is substantially in agriculture and environmental protection. To this Apparatus are provided the requirements, a Distinction to make between soil and plants. For this purpose, a sensor system for this distinction used.

0004The sensor system is a distinction between the ground and make verdure. This system can be used as part of a targeted weed control. on large Brownfields would be injected where actually Weeds were present.

0005The biggest drawback of the systems used to date is in the high price. This is mainly due to the use expensive concluded bandpass filter. These filters are needed, the sensors (photodiodes) for a discrete to raise awareness of the spectrum.

0006The principle is based on the distinction between soils and plants on the fact of the different behavior in the area the electromagnetic radiation from 450 nm to 950 nm, such as this is gargestellt in FIG. 1.

0007In the IR region (from 750 nm) radiation is a Corn plant and very strong in the area around the 550 nm less highly reflective. Between 650 and 700 nm and at a Wavelength less than 500 nm, however, most of the Radiation absorbed. The reflectance behavior of a corn plant is typical of the qualitative reflection behavior of verdure.

0008The reflective properties of the plant is from the current physiological and phenological state of plants dependent, in the visible wavelength range (400 nm-700 nm) of mostly pigment content (especially chlorophyll a + b, Carotenoids, xanthophyll) affects the reflection. in the Range from 700 nm to 3000 nm, the water content crucial for reflection.

0009Rule of thumb: The more vigorous vegetation, the higher of the pigment and water content, the higher the absorption in the visible and short-wave infrared range.

0010The reflection from the ground on the other hand runs over a very wide spectral range only weakly increasing linearly. Also Here the qualitative course is in different types of soil nearly equal. For the floor, the higher the humidity the lower the reflected portion.

0011For a distinction between the soil and plants is the Principle of quotients applied. From Fig. 1 Reflective properties of soil and corn plants in Range 450-950 nm can be clearly seen that in the The wavelength range from about 600 to about 700 nm plants less reflective than the ground. From about 700 nm to about 950 nm instead reflect plants stronger than Earth. To a reliably distinguishing between plants and soil to reach, it is not enough, only a wavelength range to record and evaluate the measured values. The maxima and Minima vary in size depending on the plant. Also the Reflections of the soil samples exhibit quantitative differences on. In addition, a change in intensity (eg would Ambient light) directly responds to the measured value influence. Becomes However, the ratio of two significant formed wavelength ranges, so is the result of the absolute values ​​independently. The use of suitable Wavelengths for the quotient formation therefore enables a reliable differentiation of plants and soil. The significant wavelengths are selected such that at least at one of the selected spectral regions the Characteristics of the soil and plants is sufficiently strong differ.

0012The quotient is the example of the relationship Education 670 and 750 nm are illustrated with the wavelengths. Plants and soil are a source of light in from above Workspace with the same intensity irradiated. The reflected radiation is recorded by sensors. On Sensort share) takes the reflected radiation at 670 nm, on the other at 750 nm. The quotient is independent of the absolute intensity of illumination, as long as the useful signal des.Sensors is sufficiently large. By forming the ratio of the respective outputs of the two detectors, one obtains the corresponding Quotient. From this, derive a statement as to whether a Plant or soil is detected.

0013Optoelectronic Systems for weed detection and targeted control offered since 1992 practice and are now in at least two variants of the Use in orchards, on railway embankments or on fallow land available.

0014Use on fallow land showed in experiments in USA and Australia high potential savings of 70 to 90% with the same high success rate. In the Netherlands services attempts in a communal area Spray savings of an average of 57%.

0015The invention is based on the object, with as inexpensive sensor systems and a high Function capability, an optical sensor system for soil / plant identification to accomplish.

0016This object is achieved by the fact that the Light source is at least one light emitting diode. By Using the sensors and the selection of suitable LEDs can be readily further combinations of Spektralbreichen for soil / plant discrimination in Should be considered. Good measurement results can be be achieved if several LEDs are provided, which are arranged around the sensor. The sensors have the wavelength sensor, a three color sensor be formed. Here, preferably, can be provided That the three-color sensor be associated with an IR Blocker is.

0017To a higher radiation intensity and safer beam level to get to the receiver, the LED in pulse mode are used. This will send the LEDs light in pulsed out manner.

0018An advantageous arrangement of light source and sensor results by the fact that the light source and the sensor as Assembly are formed.

0019In some cases it may be useful to the LEDs for different wavelength ranges are provided.

0020Furthermore, it is possible that the sensor for different having wavebands receiving diodes.

0021The signals received from the sensors to evaluate can is, provided that the light source and the sensor are connected to an electrical evaluation unit, in which an evaluation to determine the is stored plant cover of the box section.

0022Outstanding value allows the sensor unit characterized Manufacture that the sensors without additional filter Use for a limited spectral range are sensitized.

0023To dispense with the use of filters, come the approaches described in the following into consideration.

0024As emitters (illumination) are, like FIG. 2, sources in consideration, the narrow-band in a wavelength range emitting electromagnetic radiation (eg light emitting diodes).

0025The LEDs 1 and 2 are used in pulsed operation to to achieve a higher radiation intensity and safe to receive signal level at the receiver (eg photodiode) (sensor lighting unit). At the moment the lighting needs of Signal level of the reflected radiation by Soil / plant arises, be queried. The LEDs 1 and 2 consist of light-emitting diodes of different Spectral emissions. The light emitting diodes 1 and 2 are annular arranged as a light-emitting rings. 3 Within the LEDs ring 3 is of a wavelength sensor or Three color sensor configured sensor 4 for receiving the Reflection of the bottom 5 and 6 plants located.

0026Likewise, the level of reflectivity when switched measured by the photodiodes lighting (ambient light fraction). Through software-subtraction of both signal levels the external light is elemeniert. The pulsing of the LED's 1 and 2 ensures independence from ambient light.

0027come For measurements to soil / plant differentiation different spectral ranges into consideration (after Reflection behavior soil / plant), with the corresponding Light emitting diodes (intensity range) may be covered.

0028As a receiver coming sensors 4 are used, which, without additional filter insert for a limited Spectral sensitized. FIG. 3 shows an example of a complete system for soil and 5 Plant identification. 6

0029In the flowchart of FIG. 6 is the measurement and Evaluation process represented.

0030Further details of the invention are the other Dependent claims, the description and the example refer drawings. show Here<dl tsize="6"><dt>Fig. 1</dt><dd>the reflective properties of soil and Maize plants in the range 450-950 nm,</dd><dt>FIG. 2</dt><dd>the arrangement of a sensor lighting unit,</dd><dt>Fig. 3</dt><dd>the block diagram of the overall switching system,</dd><dt>Fig. 4</dt><dd>the practical implementation of the new system and </dd><dt>Fig. 5</dt><dd>an example of the chronological sequence of a Measurement cycle using a .mu.C and a Transimpendanzverstärkers.</dd></dl>

0031By using special sensors 4 and the insert the light emitting diodes 1, 2 is thus a higher selectivity reached.

0032FIG. 4 shows a schematic representation of the practical Realization of the system.

0033In Fig. 5 are sufficient times for transient provided arising from the amplifiers used.

0034The following new developments that this sensor system from other differs:

0035New is primarily the use of two sensors 4 - without additional filtering only in certain are sensitive wavelength ranges.

0036These special sensors 4 are with a pulsed Combined light source 1, 2, which in turn only in a discrete spectral radiation emitted. This brings the advantage of higher selectivity and thus better Results in the differentiation with respect to the ground. and the plant. 6

0037In the flowchart of FIG. 6 is the measurement and Evaluation process represented.

0038Fig. 7 shows the schematic construction of the Wavelength sensor SSO WS-7-56 Fa. Silicon Sensor. at the wavelength sensor Fa. Silicon Sensor is I to the type-SSOWS 7:56 to5. There is a sensor in which on a common silicon substrate two vertical pn Transitions are realized.

0039The upper diode (LED 1) is most sensitive in the range at 550 nm with a bandwidth of ~ 400-900 nm. Bandwidth of the lower diode (diode 2) is in the range of ~ 550 -.> 1000 nm Maximum sensitivity is here ~ 900 nm. The sensitivity curve of the wavelength sensor is in the range of 400 ... 1000 nm.

0040The wavelength sensor is for monochromatic light optimizes and gives the best results when perpendicular incident radiation.

0041Furthermore, the not shown three-element color sensor MCS3AT (without IR filter) and MCS3BT (with IR filter) Fa. MAZeT be used. These are three Silicon PIN photodiodes are integrated on a chip. Each of these diodes is standing dielectric by a Color filter for a particular wavelength range sensitized.

0042The color filters used reflect the locked Wavelength ranges, this also increases the Aging resistance of the filter.

0043For optimal function of the color sensor is the manufacturer an IR Blocker recommended. The reason lies in the Transmittance of each color filter for dielectric IR radiation. This transmitted radiation has direct Influence on the underlying diode, ie there is a Influencing instead of diode signals. in the Sensitivity range with IR blocker, the spectrum larger 720 nm cut off.