Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V8/00—Prospecting or detecting by optical means
  • G01V8/10—Detecting, e.g. by using light barriers

Definitions

• the present invention relates to a method and a device for non-contact detection of plants.
• the device based on this method is characterized by an optical system for collecting reflected light from a surface, a beam splitter for dividing the reflected light into at least two light beams, an interference filter for each of said light beams for filtration thereof to a predetermined wavelength, a photodiode for each of said wavelengths for conversion thereof into an electric signal, an operational amplifier for each of said signals for amplification thereof, a divider for receiving said two signals and dividing them to provide a ratio signal, and a comparator for comparing said ratio signal with a preselected reference signal to provide an output signal indicating the presence/non-presence of a plant on said surface.
• Fig. 1 is an optical/electric block diagram illu ⁇ strating the mode of operation of the device
• FIG. 2 schematically illustrates one of many conceivable applications of the invention.
• Fig. 3 is a diagram showing the intensity of reflection as a function of the wavelength.
• the method and the device according to the inven ⁇ tion for non-contact "seeing" detection of plants are based on spectral signature.
• the detecting device is viewing two specific wavelengths in the reflection spectrum from the surface it is scanning at the moment. These two wavelengths have a characteristic intensity relation for plants, which is directly converted into the single output signal representing presence/non- presence of a plant or, shorter, plant/non-plant.
• the principle of detection is based on optical signature.
• the intensity relation between the wavelength 680 nm and 730 nm decides whether a plant should be indicated or not in the output signal of the detecting device.
• 680 nm is one of the wave ⁇ lengths of light which is heavily absorbed by the chlorophyll of the plant. The intensity of this wave- length therefore is very low in the reflection spectrum from a plant.
• 730 nm is a wavelength which the plant reflects very intensely. The intensity of this wave ⁇ length therefore is very high in the reflection spectrum from a plant.
• Fig. 3 is an example of this reflection spectrum from sugar beets or, more exactly, their tops.
• the detecting device As schematically shown in Fig. 1, the detecting device, generally designated 1, is enclosed in a dust and moisture-proof casing 2.
• the detecting device has a rotary scanner 3 with mirrors 4 sweeping the surface 5 to be detected.
• the light 6 reflected from the surface 5 is collected through the scanner 3 by an optical system 7.
• this optical system has a diaphragm device 8 with two lenses 9 and two lenses 10, as well as an aperture 11 displaced between these two pairs of lenses in the common focus thereof for eliminating stray light from the reflected light 6.
• the optical system 7 also has a collecting device 38 with two lenses 12 for receiving the light 6, freed from stray light, and conducting it to a beam splitter 13.
• the beam splitter 13 consists of a semi-reflecting mirror dividing the reflected light 6 into two light beams 14 and 15. Each of these two light beams 14 and 15, by a respective interference filter 16 and 17 of about 680 nm and about 730 nm, respectively, reaches a photodiode 18, 19 for conversion into electric signals 20, 21.
• the signals 20, 21 emitted by the photodiodes 18 ' and 19 are amplified each by an operational amplifier 22, 23 of the FET type having constant gain and, after further amplification 1,10 or 100 times by amplifiers 24, 25 adjustable in parallel, are both supplied to an analogue divider 26 in which the 680 nm signal is inserted in the numerator.
• the output or ratio signal 27 from the divider 26 will thus reach its minimum when the detecting device is viewing a plant.
• a comparator 28 compares the ratio signal 27 from the analogue divider with a preselected reference signal 29 for providing an output signal 30 indicating the presence/non-presence of a plant 31 on the surface 5.
• the output signals 30 from the detecting device 1 may in turn be used as control signals in order, by the ' intermediary of a microcomputer, to control different types of means for processing and/or treating the detected plant 31 or other plants spaced therefrom by a predetermined distance, or the area surrounding said plants.
• Fig. 2 shows one of many conceivable applications of the invention. More precisely, the detecting device 1 is here mounted on one side of a hoe 32 for hoeing row crops, for instance sugar beets 33.
• the hoe 32 is either drawn or carried by a tractor 34 and has a plurality of hoeing knives 35 for hoeing between the rows of crop 33. To prevent the soil loosened by the knives 35 from covering small plants, protecting discs 36 are used.
• the detecting device 1 is so disposed on the hoe 32 that it will be located straight above a row of crop 33 immediately to the right of the hoe, or midway between two rows.
• the hoe 32 is provided on either side with a steerable wheel 37.
• the wheels 37 are operably connected to and controllable by means of the detecting device 1.
• the detecting device 1 will detect this circumstance by sensing that the crop 33 is not located straight underneath the scanner 3, whereby the detecting device 1 emits a control signal to the operating mechanism for steering the wheels 37 in the direction required to return the hoe 32 to its correct lateral position.
• the optical detecting device 1 in principle is an optical transducer which by means of two optical filters and two photo ⁇ diodes discriminates between plant and non-plant.
• the transducer can be made more or less sophisti ⁇ cated with a scanner as illustrated and described, or a stationary mirror, depending on the field of application. If the information from the detecting device and other transducers, for instance a transducer indicating the distance travelled, is processed by a microcomputer and its program, many different appli ⁇ cations can be obtained.
• the scanner 3 of the detecting device 1 is scanning sideways trans ⁇ versely of the direction of travel of the tractor 34 and the hoe 32.
• the scanner 3 can also be arranged for scanning in the longitudinal or the vertical direction.
• the latter application may be advantageous, for instance when topping sugar beets, in which case the scanner 3 may operate such that the detecting device 1 detects where the tops begin on the beet. This information may then be used for controlling a topper assembly which will correctly top every beet.

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• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Geophysics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (5)

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Family Cites Families (2)

• 1984
  • 1984-06-25 SE SE8403364A patent/SE443050B/sv not_active IP Right Cessation
• 1985
  • 1985-06-24 WO PCT/SE1985/000261 patent/WO1986000420A1/en unknown
  • 1985-06-24 AU AU45479/85A patent/AU4547985A/en not_active Abandoned
  • 1985-06-24 EP EP19850903430 patent/EP0215795A1/en not_active Withdrawn
• 1986
  • 1986-02-25 DK DK86586A patent/DK86586A/da unknown

Non-Patent Citations (1)

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