SENSOR SYSTEM AND METHOD FOR DETERMINING AN OPTICAL PROPERTY OF A PLANT

• US 20130152464A1
• Filed: 02/12/2013
• Published: 06/20/2013
• Est. Priority Date: 08/13/2010
• Status: Active Grant

• Current Assignee: Franke GmbH
• Original Assignee: Franke GmbH
• Inventors: GROZ, Daniel, DITTMAR, Guenter
• Granted Patent: US 9,128,049 B2
• Time in Patent Office: Days
• US Class Current: 47/58.1LS
• CPC Class Codes: A01G 7/00 Botany in general
• CPC Class Codes: G01N 2021/8466 Investigation of vegetal material, e.g. leaves, plants, fruits
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

A sensor system for determining an optical property of a plant by means of a reflection measurement, having a first light source, which emits light along a first beam axis, and a second light source, which emits light along a second beam axis, and at least one receiver, which is aligned along a third beam axis, to detect light reflected from the plant. The first light source, the second light source, and the receiver are arranged relative to one another so that a target cylinder, which respectively extends along the first beam axis and the second beam axis, and a first measuring cylinder, which extends along the third beam axis, at least partially overlap one another in a measuring space, and the first beam axis and the second beam axis respectively enclose an angle (α, δ) with the third beam axis. Related methods are also disclosed.

Claims

1. A sensor system for determining an optical property of a plant by means of a reflection measurement, having a first light source, which emits light along a first beam axis, and a second light source, which emits light along a second beam axis, and at least one first receiver, which is aligned along a third beam axis, to detect light reflected from the plant, wherein the first light source, the second light source, and the at least one first receiver are arranged relative to one another in such a manner that a target cylinder, which respectively extends along the first beam axis and the second beam axis, and a first measuring cylinder, which extends along the third beam axis, at least partially overlap one another in a measuring space, and the first beam axis and the second beam axis respectively enclose an angle with the third beam axis, wherein the first light source emits light in a first wavelength range and the second light source emits light in a second wavelength range, wherein the first wavelength range is a wavelength range of green light, wherein the second wavelength range is a wavelength range of red light, wherein the first light source and the second light source are arranged in a first housing, and the at least one first receiver is arranged in a second housing, and wherein a fastening of the first light source and of the second light source and of the at least one first receiver is provided such that the angles between the beam axes of the light sources and the beam axis of the at least one receiver and a distance between the light sources and the at least one receiver can be adjusted.

2. A sensor system for determining an optical property of a plant by means of a reflection measurement, having a first light source, which emits light along a first beam axis, and a second light source, which emits light along a second beam axis, and at least one first receiver, which is aligned along a third beam axis, to detect light reflected from the plant, wherein the first light source, the second light source, and the at least one first receiver are arranged relative to one another in such a manner that a target cylinder, which respectively extends along the first beam axis and the second beam axis, and a first measuring cylinder, which extends along the third beam axis, at least partially overlap one another in a measuring space, and the first beam axis and the second beam axis respectively enclose an angle with the third beam axis.

3. The sensor system as claimed in claim 2, wherein a second receiver is provided, wherein the second receiver is aligned along a fourth beam axis in such a manner that a second measuring cylinder, which extends along the fourth beam axis, and the first measuring cylinder and the target cylinders at least partially overlap one another in the measuring space, and the first beam axis and the second beam axis respectively enclose an angle with the fourth beam axis.

4. The sensor system as claimed in claim 2, wherein the first light source and the second light source are arranged in a first housing, and the at least one first receiver is arranged in a second housing.

5. The sensor system as claimed in claim 2, wherein the first light source emits light in a first wavelength range and the second light source emits light in a second wavelength range.

6. The sensor system as claimed in claim 5, wherein each receiver has an optical bandpass filter, which is transmissive for light of the first wavelength range and/or of the second wavelength range.

7. The sensor system as claimed in claim 5, wherein the first wavelength range is a wavelength range of green light and the second wavelength range is a wavelength range of red light.

8. The sensor system as claimed in claim 2, wherein the light emitted by the first light source and by the second light source is modulated with a constant modulation frequency and the at least one first receiver preferably detects the modulation frequency.

9. The sensor system as claimed in claim 2, wherein the first light source and the second light source each emit light pulsed in a constant frequency, wherein the frequencies are different from one another, wherein the at least one first receiver analyzes signals which have the frequency.

10. The sensor system as claimed in claim 2, wherein the first beam axis and the second beam axis are not congruent.

11. The sensor system as claimed in claim 2, wherein the first beam axis and the second beam axis are congruent.

12. The sensor system as claimed in claim 3, wherein the third beam axis and the fourth beam axis are not congruent.

13. The sensor system as claimed in claim 2, wherein a fastening of the first light source and of the second light source and of the at least one first receiver is provided such that the angles between the beam axes of the light sources and the beam axis of the at least one receiver and a distance between the light sources and the at least one receiver can be adjusted.

14. The sensor system as claimed in claim 2, wherein the target cylinder of the first light source and the target cylinder of the second light source in the measuring space each have a diameter of approximately 1 mm to approximately 6 mm, wherein the measuring cylinder of the at least one receiver in the measuring space has a diameter of approximately 8 mm.

15. The sensor system as claimed in claim 2, wherein the sensor system has an acoustic signal generator to output a measurement result.

16. A method for determining an optical property of a plant by means of a reflection measurement, wherein light in a first wavelength range is emitted along a first beam axis by means of a first light source, and light in a second wavelength range is emitted along a second beam axis by means of a second light source, wherein light reflected from the plant is detected by at least one first receiver, which is aligned along a third beam axis, wherein the first light source, the second light source, and the at least one first receiver are arranged relative to one another in such a manner that a target cylinder, which respectively extends along the first beam axis and the second beam axis, and a first measuring cylinder, which extends along the third beam axis, at least partially overlap one another in a measuring space, and the first beam axis and the second beam axis respectively enclose an angle with the third beam axis.

17. A method for analyzing a measurement to determine an optical property of a plant, having the following steps:

detecting a value pair, which has a spectral reflection coefficient of the plant in a green wavelength range ρ

<sub>grü

n</sub> and a spectral reflection coefficient of the plant in a red wavelength range ρ

_rot, and further conducting one of the following steps a) to c);

determining a normalized logarithmic vegetation index ln NDVI_Blatt by means of the following equation;

ln NDVI_Blatt=ln(ρ

<sub>grü

n</sub>−

ρ

_rot)−

ln(ρ

_rot),

wherein the value pair is discarded at least if the term ln(ρ

<sub>grü

n</sub>−

ρ

_rot) cannot be determined, and ln NDVI_Blatt is calculated if the term ln(ρ

<sub>grü

n</sub>−

ρ

_rot) can be determined;

determining a normalized vegetation index A_Q by means of the following equation;