APPARATUS AND METHOD FOR DETERMINING A DISTANCE TO AN OBJECT IN A FIELD

APPAREIL ET PROCEDE POUR DETERMINER LA DISTANCE D'UN OBJET SITUE DANS UN CHAMP

English Abstract

An optical proximity sensor (1) generates information indicative
of a distance (DI) to an object (14A) in a field and in some embod-
iments also generates information indicative of a spectral reflectance
characteristics of the object (14A). The information indicative of the
spectral reflectance characteristic can be used to determine whether the
object (14A) in the field is a living plant (14A) or another object such
as soil (10). Light emitted from the optical sensor (1) for reflection off
the object (14A) is modulated so that reflected light from the optical
sensor can be discriminated from reflected ambient sunlight. The opti-
cal sensor (1) is scanned over the field to map objects in the field and/or
to determine the location of rows of crop plants. A sensor in accor-
dance with the present invention has many uses in agriculture including
spraying, cultivation and vehicle guidance.

French Abstract

Détecteur optique (1) de proximité produisant des informations indiquant la distance (D1) d'un objet (14A) présent dans un champ et dont des variantes produisent en outre des informations fonction d'une caractéristique du spectre réfléchi par l'objet (14A) et permettant de distinguer si l'objet (14A) se trouvant dans le champ est une plante vivante (14A) ou un autre objet tel que de la terre (10). La lumière émise par le détecteur optique (1) pour être réfléchie par l'objet (14A) est modulée, ce qui permet de la différencier de la lumière solaire ambiante réfléchie. Le détecteur optique (1) effectue un balayage du champ pour en inventorier les objets et/ou y localiser les rangées de plantes de culture; il présente de nombreuses applications en agriculture et peut notamment servir pour l'épandage, les travaux de culture et le guidage de véhicules.

Claims

CLAIMS:
1. A method of generating information about objects
in a field, comprising:
moving a source of light and a light detector with
respect to the objects, said source of light emitting
modulated light which reflects off said objects;
filtering a signal output from said light detector
thereby discriminating components of said signal due to said
modulated light which reflects off said objects from
components of said signal due to ambient light; and
generating information indicative of distances to
said objects and information indicative of whether said
objects are living plants.
2. The method of Claim 1, wherein said ambient light
is sunlight.
3. A method of generating information about an object
in a field, comprising:
moving a sensor with respect to the object, said
sensor comprising a source of light and a light detector,
light from said source of light scanning over said object
and light from said source of light reflecting off said
object and being incident upon said light detector of said
sensor, said light reflecting off said object causing a
signal to be output from said light detector of said sensor;
using a signal output from said light detector of
said sensor to obtain distance information, said distance
information being indicative of a distance between said
sensor and said object when said light from said source is
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reflecting off said object; and
using a signal output from a light detector
of said sensor to determine a spectral reflectance
characteristic of said object, said spectral
reflectance characteristic being indicative of
whether said object is a living plant.
4. The method of Claim 3, wherein said source of
light comprises a light emitting diode.
5. The method of Claim 3, wherein said light
which reflects off said object is incident upon a first
portion of said light detector but not on a second
portion of said light detector if said object is
disposed a first distance from said sensor, and wherein
said light which reflects off said object is incident
upon said second portion of said light detector but not
on said first portion of said light detector if said
object is disposed a second distance from said sensor.
6. The method of Claim 5, wherein said source of
light outputs a first amount of substantially
monochromatic light of a first wavelength and a second
amount of light of substantially monochromatic light of
a second wavelength, said first amount of light being
modulated with a first modulation signal, said second
amount of light being modulated with a second
modulation signal.
7. The method of Claim 6, wherein said first
modulation signal is phase shifted with respect to said
second modulation signal.
8. The method of Claim 5, wherein said object is
a tree and wherein said light from said source of light
travels in a substantially horizontal direction toward
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said tree when said source of light is moved with
respect to said tree.
9. The method of Claim 5, wherein said light from
said source of light travels in a substantially
vertical direction toward said object when said source
of light is moved with respect to said object.
10. The method of Claim 5, further comprising:
using said spectral reflectance
characteristic to map objects in said field.
11. The method of Claim 5, further comprising:
using said distance information to map
objects in said field.
12. The method of Claim 5, further comprising:
storing in a data storage device information
indicative of locations of a plurality of objects
in said field, said data storage device being
coupled to said sensor.
13. The method of Claim 5, further comprising:
using said spectral reflectance
characteristic to control a valve, pump or
injector.
14. The method of Claim 5, further comprising:
using said spectral reflectance
characteristic to guide a vehicle or implement
through said field.
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Description

CA 02193837 2006-09-01
78959-2
APPARATUS AND METHOD FOR DET'ERMINING A DISTANCE
TO AN OBJECT IN A FIELD
FIELD OF THE INVENTION
The present invention rel.ates to the optical
detection of objects. More particularly, the present
invention relates to determining di.stances to objects such
as plants and soil in a field.
BACKGROUND INFORMATION
Numerous applications exist in agriculture for
sensors capable of detecting characteristics of objects
present in the field. One example of such an application,
which is presented only for illustrative purposes here,
involves orchard management. In order to control pests,
chemical insecticides are applied t:o orchard trees using a
sprayer attached to a vehicle such as a tractor. Due to the
high cost of such insecticides and due to the potential
adverse impact such insecticides may have on the
environment, it is desirable to miriimize the use of such
insecticides. If individual trees in the rows of an orchard
could be discriminated from the spaces between the trees,
then a sprayer proceeding through the orchard between two
rows of trees could be controlled to apply insecticide onto
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W096/02817 PCTlUS95IO$Z37 =
2193837
the trees and not to waste insecticide by spraying
insecticide into the spaces between trees.
In an attempt to meet this need, sonar technology
has been used. When a sonar transducer of a sonar-
controlled orchard sprayer senses that a tree is in
close proximity to the sprayer, the sprayer is
energized and insecticide is sprayed onto the tree.
Otherwise, the sprayer is not energized and the
insecticide that otherwise would have been sprayed into
the spaces between trees is preserved.
This sonar technology, however, has fundamental
limitations. Sonar sprayers often fail to discriminate
between sonar reflections off objects and ambient
acoustic interference. Accordingly, it is common for
sonar-controlled sprayers to energize when no tree is
in fact present. Moreover, sonar-controlled sprayers
are typically unable to discriminate between living
trees and other objects such a buildings, vehicles,
power poles and people. The sprayer may therefore
waste insecticide by spraying non-tree objects like
barns. Such systems also present a safety hazard
because a sonar-controlled sprayer may mistake a person
for a tree and spray the person with insecticide. A
need therefore exists for a proximity sensor which is
capable of discriminating trees from other objects
which should not be sprayed.
SUIM_MARg
An optical sensor generates information indicative
of a distance to an object in a field and in some
embodiments also generates information indicative of a
spectral reflectance characteristic of the object. The
information indicative of the spectral reflectance '
characteristic can be used to determine whether the
object in the field is a living plant or another object
such as soil. Light emitted from the optical sensor
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CA 02193837 2006-09-01
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for reflection off the object is modulated so that reflected
light from the optical sensor can be discriminated from
reflected ambient sunlight.
According to one aspect the invention provides a
method of generating information about objects in a field,
comprising: moving a source of light and a light detector
with respect to the objects, said source of light emitting
modulated light which reflects off said objects; filtering a
signal output from said light detec:tor thereby
discriminating components of said signal due to said
modulated light which reflects off said objects from
components of said signal due to antbient light; and
generating information indicative of distances to said
objects and information indicative of whether said objects
are living plants.
According to another aspect the invention provides
a method of generating information about an object in a
field, comprising: moving a sensor with respect to the
object, said sensor comprising a sc>urce of light and a light
detector, light from said source of light scanning over said
object and light from said source of light reflecting off
said object and being incident upori said light detector of
said sensor, said light reflecting off said object causing a
signal to be output from said light: detector of said sensor;
using a signal output from said licfht detector of said
sensor to obtain distance informati.on, said distance
information being indicative of a distance between said
sensor and said object when said li_ght from said source is
reflecting off said object; and using a signal output from a
light detector of said sensor to determine a spectral
reflectance characteristic of said object, said spectral
reflectance characteristic being iridicative of whether said
object is a living plant.
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CA 02193837 2006-09-01
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A sensor in accordance with the present invention
sees many applications in agriculture including:
controlling spray nozzles to spray only plants with
herbicide and not to spray substantial areas of bare ground
thereby conserving herbicide, controlling an automatic hoe
in the cultivation of plants including sugar beets,
controlling an automatic hoe in the thinning of plants
including lettuce, controlling spray nozzles to spray
herbicide onto weeds around the base of trees in an orchard
--0 without spraying the trees, controlling spray nozzles to
spray insecticide onto trees in an orchard without spraying
spaces between adjacent trees, determining the locations of
rows of crop plants and selectively spraying weeds in the
middles between rows, determining the locations of rows of
crop plants and spraying materials onto the rows of crop
plants, guiding a vehicle through a field by determining the
locations of the rows of crops in the field, developing a
map of plants and other objects in a field, controlling
spray nozzles to spray herbicide onto weeds and not onto the
stalks of cotton plants, detecting foreign objects in a flow
of crop material including the detection of rocks in a flow
of grain inside a combine, and detecting a parasitic weed in
a field of row crop plants.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a sensor in accordance with
an embodiment of the present invention.
Figures 2A-2C are cross-sectional views of a light
detector of the sensor of Figure 1.
Figures 3A-3E are plan vi_ews of a light detector
illustrating an operation of the sensor of Figure 1.
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WO 96102817 PGT/US95/O8237 =
~i938.31
Figures 4A and 4B are views of an operation of the
sensor of Figure 1.
Figure 5 is circuit diagram showing one embodiment
of a circuit of the sensor of Figure 1 which generates
a signal indicative of a distance to an object.
Figure 6 is a diagram illustrating different
spectral reflection characteristics of a living plant,
a dead leaf, soil, and a parasitic weed over a
wavelength range of 400-1100 nm.
Figures 7A-7D are diagrams illustrating a light
pipe in accordance with some embodiments of the present
invention.
Figures 8A and 8B are diagrams illustrating the
spraying of herbicide around the base of a tree in
accordance with some embodiments of the present
invention.
Figures 9A and 9B are diagrams illustrating a
determination of the locations of rows of crop plants
in accordance with some embodiments of the present
invention.
Figure 9C is a diagram illustrating guidance of an
implement such as a cultivator through a field of row
crop plants using a hydraulic actuator in accordance
with some embodiments of the present invention.
Figure 10 is a diagram illustrating how weeds
growing in the rows of cotton plants are detected and
sprayed without spraying the cotton plants in
accordance with some embodiments of the present
invention.
DETAILED DESCRIPTION OF 'IHE PREFERRED EMBODIMENTS
Figure 1 illustrates a proximity determining
sensor 1 in accordance with an embodiment of the
present invention. Proximity determining sensor 1
comprises a source of light 2 which generates light 3,
a light beam forming lens 4 which forms light 3 into a
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= W 0 96102817 ~ f C~ ~}~ ~ 7 Pi T/US95/08237
light beam 5, a detector lens 6, and a light detector
7. Light beam 5 is aligned in direction A. Detector
lens 6 has an optic axis in direction B. If, for
example, light from light beam 5 reflects off an object
located at point P1, then reflected light from the
, light beam will be incident on light detector 7 at a
near image position 8. If, on the other hand, light
from light beam 5 reflects off an object located at a
distant point P5, then reflected light from the light
beam 5 will be incident on the light detector 7 at a
far image position 9. Reflections of light from light
beam 5 at several intermediate positions P2-P4 are also
illustrated in Figure 1. Sensor 1 may, for example, be
moved in direction C witli respect to the surface 10 of
the ground in an open field so that light beam 5 is
scanned over surface 10.
In one specific embodiment of Figure 1, the light
of light beam 5 is generated by a plurality of light
emitting diodes arranged in a row. Only one of the
light emitting diodes is illustrated in Figure 1
because the row of light emitting diodes extends in the
direction perpendicular to the plane illustrated.
Light beam forming lens 4 is a cylindrical lens which
has a longitudinal axis which extends in the direction
of the row of light emitting diodes. Light beam 5
therefore is a relatively thin sheet of light having a
first dimension which extends in the direction
perpendicular to the illustrated plane and having a
second dimension, the direction of travel of the light,
which extends in direction A.
In some embodiments, light detector 7 is a silicon
PIN photodiode Model No. SL3-2, manufactured by UDT
' Sensors, Inc., Hawthorne, California. other suitable
photodetectors may be used. In some embodiments, a
charge coupled device (CCD) may be used. In some
embodiments, lens 4 is a cylindrical lens approximately
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WO 96/0281.7 938 7 7 PCTNS95/08237 =
% 3 inches long and approximatelyl1 inch wide having a
focal distance of approximately 0.8 inches, available
from United States Precision Lens. In some
embodiments, detector lens 6 is a plano-convex lens
approximately 1.5 inches in diameter having a focal
distance of approximately 1.5 inches available from
United States Precision Lens. The angle between
directions A and B is about 7.1 degrees, the lateral
distance between light source 2 and light detector 7 is
about 2.8 inches, and the distance between light
detector lens 6 and light detector 7 is about 2.5
inches.
Figure 2A is a cross-sectional view of the light
detector 7 of Figure 1 showing near image position 8
and far image position 9 in greater detail. The image
plane of the detector surface of light detector 7 is
slanted with respect to the optic axis of light
detector lens 6 in order to maintain focus of the light
arriving from the various object positions P1-P5.
Figure 3A is a plan view of the detector surface
of the light detector 7 of Figure 1 looking up into
light detector 7 in the direction opposite to direction
B. Light detector 7 has an active area 11 and a chip
boundary 12.
Figures 4A and 4B are diagrams illustrating sensor
1 at two points in time when sensor 1 is moved in
direction C with respect to the surface 10 of a field.
As illustrated in Figure 4A, when at a first point in
time light from light beam 5 is reflected off a surface
of a relatively tall living plant 14A at a distance D1
from sensor 1, an image of the reflected light is
formed on light detector 7 at image position 13. As
illustrated in Figure 4B, when at a second point in
time sensor 1 has moved farther in the direction C with
respect to the surface 10 of the field, light from
light beam 5 is reflected off a surface of a relatively
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PGTNS95/08237
= WO 96102817 2193837
short living plant 14B at a distance D2 from sensor 1.
An image of the reflected light is formed on light
detector 7 at image position 15. Accordingly, the
position of the image of the reflected light on light
sensor 7 is indicative of the distance of the
reflecting object. The angle between the detector axis
and the light beam axis is set so that light reflected
from light beam 5 strikes the center of the light
detector 7 for an object located at a predetermined
distance from sensor 1. This allows for a large
variation in sensor-to-object distance variation.
Figure 2B is a cross-sectional view of one
embodiment of light detector 7. Light detector 7
actually comprises a plurality of smaller detectors 7A-
7E. If the image created by the light reflecting off
the relatively tall living plant 14A is formed at image
position 13 on detector 7C, then a corresponding signal
will be generated on an output terminal of detector 7C.
If, on the other hand, the image created by the light
reflected off the relatively short living plant 14B is
formed at image position 15 on detector 7B, then a
corresponding signal will be generated on an output
terminal of detector 7B. The distance from the sensor
1 to the object 14A, 14B is determined by identifying
from which particular detector of detectors 7A-7E the
signal emanates.
Figure 2C is a cross-section view of another
embodiment of light detector 7. Light detector 7
comprises a single detector, the near image position 8
being at one end of the detector active area, the far
image position 9 being at an opposite end of the
detector active area. Such a light detector has an
' additional anode terniinal, the relative magnitude of
the signals present on the two anode terminals being
indicative of the relative position of the image
between two ends of the active area of the detector.
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WO 96/02817 ,~ a' = ~~1 93837 PGTlUS95/08237 =
The distance from the sensor I to the object 14A, 14B
is therefore determined by comparing the relative
magnitudes of the two anode signals due to the
reflected image.
Figure 5 is a circuit diagram showing one
embodiment of a circuit 16 of sensor 1 which generates
a signal on terminal 19, the voltage of the signal
being indicative of a relative distance between a
reflecting object 14A, 14B and sensor 1. The specific
embodiment illustrated in Figure 5 comprises a first
trans-impedance amplifier 20, a second trans-impedance
amplifier 21, a difference amplifier 22, a summing
amplifier 23, and a divider 24. Anode terminals 25 and
26 of light detector 7 may, for example, correspond
with near image position 8 and far image position 9 of
a single detector light detector 7, respectively.
Light detector 7 has a the cathode 27 coupled to an LC
circuit 27A. Light detector 7 can be reverse biased or
can be operated in the photovoltaic mode as shown. The
LC circuit 27A is provided to discriminate sunlight as
explained below. The magnitude of an analog voltage
generated on the output terminal 19 of divider 24 is
proportional to a distance to a reflecting object.
This distance information in the form of an analog
voltage is converted to digital representation before
being processed in a microcontroller. In some
embodiments, output terminal 19 is coupled to an
analog-to-digital converter input pin of a
microcontroller (not shown).
Not only is light reflected from light beam 5
incident on light detector 7, but light from other
sources may also be incident on light detector 7.
When, for example, the sensor 1 is operated in broad
daylight in an open field, sunlight is reflected off
objects and back up into sensor 1. Moreover, because
the sunlight is not focussed into a beam, reflected
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CA 02193837 2006-09-01
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sunlight is incident on the entire detecting surface of
light detector 7. Sensor 1 distinguishes reflected sunlight
from reflected light from beam 5 using techniques disclosed
in U.S. Patent No. 5,296,702. In accordance with one
embodiment of the present invention, light 3 from light
source 2 is modulated with a modulation signal having a
frequency. The LC filter circuit 27A is tuned to the
modulation frequency and therefore passes energy at the
frequency of the modulation signal and attenuates energy at
other frequencies. Accordingly, the component of the signal
output by light detector 7 which is due to reflections of
light beam 5 is distinguished from components of the signal
output by light detector 7 which are due to the more slowly
varying ambient sunlight.
In some embodiments, a phase difference between
the signal output on output terminal 19 of the circuit of
Figure 5 and a modulation signal used to modulate the
light 3 emitted from light source 2 is used by a
microcontroller to determine whether an illuminated object
is a plant. The phase of the signa.l oscillating in
LC circuit 27A is determined by the phase of the radiation
received. If more radiation modulated with a first phase is
received, the signal oscillating iri LC circuit 27A will have
a phase relatively closer to the fi.rst phase whereas if more
radiation modulated with a second phase is received, the
signal oscillating in the LC circui.t 27A will have a phase
relatively closer to the second phase. Both distance
information and spectral characteristic information are
therefore provided by the same circuit of Figure 5. In
other embodiments, a separate circuit such as is set forth
in U.S. Patent No. 5,296,702 is provided to determine
whether
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W0 96I02817 193837 PCT![7S95/08237
the illuminated object is a plant so that distance
information is provided by the circuit of Figure 5 and
spectral characteristic information is provided by a
separate circuit.
In some embodiments, a plurality of units such as
sensor 1 are aligned in a row such that the row of
units senses objects disposed in a narrow illuminated
strip and such that each individual unit senses a
corresponding section of the strip. The light of light
beam 5, however, may diverge somewhat in the direction
perpendicular to the plane illustrated in Figure 1 so
that a band of an object illuminated by beam 5 at near
position P1 has a relatively short length whereas that
same band illuminated by beam 5 at far location P5 has
a relatively long length. In order to control the
field of view of the unit over a range of object
distances and prevent overlap of the fields of view of
adjacent units, an image mask 28 is disposed between
detector lens 6 and light detector 7.
Figure 3B illustrates five images 29A-29E
corresponding with light of beam 5 reflected from
positions P1-P5, respectively. Figure 3C illustrates
an image plane mask 28. An opening of image plane mask
28 has a first edge 28A which is non-parallel with
respect to a second edge 28B opposite the first edge.
Figure 3D illustrates the images 29A1-29E1 which are
incident upon the detector surface of light detector 7
due to the operation of image plane mask 28. Image
29E1 corresponds with the same illuminated object
distance on a distant object located at position P5 as
does object image 29A1 on a close object located at
position P1. Figure 3E illustrates the image incident
on the detecting surface of light detector 7 moving
back and forth across the detecting surface as a
distance between an object illuminated by light beam 5
is moved toward and away from sensor 1.
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In accordance with some embodiments of the present
invention, light of light beam 5 reflected back into
sensor 1 is also analyzed to determine a spectral
= characteristic of an object from which the light
reflected. Depending on the spectral reflectance
characteristic detected, a determination can be made as
to whether the object is a plant. Accordingly, a
sensor in accordance with some embodiments of the
present invention develops information indicative of
whether an object illuminated by light beam 5 is a
plant in addition to information indicative of a
distance between the sensor and the object.
Figure 6 is a diagram illustrating how certain
living plants, a dead or dying plant, soil, and a
parasitic weed reflect light having different
wavelengths over the wavelength range of 400-1100 nm.
Lines 30, 30A, 30B, 30C and 31 of the graph of Figure 6
indicate spectral characteristics of a living plant of
a first species A, a parasitic weed, a living plant of
a second species B, a dead or dying plant and soil,
respectively. By detecting a relative reflectance of
light off an object at two wavelengths (for example,
670nm and 750nm) it is possible to distinguish light
reflected from living plants from light reflected from
soil. By detecting a relative reflectance of light off
an object at two wavelengths (for example, 645 nm and
750 nm), it is possible to distinguish light reflected
from living chlorophyll bearing plants from light
reflected from certain parasitic weeds. By detecting a
relative reflectance of light off an object at two or
more wavelengths (for example, 430 nm, 575 nm and 750
nm), it is possible to distinguish light reflected from
various living chlorophyll bearing plants of certain
species from other chloropizyll bearing plants of other
species. it is possible to distinguish the difference
between rice and water grass in this fashion. A more
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R'096002817 j19 337 PCT/1JS95108237
detailed description of a technique for determining
whether an object is a living plant or is soil is set
forth in U.S. Patent Application Serial No. 07/920,942
(now U.S. Patent No. 5,296,702).
Therefore, in accordance with some embodiments of
the present invention, light 3 comprises light having a
first wavelength and light having a second wavelength.
The light having a first wavelength is modulated with a
first modulation signal whMreas the light of the second
wavelength is modulated with a second modulation
signal. In a preferred embodiment, the first
modulation signal has the same frequency as the second
modulation signal but is offset in phase with respect
to the second modulation signal. In accordance with
the technique disclosed in U.S. Patent Application
Serial No. 07/920,942 (now U.S. Patent No. 5,296,702),
the relative magnitude of the component of a signal
output by light detector 7 due to the light of the
first wavelength with respect to the component of the
signal output by light detector 7 due to the light of
the second wavelength is determined. A relative
magnitude corresponding with corresponding points on
line 30 is indicative of a reflection off a plant
whereas a relative magnitude corresponding with
corresponding points on line 31 is indicative of
reflection off soil. Although one technique for
developing information indicative of whether an object
is a plant is set forth here for illustrative purposes,
it is to be understood that other techniques which take
advantage of the different reflectance characteristics
of different objects may be employed in sensor 1.
Large object size to image size reductions (high
demagnification) when the object is close to the light
detector lens can be difficult to realize. Light rays
converging to the image focus are at a large included
angle and the depth of field is small. Light detector
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WO 96102817 2 1 ~ ~ '~ ~ PCT/US95108237
lens 6 may therefore be a somewhat expensive lens and
it may be difficult to adjust lens 6 mechanically in
order to achieve a proper focus of the reflected light
onto the detecting surface of the light detector 7. To
overcome these difficulties, the image is focussed at a
convenient lower demagnification with a lower power
light detector lens 6 and a non-imaging tapered light
pipe is used to effect a spatial compression of the
light of the image where distance determination or
proximity sensing is not performed by light detector 7.
Accordingly, system cost is reduced and mechanical
adjustment tolerances are relaxed.
Figure 7A shows a light pipe 32 disposed between
image mask 28 and light detector 7. Light detector 7
comprises a plurality of light detector chips. Due to
the inclusion of light pipe 32, light detector lens 6
need not focus on the relatively small detector
surface. Rather, a ray of light 33 passes into light
pipe 32 as illustrated in Figure 7B. Figure 7C is a
top-down view illustrating a ray of light 34 passing
through light detector lens 6, through the opening in
image mask 28, into light pipe 32, and onto light
detector 7. Figure 7D is a side view illustrating a
ray of light 35 passing through light detector lens 6,
through the opening in image mask 28, through light
pipe 32, and to light detector 7. Due to the tapered
shape of the light pipe 32, the light reflected off the
object reflects down the light pipe and onto the
smaller light detector surface.
Set forth below are several methods of use in
accordance with the present invention. The
applications set forth below do not constitute an
exhaustive treatment of all such methods but are merely
illustrative and are presented to teach the broad
applicability of the present invention.
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W0 96/Q21317 ,;j ,= ;' ~ 1 7 J rJ 37 FCT/US95/08237
/
METHOD #1
SPRAYING WEEDS GROWING IN THE GROUND AROUND TREES
Figures 8A and SB are diagrams illustrating an
orchard sprayer 33 for spraying weeds growing in the
ground around trees in accordance with an embodiment of
the present invention. Orchard sprayer 33 comprises
four sensors denoted T, A, B and C in Figures 8A and
8B. Each of the sensors comprises a plurality of light
emitting diodes which emits a narrow long light beam.
The narrow long light beams emitted from sensors A, B
and C are directed toward the ground as illustrated in
Figure 8B such that strips of the ground A, B and C are
scanned by light beams from sensors A, B and C,
respectively, as a means for moving 34 moves the
orchard sprayer with respect to the tree 35. The light
beam emitted from sensor T is, on the other hand,
directed in a substantially horizontal direction so as
not to illuminate weeds on the ground but so as to be
reflected off tree 35 as illustrated in Figure 8A.
Each of the three sensor A, B and C is coupled to
a corresponding row of electrically-controlled valves,
pumps, or injectors (not shown) so that a plant
detected by one of the sensors will be sprayed by
nozzles controlled by that sensor. In one embodiment,
each of the electronically-controlled valves (such as
part number AM2106 available from Angar Scientific) has
an associated spray nozzle and therefore forms an
electronically-controlled spray nozzle.
In order to spray weeds on the ground around tree
without spraying the tree itself, a distance to tree
35 is determined by sensor T as the means for moving 34
moves the orchard sprayer past the tree. A short time
after sensor T detects an object having a spectral
35 reflectance characteristic indicative of a living plant
(which in this case would be tree 35) at a distance
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WO 96102817 PCT/US95l08237
?; 938.31
between distance DT1 and DT2, the spray nozzles of
sensor A are disabled so that tree 35 will not be
sprayed. The spray nozzles coupled to sensors B and C,
however, remain enabled so that weeds growing in the
ground in strips B and C will be sprayed. Sensors B
and C only cause objects having a spectral
characteristic of a living plant to be sprayed and
therefore do not waste herbicide by spraying the bare
ground. After the means for moving 34 propels the
orchard sprayer farther so that sensor T detects tree
35 at a distance between distance DT2 and DT3, sensors
A and B are disabled leaving only sensor C to detect
and spray weeds in strip C. Again, sensor C only
causes objects having a spectral reflectance of a
living plant to be sprayed. When the orchard sprayer
has moved to the opposite side of the tree, the spray
nozzles for the corresponding strips are enabled in
reverse order as sensor T detects the distance to tree
35 getting larger, thereby spraying weeds in the ground
around tree 35 and not spraying herbicide onto the tree
itself.
In the illustration, sensors T, A, B and C are
mounted in a staggered configuration on means for
moving 34 in the direction of travel. The sensors A, B
and C would therefore be disabled and enabled an
appropriate amount of time after the tree is detected
by sensor T so that weeds in the corresponding strip
will be sprayed right up to the edge of the tree
without spraying the tree. The speed of the means for
moving 34 is therefore detected and used to determine
when to enable and disable the spray nozzles. In order
to prevent the spray froin interfering with the optics
of the plant detecting operation, the weeds are not
sprayed when they are detected but rather are sprayed
at a later time as explained in U.S. Patent Application
Serial No. 07/920,942 (now U.S. Patent No. 5,296,702).
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METHOD #2
SPRAYING TREES AND NOT SPACES BETWEEN TREES
In accordance with another embodiment, an orchard
sprayer detects a tree and then controls spray nozzles
to spray the tree with a chemical material (such as
pesticide and other foliar applied materials) so that
the chemical material is not wasted in the spaces
between trees. Because a distance sensor in accordance
with the present invention is able to determine whether
or not the reflected light has a spectral
characteristic of a living plant, such an orchard
sprayer distinguishes non-plant objects from living
trees, thereby overcoming the above described problem
of spraying barns and people associated with prior art
orchard sprayers. In some embodiments, material flow
is switched on and off depending on the total biomass
detected in the field of view and the distance to the
biomass. Fluid pressure, nozzle configuration, nozzle
direction and other parameters of the spraying
operation are also automatically adjusted to
accommodate the particular size, density and distance
to the biomass. This technique is also usable for
selectively dispensing herbicide on weeds along roads,
highways and railroad tracks.
METHOD #3
ROW CROP MIDDLE SELECTIVE WEED SPRAYER
Many crops grow in rows where the spacing between
rows is fixed by the planting or seeding implement.
Such row crops include corn, soybeans, tomatoes and
cotton. The space between adjacent rows is referred to
as the "middle" and often should be kept free of weeds
in order to optimize crop yield and to minimize
harvesting problems. Traditionally this middle has
been kept free of weeds by mechanical cultivation.
This technique has limitations. First, tilling or
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WO 96l02817 r..) ~ p Z b 7~ ~ PC TNS95l08237
breaking up the soil requires large equipment and
therefore large amounts of energy. Second, so-called
"cultivator burn" results from getting too close to the
row with the cultivator tines and damaging plant roots.
Third, tilling opens the soil to the air thereby
allowing moisture to escape and making the soil subject
to erosion from wind and rain.
Spraying weeds in the middles with herbicide may
therefore be considered a more desirable method of
eliminating weeds from the middles. Two principle
difficulties with spraying weeds are cost of the
herbicide material and the potential of contaminating
the environment with excessive chemicals. Both of
these problems are addressed by aspects of present
Invention.
Weeds in middles are generally found in patches
ranging from a few inches across to a few feet across.
It is generally not practical for a spray vehicle
operator to turn the sprayer off and on, each time a
patch of weeds is encountered. Therefore a preferred
technique is to rely heavily on preemergence herbicide
to discourage weed seeds from gerniinating and then
later spraying a continuous blanket of post emergence
herbicide in the middles to eliminate any weeds which
germinated despite the preemergence herbicide.
Selective spraying using the optical detection
technology described previously eliminates the need for
preemergence herbicide and minimizes the application of
postemergence herbicide because only weeds are sprayed
and significant amounts of bare soil is not sprayed.
Considerable cost savings can result.
Figures 9A and 9B show a means for moving 34 (in
this case a tractor) outfitted with a plurality of
sensors 36 and a plurality of solenoid-operated spray
nozzles (not shown). The sensors are mounted on a boom
such that a strip of the field perpendicular to
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direction of tractor movement D is illuminated with
modulated light. Distance information and information
on whether an illuminated object has spectral
reflectance indicative of crop plant, weed plant or
soil is sent to a central digital processor (not
shown). By storing past information on which sensors
detect the most objects having special characteristics
of plants and which sensors detect the most objects
having heights consistent with the expected crop
height, the central digital processor determines which
illuminated objects having special plant
characteristics are crop plants in rows 37 and which
are randomly scattered weeds 38. Accordingly, the
central digital processor disables the spray nozzles
located over the rows 37 of crops. As a result, only
the weeds 38 in the middles are sprayed. The row crops
38 are not sprayed and herbicide is not wasted on the
bare ground in the middles.
METHOD #4
ROW CROP ROW SELECTIVE CROP SPRAYER
In accordance with another embodiment, rows of
crops are located as described above. Rather than
spraying the middles with herbicide, however, the crop
plant in the rows are sprayed with foliar nutrients,
pesticide, selective herbicide or water.
METHOD #5
VEHICLE OR IMPLEMENT GUIDANCE
In many farming operations, a vehicle and/or
implement is guided through rows of crops in a field.
In cultivating row crops, for example, the cultivator
implement is guided as fast as possible through the
rows of crops so that the cultivator tines come as
close as possible to the crops plants without damaging
the crop itself. Manually guiding the vehicle andfor
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PCT/US95/08237
W0 96102817 21 93837
implement with respect to the rows is a demanding and
tedious task. If, for example, the cultivator strays
too close to a row, a section of the row of crop plants
may be uprooted. Various automatic implement and
vehicle guidance systems therefore have been developed
to guide vehicles and implements with respect to rows
of crops. None of these automatic vehicle guidance
systems has, however, enjoyed broad market acceptance.
A furrow is formed between adjacent rows at the
time the row crop is planted. "Mole balls" are
physical weights which are dragged in such a furrow.
As the vehicle moves through the field, the weight of
mole ball keeps the mole ball in the furrow between
rows. If the vehicle or implement strays toward either
row, switches or valves are actuated which operate a
hydraulic cylinder to adjust the direction of travel of
the vehicle or implement.
Another vehicle guidance technique involves the
use of wires or similar mechanical devices which make
actual physical contact with the row crop plants. The
mechanical touching devices are connected to switches
which in turn control a hydraulic or other means of
redirecting the vehicle or implement.
Still other vehicle guidance techniques use
ultrasonic sonar andJor infrared detectors. An
infrared method disclosed in U.S. Patent Number
5,279,068 directs infrared radiation toward plants in
two adjacent crop rows. The two magnitudes of the
reflected infrared radiation are compared and the
vehicle or implement is steered to keep the magnitudes
of the two signals balanced thereby keeping the vehicle
or implement centered between the two rows. This
technique is believed to have problems due to weeds in
the middle reflecting and giving incorrect data and due
to voids in the row of crop plants not reflecting and
not providing sufficient data. Accordingly, the above-
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WO 95/02817 PC'PJUS93/08237
, ~.
93R37 ~
described techniques exhibit problems when faced with
situations involving fields without well contoured
furrows, crop plants which are damaged by physical
contact with the guidance device, and voids in crop
rows where plants have not survived.
These problems are overcome in accordance with
embodiments of the present invention. As set forth
above in connection with Figures 9A and 9B, sensors 36
are mounted on the vehicle or implement. The sensors
may be disposed to illuminate and therefore follow only
one row. Alternatively, the sensors may illuminate and
follow multiple rows as is illustrated in Figures 9A
and 9B. Each sensor may output three types of
information: 1) information indicative of whether there
is an object at a suitable range from the sensor in the
field of view, 2) information indicating whether an
object in range in the field of view has spectral
reflectance properties indicative of a plant crop, a
weed, or another object, 3) and information indicative
of a distance to the object. In some embodiments, the
magnitude of total reflected radiation detected is the
information indicating that an object is at a suitable
range from the sensor in the field of view. A digital
processor coupled to the sensor examines the output of
each sensor periodically and stores the information in
memory. The digital processor, with the aid of
software composed for this purpose, compares the
current data being gathered from the sensors to the
data stored in memory. From the information available,
the digital processor makes very accurate predictions
on row location based on ebject sizes, object heights,
ground topology and/or plant locations and spectral
reflectance properties. Because the crop plants were
planted at the same time in an accurate row pattern,
they are probably of a somewhat consistent size. The
processor is therefore able to determine accurately
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WO 96102817 ~ 1 9 3837 PCT/US95/08237
1-
which plants are crop and which plants are weeds.
Knowing which plants are the crop allows the processor
to plot a line which represents the centerline of the
crop row 37. In some embodiments, this information is
put into a format which is accepted by currently
available vehicle guidance systems.
In some embodiments, an implement is guided (for
example, a cultivator) with respect to rows in a field.
Figure 9C is a diagram illustrating a plurality of
sensors 36 coupled to a digital processor 90. Digital
processor 90 comprises a multi-input analog-to-digital
converter 90A, microcontroller 90B and memory 90C.
Digital processor 90 determines the locations of the
rows of crop plants 91 and moves the implement 92 to
the left or the right via valve drivers 93, valves 94
and hydraulic actuator 95. If, for example, the
implement 92 is a cultivator, the digital processor 90
controls the location of the tines of the cultivator to
uproot weeds 96 but to leave crop plants 91. Vehicle
97 may or may not be guided by the digital processor 90
through the rows of crops in the field. Voids in crop
rows where plants have not survived does not cause the
guidance system to fail.
In other embodiments, a vehicle guidance system
does not use spectral information but rather uses only
distance to object information. For example, where
dead plants are to be harvested or where a vehicle or
implement is to be guided through a recently planted
field in which the seeds have not yet germinated, the
distance information may be used to map soil contours
and to locate furrows and rows accordingly.
MP:THOD #6
MAPPING OBJECTS IN A FIELD
Some parts of a field may have different types of
soil, may receive different amounts of runoff, may
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WQ.96l02817 2 1 938 5 1 PCT/U545J08237
receive different amounts of direct sunlight, may have
different types of pests, and may be subject to other
environmental factors which affect plant growth in
different ways. If information bearing on these
different environmental factors could be easily
gathered, such information could be used in determining
how and when to till, to fertilize, and to harvest. It
could be determined, for example, that certain parts of
a field should be planted with one type of crop whereas
another parts of the field should be planted with
another type of crop.
in accordance with one embodiment of the present
invention, information to make a map of a field is
gathered automatically when the field is traversed for
another purpose such as cultivating. information
indicative of whether a strip of a field illuminated
with modulated light contains soil, living crop plants,
weeds or other objects, and the size of these plants or
other objects is supplied by a sensor of the present
invention to a data storage device. The same sensor
unit is able to determine the amount of organic
material in the soil. As a tractor, picker, combine or
other means for moving sweeps the sensor and data
storage device across the field, the data storage
device records the soil/plant information and distance
information on a storage m4dium. A hard disk drive may
be used. In some embodiments, the data storage device
also receives position information from a global
positioning system (GPS) device so that the detected
characteristics of the field are mapped to the
corresponding geographical locations in the field. In
this way, characteristics of the field can be gathered,
downloaded from the data storage device, and later
analyzed. In fact, the analysis can be done in real
time and application rates adjusted simultaneously.
Using this technique, multiple field maps gathered
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t
during multiple growing seasons and for different types
of crops can be compared and analyzed.
METHOD #7
COTTON IN-ROW WEED SPRAYER
Many row crops are grown in rows with plants in
each row spaced only a few inches apart. Rows may be
spaced 30 to 40 inches apart. Typically plant spacing
within each row is uneven so that the canopy of
adjacent plants often grow into each other or
conversely there could be gaps where no plants exist.
In such a situation, it is possible to identify the
centerline of the planted row (as discussed above) but
it may not be possible to rely upon the plant spacing
within the row for purposes of eliminating weeds
growing between crop plants in the row. It is
therefore desirable to discriminate between weeds and
crop plants using more than plant/soil location
information.
Cotton is a crop where it is desirable to
discriminate between crop plants in rows and weeds
between the crop plants in order to selectively
eliminate weeds without damaging the crop plants. When
the cotton plant is less than a few weeks old, its
stalk is soft green tissue which is somewhat
translucent to near infrared light. The stalk reflects
strongly in the infrared portion of the spectrum and it
appears to have much the same spectral reflectance as a
weed might. It is therefore difficult to discriminate
the cotton crop from the weed plants. At this stage of
the crop development, one weeding method is to spray
the rows with a continuous band of selective chemical
herbicide which can be tolerated by the cotton crop
(e.g., MSMA). Another method measures the differences
in spectral reflectance, at certain wavelengths, of
cotton plants versus that of the weed plants. Certain
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9VO 96102817 9 a n 5 Z PGT/RS95/0823 7
J?3
weed types can be discriminated from cotton plants on
the basis of a different spectral reflectance and
treated accordingly.
At a later stage, the cotton stalks become opaque
but generally still have the spectral characteristics
of weeds. At this point it is possible to discriminate
cotton stalks in the rows from weeds in the rows.
Figure 10 shows a first sensor 39 located on one side
of a row of cotton stalks 41 and second sensor 40
located on the other side of the row. In this
embodiment, sensor 40 is oriented to receive only light
modulated by sensor 39 and sensor 39 is oriented to
receive only light modulated by sensor 40. Light
reflecting off an object surface in the crop row
centerline has an angle of reflection of in excess of
45 degrees. In the specific embodiment illustrated,
the angle of reflection exceeds 90 degrees.
Because the vertical cotton stalks 41 typically do
not provide a reflecting surface that reflects light
from one side of the row to the other, and because the
weeds 41 having a different reflective surface profile
do provide such a reflecting surface, the sensor does
not detect modulated light reflected from cotton stalks
but does detect modulated light reflected from weeds 42
in the cotton rows. The weeds 42 can therefore be
selectively eliminated without damaging the cotton
stalks 41.
At a later stage, the cotton stalks become woody
and cease to be similar in spectral reflectance to
weeds. The cotton crops can therefore be discriminated
from the weeds using the normal spectral reflectance
technique described earlier. Weeds in cotton can be
eliminated using electronically-controlled plant-
eliminating devices including automatic hoes and
electronically-controlled herbicide applying spray
nozzles.
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METHOD #8
DETECTING DISSIMILAR OBJECTS IN A FLOW OF GRAIN
Harvesting equipment is particularly prone to
being damaged by picking up rocks and other hard
objects. A sensor in accordance with the present
invention is used to detect the presence of rocks or
metal fragments in the f.low of crop material in
harvesting equipment and to disengage power before
damage can result. The field-of-view of a sensor
capable of determining a spectral reflectance of an
object is aligned across the flow of the crop material
in the harvesting equipment. The background may be a
pipe, wall or panel having a particular spectral
reflectance, the flow of crop material flowing between
the sensor and the background. Crop material flowing
through the field of view of the sensor results in a
certain spectral signature being detected by the
sensor. In the event that the crop has a spectral
characteristic of a living plant 30 such as is shown in
Figure 6, introduction of a rock into the flow of crop
material will result in a substantially different
spectral characteristic being detected. The difference
in spectral characteristics is used to detect the rock
and to disengage power from the harvesting equipment.
METHOD #9
DETECTING A PARASITIC WEED IN A FIELD OF CROP PLANTS
in accordance with the present invention, a
parasitic weed is discriminated from a crop plant.
Line 30A in Figure 6 shaws the spectral reflectance of
a parasitic weed known as Dodder versus wavelength.
Dodder germinates from a seed which may lay dormant in
the ground for up to ten years. When about 2 to 3
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inches tall, the Dodder plant finds a host (the host
could be a safflower plant, a tomato plant, or an
alfalfa plant). The young Dodder plant attaches itself
to the host, qrows up into the host plant, severs its
own roots to the soil, and lives parasitically from its
host. When mature, the Dodder plant looks much like a
ball of orange colored spaghetti. Being orange, it has
a different spectral reflectance characteristic in the
visible spectrum which differentiates it from a
chlorophyll bearing host plant. Because Dodder has
very little chlorophyll, the spectral reflectance curve
for Dodder does not have as large of a chlorophyll
absorption dip at 670 nanometers as do host plants
having larger amount of chlorophyll.
In accordance with one embodiment of the present
invention, spectral reflectance at two wavelengths is
measured. As illustrated in Figure 6, an ordinary crop
plant typically has a larger difference between the
reflectance at wavelengths 670 nanometers and the
reflectance at 770 nanometers than the parasitic Dodder
weed. The magnitude of the difference in spectral
reflectance at these two characteristic wavelengths is
used to discriminate light reflecting from the
parasitic weed from light reflecting from the crop
plant. After the parasitic weed is identified in the
field and distinguished from the crop plants, the '
parasitic weed is automatically eliminated by selective
spraying or selective cultivation. Over a period of
years, all parasitic weeds and seeds of parasitic weeds
are eliminated from the fi4ld.
Although the present invention has been described
by way of the presently described specific embodiments,
the invention is not limited thereto. Adaptations,
modifications and various combinations of different
aspects of the specific embodiments may be practiced
without departing from the spirit and scope of the
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invention. The term "light" is not limited to visible
light, but rather includes infrared radiation,
ultraviolet radiation, and electromagnetic radiation of
other suitable frequencies. The above description is
presented merely for illustrative instructional
purposes and is not intended to limit the scope of the
invention as set forth in the appended claims.
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Representative Drawing