APPARATUS FOR SPRAYING INSECTICIDES

Abstract

An apparatus for dispensing an insecticide across an area of land; the apparatus comprising a vehicle configured to travel along a travelling path across the area of land, the vehicle defining a direction of travel, the vehicle comprising an insecticide dispensing device configured to dispense an insecticide along said traveling path when the vehicle travels along the travelling path; a dispensing control system configured to control an amount of insecticide to be dispensed when the vehicle travels along the travelling path; an insect sensor configured to detect insects in a detection volume; wherein the detection volume is located in front of the vehicle relative to the direction of travel;

wherein the dispensing control system is configured to receive sensor data from the insect sensor, the sensor data being indicative of detected insects in the detection volume, and to control the amount of dispensed insecticide responsive to the received sensor data.

Claims

1. An apparatus for dispensing an insecticide across an area of land, the area of land defining a ground surface, the apparatus comprising: a vehicle configured to travel along a travelling path across the ground surface, the vehicle defining a direction of travel, the vehicle comprising an insecticide dispensing device configured to dispense an insecticide along said traveling path when the vehicle travels along the travelling path; a dispensing control system configured to control an amount of insecticide to be dispensed when the vehicle travels along the travelling path; an insect sensor configured to detect airborne insects in a detection volume while the detection volume moves relative to the ground surface; wherein the detection volume is located in front of the vehicle relative to the direction of travel and elevated above the ground surface by a minimum vertical offset; wherein the dispensing control system is configured to receive sensor data from the insect sensor, the sensor data being indicative of detected insects in the detection volume, and to control the amount of dispensed insecticide responsive to the received sensor data.

2. An apparatus according to claim 1; wherein the detection volume has a size of at least 0.2 m.sup.3, or at least 0.5 m.sup.3, or at least 1 m.sup.3, or at least 2 m.sup.3, or at least 3 m.sup.3.

3. (canceled)

4. An apparatus according to claim 1; wherein the detection volume has an aspect ratio, defined as a ratio of a largest edge to a smallest edge of a minimum bounding box of the detection volume, of no more than 10:1, or no more than 5:1, or no more than 3:1, or no more than 2:1.

5-10. (canceled)

11. An apparatus according to claim 1; wherein the insect sensor comprises an illumination module configured to illuminate the detection volume and one or more detectors configured to detect light from the detection volume or wherein the illumination module is configured to simultaneously illuminate the entire detection volume.

12. An apparatus according to claim 11; wherein the illumination module includes a light source configured to emit incoherent light, wherein the light source includes one or more light emitting diodes and/or one or more halogen lamps.

13. An apparatus according to claim 11; wherein the illumination module is configured to emit a diverging beam of light having a divergence angle in at least one direction of between 2° and 45°, or between 10° and 30°.

14-16. (canceled)

17. An apparatus according to claim 11, wherein the illumination module comprises a first light source configured to selectively emit light at a first wavelength range, and wherein the illumination module further comprises a second light source configured to selectively emit light at a second wavelength range, spaced-apart from the first wavelength range.

18. An apparatus according to claim 11; wherein the one or more detectors comprise a camera and/or one or more photo diodes and are configured to selectively detect light within a first wavelength band and within a second wavelength band, non-overlapping with the first wavelength band.

19. (canceled)

20. An apparatus according to claim 18; wherein the one or more detectors comprise at least one photodiode array, each photodiode of the array being configured to receive light from a respective sub-volume of the detection volume.

21. (canceled)

22. An apparatus according to claim 11; wherein the insect sensor comprises a processor configured to identify, from detector signals from the one or more detectors, one or more types of insects and to determine respective amounts of the one or more types of insects detected in the detection volume, in particular based on one or more indicators chosen from: a detected trajectory of movement of an insect inside the detection volume; a detected speed of movement of an insect inside the detection volume; one or more detected wing beat frequencies; a melanisation ratio; an insect glossiness.

23. An insect sensor for detecting airborne insects moving above a ground surface, the insect sensor comprising: an illumination module configured to illuminate a detection volume, the detection volume being elevated from the ground surface by a minimum vertical offset, and one or more detectors configured to detected light from the detection volume; wherein the illumination module is configured to emit a diverging beam of light having a divergence angle in at least one direction of between 2° and 45°, or between 10° and 30°.

24. An insect sensor according to claim 23; wherein the illumination module includes a light source configured to emit incoherent light, the light source including one or more light emitting diodes and/or one or more halogen lamps.

25-26. (canceled)

27. An insect sensor according to claim 23, wherein the illumination module is configured to simultaneously illuminate the entire detection volume.

28. An insect sensor according to claim 23, wherein the illumination module comprises a first light source configured to selectively emit light at a first wavelength range, and wherein the illumination module further comprises a second light source configured to selectively emit light at a second wavelength range, spaced-apart from the first wavelength range.

29. (canceled)

30. An insect sensor according to claim 23; wherein the one or more detectors are configured to selectively detect light within a first wavelength band and within a second wavelength band, non-overlapping with the first wavelength band.

31. An insect sensor according to claim 13; wherein the one or more detectors comprise at least one photodiode array, each photodiode of the array being configured to receive light from a respective sub-volume of the detection volume.

32-33. (canceled)

34. An insect sensor according to claim 23; wherein the vertical offset is chosen to be between 10 cm and 5 m, or between 20 cm and 3 m, or between 20 cm and 2 m, or between 50 cm and 2 m.

35. A method of controlling the spraying of insecticides, the method comprising the steps of: detecting airborne insects moving about a detection volume, the detection volume being located in front of a moving vehicle and the detection volume being elevated above a ground surface by a minimum vertical offset; controlling the dispensing of insecticides from said moving vehicle responsive to the detection of airborne insects.

36. (canceled)

37. A method according to claim 35; wherein the detecting comprises obtaining sensor data indicative of an estimated insect population within a sampling volume above the ground surface; the sampling volume being traversed by the detection volume during relative movement of the detection volume relative to the ground surface during the sampling period t.

38. (canceled)

39. A method according to claim 35, wherein the detection volume extends from a top of a vegetation canopy upwards.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Preferred embodiments will be described in more detail in connection with the appended drawings, where

[0076] FIG. 1 shows a schematic view of an apparatus for spraying insecticides.

[0077] FIG. 2 schematically illustrates operation of an apparatus for spraying insecticides.

[0078] FIG. 3 schematically illustrates an embodiment of an insect sensor.

[0079] FIG. 4 schematically illustrates an example of a detector module of an insect sensor.

[0080] FIG. 5 schematically illustrates another example of a detector module of an insect sensor.

[0081] FIG. 6 schematically illustrates another embodiment of an insect sensor.

[0082] FIG. 7 schematically illustrates an example of a sensor signal form a detector module of an embodiment of an insect sensor as described herein.

[0083] FIGS. 8 and 9 illustrate examples of detection volumes.

DETAILED DESCRIPTION

[0084] FIG. 1 shows a schematic top view of an apparatus for spraying insecticides. The apparatus comprises a farming vehicle 100, such as a tractor or other ground vehicle. It will be appreciated that, alternatively, an aerial vehicle may be employed.

[0085] The vehicle is configured to travel along a travelling path across a field or other ground surface of ab area of land on which insect control is to be performed. The vehicle defines a direction of travel as illustrated by arrow 101. The direction of travel will also be referred to as forward direction relative to the vehicle.

[0086] The vehicle comprises an insecticide dispensing device 110 comprising one or more outlet ports for dispensing insecticide. For example, the dispensing device 110 may comprise an arm extending along a lateral direction, i.e. across the direction of travel 101. A plurality of sprayer nozzles are positioned on the arm, e.g. distributed across the length of the arm. The dispensing device may be arranged at or towards the rear of the vehicle, though other positions are possible as well. The vehicle further comprises a dispensing control unit 140, e.g. a suitable controller circuit such as a suitably programmed microprocessor or the like. The dispensing control unit is operatively coupled to the dispensing device and operable to control the amount of insecticide dispensed by the dispensing device 110. To this end, the dispensing control device may be operable to control a valve or similar flow control device for controlling the insecticide flow from an insecticide reservoir (not explicitly shown) to the output ports of the dispensing device. In some embodiments, the dispensing control unit 140 may control multiple valves for controlling insecticide flow to the respective individual output ports. In some embodiments, the vehicle may comprise multiple insecticide reservoirs, e.g. for storing different types of insecticides. In such an embodiment, the dispensing control unit may be operable to selectively control insecticide flow from the respective reservoirs to the dispensing device, e.g. so as to control which type of insecticide or combination of insecticides is to be dispensed. The dispensing control unit may control the dispensing of insecticides in real-time i.e. change the amount and/or type of insecticide to be dispensed while the vehicle travels along a travelling path. Accordingly, the dispensing control unit may cause different amounts and/or types of insecticide to be dispensed at different locations along the travelling path.

[0087] The apparatus further comprises an insect sensor 120 for detecting insects in front of the vehicle 100 while the vehicle is travelling in the direction of travel 101. To this end, the insect sensor may be mounted at or proximal to the front end of the vehicle.

[0088] Alternatively, the insect sensor may be mounted at a different location of the vehicle or even be provided on a separate vehicle, e.g. a drone or unmanned ground vehicle travelling in front of, next to or above the vehicle 100.

[0089] The insect sensor 120 of the embodiment of FIG. 1 comprises an arm or frame 133 that is mounted to the front end of the vehicle. The insect sensor further comprises an illumination module 131 and a detector module 130, each mounted to the arm or frame 133. It will be appreciated, that other embodiments may include more than one illumination module and/or more than one detector module. It will further be appreciated that the illumination module and the detector module may be provided as separate devices, i.e. each module may have its own housing. In other embodiments the illumination module and the detector module may be accommodated in a single housing or otherwise form a single unit. In other embodiments, the insect sensor may be mounted on the vehicle in a different manner, e.g. not including an arm or frame.

[0090] The illumination module 131 comprises a light source, such as one or more halogen lamps, one or more LEDs or the like, configured to illuminate an illuminated volume in front of the vehicle. The illumination module may be communicatively coupled to the dispensing control unit 140 so as to allow the dispensing control unit to control operation of the illumination module. The detector module 130 comprises one or more detectors and one or more optical elements configured to capture backscattered light from at least a portion of the illuminated volume and to guide the captured light onto the one or more detectors. The illuminated volume from which light is captured by the detector module for detecting insects is referred to as detection volume 150. The detector module 130 is communicatively coupled to the dispensing control unit 140 and forwards detector signals, optionally processed detector signals, to the dispensing control unit. The dispensing control unit processes the received detector signals so as to detect insects in the detection volume. Based on the detected insects, the dispensing control unit 140 controls operation of the dispensing device so as to cause the dispensing device to dispense insecticide corresponding to the detected insects in the detection volume. In some embodiments, the dispensing control unit may control the dispensing device to dispense the insecticide when the dispensing device reaches the location of the detection volume on which the dispensing decision was made. Alternatively, the insect sensor comprises a processor configured to perform the insect detection and to forward information about the detected insect population to the dispensing control system.

[0091] Hence, as the vehicle travels along a travelling path, the detector module captures light from a detection volume in front of the vehicle, i.e. the detection volume also travels along the travelling path, ahead of the vehicle. The dispensing control unit may thus continuously (or at least intermittently) control the dispensing device to adjust the dispensing of the insecticide to the currently (or most recently) detected insects in front of the vehicle. It will be appreciated that the adjustment may be delayed so as to account for the relative delay of the movement of the dispensing device relative to the detection volume along the travelling path, and taking the latency of the analysis of the detector signals into account. In other embodiments, the control of the dispensing device may occur after the vehicle has already passed the detection volume on which the control is based. However, the inventors have realised that such a delay is acceptable and still results in a sufficiently fine-grained adaptation of the dispensing of insecticides.

[0092] FIG. 2 schematically illustrates operation of an apparatus for spraying insecticides. In particular, FIG. 2 illustrates considerations for selecting the size and shape of the detection volume.

[0093] FIG. 2 shows an insect sensor 120 and the dispensing device 110 of the vehicle of FIG. 1. The insect sensor and the dispensing device travel along the direction of travel 101 such that the insect sensor travels ahead of the dispensing device. The insect sensor is forward-facing and monitors a detection volume 150 that also travels along the direction of travel 101, ahead of the insect detector.

[0094] In FIG. 2, the detection volume is illustrated as a box-shaped volume having a height H, a width W and depth D. It will be appreciated, however, that the detection volume may have a different shape, other than box-shaped. Preferred embodiments of a detection volume will be described below with reference to FIGS. 8 and 9. Generally, the shape and size of the detection volume and the position of the detection volume relative to the vehicle are determined by the illumination module and by the detector module of the insect sensor. Generally, the detection volume may be defined as the volume from which the detection module obtains sensor signals useful for detecting insects. The detection volume is typically defined by an overlap of the volume illuminated by the illumination module and by the field of view and depth of field of the detector module.

[0095] The insect detection may be performed based on signals recorded over a sampling period t. Generally, when the insect sensor is movable relative to a ground surface, e.g. because the insect sensor is mounted on a moving vehicle, the detection volume moves relative to the ground surface. Accordingly, when the sensor data is indicative of detected insects in the detection volume during a period of time t, the sensor data is indicative of detected insects within a space traversed by the moving detection volume during time t. Here and in the following, the volume traversed by the moving detection volume during a sampling period t will also be referred to as sampling volume. Accordingly, sensor data indicative of detected insects in the detection volume may provide an estimate of a local insect population within the sampling volume above the ground surface, the sampling volume being traversed by the detection volume during relative movement of the detection volume relative to the ground surface during the sampling period t. For example, when the vehicle travels at constant speed v across a ground surface, the total sampling volume sampled during the sampling period t is thus V.sub.sample=V.sub.0+A*v*t, where V.sub.0 is the detection volume (in the above example V.sub.0=H*W*D) and A is the cross sectional area of the sampling volume in the direction of travel (in the above example A=W*H).

[0096] The inventors have realised that, in order to make a decision as to whether to spray insecticide or not, it is preferred to locally sample at least a sampling volume of 1 m.sup.3 in order to get a result representative of the insect population.

[0097] Assuming a travelling speed of the vehicle of 20 km/h and a distance between the insect sensor and the detection volume of 6 m, a box-shaped detection volume having a height of H=1 m, a width of W=1 m and a depth of D=0.6 m, the detection volume is V.sub.0=0.6 m.sup.3 and sampling of a sampling volume of V=1 m.sup.3 requires t=0.1 s. However, larger detection volumes may be preferable so as to provide more accurate detection results. Accordingly, for typical vehicle speeds of farming vehicles, detection volumes of at least 0.2 m.sup.3, such as at least 0.5 m.sup.3, such as at least 1 m.sup.3, such as at least 2 m.sup.3 have been found suitable.

[0098] Another consideration relates to the shape of the detection volume. In order to allow for a reliable detection and identification of an insect (e.g. to be able to determine an insect's wing beat frequency), the insect should preferably remain in the detection volume for at least 0.1 s. In order to allow insects to remain in the detection volume as long as possible, regardless of the direction of travel of the insect (and regardless of the movement of the detection volume along the direction of travel), the linear dimensions of the detection volume should be similar along all directions. However, in practice, aspect ratios between the longest extent of the detection volume and the shortest extent of the detection volume of no more than 10:1, preferably no more than 5:1, preferably no more than 3:1, more preferably no more than 2:1 have been found suitable.

[0099] Yet another consideration relates to the position of the detection volume 150 relative to the vehicle and relative to the ground. In some embodiments, the detection volume may be selected sufficiently far ahead of the vehicle so as to allow the dispensing control unit (or other processor) to perform the necessary data processing so as to obtain a detection result within the time it takes for the dispensing device to travel the distance between the dispensing device and the detection volume. On the other hand, the detection volume should be sufficiently close to the vehicle so as to ensure that the detected insect population accurately reflects the insect population at a location when the dispensing device reaches said location. If the detection volume is too far removed from the dispensing device, the insect population may have changed considerably by the time the dispensing device has travelled the distance between the dispensing device and the detection volume.

[0100] The preferred vertical offset of the detection volume from the ground and/or the height of the detection volume may depend on the type of crops/vegetation and on the type of insects to be detected. For airborne insects and optical insect sensors, the detection volume is preferably located above, most preferably immediately above a reference plane. The reference plane may e.g. be defined the vegetation canopy of the area or land or by another horizontal plane positioned at a vertical offset above the ground surface.

[0101] In the following, embodiments of an insect sensor will be described which may be mounted on an agricultural vehicle, e.g. as described in connection with FIG. 1, or which may otherwise be deployed, e.g. stationary or mobile.

[0102] FIG. 3 schematically illustrates an embodiment of an insect sensor. The insect sensor comprises a forward facing detection module 130 and an illumination module 131. In this example, the illumination module is formed as two elongated arrays of LEDs. Each array extends laterally from either side of the detector module. The arrays define an illumination volume 151 illuminated by both arrays. The detector module comprises an imaging system operable to image an object plane 152 inside the illuminated volume onto at least one image plane of the detector module. The field of view of the imaging system and the depth of field 153 of the imaging system are configured such that the imaging system images at least a portion of the illuminated volume onto an image plane of the detector module. The portion of the illuminated volume imaged by the imaging system such that it can be detected by one or more detectors of the detector module and used for insect detection defines the detection volume 150.

[0103] For example, the detector module may include an image sensor, e.g. a CCD or CMOS sensor, so as to allow imaging of insects within the Illuminated volume. It has been found that imaging of insects in a detection volume is suitable for identifying insects based on trajectories of insects moving within the detection volume, i.e. within the depth of field of the imaging system. This allows detection and identification even of insects that are difficult or impossible to detect and identify based on wing beat frequencies. An example of such an insect is the jumping Cabbage Stem Flee Beatle.

[0104] For example, an imaging system based on a camera lens having f=24 mm, f/2.8 and a 3/4″ image sensor configured to focus on an object plane at 2 m distance from the lens, the field of view is approximately 1.7 m×1.7 m and the depth of field is approximately 1.3 m, thus resulting in a detection volume of approx. 3.7 m.sup.3.

[0105] It will be appreciated that other imaging systems may be used. Also, additional and alternative detectors may be used.

[0106] It will further be appreciated that the illumination module may be arranged in a different manner relative to the detector module and/or include a different type and/or number of light sources.

[0107] Generally, in order to maximize the amount of backscattered light from insects inside the detection volume, it may be preferable to position the illumination module adjacent or otherwise close to the detector module, such that the illumination direction and the viewing direction only define a relatively small angle between them, e.g. less than 30°, such as less than 20°. In some embodiments, the illumination module is configured to emit a beam of light along an illumination direction, and the detector module defines a viewing direction, e.g. as an optical axis of the detector module, wherein the illumination direction and the viewing direction define an angle between each other, the angle being between 1° and 30°, such as between 5° and 20°.

[0108] FIG. 4 schematically illustrates an example of a detector module of an insect sensor. The detector module comprises an image sensor 411 and two photodiode arrays 405 and 409, respectively. The image sensor 411 records an image of a detection volume 150 as described above. To this end the detector module comprises lenses 401, 403 and 410 for imaging on object plane in the detection volume at a suitable depth of field onto the image sensor. In particular, lens 401 images the object plane onto a virtual image plane 420. Lens 403 collimates the light from the virtual image plane and lens 410 focusses the collimated light onto the image sensor. A part of the collimated light is directed by beam splitter 404 towards another lens which focusses the light onto photodiode array 405.

[0109] Similarly, another portion of the collimated light is directed by beam splitter 407 onto lens 408 which focusses the light onto photodiode array 409. The beam splitter 404 is configured to selectively direct light at a first wavelength, e.g. 970 nm, onto photodiode array 405, while beam splitter 407 is configured to selectively direct light at a second, different, wavelength, e.g. 808 nm, onto photodiode array 409.

[0110] The photodiodes of each arrays thus detect time-resolved backscattered light from respective portions of the detection volume. Alternatively, the photodiode arrays may be replaced by individual photodiodes or by image sensors.

[0111] Based on the thus obtained signals, the system may detect insects in the respective parts of the detection module based on detected wing beat frequency, glossiness and/or melanisation, e.g. as described in WO 2018/182440.

[0112] Similarly, based on the recorded images by the image sensor 411, the system may determine additional or alternative indicators from which the presence and, optionally, identity of insects may be obtained. To this end, the process may utilise suitable computer vision techniques, such as object recognition and/or the detection and recognition of trajectories of insect movements, e.g. as described in co-pending International patent application No. PCT/EP2019/073119.

[0113] It has been found that a combination of different detector signals and, hence, different types of indicators allows for a particularly reliable detection of insects, including insects that are only difficult to detect based on e.g. wing beat frequency alone.

[0114] Nevertheless, it will be appreciated that other embodiments of detector modules may include only one or some of the above detectors, e.g. only an image sensor, or only an image sensor in combination with a single photodiode or photodiode array, or only a combination of two photodiodes or photodiode arrays. Also, in alternative embodiments, photodiodes or photodiode arrays may be configured to selectively detect light at alternative or additional wavelengths.

[0115] Yet further, while the embodiment of FIG. 4 utilises a combined optical system to direct light onto multiple sensors, alternative detector modules may comprise separate detectors, each having their own optical system, e.g. as illustrated in FIG. 5 below.

[0116] FIG. 5 schematically illustrates another example of a detector module of an insect sensor. In particular, FIG. 5 illustrates a detector module comprising three detectors 130A-C, respectively, each receiving light from a common detection volume that is illuminated by a common illumination module (not shown). In yet alternative embodiments, the detectors may receive light from different detection volumes which may be illuminated by a common or by respective illumination modules. Each of the detectors 130A-C include their own optical system, e.g. their own lenses etc.

[0117] In the present example, the detector module comprises a detector 130A for detecting light at a first wavelength and, optionally, at a first polarisation state. To this end, detector 130A may comprise a suitable band-pass filter, e.g. a filter selectively allowing light of 808 nm to reach a sensor of the detector, e.g. a photodiode or photodiode array. The detector 130A may further comprise a polarisation filter.

[0118] Detector 130B includes a digital camera, e.g. as described in connection with FIG. 3 or 4.

[0119] Detector 130C is configured for detecting light at a second wavelength (different and spaced apart from the first wavelength) and, optionally, at a second polarisation state. To this end, detector 130C may comprise a suitable band-pass filter, e.g. a filter selectively allowing light of 970 nm to reach a sensor of the detector, e.g. a photodiode or photodiode array. The detector 130C may further comprise a polarisation filter.

[0120] It will be appreciated, that alternative insect sensors may comprise additional or alternative detectors, e.g. fewer than three or more than three detectors.

[0121] FIG. 6 schematically illustrates another embodiment of an insect sensor. The insect sensor, generally designated by reference numeral 120, comprises a processing unit 140, a detector module 130 and an illumination module 131, all accommodated within a housing 110. In this example, the illumination module and the detector module are vertically aligned with each other and the illumination module is arranged below the detector module. However, other arrangements are possible as well.

[0122] The illumination module comprises an array of light-emitting diodes (LEDs) 161 and a corresponding array of lenses 161 for directing the light from the respective LEDs as a diverging beam 163 along an illumination direction 164. The array of light emitting diodes may comprise a first set of diodes configured to selectively emit light at a first wavelength range, e.g. at 810 nm+/−25 nm. The array of light emitting diodes may further comprise a second set of diodes configured to selectively emit light at a second wavelength range, different from the first wavelength range, in particular spaced-apart from the first wavelength range, e.g. at 980 nm+/−25 nm. In other embodiments, the array of light emitting diodes may include alternative or additional types of LEDs. For example, in some embodiments, the LEDs may be configured to emit broad-band visible, near-infrared and/or infrared light.

[0123] The detector module 130 comprises an optical system 132 in the form of a Fresnel lens. Alternative another lens system may be used. The detector module 130 includes an optical sensor 133, e.g. one or more photodiodes, such as an array of photodiodes, a CCD or CMOS sensor and the optical system directs light from the detection volume onto the optical sensor. In some embodiments, the optical system images an object plane 152 inside the illuminated volume onto the optical sensor. The field of view of the optical system and the depth of field of the optical system are configured such that the optical system directs light from a portion of the volume illuminated by the illumination module onto the optical sensor. The portion of the illuminated volume from which the optical system receives light such that it can be detected by the optical sensor and used for detection of insects defines a detection volume 150. The optical system 132 defines an optical axis 134 that intersects with the illumination direction 164 at a small angle, such as 10°.

[0124] For example, when an optical system is based on a camera lens having f=24 mm, f/2.8 and an optical sensor includes a 3/4″ image sensor, the detector module may be configured to focus on an object plane at 2 m distance from the lens, corresponding to a field of view of approximately 1.7 m×1.7 m and a depth of field of approximately 1.3 m, thus resulting in a detection volume of approx. 3.7 m.sup.3.

[0125] The detector module 130 is communicatively coupled to the processing unit 140 and forwards the captured radiation by the optical sensor to the processing unit. The processing unit 140 may include a suitably programmed computer or another suitable processing device or system. The processing unit receives the sensor signal, e.g. an image or stream of images and/or one or more time series of sensor signals from respective one or more photodiodes and, optionally, further detector signals from the detector module and processes the received sensor signal so as to detect and identify insects in the detection volume and output sensor data indicative of an estimated insect population.

[0126] FIG. 7 schematically illustrates an example of a sensor signal form a detector module of an embodiment of an insect sensor as described herein, e.g. an insect sensor as described in connection with any of the previous figures. In this example, the sensor signal from the detector module includes respective time series of detected light intensities at two narrow wavelength bands, e.g. as recorded by respective photodiodes provided with respective bandpass filters. In some embodiments the signal may be integrated or otherwise combined from multiple photodiodes, from an image sensor and/or the like.

[0127] In this example, time series 701 corresponds to detected light at 808 nm while time series 702 corresponds to detected light at 975 nm. However, other embodiments may use other wavelengths and/or more than two wavelengths or wavelength bands.

[0128] The processing unit of an insect sensor may process the times series to detect the presence of an insect in the detection volume and, optionally determine the type of detected insect. Alternatively, some or all of the signal and data processing may be performed by a data processing system external to the image sensor.

[0129] In the present example, the process implemented by the processing unit and/or an external data processing system may detect the presence of detected radiation above a predetermined threshold and/or determine a fundamental harmonic of the detected frequency response so as to detect the presence of an insect.

[0130] Alternatively or additionally the process may compute one or more indicators from which a type of insect may be determined. Examples of such indicators include a fundamental wing beat frequency (WBF), a body-wing ratio (BWR) and a melanisation (MEL).

[0131] For example, the process may compute the fundamental wing beat frequency (WBF) from the determined fundamental harmonic of the frequency response of a detected detection event. The process may compute the body-wing ratio as a mean ratio between a wing and body signal. The body signal may be determined as a baseline signal 711 of a detection event which represents the scattering from the insect with closed wings while the wing signal may be determined as the signal levels 712 at the peaks in scattering,

[0132] The melanisation ratio may be determined as a mean ratio between the signal strengths of the two recorded channels during a detection event.

[0133] From one or more of the above indicators, optionally in combination with other parameters, the process may determine a type of insect, e.g. a species of insects. This determination may be based on suitable look-up tables, on a classification model, such as a machine learning model, or the like.

[0134] Other examples of parameters detectable by embodiments of the insect sensor described herein and suitable for the detection and/or classification of flying or jumping insects include detected movement trajectories of insects within the detection volume, e.g. as described in co-pending International application No. PCT/EP2019/073119 the entire contents of which are hereby incorporated herein by reference.

[0135] Generally, embodiments of the insect sensor described herein provide a detection volume that is large enough for the detector module to observe a number of insects representative for the population density in the area, e.g. an area to be treated with pesticides. The detection volume is also small enough to be sufficiently uniformly illuminated so as to provide high signal strength at the image sensor.

[0136] Moreover, embodiments of the apparatus described herein provide fast observation times, e.g. so as to provide actionable input to a control system of a pesticide sprayer moving about an area to be treated.

[0137] Moreover embodiments of the apparatus described herein provide long enough observation times to be able to reliably classify flying insects.

[0138] FIGS. 8 and 9 illustrate examples of detection volumes. FIG. 8 schematically shows an example of a frusto-conical detection volume resulting from an illumination module emitting a diverging light beam with a generally circular cross section. FIG. 9 schematically illustrates an example of a frusto-pyramidal detection volume.

[0139] In order to make a spraying decision it is preferable that the recorded insect activity is representative for the area under consideration. In order to achieve this, a sufficiently high counting statistics is needed. The inventors have found that observation of at least 10, preferably at least 50, more preferably at least 100 insects allows for sufficiently representative insect activity.

[0140] The inventors have further found that typical numbers of insect activities observed in relevant areas of land are in the range from 0.2-2 insects pr. second pr. m.sup.3. When mounted on a moving vehicle, the detection volume V is moving forward with the speed, v of the moving vehicle. Assuming e.g. that the detection volume of the sensor is of the order 3 m.sup.3 and assuming an insect activity of 1 insect pr. second pr. m.sup.3, 33 seconds are needed in order to achieve a count of 100 insects. For a vehicle moving with 20 km/h this would mean that the vehicle has moved forward approx. 110 m. Considering typical lengths of spraying booms and considering that typical sizes of areas to be treated may exceed several tens of hectares, this provides for a sufficient detection resolution to support localized spraying decisions to be made for respective parts of an area of land to be treated.

[0141] As described herein, some embodiments of the insect sensor described herein record one or more time series of light scattering off one or more insects in flight at one or more wavelengths of the light. From the recorded time series, the wing beat frequency and/or ratio of scattering from body and wings, respectively, can be computed. However, in order to obtain a reliable and accurate detection result, the recorded time series should be long enough for multiple wingbeats to occur. The wingbeat frequency of insects in flight spans from around 100 Hz to around a 1000 Hz. In order to get more than 10 wings beats the time the insect is in the detection volume should, in the worst case, be preferably more than 100 ms. Similarly, a detection based on recorded flight trajectories is facilitated by observation times long enough to record trajectories of sufficient lengths.

[0142] Embodiments of the insect sensor described herein thus employ a detection volume shaped and sized to allow sufficiently long observation times, even when sensor is moving across an area of land.

[0143] A typical agricultural vehicle may move at a speed of e.g. 20 km/h or at similar speeds across an area of land. When moving at such a speed, during 100 ms the vehicle and, hence, the detection volume will have moved forward 0.55 m. Therefore, the extent of the detection volume along the direction of travel of the vehicle should preferably be larger than 1 m, such as larger than 2 m, such as larger than 5 m in order to ensure that insects are likely to remain inside the moving detection volume sufficiently long. For example, the length of the detection volume along the direction of travel may be less than 100 m, such as less than 50 m, such as less than 20 m.

[0144] Furthermore, as discussed above, it is preferred that the detection volume is of the order of, or larger than, 1 m.sup.3 such as larger than 1 m.sup.3. In order to achieve such a detection volume with a small and cost-efficient image sensor, it is preferred that the illumination module is carefully configured.

[0145] The illuminated detection volumes shown in FIGS. 8 and 9 both provide large detection volumes in the vicinity of the image sensor, i.e. allowing representative and local measurements.

[0146] The detection volumes shown in FIGS. 8 and 9 represent an overlap between an illuminated volume, illuminated by an illumination module of the insect sensor, and by a detectable volume from which a detector of the insect sensor receives light, i.e. the detectable volume may be defined by a field of view and depth of field of the detector. In one embodiment, the illumination module comprises one or more suitable light sources, e.g. one or more high-power LEDs, emitting light which is diverging from the illumination module so as to distribute light into a large volume. In one particular embodiment, the illumination module is configured to emit light with a full divergence angle in the horizontal plane that is larger than 5°, such as larger than 10° such as larger than 20°, while the vertical divergence is limited to angles smaller than 2° such as smaller than 5°. This embodiment is preferred as the resulting detection volume consequently will be optimized in space just above the crop. Moreover, in this embodiment, the amount of light which disappears upwards or into the crop is limited.

[0147] It is further preferred that the illumination module is configured so as to direct the illumination light along a center optical axis of the radiated light (i.e. along a direction of illumination) that points upwards in such an angle as to completely eliminate light form hitting the crop, e.g. between 1° and 30°, such as between 2° and 30°, such as between 5° and 20°.

[0148] An example of a detection volume resulting from such a diverging, pie-shaped, forward-upwardly directed illumination beam is illustrated in FIG. 9. In particular, FIG. 9 illustrates a 3D view of the detection volume 150 as well as a side view and a top view of the detection volume. In the example of FIG. 9, the distance do between the aperture of the detector module and the start of the detection volume is about 1 m. The distance d.sub.1 between the aperture of the detector module and the far end of the detection volume is about 10 m. The divergence angle θ.sub.vertical of the diverging light beam in the vertical direction (full angle) is about 4° while the divergence angle θ.sub.Horizontal in the horizontal direction (full angle) is about 20°. However, it will be appreciated that other embodiments may have different size and/or shape.

[0149] Generally, when the detection volume is positioned close to the insect sensor efficient illumination of the detection volume and reliable detection of small insects is facilitated. Moreover dispensing control based on the detection of local insect populations is facilitated. For example, the boundary of the detection volume closest to an aperture of the detector module may be between 10 cm and 10 m away from the aperture of the detector module, such as between 10 cm and 5 m, such as between 10 cm and 2 m. The boundary of the detection volume furthest from an aperture of the detector module may be between 3 m and 100 m away from the aperture of the detector module, such as between 5 m and 20 m, such as between 8 m and 12 m.

[0150] Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in art without departing from the spirit and scope of the invention as outlined in claims appended hereto.