EP4616172A1

EP4616172A1 - A system for determining presence and/or properties of duckweed

Info

Publication number: EP4616172A1
Application number: EP23798804.3A
Authority: EP
Inventors: Celine Catherine Sarah Nicole; Silvia Maria BOOIJ; Marcellinus Petrus Carolus Michael Krijn; Leonie Maria GEERDINCK; Maurice Alexander Hugo Donners
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2022-11-08
Filing date: 2023-11-02
Publication date: 2025-09-17
Also published as: WO2024099860A1

Abstract

A system is disclosed for determining a presence and/or properties of duckweed. The system comprises a pair of light sensors comprising a first light sensor and a second light sensor. The first light sensor is configured to measure a first value of radiant power of a first light component of light incident on the first light sensor. The second light sensor is configured to measure a second value of radiant power of a second light component of light incident on the second light sensor. The first light component is different from the second light component. The pair of light sensors is positioned below a water surface. Further, the system comprises a data processing system that is configured to determine, based on the measured first value and second value, the presence and/or one or more properties of duckweed on the water surface.

Description

A system for determining presence and/or properties of duckweed

FIELD OF THE INVENTION

This disclosure relates to a system for determining a presence and/or properties of duckweed. In particular to such system comprising a pair of light sensors, wherein each light sensor is configured to measure a radiant power of a different light component of light incident on the pair of light sensors. This disclosure further relates to a computer-implemented method and computer program for determining presence and/or properties of duckweed.

BACKGROUND

Duckweed is a small aquatic plant that is rich in protein, attracting a lot of attention recently since it is considered a main candidate to enable the transition from animalbased proteins to plant-based proteins. For food safety and human consumption, it has to be grown in controlled environments such as greenhouses and vertical farms. Its value largely depends on its nutritional content (mainly the composition and amount of amino acids in the proteins).

There are four families of duckweed; Lemna, Spirodela, Wolfia and Wolffiella. About 40 species are known worldwide. All of them have flat tiny, leaflike oval to round "fronds" from about 1 mm to less than 10 mm across. Some species develop rootlike structures which either stabilise the plant or assist to obtain nutrients where these are in dilute concentrations.

As each frond matures, it begins producing new buds in the meristematic zone near the centre of the frond. These buds grow into new fronds while still attached to the parent frond. When they mature, they break off. At this point, they have likely already begun producing fronds of their own. This cycle of reproduction allows duckweed to have a very fast rate of growth. It is capable of doubling in biomass over the course of 16 - 24 hours. Each frond can divide about 10 - 20 times during its lifetime. The protein production can be as much as 6x higher per hectare as compared to soybeans, for example. The amino acid composition of the proteins in duckweed mainly determines the nutritional value. In light of the opportunities that duckweed may provide, there is a continuous striving in the art for improving the yield of duckweed farms.

US 2015/0308948 Al discloses a photo-coupled data acquisition system and method for determining biomass of marine organisms in a water medium. Article “Trading offspring for survival: high duckweed cover decreases reproductive potential and stimulates elongation in the submerged macrophyte Chara globularis Thuillier” by Stijn Van Onsem et al discloses a study on the effects of complete duckweed cover on growth and reproductive fitness of macroalga in a pond mesocosm experiment. US 2012/0155714 Al discloses vegetative indices for measuring multilayer microcrop density and growth, wherein microcrop may be duckweed.

SUMMARY

To that end, a system is disclosed for determining a presence and/or properties of duckweed. The system comprises a pair of light sensors comprising a first light sensor and a second light sensor. The first light sensor is configured to measure a first value of radiant power of a first light component of light incident on the first light sensor. The second light sensor is configured to measure a second value of radiant power of a second light component of light incident on the second light sensor. The first light component is different from the second light component. The pair of light sensors is positioned below a water surface.

Further, the system comprises a data processing system that is configured to determine, based on the measured first value and second value, the presence and/or one or more properties of duckweed on the water surface.

Duckweed grows so fast that it is difficult to keep under control in the growth system. The plant doesn’t represent so much a challenge to grow but reproducibility and predictability of the growth is important and the need of automation is very present.

When harvested from a pond, for example, the remaining duckweed in the pond form patches of non-uniform groups of duckweed, meaning that the duckweed in each group has different duckweed properties. One group may have a high density of duckweed, while another may have a low density of duckweed. In order to be able to optimally apply supplemental light for growth and optimally enhance the nutritional content, the properties of duckweed at some location can be measured. To illustrate, localization of higher density versus lower density duckweed groups allows to tailor the supplemental light in order to optimally stimulate growth. As another example, duckweed layer thickness and canopy coverage needs to be monitored in order to predict product or harvest time or need to increase water flow rate or purity of the water (presence of algae), or to alert if something is going wrong in the production.

Preferably, the duckweed properties are measured in a straightforward and easy manner, without complex technology. A duckweed farm may look like a large scale water pond (minimum 5 cm deep water is needed) superposed on multiple layers in height. Using for example imaging systems, such as cameras, to determine the duckweed properties would be cumbersome, as it would require many cameras and a lot of image analyses. Also, the most efficient LEDs may be used to grow duckweed and therefore a DRBFr light (deep red blue far red) may be used to lower electricity usage and make the installation have a small or even negative carbon footprint (carbon dioxide can be used during growth making it sustainable). Under those lighting conditions, imaging devices such as cameras have a hard time to visualize growth continuously, including the human eye. Further, the fast growth of the duckweed would require a very high rate of imaging. Besides, plants that float do circulate and are not always at the same place on the growth surface.

In light of the above, the system disclosed herein is very beneficial. Relatively simple light sensors are used for measuring whether duckweed is present and/or for measuring the properties of the duckweed. The first light component and second light component interact differently with the duckweed (if present) on the water surface. The first light component is for example a red light component. The second component is for example a far red light component. Far red light, which may be understood as light having a wavelength between 700 - 780 nm, is relatively badly absorbed by duckweed, relative to light having other wavelengths, such as red light, which may be understood as light having a wavelength between 600 - 700 nm. Thus, far red light has relatively a high transmissivity through duckweed.

Thus, if there is duckweed on the water surface between an illumination system and the sensor pair, wherein the illumination system generates a far red light component and another light component, such as a red light component, then the ratio between the radiant power of the far red light component originating from the light source and incident on the sensor pair and the radiant power of the red light component originating from the light source and incident on the sensor pair would have some value. However, if there would be no duckweed between the illumination system and sensor pair, then this ratio would be much different, because the radiant power of the red light component as incident on the sensor pair would be higher. Thus, the presence of duckweed can be quite accurately determined based on the aforementioned ratio. Further, it is easily understood that this ratio would change gradually with thicker or thinner layers of duckweed being present between the illumination system and sensor pair. Hence, the system also allows to determine properties such as layer thickness, density, amount of duckweed based on two respective values of two different light components, one of the light components being absorbed differently by duckweed than the other light component.

Preferably, the first and second light sensor are positioned relatively close to each other such that they receive light that has travelled through the same region on the water surface. It is understood that the first and second value contain information about the presence and/or properties of duckweed at that region on the water surface. In that sense, a sensor pair may be associated with its own region on the water surface through which light incident on the sensor pair in question has travelled.

Basically, the light incident on the first light sensor is the same as the light incident on the second light sensor.

The first and second light sensor are preferably positioned in the water or under the cultivation tray (assuming the cultivation tray is transparent to the light).

In an embodiment, the data processing system is configured to determine the one or more properties of the duckweed based on a ratio between the first value of radiant power and second value of radiant power.

This embodiment provides for a sensitive system, especially if the first light component is absorbed by the duckweed to a different extent than the second light component. If that is the case, then the ratio between the first and second value will vary significantly depending on the amount of duckweed that is present on the water surface, e.g. depending on whether or not duckweed is present at all.

In an embodiment, the determined one or more properties comprise an amount of the duckweed on the water surface.

Determining that duckweed is present on the water surface above the first and second light sensor, without determining specifically how much duckweed, may be understood as an example of determining an amount duckweed. Determining that duckweed is present may namely be understood as determining that the amount of present duckweed is higher than zero, which is an example of determining an amount of duckweed.

In an embodiment, the data processing system is configured to determine how much duckweed is present on the water surface above the first and second light sensor. As referred to herein, “on the water surface above a sensor pair” may be understood to refer to a region on the water surface through which the light that is incident on the sensor pair travels. In an embodiment, the determined amount is indicative of a layer thickness of the duckweed on the water surface.

As already indicated above, the layer thickness is an important parameter to know for determining effective supplemental lighting. Thicker layers of duckweed benefit from different supplemental lighting than thinner layers.

In an embodiment, the system comprises an illumination system that is configured to generate the light incident on the first and second sensor and illuminate the duckweed on the water surface with the generated light. The light is configured to stimulate duckweed growth. (As indicated above, the light comprises the first light component and second light component.)

Conveniently, red light and far red light are already typically used in a horticulture applications, so that this embodiment can be implemented simply by installing the sensor pair at appropriate locations.

In an embodiment, the first light sensor is a non-spatially resolved sensor and wherein the second light sensor is a non-spatially resolved sensor.

This embodiment is advantageous in that it allows to use relatively simple sensors for determining properties of the duckweed on the water surface, in particular whether duckweed is present above the light sensors or not. As referred to herein, a non- spatially resolved sensor may be understood as a sensor that cannot output spatially resolved data, such as images, and/or as a sensor not comprising a plurality of pixels.

In an embodiment, the first light sensor is a photodiode and the second light sensor is a photodiode. Each photodiode may be used in combination with a spectral filter.

In an embodiment, the system comprises a plurality of pairs of light sensors. In such embodiment, the data processing system is configured to, for each pair of light sensors, determine, based on a first value of radiant power of the first light component as measured by the first light sensor of the pair in question and a second value of radiant power of the second light component as measured by the second light sensor of the pair in question, one or more properties of the duckweed on the water surface above the pair of light sensors in question.

Each pair of light sensors should be understood to be a pair comprising a first light sensor and second light sensor described above, meaning that the first light sensor is configured to measure a value of radiant power of the first light component and that the second light sensor is configured to measure a value of radiant power of the second light component. Preferably, the pairs may be separated by at least 0.25 meters so that the properties of the duckweed can be determined over a relatively large area.

This embodiment is highly advantageous in that it allows to determine where in a duckweed cultivating system, e.g. wherein in a pond, which type of duckweed is present. This allows to locally provide effective supplemental lighting, for example, and/or to determine at which locations in the duckweed cultivating system the duckweed is ready for harvest, for example.

In an embodiment, the data processing system is configured to determine, based on the one or more properties of the duckweed as determined for each pair of light sensors, a water surface coverage indicative of a percentage of the water surface that is covered by the duckweed.

To illustrate, the data processing system may be configured to determine for each pair of light sensors, whether or not duckweed is at all present above the light sensor pair in question. Herewith, the data processing determines for a plurality of regions on the water surface, namely each region above a light sensor pair, whether or not duckweed is present. This allows to determine, e.g. estimate, how much of the water surface is covered by duckweed while using a relatively simple sensor system.

In an embodiment, the system comprises an illumination system for illuminating the duckweed on the water surface. In such embodiment, the data processing system is configured to control the illumination system based on the determined one or more properties of the duckweed.

To illustrate, the data processing system may be configured to determine, for each pair of light sensors, a layer thickness of the duckweed in the region on the water surface above the light sensor pair in question. The data processing system can thus determine in which regions on the water surface the duckweed is relatively thin and where it is thicker. The data processing system may then be configured to control the illumination such that grow light is provided to the duckweed sitting in the areas where the duckweed layer is relatively thin in order to stimulate growth of the duckweed in these areas. As referred to herein, grow light may be understood as light that is configured to stimulate growth of the duckweed.

In an embodiment, the system comprises a temperature control system that is configured to control a temperature of the water. In such embodiment, the data processing system is configured to control the temperature control system based on the determined one or more properties. In an embodiment, the system comprises a water flow control system that is configured to control a speed of water flow, wherein the data processing system is configured to control the water flow control system based on the determined one or more properties.

One aspect of this disclosure relates to a computer-implemented method for determining one or more properties of duckweed on a water surface. The method comprises receiving from a first light sensor a first value of radiant power of a first light component of light incident on the first light sensor. The method also comprises receiving from a second light sensor a second value of radiant power of a second light component of light incident on the first light sensor, the first light component being different from the second light component, wherein the first light sensor and second light sensor are positioned below the water surface on which duckweed is present such that at least part of the light incident on the first and second light sensor has passed through the duckweed. The method also comprises determining, based on the measured first value and second value, one or more properties of the duckweed on the water surface.

This computer-implemented method may comprise any of the steps that the data processing system described herein may be configured to perform.

One aspect of this disclosure relates to a computer program comprising instructions, when executed by a computer, cause the computer to carry out any of the computer-implemented methods described herein.

One aspect of this disclosure relates to a computer-readable storage medium having stored thereon any of the computer programs disclosed herein.

One aspect of this disclosure relates to a computer comprising a computer readable storage medium having computer readable program code embodied therewith, and a processor, preferably a microprocessor, coupled to the computer readable storage medium, wherein responsive to executing the computer readable program code, the processor is configured to perform any of the computer-implemented methods described herein.

One aspect of this disclosure relates to a computer program or suite of computer programs comprising at least one software code portion or a computer program product storing at least one software code portion, the software code portion, when run on a computer system, being configured for executing any of the computer-implemented methods described herein.

One aspect of this disclosure relates to a non-transitory computer-readable storage medium storing at least one software code portion, the software code portion, when executed or processed by a computer, is configured to perform any of the computer- implemented methods described herein.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, a method or a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system." Functions described in this disclosure may be implemented as an algorithm executed by a processor/microprocessor of a computer. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied, e.g., stored, thereon.

Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer readable storage medium may include, but are not limited to, the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of the present invention, a computer readable storage medium may be any tangible medium that can contain, or store, a program for use by or in connection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber, cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java(TM), Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor, in particular a microprocessor or a central processing unit (CPU), of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer, other programmable data processing apparatus, or other devices create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to 2022PF80166

10 produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

Moreover, a computer program for carrying out the methods described herein, as well as a non-transitory computer readable storage-medium storing the computer program are provided. A computer program may, for example, be downloaded (updated) to the existing data processing systems or be stored upon manufacturing of these systems.

Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise. Embodiments of the present invention will be further illustrated with reference to the attached drawings, which schematically will show embodiments according to the invention. It will be understood that the present invention is not in any way restricted to these specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the invention will be explained in greater detail by reference to exemplary embodiments shown in the drawings, in which:

FIG. 1A and IB illustrate a system for cultivating duckweed comprising a system for determining presence and/or properties of duckweed according to an embodiment;

RECTIFIED SHEET (RULE 91) ISA/EP FIG. 2 illustrates a system for cultivating duckweed comprising a system for determining, more granularly, presence and/or properties of duckweed according to an embodiment;

FIG. 3 illustrates a data processing system according to an embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

In the figures, identical reference numbers indicate identical or similar elements.

Duckweed floats on water. It is the smallest flowering plant in the world. Leaves multiply by budding at exponential growth (about 50% increase per day if conditions are met). A property of duckweed is that it easily absorbs heavy metals and other contaminants in the water. Because of this, for human consumption, a controlled environment with clean water supply and uncontaminated fertilizers is desired. Examples of such controlled environments are (semi-closed) environments such as greenhouses and vertical farms. A closed environment allows reuse of CO2 that is produced as a by-product by energy plants, for example.

Typically, relatively large surface areas are required for growing duckweed, such as ponds, or multilayer growth in greenhouses or vertical farms. Optimum growth at (water) temperatures for duckweed lies between 20 and 30 °C. Artificial light, also referred to as supplemental light, is preferably provided for photosynthesis. An advantage of duckweed is that relatively low light intensities are required (100 - 200 pmol/m²/s).

A vertical farm typically comprises a succession of growth layers positioned vertically in a greenhouse. Layer to layer distance can be rather small and restricted to the optimum distance with regards to number of lamps versus uniformity needed. With such vertical design the space can be optimally used and therefore the duckweed can also be safely isolated against air/water contaminants.

Duckweed grown under ideal circumstances has a protein content of 35-45% of the dry weight.

Fig. 1 A illustrates a top view of system 2 for cultivating duckweed, in particular a cultivating tray 5 in which duckweed (not shown) is grown on a water surface 4. The duckweed flows from region 3 to the right, as indicated by the arrows, to a harvesting system 8 that is configured to harvest the duckweed. As the duckweed moves left to right it grows and reproduces. The cultivating system comprises a system for determining the presence and/or properties of duckweed as described herein. Fig. 1 A shows an illumination system 6 that in the depicted embodiment comprises a plurality of light sources 6a - 6f. Preferably, each light source can be controlled separately, e.g. in the sense that the electromagnetic spectrum and/or radiant power of the light as generated by it can be controlled. Data processing system 100 may be configured to control the individual light sources by sending appropriate control signals to them.

The illumination system 6 is preferably configured to provide the supplemental lighting that stimulates the growth of the duckweed on the water surface 4. In particular, the lighting as generated by the illumination system 6 preferably comprises a red light component and a far red light component. As described above, the light from the illumination system 6, in particular form the individual light sources, will be incident on sensor pairs 10/12 which are described in more detail below. If there is duckweed between the light sources and sensor pairs 10/12, then at least some of the light will travel through the duckweed. If this happens, then the red light component is absorbed to a greater extent by the duckweed than the far red light component. It should be appreciated that although specifically a red light component and far red light component are described with reference to the figures, in principle any two light components can be used that interact differently with duckweed, e.g. that are absorbed differently by duckweed.

As indicated, the system for determining presence and/or properties of duckweed of Fig. 1A comprises a plurality of light sensor pairs, namely 10a/12a, 10b/12b, 10c/12c, 10d/l 2d and 10e/12e. Herein, 10a - lOe indicate the light sensors each of which is configured to measure a value of the radiant power of the red light component incident on it, and 12a - 12e indicate the light sensors each of which is configured to measure a value of the radiant power of the far red light component incident on it. Each light sensor of Fig. 1 A is a photodiode that is sensitive to the relevant light component.

Fig. IB shows a cross section of the cultivating tray along line A-A shown in Fig. 1A. Here, it can be seen that the pairs of light sensors 10/12 are positioned below water surface 4. Optionally, at least some, e.g. all, of the pairs can be positioned below the cultivating tray if the bottom surface of the tray is transparent.

Fig. IB indicates a region 14 on the water surface in which a group of relatively thin duckweed is present, a region 16 on the water surface 4 in which a group of relatively dense duckweed is present, a region 18 on the water surface 4 in which no duckweed is present, and a region 20 on the water surface in which relatively dense duckweed is present.

The light generated by the individual light sources will travel through these regions which (assuming that all individual light sources generate the same light having the red and far red light components) will lead to different red/far red ratios as measured by the pairs. To illustrate, the sensor pair 10a/12a will mainly receive light from light sources 6a and 6b. Light travelling from these light sources to sensor pair 10a/12a will travel through thin duckweed containing region 14. As a result, the red light component is not absorbed significantly, so that the sensor pair will receive both a relatively high radiant power of the red light component and a relatively high radiant power of far red light component. In contrast, sensor pair 10c/12c will mainly receive light from light sources 6c and 6d. Light from these sources will travel through region 16 which contains dense duckweed. As a result, the red light component is substantially absorbed by the duckweed, so that the sensor pair receives a relatively high radiant power for the far red light component (because far red light is not significantly absorbed by duckweed) and a relatively low radiant power for the red light component. Thus, the red/far red ratio for sensor pair 10a/12a is quite different from the red/far red ration of sensor pair 10c/12c. Based on this, can the data processing system determine an amount, e.g. a layer thickness, of the duckweed above each sensor pair.

Note that in the depicted example, sensor pair 1 Od/12d mainly receives light form sources 6d and 6e. Light from these sources travels through region 18 which contains no duckweed. Hence, the red light component would be even less absorbed and would be even higher than for sensor pair 10a/12a. Hence, the red/far red ratio would be highest for this sensor pair.

Because the plurality of sensor pairs together enable to determine for a plurality of regions on water surface 4 whether duckweed is present, a water surface coverage can be determined as well. Even further, the plurality of sensors allows to determine a speed of movement of groups of duckweed.

Based on the determined presence and/or properties of the duckweed, the time of harvest can for example be determined. To illustrate, the data processing system may determine that the duckweed in region 20 is ready for harvesting. Based on this determination can for example the flow speed from left to right be increased in order to ensure that the duckweed in region 20 reaches the harvesting system 8 fast.

The data processing system may also be configured to control the illumination system based on the determined one or more properties of the duckweed. To illustrate, based on the data processing system determining that region 18 does not contain duckweed, light source 6e may be controlled, depending on the use case, to provide supplemental light of high radiant powers in order to boost the growth of duckweed in region 18, or alternatively, to provide supplemental light of low radiant powers since the supplemental light in region 18 is not efficiently used.

The data processing system may also be configured to control a temperature control system that is configured to control a temperature of the water. Different duckweed properties ask for different water temperatures.

The data processing system may also be configured to control a water flow control system that is configured to control a speed of water flow. To illustrate, once the duckweed in region 20 has been harvested, the data processing may determine that the next to-be-harvested region does not contain very much duckweed. Based on this determination may the data processing system control the speed of water flow to be low, giving duckweed some more time to grow and reproduce.

Optionally, as indicted in Fig. IB, one or more sensor pairs are present above the water surface 4 (see optional sensor pair 10f/12f). Such a sensor pair above the water surface enables to perform a reference measurement of the radiant powers of the red light component and far red light component, and thus a reference measurement of the red/far red ratio. Such reference measurement may be important if the light that is incident on the water surface varies, e.g. due to the implementation of different light recipes or because varying sunlight is also incident on the water surface. Such reference measurement allows to determine more accurately a degree of absorption for both light components, and thus allows more accurate detection of duckweed and/or or more accurate determination of the duckweed properties.

Fig. 2 is a top view of a system for cultivating duckweed as well. The system for determining the presence and/or properties of duckweed in this embodiment comprises a plurality of sensor pairs that are distributed in the xy-plane so that a more detailed view of the presence and/or properties of duckweed can be determined.

Preferably, such embodiment also comprises an illumination system that can more granularly illuminate different regions of the water surface. To illustrate, the system may determine that below light sources 6a, 6e, 6f, 6g, relatively thin duckweed is present and control these light sources to generate light stimulating growth of thin duckweed, and may determine that below light source 6c, relatively dense duckweed is present and control light source 6c to generate light that is suitable for growing specifically dense duckweed. Fig. 3 depicts a block diagram illustrating a data processing system according to an embodiment.

As shown in Fig. 3, the data processing system 100 may include at least one processor 102 coupled to memory elements 104 through a system bus 106. As such, the data processing system may store program code within memory elements 104. Further, the processor 102 may execute the program code accessed from the memory elements 104 via a system bus 106. In one aspect, the data processing system may be implemented as a computer that is suitable for storing and/or executing program code. It should be appreciated, however, that the data processing system 100 may be implemented in the form of any system including a processor and a memory that is capable of performing the functions described within this specification.

The memory elements 104 may include one or more physical memory devices such as, for example, local memory 108 and one or more bulk storage devices 110. The local memory may refer to random access memory or other non-persistent memory device(s) generally used during actual execution of the program code. A bulk storage device may be implemented as a hard drive or other persistent data storage device. The processing system 100 may also include one or more cache memories (not shown) that provide temporary storage of at least some program code in order to reduce the number of times program code must be retrieved from the bulk storage device 110 during execution.

Input/output (VO) devices depicted as an input device 112 and an output device 114 optionally can be coupled to the data processing system. Examples of input devices may include, but are not limited to, a keyboard, a pointing device such as a mouse, a touch-sensitive display, light sensors as described herein, or the like. Examples of output devices may include, but are not limited to, a monitor or a display, speakers, an illumination system as described herein, individual light sources of an illumination system described herein, a temperature control system described herein, a water flow control system described herein, a harvesting system described herein, or the like. Input and/or output devices may be coupled to the data processing system either directly or through intervening I/O controllers.

In an embodiment, the input and the output devices may be implemented as a combined input/output device (illustrated in Fig. 3 with a dashed line surrounding the input device 112 and the output device 114). An example of such a combined device is a touch sensitive display, also sometimes referred to as a “touch screen display” or simply “touch screen”. In such an embodiment, input to the device may be provided by a movement of a physical object, such as e.g. a stylus or a finger of a user, on or near the touch screen display. A network adapter 116 may also be coupled to the data processing system to enable it to become coupled to other systems, computer systems, remote network devices, and/or remote storage devices through intervening private or public networks. The network adapter may comprise a data receiver for receiving data that is transmitted by said systems, devices and/or networks to the data processing system 100, and a data transmitter for transmitting data from the data processing system 100 to said systems, devices and/or networks. Modems, cable modems, and Ethernet cards are examples of different types of network adapter that may be used with the data processing system 100.

As pictured in Fig. 3, the memory elements 104 may store an application 118. In various embodiments, the application 118 may be stored in the local memory 108, the one or more bulk storage devices 110, or apart from the local memory and the bulk storage devices. It should be appreciated that the data processing system 100 may further execute an operating system (not shown in Fig. 3) that can facilitate execution of the application 118. The application 118, being implemented in the form of executable program code, can be executed by the data processing system 100, e.g., by the processor 102. Responsive to executing the application, the data processing system 100 may be configured to perform one or more operations or method steps described herein.

Various embodiments of the invention may be implemented as a program product for use with a computer system, where the program(s) of the program product define functions of the embodiments (including the methods described herein). In one embodiment, the program(s) can be contained on a variety of non-transitory computer-readable storage media, where, as used herein, the expression “non-transitory computer readable storage media” comprises all computer-readable media, with the sole exception being a transitory, propagating signal. In another embodiment, the program(s) can be contained on a variety of transitory computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., flash memory, floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. The computer program may be run on the processor 102 described herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of embodiments of the present invention has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The embodiments were chosen and described in order to best explain the principles and some practical applications of the present invention, and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS:

1. A system (2) for determining a presence and/or properties of duckweed, the system comprising a pair of light sensors (10/12) comprising a first light sensor (10) and a second light sensor (12), wherein the first light sensor (10) is configured to measure a first value of radiant power of a first light component of light incident on the first light sensor (10), and the second light sensor (12) is configured to measure a second value of radiant power of a second light component of light incident on the second light sensor (12), the first light component being different from the second light component, wherein the pair of light sensors (10/12) is positioned below a water surface (4), and a data processing system (100) that is configured to

- determine, based on the measured first value and second value, the presence and/or one or more properties of duckweed on the water surface (4).

2. The system (2) according to claim 1, wherein the data processing system (100) is configured to determine the one or more properties of the duckweed based on a ratio between the first value of radiant power and second value of radiant power.

3. The system (2) according to claim 1 or 2, wherein the determined one or more properties comprise an amount of the duckweed on the water surface (4).

4. The system (2) according to claim 3, wherein the determined amount is indicative of a layer thickness of the duckweed on the water surface (4).

5. The system (2) according to any of the preceding claims, wherein the first component is a red light component and/or wherein the second component is a far red light component.

6. The system (2) according to the preceding claim, further comprising an illumination system (6) that is configured to generate the light incident on the first and second sensor (10, 12) and illuminate the duckweed on the water surface (4) with the generated light, the light being configured to stimulate duckweed growth.

7. The system (2) according to any of the preceding claims, wherein the first light sensor (10) is a non-spatially resolved sensor and wherein the second light sensor (12) is a non-spatially resolved sensor.

8. The system (2) according to claim 7, wherein the first light sensor (10) is a photodiode and wherein the second light sensor (12) is a photodiode.

9. The system (2) according to any of the preceding claims, wherein the system (2) comprises a plurality of pairs of light sensors (10a/ 12a -10e/12e), wherein the data processing system (100) is configured to, for each pair of light sensors (10a/12a -10e/12e), determine, based on a first value as measured by the first light sensor (lOa-lOe) of the pair in question and a second value as measured by the second light sensor (12a-12e) of the pair in question, one or more properties of the duckweed on the water surface above the pair of light sensors (10a/12a -10e/12e) in question.

10. The system (2) according to claim 9, wherein the data processing system (100) is configured to determine, based on the one or more properties of the duckweed as determined for each pair of light sensors (10a/12a -10e/12e), a water surface coverage indicative of a percentage of the water surface (4) that is covered by the duckweed.

11. The system (2) according to any of the preceding claims, further comprising an illumination system (6) for illuminating the duckweed on the water surface

(4), wherein the data processing system (100) is configured to control the illumination system (6) based on the determined one or more properties of the duckweed.

12. The system (2) according to any of the preceding claims, further comprising a temperature control system that is configured to control a temperature of the water, wherein the data processing system (100) is configured to control the temperature control system based on the determined one or more properties.

13. The system (2) according to any of the preceding claims, further comprising a water flow control system that is configured to control a speed of water flow, wherein the data processing system (100) is configured to control the water flow control system based on the determined one or more properties.

14. A computer-implemented method for determining one or more properties of duckweed on a water surface (4), the method comprising receiving from a first light sensor (10) a first value of radiant power of a first light component of light incident on the first light sensor (10), and receiving from a second light sensor (12) a second value of radiant power of a second light component of light incident on the first light sensor (12), the first light component being different from the second light component, wherein the first light sensor (10) and second light sensor (12) are positioned below the water surface (4) on which duckweed is present such that at least part of the light incident on the first and second light sensor has passed through the duckweed, and determining, based on the measured first value and second value, one or more properties of the duckweed on the water surface (4).

15. A computer program comprising instructions, when executed by a computer, cause the computer to carry out the method according to claim 13.