System for providing light to plants

Abstract

System (1) for providing light (7) to plants (6), wherein the system (1) comprises: - a light source (2) configured to be positioned above the plants (6) to provide light (7) to the plants (6) in a vertical growth direction of the plants (6); - an optical arrangement (3) for adjusting an angle of radiation (β) of the light (7) in the vertical growth direction of the plants (6); and - a control unit (4) for controlling the optical arrangement (3), wherein - the control unit (4) is configured to control the optical arrangement (3) to change the angle of radiation (β) of the light (7) depending on a height (H) of the plants (6).

Description

The present invention relates to a system for providing light to plants.A light source, such as a luminaire for providing light to plants, may be referred to as a horticultural light source or plant light source or horticultural luminaire or plant luminaire. Such a light source may be used to aid plant growth, such as plants grown indoors (e.g., a greenhouse, a vertical farm, etc.) or outdoors (e.g., in a field, etc.). Such light sources can be used especially in an agricultural context to increase the chance on a healthy crop, i.e. to achieve a healthy crop. For example, when plants are grown indoors, natural sunlight striking the plants may be reduced or unavailable at all. In the case of growing outdoor plants in an environment with reduced sunlight, sunlight that shines on the plants may also be reduced. Reduction or unavailability of sunlight has a negative effect on the growth of plants because the plants require sunlight for photosynthetic required for plant growth.To balance this, a light source, such as one or more lights, may be used to provide light to the plants to aid in the growth of the plants. Such a light source may emit light specifically adapted to support plant growth. For example, the light emittable by the light source may comprise or be photosynthetically active radiation light (PAR light). In addition, the light emittable by the light source can comprise or be ultraviolet radiation (UV radiation), such as UV-A, UV-B and / or UV-C radiation. The UV radiation (e.g., the UV-A radiation) may help the light source imitate sunlight and may have a positive effect on the plants in addition to the PAR light. For example, mimicking sunlight may help lengthen a photosynthetic period in an outdoor environment in which the natural sunlight period is decreased, and thus may lengthen a period during which plants perform photosynthetic and thus are capable of growing.The UV-A radiation can not only assist or induce production of proteins, amino acids and enzymes in plants, but it can also improve insect fouling of plants. UV-B radiation and UV-C radiation can be used to clean (e.g., sterilize) water and surfaces. When used for plants, the UV-B radiation and / or UV-C radiation may be used to eliminate pathogens on the plants, which may support healthy plant growth of the plants. In addition, UV radiation from insects, such as bees, is used for navigation to flowers. Thus, if UV radiation is not available in an indoor environment such as a greenhouse, it may be difficult for insects used to dust the plants to find the plants, particularly the flowers of the plants to be dusted.FIG. 3 schematically shows two different states of an example of providing light to plants. In FIG. 3, an example of a light source 2 for providing light 7 to plants 6 growing in a crop region 8 (e.g. a bed) is shown. By way of example, three plants 6 are shown which grow in a vertical direction. On the left side of FIG. 3, an example of an initial height of the plants 6 is shown. On the right side of FIG. 3, an example of a height of the plants 6 after a growth period (e.g., days and / or months depending on the growth rate of the plants 6) has elapsed is shown. The right hand side of Figure 3 possibly shows a condition just before plants 6 are ready to be harvested. In order to provide the plants 6 with light 7 during the complete growth period from the initial height to the height at which they are possibly ready for harvesting, the light source 2 emits the light at an angle of radiation α that allows the light 7 to reach all the plants 6 during the complete growth period.This has the disadvantage that at the beginning of the growth period, i.e., when the plants have a low height (e.g., the initial height shown on the left side of FIG. 3 ), light not only reaches the plants 6 in the cultivation area 8 but also reaches an area outside the cultivation area 8. Thus, the light 7 can reach a person (e.g. working) present in the area outside the mounting area 8. This may be disadvantageous because the person can be blinded or made blinded by the light 7. In addition, in the case that the light 7 comprises UV radiation, the light 7 may be harmful to the person (e.g. damage the eyes of the person). The terms "made blind by light" and "blind by light" may be used interchangeably.Therefore, it is an object of the present invention to provide illumination for plants without the above-described disadvantages. It is a particular object of the present invention to provide illumination for plants without disturbing persons present in the vicinity of the plants.These and other objects, which will become apparent upon reading the following description, are achieved by the subject matter of the independent claim. The dependent claims refer to preferred embodiments of the invention.According to the invention, there is provided a system for providing light to plants. The system includes a light source configured to be positioned over the plants to provide light to the plants in a vertical growth direction of the plants. Further, the system comprises an optical arrangement for adjusting an angle of the radiation of the light in the vertical growth direction of the plants and a control unit for controlling the optical arrangement. The control unit is configured to control the optical arrangement to change the angle of the radiation of the light depending on a height of the plants.In other words, the present invention proposes to adapt the light emission of a light source for providing light to plants to the height of the plants by changing the angle of the radiation of the light emitted by the light source depending on the height of the plants. To this end, in addition to the light source, an optical arrangement and a control unit for controlling the optical arrangement are provided, whereby a system for providing light to plants is formed.Thus, the system enables the light emission of the light source to be varied such that the light emitted by the light source merely reaches or impinges on the plants (e.g., a surface of the plants). This allows the light emitted from the light source to have an angle of radiation that would normally reach an area outside of a crop area (e.g., beet for the plants) without plants being present to be shielded or prevented by the plants (due to their height) from reaching the area outside of the crop area. As a result, the light emitted from the light source does not move to and impinges upon persons who are outside the mounting area in the vicinity of the mounting area. Thus, the persons are not blinded or damaged by the light (e.g. in the case that the light comprises UV radiation).In light of the above, the system for providing light to plants is advantageous compared to the light source of Figure 3 for providing light to plants.The plants may be plants grown for food, medical, fuel or other known purposes. The plants may be plants of a monoculture, i.e. of the same plant species. The plants may be grown or grown in a crop area (e.g., beet for plants). That is, the light source may be configured to be positioned over the crop area comprising the plants and thus over the plants to provide the plants with the light in a vertical growth direction of the plants. The plants may be located in an interior (e.g., a greenhouse, a vertical farm, etc.) or outdoors (e.g., in a field, etc.). Thus, the system may be a system for providing light to plants in an indoor environment and / or an outdoor environment.The light source can be referred to as horticultural light source or plant light source. The light source may be configured to emit light useful for plant growth of the plants or to support plant growth of the plants. The passages "emit light" and "emit light" can be used synonymous with the passage "emit light". For example, the light source may be configured to emit photosynthetically active radiation (PAR) light. Additionally or alternatively, the light source may be configured to emit ultraviolet (UV) radiation. The UV radiation may comprise UV-A radiation, UV-B radiation and / or UV-C radiation. In other words, the light that can be provided to the plants by the light source can comprise PAR light and / or UV radiation. Additionally or alternatively, the light source may emit any other radiation (electromagnetic waves) useful for healthy growth of the plants. The light emittable by the light source may have a spectrum optimized with respect to supporting growth of the plants (e.g. color spectrum). The light source may be configured to alter the type of radiation emitted by the light source (e.g., the spectrum). For example, the light source may be configured to emit PAR light and, additionally or alternatively, UV radiation for some periods of time.The light source may comprise one or more light emitting diodes (LEDs) for providing light to the plants. For this purpose, one or more arbitrary LED types can be used. Additionally or alternatively, the light source may comprise any one or more other types of illumination means known in the art for providing light to the plants.The controller may include or be a processor, microprocessor, controller, microcontroller, application specific circuitry (ASIC), field programmable gate array (FPGA), and / or any other known type of controller. The optical arrangement may be configured to be electrically controlled by the control unit. The control unit may be configured to provide control signals to the optical arrangement to control the optical arrangement to change the angle of the radiation of the light depending on the height of the plants. For this purpose, the control unit can be configured to communicate with the optical arrangement (e.g. to provide control signals to the optical arrangement) via a wireless and / or wired communication. The control unit and the optical arrangement can be electrically connected to one another. The term "radiation angle" may be used as a synonym for the term "angle of radiation".The control unit may be configured to control the light source, i.e. the light emission of the light source. For example, the control unit may be configured to control a light intensity of the light source and / or to switch the light source on and off. Optionally, the control unit may be configured to control the type of radiation emitted by the light source. For example, the control unit may be configured to control the light source to emit PAR light and, additionally or alternatively, UV radiation for certain periods of time.Optionally, the control unit is configured to control the optical arrangement to change the angle of the radiation of the light such that the angle of the radiation is the greater the greater the height of the plants.This allows all plants, e.g. the tip of all plants, to have light provided, regardless of the height of the plants. This allows, for example, the surface of all plants to have light provided regardless of the height of the plants.The control unit may be configured to control the optical arrangement to change the angle of radiation of the light such that the smaller the height of the plants, the smaller the angle of radiation. This allows the lighting to be adjusted to the plants in case the height of the plants decreases again during the growth phase of the plants (e.g. due to harvesting).The control unit may receive information about the height of the plants from outside the system (e.g. an operator or a control center for monitoring plant growth) (e.g. via a wireless communication and / or a wired communication). Using this information, the control unit can determine the angle of the radiation. For example, the control unit may be configured to calculate the angle of the radiation by inputting the information on the height of the plants into an algorithm. Additionally or alternatively, the control unit may be configured to determine the angle of the radiation by using the information on the height of the plants and a look-up table or database in which the respective angles of the radiation are stored for different heights of the plants. The algorithm or the look-up table or database can be adapted to the installation of the system, in particular the light source and the optical arrangement, with respect to the plants (e.g. to the position and orientation of the light source and the optical arrangement with respect to the plants).Optionally, the control unit is configured to control the optical arrangement to adjust a starting angle of the radiation of the light depending on a starting height of the plants.Optionally, the control unit is configured to control the optical arrangement to change the angle of the radiation depending on the height of the plants by controlling the optical arrangement to change the angle of the radiation depending on a time elapsed since a starting time.To this end, the control unit may be configured to calculate the angle of the radiation by inputting the elapsed time into an algorithm. The algorithm may be adapted to the plant species of the plants and optionally to one or more environmental factors (e.g. humidity, temperature, nutrition, light intensity, etc. at the crop area of the plants) having an influence on the growth rate of the plants. Additionally or alternatively, the control unit may be configured to determine the angle of the radiation by using the elapsed time and a look-up table or database in which the respective angles of the radiation are stored for different elapsed times. The look-up table or database may store, for each value of the different elapsed times, different values of the angle of radiation for different plant species and optionally one or more environmental factors (e.g. humidity, temperature, nutrition, light intensity, etc. at the crop area of the plants) having an influence on the growth rate of the plants.The control unit may be configured to control the optical arrangement to change the angle of radiation of the light such that the angle of radiation becomes larger the longer the elapsed time.The control unit may be configured to repeatedly update the angle of radiation of the light and control the optical arrangement to adjust the updated angle of radiation of the light. The control unit may be configured to periodically update the angle of radiation of the light and control the optical arrangement to adjust the updated angle of radiation of the light. Additionally or alternatively, the control unit may be triggered from outside the system (e.g. an operator or a control centre for monitoring plant growth) to determine the angle of radiation of the light depending on the height of the plants (i.e. update the angle of radiation) and to control the optical arrangement to adjust the determined (i.e. updated) angle of radiation of the light.The control unit may be configured to receive information about the angle of radiation of the light from outside the system (e.g. an operator or a control centre for monitoring plant growth) and to control the optical arrangement to change the angle of radiation of the light depending on the received information.The controller may be configured to communicate with the exterior of the system (e.g., an operator or a plant growth monitoring control center) via wireless and / or wired communication.Optionally, the system comprises a measuring unit for measuring the height of the plants. The control unit may be configured to control the optical arrangement to change the angle of the radiation depending on the height of the plants by controlling the optical arrangement to change the angle of the radiation depending on the measured height of the plants.The control unit may be configured to control the measurement unit. The control unit may be configured to communicate wirelessly and / or in a wired manner with the measurement unit. The measurement unit may be electrically connected to the control unit. The measuring unit may be a part (optionally at least partially) of the control unit.For example, the measurement unit may include a camera for capturing images of the plants and a processing unit for determining the height of the plants by processing the images. Additionally or alternatively, the measuring unit can comprise multiple illumination means and multiple light sensors, which can be arranged vertically in pairs on the crop area of the plants in order to provide photoelectric relays at different heights. The measuring unit may be configured to determine the height of the plants depending on which of the photoelectric relays detects the presence of plants. Additionally or alternatively, the measurement unit may comprise one or more light detection and ranging (LIDAR) sensors for measuring the height of the plants. Additionally or alternatively, the measurement unit may be configured for any other known method for measuring the height of the plants.The measurement unit may be configured to measure the height of the plants by measuring the height of at least one plant of the plants.Additionally or alternatively, the measuring unit can be configured to measure the height of multiple plants, statistically process or evaluate the measured heights of the multiple plants and output a result of the statistical processing as the measured height of the plants. The static processing can be carried out by the control unit, wherein the measuring unit can provide the measured heights of the multiple plants to the control unit. For example, the statistical processing of the measured heights may include determining a maximum height among the measured heights and outputting or using the maximum height as the measured height of the plants. Alternatively, the static processing of the measured heights may comprise calculating an average of the measured heights or of two or more of the largest heights of the measured heights and outputting or using the average height as the measured height of the plants.The measurement unit may be configured to measure the height of the plants by measuring the height of at least one plant of the plants disposed at a boundary of an area including the plants.The area comprising the plants may be referred to as the crop area(s). For example, it may be a beet for plants, an area of a field, etc.Optionally, the measuring unit is configured to be positioned above the plants in a vertical direction and to measure the height of the plants by measuring a distance to at least one plant of the plants in the vertical direction.The measurement unit may be configured to determine the height of the plants by using its own height with respect to a reference surface, e.g., the surface of a region (crop region) in which the plants are arranged, and the measured distance. The distance from a plant can be understood to mean the distance from the tip of the plant. For example, the measurement unit may subtract the measured distance from its own height to calculate the height of the at least one plant and output or use this calculated height as the measured height of the plants.Optionally, the optical arrangement comprises at least one optical element configured to change the angle of radiation of the light by changing a focal length of the optical arrangement.The control unit may be configured to transmit to the optical arrangement a control signal indicative of the desired angle of radiation and the optical arrangement may be configured to determine the focal length of the optical arrangement to achieve the desired angle. To this end, the optical arrangement may be configured to calculate the focal length using an algorithm and / or to use a look-up table or database comprising different focal lengths for different angles of radiation. The algorithm or the look-up table or database can be adapted to the installation of the system, in particular the light source and the optical arrangement, with respect to the plants (e.g. to the position and orientation of the light source and the optical arrangement with respect to the plants).The control unit may be configured to transmit a control signal to the optical arrangement indicative of the focal length for achieving a desired angle of radiation. For this purpose, the control unit can be configured according to the optional features mentioned above with regard to determining the focal length for a desired angle of the radiation.The control unit may be configured to control the optical arrangement to change the angle of radiation of the light by controlling the optical arrangement (e.g. the at least one optical element) to change the focal length of the optical arrangement. Optionally, the control unit may be configured to control the changing of the angle of the radiation of the light by controlling the at least one optical element to change its focal length and thus the focal length of the optical arrangement.The optical arrangement may comprise a lens system of one or more lenses for adjusting the angle of radiation of the light provided by the light source. Thus, the above-mentioned focal length may be the focal length of the lens system.The at least one optical element may be at least one liquid crystal lens.The at least one liquid crystal lens may be configured to change the angle or radiation of the light that can be provided to the plant from the light source by changing the focal length of the optical arrangement. The focal length of the optical arrangement may be the focal length of the at least one liquid crystal lens.The control unit may be configured to change the angle of radiation of the light provided to the plants from the light source by changing the focal length of the at least one liquid crystal lens. For this purpose, the control unit can be configured to transmit control signals to the optical arrangement. For example, the control unit may be configured to change the focal length of the at least one liquid crystal lens and thus of the optical arrangement (i.e. to change or regulate the focal point of the at least one liquid crystal lens) by applying a voltage to electrodes of the liquid crystal lens or triggering an application of such a voltage, wherein a liquid crystal layer is arranged between the electrodes. The at least one liquid crystal lens may be any known focus adjustable liquid crystal lens.Additionally or alternatively, the at least one optical element can be at least one movable lens.The at least one movable lens may be configured to change the angle or radiation of the light that can be provided to the plants from the light source by changing the focal length of the optical arrangement. The focal length of the optical arrangement may be the focal length of the at least one movable lens.The control unit may be configured to change the angle of radiation of the light that can be provided from the light source to the plants by changing the focal length of the at least one movable lens. For this purpose, the control unit can be configured to transmit control signals to the optical arrangement. For example, the control unit may be configured to change or regulate the focal length of the at least one movable lens (i.e. the focal point of the at least one movable lens) and thus to change the optical arrangement by electrically controlling a movement of the at least one movable lens towards or away from the light source. This changes a distance between the light source and the at least one movable lens. This can change the focal length of the optical assemblyOptionally, the control unit is configured to control the light source to maintain the light intensity of the light constant while controlling the optical arrangement to change the angle of radiation of the light.This ensures that the plants are always supplied with the same light intensity and thus light energy. Therefore, this promotes healthy plant growth of the plants. Since the system allows to avoid light being emitted outside a crop area of the plants, there is no need to reduce the light intensity to reduce person glare or damage to a person by the light (e.g., in the case that the light includes UV radiation) when the person is near the crop area.Optionally, the system is a light for providing the light to the plants.The luminaire can be referred to as horticultural luminaire or plant luminaire.In order to achieve the system according to the first aspect of the present invention, some or all of the optional features described above may be combined with each other.A method for providing light to plants is described. The method comprises providing the light, in a vertical growth direction of the plants, from a light source positioned above the plants to the plants; and controlling an optical arrangement to change the angle of the radiation of the light depending on a height of the plants.The above description with respect to the system according to the present invention applies correspondingly to the method.The method achieves the same advantages as the system according to the invention.To achieve the method, some or all of the optional features described above may be combined with each other.It should be noted that all of the devices, elements, units, and means described in the present application may be implemented in software or hardware elements or any type of combination thereof. All steps performed by the various entities described in the present application, as well as the described functionalities to be performed by the various entities, are intended to mean that the respective entity is adapted or configured to perform the respective steps and functionalities.The invention will now be described by way of example with reference to the accompanying figures, in which FIG. 1 schematically shows a block diagram of an example of a system according to an embodiment of the invention for providing light to plants; FIG. 2 schematically shows two different states of the system of FIG. 1 ; and FIG. 3 schematically shows two different states of an example of providing light to plants.In the figures, corresponding elements have the same reference numerals. The proportions and dimensions of the elements shown in the figures do not represent the components of the system to scale, but are chosen merely to describe the structure and function of the system.FIG. 1 schematically shows a block diagram of an example of a system according to an embodiment of the invention for providing light to plants. The system of Fig. 1 is an example of the system according to the present invention. The description of the system applies correspondingly to the system of FIG. 1.The system 1 of FIG. 1 is a system for providing light 7 to plants 6. optionally, the system 1 may be a luminaire for providing light to plants, i.e. a horticultural luminaire or plant luminaire. As shown on the right side of FIG. 1, the system 1 comprises a light source 2 configured to be positioned over the plants 6 to provide light 7 to the plants 6 in a vertical growth direction of the plants 6. Further, the system 1 comprises an optical arrangement 3 for adjusting an angle of the radiation β of the light 7 in the vertical growth direction of the plants 6. In addition, the system 1 comprises a control unit 4 for controlling the optical arrangement 3. The control unit 4 is configured to control the optical arrangement 3 to change the angle of the radiation β of the light 7 depending on a height H of the plants 6.As shown in FIG. 1, the optical arrangement 3 and optionally the light source 2 may be electrically connected to the control unit 4, for example by means of a wired bus (e.g. data bus). The control unit 4 may be configured to control the light source 2, e.g. the light emission of the light source 2. for example, the control unit 4 may be configured to control the light intensity of the light 7 emittable by the light source 2 and / or to switch the light source 2 on and off. Optionally, the control unit 4 may be configured to control the type of radiation emitted by the light source 2.The plants 6 may be located in a crop area 8 (e.g., a bed, an area of a field, etc.). The number of plants 6 shown in FIG. 1 is only exemplary. The plants 6 may optionally be plants of a monoculture.The light source 2, the optical arrangement 3 and the control unit 4 may be implemented as described above with respect to the system of the invention. For further details on possible implementations of the light source 2, the optical arrangement 3 and the control unit 4, reference is thus made to the corresponding description of the system of the invention.As shown in Fig. 1, the system may optionally comprise a measuring unit 5 for measuring the height H of the plants 6. Alternatively or additionally, the control unit 4 may receive information about the height H of the plants from outside the system 1 (e.g. from an operator or a control center for monitoring plant growth). As shown in FIG. 1, the optional measurement unit 5 may be electrically connected to the control unit 4 by a wired bus (e.g., data bus), for example. The optional measurement unit 5 may be implemented as described above with respect to the system of the invention. For further details on possible implementations of the measuring unit 5, reference is thus made to the corresponding description of the system of the invention.The control unit 4 may be configured to control the optical arrangement 3 to change the angle of the radiation β depending on the height H of the plants 6 by controlling the optical arrangement 3 to change the angle of the radiation β depending on the measured height of the plants 6 (measured by the optional measurement unit 5). Additionally or alternatively, the control unit 4 may be configured to control the optical arrangement 3 to change the angle of the radiation β depending on information on the height of the plants 6 received from outside the system 1.Thus, the control unit 4 may be configured to directly use the height H of the plants 6 (e.g. in the form of a measured height and / or information on the height H received from outside the system 1) to change the angle of the radiation β of the light 7 that may be provided to the plants by the light source 2. Additionally or alternatively, the control unit 4 may be configured to use a time elapsed since an initial time for changing the angle of the radiation β of the light 7. That is, the control unit 4 is optionally configured to control the optical arrangement 3 to change the angle of the radiation β of the light 7 depending on the height H of the plants 6 by controlling the optical arrangement 3 to change the angle of the radiation β depending on a time elapsed since a starting time.For further information on how the control unit 1 can be configured to change the angle of radiation β of the light 7 (which plants 6 can be provided by the light source 2) depending on information on the height of the plants 6 receivable from outside the system 1, the measured height of the plants 6 (measured by the measuring unit 5) and / or at a time elapsed since an initial time, reference is made to the corresponding description of the system of the present invention. In the following, with reference to Fig. 1, an example of a possible implementation of the system with respect thereto will be described, which does not limit the present invention to this implementation.The plants 6 shown on the left side of FIG. 1 are the same plants 6 shown on the right side of FIG. 1. They are duplicated for the purpose of providing a good illustration only for a description of an example of a possible function of the optional measurement unit 5 and the control unit 4 of the system 1 on the left side.The measurement unit 5 may be configured to measure the height H of the plants 6 by measuring the height of one of the plants 6. This can be the case when the plants 6 are of the same plant species, i.e. they are plants of a monoculture. In this case, it can be assumed that the plants grow equally under the same conditions, and therefore it can be assumed that the plants 6 of the same cultivation region 8 are of the same height H. Alternatively, the measurement unit 5 may be configured to measure the height H of the plants 6 by measuring the height of multiple plants 6. In this case, the measurement unit 5 or the control unit 4 may be configured to statistically process or evaluate the measured heights of the multiple plants and output or use a result of the statistical processing as the measured height H of the plants 6.Optionally, the measurement unit 5 may be configured to measure the height H of the plants by measuring the height of at least one plant 6 aof the plants 6 disposed at a boundary of the area 8 (may be referred to as a growing area) including the plants 6. This may be advantageous since the plants 6a at the boundary of the cultivation region 8 are the plants which shield or prevent the light 7 provided by the light source 2 from reaching the bottom of a region outside the cultivation region 8 if the height of these plants 6a is high enough for this.As shown in FIG. 1, the measurement unit 5 may be positioned above the plants 6 in a vertical direction to measure the height H of the plants 6 by measuring a distance D to at least one plant of the plants 6 in the vertical direction. The measurement unit may determine the height H of the plants by using its own height H 0 with respect to the surface of the crop area 8 in which the plants 6 are arranged and the measured distance D. For example, the measurement unit 5 may subtract the distance D from its own height H0to calculate the height H of the at least one plant and use this calculated height as the measured height H of the plants 6.FIG. 2 schematically shows two different states of the system of FIG. 1. the state shown on the left side of FIG. 2 shows the plants 6 at an earlier point in time compared to the state shown on the right side of FIG. 2, i.e. on the right side the plants 6 have grown compared to the left side.On the left side of FIG. 2, the height H of the plants 6 is equal to a first height H 1 that is smaller than the height H of the plants 6 shown on the right side of FIG. 2 that are equal to a second height H 2 (H 1<H 2). As a result, a first distance D 1 to the plants 6 (in particular to the tip of the plants 6) that can be measured by the measurement unit 5 when the plants have the first height H 1 is greater than a second distance D 2 to the plants 6 that can be measured by the measurement unit 5 when the plants have the second height H 2 (D 1>D 2).The control unit 4 (not shown in FIG. 2 ) may be configured to control the optical arrangement 3 to change the angle of the radiation β of the light 7 that can be provided by the light source 2 to the plants 6 such that the greater the height H of the plants 6, the greater the angle of the radiation β (and optionally vice versa). Therefore, the angle of radiation β of the light 7 emitted to the plants 6 having the first height H 1 becomes equal to a first radiation angle β 1 which is smaller than a second radiation angle β 2 of the light 7 illuminated to or provided to the plants 6 having the second height H 2 (β 1< β 2).As indicated by FIG. 1, changing the angle of the radiation β of the light 7 depending on the height H of the plants 6 by means of the optical arrangement 3 enables light to be provided only to the plants 6 in the cultivation region 8 without light reaching a region outside the cultivation region 8. Namely, the light 7 that can be provided from the light source 2 is shielded by the plants 6, in particular the plants 6 a, at the boundary of the cultivation region 8, from reaching a ground in a region outside the cultivation region 8. Therefore, the system of FIGS. 1 and 2 can provide light to plants without dazzling or damaging persons present adjacent to the cultivation area 8 in an area outside the cultivation area 8.To change the angle of the radiation β of the light 7 which can be provided from the light source 2 to the plants 6, as already outlined above, the optical arrangement 3 is provided.For this purpose, the optical arrangement 3 can comprise at least one optical element (not shown in FIGS. 1 and 2 ) configured to change the angle of the radiation β of the light 7 by changing a focal length of the optical arrangement 3. The at least one optical element may be at least one liquid crystal lens. Additionally or alternatively, the at least one optical element can be at least one movable lens. The control unit 4 may be configured to control the changing of the angle of the radiation β of the light 7 by controlling the at least one optical element to change its focal length and thus the focal length of the optical arrangement.For further details, e.g. additional or alternative optional implementations, of the system of Figures 1 and 2, reference is made to the description of the system according to the invention.In the claims and specification, the word "comprising" does not exclude other elements or steps, and indefinite articles such as "a" or "an" do not exclude a plurality. A single element or other entity may perform the functions of multiple entities or items recited in the claims. The fact that certain measures are recited in the mutually different dependent claims alone does not indicate that a combination of these measures cannot be used in an advantageous implementation.

Claims

A system (1) for providing light (7) to plants (6), the system (1) comprising - a light source (2) configured to be positioned over the plants (6) to provide light (7) to the plants (6) in a vertical growth direction of the plants (6), - an optical arrangement (3) for adjusting an angle of the radiation (β) of the light (7) in the vertical growth direction of the plants (6), and - a control unit (4) for controlling the optical arrangement (3); wherein - the control unit (4) is configured to control the optical arrangement (3) to change the angle of the radiation (β) of the light (7) depending on a height (H) of the plants (6).The system (1) according to claim 1, wherein - the control unit (4) is configured to control the optical arrangement (3) to change the angle of the radiation (β) of the light (7) such that the greater the height (H) of the plants (6), the greater the angle of the radiation (β).The system (1) according to claim 1 or 2, wherein - the control unit (4) is configured to control the optical arrangement (3) to adjust a starting angle of the radiation of the light (7) depending on a starting height of the plants (6).The system (1) according to any of the preceding claims, wherein - the control unit (4) is configured to control the optical arrangement (3) to change the angle of the radiation (β) depending on the height (H) of the plants (6) by controlling the optical arrangement (3) to change the angle of the radiation (β) depending on a time elapsed since a starting time.The system (1) according to claim 4, wherein - the control unit (4) is configured to control the optical arrangement (3) to change the angle of the radiation (β) of the light (7) such that the longer the elapsed time, the greater the angle of the radiation (β).The system (1) according to any one of the preceding claims, wherein - the system (1) comprises a measurement unit (5) for measuring the height (H) of the plants (6), and - the control unit (4) is configured to control the optical arrangement (3) to change the angle of the radiation (β) depending on the height (H) of the plants (6) by controlling the optical arrangement (3) to change the angle of the radiation (β) depending on the measured height (H) of the plants (6).The system (1) according to claim 6, wherein - the measuring unit (5) is configured to measure the height (H) of the plants (6) by measuring the height (H) of at least one plant of the plants (6).The system (1) according to claim 6 or 7, wherein - the measuring unit (5) is configured to measure the height (H) of the plants (6) by measuring the height (H) of at least one plant (6a) of the plants (6) arranged at a boundary of an area comprising the plants (6).The system (1) according to any one of claims 6 to 8, wherein - the measuring unit (5) is configured to be positioned above the plants (6) in a vertical direction and to measure the height (H) of the plants by measuring a distance (D) to at least one plant of the plants (6) in the vertical direction.The system (1) according to any of the preceding claims, wherein - the optical arrangement (3) comprises at least one optical element configured to change the angle of the radiation (β) of the light (7) by changing a focal length of the optical arrangement (3).The system (1) according to claim 10, wherein - the at least one optical element is at least one liquid crystal lens.The system (1) according to claim 10 or 11, wherein - the at least one optical element is at least one movable lens.The system (1) according to any of the preceding claims, wherein - the control unit (4) is configured to control the light source (2) to keep the light intensity of the light (7) constant while controlling the optical arrangement (3) to change the angle of the radiation (β) of the light (7).The system (1) according to any of the preceding claims, wherein - the system (1) is a light for providing light (7) to the plants (6).

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