Ultraviolet lighting

Abstract

An ultraviolet (UV) lighting panel 100 for a mobile autonomous agricultural system comprising: a UV light source; and a plurality of shade elements arranged relative to the UV source to direct UV ligh

Description

Field The present disclosure concerns ultraviolet lighting panels, mobile autonomous agricultural systems comprising ultraviolet lighting panels, methods of agriculture using ultraviolet lighting panels, and kits of parts comprising ultraviolet lighting panels. Background Ultraviolet (UV) light can stimulate the growth of agricultural crops. UV light (e.g. UV-C light) can also sanitise crops by, for example, damaging or killing pathogenic microorganisms such as fungi, moulds and bacteria. UV light can therefore be used as an adjunct to, or replacement for, pesticide use in agriculture. However, excessive exposure to UV light is dangerous for humans and can cause, for example, damage to human skin and eyes. The use of UV light in agriculture therefore presents a safety risk to people working in or around the crops. Summary of invention According to a first aspect, there is provided an ultraviolet (UV) lighting panel for a mobile autonomous agricultural system, the UV lighting panel comprising: a UV light source configured to generate UV light; and a plurality of shade elements arranged relative to the UV light source to direct the UV light in a primary illumination direction and to restrict emission of UV light from the UV lighting panel outside the primary illumination direction. It will be appreciated that the UV lighting panel (for example, when installed in the mobile autonomous agricultural system) may be used to direct UV light onto a crop. In use, when the UV lighting panel is arranged to direct the UV light in the primary illumination direction towards a crop, a human standing in the vicinity of the UV lighting panel may be at least partially shielded by the plurality of shade elements from exposure to UV light emitted from the UV lighting panel outside the primary illumination direction. Throughout this specification and the appended claims, the terms “ultraviolet light” and “UV light” are used to refer to electromagnetic radiation in the ultraviolet (UV) portion of the electromagnetic spectrum, i.e. having a wavelength from about 10 nm to about 400 nm. The primary illumination direction may be the direction in which the UV light is directed in order to illuminate a crop (for example, positioned relative to the mobile autonomous agricultural system). The plurality of shade elements may be arranged relative to the UV light source to restrict emission of UV light from the UV lighting panel in at least one direction outside the primary illumination direction. For example, the plurality of shade elements may be arranged relative to the UV light source to restrict emission of UV light from the UV lighting panel in two or more directions outside the primary illumination direction. The plurality of shade elements may restrict emission of UV light from the UV lighting panel in one or more directions outside the primary illumination direction which include at least one or more directions substantially orthogonal to the primary illumination direction (i.e. inclined with respect to the primary illumination direction by about 90°), for example, which include one or more directions inclined with respect to the primary illumination direction by no less than about 80°, 70°, 60°, 50°, 45°, 40°, 30° or 20°. Restricting emission of UV light from the UV lighting panel outside the primary illumination direction may comprise substantially reducing the amount of UV light emitted by the lighting panel in the one or more directions outside the primary illumination direction. For example, restricting emission of UV light from the UV lighting panel outside the primary illumination direction may comprise reducing the amount of UV light emitted by the lighting panel in the one or more directions outside the primary illumination direction by at least about 50%, for example, at least about 75%, or at least about 80%, or at least about 90%, or at least about 95%. The amount of UV light emitted by the lighting panel in a given direction may be quantified as the intensity of UV light measured at a fixed distance from the UV lighting panel along the given direction using a suitable ultraviolet light sensor. The reduction in UV light emitted from the UV lighting panel outside the primary illumination direction caused by the plurality of shade elements may be quantified by comparing the intensity of UV light measured at a fixed distance from the UV lighting panel along a given direction outside the primary illumination direction using a suitable ultraviolet light sensor with the intensity of UV light measured at said same distance from the UV lighting panel along the same given direction using the same ultraviolet light sensor when the plurality of shade elements are removed from the UV lighting panel. Restricting emission of UV light from the UV lighting panel outside the primary illumination direction may comprise substantially blocking emission of UV light from the UV lighting panel outside the primary illumination direction. The primary illumination direction may be substantially orthogonal to a lighting surface of the UV lighting panel (i.e. a surface of the UV lighting panel provided with the UV light source and typically arranged to face the crop in use). That is to say, the primary illumination direction may extend along a normal to the lighting surface of the UV lighting panel. The primary illumination direction may vary across the lighting surface of the UV lighting panel, for example, because the UV lighting panel is curved. The plurality of shade elements may be spaced apart from one another, for example, in a shading array. The plurality of shade elements may be spaced apart from one another (for example, in the shading array) and may be arranged relative to the UV light source to permit passage of the UV light between said plurality of shade elements in the primary illumination direction (while restricting emission of UV light from the UV lighting panel in the one or more directions outside the primary illumination direction). The shade elements may be spaced apart from one another by at least about 10 mm, for example, at least about 15 mm, or at least about 20 mm, or at least about 25 mm. The shade elements may be spaced apart from one another by no more than about 50 mm, for example, no more than about 45 mm, or no more than about 40 mm, or no more than about 35 mm. The shade elements may be spaced apart from one another by from about 10 mm to about 50 mm, for example, from about 15 mm to about 45 mm, or from about 20 mm to about 40 mm, or from about 25 mm to about 35 mm. The shade elements may be equally spaced apart from one another. For example, each shade element may be spaced apart from each adjacent shade element by at least about 10 mm, for example, at least about 15 mm, or at least about 20 mm, or at least about 25 mm. Each shade element may be spaced apart from each adjacent shade element by no more than about 50 mm, for example, no more than about 45 mm, or no more than about 40 mm, or no more than about 35 mm. Each shade element may be spaced apart from each adjacent shade element by from about 10 mm to about 50 mm, for example, from about 15 mm to about 45 mm, or from about 20 mm to about 40 mm, or from about 25 mm to about 35 mm. Each of the shade elements may be substantially elongate. For example, each of the shade elements may be an elongate fin. The dimensions of each of the substantially elongate shade elements (e.g. elongate fins) may be defined in terms of a length, a width measured perpendicular to the length, and a thickness measured perpendicular to both the length and the width. It may be that the length of each substantially elongate shade element (e.g. elongate fin) is substantially greater than both the width and the thickness. For example, the length of each substantially elongate shade element (e.g. elongate fin) may be at least 50 (for example, at least 100, or at least 200) times the corresponding thickness and at least 5 (for example, at least 10, or at least 15) times the corresponding width. Moreover, it may be the width of each substantially elongate shade element (e.g. elongate fin) is substantially greater than the thickness. For example, the width of each substantially elongate shade element (e.g. elongate fin) may be at least 5 (for example, at least 10, or at least 15) times the corresponding thickness. Each substantially elongate shade element (e.g. elongate fin) may have a length no less than about 400 mm, for example, no less than about 500 mm, or no less than about 600 mm. Each substantially elongate shade element (e.g. elongate fin) may have a length no greater than about 2000 mm, for example, no greater than about 1500 mm, or no greater than about 1200 mm, or no greater than about 1000 mm. Each substantially elongate shade element (e.g. elongate fin) may have a length from about 400 mm to about 2000 mm, for example, from about 500 mm to about 1500 mm, or from about 500 mm to about 1200 mm, or from about 500 mm to about 1000 mm, or from about 600 mm to about 1000 mm. Each substantially elongate shade element (e.g. elongate fin) may have a width no less than about 10 mm, for example, no less than about 20 mm, or no less than about 30 mm. Each substantially elongate shade element (e.g. elongate fin) may have a width no greater than about 60 mm, for example, no greater than about 50 mm, or no greater than about 40 mm. Each substantially elongate shade element (e.g. elongate fin) may have a width from about 10 mm to about 60 mm, for example, from about 20 mm to about 50 mm, or from about 30 mm to about 40 mm. Each substantially elongate shade element (e.g. elongate fin) may have a thickness no less than about 0.1 mm, for example, no less than about 0.5 mm, or no less than about 1 mm, or no less than about 2 mm. Each substantially elongate shade element (e.g. elongate fin) may have a thickness no greater than about 10 mm, for example, no greater than about 5 mm, or no greater than about 4 mm, or no greater than about 3 mm, or no greater than about 2 mm. Each substantially elongate shade element (e.g. elongate fin) may have a thickness from about 0.1 mm to about 10 mm, for example, from about 0.5 mm to about 5 mm, or from about 1 mm to about 4 mm, or from about 1 mm to about 3 mm. Each substantially elongate shade element (e.g. elongate fin) may be arranged relative to the UV light source such that the substantially elongate shade element (e.g. elongate fin) extends away from the UV light source (i.e. in the primary illumination direction) in the width dimension (i.e. such that the width dimension is aligned with the primary illumination direction). Thus, each substantially elongate shade element (e.g. elongate fin) may have a width in the primary illumination direction from about 20 mm to about 50 mm and a thickness perpendicular to the primary illumination direction from about 0.5 mm to about 5 mm. The plurality of shade elements (e.g. the plurality of elongate fins) may be arranged substantially parallel to one another in the shading array. Each shade element (e.g. elongate fin) may be made of a resilient (and typically flexible) material, for example, an elastomeric polymeric material such as rubber (including natural and / or synthetic rubber). Use of a resilient (and typically flexible) material may enable flexing of shade elements when brushing against crops or equipment without damage to the UV lighting panel, crops or equipment. The UV lighting panel may comprise a plurality of UV light sources configured to generate UV light. The plurality of shade elements may be arranged relative to the plurality of UV light sources to direct the UV light in the primary illumination direction and to restrict emission of UV light from the UV lighting panel outside the primary illumination direction. The or each UV light source may be elongate. In embodiments in which each shade element is elongate (e.g. an elongate fin), each elongate shade element (e.g. elongate fin) may extend longitudinally in a direction substantially orthogonal to a longitudinal axis of the or each elongate UV light source. The UV lighting panel may comprise a plurality of said elongate UV light sources spaced apart from one another to form a lighting array. In embodiments in which each shade element is elongate (e.g. an elongate fin), each elongate shade element (e.g. elongate fin) may extend longitudinally in a direction substantially orthogonal to a longitudinal axis of each elongate UV light source in the lighting array. The elongate UV light sources of the lighting array may be arranged substantially parallel to one another. In some embodiments, the UV lighting panel comprises: a lighting array comprising a plurality of elongate UV light sources spaced apart from one another (and optionally arranged parallel to one another) and configured to generate UV light; and a shading array comprising a plurality of elongate shade elements (e.g. elongate fins) spaced apart from another (and optionally arranged parallel to one another) and arranged relative to the lighting array to direct the UV light in a primary illumination direction and to restrict emission of UV light from the UV lighting panel outside the primary illumination direction. The UV lighting panel may comprise a support. The or each UV light source and the plurality of shade elements may be mounted on the support. The or each UV light source may be releasably mounted on the support, for example, to enable replacement or repair of the UV light sources. The plurality of shade elements may be releasably mounted on the support, for example, to enable replacement or repair of the shade elements. The plurality of shade elements may be releasably mounted on the support by way of a quick release mechanism. For example, each shade element may be releasably mounted on the support byway of one or more rods positioned in brackets on the support. Each rod may extend through a corresponding aperture in each shade element. The or each UV light source may be a UV light bulb. For example, the or each UV light source may be a UV light tube (i.e. a tubular UV light bulb). The or each UV light bulb (e.g. UV light tube) may have a power from about 5 W to about 20 W, for example, from about 5 W to about 15 W, or from about 10 W to about 15 W, or from about 10 W to about 13 W. The UV lighting panel may generate an irradiance of from about 15 W / m2 to about 40 W / m2, for example, from about 10 W / m2 to about 30 W / m2. In some cases, the UV light may comprise one or more of ultraviolet A (UV-A), ultraviolet B (UV-B) or ultraviolet C (UV-C) light. It will be appreciated that the terms “ultraviolet A light” and “UV-A light” are used to refer to electromagnetic radiation in the ultraviolet A portion of the electromagnetic spectrum, i.e. having a wavelength from about 315 nm to about 400 nm. It will further be appreciated that the terms “ultraviolet B light” and “UV-B light” are used to refer to electromagnetic radiation in the ultraviolet B portion of the electromagnetic spectrum, i.e. having a wavelength from about 280 nm to about 315 nm. It will further be appreciated that the terms “ultraviolet C light” and “UV-C light” are used to refer to electromagnetic radiation in the ultraviolet C portion of the electromagnetic spectrum, i.e. having a wavelength from about 100 nm to about 280 nm. The or each UV light source may be configured to generate (e.g. predominantly) ultraviolet C (UV-C) light. That is to say, the or each UV light source may be a UV-C light source configured to generate (e.g. predominantly) UV-C light. UV-C light may be particularly useful in sanitising crops. The material from which the or each shade element (e.g. elongate fin) is made is typically resistant to UV (e.g. UV-C) light. It will be appreciated that a material which is resistant to UV (e.g. UV-C) light blocks transmission of UV (e.g. UV-C) light therethrough and is also typically resistant to UV (e.g. UV-C) induced degradation, at least over reasonable timescales (for example, at least 6 months of exposure to UV (e.g. UV-C) light). At least a portion of the UV lighting panel may have a semiarch (i.e. half-arch) profile in cross section. For example, it may be that UV lighting panel as a whole has a semiarch profile in cross section. Alternatively, it may be that a first (e.g. lower) portion of the UV lighting panel has a substantially rectangular profile in cross section and that a second (e.g. upper) portion of the UV lighting panel has a semiarch profile in cross section. A semiarch profile may facilitate mounting of the UV lighting panel within an arch-shaped mobile unit of a mobile autonomous agricultural system. The UV lighting panel may comprise a power supply for supplying power to the UV light source. Alternatively, the UV lighting panel may comprise a power connection for connection to an external power supply for supplying power to the UV light source. According to a second aspect, there is provided a mobile autonomous agricultural system comprising: a powered mobile unit for carrying agricultural equipment, and configured to move along rows of crops; a UV lighting panel according to the first aspect; and a controller configured to control the travel of the mobile unit and operation of the UV lighting panel. The mobile autonomous agricultural system may further comprise: at least one laser curtain sensor configured to project a laser curtain away from the mobile unit; and a safety module configured to generate a safety output in response to determining that the laser curtain is interrupted, wherein the safety output comprises a signal to disable the UV light source. The mobile autonomous agricultural system may further comprise a plurality of laser curtain sensors distributed around the mobile unit configured together to form the laser curtain. Each laser curtain sensor may be configured to project a respective laser plane which overlaps with at least one other laser plane to form the laser curtain. The controller may be configured to delay operation of the UV lighting panel until a predetermined period of time has passed after receiving a signal to operate the UV lighting panel. For example, the controller may be configured to delay operation of the UV lighting panel until at least about 5 seconds, for example, at least about 10 seconds, have passed after receiving a signal to operate the UV lighting panel. The mobile unit may comprise an arch profile extending along an axial direction. The UV lighting panel may be mounted within the arch profile. The UV lighting panel may have a semiarch profile in cross section. The mobile autonomous agricultural system may comprise two UV lighting panels according to the first aspect mounted within the arch profile on opposing sides. For example, each of the two UV lighting panels may have a semiarch profile in cross section. The mobile autonomous agricultural system may comprise a power supply for supplying power to the or each UV lighting panels. The mobile autonomous agricultural system may further comprise at least one robot arm configured to perform agricultural tasks, and the safety output may further comprise a signal to control the robot arm to stop. The mobile autonomous agricultural system may have any features described in published United Kingdom Patent Application GB 2610184 A (A mobile autonomous agricultural system and method), which is hereby incorporated by reference in its entirety. According to a third aspect, there is provided a method of agriculture comprising illuminating a crop with UV light using a UV lighting panel according to the first aspect or using a mobile autonomous agricultural system according to the second aspect. The method may comprise (e.g. a controller) delaying operation of the UV lighting panel (i.e. to generate UV light) until a predetermined period of time has passed after receiving a signal to operate the UV lighting panel. For example, the method may comprise (e.g. the controller) delaying operation of the UV lighting panel until at least about 5 seconds, for example, at least about 10 seconds, have passed after receiving a signal to operate the UV lighting panel. The method may comprise disabling the UV light source in response to determining that the laser curtain of the second aspect is interrupted. According to a fourth aspect, there is provided a kit of parts for assembling the UV lighting panel according to the first aspect. The kit comprises at least the or each UV light source, the plurality of shade elements and a support to which the or each UV light source and the plurality of shade elements are mountable. The plurality of shade elements may be releasably mountable on the support. For example, it may be that the support comprises brackets, the kit of parts further comprises one or more rods, and each shade element is releasably mountable on the support by way of the one or more rods when positioned in the brackets. The kit may further comprise any other components of the UV lighting panel described hereinabove in relation to the first aspect. The skilled person will appreciate that, except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive, any feature described herein may be applied to any aspect and / or combined with any other feature described herein. Figures Embodiments will now be described by way of example only, with reference to the Figures, in which: Figure 1 shows perspective views of a mobile autonomous agriculture system including an ultraviolet lighting panel (a) with a plurality of shade elements and (b) with the shade elements removed, thus exposing a plurality of ultraviolet lighting tubes; Figure 2 shows (a) a side view and (b) a front view of the mobile autonomous agricultural system of Figure 1; Figure 3 shows a front view of an ultraviolet lighting panel used in the mobile autonomous agricultural system of Figures 1 and 2; Figure 4 shows a side view of the ultraviolet lighting panel of Figure 3; Figure 5 shows a perspective view of the ultraviolet lighting panel of Figure 3; and Figure 6 shows another perspective view of the ultraviolet lighting panel of Figure 3. Detailed description Figures 1 and 2 show a mobile autonomous agricultural system 10 comprising a powered mobile unit 12. The mobile autonomous agricultural system 10 is configured to operate along rows 40 of crops (illustrated in Figure 2 (b), with each row 40 shown extending into the page) to perform agricultural tasks, such as harvesting, husbandry, sanitisation or monitoring the crops. In this example, the mobile unit 12 comprises an arch profile extending along an axial direction 50. In other words, at any point in the axial direction, a cross section of the mobile unit 12 comprises an arch profile. In this example, distal ends of arms of the arch are fixed to powered wheels 14 (which are pivotable with respect to the mobile unit 12 for steering) and extend away from the wheels 14 to an apex of the arch. In this example, each distal end of the arch is attached to two wheels 14, such that the whole arch is supported on the ground by a total of four wheels 14. It will be appreciated that in other examples, any suitable number of wheels may be used, or any other suitable device for propelling the mobile unit 12 may be used. The arch profile of the mobile unit 12 defines an inner zone 16, in the form of a tunnel extending along the axial direction 50, within which agricultural equipment may be disposed such that it is protected from damage. The agricultural equipment in this example includes a robot arm 22 and two ultraviolet (UV) lighting panels 100 and 102. The arch profile further allows the mobile unit 12 to traverse along rows 40 of crops, which are raised above the ground on posts (for ease of accessibility), with a single row 40 of crops extending through the inner zone 16 along the axial direction 50, and simultaneously accessible by the agricultural equipment from two sides of the row 40. In some examples, the crops may be disposed on the ground, and the mobile unit may comprise any suitable profile to access the crops on the ground. The mobile autonomous agricultural system 10 comprises a controller 20 which is configured to control the travel of the mobile unit 12. In this example, in an autonomous mode, the controller 20 is configured to autonomously move the mobile unit 12 along the rows 40 of crops, and between the rows 40, where the rows may comprise a straight line of crops, or any other line of crops with a non-linear profile. In other words, the controller 20 is configured to align the axial direction 50 of the inner zone 16 of the mobile unit 12 with a first row 40 of crops such that the arch profile is centred and aligned with the row 40 of crops, and to move the mobile unit 12 to approach the first row 40, and continue to move the mobile unit 12 along the row 40, with the first row 40 received in the inner zone 16 until it reaches an end of the row 40. At the end of the row 40, the controller 20 is configured to control the mobile unit 12 to exit the row 40, travel a predetermined distance away from the row 40, and traverse towards an adjacent row 40 to begin the process again with the adjacent row 40. In this example, the mobile autonomous agricultural system 10 may also be operated in a manual mode, in which a user can manually control the movement of the mobile unit 12, for example up to a first row 40, at which point the user may activate the autonomous mode. In this example, the autonomous mode of the mobile autonomous agricultural system 10 provides for autonomous movement between adjacent rows 40 of crops, in a single polytunnel of plants, and also from one polytunnel to another. UV lighting panel 100 is shown in more detail in Figures 3 to 6. UV lighting panel 102 has an equivalent structure. UV lighting panel 100 comprises a support frame 104 to which a plurality of UV-C lighting tubes 106 and shade elements (also known as baffles or fins) 108 are mounted. The support frame 104 has a semiarch profile in cross-section perpendicular to the axial direction, as shown in Figure 4. This semiarch profile conforms to the arch profile of the mobile unit 12 so that the support frame 104 fits within and is mountable on the interior of the mobile unit 12 facing the inner zone 16. The support frame 104 has a plurality of lighting tube brackets 110 configured to hold the plurality of UV-C lighting tubes 106 in place against the support frame 104 and to connect the lighting tubes 106 to a power supply (not shown). The support frame 104 also has a plurality of shade brackets 112 configured to retain the plurality of shade elements 108 in place via a plurality of mounting rods 114. Each of the plurality of shade elements 108 is a rubber fin having a semiarch profile in the axial direction, as shown in Figure 4. Each rubber fin 108 is generally thin and elongate. In the example shown, each rubber fin 108 has a length L of about 710 mm, a width W of about 34.5 mm and a thickness T of about 2 mm. The rubber fins 108 are arranged parallel to one another and spaced evenly apart from one another in a shading array with a spacing S between adjacent fins of about 29 mm. When connected to the power supply and activated, the UV-C lighting tubes 106 are configured to generate UV-C light to illuminate the crops 40, for example, to sanitise the crops 40 by killing mould, fungus and / or bacteria and / or to stimulate crop growth. Because the rubber fins 108 are generally thin and spaced apart from one another, the majority of UV-C light generated by the UV-C lighting tubes is able to pass between the rubber fins 108 in a primary illumination direction D towards the crops 40. However, the rubber fins 108 prevent much of the generated UV-C light from escaping from the lighting panel in directions outside of the primary illumination direction, and particularly in the axial direction 50. Nearby humans are therefore shielded from UV-C light emitted by the lighting panel during use. The rubber fins 108 therefore function as a guard for the UV lighting panel 100. Each of the rubber fins 108 is provided with a plurality of apertures 116 configured for mounting the rubber fins 108 on the mounting rods 114. When the mounting rods 114 extend through the apertures 116 in the fins 108 and through the brackets 112 of the support frame 104, the rubber fins 108 are mounted securely on the support frame 104. However, the rubber fins 108 may be easily and quickly dismounted from the support frame 104 for replacement or repair by sliding the rods 114 through the apertures 116 and the brackets 112. The brackets 112, apertures 116 and rods 114 therefore function together as a quick release mechanism for the fins 108. In the example shown, the UV-C lighting tubes 106 are 11.5 W UV-C lighting tubes configured to generate UV-C light. However, it will be appreciated that these lighting tubes 106 could be replaced with any suitable UV light sources for generating UV light for sanitising crops and / or stimulating crop growth. In the example shown, the shade elements 108 are provided in the form of generally thin and elongate rubber fins. However, it will be appreciated that these shade elements 108 could take any suitable shape and size, as long as the shade elements 108 are configured (e.g. shaped and positioned) to permit transmission of the generated UV light in the primary illumination direction and to restrict or block transmission of generated UV light outside the primary illumination direction (e.g. in the axial direction of the mobile unit 12). In the example shown, the shade elements 108 are made of rubber. Rubber is a suitable material because it is resistant to UV-C light and because it is a resilient, flexible material (which enables flexing of the baffles when brushing against crops or equipment without damage to the UV lighting panel, crops or equipment). However, it will be appreciated that any suitable UV resistant (and optionally resilient) material may be used. In the example shown, the shade elements 108 are mounted on the support frame 104 by way of the mounting rods 114 and brackets 112, which function as a quick release mounting mechanism. However, it will be appreciated that the shade elements 108 may be attached to the support frame 104 by any other suitable means. In the example shown, the UV lighting panel 100 has a semiarch profile designed to fit within the arch profile of the mobile unit 12. However, it will be appreciated that the UV lighting panel may take any suitable shape. For example, the UV lighting panel may be a flat panel (e.g. it may have a rectangular profile in cross section in the axial direction) or it may have an arch profile. In the example shown, the mobile unit 12 is covered by a cover 120 which also helps to prevent UV light escaping from the inner zone 16 (particularly in a direction opposing the primary illumination direction). However, it will be appreciated that in other examples, the UV lighting panel 100 itself is provided with a cover, for example, mounted on or integrally formed with the support frame 104. During use of the UV lighting panels 100 and 103, it is important that people around the mobile autonomous agricultural system 10 are shielded from excessive exposure to UV light. This is achieved primarily through use of the shade elements 108. However, as an additional safety feature, the controller 20 may be configured to delay operation of the UV lighting panels 100 and 103 until a predetermined period of time has passed after receiving a signal (e.g. from a user) to operate the UV lighting panels. This may provide a user or other nearby personnel with sufficient time to move away from the mobile unit 12 before the UV lighting panels are activated. For example, the controller may be configured to delay operation of the UV lighting panel until at least about 5 seconds (for example, at least about 10 seconds) have passed after receiving a signal to operate the UV lighting panel. As a further additionally safety feature, the agricultural system 10 may be provided with a plurality of laser curtain sensors 18 distributed around the mobile unit 12. In this example, there are six laser curtain sensors 18, with one corner laser curtain sensor 18a disposed at each of four corners of the mobile unit 12, which in this example is by each wheel 14, and one side laser curtain sensor 18b disposed on each side of the mobile unit 12 between two wheels 14 in the axial direction 50. The laser curtain sensors 18 are each configured to project a respective laser plane towards the ground, and each laser plane overlaps with at least one other laser plane, so as together to form a laser curtain surrounding the mobile unit 12. Each laser curtain sensor 18 can detect when its respective laser plane is interrupted by sensing reflected waves of emitted laser beam light. Specifically, the two side laser curtain sensors 18b project a laser plane close to vertically downwards such that the respective laser planes are not interrupted by the wheels 14 if the wheels are rotated by 90 degrees, and so that the respective laser planes are not interrupted by adjacent rows 40 when the mobile unit 12 is moving along a row 40. This helps to reduce the risk of erroneous generation of a safety output. When the distance between rows is larger, the side laser curtains may be angled away from the mobile unit, or when the distance between the rows is narrow and constraining, and the wheels are smaller or do not rotate, then the side laser curtains may be angled towards the mobile unit. Each corner laser curtain sensor 18a is configured to project a laser plane angled downwards with respect to the horizontal to project away from the mobile unit 12, such that each laser plane from the corner laser curtain sensors 18a overlaps with the laser plane from an adjacent corner laser curtain sensor 18a, and so that the laser plane from each side laser curtain sensor 18b overlaps (or meets) with the laser planes from the adjacent corner laser curtain sensors 18a. This particular configuration of laser curtain sensors 18 ensures that the mobile unit 12 is wholly surrounded by the laser curtain such that the presence of an object such as a person can be detected anywhere around the mobile unit 12. It will be appreciated that there may be any suitable number of laser sensors for the particular application of the mobile autonomous agricultural system, such as one laser curtain sensor, or more than one laser curtain sensor. The mobile autonomous agricultural system 10 further comprises a safety module (not shown) which is configured to generate a safety output in response to determining that the laser curtain is interrupted. In this example, the safety output includes sending a signal to the controller to disable operation of the UV lighting panels 100 and 102. The safety output may also include sending a signal to control the mobile unit 12 to stop, and to control the robot arm 22 to stop. In some examples, the safety output signal may be to slow the mobile unit or to slow the robot arms. In other examples, the safety output may alternatively or additionally comprise producing an alarm, such as actuating an audible alarm on the mobile unit, or an alarm remote from the mobile unit to an operator, to alert the operator to the potential threat to safety of a person, or to alert the operator to the immobilising of the mobile unit or robot arms, such that they can restart the mobile unit or robot arms when it is determined to be safe again. Although the safety module and the controller have been described as separate components, it will be appreciated that they can be incorporated into a single unit. The laser curtain sensors 18 may be adjusted to determine the distance of the laser curtain from the mobile unit 12. In the example shown, the laser curtain is projected about 1.6 m away from the mobile unit 12, such that the safety output is triggered when a user walks within 1.6 m of the mobile unit 12. Further, although it has been described that the profile of the mobile unit defines an arch with distal ends of the arch fixed to wheels, in other examples, the mobile unit may have any suitable profile, or the arch profile may be inverted so that a portion of the arch at the apex is fixed to wheels and the distal ends extend upwards, away from the wheels and the ground. This can be used in situations where the crops are suspended from above, such that an inner zone between arms of the arch receives the suspended crop, and the crop is accessible to agricultural equipment in the arch from two sides simultaneously. For these examples, and the specific example described above, the axial direction may be the direction on the mobile unit which is configured to be parallel to a row while the controller controls the mobile unit to move along the row. Further details of compatible autonomous agricultural systems, mobile units and suitable safety curtains and control methods may be found in published United Kingdom Patent Application GB 2610184 A (A mobile autonomous agricultural system and method), which is hereby incorporated by reference in its entirety. It will be understood that the invention is not limited to the embodiments described above and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein. 16 04 24

Claims

1. A mobile autonomous agricultural system comprising:a powered mobile unit for carrying agricultural equipment, and configured to move along rows of crops;a UV lighting panel comprising:a UV light source configured to generate UV light; anda plurality of shade elements arranged relative to the UV light source to direct the UV light in a primary illumination direction and to restrict emission of UV light from the UV lighting panel outside the primary illumination direction; and a controller configured to control the travel of the mobile unit and operation of the UV lighting panel;wherein the plurality of shade elements are spaced apart from one another in a shading array and are arranged relative to the UV light source to permit passage of the UV light between said plurality of shade elements in the primary illumination direction, wherein the plurality of shade elements is a plurality of elongate fins arranged substantially parallel to one another in the shading array, and wherein each fin is made of an elastomeric polymeric material.

2. A mobile autonomous agricultural system according to claim 1, wherein the elastomeric polymeric material is rubber.

3. A mobile autonomous agricultural system according to claim 1 or claim 2, wherein each shade element is spaced apart from each adjacent shade element by 10 mm to 50 mm.

4. A mobile autonomous agricultural system according to any of claims 1 to 3, wherein each elongate fin has a width in the primary illumination direction from 20 mm to 50 mm and a thickness perpendicular to the primary illumination direction from 0.5 mm to 5 mm.

5. A mobile autonomous agricultural system according to any of claims 1 to 4, wherein the UV light source is elongate and each elongate fin extends longitudinally in a direction substantially orthogonal to a longitudinal axis of the elongate UV lightsource.

6. A mobile autonomous agricultural system according to any of claims 1 to 5, wherein the UV lighting panel comprises a plurality of said elongate LIV light sources arranged substantially parallel to one another and spaced apart from one another to form a lighting array.

7. A mobile autonomous agricultural system according to any of claims 1 to 6, wherein the UV lighting panel comprises a support and wherein the or each UV light source and the plurality of shade elements are mounted on the support.

8. A mobile autonomous agricultural system according to any of claims 1 to 7, wherein the plurality of shade elements are releasably mounted on the support.

9. A mobile autonomous agricultural system according to any of claims 1 to 8, wherein each shade element is releasably mounted on the support by way of one or more rods positioned in brackets on the support.

10. A mobile autonomous agricultural system according to any of claims 1 to 9, wherein the or each UV light source is a UV-C light source configured to generate UV-C light.

11. A mobile autonomous agricultural system according to any of claims 1 to 10, wherein at least a portion of the UV lighting panel has a semiarch profile in cross section.

12. A mobile autonomous agricultural system according to any of claims 1 to 11, wherein the mobile autonomous agricultural system further comprises:at least one laser curtain sensor configured to project a laser curtain away from the mobile unit; anda safety module configured to generate a safety output in response to determining that the laser curtain is interrupted within the laser curtain pattern, wherein the safety output comprises a signal to disable the UV light source.

13. A mobile autonomous agricultural system according to claim 12, wherein the mobile autonomous agricultural system comprises a plurality of laser curtainsensors distributed around the mobile unit configured together to form the laser curtain, and wherein each laser curtain sensor is configured to project a respective laser plane which overlaps with at least one other laser plane to form the laser curtain.

14. A mobile autonomous agricultural system according to any of claims 1 to 13, wherein the controller is configured to delay operation of the UV lighting panel until a predetermined period of time has passed after receiving a signal to operate the UV lighting panel.

15. A mobile autonomous agricultural system according to any of claims 1 to 14, wherein the mobile unit comprises an arch profile extending along an axial direction and the UV lighting panel is mounted within the arch profile.16.17.A mobile autonomous agricultural system according to claim 15, wherein the mobile autonomous agricultural system comprises two UV lighting panels mounted within the arch profile on opposing sides.A method of agriculture comprising illuminating a crop with UV light using a mobile autonomous agricultural system according to any of claims 1 to 16.

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