Relay device

Abstract

A system for directing a beam of light to a receiving device (106), including a transmitter unit (102) and a relay unit (104). The transmitter unit conveys light (101) from a light source to provide transmitted light, and the relay unit detects the 5 transmitted light from the transmitter unit provides a feed-back signal to the transmitter unit based on the detected light. The transmitter unit locates the relay unit based on said feed-back signal. The relay unit includes a relay deformable mirror (112, 114), which reflects the transmitted light from the transmitter unit with a first divergence angle during a first mode and a second narrower, divergence angle during a second 10 mode following the first mode. The relay deformable mirror changes from the first mode to the second mode, by changing a deformation thereof, based on information relating to the location of the receiving device.

Description

[0001] Relay Device

[0002] BACKGROUND OF THE INVENTION

[0003] With the continued proliferation of electronics devices, particularly those where it is not convenient or possible to provide a permanent wired connection, there is an important focus on how such devices are charged and communicate with other devices.

[0004] It is increasingly desirable for electronic devices to be able to transfer information wirelessly, without relying on WiFi for example, in order to transfer information quickly and securely. Furthermore, wireless charging of devices during usage is also desirable.

[0005] There have been a number of developments in charging technology in recent years, most notably the introduction of magnetic induction charging to avoid the need for a physical coupling between the charger and the device being charged. Whilst this technology may be well suited to personal portable devices such as smart phones, smart watches, tablets etc., the need for a close physical proximity between the device and the charging surface does not make this technology suitable in all circumstances. For example, when using a virtual reality gaming headset, the player may wish to move away from a gaming console, not limited by cable connections to the console and / or power sources, e.g. using the headset as a thin client.

[0006] There have been some proposals to use optical methods for wireless communication or charging. However the Applicant has recognised that in practical settings obstacles between devices also present limitations to such wireless communications and / or wireless charging.

[0007] The present invention seeks to address these problems. SUMMARY OF THE INVENTION

[0008] From a first aspect, the invention provides a system for directing a beam of light to a receiving device, comprising: a transmitter unit arranged to convey light from a light source to provide transmitted light; a relay unit comprising at least one relay deformable mirror ; wherein the relay unit is arranged to detect the transmitted light from the transmitter unit and to provide a feed-back signal to the transmitter unit based on the detected light; wherein the transmitter unit is arranged to locate the relay unit based on said feed-back signal from the relay unit; wherein the relay deformable mirror is arranged to reflect transmitted light from the transmitter unit with a first divergence angle during a first mode and a second narrower, divergence angle during a second mode following the first mode; and wherein the relay deformable mirror is arranged to change from the first mode to the second mode, by changing a deformation thereof, based on information relating to location of the receiving device.

[0009] Thus it will be seen that, in accordance with the first aspect of the invention, light may be transmitted from a transmitter unit to a receiving device via the deformable mirror(s) of the relay unit, where the divergence of the transmitted light can be changed.

[0010] Such an arrangement builds on the benefits provided by the Applicant’s previous proposals relating to transmitting a signal via a relay unit, such as that of EP4154385A1, where the relay unit is used to reduce line-of-sight problems caused by obstacles between a hub unit and a device to be charged. In accordance with the present invention however, the deformable mirror(s) of the relay unit enables it to change the divergence angle of the transmitted light. The deformable mirror may be deformed to change its curvature and thus change the divergence of the beam from the relay unit. This allows the relay unit to perform a ‘scan’ operation in which a broader beam is swept over a given area to ‘find’ the receiving device (and thus obtain information regarding its location) and then the beam can be narrowed to maximise the amount of transmitted light which reaches the receiving device once an accurate location has been determined allowing the beam to be accurately directed. As will be appreciated, several iterations of narrowing the beam and scanning a smaller area could be carried out once an approximate location is determined before the narrowest beam is used once the location has been determined accurately.

[0011] However other ways of determining the location of the receiving unit could be used instead. In these cases, the ability to change the width of the beam may nonetheless still be beneficial, for example in carrying out fine tuning of the beam direction.

[0012] The Applicant has appreciated that using a deformable mirror to change the divergence angle of the light emanating from the relay unit is a particularly powerefficient and compact solution which is suited to being employed in the relay unit which may advantageously be small and have low power requirements as it may not be practical to provide a permanently wired power connection to it.

[0013] This advantageously enables the light to be transmitted from the transmitter unit to the receiving device via the relay unit, even the receiving device is blocked from the line of sight of the transmitter unit.

[0014] The relay deformable mirror is arranged to be changed from the first mode to the second mode by changing a deformation thereof. The relay deformable mirror may deform by changing its curvature, thereby changing the focus / divergence of the transmitted light. For example, deforming the mirror to a particular curvature of the mirror will narrow the transmitted light by focusing the light as it is reflected, and can thus allow the beam to be focused onto the receiving device. Any deviation in the deformation of the mirror away from this particular curvature will increase the divergence of the beam.

[0015] The relay deformable mirror may include a piezoelectric material, whereby when the piezoelectric material is actuated, the curvature of the relay deformable mirror is changed. The deformation of the relay deformable mirror may thereby increase or decrease the width of the transmitted light, to move between the first and second modes. The deformation of the relay deformable mirror may be varied iteratively between the first and second modes, in response to the information relating to the location of the receiving device (such as the light received by its photovoltaic cell), in order to locate the receiving device. For example, the curvature of the relay deformable mirror may be progressively varied such that the angle of transmitted light moves is reduced as the area that is scanned is also reduced - e.g. until the width of the beam is at a minimum and any further movement of the light beam reduced the intensity received by the receiving device.

[0016] The receiving device may indicate to the relay unit that it has received at least a portion of the transmitted light via a feed-back signal sent back to the relay unit. For example, a retroreflector may partially reflect the signal back from the receiving device to the relay unit. Alternatively, or in addition, a different wireless communication method may be used between the receiving device and the relay unit, such as an optical, ultrasound, or radio frequency signal. This may indicate the intensity of light received by the receiving device, which may be correlated with the divergence angle of the transmitted light to correlate the location of the receiving device relative to the relay unit. In such a set of embodiments the relay unit comprises a receiver suitable for receiving the signal, for example an optical, ultrasound or radio frequency receiver. The receiver may comprise a single receiving element or equally an array of receiving elements.

[0017] In a set of embodiments, the relay unit comprises a second mirror upstream or downstream of the relay deformable mirror. By using two deformable mirrors, the relay unit may be able to receive and transmit light at a wider range of angles than if only one were used, and thus the relay unit may be able to direct the transmitted light towards the receiving device where the receiving device is at a wider range of positions.

[0018] In a set of such embodiments the relay unit comprises a first relay deformable mirror and a second relay deformable mirror; wherein the first relay deformable mirror is arranged to receive the transmitted light from the transmitter unit, and reflect the transmitted light to the second relay deformable mirror; and the second relay deformable mirror is arranged to reflect the transmitted light from the relay unit to the receiving device and / or another relay unit.

[0019] In a set of embodiments, the relay deformable mirror(s) is / are tiltable about at least two axes. The relay unit may be arranged to direct light towards a plurality of different receiving devices and / or further relay units by adjusting the tilt of the relay deformable mirror(s) to direct the light towards receiving devices located in different positions. This may allow for a signal to be transmitted to many receiving devices e.g. simultaneously with more than one relay deformable mirror, or in quick succession using a single relay deformable mirror operating in a time-division multiplexing manner.

[0020] The relay unit also detects the transmitted light from the transmitter unit, and feeds a signal back to the transmitter unit based on the detected light. The signal fed back to the transmitter unit may be used to adjust the direction of the transmitted light beam from the transmitter unit. This therefore allows the transmitter unit to ‘find’ the relay unit. When the relay unit does not detect the transmitted light, or only detects it partially, the transmitter unit may adjust the direction of the transmitted light - e.g. by an iterative scanning procedure - until the relay unit indicates that the light has been received. Such arrangements may be advantageous in simplifying set-up of the system, particularly where multiple relay units are provided or where relay units can be added or moved after initial set-up, as it does not require detailed information regarding the location of the relay unit(s) to be provided to the transmitter unit in advance. Similarly, the transmitter unit and / or receiving devices can also be added or moved after the initial set-up.

[0021] The signal fed back from the relay unit could comprise a signal indicative of the level of received light. For example the transmitter unit could compare the power of the light transmitted by the transmitter unit to the power of the light received at the relay unit taking account of the expected distance to the relay unit. Alternatively the transmitter unit could simply keep changing the direction of transmission, e.g. in a scanning motion, until the received intensity is maximised.

[0022] In a set of embodiments, the transmitter unit comprises at least one transmitter deformable mirror arranged to deflect light from the light source, wherein the transmitter deformable mirror is arranged to provide the transmitted light with a third divergence angle during a third mode and a fourth narrower, divergence angle during a fourth mode following the fourth mode, wherein the transmitter deformable mirror is arranged to change from the third mode to the fourth mode, by changing a deformation thereof, based on information relating to the location of the relay unit. As will be appreciated, this allows the transmitter unit to ‘find’ the relay unit a manner similar to that in which the relay unit ‘finds’ the receiving device.

[0023] The signal fed back to the transmitter unit may thus cause the transmitter unit to adjust the curvature of the transmitter deformable mirror in response to the light detected at the relay unit, to widen or narrow the beam. For example, the transmitter deformable mirror may include a piezoelectric material, whereby the piezoelectric material is actuated to change the curvature of the transmitter deformable mirror.

[0024] The third divergence angle is typically wider than the fourth divergence angle, such that the third divergence angle may be used to ‘find’ the relay unit, as the broader light beam is more likely to find the relay unit approximately when it is scanned. Once the relay unit is located, the divergence angle may be narrowed in order to allow for the relay unit to deflect the full intensity of the transmitted beam. As with the relay unit finding the receiving device, the transmitter unit could iterate the width of the beam and the area scanned.

[0025] The relay unit may indicate to the transmitter unit that it has received at least a portion of the transmitted light using an optical, ultrasound, or radio frequency signal. In such a set of embodiments the transmitter unit comprises a receiver suitable for receiving the signal, for example an optical, ultrasound or radio frequency receiver. The receiver may comprise a single receiving element or equally an array of receiving elements.

[0026] In a set of embodiments, the transmitter deformable mirror is tiltable about at least two axes. This facilitates the transmitted light being adjustably directed towards the relay unit.

[0027] It is not essential to use the intensity of the light received. For example another possibility would be to use a modulated beam and for the relay unit to feed back the modulation received. This could for example take the form of a coded communication signal with the transmitter interpreting a sufficiently low bit error rate as indicating that the relay unit had been adequately located.

[0028] The transmitter unit could use the light beam which is subsequently deflected by the relay unit for locating the relay unit as outlined above, or it could use a different ‘scoping’ beam. In either case the transmitter unit will typically need to know the spatial relationship between a detector used to detect the transmitted light and a part of the relay unit to which the transmitted light should be directed (e.g. the relay deformable mirror or an intermediate optical element).

[0029] In a set of embodiments, the relay unit is moveable relative to the transmitter unit. Moving the relay unit may further allow for the transmitted light to avoid obstacles which may arise in between the transmitter unit and relay unit, or may allow for the system to be used with a mobile relay unit. In accordance with the embodiments set out hereinabove, the transmitter unit can find the relay unit even when the relay unit has moved. For example, the relay unit(s) may be mounted on a drone or respective drones. Similarly, the transmitter unit and / or receiving unit may be mounted on respective drones.

[0030] In a set of embodiments, the system comprises a second relay unit arranged between the (first) relay unit and the receiving device. The second relay unit may be used to circumvent an obstacle which may arise between the first relay unit and the receiving device, by allowing re-routing of the transmitted light. The first relay unit could comprise a beamsplitter, in order to direct a portion of the transmitted light towards the second relay unit, and a portion to a receiving device. This may be useful where the transmitted light is to be directed to a plurality of receiving devices located in different places.

[0031] In a set of embodiments, the system comprises a plurality of relay units, wherein the relay units are arranged to have overlapping angular ranges to reflect the transmitted light, providing a plurality of routes for the light to travel from the transmitter unit to the receiving device. This may allow the system to circumvent obstacles by switching the direction of transmitted light between different relay units, and / or to transmit many signals at once. For example, such an arrangement could be used for a secure private network and / or to transmit a lot of data between the transmitter unit and a receiving device over a short period of time.

[0032] In a set of such embodiments, the system is arranged to change the route followed by the transmitted light when there is a determined impediment to one or more of the routes. For example, by detecting a change in intensity of transmitted light between the transmitter unit and relay unit(s), and / or between the relay unit(s) and receiving device, the presence of an obstacle may be determined and thus a signal may be sent to the transmitter unit to find and redirect the light to a different relay unit. This may allow for quick re-routing of the transmitted light to ensure the connection to the receiving device is not lost.

[0033] In a set of embodiments, the relay unit or at least one of the plurality of relay units comprises an array of mirrors, e.g. an array of deformable mirrors, wherein each mirror is arranged to reflect the transmitted light over a respective discrete angular range, the respective discrete angular ranges at least partially overlapping with each other. This may be beneficial in providing a plurality of possible directions to receive and reflect the transmitted light. This could be achieved by the incoming transmitted light being reflected at different angles, until the transmitted light emerges from the relay unit at the desired angle.

[0034] In a set of embodiments, the relay unit or at least one of the plurality of relay units comprises an arcuate array of mirrors, e.g. an arcuate array of deformable mirrors. This may allow the relay unit to reflect and receive the transmitted light in a wide range of possible directions, e.g. up to a full field of view (the extent of which may depend on the relay unit is located), such that the receiving device may be positioned anywhere in the line of sight of the relay unit(s) and receive the transmitted light. For example, the arcuate array of relay mirrors may include a plurality of mirrors, arranged to be inwardly facing in a circle or sphere. When the transmitted light beam enters the arcuate array from the transmitter unit (or another relay unit), the transmitted light may be reflected by a plurality of mirrors until the light beam emerges at the desired angle from the relay unit, to be directed towards the receiving device or another relay unit. For example, each relay deformable mirror in the arcuate array could be selectively tilted relative to the other mirrors within the relay unit in order for the transmitted light beam to emerge at any given angle. The relay unit(s) could be powered by a mains electrical connection or on-board battery. In a set of embodiments, the or each relay unit further comprises a photovoltaic cell arranged to charge the battery and / or to power the relay unit, the transmitter unit being arranged to direct the transmitted light to selectively illuminate the photovoltaic cell using the transmitted light or reflect the transmitted light to the receiving device. This may allow for the relay unit to be powered by the transmitter unit whilst also transmitting light to the receiving device. A battery in the relay unit could be charged during times when light does not need to be directed by the relay unit or the beam could be made to rapidly alternate between providing power to the relay unit and being deflected by it.

[0035] In another set of embodiments, the relay unit further comprises a photovoltaic cell and a beam-splitter, wherein the beam-splitter is arranged to split the transmitted light to provide a portion thereof to power or charge the unit via the photovoltaic cell, and to reflect the remainder of the transmitted light to the receiving device. Thus, the relay unit may be wirelessly powered by the transmitter unit, whilst providing a continuous signal to the receiving device.

[0036] In a set of embodiments, the relay unit comprises a sensor and the transmitter unit is arranged to alternately direct the transmitted light to the sensor in the relay unit, and towards the relay deformable mirror, such that the transmitted light is deflected towards to the receiving device, wherein the sensor is arranged to detect a disturbance of the transmitted light. This may allow for properties of the transmitted light beam to be measured by the sensor, whilst also transmitting light to the receiving device.

[0037] In another set of embodiments, the relay unit comprises a sensor and a beamsplitter, wherein the beam-splitter is arranged to split the transmitted light in order to provide a portion thereof for sensing, and to reflect the remainder of the transmitted light to the receiving device. This may allow for the transmitted light to be measured by the sensor, whilst providing a continuous signal to the receiving device. A sensor may be located at one or more relay units, however in some embodiments the sensor may be located at the receiving device. In a set of the embodiments outlined above, the sensor is arranged to detect properties of a medium through which the transmitted light has travelled, based on information regarding the light emitted from the light source and the light received at the sensor. For example, the sensor may be arranged to detect the intensity and / or wavelength of the light received at the relay unit. The sensor may send a signal indicative of these measurements to a processor, wherein the processor also receives signals indicative of the intensity and / or wavelength of the light transmitted from the transmitter unit, e.g. by a sensor located at the transmitter unit. Alternatively, this information may already be known to the processor, e.g. if the light source has a known wavelength and intensity. The processor may then compare the intensity and / or wavelengths of the transmitted light at the transmitter unit and the relay unit, in order to determine how the intensity and / or wavelengths have varied during transmission. This may be used to determine the properties of the medium, that the transmitted light has travelled through, e.g. by comparing to known spectra. For example, the transmitted light may be infrared, and thus the sensor may be used for infrared spectroscopy. In other examples, the sensor may detect the absorption spectra of the transmitted light, e.g. to detect the concentration of substances in the environment.

[0038] In a set of embodiments, the sensor is arranged to detect a variation in a time of flight of the transmitted light beam between the transmitter unit and the relay unit. For example, the transmitter unit may record the time a pulse of light is sent to the relay unit, and the relay unit may record the time the pulse of light is received. This can be used for measuring distances between the transmitter unit and relay unit, e.g. over a period of hours, days, and / or weeks. For example, a plurality of relay units can be used to monitor the relative movement of an arrangement of nodes in a structure, e.g. by arranging the relay units at the nodes. If the structure were to move, the time of flight between the plurality of relay units could change, and thus the movement of the structure can be monitored. This may be useful in areas prone to earthquakes, e.g. to monitor the damage to buildings, or to monitor the displacement of rockslides.

[0039] Detection of the variation in a time of flight may also be used to detection vibrations, which may cause the relay unit to shift relative to the transmitter unit and thus increase the distance for light to travel between the transmitter unit and the relay unit. In a set of embodiments, the transmitter unit comprises a light source. For example, the position of the light source, e.g. the angle of the light source, may be adjusted relative to the transmitter deformable mirror. This may allow for more accurate positioning of the transmitted light beam.

[0040] The light source may be selected depending on the use of the system, e.g. an infrared, or visible light system. For example, an infra-red beam may be suitable if the relay unit is also being used as a sensor or for wireless charging. In some embodiments, the light source comprises a laser. The laser may be used for modulation of light transmitted to the relay unit(s) and / or receiving device, e.g. to encode information within patterns of light pulses. This may be useful where the system is being used to transmit large amounts of information between the transmitter unit and receiving device, e.g. as a private network.

[0041] In a set of embodiments, the at least one relay deformable mirror is moveable between at least two different positions in or on the relay unit. This may allow the relay deformable mirror to be moved when the relay unit has been fixed in place, e.g. installed on a ceiling, such that the relay unit can vary the direction of detection of incident light and / or deflection of outgoing light by moving the relay deformable mirror.

[0042] The movement of the relay deformable mirror between different positions in or on the relay unit is in addition to the relay deformable mirror being deformable and / or tiltable, thus providing further control of direction of light travelling between the transmitter unit, relay unit(s) and receiving device. This can give a further degree of control of the direction of light deflected by the relay unit / direction of incident light that can be received, without requiring a large number of deformable mirrors.

[0043] Where the relay unit comprises two or more relay deformable mirrors, the relay deformable mirrors may be moveable or reconfigurable with respect to the relay unit, e.g. independently moveable relative to one another and the rest of relay unit.

[0044] In accordance with the embodiments set out above, incoming transmitted light may be reflected at different angles from the relay deformable mirrors, until the transmitted light emerges from the relay unit at the desired angle. This may allow the relay unit to reflect and receive the transmitted light in a wide range of possible directions, e.g. up to a 360° field of view, such that the receiving device may be positioned anywhere in the line of sight of the relay unit(s) and receive the transmitted light. The moveable relay deformable mirrors may thus be able to ‘scan’ over a wider range than a fixed relay deformable mirror, thus enabling the relay unit to search for a receiving device and / or other relay units over a larger area.

[0045] The relay deformable mirror(s) may be arranged to move linearly with respect to the relay unit, e.g. along a track or magnetically actuated by a variable magnetic field. However, in a set of embodiments, the relay unit comprises a mounting ring arranged to rotate about an axis, the mounting ring comprising the relay deformable mirror. For example, the relay deformable mirror may be mounted to the circumference of the mounting ring and be moved in a circle, in order to receive and deflect light in different directions. The mounting ring may be rotated using a number of mechanisms, e.g. a motor rotating an axle connected to the mounting ring on the axis, or a gearing system.

[0046] In a set of embodiments, a plurality of concentric mounting rings is provided arranged to rotate coaxially about the axis, wherein each mounting ring comprises a relay deformable mirror. For example, each mounting ring may comprise a relay deformable mirror mounted onto the inner circumference of the mounting ring, thus forming an array of inwardly facing relay deformable mirrors. Each mounting ring may be rotated such that when a transmitted light beam enters the relay unit from the transmitter unit (or another relay unit), the transmitted light is reflected by a plurality of mirrors until the light beam emerges at the desired angle from the relay unit, to be directed towards the receiving device or another relay unit.

[0047] This arrangement can provide a compact relay unit and a limited number of relay deformable mirrors(e.g. two), whilst allowing the transmitted light to be received and reflected at any desired angle.

[0048] For example, when the transmitter locates the relay unit, the relay unit may move a relay deformable mirror into a position where it can receive the transmitted light from the transmitter unit, e.g. by moving the respective mounting ring. Based on the location of the receiving device, the other relay deformable mirror(s) may then be moved in order to reflect transmitted light towards the receiving device and / or another relay device. The relay deformable mirror(s) may only be repositioned occasionally - e.g. during a set-up or system reconfiguration. However this is not essential; the mirror(s) could be moved during normal use, e.g. when the receiving device is moving with respect to the relay unit, without needing to move the relay unit itself.

[0049] The Applicant has recognised that instead of the relay unit employing a deformable mirror as set out above, one or more deformable lenses could be used instead for directing a beam of light to a receiving device, and therefore when viewed from a second aspect, the invention provides a system for directing a beam of light to a receiving device, comprising: a transmitter unit arranged to convey light from a light source to provide transmitted light; a relay unit comprising at least one relay deformable lens; wherein the relay unit is arranged to detect the transmitted light from the transmitter unit and to provide a feed-back signal to the transmitted unit based on the detected light; wherein the transmitter unit is arranged to locate the relay unit based on said feed-back signal from the relay unit; wherein the relay deformable lens is arranged to direct transmitted light from the transmitter unit with a first divergence angle during a first mode and a second narrower, divergence angle during a second mode following the first mode ; and wherein the relay deformable lens is arranged to change from the first mode to the second mode, by changing a deformation thereof, based on information relating to location of the receiving device.

[0050] It will be seen in accordance with the second aspect of the invention that by changing the curvature of the lens, the divergence angle of the transmitted light may be varied and thus the position of the receiving device may be determined. The deformable lens may deform and change curvature, and thus change the focus of the transmitted light to provide the first divergence angle. The deformable lens may then vary its deformation, thereby changing curvature and changing the focus of the transmitted light to provide the second divergence angle. The skilled person will appreciate that by using a deformable lens instead of a deformable mirror, the same advantages as those described above with respect to the deformable mirror may be realised.

[0051] The relay deformable lens is arranged to change from the first mode to the second mode, by changing a deformation thereof. The relay deformable lens may deform by changing its curvature, thereby changing the focus of the transmitted light. For example, deforming the lens to a particular curvature will narrow the divergence angle of the transmitted light, by focusing the light as it is transmitted through the lens, and thus can allow the beam to be focused onto the receiving device. Any deviation in the deformation of the lens away from this particular curvature will increase the divergence angle of the transmitted light.

[0052] The deformable lens can be constructed using a liquid lens comprising at least two immiscible fluids, where an applied voltage changes the shape of an interface between the fluids and thus changes the curvature of the lens, e.g. using the electrowetting principle. The deformable lens can also be constructed using a gel sandwiched between two transparent (e.g. glass) plates, where at least one plate is deformed by an actuator, e.g. a piezoelectric actuator.

[0053] In a set of embodiments, the relay deformable lens is translatable within the relay unit in at least two directions. This may allow for the relay unit to change the angle of the transmitted light towards the receiving device, e.g. to allow the receiving device to be located.

[0054] In a set of embodiments, the transmitter unit comprises at least one transmitter deformable lens arranged to deflect light from the light source; wherein the transmitter deformable lens is arranged to provide said transmitted light with a third divergence angle during a third mode and a fourth narrower, divergence angle during a fourth mode following the fourth mode; wherein the transmitter deformable lens is arranged to change from the third mode to the fourth mode, by changing a deformation thereof, based on information relating to the location of the relay unit. As when a transmitter deformable mirror is provided, an adjustable lens can be used to provide different divergence angles to facilitate finding the relay unit.

[0055] In a set of embodiments, the transmitter deformable lens is translatable within the transmitter unit in at least two directions. This may allow for the transmitter unit to change the angle of the transmitted light towards the relay unit, e.g. to allow the relay unit to be found by the transmitter unit.

[0056] It will be appreciated by the skilled person that the first and second aspects of the invention may be used in combination, e.g. where the relay unit comprises at least one relay deformable lens and / or at least one relay deformable mirror, and / or the transmitter unit comprises at least one transmitter deformable lens and / or at least one transmitter deformable mirror, order to allow further control over the transmitted light beam.

[0057] It will further be appreciated by the skilled person that the first and second aspects of the invention may both be used for at least wireless charging, optical communication, and / or projecting graphics.

[0058] Features of any aspect or embodiment described herein may, wherever appropriate, be applied to any other aspect or embodiment described herein. Where reference is made to different embodiments or sets of embodiments, it should be understood that these are not necessarily distinct but may overlap.

[0059] BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Certain preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0061] Figure 1 is a schematic diagram of the transmitter unit, relay unit, and receiving device arrangement according to a first aspect of the invention;

[0062] Figure 2 is a schematic diagram of the relay unit shown in Figure 1 ;

[0063] Figure 3a is a schematic diagram of a deformable mirror of a relay unit or transmitter unit as shown in any of Figures 1 , 2, and 4-10;

[0064] Figure 3b is a schematic diagram of the deformable mirror shown in Figure 3a;

[0065] Figure 3c is a schematic diagram of the reflection of light from the deformable mirror shown in Figures 3a and 3b with a convex deformation; Figure 3d is a schematic diagram of the reflection of light from the deformable mirror shown in Figures 3a and 3b with a planar deformation;

[0066] Figure 3e is a schematic diagram of the reflection of light from the deformable mirror shown in Figures 3a and 3b with a concave deformation;

[0067] Figure 4 is a schematic diagram of the alignment of the relay unit shown in Figure 2;

[0068] Figure 5a is a schematic diagram of the process of the transmitter unit locating the relay unit in accordance with the arrangement shown in Figures 1 , 2, and 4;

[0069] Figure 5b is a schematic diagram of the process of the relay unit locating another relay unit in accordance with the arrangement shown in Figures 2 and 4;

[0070] Figure 5c is a schematic diagram of a variant of the process of the relay unit locating another relay unit using a beam splitter in accordance with the arrangement shown in Figures 2, 4, and 5b;

[0071] Figure 6 is a schematic diagram of the relay unit shown in Figure 2 with an alternative beam path;

[0072] Figure 7 is a schematic diagram of a second relay unit;

[0073] Figure 8 is a schematic diagram of a third relay unit including a beam-splitter;

[0074] Figure 9 is a schematic of a fourth relay unit including a beam-splitter;

[0075] Figure 10 is a schematic diagram of a fifth relay unit including a retroreflector;

[0076] Figure 11a is a schematic diagram of a deformable mirror of a relay unit as shown in any of Figures 2-10;

[0077] Figure 11b is a schematic diagram of a deformable lens;

[0078] Figure 12 is a schematic diagram of a sixth relay unit including a mounting unit.

[0079] DETAILED DESCRIPTION

[0080] Figure 1 is a schematic diagram of a system for wirelessly communicating with a portable electronic device including a transmitter unit 102, relay unit 104 and receiving device 106 in accordance with a first embodiment of the invention. The transmitter unit 102 transmits a light beam 101 to the relay unit 104. The relay unit 104 directs the light beam 103 towards the receiving device 106. The relay unit 104 is movable relative to the transmitter unit 102 and the receiving device 106, as shown by the moved relay unit 104’. The transmitter unit 102 transmits a light beam 10T towards the moved relay unit 104’, and the moved relay unit 104’ directs the light beam 103’ via an alternative path towards the receiving device 106. Figure 2 is a schematic diagram of the relay unit 104 shown in Figure 1. The relay device 104 includes first and second relay deformable mirrors 112, 114, where the first relay deformable mirror 112 receives the light beam 101 from the transmitter unit and deflects this as an intermediate beam 105 to the second relay deformable mirror 114 which in turn directs the light beam 103 towards the receiving device 106.

[0081] The relay deformable mirrors 112, 114 are arranged on suitable platforms to allow them to tilt in two dimensions, to change the direction of the light beam 101, 103, 105 and also include a series of concentric sections of piezoelectric material that can be selectively actuated to deform the mirror 112, 114 by changing its curvature, to broaden and / or narrow the light beams 101 ,103. Such a mirror builds on the benefits provided by the Applicant’s previous proposals relating to a deformable mirror with a piezoelectric material, such as that of WO2023089333A1 . This is described in more detail with reference to Figures 3a-3e below.

[0082] The first and second relay deformable mirrors 112, 114 are arranged on either side of an aperture 122 of a ring-shaped photodetector 120. When the first and second relay deformable mirrors 112, 114, are aligned, and the light beam 105 from the first mirror 112 is sufficiently is narrow, the light beam 105 passes through the aperture 122 without interacting with the photodetector 120. However, if the light beam 105 is broader, or if the first relay deformable mirror 112 is tilted away from the second relay deformable mirror 114, part or all of the light beam 105 will not pass through the aperture 122, landing instead on the photodetector 120 which will thus generate a signal.

[0083] A signal generated by the photodetector 120 indicates that the tilt of the first relay deformable mirror 112 should be changed, as it is not aligned with the aperture 122. Furthermore, the signal generated by the photodetector 120 indicates that the light beam 101 has been received by the relay unit 104 from the transmitter unit 102. This information, including the intensity of light received by the photodetector 120 is transmitted back to the transmitter unit 102 as an RF signal by the antenna 116.

[0084] When the first and second relay deformable mirrors 112, 114 are aligned with each other, the light beam 105 passes through the aperture 122 and is deflected by the second relay deformable mirror 114 to direct the light beam 103 towards the receiving device.

[0085] In order to ‘find’ the receiving device, the second deformable mirror 114 is deformed such that a broad light beam 103 is directed towards the receiving device. The relay unit then performs a ‘scan’ operation, by sweeping the broad beam 103 over a given area. As the broad beam 103 is swept, a large area can be covered in order to locate the receiving device.

[0086] A second antenna 118 is provided to receive signals from the receiving device 106, indicating that it has detected the light beam 103 directed towards it. The second relay deformable mirror 118 then tilts to direct the light beam 103 towards the receiving device, and deforms to narrow the light beam 103, such that a high intensity light beam is directed at the receiving device. If no signal is received by the receiving device, then the second relay deformable mirror 114 continues the ‘scan’ operation, e.g. by deforming such that the light beam 103 is broader and thus can scan over a larger area.

[0087] Figure 3a shows a plan view of a deformable mirror 162, which can be used as a relay deformable mirror 112, 114 and / or a transmitter deformable mirror 135. The deformable mirror 162 includes a single actuator arm 164 connected by a connecting beam 166 to a central deformable moveable mirror element 168. The actuator arm 164, deformable moveable mirror element 168 and connecting beam 166 are made primarily from silicon. The actuator arm 164 has four approximately equal-sized independently addressable segments 170, 172, 174, 176 where an additional layer of piezoelectric material - e.g. lead zirconate titanate (PZT) is provided. Each piezoelectric segment is connected to a respective control output of a corresponding control system (not shown).

[0088] The deformable moveable mirror element 168 is ‘hanging’ on the actuator arm 164 which takes the form of a C-shaped piezoelectric membrane torsion beam. This torsion beam has the function of both providing lift and torsion upon actuation of pairs of the four segments 170, 172, 174, 176 so that by simply actuating two neighbouring segments, deflection in all four tilting directions is possible. Using only a single cantilever (actuator arm) with four independently actuable segments provides a micro- mirror which can tilt and rotate significantly without any weak spots. The thin, membrane-form actuator arm enables significant torsion and allows the micro-mirror to tilt and rotate despite being wide and relatively stiff - this is because, over the length of the actuator arm, it can accumulate enough torsion. Looked at another way torsion resulting from the deformation of the piezoelectric membrane formed by the arm is ‘spread along’ the actuator arm 166 away from the anchored part of the arm, resulting in a large deflection without compromising the robustness of the device.

[0089] The deformable moveable mirror element 168 is shown in more detail in Figure 3b. The deformable moveable mirror element 168 has an overall diameter of approximately 3 mm. The deformable moveable mirror element 168 has two independently actuable sections. The first section 178 is a central circular section and the second section 180 has the shape of an annulus arranged concentrically around the central circular section 178. The first section has a diameter of approximately 2 mm. Although only two sections are shown, there may be more concentrically arranged sections (e.g. further annuli) surrounding the central section.

[0090] A voltage can be applied independently to each section 178, 180 of the deformable moveable mirror element 168 using a control system (not shown). The deformable moveable mirror element 168 provides focussing and de-focussing capability. The actuable sections 178, 180 can therefore vary the curvature of the deformable moveable mirror element 168. When a light beam is incident on the deformable moveable mirror element 168, it can be reflected in a desired direction determined by the position and orientation of the deformable moveable mirror element 168 which is determined by which of the actuator segments are actuated. The width of the reflected beam can be varied by the curvature of the deformable moveable mirror element 168, which is determined by which of the sections are actuated and to which degree.

[0091] Figures 3c, 3d, and 3e show how the changing curvature of the deformable moveable mirror element 168 changes the way light is deflected, so that the deformable moveable mirror element 168 can act as a focussing or defocussing mirror, depending on how it is deformed. As illustrated in Figure 3b, the first section 178 and second section 180 are actuated with a different voltage to cause at least part of the surface of the deformable moveable mirror element 168 to be displaced in the z direction. Applying a voltage to just the central section 178 of the deformable moveable mirror element 168 results in a concave deformation of the deformable moveable mirror element 168. Applying a voltage to just the outer ring section 180 of the deformable moveable mirror element 168 results in the opposite convex deformation. Having the deformable moveable mirror element 168, segmented in this way, allows deformation of the deformable moveable mirror element 168 in both directions, upwards and downwards (e.g. in a convex or concave manner.

[0092] A schematic version of the deformable moveable mirror element 168’ deformed to have a convex curvature is shown in Figure 3c. The convex optically reflective surface causes the divergence angle of the reflected light 182’ to be greater than the divergence angle of the incident light and thus the incoming light is de-focussed. A schematic version the deformable moveable mirror element 168” deformed to have a planar curvature is shown in Figure 3d. The planar optically reflective surface causes the divergence angle of the reflected light 182” to be the same as the divergence angle of the incident light and so the surface provides specular reflection. A schematic version of the deformable moveable mirror element 168’” deformed to have a concave curvature is shown in Figure 3e. The concave optically reflective surface causes the divergence angle of the reflected light 182’” to be less than the divergence angle of the incident light and to the incoming light is focussed.

[0093] Figure 4 is a schematic diagram of the alignment procedure of the deformable mirrors within the relay unit 104. The first relay deformable mirror 112 receives a light beam 101 , and directs it towards the second relay deformable mirror 114 through the aperture 122, by tilting accordingly. For example, if a light beam 10T initially approaches the first relay deformable mirror 112 at a different angle, light is detected at the photodetector 120 and so the first relay deformable mirror 112 is tilted until the photodetector 120 no longer detects light because light is directed through the aperture 122 towards the second relay deformable mirror 114.

[0094] The first relay deformable mirror 112 is also shown as being deformed into a convex shape in order to produce a broad light beam 109 emanating from the mirror to ensure that the beam hits the photodetector 120, the direction of the incoming light beam 101, 10T may be determined, e.g. if the photodetector 120 is a four-quadrant detector. A signal from the photodetector 120 indicating the direction of the incoming light beam may be used to determine how to adjust the tilt and / or deformation of the first relay deformable mirror 112, such that the light beam passes through the aperture 122. Ensuring the light beam passes through the aperture 122 may preserve its beam quality, and can allow for the direction of the exiting light beam 103 to be controlled independently of the incoming light beam 101 , 10T. This allows for the “receiving” and “transmitting” parts of the relay device 104, e.g. the first relay deformable mirror 112 and the second relay deformable mirror 114 respectively, to act independently.

[0095] Figure 5a is a schematic diagram of the transmitter unit 102. This comprises a light source 133 e.g. a laser, a transmitter deformable mirror 135 and transmitter antenna 134.

[0096] Figure 5a also shows how the transmitter unit 102 can ‘find’ the relay unit 104. The transmitter unit 102 initially transmits a broad light beam 113 by deforming the mirror to a shallow concave shape. The light beam 113 is scanned across a predetermined area by tilting the transmitter mirror 135 until it is incident on the relay unit and in particular the first relay deformable mirror 112 thereof. The first relay deformable mirror 112 directs the light beam 113 onto the photodetector 120. The photodetector 120 detects the intensity of the light beam 113 and transmits this information to the transmitter unit 102 via the relay antenna 136 to be received by the transmitter antenna 134. In response to the detected intensity, the transmitter deformable mirror 135 is made to deform into a more concave shape to narrow the light beam 113 and then the mirror 135 is tilted again to scan the narrower beam until a signal is again transmitted from the relay unit 104. This process repeats until the transmitter deformable mirror 135 and first relay deformable mirror 112 are aligned, and the light beam 113 is sufficiently narrow to deliver an acceptable power density. The aperture of the photodetector is just slightly larger than the narrowest beam diameter. The irradiance diminishes rapidly from the centre (Gaussian beam), but there is still a small fraction that can be detected by the ring-shaped detector. With multiple sectors on the detector, the beam position can be estimated. Also during initial alignment, the mirror 112 can be used to spread the beam as in the previous figure, so even if the incident beam is narrow, it can be made to diverge and be detected.

[0097] Once the first relay deformable mirror 112 has received the narrow light beam from the transmitter unit 102, the first relay deformable mirror 112 directs the narrow light beam towards the second relay deformable mirror 114, as described above with reference to Figure 2. Figure 5b shows how a first relay unit 104a can ‘find’ a second relay unit 104b. The first and second relay units 104a, 104b may be any of the relay units described with respect to Figures 1-4, and 5a. The first relay unit 104a and second relay unit 104b each include a first and second relay deformable mirror. The first relay unit 104a initially transmits a broad light beam 125 by deforming the second relay deformable mirror 114a to a shallow concave shape. The light beam 125 is scanned across a predetermined area by tilting the second relay deformable mirror 114a until it is incident on the second relay unit 104b and in particular the first relay deformable mirror 112b thereof. The first relay deformable mirror 112b directs the light beam 125 onto the photodetector 120b. The photodetector 120b detects the intensity of the light beam 125 and transmits this information to the first relay unit 104b via the second relay antenna 136b, to be received by the first relay antenna 136a. In response to the detected intensity, the second relay deformable mirror 114a of the first relay unit 104a is made to deform into a more concave shape to narrow the light beam 125 and then the mirror 114a is tilted again to scan the narrower beam until a signal is again transmitted from the second relay unit 104b. This process repeats until the second relay deformable mirror 114a of the first relay unit 104a and the first relay deformable mirror 112b of the second relay unit 104b are aligned, and the light beam 125 is sufficiently narrow to deliver an acceptable power density.

[0098] Once the first relay deformable mirror 112b has received the narrow light beam from the first relay unit 104a, the first relay deformable mirror 112b directs the narrow light beam towards the second relay deformable mirror 114b of the second relay unit 104b, as described above with reference to Figure 2. This process may be repeated between a plurality of relay units, in order to align a “chain” of relay units.

[0099] Figure 5c is a schematic diagram of a relay unit 184, including first and second relay deformable mirrors 112b’, 114b’, and a beam splitter 186 arranged between the first and second relay deformable mirrors 112b’, 114b’. The relay unit 184 may be aligned with a transmitter unit and / or another relay unit similarly to the method described with reference to Figures 5a and 5b, however instead of a photodetector, a beam splitter 186 is used to detect the intensity of the light beam 127 directed towards the relay unit 184. The beam splitter 186 splits the incident light beam 127 into two components: one component directed towards the second relay deformable mirror 112b’, and the other component is directed towards a light detector component 188. The beam splitter 186 could be removed when alignment is completed, e.g. to maximize transmitted power.

[0100] Figure 6 shows the relay unit 104 shown in Figure 2, deflecting two edges of a collimated beam 105a, 105b. The beam is focused onto the aperture 122 by the first relay deformable mirror 112 and re-collimated by the second relay deformable mirror 114. The curvature of the first and second relay deformable mirrors 112, 114 may be slightly re-adjusted after the transmitter unit and relay unit(s) are aligned as described with reference to Figures 5a-5c, in order to correct any deviations in the beam introduced after alignment.

[0101] The respective deformable mirrors of the transmitter unit 102 and relay unit 104 are able to adjust their tilt and curvature in order to re-direct the light beam 101 to the receiving device 106, across a wide range of relative arrangements of the transmitter unit 102, the relay device 104, and the receiving device 106. Using a relay unit 104 to direct the light beam 101 is useful when there is an obstacle present between the transmitter unit 102 and the receiving device 106 preventing it from transmitting to the receiving device 106 directly, as the light beam 101 may be directed around the obstacle to reach the receiving device 106.

[0102] There could be more than one relay device 104 provided, such that the light beam may be directed along a plurality of paths in order to travel between the transmitter unit 102 and the receiving device 106. This may allow for light beam to be directed around a variety of obstacles, or for more than one light beam to be directed between the transmitter unit 102 and the receiving device 106.

[0103] Referring back to Figure 1, it can be seen that if the relay unit 104’ is moved to a different place, the system can still function as the transmitter unit 102 can simply repeat the finding process outlined above until an incident beam 10T in a new direction is directed at the relay unit 104’.

[0104] Figure 7 is a schematic diagram of a second embodiment of the relay unit 117, including four relay deformable mirrors 124a, 124b, 126a, 126b. By using multiple mirrors within a single relay unit, the relay unit is able to receive and transmit light from and to a wide range of directions, where each mirror addresses part of the total angular range of the second relay unit 117. This allow a greater flexibility in system design and / or fewer relay units to be used.

[0105] The third and fourth relay deformable mirrors 124a, 124b receive the light beam 107, e.g. from the transmitter unit or another relay unit, and transmit the beam to an intermediate mirror 128. The intermediate mirror 128 is arranged behind an aperture 132 in a photodetector 130. The intermediate mirror reflects the beam onto one of the fifth and sixth relay deformable mirrors 126a, 126b, reflect the light beam in two different directions 107a, 107b, depending on their respective tilt and curvature. This can be used in an arrangement where the light beam 107 is to be directed towards to different relay units (not shown), or two different receiving devices without needing either mirror to be able to move quickly or through a large angle.

[0106] Figure 8 shows a schematic diagram of a third embodiment of a relay unit 119 in communication with the transmitter unit 102, where the relay unit 119 includes a beam splitter 138. This relay unit 119 may be used instead of the relay units described with reference to Figures 1-6. The beam splitter 138 splits the incident light beam 111 into two components: one component directed towards the first relay deformable mirror 112’, and the other component is directed towards a light detector component 140.

[0107] The component 140 could be a specialised light sensor, e.g. one arranged to detect intensity, phase and / or wavelength of the light beam 111. The sensor 140 transmits data relating to these measurements wirelessly to the transmitter unit or another remote unit , in order to allow them to determine spectral attenuation, beam quality / disturbance, or a time delay. For example, the sensor may be used for spectroscopy, e.g. infrared spectroscopy, by measuring the absorption of the transmitted light between the transmitter unit 102 and the relay unit 119, in order to determine the composition of gases between the transmitter unit and relay unit.

[0108] In another embodiment the component could be a photovoltaic cell arranged to power / charge the relay unit 104. This allows for the relay unit to be wireless. The beam splitter 138 could be wavelength dependent such that different wavelength channels of the light beam 111 have different uses, e.g. a particular wavelength is used for communication between the transmitter unit and the receiving device, whereas a different wavelength is used for charging and / or sensing.

[0109] Figure 9 is a schematic diagram of a fourth embodiment of a relay unit 121 in communication with the transmitter unit 102, where the relay unit 121 includes a single relay deformable mirror 142. The relay deformable mirror 142 directly deflects the light beam 113 towards another relay unit or receiving device. In this case, the photodetector 144 is on the outside of the relay unit 121 but this operates in the same way described previously whereby a signal therefore is communicated back to the transmitter unit to direct its scanning and narrowing of the beam 113. Like the previous embodiment this embodiment also includes a beam-splitter 150 and light sensor or PV cell 148.

[0110] Figure 10 is a schematic diagram of a fifth embodiment of a relay unit 123 in communication with the transmitter unit 102, where the relay unit 123 includes a retroreflector 152 around the entrance aperture thereof. The retroreflector 152 is used to give instant optical feedback to the transmitter unit 102 to indicate that the light beam 115 is in the correct position, i.e. is incident on the first relay deformable mirror 112”. This reduces the number of iterations required to align the transmitted light beam 115 with the relay unit 123. The retroreflector 152 could be a fixed around the entrance aperture. Additionally or alternatively a switchable retroreflector 153 could be periodically inserted into the path of the beam.

[0111] Figure 11a shows generically how a deformable mirror 154, can be used to focus a collimated beam 155 to a focused beam 157 in accordance with the embodiments described with reference to any of Figures 2-10.

[0112] Figure 11b however shows how a similar effect can be obtained using a deformable lens 156. It should be understood therefore that in accordance with the invention deformable lens can be used in place of any or all of the deformable mirrors shown in any of the embodiments described above with reference to Figures 2-10. The deformable lens 156 is able to deform such that it changes its curvature, such that the incident light beam 159 passed through the deformable lens 156 and is distorted, e.g. narrowed or broadened. Whereas the deformable mirror 154 shown in Figure 11a is tilted in order to direct the light beam as required, the deformable lens 156 can be translated to give the required direction.

[0113] Figure 12 is a schematic diagram of a sixth embodiment of part of a relay unit 163, including a first relay deformable mirror 170 mounted onto the inner circumference of a first mounting ring 162, and a second relay deformable mirror 172 mounted onto the inner circumference of a second mounting ring 164. The second mounting ring 164 has a smaller diameter than the first mounting ring 162 and is mounted such that the second mounting ring 164 is concentric to the first mounting ring 162.

[0114] The centre points of the first and second mounting rings 162, 164 are each able to rotate around a common static shaft 176. This rotation allows the first and second relay deformable mirrors 170, 172 to move independently in a circle.

[0115] The first mounting ring 162 is connected to a first motor 166, and the second mounting ring 164 is connected to a second motor 168. The first motor 166 and the second motor 168 respectively rotate the first and second mounting rings 162, 164 about the shaft 176. The first and second motors 166, 168 thus allow for the first and second relay deformable mirrors 170, 172 to be repositioned relative to one another and to the rest of the relay unit such as the housing etc. (not shown), e.g. controlled by a processor (not shown) and suitable drive electronics connected to the first and second motors 166, 168.

[0116] In use, a light beam 174 entering the relay unit 163 is reflected by the first relay deformable mirror 170 towards the second deformable mirror 172, and the second relay deformable mirror 172 reflects the light beam 174a away from the relay unit 163. Thus, by changing the relative positions of the first and second relay deformable mirrors 170, 172, by using the first and second motors 166, 168 to rotate the first and second mounting rings 162, 164 respectively, the relay unit 163 can both receive and deflect incident light in any direction. As each mounting ring 162, 164 is connected to a different motor 166, 168, the mounting rings can be independently rotated relative to one another.

[0117] In addition, the curvature and tilt of the first and second relay deformable mirrors can be varied as described above in relation to previous embodiments, to provide further control over the light that can be received and deflected by the relay unit 163.

[0118] Additional mounting rings and respective relay deformable mirrors may also be added to the relay unit 163, concentric to the first and second mounting rings 162, 164. This may allow further control of the direction of light deflection from the relay unit 163.

[0119] Whilst Figure 12 shows the incident light 174 hitting the first relay deformable mirror 170, and then the second relay deformable mirror 172, it will be appreciated that the incident light may first be directed toward the second relay deformable mirror 172 (e.g. to the innermost mounting ring), and then the first relay deformable mirror 170 (e.g. the outermost mounting ring).

[0120] The relay unit 163 may be used to configure the light path between a transmission unit and a receiving device once the relay unit has already been installed in a room, e.g. where the relay unit 163 is installed on the ceiling of a room, and / or where the receiving device moves around. It will be appreciated by the skilled person that whilst motors are described herein to move the first and second relay deformable mirrors relative to one another, other mechanisms may be used, such as gears or magnetic actuation.

Claims

CLAIMS1 . A system for directing a beam of light to a receiving device, comprising: a transmitter unit arranged to convey light from a light source to provide transmitted light; a relay unit comprising at least one relay deformable mirror ; wherein the relay unit is arranged to detect the transmitted light from the transmitter unit and to provide a feed-back signal to the transmitter unit based on the detected light; wherein the transmitter unit is arranged to locate the relay unit based on said feed-back signal from the relay unit; wherein the relay deformable mirror is arranged to reflect the transmitted light from the transmitter unit with a first divergence angle during a first mode and a second narrower, divergence angle during a second mode following the first mode ; and wherein the relay deformable mirror is arranged to change from the first mode to the second mode, by changing a deformation thereof, based on information relating to the location of the receiving device.

2. The system of claim 1 , the at least one relay deformable mirror comprises a first relay deformable mirror and a second relay deformable mirror; wherein the first relay deformable mirror is arranged to receive the transmitted light from the transmitter unit, and reflect the transmitted light to the second relay deformable mirror; wherein the second relay deformable mirror is arranged to reflect the transmitted light from the relay unit.

3. The system of claim 1 or 2, wherein the at least one relay deformable mirror is tiltable about at least two axes.

4. The system of claim 1 , wherein the transmitter unit comprises at least one transmitter deformable mirror arranged to deflect light from the light source; wherein the transmitter deformable mirror is arranged to provide said transmitted light with a third divergence angle during a third mode and a fourth narrower, divergence angle during a fourth mode following the fourth mode;wherein the transmitter deformable mirror is arranged to change from the third mode to the fourth mode, by changing a deformation thereof, based on information relating to the location of the relay unit.

5. The system of claim 4, wherein the at least one transmitter deformable mirror is tiltable about at least two axes.

6. The system of any preceding claim, wherein the transmitter unit is moveable relative to the relay unit.

7. The system of any preceding claim, wherein the relay unit is moveable relative to the transmitter unit.

8. The system of any preceding claim, wherein the transmitter unit comprises a light source.

9. The system of any preceding claim, wherein the relay unit comprises an array of relay deformable mirrors, wherein each relay deformable mirror reflects the transmitted light over a respective discrete angular range, wherein the respective discrete angular ranges of the relay deformable mirrors at least partially overlap with each other.

10. The system as claimed in claim 9, comprising an arcuate array of relay deformable mirrors.

11. The system as claimed in any preceding claim, comprising a second relay unit, wherein the second relay unit is arranged between the relay unit and the receiving device.

12. The system as claimed in any preceding claim, comprising a plurality of relay units, wherein the relay units are arranged to have overlapping angular ranges to reflect the transmitted light, providing a plurality of routes for the light to travel from the transmitter device to the receiving device.

13. The system as claimed in claim 12, wherein the plurality of relay units are arranged to change the route followed by the transmitted light when there is a determined impediment to one or more of the routes.

14. The system as claimed in any preceding claim, wherein the relay unit further comprises a photovoltaic cell and the transmitter unit is arranged to direct the transmitted light to alternately charge the photovoltaic cell using the transmitted light, and to reflect the transmitted light to the receiving device.

15. The system as claimed in any preceding claim, wherein the relay unit further comprises photovoltaic cell and a beamsplitter, wherein the beamsplitter is arranged to split the transmitted light to simultaneously charge the photovoltaic cell using the transmitted light beam, and to reflect the transmitted light to the receiving device.

16. The system as claimed in any preceding claim, wherein the relay unit comprises a sensor, and the transmitter unit is arranged to alternately direct the transmitted light to the sensor, and to reflect the transmitted light to the receiving device, wherein the sensor is arranged to detect a disturbance of the transmitted light.

17. The system as claimed in any preceding claim, wherein the relay unit comprises a sensor and a beamsplitter, wherein the beamsplitter is arranged to split the transmitted light in order to simultaneously direct the transmitted light to the sensor and to reflect the transmitted light to the receiving device.

18. The system as claimed in any of claims 16, or 17, wherein the sensor is arranged to detect a variation in a time of flight of the transmitted light beam between the transmitter unit and the relay unit.

19. The system as claimed in any of claims 16-18, wherein the sensor is arranged to detect properties of a medium through which the transmitted light has travelled based on information regarding the light emitted from the light source and the light received at the sensor.

20. The system as claimed in any preceding claim, wherein the light source comprises a laser.

21. The system as claimed in any preceding claim, wherein the at least one relay deformable mirror is moveable between at least two different positions in or on the relay unit.

22. The system as claimed in claim 21 , wherein the relay unit comprises a mounting ring arranged to rotate about an axis, the relay deformable mirror being mounted to the mounting ring.

23. The system as claimed in claim 22, comprising a plurality of concentric mounting rings arranged to rotate coaxially about the axis, wherein each mounting ring comprises a respective relay deformable mirror mounted thereto.

24. The system for directing a beam of light to a receiving device, comprising: a transmitter unit arranged to convey light from a light source to provide transmitted light; a relay unit comprising at least one relay deformable lens; wherein the relay unit is arranged to detect the transmitted light from the transmitter unit and to provide a feed-back signal to the transmitted unit based on the detected light; wherein the transmitter unit is arranged to locate the relay unit based on said feed-back signal from the relay unit; wherein the relay deformable lens is arranged to direct transmitted light from the transmitter unit with a first divergence angle during a first mode and a second narrower, divergence angle during a second mode following the first mode ; and wherein the relay deformable lens is arranged to change from the first mode to the second mode, by changing a deformation thereof, based on information relating to location of the receiving device.

25. The system as claimed in claim 24, wherein the relay deformable lens is translatable within the relay unit in at least two directions.

26. The system as claimed in claim 24 or 25, wherein the transmitter unit comprises at least one transmitter deformable lens arranged to deflect light from the light source;wherein the transmitter deformable lens is arranged to provide said transmitted light with a third divergence angle during a third mode and a fourth narrower, divergence angle during a fourth mode following the fourth mode; wherein the transmitter deformable lens is arranged to change from the third mode to the fourth mode, by changing a deformation thereof, based on information relating to the location of the relay unit.

27. The system as claimed in claim 26, wherein the transmitter deformable lens is translatable within the transmitter unit in at least two directions.

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