WO2024149463A1

WO2024149463A1 - Luminous sign

Info

Publication number: WO2024149463A1
Application number: PCT/EP2023/050621
Authority: WO
Original assignee: Verisure Sàrl
Priority date: 2023-01-12
Filing date: 2023-01-12
Publication date: 2024-07-18

Abstract

Provided is a luminous sign (100) comprising first (102) and second (104) optical waveguide layers each comprising a pair of major surfaces (106, 106`108, 108`) and at least one peripheral edge surface (107, 109) between the pair of major surfaces (106, 106`, 108, 108`), the major surfaces of one of the two optical waveguide layers (102, 104) being superimposed over the major surfaces of the other of the two optical waveguide layers (102, 104); each of the first and second waveguide layer (102, 104) being provided with a photoluminescent structure (110, 112) including photoluminescent material, the photoluminescent material being configured to emit visible emission light on being excited by excitation light; each photoluminescent structure (110, 112) defining an image; a light source arrangement (114) configured to launch excitation light into each of the first and second waveguide layers (102, 104); and a processor configured to activate the light source arrangement (114) to launch excitation light into the first or the second waveguide layers (102, 104) to cause the respective photoluminescent structure (110, 112) to display the respective image as a pattern of emission light.

Description

Luminous sign

Technical field

The present invention relates to luminous signs, and in particular such signs for use in conjunction with a premises security monitoring installation.

Background

House breaking, breaking and entering, burglary, theft from premises and criminal damage to premises such as homes and businesses are problems that have troubled human society for centuries, and possibly for millennia Perhaps surprisingly, burglar alarms have been around in some guise since the 18^th century, with the first electric burglar alarm was apparently patented in 1853 by the Reverend Augustus Russell Pope and rang a bell if a door or window was opened. Perhaps more surprisingly, the Pope invention was quickly commercialised AND USED as the basis for a monitored alarm service in which signals from alarm installations were carried over telephone lines to staff working in a remote monitoring station.

While burglar alarms (hereinafter security monitoring systems) potentially provide a means to catch villains committing burglary, it has long been recognised that potential acts of burglary and the like may be prevented - or at least driven elsewhere, by providing warning signs and other indications - such as conspicuously located sirens, cameras or other security items, so that any potential burglar or housebreaker is made aware of the fact that a particular property is protected by a security monitoring system. This fact has been confirmed through interviews with convicted burglars and housebreakers - who confirm that they will generally look elsewhere rather than attempting to break into a property that they know to have a professionally installed alarm system. A recent survey also confirmed that purchasers and potential purchasers of security monitoring systems consider the presence of clearly visible signage an important part of a security monitoring system installation because it is believed to dissuade burglars and housebreakers from attempting a felonious entry.

For such signage to work it is clearly necessary for the signage to have sufficient visual impact to attract the attention of any villain “casing the joint” prior to deciding to affect an unlawful entry. There is scope to improve the visual impact of signage generally, and in particular that dedicated to warning off potential burglars.

The present invention provides various embodiments of signage particularly intended for use in conjunction with security monitoring system installations, although various of the embodiments also potentially have wider application.

Summary

According to a first aspect there is provided a luminous sign comprising first and second optical waveguide layers each comprising a pair of major surfaces and at least one peripheral edge surface between the pair of major surfaces, the major surfaces of one of the two optical waveguide layers being superimposed over the major surfaces of the other of the two optical waveguide layers; each of the first and second waveguide layer being provided with a photoluminescent structure including photoluminescent material, the photoluminescent material being configured to emit visible emission light on being excited by excitation light; each photoluminescent structure defining an image; a light source arrangement configured to launch excitation light into each of the first and second waveguide layers; and a processor configured to activate the light source arrangement to launch excitation light into the first or the second waveguide layers to cause the respective photoluminescent structure to display the respective image as a pattern of emission light.

Such a sign may provide visually striking images that are attention grabbing (even when only seen using peripheral vision) by virtue of a perceived “movement” between the images provided by the two photoluminescent structures. It is not necessary for the two images to be arranged to provide a two-frame animation - switching between the two images may provides a motion-like simulation effect even when the two images are simply verbal rather than pictorial.

Optionally the light source arrangement includes a first set of light sources dedicated to the illumination of the first waveguide, and a second set of light sources dedicated to the illumination of the second waveguide. Such a light sources arrangement may also include one or more light sources configured to emit light onto an edge face of the respective waveguide. Such arrangements permit the simultaneous illumination of both images.

Alternatively, the light source arrangement may include one or more light sources that are used both to illuminate the first waveguide and to illuminate the second waveguide. Such a light source arrangement may include an optical switch that is controlled by the processor to switch light to the first waveguide or to the second waveguide. Such an arrangement may permit some cost reduction by reducing component count, but may not permit the simultaneous illumination of both images.

In any variant of the first aspect, the light source arrangement may include for each optical waveguide a light diffusing optical fibre to supply light to the waveguide from one or more of the respective light sources. Such an arrangement may permit good coupling of light from the light source arrangement into the waveguides, thereby providing a uniform spread of light across the photoluminescent structures for more even image illumination. Preferably, the first and second optical waveguide layers are separated by a gas-filled gap. Optionally, the gap is filled with a moisture-free gas at a pressure below atmospheric pressure (100,000 pascals).

Luminous signs according to any variant of the first aspect may further comprise at least one photovoltaic arrangement arranged to receive, from at least one of the at least one peripheral edge surfaces of one of the optical waveguide layers, light captured through an outermost major surface of the respective optical waveguide layer. Optionally, the at least one photovoltaic arrangement is coupled to an electrical energy storage arrangement. Preferably, the energy storage arrangement is enclosed within a body of the sign, and the processor and light source arrangement are configured to receive power from the energy storage arrangement.

In preferred variants of the first aspect, the luminous sign further comprises a transceiver to communicate with a control unit of a security monitoring installation. Optionally, such a sign further comprises an anti-tamper arrangement coupled to the processor, the processor being configured to use the transceiver to communicate an alarm event to the control unit of the security monitoring installation in the event that the anti-tamper arrangement is triggered.

In any variant of the first aspect, the luminous sign may further comprise an optical sensor coupled to the processor, the processor being configured to: determine an ambient light level based on a condition or output of the optical sensor; and to activate the light source arrangement if the determined ambient light level is below a first threshold level for more than a first predetermined period. In such a sign, the processor may be configured subsequently to turn off the light source arrangement if the determined ambient light level exceeds a second threshold level for more than a second predetermined period, the second predetermined period being longer than the first predetermined period.

In any variant of the first aspect, the luminous sign may further comprise a memory that stores information about the timings of transitions from night to day and vice versa, the processor being configured to use the stored information to determine when to activate the light source arrangement and when to deactivate the light source arrangement. In such a sign including a transceiver, the processor may be configured to: receive, from the control unit of the security monitoring installation, information about the timings of transitions from night to day and vice versa; and store the received information in the memory.

In any variant of the first aspect, the photoluminescent structure for at least one of the optical waveguide layers may comprise a transparent carrier upon which the photoluminescent material of the photoluminescent structure is carried.

According to a second aspect there is provided a security monitoring installation comprising a control unit for the installation to manage and control one or more alarm peripherals; the control unit and each of the one or more alarm peripherals including a radio transceiver, each of the one or more alarm peripherals configured to use a respective radio transceiver to provide the control unit with notifications of alarm events; the control unit using its radio transceiver to receive notifications of alarm events and to send control signals to the one or more alarm peripherals; the installation further comprising a luminous sign, according to any variant of the first aspect, having a transceiver to communicate with a control unit of a security monitoring installation.

Brief description of Figures

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying Figures, in which:

Figure 1A illustrates schematically a front elevation of a luminous sign 100 according to an aspect of the invention;

Figure IB shows schematically a cross-section of the device of Figure 1A taken along the line B- B;

Figure 2 shows schematically a residence protected by a security monitoring system according to an aspect of the invention;

Figure 3 shows schematically a first light source arrangement for a luminous sign according to an aspect of the invention; and

Figure 4 shows schematically a second light source arrangement for aluminous sign according to an aspect of the invention;

Specific description

Figure 1A shows schematically a front elevation of a luminous sign 100 according to an aspect of the invention. Figure IB shows the device of Figure 1A schematically in cross section along the line B-B. The sign 100 comprises first 102 and second 104 optical waveguide layers or substrates each comprising a pair of major surfaces 106 and 106’, and 108 and 108’. As illustrated, the waveguide layers are each generally rectangular in shape, the major surfaces each defined by four sides. Each of those sides provides at least one peripheral edge surface 107/109 that extends between the pair of major surfaces. The two optical waveguide layers are arranged so that the major surfaces of one of the two optical waveguide layers is in effect superimposed over (although in the orientation shown the two waveguide layers are positioned one behind the other) the major surfaces of the other of the two optical waveguide layers. It makes housing of the two optical waveguide layers easier if they are generally the same shape and size - although neither of these similarities is actually essential. It will be appreciated that likewise the choice of a rectangular or polygonal shape is also not essential - the optical waveguide layers could be in the form of circles, ovals or other “organic” shapes. The two waveguide layers are typically made of a plastics material such as PMMA, polycarbonate, or polyethylene terephthalate (PET) Etc, but may be made of glass, preferably toughened glass. Each waveguide layer is typically between 3 and 8mm in thickness, optionally between 4 and 6 mm, for example 5 mm thick. Thus the sign effectively consists of two panes of transparent material, such as glass, arranged face to face.

Each of the first 102 and second 104 waveguide layer is provided with a photoluminescent structure 110, 112, that includes photoluminescent material, each photoluminescent structure defining an image. The photoluminescent structure 110 of the first waveguide 102 here comprises a pair of icons and a company name, while that 112 of the second waveguide 104 here comprises three icons and again the company name.

Each photoluminescent structure may conveniently be provided in the form of a transparent film or foil onto which has been printed or otherwise deposited a patern of dots of a photoluminescent material, the patern of dots defining an image, and the transparent film adhering to its associated waveguide layer. The transparent film is typically a polymeric material, for example a polyester such as PET or a material such as PVB (poly-vinyl-butyral). Alternatively, a film-like glass of the type used for the screens or protective overlays for smartphones, e.g., Gorilla Glass, can be used to good effect if cost considerations permit this. The thickness of photoluminescent material making up the image is preferably quite small, generally no more than about 100 microns, typically in the range of 1 to 60 microns, for example around 30 microns in thickness. Consequently, the film and its waveguide substrate may be laminated either with the photoluminescent material sandwiched between the film and the waveguide, or with the film material interposed between the photoluminescent material and the associated waveguide substrate. Generally, however it is preferable to adopt the later construction, with the film material in intimate contact with its waveguide substrate rather than being spaced therefrom by the photoluminescent material because this tends to reduce the maintenance of “air pockets” (although of course the film material may be laminated to the substrate under an atmosphere other than air, e.g. dry nitrogen, and other unwanted visual artefacts.

Instead of the photoluminescent structures being formed on films or foils, the photoluminescent material may be deposited onto the waveguide substrates directly, or one waveguide substrate may have its photoluminescent material deposited directly, and the other waveguide substrate may have its photoluminescent material carried on a film or foil.

The photoluminescent material or materials is/are configured to emit visible emission light (i.e., in the wavelength range of approximately 0.4 to 0.7 pm) on being excited by excitation light, typically of shorter wavelength. Typically, the photoluminescent material or materials comprises one of a fluorophoric dye, quantum dots (in the form of nanocrystals), or a phosphor. In preferred embodiments the photoluminescent material is/are selected from dyes of the type provided by BASF (RTM) under the brand name Lumogen - which are available in shades of yellow, green, orange, pink, and red. These dyes comprise benzoaxanthene derivatives or a perylene perinone dye and have broad absorption bands of around 400 to 600 nm. Lumogen

(RTM) Yellow 083 has an absorption peak of 476nm and an emission peak of 490nm; Lumogen

(RTM) Yellow 170 has an absorption peak of 505nm and an emission peak of 528nm; Lumogen

(RTM) Orange 240 has an absorption peak of 524nm and an emission peak of 539nm; Lumogen

(RTM) Pink 285 has an absorption peak of 547nm and an emission peak of 580nm; and Lumogen (RTM) Red 305 has an absorption peak of 578nm and an emission peak of 613nm. These dyes also exhibit a large Stokes shift so that the risk of reabsorption of emitted photons is reduced.

These or similar dyes can conveniently be formed into printable inks as described in WO2021/099985, where preferred inks are described as:

“With a view on photon efficiency, a preferred embodiment of the device and ink composition are according to the invention characterized in that said acrylate comprises a diacrylate, preferably a glycol di-acrylate, particularly at least one of tri(propylene glycol) diacrylate (TPGDA), tri(ethylene glycol) diacrylate (TEGDA), 1,6-Flexanediol diacrylate (FIDDA) and di(ethylene glycol)diacrylate (DEGDA), wherein most preferably said glycol diacrylate comprises tri(propylene glycol) diacrylate (TPGDA) or 1,6-Flexanediol diacrylate (FIDDA). FIDDA appears to be favourable for quantum dots and green dyes based on benzoxanthene, whereas TPGDA favours red dyes like RED-305.

Excellent results are achieved in this sense with a specific embodiment of the ink composition according to the invention wherein the composition comprises between 0,01 and 5 wt%, particularly between 0,01 and 2,5 wt%, more particularly between 0,25 wt% and 1,25 wt%, even more particularly around 1 wt%, of a dye as said luminescence agent and/or wherein the composition comprises between 0,01 and 25 wt%, particularly between 1 wt% and 15 wt%, more particularly around 10 wt%, of quantum dots as said luminescence agent.

In a preferred embodiment said ink composition according to the invention is characterized in that said ink composition has a viscosity in a range of between 1 and 100 mPa.s at an application temperature between 25 °C and 33 °C, preferably between 5 and 30 mPa.s at said application temperature. This allows the ink composition to be applied in a thin layer using a thin film deposition technology, like for instance inkjet printing, screen printing, gravure printing, flexographic printing or lithography.”. The photoluminescent structures may comprise a single photoluminescent material or a mix of photoluminescent materials. In order to improve the sign’s visual attention-grabbing effect, the pair of images is preferably composed so that there is some contrast in colour between the two images. Optionally different parts of one image may use photoluminescent materials that luminesce with different colours - for example, using different dyes. One or both images may be formed in this way, and by contrasting the positions and colours of image elements in the two images effects that are very visually striking - and that attract attention even when seen only through peripheral vision can be produced.

Excitation light is provided by a light source arrangement 114 configured to launch excitation light into each of the first 102 and second 104 waveguide layers through respective peripheral edge surface 107”7109”’. In this simplified, schematic representation the light source arrangement 114 is shown as being confined to a module positioned above (i.e. adjacent the upper edge of) the first 102 and second 104 waveguide layers, although in practical implementations the light source arrangement may be provided on one, some, or all of the peripheral edge surfaces of the first 102 and second 104 waveguide layers.

The luminous sign 100 includes a processor, not shown, that is configured to activate the light source arrangement 114 to launch excitation light selectively into the first 102 or the second waveguide layers 104 to cause the respective photoluminescent structure to display the respective image as a pattern of emission light. That is, by selectively launching excitation light into either the first 102 or second 104 optical waveguide layers, either the first 110 or the second 112 photoluminescent structure can be excited causing the relevant image to be displayed. By alternating activation between the two optical waveguide layers, the respective images are alternately displayed as a pattern of emission light creating the appearance of movement. Preferably, as here the appearance created is that of lateral - side to side - movement, as this is very effective at attracting human attention, even when only observed using peripheral vision. Consequently, by simulating movement, signs according to embodiments of the invention can be much more effective in attracting attention than “static” signs of the same size, location, and luminosity, and in this way the deterrent effect of the sign is increased thereby increasing the likelihood that villains will leave the protected property unmolested. In some embodiments, the processor may be configured under some circumstances to cause light to be launched into both waveguides so that both images are activated simultaneously.

Figures 1A and IB also show the presence of an optional, albeit preferred, feature and that is the provision of one or more photovoltaic arrangements 116 arranged to receive, from at least one of the at least one peripheral edge surfaces of one of the optical waveguide layers, light captured through an outermost major surface of the respective optical waveguide layer. That is, light that enters the “face” (or front-elevation) of the sign is captured by an optical waveguiding layer to emerge at one or more peripheral edge surfaces of the relevant optical waveguide layer and there stimulates a photovoltaic arrangement (which may comprise one or more photovoltaic cells) 116. In this way, energy from sunlight can be captured by a photovoltaic arrangement 116 and used to power the sign (the processor and the light source arrangement 114). In this way the sign can function as a luminescent solar concentrator (LSC), potentially meaning that the sign can power itself without needing either to be connected to mains electricity or needing to rely on a non-rechargeable battery or battery swapping of rechargeable cells.

Preferably the sign 100 also includes a rear element 150 in the form of a Lambertian scatterer which may simply be a plastic, glass or metal substrate which is provided with a matt surface or surface treatment, preferably white (e.g., paint or powder coating).

Sunlight (or potentially other light) entering the sign 100 through its exterior face excites the photoluminescent material(s) resulting in luminescent emission. The radiation from luminescent emission is emitted more or less omnidirectionally and hence some of this radiation enters the associated optical waveguide where it is guided, by total internal reflection, to emerge at the peripheral edges of the waveguide. Similarly, excitation light launched into the waveguide is guided by total internal reflection but some of the light escapes through the major faces of the waveguide to impinge on the photoluminescent material(s) again resulting in luminescent emission.

If, as preferred, photovoltaic elements are provided, they may be provided on only the outermost waveguide if there is sufficient space along the periphery to accommodate sufficient PV elements to provide enough charging current to reliably charge the energy storage device. Particularly for temperate climates, where the day length varies significantly throughout the year, it may be necessary or at least preferable to provide PV elements along the periphery of each optical waveguide. Each PV element will typically generate about 0.6V, so that by series connecting 6 PV devices a useful voltage of 3.6 Volts can be achieved. A convenient way to mount and locate multiple PV elements is described in WO2020/197388, see in particular Figures 2 to 7, the relevant disclosure of which is hereby incorporated by reference. The provision of front and back electrical conductors which permit the series connection of PV devices by stacking the devices so that the back electrical connector of one device is in contact with the front electrical connector of an adjacent device, and so on. Because, unlike WO2020/197388 we are more concerned with our device 100 functioning as a sign rather than primarily as an LSC as a power source, embodiments of the invention may conveniently be realised with fewer PV elements than could potentially be accommodated. The light source arrangement may be provided as a set of modules, one for each illuminated side of the sign 100 - typically just one or two sides, as may the photovoltaic assemblies -again typically only one or two sides of the sign will receive such assemblies. The sign 100 preferably includes a peripheral frame 118 that may serve to protect the various components of the sign, and which may also include a mounting arrangement and a tamper detection arrangement. The peripheral frame is preferably made of anodised aluminium or stainless steel, optionally of elements having a U-shaped profile.

The two optical waveguides 102 and 104 with their associated photoluminescent structures 110 and 112 are preferably sealed together by means of a peripheral seal 120. The peripheral seal 120 is preferably resilient and substantially impermeable to moisture, for example a silicone-based mastic, or the like, of the type used for sealing glazing units for double-glazed windows.

Figure 2 shows schematically the facade of a house 200 on which is mounted a sign 100 according to an embodiment of the invention. The house is protected by a security monitoring installation of which the sign is a peripheral. Other peripherals include a video camera 202 with an integral motion sensor, and magnetically triggered contact switches, not shown, on the doors and windows. The security monitoring installation is controlled by a control unit, not shown, within the protected area of the house, the control unit being configured to manage and control the alarm peripherals. The control unit and each of the one or more alarm peripherals preferably include a radio transceiver. Each of the alarm peripherals is configured to use its radio transceiver to provide the control unit with notifications of alarm events, and the control unit is preferably configured to report alarm events to a remote monitoring station 204 via the Internet 206 or via a radio link such as over a public land mobile network 208. At the remote monitoring station 204 human operatives review reported alarm events, intervening as appropriate to send the police or other security personnel to the premises, and guiding the security personnel using information from sensors and images from cameras, etc.

The control unit uses its radio transceiver to receive notifications of alarm events and to send control signals to the one or more alarm peripherals, for example instructing video cameras to forward captured images/video which the control unit then forwards to the remote monitoring station. In the installation shown the luminous sign also includes a transceiver to receive instructions and data from the control unit of the security monitoring installation. In particular the control unit may be configured to acquire up to date information on the timings of transitions from night to day and vice versa - for example the time for sunset and sunrise, or some offset from these times that reflects night’s arrival and departure, possibly adjusted to take account of the geographical location of the installation. For example, this information may be provided periodically from a cloud-based service or other bank end function run by or for the system provider/installer, or some independent entity, or acquired by the central unit periodically “visiting” an external source of such data, such as a national or regional weather forecasting organisation or a broadcasting entity (such as the BBC). The relevant information can then be transmitted from the security monitoring system’s control unit to the controller of the sign, by means of the two devices’ transceivers. The processor of the sign may then be configured to store the relevant information in a memory for use in determining when to activate the light source arrangement so that the sign is active (meaning that excitation light is being supplied from the light source arrangement) during the appropriate nocturnal hours.

The sign 100 in the Figure 2 installation may also include an anti -tamper arrangement, that responds to any attempt to remove the sign from its mounting point, or any attempt to disassemble the sign. The anti-tamper arrangement is configured to causes an event message to be sent by the sign’s transceiver to the installation control unit which may then send instructions to any video cameras of the system, such as camera 202, in an attempt to acquire images of the person interfering with the sign. Although it may be considered that theft of, or interference with, the sign is rather a trivial matter, such petty acts of vandalism are often precursors to more serious misbehaviour and it is therefore more important to deal with such infractions than one might imagine.

Figures 3 and 4 show schematically alternative approaches to applying excitation light to the first 102 and second 104 optical waveguides. In Figure 3 the light source arrangement 114 comprises a first set of light sources 302 dedicated to the illumination of the first waveguide 102, and a second set of light sources 304 dedicated to the illumination of the second waveguide 104. Each set of light sources may comprise one or more than one individual light sources, each typically in the form of a light emitting diode. Each set of light sources may be coupled to its associated optical waveguide by means of a light diffusing optical fibre such as that offered by Coming (RTM) as Fibrance (RTM) Light-Diffusing Fibre 2. This is a glass optical fibre that has an operating wavelength range of 420 to 700 nm and emits laterally (with a 120-degree viewing angle) continuous, uniform light which makes it ideally suited to this application. This fibre also has a small minimum bend radius which is also very useful in this application. In preferred embodiments a single laser is coupled to a light-diffusing fibre that provides excitation light to an individual waveguide. Alternatively, instead of coupling the light sources to the optical waveguide layers by means of an optical fibre, the output of the light sources may be arranged to impinge directly onto a peripheral edge surface 107 of the relevant waveguide either “on axis” or “off axis”, that is the “beam” of light emitted by the light source is either for directed along a path that is parallel to the opposed major faces (106 and 106’, or 108 and 108’) for on-axis launching, or at an oblique angle with respect the normal to the planes defining these major faces (in effect launching the light so that it is angled slightly towards one or other of the major faces of the relevant waveguide). Depending upon the lengths of the sides of the sign 100 one or more than one light source may be provided along a single edge of each waveguide of the sign to ensure that excitation light spreads throughout the relevant waveguide so that excitation light reaches under every part of the photoluminescent structure.

Typically a sign for use to announce the presence of a security monitoring installation may be in the region of 20cm by 15cm, or A4 size (approximately 210mm by 300mm) but larger or smaller signs may be provided. The invention is of course also applicable to much larger signs - e.g. up to the size of billboards (in the US 14 feet (4.27m) high by 48 feet (14.63m) wide, or in the UK 480 inches by 120 inches - 12.19m x 3.05m), for example for use in advertising.

Figure 3 also shows a control module 305 for the sign 100, the module containing the processor 306 - which will typically be a microcontroller or micro-control unit (MCU), with an internal memory, together with a power supply 308. The power supply may be mains powered, optionally with battery back-up, but is preferably in the form of a rechargeable battery 308 which is coupled to a charging arrangement 310. The charging arrangement 310 is preferably controlled by the processor 306 and receives power from the photovoltaic arrangement 116. Preferably, as shown, the control module 305 also includes a transceiver 308 for communication with the control unit of the security monitoring installation. Preferably the transceiver 308 communicates with the control unit using a low power narrow bandwidth channel, for example using the Matter protocol, BlueTooth low energy, or a channel in an ISM band such as the 868MHz channel.

Figure 4 corresponds closely with Figure 3 but shows an alternative light source arrangement 114 which includes one or more light sources 400 that are used both to illuminate the first waveguide and to illuminate the second waveguide, an optical switch 402 being provided between the one or more light sources 400 and the pair of optical waveguides, the switch being coupled to and controlled by the processor 306 and being operative to apply excitation light alternately to the first 102 and second 104 optical waveguide. The optical switch switches light applied at a single input 403 to one or other of two output ports 404, 405, each output port being dedicated to a different one of the optical waveguide layers 102, 104. Light may conveniently be coupled from the output ports to the associated optical waveguide layer 102, 104 using a diffusing fibre arrangement as previously described with reference to Figure 3. Conveniently the optical switch is provided with fibre pigtails which are readily coupled to, for example, a single laser source of excitation light, and to a pair of diffusing fibres one for each of the optical waveguides of the sign 100. By providing a sign as described, where two (or more) waveguides can in effect be activated to cause light to be emitted from different images it is possible to provide motion-like simulation effects - and these can be extremely effective in signage used for advertising, as well as being visually striking and hence useful in the present application.

The light source arrangements may be configured to pulse the excitation light rather than to provide a continuous supply of a given intensity, the pulse rate being so chosen that no pulsing of the emission of the photoluminescent sources is discernible to the human eye - for example at a frequency of 25Hz or more, perhaps with a 50/50 duty cycle. This may help to reduce energy consumption and hence permit the use of a lower-capacity rechargeable power source and in turn reduce the energy required of the PV arrangement - thereby reducing costs and also potentially reducing the size of the PV module(s) required.

The light source arrangements could additionally or alternatively be arranged to pulse, under the control of the processor 306, as a means to attract more attention. For example, in the event that the control unit of the security monitoring installation receives an event notification from an alarm peripheral, the control unit could be configured to signal to the sign to cause its processor to cause the sign to flash - perhaps by activating the light sources for both waveguides simultaneously (where this is possible) and alternately turning both on or both off - so that he sign as a whole flashes at a rate readily detectable by a human - for example turning on and off once every 1 or 2 seconds.

Although the invention has been described on the basis that the sign comprises just two superimposed waveguides, it will be appreciated that more than two waveguides (e.g. 3 or 4 waveguides) may be superimposed to enable the display of multiple possible visual effects and potentially the display of more complex visual effects. As noted above, the light sources for more than one waveguide layer (for a subset or for all of the waveguide layers) may be activated simultaneously.

Optionally a sign according to the first aspect of the invention may include a third waveguide layer (similar to the first two layers) provided with a photoluminescent structure including photoluminescent material, the photoluminescent material being configured to emit visible emission light on being excited by excitation light, the photoluminescent structure of the third layer defining a warning message (e.g. such as “Help” or “emergency”), the sign further comprising an RF transceiver (or RF receiver) and a processor configured to cause the display to display the warning message by activating the third layer upon receiving an instruction so to do via the RF transceiver/receiver. Such a sign may be provided as part of a security monitoring system installation, so that a control unit of the installation can signal the sign to cause the display of an alarm/waming sign in the event of an incident. Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

Signs according to any variant of the first aspect may also include or be coupled to a proximity sensor such as a PIR detector and be configured to turn on, or change illumination behaviour, on based on triggering of the proximity sensor. There are some uses cases where users may not like to leave the deterrence panel always on, and signs according to any variant of the first aspect may include an on/off control such as a push button, although optionally the on/off control may include an NFC antenna arrangement and be configured to use this to achieve secure activation/deactivation. But by providing a proximity sensor in (or associated with) the sign the option is provided to light up the panel when presence and/or motion is detected in the surroundings. In this way, deterrence capabilities are still provided even if the sign is nominally turned off on a regular basis. In addition, a sign provided with or associated with a proximity detector (e.g. PIR Thermal MOS sensor, radar) could also be configured to transmit an alert (via RF or via a wired connection) to a security monitoring system (e.g. to a controller of such a system) in the event that the proximity detector is triggered - in effect functioning as an alarm node of the security monitoring system.

Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

Signs according to any variant of the first aspect may also include an output port to power/recharge external devices, this enables advantage to be taken of the energy harvested by the solar cells or the deterrence panels we can power other (outdoor) devices of an alarm installation. By including an electrical output port in the deterrence panel, a user would be able to link a (video) camera, a video doorbell, an external keypad, or any other device via a cable to be recharged by the battery of the deterrence panel. Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

Signs according to any variant of the first aspect could be coupled to a security monitoring installation (for example via a radio link) and configured to trigger flashing/steady lights when an alarm is triggered in the security monitoring system For example, in case of intrusion detected either within the house or within a protected area of the garden or outdoor space, and signs according to any variant of the first aspect could flash to deter burglars and/or to attract the attention of neighbours and/or passers-by or the police. Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

Signs according to any variant of the first aspect could be configured to include a siren which can be activated (for example via a radio link) in the event of an alarm event in an associated security monitoring system. Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

Signs according to any variant of the first aspect could be configured to be turned on or off remotely, or placed in a proximity-triggered mode, via a wireless link - for example under user control, the user having an app on a device, such as a smartphone, the app cooperating with a cloud-based backend of a security monitoring system of the premises. Additionally this functionality may be incorporated into security monitoring installations according to the second aspect.

It will be appreciated that signs according to any variant of the invention could be in the form of multi-pane display elements. When activated, such signs could be arranged to activate alternately different panes of the multi-pane display.

Signs and/or displays according to any aspect or variant may be fabricated using electroluminescent inks instead of or in addition to materials previously disclosed and described. For example, suitable electroluminescent inks are available from the DuPont corporation under the trade name Luxprint, others are available from Micromax (in Europe available via the distributor CCI Eurolam), and “Saral” brand inks are available from Saralon Electronics.

Signs and/or displays according to any aspect or variant of the invention may be provided in the form of a “sticker” that can be applied to an existing structure or surface, such as a window, a display panel, name board, or an alarm node, camera, or siren of a security monitoring installation - optionally one that was previously installed, etc. The “sticker” may be provided with an integral adhesive layer, but may alternatively be provided in a form that can be secured to a substrate by means of an applied adhesive (spray adhesive, brushed or spread adhesive, double-sided tape, etc.). Such “stickers” may make use of electroluminescent inks, as previously mentioned. Such stickers may include photoelectric elements to generate electricity from optical radiation (UV, IR, visible or some combination of these), optionally linked to an electrical storage device such as a rechargeable battery or supercapacitor. Indeed, any feature of any previously disclosed or suggested variant may take the form of a “sticker” for application to a suitable support surface. Sticker type devices with energy storage and/or electricity generating capability may be coupled to other devices to provide back up or trickle charging power. Conversely, sticker type device may also be coupled to existing (optionally previously installed) devices, such as elements of a security monitoring system, to draw power from the existing device - for example via a wired connection (or be electromechanically coupled, eg, inductively coupled to the other device to draw power). Conveniently, components and devices of the security monitoring system may include power transfer ports (e.g. sockets or plugs) to enable convenient connection to sticker type devices as well as to other sign/display devices according to any aspect or variant of the invention.

Claims

1. A luminous sign comprising first and second optical waveguide layers each comprising a pair of major surfaces and at least one peripheral edge surface between the pair of major surfaces, the major surfaces of one of the two optical waveguide layers being superimposed over the major surfaces of the other of the two optical waveguide layers; each of the first and second waveguide layers being provided with a photoluminescent structure including photoluminescent material, the photoluminescent material being configured to emit visible emission light on being excited by excitation light; each photoluminescent structure defining an image; a light source arrangement configured to launch excitation light into each of the first and second waveguide layers; and a processor configured to activate the light source arrangement to launch excitation light into the first waveguide layer or into the second waveguide layers to cause the respective photoluminescent structure to display the respective image as a pattern of emission light.

2. The luminous sign of claim 1, wherein the light source arrangement includes a first set of light sources dedicated to the illumination of the first waveguide, and a second set of light sources dedicated to the illumination of the second waveguide.

3. The luminous sign of claim 2, wherein the light sources arrangement includes one or more light sources configured to emit light onto an edge face of the respective waveguide.

4. The luminous sign of claim 1, wherein the light source arrangement includes one or more light sources that are used both to illuminate the first waveguide and to illuminate the second waveguide.

5. The luminous sign of claim 4, wherein the light source arrangement includes an optical switch that is controlled by the processor to switch light to the first waveguide or to the second waveguide.

6. The luminous sign of any one of the preceding claims, wherein the light source arrangement includes for each optical waveguide a light diffusing optical fibre to supply light to the waveguide from one or more of the respective light sources.

7. The luminous sign of any one of the preceding claims, wherein the first and second optical waveguide layers are separated by a gas-filled gap.

8. The luminous sign of claim 7, wherein the gap is filled with a moisture-free gas at a pressure below 100,000 pascals.

9. The luminous sign of any one of the preceding claims, further comprising at least one photovoltaic arrangement arranged to receive, from at least one of the at least one peripheral edge surfaces of one of the optical waveguide layers, light captured through an outermost major surface of the respective optical waveguide layer.

10. The luminous sign of claim 9, wherein the at least one photovoltaic arrangement is coupled to an electrical energy storage arrangement.

11. The luminous sign of claim 10, wherein the energy storage arrangement is enclosed within a body of the sign, and the processor and light source arrangement are configured to receive power from the energy storage arrangement.

12. The luminous sign of any one of the preceding claims, further comprising a transceiver to communicate with a control unit of a security monitoring installation.

13. The luminous sign of claim 12, further comprising an anti-tamper arrangement coupled to the processor, the processor being configured to use the transceiver to communicate a tamper event to the control unit of the security monitoring installation in the event that the anti-tamper arrangement is triggered.

14. The luminous sign of any one of the preceding claims, further comprising an optical sensor coupled to the processor, the processor being configured to: determine an ambient light level based on a condition or output of the optical sensor; and to activate the light source arrangement if the determined ambient light level is below a first threshold level for more than a first predetermined period.

15. The luminous sign of claim 14, wherein the processor is configured subsequently to turn off the light source arrangement if the determined ambient light level exceeds a second threshold level for more than a second predetermined period, the second predetermined period being longer than the first predetermined period.

16. The luminous sign of any one of the preceding claims, further comprising a memory that stores information about the timings of transitions from night to day and vice versa, the processor being configured to use the stored information to determine when to activate the light source arrangement and when to deactivate the light source arrangement.

17. The luminous sign of claim 16 as dependent on claim 12, the processor being configured to: receive, from the control unit of the security monitoring installation, information about the timings of transitions from night to day and vice versa; and store the received information in the memory.

18. The luminous sign of any one of the preceding claims, wherein the photoluminescent structure for at least one of the optical waveguide layers comprises a transparent carrier upon which the photoluminescent material of the photoluminescent structure is carried.

19. The luminous sign of any one of the preceding claims, further comprising a third optical waveguide layer comprising a pair of major surfaces and at least one peripheral edge surface between the pair of major surfaces, the major surfaces of the third optical waveguide layer being superimposed over the major surfaces of the other two optical waveguide layers; the third waveguide layer being provided with a third photoluminescent structure including photoluminescent material, the photoluminescent material being configured to emit visible emission light on being excited by excitation light; the third photoluminescent structure defining a third image; wherein the light source arrangement is further configured to launch excitation light into the third waveguide layer; and the processor is further configured to activate the light source arrangement to launch excitation light into the third waveguide layer to cause the third photoluminescent structure to display the third image as a pattern of emission light.

20. A security monitoring installation comprising a control unit for the installation to manage and control one or more alarm peripherals; the control unit and each of the one or more alarm peripherals including a radio transceiver, each of the one or more alarm peripherals configured to use a respective radio transceiver to provide the control unit with notifications of alarm events; the control unit using its radio transceiver to receive notifications of alarm events and to send control signals to the one or more alarm peripherals; the installation further comprising a luminous sign as claimed in claim 12 or any one of claims 13 to 19 as dependent on claim 12.