WO2023094149A1

WO2023094149A1 - A method of installing a sensor unit for a security monitoring system and a kit of parts including sensor unit assembly

Info

Publication number: WO2023094149A1
Application number: PCT/EP2022/081195
Authority: WO
Inventors: Christian Westergren; Rinaldo Filinesi
Original assignee: Verisure Sàrl
Priority date: 2021-11-26
Filing date: 2022-11-09
Publication date: 2023-06-01
Also published as: EP4187516A1; AR127739A1

Abstract

The present invention relates to a method a of installing a sensor unit for a security monitoring system comprising the steps of selecting dependent on a desired detection area and/or detection range of the sensor unit (10) an interchangeable cover (12) from a plurality of different interchangeable covers (12), wherein the different interchangeable covers (12) are adapted to restrict differently the field of view of a motion detector (14) of the sensor unit (10); and connecting the selected interchangeable cover (12) to the sensor unit (10). Also provided is a corresponding kit of parts including a sensor unit assembly, comprising a sensor unit (10) with image capture means (18) configured to capture an image and/or a video of a monitored area and a motion detector (14), in particular a passive infrared, PI R, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means (18); and a plurality of interchangeable covers (12), each configured to be connected to the sensor unit (10), wherein different interchangeable covers (12) are configured to cover different parts of a lens or lens array of the motion detector (14) when connected to the sensor unit (16).

Description

A method of installing a sensor unit for a security monitoring system and a kit of parts including sensor unit assembly

The present invention relates to a method of installing a sensor unit for a security monitoring system. Furthermore, the invention relates to a sensor unit assembly.

Security monitoring systems for monitoring premises typically provide a means for detecting the presence and/or actions of people at the premises and reacting to detected events. Commonly such systems include sensors to detect the opening and closing of doors and windows, sensors in the form of movement detectors to monitor spaces for signs of movement, microphones to detect sounds such as breaking glass, and image sensors to capture still or moving images of monitored zones. Such systems may be self-contained, with alarm indicators such as sirens and flashing lights that may be activated in the event of an alarm condition being detected. Such installations typically include a central unit that is coupled to the sensors, detectors, cameras, etc. (“nodes”), and which processes receive notifications and determines a response. The central unit is typically linked to the various nodes wirelessly, rather than by wires, since this facilitates installation and also provides some safeguards against sensors/detectors effectively being disabled by disconnecting them from the central unit. Similarly, for ease of installation and to improve security, the nodes of such systems are typically battery rather than mains powered. Alternatively, a security monitoring system may include an installation at a premises, domestic or commercial, that is linked to a Central Monitoring Station (CMS) where typically human operators manage the responses required by different alarm and notification types. In such centrally monitored systems, the central unit at the premises installation typically processes notifications received from the nodes in the installation and notifies the Central Monitoring Station of only some of these, depending upon the settings of the system and the nature of the detected events. In such a configuration, the central unit at the installation is effectively acting as a gateway between the nodes and the Central Monitoring Station.

An important part of such security monitoring systems typically are the means for detecting the presence and/or actions of people or other detection targets, in particular moving objects. Commonly, such systems include motion sensors monitoring defined areas for signs of movement and imaging means to capture images or videos of a monitored area in the event that movement is detected.

In many commercially available security monitoring systems, passive infrared sensors (PIR) are applied for the purpose of motion detection. Such sensors typically comprise a sensor package, hermetically sealed, inside which there are typically a balanced pair of sensor elements which are exposed to IR radiation through one or more windows in the hermetic package. Typically, the PIR includes an optical arrangement, in the form of one or more lenses, that determines what the PIR sensor can “see” - e.g. how broadly, where, and how far. The lenses are typically provided in the form of Fresnel lenses. Generally, rather than using a single lens with a single focal length, an array of lenses with a range of different focal lengths are used, so that the PIR can “see” across a range of areas. Fresnel lenses and Fresnel lens arrays are attractive for this application because they can be made small and thin, so that they can be very compact. They can also be moulded from cheap plastic, meaning that the cost of the PIR can be kept down. Although moulded plastics Fresnel lenses are cheap and generally convenient, their optical performance can be adversely affected if they move relative to the sensor elements and if they are bent or otherwise deformed. Typically, being made of semi-soft plastics material, Fresnel lenses are easily damaged or distorted, changing and impairing their optical performance.

Movement sensors, such as PIR sensors, can be installed indoors or outdoors, for example to monitor rooms, entrances to dwellings such as houses or any or other area of interest. In order to avoid false alarms, it is desirable to restrict the monitoring area of the sensor to the area(s) of interest. At the same time, movement events of objects outside the area of interest should not result in activation of the security monitoring system. For example, when the movement sensor is installed to monitor a garden and a public path is located just beyond a garden fence, it would be desirable to prevent the movement sensor from being triggered by people walking along the public path.

However, the area of interest may significantly differ from application to application. Hence, a means for detection area adaption is required to ensure proper functionality of the system.

It is known that detection area adaption to specific applications can be achieved by precise adjustment of the mounting position of the sensor, both in terms of height and orientation (inclination to the vertical as well as azimuth) during the installation of the sensor, and/or by software means, for example programs which electronically regulate the sensor detectivity, during the commissioning of the security monitoring system. However, perfecting the positioning of the sensor and/or software calibration often requires extensive trial and error approaches and is consequently very time-consuming and expensive. It is understandable that an installation engineer may not have the time and/or patience to invest the time and effort necessary for correct calibration, resulting in imperfect functionality of the security monitoring system. In consequence, the sensor may routinely generate false alarms (which are expensive for the system supplier/operator to deal with) and these may lead to the relevant sensor being disabled or even the whole security monitoring system being turned off.

Hence, there is a need to provide fast and cheap means for application specific detection area adaption of movement sensors for security monitoring systems.

Summary

According to a first aspect there is provided a passive infrared, PIR, motion sensor or a camera including a PIR sensor, having a plurality of different interchangeable covers or masks by means of which the field of view of the PIR sensor can be adjusted to suit a particular installation location.

Such a passive infrared, PIR, motion sensor or a camera including a PIR, may include a body which includes a lens or lens array for the sensing arrangement of the PIR, different interchangeable covers (or masks) of the plurality being mountable to and demountable from the body and being configured to cover different portions of the lens or lens array while leaving exposed another portion of the lens or lens array. Preferably each of the covers or masks is mountable to the body in such a way as to avoid distorting at least the exposed portion of the lens or lens array. Preferably, when one of the interchangeable covers or masks is mounted to the body, the mounted cover or mask is spaced from the lens or lens array by an air gap.

Each of the interchangeable covers or masks may be configured as an end cap. The interchangeable covers or masks are preferably configured to be attached to the motion sensor or camera without the use of adhesives or screws. Preferably, each cover or mask is configured to clip to or snap fit to the motion sensor or camera.

Each of the interchangeable covers or masks may include a differently positioned or dimensioned aperture to expose only the selected portion of the lens or lens array

The motion sensor or camera according to the first aspect preferably includes an anti-tamper arrangement configurable to trigger an alarm event in the event that a cover or mask secured to the sensor is removed from the sensor

Each of the interchangeable covers or masks is preferably provided in the form of a self-supporting structure.

The body and each of the different interchangeable covers or masks may be injection moulded from a thermoplastic material. Preferably the body and the interchangeable covers or masks are injection moulded from polycarbonate.

An interchangeable cover or mask may be configured to accept one or more mask inserts to enable the interchangeable cover to be configured for a particular installation by, for example, masking both near and far zones otherwise monitorable by the motion sensing device. The interchangeable cover and the mask inserts may be configured to clip or snap fit together, preferably with the mask inserts located on an inner surface of the interchangeable cover so that they are only removable from the inner side of the cover.

According to a second aspect of the invention there is provided a method of tuning a passive infrared, PIR, motion sensor to suit a particular installation location, the PIR including a lens or lens array to focus light onto the sensing arrangement of the sensor, the method comprising selecting a cover from a collection of a plurality of covers, each cover having a different configuration to expose a different portion of the lens array, the selected cover having being appropriately configured (e.g. appropriately positioned and dimensioned) to expose only a selected portion of the lens or lens array to restrict the field of view of the sensor to suit the particular installation location.

Each cover (which may also be termed a mask) may include a differently positioned or dimensioned aperture to expose only the selected portion of the lens or lens array.

Each cover may be configured to clip to or snap fit to the motion sensor.

According to a further aspect of the invention, there is provided a battery- powered sensor unit assembly, comprising a sensor unit with image capture means configured to capture an image and/or a video of a monitored area and a motion detector, in particular a passive infrared, PI R, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means, the sensor unit having a housing including a battery compartment to receive one or more batteries to power the sensor unit, the battery compartment including a closure element for closing the battery compartment; and a removable masking element connected to the sensor unit and covering part of a lens of the motion detector; wherein the removable masking element is secured to the sensor unit assembly by the closure element of the battery compartment, the removable masking element only being removable from the sensor unit assembly once the closure element of the battery compartment is opened/released. Optionally, the battery compartment closure is provided with an anti-tamper arrangement which is triggered by removal of the battery compartment closure, the anti-tamper arrangement also being triggered by removal of the removable masking element. This aspect may be combined with any of the features or elements of other aspects and embodiments of the invention.

According to a further aspect of the invention, there is provided a battery- powered sensor unit assembly, comprising a sensor unit with image capture means configured to capture an image and/or a video of a monitored area and a motion detector, in particular a passive infrared, PIR, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means, the sensor unit having a housing including a battery compartment to receive one or more batteries to power the sensor unit, the battery compartment including a closure member to close the battery compartment; and a removable cover connected to the sensor unit and covering part of a lens of the motion detector; wherein the removable cover is kept in place by the closure member of the battery compartment, the removable cover only being removable once the closure member of the battery compartment is released. This aspect may be combined with any of the features or elements of other aspects and embodiments of the invention.

The motion sensor preferably includes an anti-tamper arrangement configurable to trigger an alarm event in the event that a cover secured to the sensor is removed from the sensor.

The object of the invention is also solved by a method of installing a sensor unit for a security monitoring system comprising the steps of selecting dependent on a desired detection area and/or detection range of the sensor unit an interchangeable cover from a plurality of different interchangeable covers, wherein the different interchangeable covers are adapted to cover different parts of a motion detector of the sensor unit; and connecting the selected interchangeable cover to the sensor unit.

In an aspect, the invention also provides a method of installing a sensor unit for a security monitoring system comprising the steps of selecting dependent on a desired detection area and/or detection range of the sensor unit an interchangeable cover from a plurality of different interchangeable covers, wherein the different interchangeable covers are adapted to restrict differently the field of view of a motion detector of the sensor unit; and connecting the selected interchangeable cover to the sensor unit.

Optionally, the interchangeable covers are connected to the sensor unit by means of one or more connection elements, each comprising a first connection member positioned at the sensor unit and a second complementary connection member positioned at the interchangeable cover to be connected.

The interchangeable covers can be for example cheap and easy to attach injection moulded plastic parts with different shapes and/or sizes adapted to absorb or reflect incoming radiation, in particular infrared light. By selecting and connecting a suitable cover to the sensor unit, radiation emerging from locations outside of the area of interest can be blocked selectively, thereby calibrating the detection area in a purely hardware-based and time-efficient manner.

In a preferred embodiment of the method, a user (or, more typically, an installation engineer) performs at least the step of connecting the selected interchangeable cover or covers during installation of the sensor unit at a building structure. Mounting of the sensor unit to a desired spot from which the area of interest can be observed typically anyhow requires a user (or, more typically, an installation engineer) interaction. Synergistically combining this action with the connection of the cover to the sensor unit obviates additional calibration steps to define the detection area, thereby minimizing the total installation and calibration effort.

In an embodiment of the method, more than one (e.g. two) interchangeable cover can be selected. By using multiple covers, incoming radiation from defined locations that should not be monitored, i.e. locations very close to and very far away from the security monitoring system, can be blocked so that the sensor “sees” only an intermediate (“Goldilocks”) zone. This enables a lens array or lens portions to be shielded at different positions spaced apart from each other, thereby restricting the extent of the region being monitored. For example, by mounting the two covers such that incoming radiation is blocked from reaching the top and bottom end of the lens array or lens portions, a minimum and maximum detection range can be defined simultaneously.

The object of the invention is also solved by a kit of parts including a sensor unit assembly, in particular for performing a method according to the invention, comprising a sensor unit with image capture means configured to capture an image and/or a video of a monitored area and a motion detector, in particular a passive infrared (PIR) sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means; and a plurality of interchangeable covers, each configured to be connected to the sensor unit and wherein different interchangeable covers are configured cover different parts of a lens or lens array of the motion detector when connected to the sensor unit. In an aspect, the present invention also provides a kit of parts including a sensor unit assembly, comprising a sensor unit with image capture means configured to capture an image and/or a video of a monitored area and a motion detector, in particular a passive infrared, PI R, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means; and a plurality of interchangeable covers, each configured to be connected to the sensor unit, wherein different interchangeable covers are configured to restrict differently the field of view of the motion detector when connected to the sensor unit to restrict differently the field of view of the motion detector.

Optionally, the different interchangeable covers are configured to restrict differently the field of view of a motion detector by covering different parts of a lens or lens array of the motion detector when connected to the sensor unit.

The advantages that were discussed for the method also apply to these kits of parts.

Optionally the sensor unit, for example of the kit of parts, includes a battery compartment having a battery compartment cover, and the interchangeable covers are so configured that the covers can only be mounted to or removed from the sensor unit while the battery compartment cover of the sensor unit is absent, the interchangeable covers being securable to the sensor unit by securing the battery compartment cover to the sensor unit. The interchangeable cover(s) can thus be secured without the need for an additional fastening arrangement which may reduce moulding complexity and cost, while providing enhanced security of retention.

Optionally, the sensor unit, for example of the kit of parts, includes an antitamper arrangement for the battery compartment cover, the anti-tamper arrangement also providing anti-tamper protection for an interchangeable cover. In this way the interchangeable cover(s) is/are protected by an anti-tamper arrangement without the need to provide a further one in addition to that already provided for the battery compartment.

Optionally an interchangeable cover of the plurality of covers is configured to receive one or more shutter elements on an inner surface of the interchangeable cover prior to connecting the interchangeable cover to the sensor unit. In this way a cover can be configured appropriately for a particular situation while reducing the amount of material needed to provide a desired solution.

The interchangeable cover may be configured to couple to the or each shutter element through a snap fit interface arrangement. In this way, shutter elements may be coupled to the cover quickly and reliably without the need for further separate fastening elements and without the use of tools.

Optionally each of the plurality of interchangeable covers is configured to be connected to the sensor unit by means of a connection element, wherein the connection element comprises a first connection member positioned at the sensor unit and a second complementary connection member positioned at the interchangeable cover.

In a preferred embodiment, the connection element is a clip or snap connector. This allows fast and easy connection of covers to the sensor unit, in particular without the need for additional tools.

Typically, the motion detector comprises a lens array, in particular of a Fresnel type to focus incoming light from different zones or regions onto an active sensing part of the motion detector. In particular, the Fresnel lens allows influencing the beam path and shape of incoming radiation in a very space saving manner. In a simple arrangement, the Fresnel lens array can form an exposed surface of the motion detector.

Preferably, the lens array comprises multiple zones of different focal lengths. This allows focusing radiation from different locations or regions within the detection area to the sensor at different designated areas of the motion detector surface.

It is also conceivable that one zone of the lens or lens array forming an upper end of the motion detector surface has a long focal length, thus focusing light from parts of the detection area which are far away from the location at which the security monitoring system is mounted. Simultaneously, another zone of the lens or lens array forming a lower end of the motion detector surface can have a short focal length, thus focusing light from parts of the detection area which are close to the location at which the security monitoring system is mounted. The different zones can be sharply defined by abrupt changes of the lens geometry or smoothly transition into each other, such that the lens or lens array offers a continuous or nearly continuous focal length gradient.

In one variant of the kit of parts, the different interchangeable covers or masks are adapted to cover one or more different zones of the lens or lens array when connected to the sensor unit. Hence, zones of the lens array with certain focal length or focal length ranges can be selectively shaded and/or deactivated, thus decreasing substantially the intensity of light reaching the sensor from areas for which detection and/or monitoring is not required.

Advantageously, at least one interchangeable cover is adapted to cover a zone of highest focal length of the lens or lens array when connected to the sensor unit. By connecting this cover to the sensor unit, a maximum detection range can be defined and/or decreased.

In a further advantageous embodiment, at least one interchangeable cover is adapted to cover a zone of lowest focal length of the lens or lens array when connected to the sensor unit. This allows to selectively define and/or decrease detectivity in areas located close to the system.

In a simple arrangement of the kit of parts, the multiple zones of the lens or lens array with different focal length are spaced at different distances from the image capture means, wherein the zone located closest to the image capture means has the highest focal length. This allows installing the system at an elevated position, for example at a wall, such that the image capture means and zone of highest focal length are located above the zones of lower focal length.

In a preferred variant of a kit of parts according to an aspect of the invention, the covers are shaped such that when connected to the sensor unit a free space is formed between the cover and a lens or lens array of motion detector. Thus, direct contact between the cover and the lens or lens array of the motion detector is avoided. This reduces the risk of damaging the lens or lens array during connection or removal of covers, in particular in systems in which the lens or lens array is soft and/or otherwise readily deformable or readily damaged.

In a further embodiment, the kit of parts comprises a lid or shade for reducing illumination of the image capture means and/or motion detector. This is particularly useful for outdoor applications to protect the image capture means and/or motion detector from direct sunlight. Such a lid or shade may also be useful in internal settings where incandescent lights or other sources of significant quantities of IR energy, such as ovens, furnaces, or other industrial plant, are present.

In another preferable variant, the kit of parts comprises an anti-tamper means configured to prevent removal of interchangeable covers connected to the sensor unit without triggering a tamper signal. It is conceivable that a villain or other unauthorized subject might want to remove the cover so that the detection area and/or detectivity of the motion detector is increased and the system is triggered by harmless movements, eventually provoking an operator to either learn to ignore alarm signals or to simply disable the system. An anti-tamper means triggering an electrical signal upon unauthorized removal of the cover, thereby inducing an alarm or starting the image capture means, can prevent such situations and increases the overall security for the operator.

According to an aspect of the invention there is also provided a sensor unit assembly, including one or more interchangeable covers connected to the sensor unit (10), assembled from a kit of parts according to the invention. The invention also provides a security monitoring installation comprising one or more such sensor unit assemblies.

The invention also provides a security monitoring installation comprising one or more passive infrared, PIR, motion sensors or cameras including a PIR sensor, having a plurality of different interchangeable covers by means of which the field of view of the PIR sensor can be adjusted to suit a particular installation location.

Further advantages and features will become apparent from the following description of the invention and from the appended figures, which show nonlimiting exemplary embodiments of the invention and in which:

Fig. 1 schematically shows a side view of a first embodiment of a sensor unit, for a security monitoring system assembly, particularly for indoor applications;

Fig. 2 schematically shows a side view of a second embodiment of a sensor unit, for a security monitoring system assembly, particularly for outdoor applications with a first cover connected to a sensor unit; Fig. 3 schematically shows a side view the sensor unit of Fig. 2 with a different second cover connected to the sensor unit in place of the first cover;

Fig. 4 schematically shows a side view the sensor unit of Fig. 2 with a third different cover connected to the security monitoring unit in place of the first cover;

Fig. 5 schematically shows a side elevation of a sensor unit, corresponding to a sensor unit as shown in any of Figures 2 to 4, with its battery cover and PIR sensor cover removed;

Fig. 6 schematically shows a frontal (or plan) view corresponding to Figure 5;

Fig. 7 schematically shows a front view of a first embodiment of a lens array of a motion detector, the lens array having multiple distinct zones of different focal lengths;

Fig. 8 schematically shows a PIR sensor cover arrangement configured to permit separate cover elements to be secured within a cover to obscure different parts of a lens array of the PIR sensor; and

Fig. 9 schematically shows a detection range diagram of a motion sensor unit comprising the lens array of Fig. 7;

Fig. 1 schematically shows a first embodiment of a sensor unit 10, for a security monitoring system particularly for indoor applications.

The sensor unit or node 10 comprises a security monitoring unit 16 with image capture means 18, such as a camera including an image sensor, configured to capture an image and/or a video of a monitored area and a motion detector 14. In the depicted embodiment, the motion detector 14 comprises a passive infrared (PIR) sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means 18. The PIR sensor includes a Fresnel lens array 20 behind which are located the sensing elements of the PIR sensor. As the skilled person will appreciate, other technologies may be used to provide motion sensing, for example microwave sensing, and these likewise may benefit from the application of the inventive idea of providing a plurality of interchangeable covers or masks to tune the area seen by the motion sensor or motion sensing arrangement. Therefore, unless the context clearly requires otherwise, the invention as described and claimed is also to be taken to embrace both optical, e.g. PIR motion sensing, and non-optical, e.g. microwave, motion sensing. However, for battery-powered sensor units the use of a passive sensor such as a PIR is preferred because the use of such sensors can contribute to an attractively long battery life for the sensor unit - which is typically very important for security monitoring systems.

Furthermore, the security monitoring unit 16 has a housing within which the image capture means 18 and the motion detector 14 are located. In the embodiment, the housing is an injection moulded plastic part with openings that allow radiation to reach the sensors of the image capture means 18 and the motion detector 14. More details of the structure of examples of the housing are described below with reference to Figures 5 and 6.

The sensor unit or node 10 furthermore comprises a plurality of interchangeable covers 12, which may also be considered to be masks, each configured to be connected to the security monitoring unit 16. All interchangeable covers 12 are differently configured so that they cover different parts of the lens array 20 when connected to the security monitoring unit 16. For example, different covers may be provided with differently positioned apertures and/or differently sized apertures, to expose different parts of the lens array, thereby providing different fields of view for the sensing elements of the motion sensor.

The interchangeable covers may be connected or secured to the security monitoring unit 16 by means of a connection element. Additionally, or alternatively, the covers may be secured to the security monitoring unit 16 by means of a removable housing element such as a battery compartment cover, as will be described further below. In an embodiment, the connection element may be a clip connector, in particular a snap-fit connector.

It is conceivable, that the housing of the security monitoring unit 16 comprises a first connection member of the connection element, in particular a notch being used as snap-in area. Each of the interchangeable covers 12 may comprise a second connection member complementary to the first connection member. This can for example be a protrusion and/or cantilever adapted to snap in the above-mentioned notch when the respective cover 12 is pressed against the housing of the security monitoring unit 16. The connection can be permanent, so that once fitted the cover cannot readily be removed subsequently, but is preferable removable so that, for example, various different covers can be tried to suit a particular installation, and the optimum one chosen.

Of course, a snap-in (or snap-fit) connection is only one example of a suitable connection element and not limiting the scope of the invention. Other fastening means, such as magnetic or screw connections can be applied. In the case that the device 10 includes a removable battery compartment cover, it is preferred that at least some of the fastening means are concealed behind the battery compartment cover when the device is fully assembled - thereby improving retention security for the motion sensor mask/cover.

In the example depicted in Fig. 1 , a cover 12 for indoor surveillance is selected and connected to the security monitoring unit 16. The cover 12 has an opening, aperture or cut-away through which incoming radiation can reach the motion detector through the lens array 20. In the Fig. 1 example, the opening or aperture in the mask is so sized and located that the entire lens array surface 20 is exposed. Consequently, the motion detector 14 is not shaded by the selected cover 12 and the sensor unit or node 10 works with the full detection area intrinsic to the motion detector 14. In this case, the cover 12 may mask an otherwise visible first connection element of the housing, and/or other structural features resulting in improved appearance of the sensor unit or node 10. Alternatively, it is possible that no cover is connected to the security monitoring unit 16 in order to exploit the full detection range offered by the motion detector 14.

In this Figure 1 example, the security monitoring unit 16 is a mains powered device, the power supply cable 8 being visible in the bottom left of the Figure. It is of course possible to have a battery-powered indoor surveillance camera, and equally it is possible to install an indoor surveillance camera in an internal location where it may be useful to mask A second embodiment of a sensor unit or node 10 is shown in the Figures 2 to 4. The second embodiment largely corresponds to the first embodiment, so that only the differences will be discussed below. Identical and functionally identical parts are provided with the same reference symbols.

In each of the Figures 2 to 4 a different cover 12 is selected and connected to the security monitoring unit 16. The different covers 12 shade different parts of the lens array 20, thereby defining different detection areas specific for the intended application.

In the described embodiment, the covers 12 are shaped such that in an assembled state a free space between them and the lens array surface 20 is formed. The free space can be for example a narrow gap (e.g., an air gap) between the cover 12 and the lens array surface 20 to avoid direct contact albeit ensuring proper masking.

Figure 5 schematically shows a side elevation of a sensor unit, corresponding to a sensor unit 16 as shown in any of Figures 2 to 4, with its battery compartment cover 11 and motion sensor cover 12 removed. The unit 16 has an internal compartment 23 (not shown) to receive a battery or battery pack 13, the battery preferably being rechargeable although a battery pack may be provided to enable the use of, for example, a plurality of standard alkaline cells. Provision may also be made to locate a power supply within the battery compartment and for a power supply lead to enter and extend from the battery compartment so that the power supply may be connected to an external source of power such as a mains electricity supply (as in the example shown in Figure 1).

The attachment of the battery compartment cover 11 (which may also be referred to as a lid, closure, closure element, or closure member) to the housing of the unit 16 is preferably provided with a tamper detection arrangement (also known as anti-tamper), so that once the unit is powered and registered within a security monitoring installation removal or attempted removal of the battery compartment cover causes the unit 16 to transmit a tamper signal to a control unit of the security monitoring installation which can then transmit an alarm event signal to a central monitoring station and/or cause the local sounding of a klaxon or other alarm indicator. In an example, an anti-tamper arrangement of the battery compartment cover may be used to provide an anti-tamper feature for the motion sensor mask 12 by requiring that removal of an installed mask 12 requires prior removal or release of the battery compartment cover 11.

An example of such an integrated anti-tamper arrangement is shown schematically in Figure 5. Here, the motion detector masks 12 are so configured that, once installed and the unit assembled with the battery compartment cover 11 in place, the cover 12 cannot be removed without removing the battery compartment cover 11. In the example shown a latching arrangement is provided to secure the battery compartment cover 11 releasably to the housing of the unit 16. Projections in the form of tongues or hooks 17 extend from the open side of the battery compartment cover 11 , and these engage with corresponding features (not shown) provided in the housing of the unit 16. A battery compartment cover release button 15 is provided to release the latching arrangement enabling the removal of the battery compartment cover 11. Preferably, the latching arrangement is so configured that the battery compartment cover can be pushed into place, displacing the corresponding features in the housing which then snap back into place when the battery compartment cover 11 is in place, without requiring that the release button 15 be held depressed.

The sensor cover 12 is provided with protrusions, in the form of flanges, tongues, or fingers, that extend from the open end of the sensor cover 12, and these cooperate with the battery compartment cover to lock the sensor cover in place once it and the battery compartment cover have been assembled to the housing. Preferably a relevant protrusion is formed on each side of the sensor cover 12 (so that a protrusion is provided for each of the two sides of the battery compartment (at least one either side of the battery). Each protrusion is also preferably formed with a hooked end or with an enlarged end, or some other suitable configuration, to better secure the sensor cover in place once the battery compartment cover is in place.

The sensor cover 12 and housing are also configured to reduce the risk that the sensor cover 12 can be prised away from the housing. To address this issue the sensor cover and housing preferably engage with each other over a large extent of their cooperating surfaces. In the example shown in Figure 5, the housing is provided with an outwardly facing groove or channel 21 on each side, and the motion sensor covers 12 are each provided with one or more corresponding male features, for example in the form of tongues or flanges, on respective inner edges. The motion sensor cover being mountable to and removable from the housing by engaging the male members with the open slots and then causing a relative sliding movement between the motion sensor cover 12 and the housing. In other words, the motion sensor cover 12 slides onto the housing, and into place on the sensor unit 10, from an end of the sensor unit 10. The motion sensor cover 12 can therefore be considered to be an end cap of the sensor unit (or at least of its housing).

When a motion sensor cover 12 is to be installed either for the first time or to replace a previously installed cover 12, the battery compartment cover is lifted off after/while actuating the cover release button 15. If a cover 12 is already installed this is removed, for example by sliding it laterally away from the battery compartment (i.e. linearly leftwards in the arrangement shown in Figure 5). The motion sensor cover that is to be installed is then slid on (from left to right in Figure 5) by engaging the male members with the respective open slots 21 and then pushing the cover 12 into place (up to the limit of its movement). Preferably, the slots 21 on either side of the housing are sections or segments of a single continuous slot that extends around the end of the housing intermediate the two slot sections, and one or more corresponding male protrusions is/are formed on a mating inner surface of the sensor mask 12. In this way, an installed sensor mask may be more firmly and securely retained.

Figure 6 schematically shows a frontal (or plan) view corresponding to Figure 5. The single continuous peripheral groove 21 mentioned as a preferred configuration is shown (as a dashed line) as including two opposed lateral segments 2T and 21”, with a portion 2T” connecting the segments to make a continuous peripheral groove. The battery compartment 23 can also be seen, and within this are shown electrical terminals 25 for connection to corresponding terminals on the battery or battery pack 13. Also shown are apertures 27 to receive the latch elements 17 of the battery compartment cover 11. The anti-tamper sensing arrangement for the battery cover (and hence also for the sensor cover 12) is provided within the housing behind (when viewed in Figure 6) the battery compartment. For example, one or more of the latch elements 17, or some other protrusion of the battery compartment cover 11 , may be configured to make (or optionally break) a circuit in the installed position, the circuit status changing -and the change being detectable - when the battery compartment cover is displaced.

Fig. 7 shows a detailed illustration of the motion detector surface 20. The motion detector 14 comprises a passive infrared (PIR) sensor and a Fresnel lens array 22 located at the motion detector surface 20 for focusing incoming infrared radiation onto the sensor.

The lens array 22 comprises multiple zones 24 of different focal length. Hence, light incoming from different regions within the detection area being differently spaced apart from the motion detector 14, i.e. incoming with different incident angles, is focused by different zones 24 of the lens array 22 onto the PIR sensor.

In the described example, there are three zones 24 of different focal length being spaced at different distances from the image capture means 18. In particular, the zone 24 of highest focal length, which is the upper zone 24 depicted in Fig. 7, is located closest to the image capture means 18.

The zone 24 located in the middle of Fig. 7 has intermediate focal length and the zone 24 located at the lower end of Fig. 7 has the lowest focal length.

In Fig. 2 a cover 12 is selected and connected to the security monitoring unit 16 which does not block any incoming radiation from reaching the sensor. Thus, movement of infrared emissive or reflective objects can be detected within the whole detection range intrinsic to the uncovered motion detector 14.

In Fig. 3 a cover 12 is selected and connected that only covers the upper zone 24 of the lens array 22. Hence, the intensity of radiation incoming from locations within the detection area further from the system 10 is reduced. Consequently, the maximum detection range is decreased to a desired value.

In Fig. 4 a cover 12 is selected and connected that covers both the upper and middle zones 24 of the lens array 22. Hence, the detection range is further reduced.

It is also conceivable that only one cover 12 adapted to cover the zone 24 of lowest focal length is selected and connected to the security monitoring unit 16 to prevent activations of the sensor unit or node 10 by moving subjects in close proximity, in particular in spaces underneath of the installation and/or mounting position. Furthermore, embodiments may be so designed that two covers 12 can be simultaneously connected to the security monitoring unit 16, for example one covering the zone 24 of highest focal length and one covering the zone 24 of lowest focal length, such that only the zone 24 of intermediate focal length remains uncovered. An example of such a design is shown schematically in Figure 8. Here, a PIR sensor cover arrangement 12 is configured to permit separate cover elements to be secured within a cover to obscure different parts of a lens array of the PIR sensor. The cover 12 has an aperture 80 that optionally is so configured that when installed it exposes the full operating area of the PIR sensor (or, differently expressed exposes the full operating area of a lens array of the PIR sensor). The cover 12 is arranged to receive and retain separate cover elements 82 and 84. Cover element 82 fits within a slot or socket 86 on an upper part of the inner side of the cover 12. Cover element 84 likewise fits within a slot or socket 88 on a lower part of the inner side of the cover 12. The cover elements 82 and 84 may be configured to be interchangeable - for example, they may be identical. However, the configuration of the cover and the lens array of the PIR detector may be such that cover elements to fit within the upper socket 86 must be differently configured to cover elements that fit within lower socket 88, and vice versa.

Each of the upper and lower cover elements 82 and 84 may be provided in different sizes - that is covering more or less of the motion detector or its lens or lens array (if present), to enable different degrees of shading. Preferably, each cover element is clearly marked (preferably using an integral indication, for example moulded in to the cover element when it is injection moulded) to indicate the degree of shading - for example by indicating a range of distances obscured.

Preferably, the cover elements and their sockets are configured to achieve a snap fit, so that once installed a cover element is retained very securely within the cover. Preferably, however, the snap fit is releasable when the cover 12 is removed from the device 10, so that an installed cover element can be removed optionally to be replaced with another cover element.

Although the embodiments illustrated in Figure 8 are shown as including sockets 86 and 88 to receive the cover elements 82 and 84, it will be appreciated that a kinematically equivalent arrangement, in which the cover elements are each provided with a socket (more generally female receptacle) to receive a respective protrusion (more generally male member) of the cover 12 could be used instead.

Also, both with configurations of the kind shown in Figure 8 - in which a cover member 12 is configured to receive interchangeable shutters or masks 82 or 84, and with configurations as shown in Figures 2 to 4 - in which each cover member is differently configured (for example by defining a differently dimensioned aperture to mask different portions of the PIR detector or a lens array of a PIR detector), it is possible to provide arrangements in which the lateral extent of the “view” seen by the PI R sensor or by a lens array of a PI R sensor is similarly differently maskable to restrict the lateral extent of the operating field of a PIR sensor. Such an arrangement may, for example be helpful where a sensor device 10 is to be mounted in a position where a neighbouring property to one to be monitored is also in view. In such a situation one might typically endeavour to mount the sensor device 10 on an angled mount so that only the property to be monitored is within view of an image capture means of the sensor device and within view of the PIR sensor - but sometimes this is not possible. In such a situation, embodiments of the present invention which provide a way to restrict the lateral extent of the “view” of the PIR sensor can be useful.

An illustrative example of the expected detection area, respectively detection range of the sensor unit or node 10 with different covers 12 being attached to the monitoring unit 16 is provided in Fig.9. In this example, the sensor unit or node 10 is mounted at an installation height of 2.2 metres with a mounting angle of 0 degrees. Clearly, the ranges can be expected to increase if the installation height is increased, and reduced if the installation height is reduced. Similarly, tilting the sensor forwards away from the vertical will tend to reduce the detection ranges, while tilting the sensor backwards away from the vertical will tend to increase the detection ranges.

In case only the zone 24 of longest focal length is covered, no activation of the motion detector 14 is expected for objects moving at a distance greater than 9.8 metres. This distance is indicated with the solid line 28.

In case the zone 24 of highest and intermediate focal lengths are both covered, no signal is expected for objects moving at a distance greater than 4.6 metres. This distance is indicated with the second solid line 30. For indoor applications, the detection range can be smaller, for example due to reduced ambient stray light, which also contributes to the total amount of infrared light reaching the sensor.

It is conceivable that the indoor detection range is 7.0 metres with the zone 24 of highest focal length being covered, as indicated by the first dashed line 32, and only 3.0 metres if the zones 24 of highest and intermediate focal length are both covered, as indicated by the second dashed line 34.

Unlike in the first embodiment of the security motion system assembly 10 for indoor applications, the second embodiment for outdoor applications as shown in Fig. 2 to Fig. 4 has first and second sunshades or lids 26 to protect respectively the image capture means 18 and the motion detector 14 from direct sunlight. Direct sunlight can result in overexposure and saturation of optoelectronic sensors used in cameras and motion detectors and may even reduce their lifetime. Furthermore, sunlight has a significant share of infrared radiation. Hence, direct solar illumination and/or moving clouds could result in triggering of the PIR sensor. These effects can be avoided with the sunshades or lids 26. The use of a “sunshade” may also be appropriate in some internal installations - particular those where high-power incandescent lights or other powerful emitters of infrared radiation (such as infrared heaters) are mounted at a level above the installation level of a sensor unit or node 10 according to an aspect of the present invention.

In the illustrated embodiments, the motion detector sunshades 26 are integral with the covers 12 to avoid competition of assembly space, although this is of course optional.

Furthermore, the embodiments the sensor unit or node 10 may further comprise anti-tamper means configured to prevent removal of interchangeable covers 12 connected to the security monitoring unit 16 without triggering a tamper signal. The anti-tamper means can for example comprise an electrical contact formed between the security monitoring unit 16 and the attached cover 12. In case the cover 12 is removed, an electrical signal is triggered that can starting an alarm and/or the image capture means 18.

Alternatively, covers 12 can be fixed to the security motion unit 16 by magnetic connectors. Particularly in this configuration, the anti-tamper means can be a sensor stimulated by changes in a magnetic field resulting from unauthorized removal of the cover 12.

Of course, also motion detector types and designs other than described above can be applied, such as for example microwave.

The above-described sensor unit or node assemblies 10 in their respective assembly states as shown in the Figures 1 to 4 are installed using a method according to the invention, which will be described in the following.

In a first step of the method, a suitable cover 12 is selected from a plurality of different interchangeable covers 12 depending on a desired detection area and/or detection range of the sensor unit or node 10. As described above, the different interchangeable covers 12 are adapted to each cover different zones 24 of the motion detector surface 20 of the security monitoring unit 16.

In a second step, the selected interchangeable cover 12 is connected to the security monitoring unit 16, for example by means of one or more connection elements - or using an arrangement such as that illustrated schematically in Figures 5 and 6, where the cover or mask 12 is retained in position, at least in part, by a battery compartment cover. In some of the described embodiments, this is achieved by gently pressing the cover 12 against the security monitoring unit 16, such that the complementary connection members located at the cover 12 and the security monitoring unit 16 connect to each other, in particular snapping into each other. In other described embodiments the cover or mask 12 may be slid into place, and then retained by engaging a battery compartment lid or closure- although there may in addition be a snap fit arrangement whose operation is such as to provide clear tactile or audible feedback of the engagement of corresponding parts of the cover/mask 12 and for example the housing of the device.

It is conceivable that a user (or, more typically, an installation engineer) performs the second step, advantageously the first and second step, during installation of the sensor unit or node 10 at a building structure. This reduces the overall effort for setting up the sensor unit or node 10 because installation at a building structure typically anyhow requires a user interaction. Additional timeconsuming system calibration is not required. It is contemplated that, for example, a kit of parts according to an aspect of the invention would be supplied with a set of a plurality of interchangeable covers/masks, each having a clearly visible indicator or legend (e.g. A, B, C, D, E, F), together with one or more charts or tables that indicate the effective range (maximum, minimum) of the motion sensor - when the motion sensor is mounted (vertically) at specified heights - e.g. 1.8, 1.9. 20. 2.1. 2.2. 2.3 metres, etc. In addition, the sensor unit (or kit of parts) may also be supplied with adapters or mounting elements that permit the fixing of the sensor unit at a known angle from the vertical (typically enabling the sensor unit to be angled downwards at a known offset from the vertical (e.g. 5, 10, 15, 20 degrees) - and suitable charts or tables provided showing the effective range of the motion sensor resulting from the use of the different masks (e.g. A, B, C, D, E, F) with the different angled adapters. IN this way, the installation engineer can readily determine what combination of elements to combine to achieve the motion desired range for any particular installation.

Especially in indoor applications, where the detection space is typically confined by walls, it is also possible to select zero covers 12 or a cover 12 which does not shade the motion detector surface 20.

In case confinement of the detection space in not sufficiently provided by the surrounding environment itself, selection and connection of a suitable cover 12 is applied to precisely define the detection area, thus avoiding undesired triggering events.

As shown in the Figures 2 to 4, it is possible to select and connect a single cover 12 for masking one or multiple zones 24 of the motion detector surface 20 or lens array 22.

However, dependent on the application, it can be beneficial to install two covers 12, in particular when different areas of the motion detector surface 20 spaced apart from each other are intended to be covered, for example using a configuration such as that illustrated in Figure 8.

Embodiments of the motion sensor node so far described typically include a lens array, such as a Fresnel lens array, to focus infra-red radiation from different locations (including locations at different distances from the sensor node) onto one or more sensing elements, and this is the most usual arrangement. It is however possible to produce a motion sensor node which does not rely on the use of a lens array, and the present invention is equally applicable to such arrangements albeit that they are likely to be used less commonly. In particular, if the motion sensor is based on microwaves, there may be no lens or lens array.

Claims

- 25 - Claims

1. A method of installing a sensor unit for a security monitoring system comprising the steps of selecting dependent on a desired detection area and/or detection range of the sensor unit (10) an interchangeable cover (12) from a plurality of different interchangeable covers (12), wherein the different interchangeable covers (12) are adapted to restrict differently the field of view of a motion detector (14) of the sensor unit (10); and connecting the selected interchangeable cover (12) to the sensor unit (10).

2. A method according to claim 1 , wherein connecting the selected interchangeable cover (12) to the sensor unit is performed while a battery compartment cover of the sensor unit is removed, the method further comprising retaining the interchangeable cover (12) to the sensor unit (10) by securing a battery compartment cover to the sensor unit (10).

3. A method according to claim 2 wherein the securing of the battery compartment cover to the sensor unit (10) engages an anti-tamper arrangement of the sensor unit, the anti-tamper arrangement also providing anti-tamper protection for the interchangeable cover (12).

4. A method according to any one of the preceding claims, further comprising configuring an interchangeable cover (12) by connecting one or more shutter elements (82, 84) to an inner surface of the interchangeable cover (12) prior to connecting the selected interchangeable cover (12) to the sensor unit (10).

5. A method according to any one of the preceding claims, wherein the different interchangeable covers (12) are so configured that they only restrict the maximum and/or minimum range of the field of view of the motion detector (14) of the sensor unit (10).

6. A method according to any one of claims 1 to 4, wherein different interchangeable covers (12) are so configured that they differently restrict the lateral field of view of the motion detector (14) of the sensor unit (10).

7. A method according to any one of the preceding claims, wherein an installer performs at least the step of connecting the selected interchangeable cover or covers (12) during installation of the sensor unit (10) at a building structure.

8. A method according to any one of the preceding claims, wherein connecting the selected interchangeable cover (12) to the sensor unit (10) is performed by means of one or more connection elements, each comprising a first connection member positioned at the sensor unit (10) and a second complementary connection member positioned at the interchangeable cover (12) to be connected.

9. A method of tuning a passive infrared, PIR, motion sensor to suit a particular installation location, the PIR including a lens or lens array to focus light onto the sensing arrangement of the sensor, the method comprising selecting a cover from a collection of a plurality of covers, each cover having a different configuration to expose a different portion of the lens or lens array, the selected cover having an appropriately configured aperture to expose only a selected portion of the lens or lens array to restrict the field of view of the sensor to suit the particular installation location.

10. A kit of parts including a sensor unit assembly, in particular for performing the method of any of the preceding claims, comprising a sensor unit (10) with image capture means (18) configured to capture an image and/or a video of a monitored area and a motion detector (14), in particular a passive infrared, PIR, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means (18); and a plurality of interchangeable covers (12), each configured to be connected to the sensor unit (10), wherein different interchangeable covers (12) are configured to restrict differently the field of view of the motion detector (14) when connected to the sensor unit (16).

11 . The kit of parts of claim 10, wherein the different interchangeable covers (12) are configured to restrict differently the field of view of a motion detector by covering different parts of a lens or lens array of the motion detector (14) when connected to the sensor unit (16).

12. A kit of parts according to claim 10 or claim 11 , wherein the sensor unit includes a battery compartment (23) having a battery compartment closure (11), and the interchangeable covers (12) are so configured that the covers can only be mounted to or removed from the sensor unit (10) while the battery compartment closure (11) of the sensor unit is in an open position, the interchangeable covers (12) being securable to the sensor unit (10) by securing the battery compartment closure (11) to the sensor unit (10).

13. A kit of parts according to claim 12 wherein the sensor unit (10) includes an anti-tamper arrangement for the battery compartment closure (11), the antitamper arrangement also providing anti-tamper protection for an interchangeable cover (12).

14. A kit of parts according to claim 12 or claim 13, wherein an interchangeable cover (12) of the plurality of covers is configured to receive one or more shutter elements (82, 84) on an inner surface of the interchangeable cover (12) prior to connecting the interchangeable cover (12) to the sensor unit (10).

15. A kit of parts according to claim 14, wherein the interchangeable cover (12) is configured to couple to the or each shutter element through a snap fit interface arrangement.

16. A kit of parts according to any one of claims 11 to 15, characterized in that the motion detector (14) comprises a lens array (22), in particular of a Fresnel type.

17. A kit of parts according to claim 16, characterized in that the lens array (22) comprises multiple zones (24) of different focal length.

18. A kit of parts according to claims 17, characterized in that different interchangeable covers (12) are adapted to cover one or more different zones (24) of the lens array (22) when connected to the security monitoring unit (16).

19. A kit of parts according to claim 17 or 18, characterized in that at least one interchangeable cover (12) is adapted to cover a zone (24) of longest focal - 28 - length of the lens array (22) when connected to the security monitoring unit (16).

20. A kit of parts according to any of the claims 17 to 19, characterized in that at least one interchangeable cover (12) is adapted to cover a zone (24) of shortest focal length of the lens array (22) when connected to the security monitoring unit (16).

21 . A kit of parts according to any of the claims 17 to 20, characterized in that the multiple zones (24) of the lens array (22) are spaced at different distances from the image capture means (18), wherein the zone (24) located closest to the image capture means (18) has the longest focal length.

22. A kit of parts according to any of the claims 11 to 21 , characterized in that the covers (12) are shaped such that when connected to the security monitoring unit (16) a free space is formed between the cover (12) and the lens or lens array (20).

23. A kit of parts according to any of the claims 10 to 22 further comprising a sunshade (26) for reducing unwanted illumination of the image capture means (18) and/or motion detector (14).

24. A kit of parts according to any of the claims 10 to 23 further comprising an anti-tamper arrangement configured to prevent removal of interchangeable covers (12) connected to the security monitoring unit (16) without triggering a tamper signal.

25. A sensor unit assembly, including an interchangeable cover (12) connected to the sensor unit (10), assembled from a kit of parts according to any one of claims 10 to 24.

26. A battery-powered sensor unit assembly, comprising a sensor unit (10) with image capture means (18) configured to capture an image and/or a video of a monitored area and a motion detector (14), in particular a passive infrared, PIR, sensor, configured to detect motion in a detection area and to provide dependent on the detection a signal to activate the image capture means (18), the sensor unit having a housing including a battery compartment to receive - 29 - one or more batteries to power the sensor unit, the battery compartment including a closure element for closing the battery compartment; and a removable masking element (12) connected to the sensor unit (10) and covering part of a lens of the motion detector (14); wherein the removable masking element (12) is secured to the sensor unit assembly by the closure element of the battery compartment, the removable masking element (12) only being removable from the sensor unit assembly once the closure element of the battery compartment is opened/released.

27. A battery-powered sensor unit assembly as claimed in claim 26, wherein the battery compartment closure is provided with an anti-tamper arrangement which is triggered by removal of the battery compartment closure, the antitamper arrangement also being triggered by removal of the removable masking element.