AU2012261766B2 - A sensor - Google Patents

Abstract

A sensor for sensing electromagnetic radiation from a viewing area is described. The sensor incorporates a housing having an aperture for receiving electromagnetic radiation from the viewing area and a sensing region located within the housing where the sensing region sensitive to electromagnetic radiation and operable to provide an electrical signal once a predetermined threshold condition is met. The sensor also includes a focusing element forming part of the sensor to direct electromagnetic radiation from the viewing area onto the sensing region, wherein the focusing characteristics of the focusing element may be modified to modify the viewing area of the sensor. 110 126 211 310 212 131 120' Figure 2a 301A110 126 310 212 131 120' Figure 2b

Description

1 A SENSOR PRIORITY DOCUMENTS [0001] The present application claims priority from Australian Provisional Patent Application No. 2011905218 entitled "A SENSOR" and filed on 14 December 2011. The content of this application is hereby incorporated by reference in its entirety. TECHNICAL FIELD [0002] The present invention relates to sensors for sensing electromagnetic radiation. In a particular form, the present invention relates to a motion sensor for sensing movement of an object in a viewing area of the sensor based on detecting infra-red (IR) radiation. BACKGROUND [0003] Motion sensors are used primarily to monitor an area by detecting the presence of an object within a viewing area of the sensor. This may be in the context of securing an area from an intruder or to trigger the operation of a further device such as the case where a vehicle enters a viewing area and the operation of a garage door is then actuated to allow exit or entry from a building. There are many types of electromagnetic sensors ranging from those based on analysing changes in the visual characteristics of an area, to those that detect changes in the ambient temperature of the viewing area using a passive infra-red (PIR) detector to other examples that use microwave transceivers which rely on detecting the reflection of microwaves emitted from the transceiver. [0004] Typically, a sensor will comprise a housing having an aperture through which electromagnetic radiation from the viewing area enters and a sensing region with associated electronic circuitry mounted within the housing. These housings are often substantially hermetically sealed to both increase reliability where the sensor may be subject to the outdoor environment, and/or to prevent tampering. In order to maximise the viewing area, the sensor will often incorporate a means for focusing electromagnetic radiation that functions to concentrate or focus electromagnetic radiation onto the sensing region of the sensor. The combination of the sensitivity of the sensing region and the optical characteristics of the focusing member then define the effective viewing area of the sensor. [0005] Referring now to Figure 1, there is shown an example of an IR based motion sensor 100 of the type that would typically be mounted on a wall or the like that operates by detecting changes in the ambient temperature. Motion sensor 100 comprises a housing 120 having a forward facing viewing aperture or window 110. Located in the housing is a PIR detector 130 having a sensing region 131 and associated electronic control circuitry 140 mounted in housing 120 responsible for both powering and 2 associated electronic control circuitry 140 mounted in housing 120 responsible for both powering and processing the output from PIR detector 130. Typically, an electrical signal will be provided by electronic control circuit 140 based on the output of sensing region 131 once a threshold condition is met. This electrical signal may be relayed by cabling 150 which in this example also functions to power motion sensor 100. [0006] To improve the viewing range of motion sensor 100, window 110 may incorporate a focusing element 111 that functions to focus IR radiation incident on window 110 onto sensing region 131 of PIR detector 130 which is located at the centre of window 110 as viewed from the front. The use of a focusing element 111 is generally employed to broaden or change the acceptance angle of the motion sensor 100 as compared to a sensor without a focusing element. [0007] To ensure a compact configuration, the focusing element 111, as is the case here, is implemented as a substantially planar Fresnel lens element formed from a material such as plastic. In other examples, the focusing element 111 may comprise an array of Fresnel lens elements. The focusing element 111 design is dependent on the desired viewing area of the sensor. In the case of where focusing element 111 consists of an array of Fresnel lens elements, rows of lens elements or even individual elements may be designed to cover specific portions or fields of view of the viewing area. In this way, the coverage of the viewing area may be tailored according to requirements. [0008] One disadvantage of the motion sensors incorporating such a focusing arrangement is that the viewing area cannot be easily modified. Accordingly, if the desired viewing area changes in practice from the originally specified viewing area of the motion sensor then a new sensor will have to be sourced. In some instances, there may also be a requirement to be able to change the viewing area of a motion sensor on a regular basis. There is therefore a need for a motion sensor whose viewing area may be readily modified. SUMMARY [0009] In a first aspect, the present invention accordingly provides a sensor for sensing electromagnetic radiation from a viewing area including: a housing having an aperture for receiving electromagnetic radiation from the viewing area; a sensing region located within the housing, the sensing region sensitive to electromagnetic radiation and operable to provide an electrical signal once a predetermined threshold condition is met; a focusing element forming part of the sensor to direct electromagnetic radiation from the viewing area onto the sensing region, the focusing element formed of a flexible material wherein the focusing characteristics of the focusing element may be modified to modify the viewing area of the sensor; and 3 flexing means to modify the focusing characteristics of the focusing element by flexing or bending the focusing element without obscuring a central region of the focusing element. [0010] In another form, the flexing means includes moveable abutment means that abut at least one edge of the focusing element to apply a flexing force. [0011] In another form, the moveable abutment means includes an adjustable screw that abuts a side edge portion of the focusing element. [0012] In another form, the moveable abutment means is manually actuated. [0013] In another form, the moveable abutment means is mechanically actuated. [0014] In another form, the flexing means displaces the edges of the focusing element with respect to the central region of the focusing element which is fixed. [0015] In another form, the flexing means displaces a central region of the focusing element with respect to fixed edges of the focusing element. [0016] In another form, the flexing means includes pressure modification means to change the internal pressure of the housing to cause the focusing element to flex or bend. [0017] In another form, the pressure modification means includes an electronically controlled micro pump located in the housing. [0018] In another form, the focusing element includes a resilient frame or surround portion. [0019] In another form, the viewing area of the sensor is modified by modifying the acceptance angle of the sensor. [0020] In another form, the viewing area of the sensor is modified by modifying the range of the sensor. [0021] In another form, the sensor is operative to sense electromagnetic radiation in the infra-red range. [0022] In another form, the sensor is a passive infra-red (PIR) motion based sensor. [0023] In another form, the focusing element is a Fresnel lens based element. [0024] In a second aspect, the present invention accordingly provides method for modifying a viewing area of a sensor for sensing electromagnetic radiation, the sensor having a housing including an aperture to receive electromagnetic radiation from the viewing area, the method including: 4 focusing by a flexible focusing element the electromagnetic radiation from the viewing area onto a sensing region located in the housing, the sensing region operative to provide an electrical signal once a predetermined threshold condition is met; modifying the focusing characteristics of the focusing element by flexing or bending the focusing element to modify the viewing area focused by the focusing element onto the sensor without obscuring a central region of the focusing element. [0025] In another form, the sensor is operative to sense electromagnetic operation in the infra-red range. [0026] In another form, the sensor is a passive infra-red (PIR) motion based sensor. [0027] In another form, modifying the viewing area includes modifying the acceptance angle of the sensor. [0028] In another form, the viewing area includes modifying the range of the sensor. BRIEF DESCRIPTION OF DRAWINGS [0029] Illustrative embodiments of the present invention will be discussed with reference to the accompanying drawings wherein: [0030] FIGURE 1 is a figurative perspective view of a prior art motion sensor; [0031] FIGURES 2a and 2b are top sectional views of a sensor in accordance with an illustrative embodiment of the present invention depicting the flexing or bending of the focusing element to change the focusing characteristics of the sensor; [0032] FIGURE 3 is a detailed sectional view of the flexing means illustrated in Figures 2a and 2b operative to flex or bend the focusing element; [0033] FIGURE 4 is a front perspective view of a focusing element incorporating a frame portion; [0034] FIGURES 5a and 5b are schematic views depicting the change in viewing area as a result of changing the focusing characteristics of the sensor as depicted in Figures 2a and 2b; [0035] FIGURES 6a, 6b and 6c are top figurative views of different flexing arrangements in accordance with further illustrative embodiments of the present invention; and [0036] FIGURES 7a and 7b are top sectional views of a sensor in accordance with another illustrative embodiment of the present invention. [0037] In the following description, like reference characters designate like or corresponding parts throughout the figures.

5 DESCRIPTION OF EMBODIMENTS [0038] For ease of description, the sensors embodying the present invention are described below in their usual assembled position as shown in the accompanying drawings and terms such as front, rear, upper, lower, horizontal, longitudinal etc., may be used with reference to this usual position. However, the sensors may be manufactured, transported, sold, or used in orientations other than that described and shown herein. [0039] Referring now to Figures 2a and 2b, there are shown top sectional views of a sensor 200 according to an illustrative embodiment. Sensor 200 in this illustrative embodiment shares a number of common features with sensor 100 including a housing 120 having a forward facing viewing aperture or window 110 and a PIR detector 130 having a sensing region 131 and associated electronic control circuitry mounted 140 in housing 120. However, focusing element 211 is formed of a flexible material which in this embodiment is a flexible plastic and mounted within housing 120 to allow the focusing characteristics of focusing element 211 to be modified to modify the viewing area of sensor 200. [0040] In this illustrative embodiment, sensor 200 includes flexing means 300 in the form of an arrangement that applies a flexing force to one or both sides of flexible focusing element 211 substantially in the plane of the focusing element 211. The application of this flexing force causes flexing or bending of focusing element 211 thereby increasing or decreasing its curvature (as best seen Figure 2b). Flexing means 300 in this illustrative embodiment includes opposed moveable abutment means in the form of adjustment screws 310 that each abuts a side edge portion 212 of focusing element 211. [0041] Referring now also to Figure 3, each adjustment screw 310 includes a head portion 311 that is recessed within a countersunk region 121 of housing 120 and a screw threaded shank 312 that extends through a complementary screw threaded bore 122 in housing 120 and terminates in a receiving region 313 that receives a side edge portion 212 of flexible focusing element 211. As can be seen by reference to Figure 2b, by screwing adjustment screw 310 into countersunk region 121 a flexing force is applied to the edge of focusing element 211 that causes focusing element 211 to flex or bend outwardly thereby generally increasing the curvature of the focusing element. In this illustrative embodiment, the portion of housing 120 that surrounds focusing element 211 further includes top and bottom arcuate cut-out portions 126 that define the outward limit of movement of focusing element 211. [0042] To reduce this induced curvature, adjustment screw 310 may be unscrewed causing receiving region 313 to move outwardly and reduce the flexing force applied to side edge portions 212 of focusing element 211. As would be appreciated by those of ordinary skill in the art, one edge of focusing element 211 may be fixed to housing 120 and the flexing force applied to only one side edge portion 212. Furthermore, while in this illustrative embodiment a flexing force has been applied to one or more of the side edges of focusing element 211 depending on requirements one or more of the top and/or bottom 6 edges may be so manipulated. In another illustrative embodiment, a transparent window not having any focusing characteristics may be mounted behind focusing element 211 and covering window 110 to maintain the sealing characteristics of housing 120 if desired. [0043] While in the illustrative embodiment depicted in Figures 2a and 2b, adjustment screw 310 is manually actuated, in another illustrative embodiment adjustment screw 310 may be mechanically actuated by an electric motor (not shown) such as a stepper motor which functions to rotate adjustment screw 310 in either direction as required. The stepper motor in this illustrative embodiment would be both powered and controlled by associated controller circuitry forming part of the electronic control circuitry 140 mounted in the housing 120. In this embodiment, an external electrical switch or actuator may be employed to operate stepper motor and in turn modify the viewing area of sensor 200. [0044] Referring now to Figure 4, there is shown a focusing element 211 that includes a resilient frame or surround portion 213 that functions to improve the flexing or bending characteristics of focusing element 211. Frame portion 213 while still flexible is comparatively rigid compared to the central portion 214 of focusing element 211. This resistance to the flexing or bending force applied by the flexing means 300 is able to provide a greater level control over the curvature of focusing element 211 should this be required. [0045] Referring now to Figures 5a and 5b, there are shown schematic views of sensor 200 depicting the associated viewing areas 180, 180' corresponding to the configurations depicted in Figures 2a and 2b. As shown in Figure 5a, sensor 200 in its original configuration corresponding to Figure 2A has a viewing area defined in this illustrative embodiment by acceptance angle a and range d. It is a feature of infra-red motion sensors of the type referred to in these illustrative embodiments that a decrease in the acceptance angle a results in an increase of range d of the viewing area. As shown in Figure 5b, increasing the curvature of focusing element 211 results in sensor 200' having a decreased acceptance angle a' but an increased range d' which is sufficient to now encompass object 290 within modified viewing area 180'. As would be appreciated by those of ordinary skill in the art, other types of sensors may have a different relationship between the degree of flexing of focusing element and the resulting change in the viewing area as a result of this flexing or bending. [0046] Referring now to Figures 6a, 6b and 6C there is shown in figurative form different flexing arrangements to flex or bend focusing element 211. In Figure 5a, focusing element 211 is fixed on its side edge portions 212 to housing 120. Rotatable cam element 310 is positioned within housing 120 at the top (and/or bottom) of focusing element 211 and upon rotation exerts a force on a top (and/or bottom) central region 219 of focusing element 211 which is held in tension with respect to the fixed side edge portions 212. In this manner, cam element 310 is operable to cause focusing element 211 to flex or bend outwardly to a degree determined by the amount of rotation of cam element 211.

7 [0047] Figure 6b depicts another flexing arrangement or means wherein the top (and/or bottom) central region 219 of focusing element is fixed to housing 120 and includes two abutment screws 320 operable to abut against the front edge portion 217 of focusing element 211. Abutment screws 320 may then be rotated to exert a front force causing each front edge portion 217 to be displaced relative to the fixed central region 219 resulting in flexing or bending of focusing element 211 and an associated increase in the curvature of focusing element 211. [0048] Figure 6c depicts yet another flexing arrangement or means similar to the arrangement depicted in Figure 5b but instead involving two tensioning elements 330 that exert a tensioning force on each rear edge portion 218 of focusing element 211 again causing each edge portion 218 to be displaced relative to the fixed central region 219 to cause flexing or bending of focusing element 211 and increase the curvature of focusing element 211. [0049] In each of the arrangements depicted in Figures 6a, 6b and 6c the curvature of focusing element 211 may be reduced by reversing the operation employed initially to increase the curvature. As previously described, instead of being manually actuated each of the flexing means may be actuated by an appropriately controlled stepper motor or the like. [0050] Referring now to Figure 7a and 7b, there is shown a top sectional view of a sensor 300 according to a further illustrative embodiment. In this embodiment housing 120 is hermetically sealed and again focusing element 211 is formed of a flexible material mounted at its periphery within housing 120. In this embodiment, sensor 300 includes a flexing means in the form of pressure modification means 380 which functions to change the internal pressure within housing 120. An increase in the internal pressure of housing 120 causes focusing element 211 to flex or bend outwardly, thereby increasing its curvature and changing the viewing area of sensor 300 as previously described with respect to Figures 5a and 5b. [0051] In this embodiment, the pressure modification means is a micro-pump 381 controlled by electronic circuitry forming part of electronic control circuit 140. In this manner, an external switch (not shown) may be used to increase or decrease the internal pressure of housing 120 and as a result either increase or decrease the curvature of focusing element 211 respectively. [0052] In any of the above embodiments, focusing element 211 may be a Fresnel lens based element comprised of a single Fresnel lens element or including an array of Fresnel lens elements depending on configuration requirements. [0053] While the present illustrative embodiments have been described in relation to sensors operating in the infra-red band (i.e. 0.7 4 pm to 300pm) it will be readily apparent that consistent with the principles described herein that the present invention will have application to sensors operating in other wavelength bands.

8 [0054] Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. [0055] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge. [0056] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

Claims (20)

1. A sensor for sensing electromagnetic radiation from a viewing area including: a housing having an aperture for receiving electromagnetic radiation from the viewing area; a sensing region located within the housing, the sensing region sensitive to electromagnetic radiation and operable to provide an electrical signal once a predetermined threshold condition is met; a focusing element forming part of the sensor to direct electromagnetic radiation from the viewing area onto the sensing region, the focusing element formed of a flexible material wherein the focusing characteristics of the focusing element may be modified to modify the viewing area of the sensor; and flexing means to modify the focusing characteristics of the focusing element by flexing or bending the focusing element without obscuring a central region of the focusing element.

2. The sensor of claim 1, wherein the flexing means includes moveable abutment means that abut at least one edge of the focusing element to apply a flexing force.

3. The sensor of claim 2, wherein the moveable abutment means includes an adjustable screw that abuts a side edge portion of the focusing element.

4. The sensor of claim 2 or 3, wherein the moveable abutment means is manually actuated.

5. The sensor of claim 2 or 3, wherein the moveable abutment means is mechanically actuated.

6. The sensor of claim 1, wherein the flexing means displaces the edges of the focusing element with respect to the central region of the focusing element which is fixed.

7. The sensor of claim 1, wherein the flexing means displaces the central region of the focusing element with respect to fixed edges of the focusing element.

8. The sensor of claim 1, wherein the flexing means includes pressure modification means to change the internal pressure of the housing to cause the focusing element to flex or bend.

9. The sensor of claim 8, wherein the pressure modification means includes an electronically controlled micro-pump located in the housing.

10. The sensor of any one of claims 1 to 9, wherein the focusing element includes a resilient frame or surround portion. 10

11. The sensor of any one of the preceding claims, wherein the viewing area of the sensor is modified by modifying the acceptance angle of the sensor.

12. The sensor of any one of the preceding claims, wherein the viewing area of the sensor is modified by modifying the range of the sensor.

13. The sensor of any one of the preceding claims, where the sensor is operative to sense electromagnetic radiation in the infra-red range.

14. The sensor of claim 13, wherein the sensor is a passive infra-red (PIR) motion based sensor.

15. The sensor of any one of the preceding claims, wherein the focusing element is a Fresnel lens based element.

16. A method for modifying a viewing area of a sensor for sensing electromagnetic radiation, the sensor having a housing including an aperture to receive electromagnetic radiation from the viewing area, the method including: focusing by a flexible focusing element the electromagnetic radiation from the viewing area onto a sensing region located in the housing, the sensing region operative to provide an electrical signal once a predetermined threshold condition is met; modifying the focusing characteristics of the focusing element by flexing or bending the focusing element to modify the viewing area focused by the focusing element onto the sensor without obscuring a central region of the focusing element.

17. The method of claim 16, wherein the sensor is operative to sense electromagnetic operation in the infra-red range.

18. The method of claim 17, wherein the sensor is a passive infra-red (PIR) motion based sensor.

19. The method of any one of claims 16 to 18, wherein modifying the viewing area includes modifying the acceptance angle of the sensor.

20. The method of any one of claims 16 to 18, wherein the viewing area includes modifying the range of the sensor.