EP2760779A2

EP2760779A2 - Edge device

Info

Publication number: EP2760779A2
Application number: EP12787822.1A
Authority: EP
Inventors: Terence Platt; Karl Westhead; Carmel KELLEGHAN
Original assignee: Avire Ltd
Current assignee: Avire Ltd
Priority date: 2011-09-30
Filing date: 2012-10-01
Publication date: 2014-08-06
Also published as: GB2495141B; AU2012314039B2; GB2495141A; GB2521945B; AU2016266002A1; AU2012314039A1; GB2521945A; WO2013045953A3; GB201116915D0; CN104080725A; WO2013045953A2; GB201500882D0; CN104080725B; AU2012314039A8

Abstract

An edge device for an obstacle detection system has a housing in which an array of radiation emitters/receivers are provided. The edge device has, integrally formed with said housing,means for reflecting radiation emitted by the radiation emitters through a predefined angle.

Description

Edge Device

The present invention relates to an edge device, and in particular an edge device for a doorway having a powered door such as an elevator doorway.

Infrared beam systems for elevator or other powered doors generally use respective arrays of infrared transmitters and receivers (e.g. comprising infrared emitter/receiver diodes) to create a grid or 'curtain' of beams between two elongated edge detector devices mounted on, or alongside, the elevator doors. The interruption of any beam, for example due to an obstruction, results in the door motor being reversed and hence the doors opening (e.g. to allow a passenger to enter or leave). However, the need to accommodate diodes into a relatively narrow channel presents technical issues that can restrict the choice of diode packages that may be used and generally results in a relatively wide edge sensor (in a dimension perpendicular to the axis of the infrared beams). This is especially true of surface mount diode packages which are generally preferred as they can provide advantages in terms of improved manufacturing process. The difficulty in accommodating the diodes is not ideal in many applications, particularly where the detectors are mounted statically (i.e. on the lift in the running clearance between the lift doors and landing doors) where narrow detectors are preferable. Other issues with current detectors arise from the difficulties in achieving sufficient protection from external environmental conditions for example to conform with appropriate Ingress Protection (IP) Ratings which, for many applications, requires the detector to be totally protected against dust and at least having sufficient protection against ingress of water such that there is limited ingress in the presence of low pressure jets of water from all directions (corresponding to an IP rating of 65).

The invention therefore aims to provide an improved edge detector which overcomes or at least partially mitigates the above issues, preferably in a cost- effective way that does not add significantly to the manufacturing cost of the detector.

According to one aspect of the present invention, there is provided an edge device for an obstacle detection system, the edge device comprising: a housing; and an array of radiation emitters provided in the housing; and means for redirecting radiation emitted by the radiation emitters through a predefined angle for emission from the edge device for receipt by a complementary edge device on an opposite side of the doorway; wherein the redirecting means forms part of the housing.

According to one aspect of the present invention, there is provided an edge device for an obstacle detection system of a doorway, the edge device comprising: a housing; an array of radiation receivers provided in the housing; and means for redirecting radiation received by the edge device through a predefined angle for receipt by the array of radiation receivers; wherein the redirecting means forms part of the housing.

The redirecting means may comprise a reflective surface arranged to receive, in operation, the radiation and for reflecting the radiation incident on the reflective surface through the predefined angle. The reflective surface may comprise a surface of a material from which the housing is fabricated. The reflective surface may comprise a layer (e.g. a reflective layer or a polish layer), formed on a portion of the housing, the portion of the housing being arranged such that, in operation, the radiation incident on the layer is reflected through the predefined angle. The reflective surface may be only partially reflective (e.g. having an optical throughput of approximately 90% or less). For example, the reflective surface may have an optical throughput of between approximately 50% and 90%, preferably between approximately 60% and 85%, more preferably approximately 70% plus or minus 5%% or approximately 80% plus or minus 5%.

The housing may be fabricated from a reflective material whereby to provide the reflective surface. The housing may, for example, be fabricated from a metallic material (e.g. aluminium). The radiation may be infrared radiation.

The edge device may further comprise a circuit board on which the emitters/receivers are mounted. Each emitter/receiver may comprise a surface mount device. Each emitter/receiver may comprise a light emitting/photo- detecting diode.

The edge device may further comprise a lens for guiding and/or focussing the radiation. According to one aspect of the present invention, there is provided a lens for an edge device of an obstacle detection system, the lens comprising: a lens portion for focussing and or guiding radiation incident on the lens, the lens portion comprising a first material; and an interface portion for interfacing with a surface of a channel of the edge device to secure the lens in position in the channel when the edge device is assembled, the interface portion comprising a second material; wherein the second material is softer than the first material.

The lens may be elongated in a direction substantially perpendicular to an optical axis of the lens. The lens may, for example be between approximately 1.5m and 2.5m in length, for example between approximately 1.75m and 2.25m in length, for example about 2m in length.

At least one of the materials may comprises a plastics material (e.g. polyvinyl chloride (PVC) material).

According to one aspect of the present invention, there is provided a method of manufacturing the lens according to a previous aspect comprising co-extruding the first and second materials to form the lens.

According to one aspect of the present invention, there is provided an edge device for an obstacle detection system, the edge device comprising: a housing; an array of radiation emitters and or receivers provided in the housing; and a lens according to a previous aspect.

The housing may comprises means for interfacing with the lens to form a tight friction fit whereby to seal the housing from environmental conditions. The housing may comprise means for interfacing with the interface portion of the lens whereby to seal the housing from environmental agents such as dust and/or water. The interfacing means may be adapted to produce a seal that inhibits the ingress of dust and/or water to a predefined ingress protection rating. The interfacing means may be adapted to produce a seal that inhibits the ingress of dust and water to a ingress protection rating equal to or in excess of 54. The interfacing means may be adapted to produce a seal that inhibits the ingress of dust and water to a ingress protection rating equal to or in excess of 65.

The edge device may further comprise means for retaining the lens at each longitudinal end thereof. The retaining means may comprise a clamp portion (preferably at one longitudinal end of said lens), through which said lens extends, whereby to allow movement of the lens due to expansion and/or contraction in the longitudinal direction. The clamp portion through which said lens extends may comprise a gasket, at an interface between the lens and the clamp portion, whereby to maintain a seal with the lens as the lens expands and/or contracts.

According to one aspect of the present invention, there is provided a housing for an edge device of an obstacle detection system, the housing comprising: means for receiving an array of radiation emitters and/or radiation receivers; and means for redirecting radiation, emitted by the radiation emitters and/or to be received by the radiation receivers, through a predefined angle.

According to one aspect of the present invention, there is provided a method of assembling an edge device for an obstacle detection system, the method comprising: providing a housing; and assembling an array of radiation emitters and/or radiation receivers in the housing; wherein the housing comprises means for redirecting radiation, emitted by the radiation emitters and/or to be received by radiation receivers, through a predefined angle.

The method may further comprise assembling the lens of a previous aspect in the housing.

It will be appreciated that the terms 'edge detector' and 'edge device', as referred to herein includes receiver edge devices comprising radiation receivers (also referred to as sensors), emitter edge devices comprising radiation emitters (also referred to as transmitters), and/or combined receiver/emitter edge devices comprising both radiation receivers and emitters.

Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently (or in combination with) any other disclosed and/or illustrated features. In particular but without limitation the features of any of the claims dependent from a particular independent claim may be introduced into that independent claim in any combination or individually. According to one aspect of the invention, there is provided an edge device for an obstacle detection system that has a housing in which an array of radiation emitters/receivers are provided. The edge device of this aspect has, integrally formed with said housing, means for reflecting radiation emitted by the radiation emitters through a predefined angle.

Embodiments of the invention will now be described by way of example only with reference to the attached figures in which: Figure 1 shows a partial and simplified isometric view of the two ends of an edge device;

Figure 2 shows a simplified transverse cross-sectional view of the edge device of Figure 1 ;

Figure 3 shows a partial, cut-away, and simplified isometric view of the edge device of Figure 1 ; and

Figure 4 shows a partial, and simplified isometric view of the edge device of Figure 1 in a partly disassembled state.

Overview

Figures 1 to 4 shows an edge device for using an obstacle detection system of a doorway, such as an elevator doorway, comprising a powered door generally at 10. The edge device 10 comprises a housing 12 having an internal surface forming a channel 14 configured to receive a circuit board 16 on which an array of infrared diodes 18 are arranged, and to receive a lens 20 for guiding and/or focussing infrared radiation transmitted by (or to be received by) the infrared diodes 18.

In this embodiment where the edge device 10 is to be used as an edge sensor device for receiving the infrared radiation, the infrared diodes 18 comprise infra red receiver diodes and where the edge device 10 is to be used as an edge emitter device for transmitting the infrared radiation, the infrared diodes 18 comprise infrared transmitter diodes. Generally, this embodiment will be described with reference to an edge 'emitter' device comprising infrared transmitter diodes 18 but it will be appreciated that the description applies equally to edge sensor devices for receiving the radiation.

As best seen in Figure 2, the channel 12 is arranged such that, when the edge device 10 is assembled, the circuit board 16 is located in a plane substantially parallel to a longitudinal axis (χ-χ') of the edge device 10 and parallel to the direction Y (Υ') in which radiation 22 is emitted from (or received by) the lens 20 (e.g. in a direction generally parallel to transverse axis y-y'). The housing 12 comprises a reflective surface 24 arranged to redirect the radiation 22 emitted from (or received by) the infrared diodes 18 in the direction of the lens 20 (or receiver diode). Thus, the radiation 22 is emitted from (or received by) the infrared diodes 18 has an optical axis generally perpendicular to the axis with which the radiation 22 is to be emitted from (or received by) the edge device 10 (albeit that in this embodiment the infrared radiation 22 is emitted in a generally conical radiation pattern having the optical axis at its approximate centre).

Accordingly, because the circuit board 10 is thin (typically 1.2mm / 1.6mm) and arranged substantially parallel to the direction Y (Υ') in which radiation is emitted from (or received by) the edge device 10, the housing 12 can, advantageously, be made significantly narrower. It will be appreciated that the term 'narrower' refers to a dimension extending in a transverse direction generally perpendicular both to a direction Y (Υ') in which radiation 22 is emitted from (or received by) the edge device 10 and the longitudinal axis (χ-χ') of the edge device 10 (e.g. a dimension extending in a direction generally parallel to axis z-z').

The channel 14 and lens 20 are also advantageously configured such that when the edge device 10 is assembled, the lens 20 forms a sealing interface with the internal surface of housing 12 that forms the channel 14 that is sufficiently close- fitting to seal the channel 14 to prevent the ingress of dust and/or water into the channel to achieve a desired ingress protection (IP) rating. In this embodiment, the IP rating achieved is IP65 although higher IP ratings are possible depending on the requirements of the application in which the edge device 10 is to be used.

Effectively, therefore, the edge device avoids the issues associated with known edge device by 'folding' the optical path allowing a greater choice of infrared diodes to be used. For example cheaper surface mount diodes, which would not previously have been used because of the need to accommodate a relatively large circuit board footprint and combined circuit board plus diode height, can now be used (on both the emitter and the receiver sides of the system). Typically, for example, attempting to accommodate such a circuit board in existing arrangements would result in the width of the detector being the width of the circuit board (typically 10 to 18mm) plus the thickness of the channel that the circuit board will sit within. Accordingly, the edge device 10 of this embodiment can provide a narrower design, using any of a wider range of emitter and receiver diodes (especially surface mount devices) and can therefore provide significant cost savings.

The ease with which a desired IP rating can be achieved is also improved by the construction of the lens 20 which comprises a relatively thick lens (in the direction that light is emitted from or received by the lens), which improves the surface area contact between the lens and the channel 14. The ingress protection is further enhanced by forming the lens 20 from a first, relatively hard, transparent or translucent material which forms a focussing portion 28 of the lens through which the radiation is focussed in operation and a second, relatively soft, material which forms the longitudinal sides 30 of the lens 20 that form the seal with the housing 12. Thus, when the edge device is assembled the softer material of the longitudinal sides 30 conforms to the internal surface of the housing 12 to form an improved seal, whilst the harder material of the focussing portion ensures that the structural integrity and robustness of the edge device is maintained.

The construction of the lens also provides benefits during assembly by improving the ease with which the lens 20 can be pushed into the channel 14 whilst still forming a substantially watertight seal.

The various components of the edge device 10 will now be described in more detail, by way of example only.

Housing The housing 12 is elongated in a longitudinal direction (e.g. in a direction parallel to axis x-x' in the figures). The internal surface of the housing 12 forming the channel 14 defines two sections 32, 34, each extending in the longitudinal direction. One section 32 is configured for receiving the circuit board 16 and comprises the reflective surface 24. The other section 34 is configured for receiving the lens 20. The internal surface defining the circuit board receiving section 32 forms a recess 36, extending in the longitudinal direction, for receiving the circuit board 16 in a relatively close-fitting arrangement in the recess 36. The internal surface of this section 32 also comprises a protrusion 38 extending from a wall of the housing 12, and in the longitudinal direction, to form a groove between the protrusion 38 and a base of the recess 32, into which groove an edge of the circuit board 16 may be received thereby helping to retain the circuit board 16 in position when the edge device 10 is assembled.

The internal surface defining the circuit board receiving section 32 of the channel 14 also defines a mirror portion 40 comprising the reflective surface 24. The mirror portion 40 extends in the longitudinal direction, opposite the recess 36, and is inclined relative to the base of the recess 36 such that, when the edge device 10 is assembled with the circuit board and lens 20 in place, the radiation 22 emitted from (or received by) the infrared diodes 18 provided on the circuit board 16 is reflected, by the reflective surface 24, towards the lens 20 (or towards the infrared receiver diodes in the case of an edge sensor). In the present embodiment the reflective surface 24 is substantially planar. However, it will be appreciated that the reflective surface 24 may be curved, for example concavely to help focus the radiation incident on the surface, or convexly to distribute the radiation if appropriate.

The reflective surface 24 of this embodiment is an integral part of the material from which the housing 12 is made. Specifically, the reflective surface 24 of this embodiment comprises a surface of the material from which the housing 12 is fabricated. This is particularly advantageous because it significantly reduces the cost and complexity of manufacturing when compared, for example, to an alternative embodiment in which a reflective material is adhered to the material of the housing 12.

In this embodiment, the material from which the housing 12 is manufactured comprises a lightweight metallic material, such as aluminium, which is fabricated in an extrusion process. Whilst aluminium is known not to have a high quality mirror surface without relatively extensive polishing, somewhat surprisingly it has been found that aluminium is sufficiently reflective to meet the technical requirements of edge detector devices. Specifically, it has been found that the approximately 80% throughput of the infra-red light achieved with a relatively virgin surface (with minimal or no polishing) is sufficient to provide highly effective detection apparatus. The use of aluminium is also has the benefit that the resulting aluminium reflective surface 24 ages well thereby enhancing the longevity and reliability of the edge sensor.

The internal surface defining the lens receiving section 32 of the channel 14 comprises lens interface portions 42 which interface with respective sides of the lens 20 when the edge device 10 is assembled. Each lens interface portions 42 is uneven in profile to provide an improved seal between the lens 20 and the internal surface defining the lens receiving section 34. Specifically, each lens interface portions 42 has a generally 'saw-tooth' shaped transverse cross-section each 'tooth' of which extends in the longitudinal direction and engages with the relatively soft material which forms the longitudinal sides 30 of the lens 20 that form the seal with the housing 12. The shape and dimensions of the housing 12, and in particular those of the circuit board receiving section 32, are such that when the edge device 10 is assembled, the diode 18 is in close proximity (typically ~3mm plus or minus 1 mm at the centre of the reflective surface, ~1.5mm plus or minus 0.5mm at its closest point and ~4mm plus or minus 1 mm at its furthest point) to the reflective surface 24 and to the rear of the channel (the rear being transversely at the opposite side of the channel to the lens as seen in Figure 2) to help reduce the effects of parasitic light. More specifically, the proximity of the diode 18 to the reflective surface 24 is such that the scatter due to the surface imperfections inherent to materials such as aluminium are minimised. Accordingly, since infra-red has a longer wavelength that visible light the aluminium surface (which appears to be a very poor reflector to visible light) is of sufficient quality for infrared. Further, the performance of the reflective surface 24, which is affected by the amount of scattering from the inherently imperfect surface, is ameliorated by the proximity with which the diodes 18 are placed to the reflective surface thereby reducing the effect of the scattering due to surface imperfections are minimised (this is especially beneficial on the receiver side).

The housing 12 also comprises a mounting portion 44 for mounting the edge device 10 in an elevator door or doorway of in any other similar application. The mounting portion comprises a longitudinal keyway 46 adapted to co-operate with a corresponding 'key' to secure the edge device in position. The 'key' may comprise, for example, the bolts or screws having heads that engage in the keyway 46 and shafts which extend out of the keyway 46 to securely mount the edge device 10.

The housing may be any suitable length and other dimensions. Typically however, the housing (and hence the lens and circuit board) is in the region of a human being's height, for example in the region of 1.5 to 2.5 metres long, more preferably in the region of 2 metres long, although this may vary depending on application. Typically, the housing can be very narrow (e.g. in the region of 10mm wide) because of the beneficial arrangement of circuit board and reflecti9ve surface. The housing may, however, be wider (e.g. between 10mm and 20mm or between 10mm and 15mm) or narrower (e.g. between 5mm and 10mm).

Lens The lens 20 extends in the longitudinal direction, is prismatic in shape, and has a general wedge shaped transverse cross-section with a convex external (when assembled) surface. The lens 20 is configured such that radiation 22 emitted by the emitter diodes 18 reflected by the reflective surface 24 is guided and focussed to form a substantially parallel beam. The lens is provided with a wide aperture to ensure sufficient light is focused on the reflective surface (in the case of a receiver edge device).

In the case of the receiver edge receiver device the lens 20 is configured such that a beam of radiation 22 received by the lens 20 is guided onto the reflective surface 24 which in turn reflects it onto the receiver diodes 18. Advantageously, the lenses 20 on the emitter and receiver sides are designed to have identical cross-sections to simplify the manufacturing process.

In this embodiment the relatively hard and relatively soft materials of the lens 20 each comprise a polyvinyl chloride (PVC) material or other such resin having the desired hardness (although any suitable material may be used). PVC may appear to be an unexpected choice for a lens material because it is generally understood to have relatively poor optical properties and to be problemetic due to the relatively high differential rates of expansion/contraction. However, it has been found that its optical properties are sufficient for the typical obstacle sensing applications for which it is to be used. Further, the use of the dual material structure, in conjunction with the structure of the lens receiving section 34 of the housing can ameliorate potential issues with expansion and contraction. Accordingly PVC, which is cheaper than alternatives such as Polycarbate can beneficially be used to further reduce the manufacturing costs of the edge device 10.

Further, as best seen in Figure 1 , the edge device 10 comprises retainers 50, 50' at either longitudinal end of the housing 12 which help to hold the lens 20 in position when the edge device 10 is assembled. The retainer 50 at one end (typically the bottom end when installed) is configured to cradle one longitudinal end of the lens to inhibit movement in the x' to x direction whilst the retainer 50' at the other end comprises a clamp portion 52 through which the lens 20 extends by a short distance (typically between 10mm and 30mm) thereby allowing the lens 20 to expand and contract in the longitudinal direction whilst maintaining the desired ingress protection rating. The clamp portion 52 also comprises a gasket arranged to interface with the back of lens (the back being the opposite side to the curved surface of the lens) so that as the lens 20 expands and contracts the seal is maintained at the end of the edge device 10.

Advantageously, to simplify the manufacturing process, the two materials of the lens 20 are coextruded to form the desired lens profile (although any other suitable manufacturing process may be used).

Circuit Board The circuit board 16 comprises the circuitry required to access and control the diodes (although the driver and control circuitry itself may be provided separately to reduce circuit footprint). The diodes are positioned on the circuit board 16 such that when the edge device 10 is assembled with the circuit board and lens 20 in place, the radiation 22 emitted from (or received by) the infrared diodes 18 provided on the circuit board 16 is reflected, by the reflective surface 24, towards the lens 20 (or towards the infrared receiver diodes in the case of an edge sensor). Typically, between 8 and 48 diodes are provided per edge device 10. Modifications and alternatives

Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

It will be appreciated that whilst, in the above embodiments, each detector device comprises an array of infrared receiver diodes and/or an array of infrared transmitter diodes, the detector may comprise an array comprising a combination of transmitters and receivers. Further, whilst infrared sensors and emitters are particularly advantageous, other sensors and emitters may be used to produce a detection curtain comprising beams of any form of radiation (e.g. visible light or other form of electromagnetic radiation) suitable for the application for which the detector is to be used.

Although the material from which the housing is made is described as being aluminium it will be appreciated that any suitable metallic or plastics material may be used although preferably the material is such that it can be moulded or otherwise worked relatively easily to ensure the manufacturing process remains cost-effective.

Whilst having the reflective surface formed from the same material as the housing is particularly beneficial and reduces cost significantly, in other applications, where the mirror quality of the reflective surface is paramount then a reflective layer of a different material may be adhered to, or coated on, the mirror portion of the housing. Further, the inherent reflectivity of the housing material could be enhanced by coating the reflective surface with a layer of an appropriate substance (e.g. a polish).

Whilst it is particularly beneficial, in terms of simplifying the accommodation of the necessary circuitry and diodes, to redirect the radiation from the emitter (or to the receiver) diodes through approximately 90° the arrangement could be altered depending on requirements. For example, in some applications it may be helpful to redirect the radiation at a more acute or more obtuse angle (say in a range of 45° to 135°).

Claims

1. An edge device for an obstacle detection system, the edge device comprising: a housing; and an array of radiation emitters provided in said housing; and means for redirecting radiation emitted by the radiation emitters through a predefined angle for emission from said edge device for receipt by a complementary edge device on an opposite side of the doorway; wherein said redirecting means forms part of said housing.

2. An edge device for an obstacle detection system of a doorway, the edge device comprising: a housing; an array of radiation receivers provided in said housing; and means for redirecting radiation received by said edge device through a predefined angle for receipt by said array of radiation receivers; wherein said redirecting means forms part of said housing.

3. An edge device as claimed in claim 1 or 2 wherein said redirecting means comprises a reflective surface arranged to receive, in operation, said radiation and for reflecting said radiation incident on said reflective surface through said predefined angle.

4. An edge device as claimed in claim 3 wherein said reflective surface comprises a surface of a material from which said housing is fabricated.

5. An edge device as claimed in claim 3 or 4 wherein said reflective surface comprises a layer, formed on a portion of said housing, said portion of said housing being arranged such that, in operation, said radiation incident on said layer is reflected through said predefined angle.

6. An edge device as claimed in any of claims 3 to 5 wherein said reflective surface is partially reflective (e.g. having an optical throughput of approximately 90% or less).

7. An edge device as claimed in any of claims 3 to 6 wherein said housing is fabricated from a reflective material whereby to provide said reflective surface.

8. An edge device as claimed in claim 7 wherein said housing is fabricated from a metallic material (e.g. aluminium).

9. An edge device as claimed in any preceding claim wherein said radiation is infrared radiation.

10. An edge device as claimed in claim 1 or any claim dependent therefrom further comprising a circuit board on which said emitters are mounted.

1 1. An edge device as claimed in claim 10 wherein each said emitter comprises a surface mount device.

12. An edge device as claimed in claim 10 or 1 1 wherein each said emitter comprises a light emitting diode.

13. An edge device as claimed in claim 2 or any claim dependent therefrom further comprising a circuit board on which said receivers are mounted.

14. An edge device as claimed in claim 13 wherein each said receiver comprises a surface mount device.

15. An edge device as claimed in claim 13 or 14 wherein each said receiver comprises an photo-detector diode.

16. An edge device as claimed in any preceding claim further comprising a lens for guiding and/or focussing said radiation.

17. A lens for an edge device of an obstacle detection system, the lens comprising: a lens portion for focussing and or guiding radiation incident on the lens, the lens portion comprising a first material; and an interface portion for interfacing with a surface of a channel of the edge device to secure said lens in position in said channel when the edge device is assembled, the interface portion comprising a second material; wherein the second material is softer than the first material.

A lens as claimed in claim 17 wherein said lens is elongated in a direction substantially perpendicular to an optical axis of the lens.

A lens as claimed in claim 18 wherein said lens has a length of between approximately 1.5 m and 2.5m.

A lens as claimed in any of claims 17 to 19 wherein at least one of said materials comprises a plastics material (e.g. polyvinyl chloride (PVC) material).

A method of manufacturing the lens of any of claims 17 to 20 comprising co-extruding said first and second materials to form said lens.

An edge device for an obstacle detection system, the edge device comprising: a housing; an array of radiation emitters and or receivers provided in said housing; and a lens according to any of claims 17 to 20.

An edge device as claimed in claim 16 or 22 wherein the lens comprises a lens according to any of claims 17 to 20.

An edge device as claimed in claim 16, 22 or 23 wherein the housing comprises means for interfacing with the lens to form a sealing fit whereby to seal said housing from environmental conditions.

An edge device as claimed in claim 23 wherein the housing comprises means for interfacing with said interface portion of said lens whereby to seal said housing from environmental agents such as dust and/or water. An edge device as claimed in claim 24 or 25 wherein the interfacing means is adapted to produce a seal that inhibits the ingress of dust and/or water to a predefined ingress protection rating.

An edge device as claimed in claim 26 wherein the interfacing means is adapted to produce a seal that inhibits the ingress of dust and water to a ingress protection rating equal to or in excess of 54.

An edge device as claimed in claim 27 wherein the interfacing means is adapted to produce a seal that inhibits the ingress of dust and water to a ingress protection rating equal to or in excess of 65.

An edge device as claimed in any of claims 23 to 28 further comprising means for retaining the lens at each longitudinal end thereof.

An edge device as claimed in claim 27 wherein the retaining means comprises a clamp portion (preferably at one longitudinal end of said lens), through which said lens extends, whereby to allow movement of the lens due to expansion and/or contraction in the longitudinal direction.

An edge device as claimed in claim 30 wherein the clamp portion through which said lens extends comprises a gasket, at an interface between the lens and the clamp portion, whereby to maintain a seal with the lens as the lens expands and/or contracts.

A housing for an edge device of an obstacle detection system, the housing comprising: means for receiving an array of radiation emitters and/or radiation receivers; and means for redirecting radiation, emitted by the radiation emitters and/or to be received by said radiation receivers, through a predefined angle.

A method of assembling an edge device for an obstacle detection system, the method comprising: providing a housing; and assembling an array of radiation emitters and/or radiation receivers in said housing; wherein the housing comprises means for redirecting radiation, emitted by the radiation emitters and/or to be received by radiation receivers, through a predefined angle.

A method as claimed in claim 33 further comprising assembling the lens of any of claims 17 to 20 in said housing.