NL2034575B1

NL2034575B1 - Luminaire and system including the same

Info

Publication number: NL2034575B1
Application number: NL2034575A
Authority: NL
Inventors: Hans Van Der Voort Ronald
Original assignee: Epeon
Priority date: 2023-04-14
Filing date: 2023-04-14
Publication date: 2024-10-21
Also published as: EP4446498A1

Abstract

The document relates to a luminaire, comprising a rotatable body and a socket. The rotatable body comprising a housing deﬁning an outer shape of the rotatable body, a part of which 5 is shaped as at least part of a sphere; and, a light source, arranged inside of the housing and providing a diverging light beam. The socket is conﬁgured to receive the part of the housing shaped as at least part of a sphere as the ball part of a ball-and-socket joint. Said part of the housing and the socket are shaped complementary to allow for the rotatable body to be rotated along three orthogonal axes of rotation, thereby changing the ﬁeld of view. 10 [Fig 2A]

Description

LUMINAIRE AND SYSTEM INCLUDING THE SAME

The present application concerns a luminaire, a system for projecting a line of light on a surface, and a support such as a post including a part of the luminaire.

Luminaires are known from the art. A luminaire generally comprises a housing in which at least one light source is arranged, and frame members in which said housing is arranged. Light sources in combination with one or more optical elements emit a light beam having an angular width, herein also referred to as beam divergence, beam angle, or a “field of view” (originating from the light source). These terms are used herein to describe the angle subtended by the light beam at the light source.

Traditional road markings are important for road users to see the course of the road and for traffic safety. However, road markings are not always visible enough because of wear and/or bad weather conditions. Luminaires may be used to project light forming such road markings. Projected road markings enhance the visibility of the course of roads and cycle paths and potentially can help inreducing traffic casualties. Consistency in road markings becomes particularly relevant when they are used by driver assistance systems (ADAS), which heavily rely on well visible road markings. It is therefore important that the projected road markings are exactly at their desired location on the road and in the right direction.

At the same time, to keep cost at a minimum, installing luminaires — including arranging the housings in corresponding frame members - should be quick and easy.

These goals result in opposing requirements. A housing of which the position and/or orientation is difficult to change is likely also more difficult to instal. Vice-versa, a housing that is simply to install may be easily displaced, removed, and stolen by malicious actors, such as vandals or thieves.

It is an object of the invention to provide a luminaire of which the light beam can be arranged very accurately, such that a projection of the light beam on the road can be arranged accurately and reliably at a desired location, and/or in a desired direction.

It is a further object of the invention to provide a luminaire that may be quickly and easily installed, and at the same time is less vulnerable to efforts by external actors to change its position and/or orientation.

At least one of the abovementioned objects and/or other objects is at least partially achieved in a luminaire according to appended claim 1. The luminaire comprises a rotatable body and a socket. The rotatable body comprises a housing and a light source. The housing defines the outer shape of the rotatable body. the housing or a part of the housing of the rotatable body is shaped so as to at least partially or even fully from a sphere (herein also referred to as a “ball”). The at least one light source and the one or more optical elements are all arranged inside the housing and provide a light beam of a desired angular width. The socket is configured to receive the part of the housing shaped as at least part of a sphere as the ball part of a ball-and-socket joint. In other words, the housing of the luminaire has a double function: first of all it forms a protection for the elements arranged inside the housing such as the at least one light source and possible further optical elements, secondly the housing is part of the joint (connected or connectable to a post, for instance) that enables the housing and the light source/optical elements fixedly arranged therein, to be properly orientated relative to the road. More specifically, the (part of the) housing and the socket are shaped complementary to allow for the rotatable body to be rotated along three orthogonal axes of rotation, there changing the orientation of the light beam emitted by the luminaire.

The part of the housing shaped as at least part of a sphere can have a number of shapes. In some embodiments, it comprises a spherical segment and/or a spherical cap. In some embodiments, it comprises a hemisphere, and preferably a sphere.

The socket can also be implemented in a number of ways. In some embodiments, the socket comprises at least one of a surface comprising a bowl- or cup-like depression and one or more protrusions configured to at least partially enclose the luminaire.

In some embodiments, when the rotatable body is received in the socket, a contact area between the housing and the socket is contiguous. This makes the housing harder to grasp and get a hold on, making it harder to change the orientation of the luminaire, for intention unintentionally or maliciously.

In some embodiments, the socket is configured be in the following states: - a first state, in which the rotatable body can be removed from the socket; - a second state, in which the rotatable body cannot be removed from the socket, and in which the rotatable body can be rotated in the socket: - a third state, in which the rotatable body cannot be removed from the socket and in which the rotatable body the orientation of the rotatable body in the socket cannot be adjusted.

This allows for easy installation while at the same time limiting the risk of the orientation of the luminaire changing, for example unintentionally.

The luminaire can fulfil a number of lighting function. In some embodiments, the light source is configured to emit a beam of light, and preferably configured to emit a line-laser. In some embodiments, the luminaire is configured to project a line of light on a surface, for instance a traffic surface, when in operation.

Such lighting functions may, in tum, be achieved in a number of ways. In some embodiments, at least one optical element, for instance at least one of a lens element and a reflective element, is arranged in the housing, wherein the at least one optical element is configured to receive light from the light source and to emit a divergent light beam able to project a line of light on a surface, for instance a traffic surface like a road.

In some embodiments, the light source comprises a laser source configured to emit a laser beam, and one or more optical elements configured as a beam former, such as a prism or a mirror, configured to form the laser beam into a divergent beam of light.

In some embodiments, the housing comprising a transparent window through which the field of view extends. Preferably, the luminaire further comprises a laser source and a beam former, wherein the laser source and beam former are arranged inside the housing, and configured such that diverging laser light beam is emitted through the transparent window.

The luminaire may, for example, be used to project road markings onto a traffic surface.

Other directive functions may also be used, such as projecting arrows. For these functions, but also for many other conceivable functions, the orientation of the luminaire changing may cause confusion or even hazardous situations. To avoid this, in some embodiments the rotatable body further comprises sensing means configured to detect a change in a position or orientation of the luminaire and controlling means configured to dim or turn off the light source when a change in the position or orientation of the rotatable body is detected.

In some of such embodiments, the sensing means are be configured to measure a change in position and/or orientation of the rotatable body, such as an accelerometer, a gyroscope or a magnetometer, and the controlling means are further configured to dim or turn off the light source when a total amount of change in position and/or orientation exceeds a first predetermined threshold.

Additionally and/or alternatively, in some embodiments the sensing means are configured to measure an orientation of the rotatable body, such as a gyroscope, and the controlling means are further configured to store a baseline orientation of the rotatable housing, periodically measure the orientation of the rotatable housing, and dim or turn off the light source when a difference between the baseline orientation and the measured orientation exceeds a second predetermined threshold.

Turning the light source on or off manually may take time or require specific tools. Turning the light source on or off may require opening of the housing and/or removing the rotatable body from the socket. This is preferably avoided. In some embodiments, the controlling means are further configured to, after dimming or turning off the light source, turning the light source back on when an inverse of the change in the position or orientation of the rotatable body is detected. For example, the original function of the luminaire may than be performed again.

In some of such embodiments, the controlling means are further configured to, after dimming or turning off the light source, turn the light source back on when the total amount of change in position and/or orientation is smaller than the first predetermined threshold.

Alternatively and/or additionally, in some embodiments the controlling means are further configured to, after dimming or turning off the light source, periodically measure the orientation of the rotatable housing, and tarn the light source back on when the difference between the baseline orientation and the measured orientation is smaller than the second predetermined threshold.

The luminaire is preferably positioned with relatively great degrees of freedom. In some embodiments, the socket is further configured to be releasably attached to a support such as a pole or a post. The socket may also be integrally formed with or fixedly connected to a support. The application further provides for a system for projecting a line of light on a surface, for instance a traffic surface, the system comprising a luminaire as claimed in any of the preceding claims, a support for supporting the luminaire, wherein the socket of the luminaire is integrally formed with or fixedly connected to the support. Preferably, the support is a pole or a post configured to be anchored into the ground.

The application furthermore provides for a support, for instance a post, the support comprising a socket, for supporting the luminaire, the support comprising the socket configured to receive the part of the housing of the luminaire as covered by any of the previously discussed embodiments.

Further details on, and advantages of embodiments of the luminaire according to embodiments of the present invention are elucidated in the accompanying figures, in which: figure 1 shows an environment in which an embodiment of a luminaire may be deployed; figures 2A and 2B show various sides of an embodiment of the luminaire; figure 3 shows a further embodiment of the luminaire; figure 4 shows half of a further embodiment of the luminaire; figure 5 shows a further embodiment of the luminaire; figure 6 shows a schematic representation of an embodiment of the laminaire according to the invention.

Embodiments of the present disclosure comprise a system for projecting a line of light on a surface, for instance a traffic surface. The line of light can be projected to add additional surface markers on the surface, to replace the surface markings already present on the surface and/or on top of the existing surface markings to enhance visibility thereof. The system comprises a luminaire 1 and a support, like a post 100. for supporting the luminaire. The luminaire is configured to project a line of light on a surface, for instance a traffic surface. Referring to figure 1, the surface may correspond to a traffic surface. The term “traffic surface” may refer to any space intended to sustain vehicular and/or pedestrian traffic, such as a road surface ((sub)urban streets or boulevards, roads, highways, countryside roads or paths, etc.), a biking or skating surface (bikeways, skateparks, ways dedicated to light electric vehicles (LEVs}, micro-EVs, etc.), a pedestrian surface (public places, markets, parks, pathways, sidewalks, zebra crossings, etc.), a railway surface (railways tracks for trams, trains, etc.), a water surface (waterways for boats, jet skis, etc.), or a way surface dedicated to aircrafts, such as a taxiway or a runway. The surface may comprise one or more surface markings 103 (e.g. an arrow road marking, a bike-only lane, a one-way lane, etc.) instructing vehicles and/or pedestrian to behave appropriately on the traffic surface (e.g. drive forward, turn left, do not cross 5 the line, etc.). For example, a surface marking may correspond to a continuous line instructing vehicles to travel within the surface, and the second surface marking may correspond to a dashed line allowing vehicles to change lane. While in figure 1 the system is provided to the side of the traffic surface, it could also be provided on or above the traffic surface, for instance being mounted on existing infrastructure, such as overhead road signage and the like.

Figure 1 shows an embodiment of a luminaire 1 attached to a pole 100 arranged next to a traffic surface like a road 102. Luminaire 1 is configured to emit a light beam 104, for instance a beam of laser light, towards the road 102. The laser light beam 102, after having been generated by the laser light source 131 and after having passed one or more optical elements (to be described later), is given a sufficiently large angular width so as to form a diverging light beam that may generate one or more (rectangular and/or curved) lines 105 of light when projected on the traffic surface (for instance, on the surface of the road 102, cf. figure 1). The line may be projected on existing road markings 103, i.e. road markings already present on the traffic surface, and/or at any other position, for instance at a different position beside the existing road markings. These road markings 103are generally oblong/rectangular but can also have other elongated shapes.

In the environment shown in figure 1, the line of light 105 coincides with part of the road marking 103 that is arranged on the same side of the road as luminaire 1 and as pole 100 to which luminaire 1 is attached. This is advantageous as it prevents people passing pole 100 from passing through line-laser 104. Luminaire 1 can also be used to project a line of light 105 on other positions on road 102.

Line of light 105 generally extends in the same direction as road 102. In this environment, luminaire 1 is used to supplement existing road markings. It is also possible that luminaire 1 provides the only road markings. Luminaire 1 may also be used to project other shapes than lines and/or for other purposes than for road markings.

Figures 2A and 2B show, from different perspectives, an embodiment of luminaire 1 according to the invention. In the embodiment shown, luminaire 1 comprises a spherical housing 10 and a socket 20. It could be said that figure 2A shows luminaire 1 from the side, and figure 2B from the front.

Housing 10, in combination with the complementary shaped socket 20 offers exactly the required degrees of freedom along the three rotational axis’, RX, RY and RZ to position the projected line 105 correctly. The housing is in fact the ball of the ball-joint.

In this embodiment, socket 20 is made up of a frame member 21, attached to pole 100, and three fingers 22a, 22b, 22¢, in turn attached to frame member 21. Frame member 21 and fingers 22a, 22b, and 22c are shaped complementary to spherical housing 10, providing a socket 20 in which spherical housing 10 can be received. Fingers 22a, 22b, and 22c may be attached to frame member 21 via screws. The fingers, in this embodiment, are spaced uniformly apart — i.e. over 120 degrees.

For embodiments with two or four fingers, uniform spacing would imply the fingers extending over (slightly less than) 180 and 90 degrees, respectively. Exact uniform spacing of three fingers or more, however, is not necessary — some deviation may exist. Preferably, there is no pair of adjacent fingers in the plurality of fingers of which the fingers are placed more than 180 degrees apart. For an embodiment of two fingers, this means that the fingers have to be arranged on opposing sides of housing 10. Further embodiments can be conceived as well.

Once received, housing 10 can be considered an example of a rotatable body and can be rotated in three rotational directions (considered from the field of view). These directions are also referred to as the jaw, pitch, and roll.

In this embodiment specifically, the amount of grip that fingers 22a, 22b, and 22¢ collectively have on housing 10 can be adjusted via said screws. While the amount of grip is technically a continuous variable — i.e. may take on any particular level - this embodiment, three operational states may be identified:

When the screws are turned tight, and fingers 22a, 22b, and 22¢ have sufficiently high grip on housing 10, so housing 10 cannot be rotated in the socket 20, and thus certainly cannot be removed. When the screws are loosed somewhat, fingers 22a, 22b, and 22c will eventually have so little grip on housing 10 that housing 10 can be rotated in socket 20, allowing for a change in the field of view. When the screws are loosed further, fingers 22a, 22b, and 22c will eventually have so little grip on housing 10 that housing 10 can be removed from socket 20.

The skilled person will appreciate that socket 20 and the releasable connection to the housing 10 may also be provided by other means. The fingers are examples of protrusions that the socket may comprise. In the embodiment shown in figure 2A, frame member 21 comprises a depression in which part of housing 10 can be received. The skilled person will appreciate that socket 20 does not have to comprise both (clamping) protrusions and a depression. Embodiments are conceivable in which socket 20 comprises only one of these.

In this embodiment, the outer shape of housing 10 is defined by housing element 11a, cooling disc 14a, annular window 12, cooling disc 14b and housing element 11b. Inside of housing 10 are arranged a laser source 131 and mirror 132.

The outer shape of housing element 11a (and housing element 11b, for that matter) is a spherical cap (i.e. a spherical dome), being a part of a sphere cut off by a plane. The outer shape of annular window 12 (and cooling discs 14a, 14b, for that matter) is a spherical segment (i.e. a spherical frustum), being a part of a sphere that lies between two planes. Together these elements form substantially spherical housing 10.

The embodiment shown here is provided with the optional, though advantageous cooling discs 14a, 14b. Said discs 14a, 14b may, for example, be made of aluminium, but may be made of other heat-conducting materials as well. Such discs 14a, 14b can help cool off housing 10, which may heat up (specifically, laser source 131), during use.

Housing element 11b is advantageously provided with an opening 15, in turn sealed by a water-proof and air-permeable seal. Differences in pressure between the inside and outside of housing 10 can occur due to the weather, but also due to housing 10 (or, more specifically, laser source 131) heating up during use. Providing such an opening 15 and seal allows for pressure to be levelled between the inside and the outside of housing 10, without risking water damage (e.g. due to moisture or condensation) to the (components arranged) inside of housing 10.

Figure 3 shows another embodiment of luminaire 1 according to the invention. Again, socket 20 is made of frame member 21 and fingers 22a, 22b, 22c. Housing 10 is again substantially spherical and received in the socket to form a ball-and-socket joint. The orientation of housing 10 in socket 20 in figure 3 is different from the one in figures 2A and 2B.

The exact orientation that is desired for housing 10 depends on many things. Examples are: the position of luminaire 1 on pole 100, the distance between pole 100 and road 102, the position line of light 105 1s desired on road 103, etc.

The ball-and-socket joint allows for housing 10 to be received in socket 20, while also being oriented in any relative rotational position. When housing 10 is received in socket 20, given that fingers 22a, 22b, and 22e do not clamp down on it, housing 10 can be moved freely in three dimensions, specifically three rotational dimensions, e.g. in the roll-, pitch-, and jaw-dimension. The ball-and-socket joint thus allows for accurately positioning housing 10, and thus for accurately aiming the line-laser 104 emitted by housing 10 - For example, such that line-laser 104 projects the line of light 105 onto road markings 103.

The skilled person will appreciate that effect can also be achieved — although to a lesser degree — with a luminaire that is only partially spherical. Said part of housing 10 may be a hemisphere, for example, or a further spherical segment or spherical cap. The skilled person will appreciate that only a part of housing 10 has to be shaped as only part of a circle.

While the embodiments of figures 2A, 2B, and 3 have annular windows (i.e. windows that go all the way around spherical housing 10), windows of other shapes are also possible. As long as they are of a shape and size, and arranged in a position, that allows for the beam of light emitted by laser source 131 and shaped by mirror 132 to exit housing 10 in a suitable direction and with suitable optical characteristics.

Figure 4 shows the inside of an embodiment of housing 10, again comprising disc 14a, laser source 131 and an optical element (i.e. a second optical element) comprised of a mirror 132. In this embodiment specifically, mirror 132 is attached, via screws 133a, 133b, to slots 16a, 16b provided in disc 14a. Light source 131 emits a laser beam that impinges onto mirror 132 after having passed a first optical element comprised of an optical lens. The mirror 132 shapes said laser beam into a diverging laser beam 104 (i.e. a laser beam having a sufficiently large angular width). The skilled person will appreciate that other beam-shapers than a lens and/or a mirror 132 can be used to achieve this.

As screws 133a, 133b can be fastened at any position in slots 16a, 16b, the distance between laser source 131 and mirror 132 is adjustable. Adjusting this distance, in turn, can be used to change the shape and size of the beam of light emitted by housing 10 and, as a consequence, the line length of the line projected on the surface. Mirror 132 may also be made repositionable via other means and in some embodiments, the distance between laser source 131 and mirror 132 is adjustable because laser source 131 can be repositioned, either instead of, or together with mirror 132. Instead of mirror 132, other beam forming means such as a lens or prism may be used as well.

Housing 10, received in socket 20, is placed in a particular orientation upon installation.

Ideally, this orientation does not change during normal use of the luminaire.

In figure 1, upon installation, housing 10 can generally be said to be emitting light downward. If its orientation changes, housing 10 may emit light into different, undesired directions.

Moreover, when luminaire 1 is used to delimit road markings, doing so in an inaccurate manner can also put traffic at risk as it is directed into the wrong direction.

To avoid the orientation from being changed, housing 10 may be provided with a substantially smooth outer surface and/or may have few to no ridges or protrusions on its outer surface. This limits the amount of grip external actors — i.e. people - get when trying to get a hold on housing 10. This reduces the risk of the position and/or orientation being changed by force.

In further embodiments, the contact area between housing 10 and socket 20 is preferably contiguous, or uninterrupted. Alternatively said, between housing 10 and socket 20 there is preferably only one contact area. This avoids, for example, hands or rope from wrapping completely around housing 10 and being able to pull on housing 10.

The embodiments shown in figures 2A, 3 and 5. housing 10 comprises each of the smooth outer surface, the substantially spherical shape, and the contiguous contact area with socket 20, and the luminaires shown are therefore surprisingly advantageous ones.

It is advantageous for the light source to turn off when its position and/or orientation does change. Sensors or sensing means 201 inside the spherical luminaire may indirectly monitor the position of the line by constantly sensing the position of the luminaire; i.e. the direction of the beam.

In case a certain deviation with respect to the initial position is sensed, the light source is switched off.

In some embodiments, the luminaire comprises sensing means 201 configured to sense such change and a controller or controlling means 200 configured to turn off the light source when a predetermined amount of change is detected. In the environment of claim 1, pole 100 may for example fall over due to an accident. Less maintenance is required for luminaires that also turn the light source back on again, when change earlier measured is undone. This helps avoid having to open up housing 10, which may require moving housing 10 out of the socket, or generally turn the light back on manually in any other way.

These advantages may be achieved by use of an accelerometer, configured to detect a change in position and/or orientation of housing 10. If the accelerometer detects a sufficiently high change in position (e.g. larger than a threshold) and light source is turned off. In some embodiments, the detected changes in position and/or orientation may be stored and integrated and/or summed over time, and a relative position may be determined based thereon. If a total amount of measured change is sufficiently close to zero (e.g. less than the threshold) it may be determined that housing 10 is in the desired position (i.e. housing 10 may be said to have returned to the same position as before), so the light source may be turned on again.

These advantages may also be achieved by use of a gyroscope or a magnetometer, configured to detect the orientation of housing 10. Upon installation, the desired orientation may be stored as a baseline orientation. Periodical measurements done by the gyroscope later in time can then be compared to this baseline orientation. If the difference is sufficiently high (e.g. larger than a threshold) the light source may be turned off. In some embodiments, after turning the light source off, the periodical measurements may continue. If the different between the current orientation and the baseline orientation is, again, sufficiently low (e.g. lower than the threshold) the light source may be turned on again.

While in the above examples it is said that the light source may be turned off, the light source may also be dimmed down to a level at which it will not, or 1s at least unlikely to confuse drivers or other traffic users. The skilled person will appreciate that ‘turning the light source back on’ after dimming it, refers to restoring the light source’s intensity to a predefined or earlier level.

A luminaire provided with any of the abovementioned sensors 201 may be provided further with communication means 202 that can send measurements to other devices such as a server, which may also monitor the orientation and position or function of said luminaire, or even multiple luminaires. A schematic representation of such an embodiment is shown in figure 6.

In the embodiment shown in figures 2A and 2B, luminaire 1 is releasably attached to pole 100. Specifically, socket 20 may be attached to existing poles 100. Figure 5 shows an embodiment in which pole 100 and socket 20 are integrally formed. On the left side of figure 5, luminaire 1 is shown from what may be called the front and on the right side of figure 5, luminaire 1 is shown from may be called the side.

In this embodiment, socket 20 has a bowl-shape, being another shape that allows for receiving spherical housing 10 as a ball-and-socket joint. In further embodiments, socket 20 may be provided by a depression-like shape. In further embodiments, socket 20 may be provided by a combination of the earlier mentioned shapes and/or means. In further embodiments, socket 20 may have the shape as shown in figure 5, and also be releasably attached to pole 100.

Claims

CONCLUSIONS

1. A lantern comprising: a rotatable body comprising: a housing defining an outer shape of the rotatable body, a portion of which is shaped like at least a portion of a sphere; and a light source arranged within the housing and comprising a diverging beam of light; a cup adapted to receive the portion of the housing shaped like at least a portion of a sphere as the ball in a ball joint: wherein said portion of the housing and the cup are complementary shaped to enable the rotatable body to be rotated along three orthogonal axes of rotation, thereby changing the field of illumination.

2. A lantern according to claim 1, wherein the shape of the part of the housing formed as at least a part of a sphere comprises a spherical segment and/or a spherical cap.

3. Lantern according to claim 1 or 2, wherein the shape of the part of the housing formed as at least a part of a sphere comprises a hemisphere, preferably a sphere.

4. A lantern according to claim 1, 2 or 3, wherein the bowl comprises at least one of: - a surface comprising a bowl- or cup-shaped recess; one or more projections adapted to at least partially enclose the lantern.

5. A lantern according to any preceding claim, wherein, when the rotatable body is received in the bowl, a contact area between the housing and the bowl is continuous.

6. A lantern according to any preceding claim, wherein the bowl is adapted to be in one of the following states: - a first state, in which the rotatable body can be removed from the bowl; - a second state, in which the rotatable body cannot be removed from the bowl, and in which the rotatable body can be rotated in the bowl;

- a third condition, in which the rotatable body cannot be removed from the bowl and in which the rotatable body cannot be adjusted in its orientation within the bowl.

7. Lantern according to any of the preceding claims, wherein the light source is arranged to emit a light beam, and preferably is arranged to emit a line laser.

8. A lantern according to any preceding claim, wherein the lantern is designed to project a line of light onto a surface, for example a traffic surface, when in operation.

9. A lantern according to any preceding claim, further comprising at least one optical element, for example at least one of a lens element and a reflective element, arranged in the housing, the at least one optical element being adapted to receive light from the light source and to emit a diverging light beam capable of projecting a line of light onto a surface, for example a traffic surface such as a road.

10. A lantern according to any preceding claim, wherein the light source comprises: a laser source adapted to emit a laser beam, and; one or more optical elements, adapted as a beam shaper, such as a prism or a mirror, adapted to shape the laser beam into a diverging light beam.

11. A lantern according to any preceding claim, wherein the housing comprises a transparent window through which the illumination field extends.

12. A lantern according to any preceding claim comprising a laser source and a beam former, the laser source and beam former being disposed within the housing and being arranged to emit a diverging laser light beam through the transparent window.

13. A lantern according to any preceding claim, wherein the rotatable body further comprises: detection means adapted to detect a change in a position or orientation of the lantern;

control means adapted to dim or switch off the light source when a change in the position or orientation of the rotatable body is detected.

14. A lantern as claimed in claim 13, wherein the detection means are means adapted to sense a change in position and/or orientation of the rotatable body, such as an accelerometer, a gyroscope or a magnetometer, and wherein the control means are further adapted to dim or switch off the light source when a total amount of change in position and/or orientation exceeds a first predetermined threshold value.

15. A lantern according to claim 13 or 14, wherein the detection means are means adapted to measure an orientation of the rotatable body, such as a gyroscope, and wherein the control means are further adapted to store a baseline orientation of the rotatable housing, periodically measure the orientation of the rotatable housing, and dim or switch off the light source when a difference between the baseline orientation and the measured orientation exceeds a second predetermined threshold value.

16. A lantern according to any one of claims 13 to 15, wherein the control means are further arranged to, after dimming or switching off the light source, switch the light source on again when an inverse of the change in the position or orientation of the rotatable body is detected.

17. A lantern according to any one of claims 13 to 16, wherein the control means are further arranged to, after dimming or switching off the light source, switch the light source on again when the total amount of change in position and/or orientation is less than the first predetermined threshold value.

18. A lantern according to any one of claims 13 to 17, wherein the control means is further arranged to periodically measure the orientation of the rotatable housing after dimming or switching off the light source, and to switch the light source on again when the difference between the baseline orientation and the measured orientation is less than the second predetermined threshold value.

19. A lantern according to any preceding claim, wherein the bowl is further adapted to be releasably attached to a support such as a stand or a pole.

20. System for projecting a light line onto a surface, for example a traffic surface, the system comprising: - a lantern according to any one of the preceding claims; - a support for supporting the lantern, the bowl of the lantern being integral with or firmly connected to the support.

21. System according to claim 20, wherein the support is a post or pole to be anchored in the ground,

22. A support, for example a pole, the support comprising a cup for supporting the lantern, the support comprising the cup adapted to receive the part of the housing of the lantern according to any of claims 1 to 19.