LIGHTING DEVICE AND METHOD IN CONNECTION WITH A LIGHTING DEVICE

Abstract

 A lighting device and a method in connection with a lighting device, the lighting device comprising one or more light sources (1) and a structural element (3) configured to transmit light. The lighting device further comprises a light sensor (2) arranged in the lighting device to receive light of said one or more light sources (1) that is reflected from the structural element (3) configured to transmit light, and control electronics connected to the one or more light sources (1) and to the light sensor (2) and configured to determine the light output by said one or more light sources that is reflected to the light sensor from the structural element (3) configured to transmit light, and to control the operation of said one or more light sources in response to the determined light.

Description

FIELD OF THE INVENTION

[0001] The invention relates to lighting devices, and specifically to exit and emergency lights.

BACKGROUND OF THE INVENTION

[0002] Exit and emergency lights are lighting devices used in facilities for safety of the facility especially in emergencies. The purpose of exit lights is to indicate an emergency exit for people in the facility in order to guide them out of the facility in case of emergency. Typically, exit lights are provided with a symbol including an indicator arrow attached to a cover of the lighting device or the like, to indicate the emergency exit from the facility. Emergency lights, on the other hand, are lighting devices ensuring sufficient illumination in a facility in case of emergency. The exit as well as emergency lights must meet the criteria imposed on them in terms of operational reliability and lighting capacity. These criteria include, for example, operation in case of a power outage, sufficient surface brightness of the exit light, and sufficiently high illuminance output by the emergency light.

[0003] In exit lights and emergency lights, different elements have been used for producing the lighting, as they are purposed for different uses. Emergency lights are required to illuminate the environment, whereas the purpose of exit lights is to illuminate the indicator symbol of the lighting device. If the same light output is used for an exit and an emergency light, the surface brightness of the exit light will become unnecessarily high when the illumination output by the emergency light would be sufficient. Herein, the same light output refers to a light output apparatus, such as an LED board, outputting an equal luminous flux from the light source. Correspondingly, if the luminous flux from the light source is sufficient to provide appropriate illumination for the exit light, the luminous flux of this light source will be too low in connection with the emergency light.

[0004] Because of different requirements in terms of lighting output by the light source, separate apparatuses have been used in exit lights and emergency lights to output the light for each purpose. However, it would be advantageous if the same light output apparatus, such as an LED board, could be used in a plurality of lighting devices of different types.

BRIEF DESCRIPTION OF THE INVENTION

[0005] The object of the invention is to provide a lighting device and a method in connection with a lighting device so as to be able to solve the above mentioned problem. The object of the invention is achieved with a lighting device and a method characterized by the features of the independent claims. The preferred embodiments of the invention are presented in the dependent claims.

[0006] The invention is based on a light output apparatus arranged to automatically recognize the type of the lighting device, and based on the recognition, to adjust the luminous flux being output so as to be suitable for the recognized lighting device. A lighting pattern output by the lighting device may also be controlled based on the recognition. The recognition is based on the amount of light reflected back from a cover of the lighting device towards the light output apparatus. In exit lights, it is known that a picture is used in connection with the cover of the lighting device, and this picture reflects significantly more light back to the interior of the lighting device than the cover in connection with an emergency light, which is for example clear. When the type of the lighting device has been recognized, the luminous flux is set to a value that is required for this particular lighting device. In addition to the luminous flux, it is possible to switch on light sources provided with different kinds of optics, depending on the operating mode, in order to provide a lighting pattern that is appropriate for the purpose.

[0007] The advantage of the lighting device and the method for a lighting device according to the invention is that the light output apparatus may be used in an exit light as well as in an emergency light, and so the number of parts that need to be stored can be reduced. Further, installing the lighting device according to the invention and setting it up for operation is simple, because separate procedures are not required for configuring the light output apparatus during the installation.

BRIEF DESCRIPTION OF THE FIGURES

[0008] The invention will now be described in more detail in connection with preferred embodiments, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of an embodiment of the invention in connection with an exit light;

Fig. 2 is a schematic diagram of an embodiment of the invention in connection with an emergency light;

Fig. 3 is a flow chart presenting the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Fig. 1 is a cross-sectional view of an implementation of one embodiment of the invention in connection with an exit light. According to the invention, the lighting device comprises one or more light sources 1, such as LED light sources, and a structural element 3 configured to transmit light. The structural element configured to transmit light, such as a cover of the lighting device, is disposed at least partly in front of the light source. Typically, the cover is attached to a lighting device body 5 or the like, the light source being entirely enclosed by the cover and the body.

[0010] The lighting device shown by Fig. 1 further comprises a light sensor 2 arranged in the lighting device to receive light of the one or more light sources that is reflected from the structural element 3 configured to transmit light. Fig. 1 schematically shows how some of the light output by the light source 1 reflects back to the interior of the lighting device and hits the light sensor 2. Herein, a light sensor refers to a component or a device having electrical properties that change by the effect of the light focused thereon. Such components may be for example photodiodes or phototransistors. The light sensor 2 may also be a component that is adapted to receive a specific wavelength or wavelength band to avoid incorrect recognition. In this case the light sensor receives the light wavelength or wavelength band that is output with the light source in the lighting device.

[0011] The lighting device according to the invention comprises control electronics connected to said one or more light sources and to the light sensor. The control electronics are configured to determine the light output by said one or more light sources that is reflected to the light sensor from the structural element configured to transmit light. The light sensor is thus electrically part of the control electronics for determining the amount of reflected light. In other words, the control electronics together with the light sensor form an electric circuit that outputs a signal within said circuit as a function of the amount of light, which signal may be further utilized in the control electronics.

[0012] In the lighting device of the invention, the control electronics are further configured to control the operation of said one or more light sources in response to the determined light.

[0013] Fig. 1 shows that the structural element 3 configured to transmit light comprises a pictogram 4, whereby the lighting device is formed as an exit light. In the example of Fig. 1, the pictogram is disposed in the interior of the cover 3 of the lighting device. However, the pictogram may also be provided on the exterior of the cover as a separate film, or it may be formed as part of the cover. The pictogram represents, for example, an exit. The cover may also have pre-installed holders on which the pictogram may be secured.

[0014] Fig. 2 corresponds to the example of Fig. 1, except that the pictogram is not provided in connection with the structural element 3 configured to transmit light. The cover 3 is a substantially clear cover, the lighting device of Fig. 2 thus being for example an emergency light for the purpose of lighting its surroundings. The pictogram of Fig. 1 forms an obstruction for part of the light output by the light source, whereby more light is reflected towards the light sensor than in the example of Fig. 2 where there is no pictogram arranged in connection with the cover. In the lighting device according to the invention, as the control electronics are configured to control the operation of the light source in response to the determined light, the control electronics together with the light sensor may recognize the type of the lighting device based on the light reflected from the structural element configured to transmit light.

[0015] When the light sensor detects together with the electronics it is connected to that the amount of reflected light is greater than a specific limit, it may be concluded that the lighting device is provided with the pictogram, the lighting device thus being an exit light. However, if the amount of reflected light is smaller than a specific limit, it may be concluded that the lighting device is an emergency light in which the structural element configured to transmit light does not have the pictogram.

[0016] According to the invention, the control electronics are configured to control the operation of said one or more light sources in response to the determined light. According to a preferred embodiment of the invention, the control electronics are configured to increase the luminous flux output by the one or more light sources when the amount of the determined reflected light is smaller than a specific limit. When the amount of reflected light is small, the lighting device is an emergency light for the purpose of providing lighting in its surroundings.

[0017] According to an embodiment of the invention, the control electronics are configured to decrease the luminous flux output by the one or more light sources when the amount of the determined reflected light is greater than a specific limit. On the basis of a small amount of reflected light, the type of the lighting device may be concluded to be an exit light. An exit light need not provide lighting in its surroundings, but it only needs to output sufficient surface brightness for the exit sign.

[0018] According to a preferred embodiment of the invention, the amount of reflected light is determined in connection with switching-on of the lighting device. In other words, when the lighting device is switched on it is determined based on the reflected light whether it is an exit light or an emergency light. When the type of the lighting device has been determined, the lighting device is controlled so as to provide lighting according to the type of the lighting device, and then the lighting device is left on to provide such lighting. When the type of the lighting device is determined right after the lighting device has been switched on, the light sensor is not necessarily used during the time of providing the lighting. However, it is also possible to use the light sensor during the operating time of the lighting device, and the amount of reflected light measured by this light sensor may be used for adjustment or control purposes.

[0019] According to one embodiment of the invention, the control electronics are configured to pulse the light output by said one or more light sources, to determine the pulsed reflected light, and to control the operation of said one or more light sources in response to the determined light. By means of the lighting device according to the embodiment, an incorrect recognition of the operating mode caused by an external light source may be avoided. When light output by the light sources is pulsed, the reflected light must be pulsed correspondingly. One possible way to implement the pulsing is presented in document FI116356, wherein the effect of external light on measurement may be eliminated by calculating a difference between illuminations output at two different intensities, whereby the external light does not have an effect on the difference variable. According to the embodiment of the invention, in other words, pulsing ensures that the determined light originates from one or more light sources of the same lighting device.

[0020] The light sources of the lighting device are switched on at a known light output, so that the comparison of the reflected light with the preset limit value may be carried out. The light sources may also be switched on, for example, at full luminous flux, whereby on the basis of the amount of reflected light, lighting is turned down when it is detected that the lighting device is an exit light. When it is detected on the basis of the reflected light that the lighting device is an emergency light, lighting is allowed to remain at the original value.

[0021] The known light output of the light sources may also be, for example, 50% of the maximum light output or luminous flux of the light sources. A suitable limit value for carrying out the recognition of the type of the light source may be determined, for example, by experiments.

[0022] Adjusting of the luminous flux of the light sources may be done by means of an electronic circuit providing a voltage or current supplying the one or more light sources, the level of which voltage or current may be adjusted. When the one or more light sources are LED components, the luminous flux may be varied by varying the current flowing through the LED components. The luminous flux output by LED components is almost directly proportional to the current flowing through the component. The control electronics in the lighting device either include as such a connection for controlling the LED components, or control such connection on the basis of the reflected light indicated by the sensor.

[0023] As discussed above, the amount of reflected light output by the light source is preferably determined in connection with switching-on of the lighting device, i.e. as soon as the lighting device is connected for operation. For this purpose the control electronics of the lighting device include, for example, a timer circuit, under the control of which, initially, the amount of reflected light is determined. After a determined time the electronic circuit performs the comparison with the preset limit and switches to a continuous operating mode using lighting selected on the basis of the comparison.

[0024] According to one embodiment of the invention, when it has been detected that the lighting device is an emergency light, the control electronics of the lighting device also switch alternative light sources on in order to provide a lighting pattern optimized for use in emergency lighting. Thus, during the time of determining the type of the lighting device, all of the light sources in the lighting device are not necessarily switched on; instead they are switched on only if it is detected that the lighting device is an emergency light. Such additional light sources to be switched on may be provided, for example, with application specific optics.

[0025] The lighting device according to one embodiment includes, for example, a housing, a cover and an LED board as a light source. An LED board refers to a circuit board or the like comprising one or more LED light sources and electronic circuits connected thereto. The LED board is disposed in the interior of the cover, and it also includes a light sensor directed towards the cover. On the inner surface of the cover, a place is arranged for example for a pictogram formed by a plastic film. For exit sign use, the lighting device is provided with the pictogram, whereas for use as an emergency light, the pictogram is not included. Fig. 1 and 2 illustrate that the LED light source and the light sensor are disposed on the same circuit board.

[0026] The flow chart of Fig. 3 represents a method according to one embodiment of the invention in connection with a lighting device. According to the method, light is output 31 by one or more light sources, and light of said one or more light sources that is reflected from a structural element configured to transmit light is received 32 by a light sensor. Further in the method, the light output by said one or more light sources that is reflected from the structural element configured to transmit light is determined 33, and the operation of said one or more light sources is controlled 34 in response to the determined light. The method may be carried out with the lighting device according to the invention, and the method carried out with the lighting device and some of its embodiments have been described above in connection with the lighting device.

[0027] Further, the information obtained from the light sensor may be used to automatically set the lighting device to operate continuously or non-continuously. Typically, exit lights operate continuously, i.e. they are continuously on. Emergency lights, on the other hand, may operate non-continuously, such that they are only switched on in a battery-backed mode, also when power supply from the grid is lost.

[0028] The invention has been described above particularly with reference to an embodiment where the one or more light sources used are LED components. However, it is obvious that the light source used is freely selectable without affecting the implementation of the invention. The features related to control of the light sources have not been described in detail in connection with the invention. In the field of lighting devices it is known per se that the luminous flux output by light sources may be adjusted. The control electronics in the lighting device have also been described on a general level. The purpose of the control electronics in the invention is to carry out the determination of the reflected light together with the light sensor, and to control the luminous flux output by the light sources of the lighting device as appropriate, considering the type of the lighting device detected based on the amount of reflected light as described above.

[0029] As to the structure of the lighting device, reference is made above to Fig. 1 and 2 presenting the structures that illustrate the invention. It is obvious for a person skilled in the art that the structure of the lighting device may vary.

[0030] It is obvious for a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, but may vary within the scope of the claims.

Claims

1. A lighting device, comprising one or more light sources (1) and a structural element (3) configured to transmit light, characterized in that the lighting device further comprises
a light sensor (2) arranged in the lighting device to receive light of said one or more light sources (1) that is reflected from the structural element (3) configured to transmit light, and
control electronics connected to the one or more light sources (1) and to the light sensor (2), and configured to determine the light output by said one or more light sources (1) that is reflected to the light sensor (2) from the structural element (3) configured to transmit light, and to control the operation of said one or more light sources (1) in response to the determined light.

2. The lighting device according to claim 1, wherein the control electronics are configured to decrease the luminous flux output by the one or more light sources (1) when the amount of the determined reflected light is greater than a predefined limit.

3. The lighting device according to claim 1 or 2, wherein the control electronics are configured to increase the luminous flux output by the one or more light sources (1) when the amount of the determined reflected light is smaller than a predefined limit.

4. The lighting device according to claim 3, wherein the control electronics are configured to switch at least one other light source (1) on when the amount of reflected light is smaller than a predefined limit.

5. The lighting device according to any one of the preceding claims 1 - 4, wherein the control electronics are configured to set the luminous flux output by said one or more light sources (1) to a predefined value in response to the amount of the determined reflected light.

6. The lighting device according to any one of the preceding claims 1 - 5, wherein the control electronics are configured to control the operation of said one or more light sources (1) in response to the determined light in connection with switching-on of the lighting device, preferably right after it has been switched on.

7. The lighting device according to any one of the preceding claims 1 - 6, wherein the one or more light sources (1) are LED components disposed on the same circuit board with the light sensor (2).

8. The lighting device according to any one of the preceding claims 1 - 7, wherein the structural element (3) configured to transmit light is a cover of the lighting device.

9. The lighting device according to claim 8, wherein the cover (3) of the lighting device comprises a pictogram (4) and the lighting device is an exit light.

10. The lighting device according to claim 8, wherein the lighting device is an emergency light.

11. The lighting device according to claim 8, wherein the cover (3) of the lighting device is configured to receive a pictogram (4).

12. The lighting device according to any one of the preceding claims 1 - 11, wherein the control electronics are configured to pulse the light output by said one or more light sources (1), to determine the pulsed reflected light, and to control the operation of said one or more light sources (1) in response to the determined light.

13. The lighting device according to any one of the preceding claims 1 - 12, wherein the control electronics are configured to continuously determine the light output by said one more light sources (1) that is reflected to the light sensor (2) from the structural element (3) configured to transmit light.

14. A method in connection with a lighting device, the lighting device comprising one or more light sources (1) and a structural element (3) configured to transmit light, characterized in that the method comprises the steps of
outputting (31) light by the one or more light sources (1),
receiving (32), by a light sensor (2), light of said one or more light sources (1) that is reflected from the structural element (3) configured to transmit light,
determining (33) the light output by said one or more light sources (1) that is reflected from the structural element (3) configured to transmit light, and
controlling (34) the operation of said one or more light sources (1) in response to the determined light.

15. The method according to claim 14, comprising a step of decreasing the luminous flux output by the one or more light sources (1) when the amount of the determined reflected light is greater than a predefined limit.

16. The method according to claim 14 or 15, comprising a step of increasing the luminous flux output by the one or more light sources (1) when the amount of the determined reflected light is smaller than a predefined limit.

17. The method according to claim 16, wherein at least one other light source (1) is switched on when the amount of reflected light is smaller than a predefined limit.

Drawing