Luminaire and Method for Temperature Determination

Abstract

A luminaire comprises at least one light emitting diode (LED) as a light source. Such LED comprises a limited light emitting angle for the emitted light radiation. Outside of the light emitting angle, an infrared sensor is assigned to the light source for detecting its temperature.

Claims

1. A luminaire (1) with at least one light emitting diode (LED) (2) as a light source (2), which LED (2) has a limited light emitting angle (4) for the emitted light radiation (5), wherein outside of this light emitting angle (4) an infrared sensor (6) is assigned to the light source (3) for determining its temperature.

2. The luminaire according to claim 1, wherein the infrared sensor (6) is essentially arranged orthogonal to a medium emitting direction (7) next to the light source (3).

3. The luminaire according to claim 1, characterized in that said light source (3) is an LED-spot light, an LED-strip, or an LED-ribbon.

4. The luminaire according to claim 1, wherein the infrared sensor (6) is connected to an evaluation/control means (8) for temperature determination and control of the light source (3).

5. The luminaire according to claim 1, wherein the infrared sensor (6) is arranged within a luminaire housing (9).

6. The luminaire according to claim 1, wherein the evaluation/control means (8) has a pre-set maximum temperature threshold as a switch-off value for the light source (3).

7. The luminaire according to claim 1, wherein the infrared sensor (6) is screened with respect to ambient heat radiation.

8. The luminaire according to claim 1, wherein a second infrared sensor (10) is assigned to the infrared sensor (6) for detecting and compensation of ambient heat radiation.

9. The luminaire according to claim 1, wherein the infrared sensor (6, 10) is adjustably arranged.

10. A method for temperature control of at least one LED (2) as a light source (3) of a luminaire (1) with the following steps: i) arranging an infrared sensor (6) outside a light emitting angle (4) of the light source (3); ii) measuring a heat radiation of the light source (3) by such infrared sensor (6), and iii) evaluating the infrared signal for determining temperature of the light source (3).

11. The method according to claim 10, characterized by the further step of: switching off of the light source (3) in case the detected temperature value is higher than a pre-set maximum temperature threshold.

12. The method according to claim 10, characterized by the step of: screening the infrared sensor (6) with respect to ambient heat radiation.

13. The method according to claim 10, characterized by the further step of: measuring the ambient heat radiation by a second infrared sensor (10) for compensation of ambient heat.

14. The method according to claim 10, characterized by the further step of: assigning the infrared sensor (6) to an LED-spot light, an LED-strip, or an LED-ribbon as a light source (3).

15. The method according to claim 10, characterized in that a light guide for example in a form of a light collecting rail is assigned to each LED of a plurality of LEDs for simultaneously detecting the emitted infrared parts of all LEDs, wherein at a corresponding exit end of the light guide the infrared sensor is isolated with respect to ambient radiation.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0022] In the following an advantageous embodiment of the invention will be described with respect to the FIGURES.

[0023] FIG. 1 is a principle illustration of a luminaire with an infrared sensor according to the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0024] In FIG. 1, a part-sectional view of luminaire 1 with a temperature determination of a light source according to the invention is illustrated. Luminaire 1 has a luminaire housing 9 and a light source 3 arranged therein. A corresponding light exit opening of the luminaire or the luminaire housing is not further illustrated. However, this can be arranged in a normal way in the direction of the light radiation emitted by the light source 3. Moreover, in FIG. 1, only one light source in the form of a light emitting diode (LED) 2 is illustrated. Of course, several such LEDs may be arranged in the form of strips or ribbons.

[0025] The LED 2 generally consists of a printed circuit board 12 with a corresponding semi-conductor and a lens means 11 for dissipating or collecting the emitted light. With such an LED 2, corresponding light rays 5 will be emitted in a particular space area which is defined by the illustrated emitting angle 4. This angle depends on the LED and the corresponding lens means 11, for example 15 to 120. A medial emitting direction 7 which, as a rule, extends perpendicular from the light source 3, is determined by the corresponding emitting angle 4.

[0026] By use of the light source or by radiation directed to the light source from the outside, see for example, sun radiation, the temperature of the LED will rise. In this connection, it has to be considered that, for example, the light flux amount of an LED strongly depends on the barrier layer temperature. The higher the temperature of the LED, the smaller the light flux is, the shorter the functional life becomes, and a change in the light color may result. For the corresponding cooling, a cooling device 13 is assigned to the LED, which can, for example be a ribbed cooling body, and active cooling, for example, also with cooling fluid or the like. In case the LED is heated, it corresponds essentially to a black body which emits corresponding black body radiation during heating in addition to the light radiation. Such a black body radiation has a very characteristic spectrum, which only depends upon the temperature of the corresponding body. In the temperature range according to the invention, this black body radiation is in the infrared range.

[0027] Thus, according to the invention, an infrared sensor 6 is assigned to the light source 2, which sensor detects such black body radiation in the infrared range.

[0028] By the arrangement of the cooling device 13, such corresponding black body radiation, which corresponds to the temperature of the light source 2, is essentially emitted only an upper half space of the cooling device 13, see reference numeral 14, which designates the emitting angle of the black body radiation.

[0029] In the area of this emitting angle, the infrared sensor 6 is arranged, such that the temperature of the light source 2 can be detected by this sensor.

[0030] Infrared sensor 6 can be arranged in such a way that it is arranged within the radiation area of the black body radiation, which means of the heat radiation, but is not arranged in the area of the light radiation, see the corresponding emitting angle 4.

[0031] The infrared sensor 6 is connected to an evaluation/control means 8. By this means the corresponding infrared signals are received and are converted into temperature values. The corresponding temperature values are in particular compared to a maximum temperature threshold. In case the detected temperature the light source 2 is higher than this maximum temperature threshold, the luminaire in particular the light source, can be switched off by the evaluation/control means.

[0032] It was already said that a corresponding light source 2 may also be passively heated by radiation from the outside, see for example sun radiation. This heating might negatively influence the light source, which may endanger its operation. Also in such a case, the temperature can be detected by the infrared sensor 6 and result in the initiating of an active cooling of the light source by the evaluation/control means.

[0033] The corresponding heat radiation from the outside corresponds to an ambient heat radiation, which will be screened during temperature measurement of the light source or will be considered during temperature measurement. For suppressing such ambient heat radiation, it is possible to for example, assign a screening to the infrared sensor 6 in the form of a covering, a foil, a cooling body or the like. This will guarantee that the ambient heat radiation does not directly reach the infrared sensor 6.

[0034] It is also possible that the ambient heat radiation will be detected by a further second infrared sensor 10. This is, in particular, directed to the ambient heat radiation and detects same. By the measurement values of both infrared sensors 6 and 10, then a compensation of the ambient heat radiation during detecting of the temperature of the light source may be attained. Both infrared sensors transmit corresponding sensor values to the evaluation/control means 8.

[0035] It is further to be noted that in FIG. 1 essentially only one light source is illustrated as well as only one infrared sensor 6 or infrared sensor 10, respectively. Of course, it is possible to use several light sources with just one infrared sensor 6 or also in combination with several of such infrared sensors 6. This is also valid for the second infrared sensor 10, from which also several might be used, to detect ambient heat radiation from the outside coming from different regions.

[0036] According to the invention, sure detection of temperature of the corresponding light source is performed to prevent, for example, overheating of same. Thus, the light output, functional life and also the light color are protected in view of a negative influence by overheating the light source. Such a temperature measurement has a particular advantage in hazardous areas, to avoid ignition by such overheated light source.