EP2333404A1 - Light emitter with diffuser - Google Patents

Abstract

The illuminating unit (1) has a light source in the form of light emitting diodes (2), where one or multiple plate-shaped elements are arranged with electrically adjustable transparency in beam path. The elements have liquid crystals. The light emitting diodes are arranged in a matrix shape or honeycomb-shape.

Description

The invention relates to a lighting device, in particular in the form of a beacon for TV studios, stages, etc. The lighting device comprises a light source.

At such Leuchtstrahler high demands are made today. For example, considering the use of object spotlights in TV studios, it is necessary to illuminate certain areas with high brightness while leaving other areas in the dark. Depending on the nature of the desired TV recording also different characteristics of the emitted light are desired. For a detailed view of a small section of the stage, the light should hit this detail as concentrated as possible. On the other hand, in the case of an overview shot of the stage as a whole, a planar illumination is required.

According to the classical procedure, strong halogen lamps are used for such purposes, the lighting area being optionally restricted by means of diaphragms or lens systems. For the change between concentrated lighting and surface lighting diffusers are used, which can be selectively inserted into the illumination beam path and removed from it. Without a diffuser, the light from the object spotlight hits concentrated on a small section of the stage. If the diffuser is introduced into the beam path, the light is scattered in the most different directions, so that a planar illumination is generated. When changing between the two states, the diffuser is moved mechanically.

The invention is based on the object to present such a lighting device that allows fast switching between different lighting conditions. Based on the above-mentioned prior art, the object is achieved by the features of the independent claim. Advantageous embodiments can be found in the subclaims.

According to the invention, a plate-shaped element is arranged in the beam path of the light source. The plate-shaped member comprises two transparent plates enclosing a liquid crystal layer therebetween. The plate-shaped element can assume two states. In a first state, the liquid crystals are disordered. In a second state, the liquid crystals are aligned with each other. For switching between the states, an electric voltage is applied to the liquid crystal layer.

A beacon refers to a high-intensity illumination device, with which an object can be illuminated from a distance. The light emanating from the illuminator can be adjusted so that it is concentrated on the object, while other areas are not illuminated. Such object radiators can be used in particular in TV studios, theaters, stages. Possible are also uses in the lighting of buildings, shop windows, showcases and the like.

The liquid crystals in the plate-shaped element have the property that they are translucent only in certain directions. When the liquid crystals in the liquid crystal layer are disordered, the light coming from the light source is scattered and directed in various directions. Even if the liquid crystals are disordered, a large part of the incident light may pass through the plate-shaped member. The exiting light is diffuse, the plate-shaped element thus acts like a frosted glass. In the lighting device according to the invention, the plate-shaped element in this state acts as a diffuser.

When the liquid crystals in the liquid crystal layer are aligned with each other, the light emitted from the light source can pass directly through the plate-shaped member. The plate-shaped element in this state is transparent in the sense that one can recognize an object through the plate-shaped element. In this state of the plate-shaped element, therefore, the light from the light source is passed directly to the object. Regularly, the liquid crystals are disordered in the initial state and they align after applying a voltage. The plate-shaped elements thus have an electrically adjustable transparency. As such, the plate-like elements are known and commercially available. To distinguish are the plate-shaped elements according to the invention of so-called light locks, which are based on liquid crystals. Characteristic of light locks, like them for example, used in LCD displays is a state in which the light is not allowed to pass.

With the diffuser according to the invention it is possible to switch the lighting device almost instantaneously between a direct illumination and a diffuse illumination. In particular, it is no longer necessary to move the diffuser mechanically into or out of the beam path.

The transparent plates of the plate-shaped elements are preferably arranged substantially parallel to each other. The plates may be made of glass or other material such as plastic. The material can be rigid or flexible. If the plates are flexible, the plate-shaped element as a whole is flexible. The plates can be even. Also possible are embodiments in which the plates are curved.

The plate-shaped elements are often not very heat resistant. When using a light source that emits much heat, such as an incandescent lamp or a halogen lamp, there must be some clearance between the diffuser and the light source so that the diffuser is not damaged by the heat. An advantage is a light source that emits little heat, such as an LED. The diffuser can then be arranged at a small distance from the light source, for example less than 20 cm, preferably less than 10 cm. The light source may include a plurality of LEDs. The LEDs can be arranged two-dimensionally, for example in the form of a matrix or honeycomb.

In order to further reduce the risk of heat damage, cooling means for the plate-shaped elements may be provided.

The LEDs preferably comprise a collimator optic arranged in front of the luminous substrate, so that the light is emitted in a narrow cone of rays. The collimator optics of the LED should be distinguished from other lenses that the illumination device may possibly have.

In order to expose the liquid crystals to an electrical voltage, an electrically conductive layer may be formed on each side of the liquid crystal layer. Between the two electrically conductive layers, a voltage source can be provided. In the simplest case, a switch is arranged between the voltage source and the electrically conductive layers, with which the voltage can be switched on or off. By operating the switch, it is possible to switch between a state of the plate-shaped member in which the liquid crystals are disordered and a state in which the liquid crystals are aligned with each other. In an advantageous embodiment, a voltage regulator is provided with which a plurality of different voltages can be applied between the electrically conductive layers. It is then possible to switch in several stages or even continuously between a completely disordered and a fully aligned state of the liquid crystals. For the diffuser this gives rise to the possibility of intermediate states between the very transparent and the very diffuse state. The voltage regulator may be configured to adjust DC voltage or AC voltage, the adjustment preferably can be steplessly. The term voltage regulator also encompasses devices which generate different voltage profiles, for example by generating a specific average voltage by rapid switching back and forth. Experiments have shown that rapidly changing voltages can cause a faster reaction of the liquid crystals.

Occasionally, it is desired that a particular object be permanently subject to direct illumination and that the illumination be varied only in the environment of the object. It may therefore be expedient if the plate-shaped elements only partially cover the light emitted by the light source. It can then be adjusted whether the permanent direct illumination is supplemented by further direct light or by diffused light. One application for this could be the lighting of a showcase, which is to be permanently illuminated directly, while in the environment different illuminations are desired, for example, depending on the additional incident daylight.

The illumination device according to the invention can be set up in such a way that even further properties of the light conducted onto the object can be influenced. These properties may be, for example, the color of the light or the color temperature. For this purpose, the light source can have a plurality of separate light regions which emit light with different properties. Optionally, the light areas may be created by filters having different properties. For example, a first light region of the light source can be warm-white and a second light region of the light source can be cold-white Emit light. It is also possible that the different light areas emit light in different colors. In order to be able to influence the properties of the light, the diffuser can comprise a plurality of mutually separate sub-areas, which can be controlled separately from one another. The partial surfaces may be formed on a single plate-shaped element or on a plurality of plate-shaped elements. The partial areas can be assigned to the light areas. Preferably, a partial surface of the diffuser is arranged in front of each light region.

By separate control of the partial surfaces of the diffuser, the properties of the light can now be influenced. For example, if the partial area arranged in front of the warm-white light area is in the clear state (liquid crystals aligned) and the partial area arranged in front of the cold-white light area is in the diffuse state (liquid crystals disordered), the object is primarily illuminated with warm white light. If the object is then to be illuminated cold-white, then a reverse control of the partial surfaces is required. If the voltage applied to the faces is changed simultaneously and in opposite directions, it is possible to switch between warm white light and cold white light without the brightness changing significantly. Also any intermediate states between warm-white light and cold-white light can be adjusted in this way. Corresponding transitions are possible between light of different colors.

Further optical effects can be achieved if the light emerging from the partial surfaces of the diffuser is then superimposed concentrically. It will For example, it is possible to generate a white light beam from the light of a red, a green and a blue LED. If a color is switched from direct illumination to diffuse illumination by changing the voltage on the plate-shaped element, a corona of the relevant color is formed around the center, while the color in the center is present only to a lesser intensity. Such an effect is desirable for certain TV recordings. In an advantageous embodiment, the illumination device according to the invention therefore comprises an optical element, with which the light emerging from the partial surfaces can be superimposed.

The illumination device according to the invention can be equipped with further lens elements which are arranged in the beam path and influence the illuminated area. Thus, the illumination angle or the illumination field can be varied and adjusted to the actual needs, see DE 20 2007 008 430 U1 , The electrically controllable plate-shaped elements can be arranged directly behind the LEDs, ie between the LEDs and the lens systems. In another embodiment, which has in the beam path successively arranged lenses or lens systems, the electrically controllable plate-shaped elements between the lenses or lens systems are arranged. Also possible are embodiments in which the plate-shaped elements are arranged by the light source on the other side of the lens system.

Especially in TV studios and on stages it is often required that the lighting can follow moving objects. It can be provided for this purpose a suspension for the lighting device, which makes it possible that the lighting device can be moved relative to a rigid structure. As a rigid structure in this sense, for example, a tripod is considered.

The invention further relates to an arrangement comprising a lighting device according to the invention and a wall, wherein the lighting device is arranged such that the light emitted by the lighting device strikes the wall at an acute angle. This is particularly the case with walls that serve as a background in TV studios. In this case, a lighting device is arranged at a small distance from the plane of the wall, which illuminates obliquely on the wall. For the TV recordings, it is important that the area that can be seen in the recording, evenly lit. With the illumination device according to the invention, it becomes possible to vary between a concentrated illumination of a small area and a uniform illumination of a larger area. In addition, the lighting device can be adjusted so that even in the near range, the different colors of a multi-colored light source are not individually visible.

An acute angle is understood in particular to mean an angle of less than 20 °, preferably less than 10 °. The angle refers to the center beam of the illumination. The lighting device can be arranged on the same side of the wall on which the TV camera is arranged. The light is then reflected off the wall. The application is also possible with translucent walls. The lighting device is then placed on the other side of the wall and the light passes through the wall.

Fig. 1:

eine erfindungsgemäße Beleuchtungseinrichtung in Verwendung;

Fig. 2:

eine schematische Darstellung einer erfindungsgemäßen Beleuchtungseinrichtung;

Fig. 3:

eine schematische Darstellung der Funktionsweise eines Diffusors;

Fig. 4:

eine schematische Darstellung eines Diffusors;

Fig. 5:

die Beleuchtungseinrichtung aus Fig. 2 in einer Ansicht von vorne;

Fig. 6:

die Ansicht gemäß Fig. 5 bei einer anderen Ausführungsform der Erfindung;

Fig. 7:

die Ansicht gemäß Fig. 4 bei einer anderen Ausführungsform der Erfindung;

Fig. 8:

die Ansicht gemäß Fig. 4 bei noch einer anderen Ausführungsform der Erfindung;

Fig. 9:

eine schematische Darstellung einer alternativen Ausführungsform;

Fig. 10:

eine weitere Ausführungsform der Erfindung; und

Fig. 11:

eine Ausführungsform einer erfindungsgemäßen Anordnung.

The invention will now be described by way of example with reference to the accompanying drawings, given by way of advantageous embodiments. Show it:

Fig. 1:

a lighting device according to the invention in use;

Fig. 2:

a schematic representation of a lighting device according to the invention;

3:

a schematic representation of the operation of a diffuser;

4:

a schematic representation of a diffuser;

Fig. 5:

the lighting device off Fig. 2 in a view from the front;

Fig. 6:

the view according to Fig. 5 in another embodiment of the invention;

Fig. 7:

the view according to Fig. 4 in another embodiment of the invention;

Fig. 8:

the view according to Fig. 4 in still another embodiment of the invention;

Fig. 9:

a schematic representation of an alternative embodiment;

Fig. 10:

another embodiment of the invention; and

Fig. 11:

an embodiment of an inventive arrangement.

A lighting device 14 according to the invention is shown in FIG Fig. 1 arranged on a tripod 15. Via a hinge 16, the lighting device 14 can be pivoted up and down, a hinge 17, the lighting device 14 can be rotated to the right and left. In Fig. 1 For example, the illumination device 14 is set to provide concentrated illumination for an object 18 on a stage 19.

According to Fig. 2 the illumination device 14 comprises a light source 29 arranged in a housing 20. The light source 29 is composed of a plurality of light sources Fig. 5 shown LEDs 30 together. The LEDs 30 are arranged honeycomb-like side by side and aligned parallel to each other to the output of the housing 20. Each LED 30 includes a collimator optics so that the light is emitted in the form of a narrow cone. At the outlet of the housing 20, a diffuser 21 is arranged. Also possible are embodiments in which the light source 29 is a single powerful LED, for example with a power of more than 50 W.

The operation of the diffuser 21 is described below with reference to Fig. 3 explained. Contained in the diffuser 21 is a plurality of liquid crystals 22 which transmit light only in certain directions, respectively. Are the liquid crystals 22 as in Fig. 3A aligned with each other, they are all translucent in the same direction. When light that is in Fig. 3 indicated by arrows 24, impinges on the diffuser 22, the light can pass directly through the diffuser 22 in the appropriate direction. The diffuser 22 is then transparent. Are the liquid crystals 22 as in Fig. 3B disordered, the light is diffused in the diffuser 21 in all possible directions. Also in this state, the majority of the light on the other side of the diffuser 21 exits again, but in different directions. The effect of the diffuser 21 is similar to that of frosted glass.

According to Fig. 4 the diffuser in the lighting device 14 according to the invention has the shape of a plate-shaped element 25. The plate-shaped element 25 comprises two glass plates 26, which are arranged at a small distance parallel to each other. Between them, the glass plates 26 enclose a layer of liquid crystals 22. Between the glass plates 26 and the liquid crystal layer, a conductive layer 27 is formed respectively. Via a controllable voltage source 28, a voltage between the conductive layers 27 can be applied. When no voltage is applied between the conductive layers 27, the liquid crystals 22 are disordered and incident light is scattered in various directions. By applying a voltage between the conductive layers 27, the liquid crystals 22 are aligned with each other. Incident light can pass straight through and the plate-shaped element 25 becomes transparent. The voltage source 28 is infinitely variable, so that a continuous transition of the liquid crystals 22 from the disordered state to the aligned state is possible.

In Fig. 1 a voltage is applied to the diffuser 21 and the diffuser 21 is transparent. The light generated by the light source 29 passes straight through the diffuser 21 and impinges directly on the object 18 on the stage 19. This lighting condition is suitable, for example, to take close-up shots of the object 18. Turning off the voltage on the diffuser 21, the liquid crystals 22 go into the disordered state, and incident light is scattered in all directions. The stage 19 is uniformly illuminated with diffused light over a large area, so that good illumination is provided for overview photos.

Fig. 6 shows a front view of an alternative embodiment of a lighting device according to the invention 14. The light source 29 is divided into four separate light regions 31. In each light region 31, twelve LEDs 30 are arranged in matrix form. Two obliquely opposite light areas 31 are equipped with LEDs 30 which emit cold white light. The LEDs 30 of the other two light areas 31 emit warm white light.

The plate-shaped element 25 of the diffuser 21 has four partial surfaces 32 on which a voltage can be applied independently of one another. A cross section through the corresponding plate-shaped element is in Fig. 7 shown. The conductive layer 27 is interrupted according to the partial surfaces 32. For each partial area 32, a voltage source 28 is provided, so that an independent control of the partial areas 32 is possible. In Fig. 7 is at the lower part surface 32 to a voltage and not on the upper part surface 32.

Each of the partial surfaces 32 of the diffuser 21 is assigned to a light region 31 and positioned in front of the relevant light region 31. By applying a voltage to the sub-areas 32, the warm-white light and the cold-white light can be directed or scattered directly on the object. By suitable control of the partial surfaces 32 as a continuous change in the color temperature of the illumination is possible. In particular, this change is possible without at the same time the brightness changes significantly.

If the light areas 31 are equipped with LEDs 30 of different color, it is possible in a corresponding manner, to achieve continuous transitions in the color of the lighting. Instead of LEDs 30 with different colors, the same color LEDs can be used and the light can be influenced by appropriate filters.

In the embodiment of the Fig. 8 the plate-shaped element 25 covers only a part of the LEDs 30. The centrally arranged LEDs 30 always radiate directly onto the object. Only with the LEDs 30 at the edge can be set whether they should illuminate the object directly or whether the light should be scattered.

In the embodiment of the Fig. 9 there are two lens systems indicated schematically at 5, with which the illumination angle can be changed by displacing these lens systems or by shifting parts of the lens systems relative to one another. Through the plate 21 can be selected again between direct illumination by the LEDs of the lighting device 1 and a diffuse illumination.

In Fig. 10 the light source 29 is composed of a red LED 33, a green LED 34 and a blue LED 35, which are each equipped with a Kolllimatoroptik. In front of each LED, a single controllable diffuser 21 is arranged. Via mirrors 36 and the dichroic mirrors 37, the light is superimposed into a concentric light beam. If all diffusers 21 are in the same state, the superimposed light beam is white. If, for example, the light of the red LED 33 is scattered more strongly, the result is an image as shown in FIG Fig. 10 indicated at 38. It forms a corona of red light, while the intensity of the red light in the center is reduced.

Fig. 11 shows a TV studio with a table 38 and a chair 39, on which, for example, a newscaster can sit. The background for the images taken with a TV camera 40 forms a wall 41. At the foot of the wall, a lighting device 14 according to the invention is arranged, which illuminates the wall 41 at an acute angle. By adjusting the diffuser 21, the intensity and the area distribution of the illumination can be set so that the desired image is created for the TV camera.

Claims (15)

Lighting device, in particular in the form of a beacon (14) for TV recordings, stages, etc., with a light source (29) and with a in the beam path of the light source (29) arranged plate-shaped element (25), wherein the plate-shaped element (25) two transparent plates (26) having a layer of liquid crystals (22) disposed therebetween, the liquid crystals (22) being disordered in a first state and wherein the liquid crystals (22) are aligned with each other in a second state and switching between states an electric voltage is applied to the liquid crystal layer. Lighting device according to claim 1, characterized in that in the first state of the plate-shaped element (25) passing light is scattered. Lighting device according to claim 1 or 2, characterized in that in the second state of the plate-shaped element (25) incident light can pass directly. Lighting device according to one of claims 1 to 3, characterized in that the light source (29) has an LED (30). Lighting device according to one of claims 1 to 4, characterized in that the liquid crystals (22) are enclosed between electrically conductive layers (27). Lighting device according to claim 5, characterized in that a controllable voltage source (28) is provided to apply a voltage between the electrically conductive layers (27). Lighting device according to one of claims 1 to 6, characterized in that the plate-shaped element (25) only partially covers the light emitted by the light source (29). Lighting device according to one of claims 1 to 7, characterized in that the light source (29) has a plurality of separate light regions (31) and that the light regions (31) emit light with different properties. Lighting device according to one of claims 1 to 8, characterized in that it comprises one or more plate-shaped elements (25) with separate electrically controllable partial surfaces (32). Lighting device according to claim 8 or 9, characterized in that the partial surfaces (32) are associated with the light regions (31). Lighting device according to one of claims 8 to 10, characterized in that an optical element (36, 37) is provided in order to different from Partial surfaces (32) to superimpose exiting light. Lighting device according to one of claims 1 to 11, characterized in that lens elements (5) are provided in the beam path, with which the illumination area is variable. Lighting device according to one of claims 1 to 12, characterized in that it comprises cooling means for the electrically controllable plate-shaped elements (25). Lighting device according to one of claims 1 to 13, characterized in that a suspension (16, 17) is provided, with which the illumination device (14) can be moved relative to a rigid structure. An assembly of a wall (41) and a lighting device (14), wherein the lighting device (14) is designed according to one of claims 1 to 14 and arranged so that the light impinges on the wall (41) at an acute angle.

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