EP3045805A1

EP3045805A1 - Colored strobe light

Info

Publication number: EP3045805A1
Application number: EP14196517.8A
Authority: EP
Inventors: Nina Lillelund Kildeby
Original assignee: Martin Professional ApS
Current assignee: Harman Professional Denmark ApS
Priority date: 2014-12-05
Filing date: 2014-12-05
Publication date: 2016-07-20

Abstract

The invention relates to a lighting fixture (10) comprising a housing (20), at least one LED (31) provided in the housing. The housing comprises a light exit opening (21) for the light emitted by the at least one LED, and a scrolling assembly (40). The scrolling assembly comprises a first spool (41) and a second spool (42) and a sheet (50) extending between the two spools (41, 42). The scrolling assembly is configured to scroll the sheet (50) from one of the spools to the other of the spools. The sheet (50) comprises different sections (50a-c), each section containing a different phosphor composition. The scrolling assembly is attached to the housing in such a way that the light of the at least one LED passing through the light exit opening passes through the sheet.

Description

Technical Field

Various embodiments relate to a lighting fixture, especially a strobe light which is able to emit strobe light in different colors.

Background

A light emitting diode, LED, is an electro-luminescent diode that includes a semiconducting material doped with an impurity to form a p-n junction. Materials for the LEDs can be selected in such a way that the light emitted by the LED has a particular color such as red, green or blue. LEDs have many advantages over conventional light sources, as the power consumption is lower, the lifetime is longer and the size is smaller. In order to generate white light, two solutions are known. In one solution a red LED, a green LED and a blue LED are used and the light emissions are mixed generating a white light beam. The second solution includes the use of a blue LED coated with a phosphor material so that the blue light emitted by the LED is converted by the phosphor material into a light with a longer wavelength.
For the generation of an LED strobe light, the first approach can be used with the RGB LEDs in order to generate the white light. However, the price of such a strobe light is due to the number of LEDs quite high compared to the output of the strobe light. Furthermore, a strobe light comprising pure white LEDs is known giving the maximum output in the white colors. If other colors than white for the strobe light should be generated, the light is filtered. However, these color filters absorb light and, hence, lead to a lower output of the strobe light.
Accordingly, a need exists to provide a strobe light which can generate different colors which has an improved light output.

Summary

This need is met by the feature of the independent claim. The dependent claims describe further aspects of the invention. A lighting fixture is provided comprising a housing and at least one LED provided in the housing, wherein the housing comprises a light exit opening for the light emitted by the at least one LED. Furthermore, a scrolling assembly is provided comprising a first spool and a second spool and a sheet extending between the two spools. The scrolling assembly is configured to scroll the sheet from one of the spools to the other of the spools. The sheet comprises different sections and each section contains a different phosphor composition, wherein the scrolling assembly is attached to the housing in such a way that the light of the at least one LED passing through the light exit opening passes through the sheet.
The lighting fixture has the advantage that there is no need to filter the light in order to generate different colors. In the above described lighting fixture the different colors are generated by the different sections of the sheet, each section comprising a different phosphor composition resulting in a different light output. Recently, the use of flexible thin phosphor sheets has become available. By way of example, the different sections of the sheet can be composed of the different phosphor sheets as described in WO 2014/124325 .
Preferably, the lighting fixture operates as a strobe light. However, the lighting fixture can also operate as a normal lighting fixture generating different colors without a strobe effect.

Brief description of the Drawings

The lighting fixture together with the above and other advantages may best be understood from the following detailed description of the embodiments illustrated in the drawings.

FIG. 1 is a schematic exploded view of a lighting fixture configured to generate different output colors.
FIG. 2 is a perspective view of the lighting fixture of FIG. 1 in an assembled state.
FIG. 3 is a schematic sectional side view of the lighting fixture of FIGs. 1 and 2.
FIG. 4 is a schematic view of a scrolling assembly used in the lighting fixture of FIGs. 1 to 3.
FIG. 5 is a more detailed view of a sheet used in the scrolling assembly of FIG. 4.
FIG. 6 shows a schematic side view of another embodiment of the lighting fixture.
FIG. 7 shows a schematic side view of still another lighting fixture including the scrolling assembly.
FIG. 8 shows a schematic side view of an additional lighting fixture including the scrolling assembly.

Detailed description

The features mentioned above and the features yet to be explained below may not only be used in isolation or in combination as explicitly indicated, but also in other combinations. The features in the embodiments may be combined unless explicitly mentioned otherwise. In the following, embodiments will be described in detail with reference to the accompanying drawings. The drawings are regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose becomes apparent for a person skilled in the art. Any connection or coupling between functional blocks, devices, components or other physical units shown in the drawings and described hereinafter may be implemented by a direct or indirect connection or coupling.
FIG. 1 shows a perspective view of a lighting fixture 10 including a housing 20. A circuit board 30 with a plurality of LEDs 31 is provided, the LEDs 31 emitting preferably blue/violet light with a peak emission wavelength between 360 and 480 nm, preferably between 400 and 480 nm, and more preferably between 440 and 480 nm. The LEDs 31 can also be configured to emit ultra-violate light such as UVA light having wavelengths between 320-380nm, UVB light having wavelengths between 280-320nm and UVC light having wavelengths between 185-280nm; The circuit board 30 may be designed in such a way that each LED 31 can be controlled individually, especially can be turned on and off individually. In the embodiment shown a large number of LEDs are provided in rows and columns. The LEDs may also be electrically connected in series. The circuit board 30 with the LEDs 31 is connected to the inside of housing 20 in a fixed position with fixing elements not shown in the figure. The circuit board 30 and the LEDs 31 are arranged in such a way that the light emitted by the LEDs passes through a light exit opening 21 arranged opposite the upper surface of the circuit board 30. The internal surfaces 22 and 23 of the housing may be designed as reflective surfaces so that the light of the LEDs 31 is reflected by the surfaces 22, 23 and can pass through the light exit opening 21. In fact it is possible to provide one or more reflectors configured to reflect the light from the LEDs 31 towards to sheet 50 and the surfaces 22, 23 may be configured to reflect the light towards the sheet.
In FIG. 2 the housing 20 is shown in the assembled state with the light exit opening 21. In the embodiment shown, the housing 20 is made of two different parts 20a and 20b which are mirror-symmetric to a plane defined where the two parts 20a and 20b meet. On the front surface 24, where the light exit opening 21 is provided, the housing comprising web sections 25 and 26 which define with their corresponding shape the shape of the light exit opening. In the embodiment shown, light exit opening is substantially rectangular in shape. However, it should be understood that other shapes of the light exit opening are possible. Furthermore, the smaller the web sections are extending on the front surface, the less light is reflected from the LED 31 to the interior of the housing.
Inside the housing a scrolling assembly 40 is arranged. As can be deduced inter alia from FIG. 3, the scrolling assembly is arranged in the front part of the housing 20. The scrolling assembly comprises two spools 41 and 42, best seen in FIG. 4. A sheet 50 can be scrolled from one shaft 41 or 42 to the other of the shafts. The sheet in the form of a strap is fixed at its two outer ends to the two spools 41 and 42 and the sheet can be wound and rewound from one spool to the other, the sheet extending across the gap defined between the two spools. The width of the sheet in the direction perpendicular to the winding direction is such that the sheet fully covers the light exit opening. As a consequence, the light emitted by the plurality of LEDs 31 passes through the sheet 50 before exiting the lighting fixture 10. The scrolling assembly comprises a motor 60 which is configured to drive the spools in such a way that the sheet can be wound and rewound from one spool to the other. As shown in FIG. 4, a manual actuating device 70 may be provided with which the motor (60) can be manually controlled. Furthermore, an interface 61 may be provided at the motor with which control signals can be received from outside the lighting fixture in order to control the position of the sheet.
In the embodiment shown in FIG. 2 and 3, the scrolling assembly 40 is arranged inside the housing 20. However, the scrolling assembly 40 may also be arranged outside housing 20. It may be connected to the housing 20 in such a way that the sheet 50 covers the light exit opening from the outside. The connection of the scrolling assembly 40 to the outer surface of the housing 20 may be obtained by support structures not shown in the figures.
As can best be seen in FIG. 5, the sheet 50 comprises different sections 50a, 50b, and 50c, wherein each section of the sheet is sized such that the one section can fully cover the light exit opening 21. In FIG. 4 the right and the left border 51 and 52 of one section are shown by the dashed lines. As can be seen, the section 50b of the sheet 50 covers the complete light exit opening 21 shown in FIG. 4.
The different sections 50a, 50b, and 50c now differ from one another by the phosphor material used in each section. By way of example, one of the sections may comprise a yellow emitting phosphor or a blend of yellow and green emitting phosphor so that the light emitted by the sheet is white. Each section of the sheet 50 may be a phosphor sheet as commercialized by PhosphorTech Corporation and as described in WO 2014/124325 . Each section can be made of a substrate with a first layer of phosphor materials disposed on the surface of the substrate. A single layer of the phosphor particles may be prepared by applying a layer of adhesive to a substrate followed by applying phosphor particles, wherein the phosphor particles stick to the adhesive layer in a uniform and dense layer upon contact. The phosphor particles can be brushed or sprayed onto the adhesive surfaces until full coverage is achieved and no more phosphor particles would stick to the surface. The different sections now differ from one another in that one section 50b is coated with one kind of phosphor particles so that a first color is emitted by the sheet, whereas a neighboring sheet has a different phosphor composition so that another color is emitted by the phosphor sheet when the blue/violet LEDs 31 emit light.
The sheet is flexible and has a thickness between 50 and 500 µm so that it can be wound and unwound on the spools 41 and 42. The lighting fixture 10 can now generate different colors by scrolling the sheet in such a way that one particular section 50a, 50b, or 50c is located in front of the light exit opening. The scrolling assembly with motor 60 is designed in such a way that the motor knows which section 50a to 50c is located in front of the light exit opening. By way of example, the motor 60 may have a memory in which the position of the different sections 50a to 50c in the sheet is known. Furthermore, each section may have a marker 55 indicating to the motor which phosphor material is provided on the corresponding section so that the motor knows which light will be emitted by the lighting fixture. In another embodiment the motor may be configured to count the longitudinal position of the sheet between the two spools so that in dependence of the two end positions of the sheet relative to the spools, it is known where each section of the sheet is located. The motor may be able to determine how the two spools 41 and 42 have to be rotated in order to place a certain section of the sheet in front of the light exit opening.
As shown in FIG. 5, one section of the sheet, here section 50a, comprises a cutout 56, wherein no sheet is provided, section 50a being held in position by the two webs 57, 58, which connect the section where the cutout is provided with the neighboring sections. The cutout 56 is dimensioned such that, when the cutout is located in front of the light exit opening, no sheet is located between the LEDs and the light exit opening. When section 50a is located in front of the light exit opening, the light emitted by lighting fixture 10 has the color of the light as emitted by the LEDs. If the LEDs are blue LEDs, then the lighting fixture emits blue light.
In one embodiment one of the sections of the sheet comprises areas comprises a number of sub-sections where each sub-section comprises different phosphor compositions. As a consequence when such section is arranged in the light the different phosphor material of the different subsections will generate different colours at the same time. The relatively size of the sub-sections can be varies in order to change the ratio between the different colours generated by the different phosphor material. Additionally the different subsections can be formed in predefined patterns whereby the sheet also can be used to generate graphical patterns such as images or logos. For instance the light fixture may be driven in a viewing mode where the LEDs provide a lower light output to the phosphor sheet whereby an audience may be we able to observe the phosphor sheet directly. However it is to be understood that the light fixture also can create strobe light using such section.
FIG. 6 shows another example of a lighting fixture. In the example shown in FIG. 6, the light output generated by the lighting fixture is further improved. In the embodiment of FIG. 6, the lighting fixture with the LEDs 31 and the phosphor sheet additionally comprises first light collecting elements 61a and 61b. These light collecting elements are arranged in such a way that each first light collecting element collects the light emitted by one or several LEDs and directs the light in direction of the sheet 50. The light emitted by each of the LEDs is emitted in substantially 180° to the space above the circuit board 30. The first light collecting elements 61a and 61b help to guide the light emitted by the LEDs in direction of the sheet so that the amount of light passing through the sheet 50 is increased. The first light collecting elements 61a and 61b may be designed as TIR (Total Internal Reflection lenses) lenses, regular optical lenses, light mixing rods, or regular reflectors. In the embodiment shown, one first light collecting element is provided for each LED. However, it should be understood that also one first light collecting element may be provided for more than one LED.
Furthermore, second light collecting elements 62a and 62b can be provided to collect the light emitted by the phosphor sheet 50. As indicated by the arrows in the sheet 50, the light emitted by the phosphor sheet is directed into different directions. The light collecting elements 62a and 62b help to further direct the light beam or light beams emitted by the lighting fixture. With the use of the second light collecting elements, more focussed light beams such as light beams 65 and 66 are obtained. The second light collecting elements 62a, 62b may be designed as light mixing rods in which the light entering the light mixing rod is reflected at the internal surface and thus generates a more focussed and homogenous light beam. Alternatively the second light collecting elements can be provided as TIR (Total Internal Reflection lenses) lenses, regular optical lenses, or regular reflectors. It should be understood that only one of the light collecting elements may be provided, either the first light collecting elements 61a and 61b or the second light collecting elements 62a and 62b.
FIG. 7 shows an embodiment in which only the first light collecting elements 61 are provided such as the three first light collecting elements 61a-61c. Furthermore, the scrolling assembly with the phosphor sheet 50 is arranged at a distance such that each of the first light collecting elements, e.g. the TIR lenses generate light beams 70a-70c which are more focused than if the light were directly emitted from the LED 31 to this sheet 50 without providing the light elements 61a-61c. In the embodiment of FIG. 7, three of the LEDs 31 are shown together with three first light collecting elements. However, it should be understood that any number of LEDs may be used and that one first light collecting element may be provided for each LED. In another embodiment, one first light collecting element such as elements 61a-61c is provided for a group of LEDs. The light emitted by the phosphor sheet 50 is then emitted in substantially 180° to the direction opposite to the space where the LEDs are located as symbolized in FIG. 7 by the arrows 71.
FIG. 8 shows a further embodiment in which the components present in FIG. 7 are also present. However, an additional lens 80 is provided to collect the light emitted by the phosphor sheet 50. This lens may be a Fresnel lens which collects the light emitted by the phosphor sheet so that a light beam 81 is obtained which is more focused than the light beam emitted in the embodiment of FIG. 7, where no light collecting element is used after the sheet 50.
The optical systems shown in FIG. 6 to 8 do not indicate the housing 20. The housing 20 may be arranged relative to the lenses shown in FIG. 6 to 8 in such a way that all the optical elements shown in FIG. 6 to 8 are provided inside the housing or at least at the light exit opening, however, the light exit opening may also be provided directly before or after the phosphor sheet 50 so that the second light collecting elements such as the elements 62 or the Fresnel lens 80 are located directly on the housing at the light exit opening. Furthermore, the second light collecting elements or the Fresnel lens 80 may also be located outside the housing, e.g. when the phosphor sheet 50 is also attached to the outside of the housing.
In one example the sheet may be kept temporarily in front of the light exit opening until it is decided to change the color of the lighting fixture. In another example the sheet with the different sections may be continuously scrolled so that a light effect with continuously changing colors is obtained.
In one embodiment the lighting fixture is operating as a strobe light. In another embodiment, however, the lighting fixture may be used as a continuously light emitting lighting fixture.
Summarizing, a lighting fixture is obtained which can generate different colors with a high light output.

Claims

A lighting fixture (10) comprising:
- a housing (20),

- at least one LED (31) provided in the housing, wherein the housing comprises a light exit opening (21) for the light emitted by the at least one LED,

- a scrolling assembly (40) comprising a first spool (41) and a second spool (42) and a sheet (50) extending between the two spools (41, 42), wherein the scrolling assembly is configured to scroll the sheet (50) from one of the spools to the other of the spools, wherein the sheet (50) comprises different sections (50a-c), each section containing a different phosphor composition, wherein the scrolling assembly is attached to the housing in such a way that the light of the at least one LED passing through the light exit opening passes through the sheet.
The lighting fixture (10) according to claim 1, wherein each section (50a - 50c) of the sheet has at least the size of the light exit opening (21) of the housing.
The lighting fixture according to claim 1 or 2, wherein one section (50a) of the sheet (50) comprises a cutout (56) having a size of at least the light exit opening (21) so that when said one section (50a) with the cutout (56) is located in front of the light exit opening (21), the light from the at least one LED (31) passes through the light exit opening (21) without passing the sheet (50).
The lighting fixture (10) according to any of the preceding claims wherein one section of the sheet comprises a plurality of sub-sections, wherein each sub-section contains a different phosphor composition.
The lighting fixture (10) according to any of the preceding claims wherein the at least one LED (31) has a peak emission wavelength between 360 and 480 nm.
The lighting fixture (10) according to any of the preceding claims, wherein the at least one LED (31) is an array of LEDs arranged in at least two columns and at least two lines.
The lighting fixture (10) according to any of the preceding claims wherein the lighting fixture is configured to operate as a strobe light.
The lighting fixture (10) according to any of the preceding claims wherein the sheet (50) is a flexible sheet with a thickness between 50 and 500 µm.
The lighting fixture according to any of the preceding claims, wherein the scrolling assembly (40) comprises a motor (60) configured to control the scrolling of the sheet (50) between the two spools (41, 42), wherein the motor is configured to control the scrolling in such a way that the light from the at least one LED passing through the light exit opening passes through a single section of the sheet.
The lighting fixture according to any of the preceding claims, wherein the scrolling assembly (40) is provided inside the housing and the sheet (50) is located between the at least one LED (31) and the light exit opening (21).
The lighting fixture according to any of the claims 1 to 9, wherein the scrolling assembly (40) is connected to an outside of the housing (20) wherein the sheet (50) covers the light exit opening (21) from the outside of the housing.
The lighting fixture according to any of the preceding claims, further comprising at least one light collecting element located between the at least one LED (31) and the sheet (50) configured to collect the light emitted by the at least one LED.
The lighting fixture according to any of the preceding claims, further comprising at least one light collecting element (62a, 62b) located after the sheet in a direction of the light emitted by the at least one LED in direction of the sheet in order to collect the light emitted by the sheet (50).
The lighting fixture according to claim 13 wherein the at least one light collecting element (62a, 62b) contains at least one light rod.
The lighting fixture according to claim 13 wherein the at least one light collecting element is a Fresnel lens (80) collecting the light emitted by the sheet (50).
The lighting fixture according to any of claims 12 to 15 wherein the at least one light collecting element (61a-c) located between the at least one LED and the sheet (50) contains at least one Total Internal Reflection lens.