WO2013064971A2

WO2013064971A2 - A multi-view lighting device, an assembly and a luminaire

Info

Publication number: WO2013064971A2
Application number: PCT/IB2012/056007
Authority: WO
Inventors: Ties Van Bommel; Rifat Ata Mustafa Hikmet
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2011-11-02
Filing date: 2012-10-30
Publication date: 2013-05-10
Also published as: WO2013064971A3

Abstract

A multi-view lighting device100, an assembly and a luminaire are provided. The multi-view lighting device 100 presents a first image 218 being related to a first predefined image 224 in a first direction and a second image 229 being related to a second predefined image 222 in a second direction being different from the first direction. The multi- view lighting device 100 comprises a light source 104, a light conversion element 110, and a matrix of optical structures 102. The light source 104 emits light in first color distribution. The light conversion element 110 receives light from the light source and emits light according to a composite image. The light conversion element 110 comprises one or more luminescent materials being configured to absorb a part of light of the first color distribution and to convert a part of the absorbed light towards one or more other colors. The one or more luminescent materials are arranged in a plane to form the composite image. The composite image being based on the first predefined image 224 and the second predefined image 222. The matrix of optical structures 102 receives light emitted by the light conversion element 10, refracts light being related to the first predefined image 224 into a first light emission direction and refracts light being related to the predefined second image 222 into a second 1 light emission direction.

Description

A multi-view lighting device, an assembly and a luminaire

FIELD OF THE INVENTION

The invention relates to multi-view lighting devices having a surface for presenting a first image in a first direction and a second image in a second direction.

Examples of multi-view devices are devices which present a stereoscopic image to a person who looks from a specific position towards the multi-view devices.

BACKGROUND OF THE INVENTION

Multi-view devices are known in the art. For example, in the form of greeting cards presenting a three dimensional image or displays that image a three dimensional movie. To obtain an auto stereoscopic effect two images are provided at two viewing directions in order to image two slightly different images in the eyes of a person such that the person experiences a three dimensional picture. In other applications more than two images are provided at a plurality of viewing angles. If a person or, for example, a camera moves relative to the multi-view device, different images will be seen. The images may be subsequent images of a film scene and the person will see the short film scene. The series of images may also be an animation, or a specific type of animation like for example a comic, a morph or a zoom.

Published patent specification US5695346 discloses several embodiments of multi-view devices which present an auto stereoscopic image to a user or present an animation. One of the devices described in the cited patent specification is a shelf header slide-in display assembly. The shelf header slide-in assembly consists of a translucent basis on which two dimensional translucent images and a special interlaced translucent image are printed. An array of lenticular lenses is provided in front of the interlaced image. The shelf header slide-in assembly is back lit with a light source.

The interlaced image consists of alternating stripes of two or more images. If back lit, the surface of the shelf header slide-in assembly emits light into the direction of a visitor of the shop. If not back lit, a part of the ambient light is reflected. At the area of the interlaced image the emitted and reflected light is refracted by the array of lenticular lenses such that light originating from the stripes of one image is refracted into one specific viewing direction, and light originating from the stripes of another image is refracted into another specific viewing direction.

The interlaced image and the array of lenticular lenses is designed such that a visitor of the shop who stands in front of the shelf and who looks towards the shelf header experiences a three dimensional image at the position of the interlaced image. Alternatively, the shelf header slide-in assembly may be designed such that, if the visitor passes along the shelf and looks towards the shelf header, the visitor sees an animation, representing a series of successive images.

The interlaced image is printed, which means that, if light from is light source is transmitted through the interlaced image, a part of the light is absorbed, and, if impinging ambient light is reflected by the interlaced image, a part of the impinging ambient light is absorbed.

A problem of the disclosed shelf header slide-in assembly is that the assembly is not light efficient.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a more efficient multi-view lighting device. A first aspect of the invention provides a multi-view lighting device. A second aspect of the invention provides an assembly. A third aspect of the invention provides a luminaire. Advantageous embodiments are defined in the dependent claims.

A multi-view lighting device presents a first image being related to a first predefined image in a first direction and presents a second image being related to a second predefined image in a second direction being different from the first direction. The multi- view lighting device comprises a light source, a light conversion element, and a matrix of optical structures. The light source emits light in first color distribution. The light conversion element receives light from the light source and emits light according to a composite image. The light conversion element comprises one or more luminescent materials being configured to absorb a part of light of the first color distribution and to convert a part of the absorbed light towards one or more other colors. The one or more luminescent materials are arranged in a plane to form the composite image. The composite image is based on the first predefined image and the second predefined image. The matrix of optical structures receives light emitted by the light conversion element, refracts light being related to the first predefined image into a first light emission direction and refracts light being related to the predefined second image into a second light emission direction.

The multi-view lighting device emits light and, consequently, lightens the environment in which the multi-view lighting device is provided when it is in operation. A viewer, who looks towards the multi-view lighting device at a viewing angle along the first direction or the second direction, sees the first image or the second image. Thus, for this viewer, the multi-view lighting device is not a surface with an uniform light emission, but is a light emitting surface with an image. The viewer may also see the first image and the second image if one of his eyes is in the path in which the first image is emitted and the other one of his eyes in in the path in which the second image is emitted - depending on the specific first image and second image, the user may see a stereoscopic image.

The composite image is formed by locally providing in the plane a specific amount of one or more luminescent material and/or by locally providing in the plane a specific combination of one or more luminescent materials. This results in a local light emission of light of a specific color by the light conversion element. The specific color is related to the color of the first predefined image or the second predefined image.. The multi- view lighting device uses luminescent material to convert light which originates from the light source towards light of another color to obtain a light emission which has locally, in accordance with the composite image, a specific color. The conversion of light by

luminescent materials is relatively efficient and effective, and, thus, compared to the known technologies wherein light is locally absorbed, a more efficient solution is obtained to emit light according to the composite image.

The composite image comprises areas which are related to the first predefined image and comprises areas which are related to the second predefined image. The matrix of optical structures is arranged in such a relative position with respect to the light conversion element (emitting colors of light according to the composite image) that light, which is emitted by areas related to the first predefined image is emitted into the first direction and that light, which is emitted by areas related to the second predefined image, is emitted into the second direction. Thus, an eye of a person, which is inside the light emitted into the first direction and which looks towards the multi-view device, sees the first image - another eye of the person, or an eye of another person, which is inside the light emitted into the second direction and which looks towards the multi-view device, sees the second image. Thus, the multi-view lighting device has two different views in two different directions. It is to be noted that the invention is not limited to presenting only two images in only two different directions. More than two different images may be presented in more than two different directions by use of a specific composite image which comprises the information of more than two predefined images and by use of a matrix of optical structures which is adjusted for the specific composite image.

It is to be noted that the term matrix comprises the term array. An array of optical structures is obtained by arranging optical structures in a matrix with a single row or a single column.

Further, the luminescent materials may be any material which is capable of absorbing light of a first spectral range and converting (a part of) the absorbed light into light of a second spectral range. Hence, inorganic phosphors and/or organic phosphors may be used, as well as, quantum dots and quantum rods.

The first direction is a direction towards a predefined first point which has a relative position with respect to the multi-view lighting device. If the first point is at a relatively large distance from the multi-view lighting device, the light rays which are emitted towards the first point are refracted by the optical elements into about the same light emission angles. If the first point is predefined at a relatively short distance from the multi-view lighting device, the light rays which are emitted towards the first point are refracted by the optical element into slightly different light emission angles. The same applies for the second direction.

Optionally, the composite image comprises sub-images, the sub-images are either based on a portion of the first predefined image or based on a portion of the second predefined image.

Optionally, the sub-images have a rectangular shape or have a triangular shape. Rectangles and triangles can be arranged in a raster or a matrix without spaces between the sub-images. This allows an optimal use of the space that is available in the light conversion element for the composite image. Further, if the sub-images are arranged in a raster or matrix of respective triangles or rectangles, advantageous constructions of the matrix of optical structures can be used to refract light of sub-images which are related to different images into different directions.

For example, the sub-images may have an elongated shape and sub-images related to the first predefined image and the second predefined image may alternate in an array. This allows the use of an array of optical structures wherein one elongated optical structure is related to two neighboring elongated shaped sub-images, wherein the elongated optical structure refracts light originating from one of the neighboring sub-images into the first direction and light originating from another one of the neighboring sub-images into the second direction.

If the sub-images have a triangular shape, four sub-images related to four different predefined images may be arranged into a square, and optical structures with the shape of a prism or pyramid may refract light originating from the four sub-images into four different directions.

Optionally, the sub-images comprise one or more pixels. Each pixel represents an image pixel of the respective first predefined image or of the respective second predefined image. A first subset of the pixels comprise a pixel specific amount of a specific one of the one or more luminescent materials to obtain a pixel specific light emission having a color distribution in accordance with the image pixel of the respective first predefined image or of the respective second predefined image.

A pixel is a subarea of the sub-image, and is, for example, a square area of the light conversion element that is provided with the specific amount of one or more specific luminescent material(s). The specific amount of the luminescent material results in the absorption of a specific amount of light of the first color distribution and the generation of a specific amount of another color. Also some light of the first color may be transmitted through the luminescent material(s), and thus, the pixel has a light emission which comprises a combination of light of the first color distribution and light of the another color generated by the luminescent material. Each pixel of the sub-image is related to the image pixel of either the first predefined image or the second predefined image. The color of the light emission of the pixel is based on the image color of the pixel of the respective predefined image. The first subset may comprise all pixels, and in that case all pixels contain a pixel specific amount of a pixel specific combination of luminescent material. It is possible that at specific areas of the sub-images no light conversion is required and luminescent material is absent at those pixels such that the received light of the first color distribution is let through the pixels.

Optionally, pixels of the first subset of pixels comprise a pixel specific mix of specific amounts of two or more luminescent materials of the one or more luminescent materials to obtain the pixel specific color distribution in accordance with the image pixel. The use of luminescent materials in pixels is not limited to one luminescent material only. More than one luminescent material may be mixed and provided in the light conversion element at the area of the specific pixel. Optionally, a second subset of the pixels is subdivided into sub-pixels.

Specific sub-pixels of the corresponding pixel comprise the one or more sub-pixel a specific luminescent material. A combined light emission of the sub-pixels of their corresponding pixel has a pixel specific color distribution in accordance with an image pixel to which the corresponding pixel relates. Thus, instead that one or more luminescent materials are provided along the whole area of the pixel, the pixel may be subdivided into several sub- pixels which comprise no or one or more specific luminescent material. Thus, each sub-pixel emits a sub-pixel light emission and the combination of the sub-pixel light emissions is the combined light emission of the pixel and the combined light emission is based on a corresponding pixel in the respective first image or second image. It is to be noted that, a characteristic size of the sub-pixels should be such that, if a viewer is at a predetermined distance from the multi-view lighting device and looks towards the multi-view lighting device, the eyes of the viewer can not distinguish between the individual sub-pixels. It is to be noted that the second subset may overlap with the first subset, or may be disjoint with the first subset.

Optionally, the he light conversion element further comprises light intensity reduction material being partly light reflective and partly light transmissive. The light intensity reduction material is arranged in the light conversion element according to the composite image to locally decrease a light intensity emitted by the light conversion element.

If the first predefined image and the second predefined image comprise relatively large intensity differences at different areas of the respective images, the use of luminescent material in the light conversion element may not be sufficient to obtain a realistic reproduction of the first predefined image and the second predefined image. This problem is solved by the light intensity reduction material which may be locally be used to reduce the emitted light intensity. The light intensity reduction material does not absorb light - a portion is transmitted and the remaining light is reflected back. In other words, the light intensity reduction material is partly light reflective and partially light transmissive. Back reflected light may be recycled by the light source, for example, when the light source comprises a light reflective cavity. Thus, the light tuning material does not negatively influence the efficiency of the multi-view lighting device.

Optionally, a third subset of the pixels comprise a pixel specific amount of light intensity reduction material to reduce the light intensity of the light emission of the pixel in accordance with the image pixel of the respective first predefined image or the respective second predefined image. It is to be noted that the third subset may overlap with the first subset of pixels and/or the second subset of pixels, and may also be disjoint with the first and/or the second subset of pixels. It is to be noted that the use of the light intensity reduction material in a pixel may also be sub-divided in applying a specific amount of light intensity reduction material per sub-pixel.

Optionally, the optical structures comprise at least one of lenses, lenticular lenses, prisms, or lenticular prism. (Lenticular) Lenses and (lenticular) prisms are effective and efficient optical structures to be used in the matrix of optical structures.

Optionally, a combination of the light conversion element and the matrix of optical structures is configured to generate an auto stereoscopic image to a viewer who looks towards the multi-view device. The auto stereoscopic image is a three dimensional image that is seen by the viewer if he is located at as specific position in front of the multi-view lighting device and if he looks with both eyes towards the multi-view lighting device. The auto stereoscopic image is presented to a viewer when the left eye of the viewer receives an image that corresponds to an image that would be seen by that left eye if the presented three dimensional object was present at the location of the multi-view lighting device, and when the right eye of the viewer receives an image that corresponds to an image that would be seen by the right eye if the presented three dimensional object was present at the location. This means that the first direction is a direction towards a predefined position of one of the eyes of the viewer, and that the second direction is a direction towards another predefined position of the other one of the eyes of the viewer. This also means that the first predefined image and the second predefined image, are recordings of the three dimensional object from a certain distance from slightly different neighboring positions.

Optionally, a combination of the light conversion element and the matrix of optical structures is configured to generate a series of images if a position of the viewer changes relatively to a position of the multi-view lighting device. This optional embodiment allows the presentation of a short animation. In this specific option, the multi-view lighting device is arranged to present a plurality of images in a plurality of different directions.

Optionally, the light source comprises a housing and one or more light emitters. The housing encloses a cavity. Surfaces of the housing that face the cavity are light reflective and the housing comprises a light exit window for emitting light towards the light conversion element. The one or more light emitters are provided within the cavity. Relatively light efficient light source may be manufactured according to this option and the light emission at the light exit window is relatively uniform. Because the surfaces of the housing that face the cavity reflect light, light is not absorbed and is given another chance to leave the cavity after the reflection by the surface. It also results in the arrival of light at a plurality of light emission angles at the light exit window. Thus, the surface of the light emitters itself do not have to have the same size as the size of the light conversion element, because the cavity spreads the light along the whole light exit window.

The light emitters may be Light Emitting Diodes (LEDs), Organic LEDs, fluorescent light tubes, incandescent lamps. The light emitters may emit light of the first color distribution, which is, for example, a color distribution which comprises a significant amount of blue light, and in other embodiment, the emitted light comprises light in the UV spectral range (in which case the luminescent material(s) convert the UV light towards visible light). Further, the light source itself may also comprise luminescent material for generating the first color distribution.

It is to be noted that the multi-view device according to the invention are not limited to light sources which comprise a cavity. For example, an Organic LED of a size equal to the size of the light conversion element may be applied to the light conversion element.

Optionally, the one or more luminescent materials comprises at least one of an inorganic luminescent material, a quantum dot and an organic luminescent material.

Optionally, the organic luminescent material comprises a perylene derivative.

In accordance to a second aspect of the invention, an assembly is provided which comprises the multi-view lighting device according to the first aspect of the invention. The assembly is one of: i) a push button for generating a three dimensional image or a series of images on the push button, ii) an indicator for generating an indication by means of a three dimensional image or a series of images, iii) an advertisement sign for generating an three dimensional image or a series of images as part of the advertisement sign, and iv) a company logo presentation board for generating a three dimensional company logo presentation or for generating a series of images comprises the company logo.

The assemblies according to the second aspect are attractive to viewers because they present a three dimensional image or a series of images (if the viewer moves relatively to the assembly). Further, the assemblies are well visible because it emits light.

According to a third aspect of the invention, a luminaire is provided which comprises the multi-view lighting device according to the first aspect of the invention.

The assemblies according to the second aspect of the invention and the luminaire according to the third aspect of the invention provide the same benefits as the multi-view devices according to the first aspect of the invention and have similar embodiments with similar effects as the corresponding embodiments of the multi-view devices.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

It will be appreciated by those skilled in the art that two or more of the above- mentioned options, implementations, and/or aspects of the invention may be combined in any way deemed useful.

Modifications and variations of the device, the assemblies and/or the luminaire, which correspond to the described modifications and variations of the device, can be carried out by a person skilled in the art on the basis of the present description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 schematically shows a three dimensional view of an embodiment of a multi-view lighting device according to the first aspect of the invention,

Fig. 2 schematically shows a cross-section of the embodiment of the multi- view lighting device of Fig. 1,

Fig. 3a schematically shows a cross-section of an alternative embodiment of the multi-view lighting device,

Fig. 3b schematically shows a top view of a light conversion element comprising sub-images and pixels,

Fig. 4a schematically shows a top view of a light conversion element comprising sub-images that are related to a first to a fourth image,

Fig. 4b schematically shows a matrix of optical elements comprising lenses,

Fig. 4c schematically shows a matrix of optical element comprises prisms, Fig. 5(a) to (f) schematically show different arrangements of luminescent material and/or light intensity reduction material in the light conversion element,

Fig. 6a schematically presents a dvd player comprising different assemblies according to the second aspect of the invention,

Fig. 6b schematically presents a luminaire according to the third aspect of the invention, and

Fig. 6c schematically shows an advertisement sign. It should be noted that items denoted by the same reference numerals in different Figures have the same structural features and the same functions, or are the same signals. Where the function and/or structure of such an item have been explained, there is no necessity for repeated explanation thereof in the detailed description.

The Figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 schematically shows a three dimensional view of a first embodiment of a multi-view lighting device 100 according to the first aspect of the invention. The multi- view lighting device 100 is for presenting a first image in a first direction and generating a second image in a second direction which is different from the first direction. The multi-view lighting device 100 comprises a light source 104, a light conversion element 110 and a matrix 102 of optical elements. The first image and the second image are related to a first predefined image and a second predefined image, respective, which means that they are a sort of reproduction of the first predefined image and the second predefined image and that, due to technical limitations of the multi-view lighting device 100, they may be slightly differently.

The light source 104 emits light of a first color distribution towards the light conversion element 110. The light conversion element 110 comprises one or more luminescent materials which are configured to absorb a part of the light of the first color distribution and to convert a part of the absorbed light towards other colors. The one or more luminescent materials are arranged in a plane to form a composite image. The composite image is based on a first predefined image and a second predefined image. The light conversion element 110 emits light according to the composite image. At a specific side of the multi-view lighting device 100 of Fig. 1 it is seen that the light conversion element 110 has different areas 106, 108. The areas 106, 108 are so-termed sub-images and each sub- image 106, 108 relates either to the first predefined image or to the second predefined image. In Fig. 1, a second sub-image 106 and all other sub-images, which are drawn a little more dark, relate to the second predefined image. Further, a first sub-image 108 and all other sub- images which are drawn (in a cross-sectional view) with a white rectangle, relate to the first predefined image. It is to be noted that the sub-image relate to the predefined images, because they may be slightly different because of limitations of the composite image, or limitations of the luminescent material. A pair of a single second sub-image 106 and a single first sub-image 108 is arranged at a specific relative position to a single optical element of the matrix 102 of optical elements. The optical element refracts light which originates from the first sub-image 108 into a first direction - this light is related to the first predefined image. And refracts light which originates from the second sub-image 106 into the second direction - this light is related to the second predefined image.

In Fig. 1 an imaginary line A- A' is indicated. Fig. 2 schematically shows a cross-sectional view along the imaginary line A- A' of the embodiment of the multi-view lighting device 100 of Fig. 1.

The light source 104 comprises a housing 216 which encloses a cavity 214. Surfaces of the housing 216 that face the cavity are light reflective. The housing 216 further comprises a light exit window at which the light conversion element 110 is provided. Light emitters 212 are provided within the cavity 214 and emit, in operation, light of the first color distribution. The light emitters 212 are, for example, Light Emitting Diodes (LEDs), Organic LEDs, traditional fluorescent light tubes, or traditional incandescent lamps. The light of the light emitters 212 partly falls onto the surfaces of the housing 216 which are reflective.

Consequently, the cavity 214 acts as a light mixing box which provides a relatively homogenous light output at the light exit window and light arrives at a plurality of light emission angles at the light exit window. Further, if any light is reflected back by light conversion element 110 or by the matrix 102 of optical elements, this light is recycled by the cavity because it is reflected once or more times before it arrives again at the light exit window of the housing 216. It is to be noted that the light emitters 212 may comprise luminescent material as well to obtain the light emission of the first color distribution.

The surfaces of the housing 216, which are light reflective, reflect at least 80% of light which impinges on the surfaces. In another embodiment, the surfaces reflect more than 90% and in yet another embodiment, the surfaces reflect more than 95% of the light which impinges on them. The surfaces of the housing 216 which face the cavity may be provided with, for example, a coating which comprises A1₂0₃ or Ti0₂ particles. The surfaces may also be provided with other layers that have a light reflective property.

In the cross-sectional view of Fig. 2, cross-sections of the sub-images 106, 108 of the light conversion element are drawn. Light 206, which is emitted by the second sub- images 106 (which are related to the second predefined image 222), is refracted by the optical elements 210 into the second direction, which is in the example of Fig. 2, a direction towards a second viewer 204. Light 208 which is emitted by the first sub-images 108 (which are related to the first predefined image 224), is refracted by the optical elements 210 into the first direction. The first direction is, in the example of Fig. 1, a direction towards a first viewer 202. Thus, the first viewer 202 sees the first image 218, and the second viewer 204 sees the second image 220.

In Fig. 2 the first image 218 and the second image 220 are drawn above the symbol of an eye of the respective first viewer 202 and second viewer 204. The first image 218 and the second image 220, are, based on the received respective light 206, 208, constructed in the mind of the respective first viewer 202 and the second viewer 204. The multi-view lighting device 100 does not have a specific place where the complete first image 218 or the complete second image 220 is present. The multi-view lighting device 100 comprises the respective sub-image 106, 108 which related to the drawn elongated stripes of the respective first predefined image 224 and second predefined image 222. It is to be noted that the first predefined image 218 and the second predefined image 220 are images which are used to create the composite image in the light conversion element 110 and which are planned to be seen by the respective first viewer 202 and the second viewer 204.

Although, in this discussion of Fig. 2, the first viewer 202 and the second viewer 204 are assumed to be different persons, the drawn symbols 202, 204 may also represent both eyes of a single person. Especially if the first image 218 and the second image 220 are images that are configured to present an auto-stereoscopic image to the single person, the single person sees a three dimensional image. It is also possible that a single person moves from a first position (where symbol 202 is drawn) towards a second position (where symbol 204 is drawn) and that he sees subsequently different images at the light emitting surface of the multi-view lighting device 100.

Further, in Fig. 1 and 2 the second sub-images 106 alternate with the first sub- images 108. In other embodiment more than two predefined images may be combined in the composite image, for example, by alternating elongated stripes which are related to the first, the second and a third predefined image and provide three elongated strips below a single optical element 210. In such a configuration, three different images are presented in three different directions.

In the embodiment of Figs. 1 and 2, the optical elements are elongated

(lenticular) lenses. Other optical elements which are capable of refracting light in different direction may be used as well. For example, as discussed in the Fig. 3 and Fig. 4 the optical elements may also be elongated prisms, prisms or lenses with a square footprint.

Fig. 3 a schematically shows a cross-section of an alternative embodiment of multi-view lighting device 300. The light source of the multi-view lighting device 300 comprises a light emitter 302, a light guide 304, light outcoupling structures 306 and a mirror 308. A first side of the light guide 304 is facing the light conversion element. A second side of the light guide 304, which is a side opposite the first side, comprises the light outcoupling structures 306. The mirror 308 is provided to the second side of the light guide 304. The light outcoupling structures 306 are arranged to outcouple light guided light 310 towards the light conversion element 110. A light emitter 302 is arranged in a so-termed side-emitting configuration, which means that it emits light into the light guide via a light input window which is arranged substantially perpendicular to the light exit window. The mirror 308 is used to assist the light guiding of light within the light guide 304 and to reflect light towards the light conversion element 110 if the light conversion element 110 or the matrix 314 of optical elements 312 reflects back light towards the mirror 308. Thus, the mirror also assists in the recycling of light and the multi-view lighting device 300 is relatively efficient.

The arrangement and function of the light conversion element 110 has been discussed in the context of Figs. 1 and 2.

The matrix 314 of optical element comprises a plurality of elongated prism shaped optical structures 312. One of the sloping top surfaces of the elongated prism shaped optical structures 312 has a specific relative position to the first sub-images 108, such that light 208 emitted by the first sub-images 108 is refracted by the elongated prism shaped optical structures 312 into the first direction. Another one of the sloping top surfaces of the elongated prism shaped optical structures 312 has a specific relative position to the second sub-images 106, such that light 206 emitted by second sub-images 106 is refracted by the elongated prism shaped optical structures 312 into the second direction.

Fig. 3b schematically shows a top view of a light conversion element 110. At the left end of Fig. 3b are presented the first predefined image 224 and the second predefined image 222. The light conversion element 110 comprises, as discussed previously, sub-images 106, 108. In Fig. 3b one sub-image is a column of a grey level or a column which is presented without grey level. The first sub-images 108 are related to portions of the first predefined image 224. The second sub-images are related to portions of the second predefined images 222. Each sub-image 106, 108 comprises pixels 352, 354 (indicated by the rows). Depending on the specific sub-image in which the pixels are located, the pixels 352, 354 relate to image pixels either of the first predefined image or of the second predefined image. Each pixel 352, 354 of the light converting element emits a specific color distribution and/or light intensity that is related to a color or an intensity of the corresponding pixel in either the first predefined image or the second predefined image. It is to be noted that the pixels of Fig. 3b have (in the top-view) a square shape. Other shapes are possible as well, such as, for example, triangular or hexagonal pixels.

Fig. 4a schematically shows a top view of a light conversion element 400 which comprises sub-images 402, 404, 406, 408. The sub-images 402 ... 408 have, in a top view, a triangular shape and they are combined in a specific raster, such that a combination of four sub-images 404 ... 408 form a square. The first sub-images 402 related to a first predefined image. The second sub-images 404 relate to a second predefined image. The third sub-images 406 relate to a third predefined image. The fourth sub-images 408 relate to a fourth predefined image. Sub-images which are related to the same predefined image are schematically filled with the same pattern. If the sub-images are arranged in such a configuration, the first to fourth image may be visible in four different directions when the matrices 430, 460 with optical element 432, 462 of Fig. 4b and 4c are used.

Fig. 4b schematically shows a matrix 430 of optical elements comprising lenses 432 which have a square footprint and have cross-sections 434, 436 along the indicated lines a and b.

Fig. 4c schematically shows a matrix 460 of optical element comprises prisms 434 which have cross-sections 464, 466 along the indicated lines a and b.

Fig. 5(a) to (f) schematically show different arrangements of luminescent material and/or light intensity reduction material in a plane of the light conversion element.

As discussed before, each pixel of the sub-images emits a specific color distribution and/or a specific light intensity which relate to the color or the intensity of a corresponding image pixel in the first or second predefined image. The luminescent material(s) and/or a light intensity reduction material are applied, per pixel, in a such a configuration that if light of the first color distribution is received from the light source, the specific color distribution and/or specific light intensity is emitted by the pixels.

In Fig. 5(a) a first configuration is shown. In the figure, the light source 506 is drawn schematically as a layer on top of which a light conversion element 504 is arranged. At the light emission side of the multi-view lighting device is arranged a matrix of optical elements 502. Embodiments of the light source 506 and the matrix of optical elements 502 are discussed previously.

The rectangle which is drawn with a grey level is a cross-section of a first pixel 508 of a specific second sub-image. The first pixel 508 comprises a specific amount of a single specific luminescent material to absorb a portion of light of the first color spectrum (received from the light source 506) and to convert a part of the absorbed light into light of another color distribution. The specific amount of luminescent material may be enough to prevent the transmission of light of the first color spectrum through the first pixel 508 and, thus, emits the first pixel 508 only light of the another color. The second pixel 510 does comprise an alternative luminescent material which converts absorbed light into an alternative color. Further, the amount of the alternative luminescent material in the second pixel 510 is not enough to prevent the complete transmission of light of the first color and thus comprises a light emission of the second pixel 510 light of the first color distribution and light of the alternative color. It is to be noted that the first pixel 508 and/or the second pixel 510 may also comprises a mix of luminescent materials to obtain a desired color conversion.

The configuration of Fig. 5(b) is similar to the configuration of Fig. 5(a), only the first pixel 508 of Fig. 5(a) is replaced by a first layer 524 which comprises a specific amount of a specific luminescent material, and a second layer 522 which comprises another amount of another luminescent material. The first layer 524 and the second layer 522 are configured to have a combined light emission that is substantially equal to a desired light emission for the specific pixel which is formed by the first layer 524 and the second layer 522.

The configuration of Fig 5(c) is similar to the configuration of Fig. 5(a), only the first pixel 508 of Fig. 5(a) is replaced by the first layer 524 which comprises the specific amount of the specific luminescent material, and a second layer 532 which comprises a light intensity reduction material. The second layer 532 allows the transmission of a specific amount of light through the second layer 532 and back reflects the light which is not transmitted through the second layer 532. Thus, the emitted light intensity of the pixel is reduced and the light which is reflected back may be recycled by the light source. The light intensity reduction material of the second layer 532 reduces the amount of emitted light such that a desired light intensity is emitted by the pixel formed by the first layer 524 and the second layer 532.

The configuration of Fig. 5(d) comprises sub-pixels 540 ... 550. The sub- pixels 546, 540, 548 form together a single pixel of a second sub-image of which the light emission must have a certain color. The sub-pixels 546, 540, 548 each comprise a specific amount of a specific luminescent material such that each sub-pixel 546, 540, 548 emits a sub- pixel light emission. The sub-pixels are configured to emit a combined light emission of the sub-pixel light emissions (of sub-pixels 546, 540, 548) which is substantially equal to the desired light emission of the pixel formed by the respective sub-pixels. The same applies to sub-pixels 542, 550, 544 which form together a single pixel of a first sub-image.

In the configuration of Fig. 5(e) certain sub-pixels 562, 564, 566 comprises a layer 568, 569 with light intensity reduction material which reduces the amount of light emitted by the sub-pixels 562, 564, 566 and the light which is not allowed to be transmitted through the sub-pixels 562, 564, 566 is back reflected towards the light source.

In the configuration of Fig. 5(f) certain sub-pixels 572, 574 do not comprise luminescent material and are fully light transmitting. These sub-pixels may comprise a scattering material, such as Ti0₂ or A1₂0₃ particles, which results in a relatively diffuse light emission by the sub-pixels 572, 574.

Examples of the luminescent materials being used in the light conversion element include organic and inorganic phosphors. Examples of organic phosphors are luminescent materials based on perylene derivatives. Commercially available products are sold under the name Lumogen by BASF, such as Lumogen Red F305, Lumogen Orange F240, Lumogen Yellow F 170 or Yellow F083. These materials may be mixed as well and may be combined with scattering particles, such as A1₂0₃ or Ti0₂. Examples of inorganic phosphors suitable as luminescent materials include, but are not limited to, cerium doped yttrium aluminum garnet (Y3A15012:Ce3+, also referred to as YAG:Ce or Ce doped YAG) or lutetium aluminum garnet (LuAG, Lu3A15012), a-SiA10N:Eu2+ (yellow), and

M2Si5N8:Eu2+ (red) wherein M is at least one element selected from calcium Ca, Sr and Ba. Another example of an inorganic phosphor that may be used in embodiments of the invention, typically in combination with a blue light emitting light source, is YAG:Ce.

Furthermore, a part of the aluminum may be substituted with gadolinium (Gd) or gallium (Ga), wherein more Gd results in a red shift of the yellow emission. Other suitable materials may include (Sri x yBaxCay)2 zSi5 aAlaN8 aOa:Euz2+ wherein 0 < a <5, 0 < x <l, 0 < y < l and 0 < z < 1, and (x+y) < 1, such as Sr2Si5N8:Eu2+ which emits light in the red range.

In embodiments of the invention the luminescent materials may comprise quantum dots. Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can, therefore, be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphode (InP), and copper indium sulfide (CuInS2) and/or silver indium sulfide (AgInS2) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore, the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention, provided that it has the appropriate wavelength conversion characteristics.

However, it may be preferred for reasons of environmental safety and concern to use cadmium- free quantum dots or at least quantum dots having a very low cadmium content.

The multi-view lighting device comprises a light source. The term light source may in principle relate to any light source known in the art.

In an embodiment, the light source is a light source that during operation emits at least light at wavelength selected from the range of 200-490 nm, especially a light source that during operation emits at least light at wavelength selected from the range of 400-490 nm. This light may partially be used by the luminescent material.

In a specific embodiment, the light source comprises a solid state LED light source (such as a LED or laser diode). The term "light source" may also relate to a plurality of light sources, such as (solid state) LED light sources.

In an embodiment, the light source may also provide light source light having a correlated color temperature (CCT) between about 5.000 and 20.000 K, e.g. direct phosphor converted LEDs (blue light emitting diode with thin layer of phosphor for e.g. obtaining of 20.000K. These types of LEDs are used in LED light based backlights of LCD panels but can also be used in suggested multi-view lighting device. An advantage of the relative high color temperature may be that there may be a relative high blue component in the light source light. This blue component may partially be absorbed by the luminescent materials and converted into luminescent material light. Optionally, a separate blue light source (such as a solid state LED) may be included in the light source. The terms "blue light" or "blue emission" especially relates to light having a wavelength in the range of about 440-490 nm (including some violet and cyan hues).

Fig. 6a schematically shows a DVD player 600 which comprises a plurality of assemblies 602, 604, 606 which comprise a multi-view lighting device according to the first aspect invention.

An assembly 602 presents a company logy by means of a first multi-view lighting device to the user of the DVD player 600. The company logo may be visible as a three dimensional image or an animation, and, is, for example, only visible when the DVD player 600 is in operation. The use of assembly 602 is advantageous because the company logo is better visible and will early attract the attention of people. A second assembly 606 is an error-indicator for providing to the user an indication that an error occurred in the operation of the DVD player 600. By switching the multi- viewing lighting device, for example, alternatingly on and off a blinking error indication may be created which comprises a three-dimensional image.

A third assembly 504 is a 'play' push button to indicate in a three dimensional image that the 'play' push button may be pushed to start the playing of a DVD.

Fig. 6b schematically shows a luminaire 630 which comprising a multi-view lighting device 632. The presented luminaire 630 may, for example, be provided to a ceiling. The light emitting surface of the luminaire has, because of the use of the multi- view lighting device 632, an attractive look of a three-dimensional image, or in the form of a plurality of different images being presented in different direction. The images imaged by the multi- view lighting device 632 may suggest that the luminaire 630 has a spherical light emitting surface. In another embodiment, a first image indicating an emergency route is presented in a first direction, while in the other direction another image is presented.

Fig. 6c schematically shows an advertisement board 660 which comprises a multi- view lighting device 662. The multi- view device 662 presents to the viewer a three dimensional advertisement or an animated advertisement to the viewer who, for example, passes in a car. The advertisement board 660 attracts much faster the attention of a viewer than an advertisement sign which presents a two dimensional image only.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. A multi-view lighting device (100, 300, 632) for presenting a first image (218) being related to a first predefined image (224) in a first direction and a second image (220) being related to a second predefined image (222) in a second direction different from the first direction, the multi-view lighting device (100, 300, 632) comprises:

- a light source (104, 506) for emitting light in first color distribution,

a light conversion element (110, 400, 504) for receiving light from the light source (104, 506) and for emitting light according to a composite image, the light conversion element (110, 400, 504) comprising one or more luminescent materials being configured to absorb a part of light of the first color distribution and to convert a part of the absorbed light towards one or more other colors, the one or more luminescent materials being arranged in a plane to form the composite image, the composite image being based on the first predefined image (224) and the second predefined image (222),

a matrix (110, 314, 430, 460) of optical structures for receiving light emitted by the light conversion element (110, 400, 504) and for refracting light being related to the first predefined image (224) into a first light emission direction and for refracting light being related to the second predefined image (222) into a second light emission direction.

2. A multi-view lighting device (100, 300, 632) according to claim 1, wherein the composite image comprises sub-images (106, 108, 402 ... 408), the sub-images (106, 108, 402 ... 408) are either based on a portion of the first predefined image (224) or based on a portion of the second predefined image (222).

3. A multi-view lighting device (100, 300, 632) according to claim 2, wherein the sub-images (106, 108, 402 ... 408) have a rectangular shape or have a triangular shape.

4. A multi-view lighting device (100, 300, 632) according to claim 2, wherein the sub-images (106, 108, 402 ... 408) comprises one or more pixels (352, 354, 508, 510), each pixel (352, 354, 508, 510) represents an image pixel of the respective first predefined image (224) or of the respective second predefined image (222), and pixels of a first subset of the pixels comprise a pixel specific amount of a specific one of the one or more luminescent materials to obtain a pixel specific light emission having a color distribution in accordance with the image pixel of the respective first predefined image (224) or of the respective second predefined image (222).

5. A multi-view lighting device (100, 300, 632) according to claim 4, wherein pixels of the first subset of the pixels comprises a pixel specific mix of specific amounts of two or more luminescent materials of the one or more luminescent materials to obtain the pixel specific color distribution in accordance with the image pixel.

6. A multi-view lighting device (100, 300, 632) according to claim 4, wherein a second subset of the pixels is subdivided into sub-pixels (540 ... 560), specific sub-pixels (540 ... 560) of their corresponding pixel (352, 354, 508, 510) comprise the one or more specific luminescent materials, and a combined light emission of the sub-pixels (540 ... 560) of their corresponding pixel (352, 354, 508, 510) has a pixel specific color distribution in accordance with an image pixel to which the corresponding pixel relates.

7. A multi-view lighting device (100, 300, 632) according to claim 1, wherein the light conversion element (110, 400, 504) further comprises light intensity reduction material being partly light reflective and partly light transmissive, the light intensity reduction material being arranged in the light conversion element (110, 400, 504) according to the composite image to locally decrease a light intensity emitted by the light conversion element (110, 400, 504).

8. A multi-view lighting device (100, 300, 632) according to claim 4 and 7, wherein a third subset of the pixels comprise a pixel specific amount of light intensity reduction material to reduce the light intensity of the light emission of the pixel in accordance with the image pixel of the respective first predefined image (224) or the respective second predefined image (222).

9. A multi-view lighting device (100, 300, 632) according to claim 1, wherein the optical structures comprises at least one of lenses (432), lenticular lenses (210), prisms (462), or lenticular prisms (312).

10. A multi-view lighting device (100, 300, 632) according to claim 1, wherein a combination of the light conversion element (110, 400) and the matrix (110, 314, 430, 460) of optical structures is configured to generate an auto stereoscopic image to a viewer (202, 204) who is looking towards the multi-view lighting device (100, 300, 632).

11. A multi-view lighting device (100, 300, 632) according to claim 1, wherein the light source (104, 506) comprises

a housing (216) enclosing a cavity (214), surfaces of the housing (216) facing the cavity (214) are light reflective, and the housing (216) comprises a light exit window for emitting light towards the light conversion element (110, 400, 504), and

one or more light emitters (212) provided within the cavity.

12. A multi-view lighting device (100, 300, 632) according to claim 1, wherein the one or more luminescent materials comprises at least one of an inorganic luminescent material, a quantum dot and an organic luminescent material.

13. A multi-view lighting device (100, 300, 632) according to claim 12, wherein the organic luminescent material comprises a perylene derivative.

14. An assembly (604, 602, 606, 662) comprising the multi-view lighting device

(100, 300, 632) according to claim 1, the assembly being one of:

a push button (604) for generating a three dimensional image or a series of images on the push button,

an indicator (606) for generating an indication by means of a three dimensional image or a series of images,

an advertisement sign (662) for generating an three dimensional image or a series of images as part of the advertisement sign, and

a company logo presentation board for generating a three dimensional company logo presentation or for generating a series of images comprises the company logo.

15. A luminaire (630) comprising the multi-view lighting device (100, 300, 632) according to claim 1.