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1. WO2014147505 - DISPOSITIF D'ÉCLAIRAGE AVEC DISPOSITIF DE MISE EN FORME DE FAISCEAU RÉGLABLE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

Illumination device with adjustable beam shaper

FIELD OF THE INVENTION

The present invention relates to an illumination device with a partially light reflecting beam shaper for controlling the light distribution, and to a method of

manufacturing such a device.

BACKGROUND OF THE INVENTION

Illumination devices emitting light having a predefined illuminance or intensity pattern are of interest for various lighting purposes, including applications such as exterior and interior building lighting, landscape lighting, painting lighting, wall-washing, and ornamental projections. Traditional illumination devices may comprise adjustable apertures or projection optics for projection of a mask or a template arranged in front of a lighting source to control the shape, intensity pattern, and/or illuminance of emitted light.

In for example US 2006/0245184, a lighting device is described, which has an aperture mechanism assembly operating in the same fashion as an iris type control. The aperture mechanism assembly is used to provide an illumination pattern that has a well-defined far field beam image, and to provide an ability to tailor the light output pattern of the device. The aperture blades are formed from a neutral density filter material, a translucent diffuser material, or a colored filter material, and may be variably adjusted between a spot and a flood beam pattern based on the desired lighting effect. The color of the lighting device may be changed by opening of closing one or several iris devices that are provided in front of the light source.

Although such a device may provide light beams of various intensity and shape, there is still a need for improved illumination devices capable of emitting light having an adjustable light distribution.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide an illumination device capable of emitting light, having a predefined and/or adjustable light distribution and/or intensity pattern, optionally with an improved efficiency.

This and other objects of the present invention are achieved by means of an illumination device, a luminaire, and a method, respectively, having the features defined in the independent claims. Preferable embodiments of the invention are characterized in the dependent claims.

Hence, according to a first aspect of the present invention, an illumination device is provided, comprising a light mixing chamber having a light reflecting inner surface, a light emitting element arranged to emit light into the light mixing chamber, and a beam shaper having an at least partially light reflecting portion and at least one at least partially light transmitting region. The beam shaper is arranged such that, during operation, a first portion of the light generated by the light emitting element is reflected back into the light mixing chamber by the at least partially light reflecting portion, and a second portion of light generated by the light emitting element is directly transmitted through the beam shaper via the at least one at least partially light transmitting region. The beam shaper provides an illuminance distribution at the exit plane of the beam shaper, which may be projected by an optical imaging element onto a target region, e.g. as intensity into the far field or as a prescribed illuminance pattern on to a target region at a predetermined distance from the illumination device.

According to a second aspect of the present invention, a method is provided, comprising the steps of providing a light mixing chamber having a light reflecting inner surface, and arranging a light emitting element such that light can be emitted into the light mixing chamber. The method further comprises arranging a beam shaper, having an at least partially light reflecting portion and at least one at least partially light transmitting region, to reflect a first portion of light generated by the light emitting element back into the light mixing chamber, and to directly transmit a second portion of light generated by the light emitting element through the beam shaper.

According to a third aspect, a luminaire is provided, comprising an illumination device according to the first aspect of the present invention.

The light reflecting portion and the light transmitting region of the beam shaper may define a masking pattern or structure that enables the intensity of the light passing through the beam shaper to be controlled. The masking structure also allows the light beam exiting the beam shaper to be provided with a certain shape and/or an intensity pattern. Thereby the illumination may be adapted to the specific object to be illuminated, or illumination target.

The present invention is based on a realization that the efficiency of the lighting device, i.e. the ratio between the output light energy and the input energy of the device, may be improved by using a beam shaper wherein the non-transmitting portions are light reflecting. Thereby the portion of light that does not pass through the beam shaper is reflected back into the mixing chamber. Recycling light by reflecting it back into the mixing chamber, instead of e.g. letting it be absorbed by "dark" areas of the beam shaper, may improve the efficiency of the illumination device.

The light mixing chamber may be provided with a light reflecting inner surface, which advantageously improves the mixing and the homogeneity of the light before it is out-coupled via the beam shaper. The inner surface may for example be specular light reflecting, or diffusive white. The mixing chamber also allows for several and different light emitting elements to be used, having e.g. different color, spectra, and/or color temperature, wherein the light emitted from each light emitting element may be mixed before reaching the beam shaper such that each individual light emitting element may be less visible to the eye of an observer. A highly reflective inner surface may advantageously improve the efficiency of the mixing chamber, due to less losses caused by for example light absorption. This also applies to the at least partially light reflecting portion of the beam shaper.

The term "light-emitting element" is used to define any device or element that is capable of emitting radiation in any region or combination of regions of the

electromagnetic spectrum, for example the visible region, the infrared region, and/or the ultraviolet region, when activated e.g. by applying a potential difference across it or passing a current through it. Therefore a light-emitting element can have monochromatic, quasi-monochromatic, polychromatic or broadband spectral emission characteristics. Each light-emitting element has at least one light source. Examples of light sources include

semiconductor, organic, or polymer/polymeric light-emitting diodes (LEDs), e.g. blue LEDs, direct LEDs, phosphor converted LEDs, optically pumped nano-crystal LEDs or any other similar devices as would be readily understood by a person skilled in the art. RGB LEDs may advantageously be used to enable dynamic color light output from the illumination device. Furthermore, the term light-emitting element can be used to define a combination of the specific light source that emits the radiation in combination with a housing or package within which the specific light source or light sources are placed. For example, the term light emitting element may comprise a bare LED die arranged in a housing, or an array of LED elements, which also may be referred to as an LED package.

The light emitting element may be arranged for example outside of the mixing chamber, wherein the emitted light may be guided or transmitted into the mixing chamber by for example a light guide, or introduced via a light entering portion or aperture in a sidewall or bottom portion of the chamber. The light emitting element may also be arranged within the mixing chamber, e.g. arranged on a bottom or sidewall portion, such that the light is generated directly within the mixing chamber. The light emitting element may form a separate unit, or an integral part of a wall of the mixing chamber.

The beam shaper comprises one or several portion(s) that may be for example diffusive (white) or specular reflective, and one or several region(s) that may be at least partially light transmitting. It will be appreciated that the at least partially light transmitting region may comprise an opening, such as e.g. a light exit window or aperture. Such light exit aperture may e.g. be defined by sidewalls of the mixing chamber.

The reflective portion of the beam shaper may be arranged to cast a shadow, which is visible to the eye, in the projected image, thereby enabling a pattern to be projected on the illumination target. For example, it may be desirable to shape or limit the illumination to follow the shape of a wall of a building such that light pollution outside of the target plane may be reduced. The design of the beam shaper may for example be computer generated to form a desired projection image and to correct for distortions of the projection optics.

It will be appreciated to those skilled in the art that the beam shaper may be comprised of for example a cut -through substrate of a light reflecting material, such as a metal sheet of foil, such that the reflective portions of the beam shaper are provided by the substrate and the transmitting portion are comprised of the cut-out portions. The beam shaper may also be formed of one or several portions of the sidewalls of the mixing chamber, such that the sidewall portion(s) may form the at least partially light reflecting portion(s) of the beam shaper, and the light exit aperture, defined by the sidewall portion(s), forms the at least partially light transmitting region of the beam shaper.

According to an embodiment of the present invention, the beam shaper comprises an optical mask. The optical mask may have a plurality of at least partially light reflecting portions separated, in the plane of the mask, by one or several at least partially light transmitting region(s). The optical mask may for example comprise an at least partially light transmitting substrate onto which a patterned, at least partially light reflecting layer is disposed. The at least partially light reflecting layer may for example comprise a white or specular light reflecting material. Other examples of reflective mask materials include metals or metal alloys, which can be sputtered, evaporated, screen printed, plated, laminated, or

deposited onto the substrate by any other suitable techniques known readily understood by a person skilled in the art. Examples of patterning methods include wet etching, dry etching, laser etching, lift off, printing, and other methods available in the art. The substrate may for example comprise silicate glass, poly(methyl methacrylate) (PMMA), quartz, ceramics, or other light transmitting material.

The pattern of the optical mask may also comprise a repetitive pattern of the at least partially light reflecting portions.

In order to produce a light distribution, wherein the emitted light has a varying intensity, it may be advantageous if the light reflecting portions of the pattern are small enough not to be visible to the eye in the projected image (i.e. on the surface which is illuminated by the illumination device).

The beam shaper, comprising e.g. an optical mask, may advantageously be arranged such that the at least partially light reflecting portions face the light emitting element and the light mixing chamber, to allow for the light to be reflected back into the mixing chamber.

The beam shaper may be directly coupled to the mixing chamber, preferably in the direct proximity of the light exit portion, for example by means of a spacer, interlayer, or fastening means, such that light exiting the mixing chamber may impinge on the optical mask.

According to an embodiment, the beam shaper is interchangeably arranged at the light exit portion of the light mixing chamber. This advantageously allows for the user of the illumination device to change between several different types of beam shaper, such as e.g. optical masks, depending on the desired light distribution, illuminance, intensity pattern, etc. It also allows for late stage configuration during manufacturing of the illumination device, and adjustment upon installation or by the end user, by simply interchanging the mask.

According to an embodiment, the beam shaper may be movably arranged at a light exit portion of the light mixing chamber so as to enable the shape and/or area of exit portion of the mixing chamber to be adjusted during operation.

The optical mask may also comprise Model Lighting Ordinance (MLO) type repetitive pyramidal structures of a dielectric material. Such pyramidal structures may e.g. let light be transmitted through the optical mask within an interval of approximately ±60° relative to a normal of the surface of the optical mask, while light not transmitted may be reflected back into the mixing chamber. Using such structures may advantageously provide a simplified, more compact, and/or more efficient projection optics.

According to an embodiment, the beam shaper comprises a portion of an inner wall of the light mixing chamber wherein the portion of the inner wall is moveable, or possible to angle, in relation to the rest of the inner wall so as to change the shape and/or area of the light exit portion of the light mixing chamber. By moving the portion of the inner wall, the light exit portion may be formed to conform to various shapes such as e.g. circles, ovals, triangles, and rectangular shapes. Moving, or deforming, one or several reflective walls or reflective portions of walls of the light mixing chamber advantageously enables the light distribution and/or intensity pattern of the emitted light to be adjusted with an improved efficiency.

According to an embodiment, the mixing chamber comprises a first sidewall and a second sidewall which are movable in relation to each other such that the area of the light exit portion of the mixing chamber is decreased in response to the first and second sidewalls being moved towards each other, and increased in response to the first and second sidewall being moved away from each other.

According to an embodiment, the beam shaper comprises an at least partially light reflecting diaphragm member, e.g. an iris diaphragm, arranged to receive light exiting the light mixing chamber. The at least partially light reflecting portions of the beam shaper form a plurality of at least partially overlapping movable segments, which define a substantially circular light transmitting opening, or aperture. The diaphragm member is arranged at the light exit portion of the mixing chamber such that the at least partially light reflecting portions of the diaphragm member face the light mixing chamber. Thus, light impinging on the movable segments is reflected back into the mixing chamber. By moving the segments relative to each other, the size of the aperture may be varied accordingly. This enables the beam angle of the emitted light, i.e. the width of the projected beam, to be varied. For example, a relatively small aperture may provide a relatively narrow beam, while a relatively large aperture may be used for generating a relatively wide beam.

According to an embodiment, the illumination device further comprises an optical imaging element. By optical imaging element should be understood an arrangement of one or several refractive lenses and/or reflective mirrors adapted to collect most of, or at least a portion of the light transmitted through the beam shaper. The optical imaging element may be arranged to focus light transmitted through the beam shaper into the target illumination plane or into the far field. Thereby the projected image for example may be adapted to the distance between the illumination device and the illumination target. The optical imaging element may be used to transfer the illuminance pattern at the exit surface of the mixing chamber to the target illuminance plane or into the far field. A sharp image may for example be used for ornamental projection purposes requiring a distinct illumination pattern or projected image, whereas a blurred image may be desirable for other purposes, such as for example wall-washing and exterior building lighting, which may require a smoother lighting pattern.

The optical imaging element may comprise one or several lenses which may be controllably movable in relation to the light emitting element, preferably towards and/or away from the light emitting element, which enables the focus of the exiting light beam to be adjusted. The optical imaging element may also comprise other types of imaging collimator, such as for example a RXI collimator which may collimate the transmitted light by refraction (R), reflection (X), and internal reflection (I).

According to an embodiment, the optical imaging element comprises at least two lenses arranged in spaced relation to each other.

At least one of the lenses may be controllably movable in relation to another one of the at least two lenses, preferably towards and/or away from said another lens, which allows for a more precise control of the focus of the exiting light beam.

According to an embodiment, examples of lenses include spherical, aspherical, biconvex, plano-convex, biconcave, plano-concave lenses, or Fresnel lenses. Each one of the lenses may be independently selected.

It will be appreciated that other embodiments than these described above are also possible, for example comprising a several optical masks, mixing chambers, and optical focusing elements.

It will also be appreciated that any of the features in the embodiments described above for the illumination device according to the first aspect of the present invention may be combined with the method and luminaire according to the second and third aspects of the present invention, respectively.

Further objectives of, features of, and advantages with the present invention will become apparent when studying the following detailed disclosure, the drawings, and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, in which:

Fig. 1 schematically depicts a cross sectional side view of an illumination device according to an embodiment of the present invention, comprising a light mixing chamber and a beam shaper;

Fig. 2 schematically depicts a cross sectional side view of an illumination device according to another embodiment of the present invention, comprising a light mixing chamber, a beam shaper and a two lens optical element;

Fig. 3 schematically depicts cross sectional side view of a beam shaper comprising an optical mask;

Fig. 4 schematically depicts a top or frontal view of an optical mask having a plurality of at least partially reflective portions separated by an at least partially light transmitting portion;

Figs. 5a and 5b each schematically depicts a perspective view of a light mixing chamber having two moveable sidewalls;

Figs. 6a and 6b each schematically depicts a top view of a diaphragm element according to an embodiment of the present invention; and

Fig. 7 shows a general outline of a method of manufacturing an illumination device according to an embodiment of the present invention.

All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested. As illustrated in the figures, the sizes of layers and regions may be exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

With reference to Fig. 1, there is shown a schematic cross sectional side view of an illumination device according to an embodiment of the present invention.

The illumination device 100 comprises a mixing chamber 110 having diffusive, highly reflective inner walls 112 and a light exit portion 114. According to the embodiment depicted in Fig. 1, a plurality of light emitting elements 120 is arranged in an array on a support portion of the mixing chamber 110. The support portion may be considered an inner wall, and may also be reflective. The support portion opposes the light exit portion 114 such that light emitted by the plurality of light emitting elements 120 is emitted into the mixing chamber 110. The illumination device 100 may also comprise a single light emitting element 120, such as for example a high brightness LED, or a set of light emitting elements of different colors.

The emitted light, which according to the embodiment shown in Fig. 1 may originate from a plurality of light emitting elements 120, may be mixed within the mixing chamber 110 by internal reflection, forming a single light beam.

A beam shaper, such as e.g. an optical mask 130, is coupled to the light exit portion 114 of the mixing chamber 110 such that the mixed light exiting the mixing chamber 110 may impinge on the optical mask 130.

The optical mask 130 may comprise a transparent substrate 136 of for example glass or plastic, onto which a pattern 132 of a highly light reflective material is printed. The pattern 132 is facing the mixing chamber 110 and thus the light emitting elements 120, which thereby enables emitted light to be reflected by the light reflecting portions of the pattern 132. Light impinging on the light transmitting portions 134 of the mask 130, i.e. the "open" portions of the pattern 132 which are not provided with the light reflecting material, may pass through the optical mask 130 and thus form an exiting light beam comprising a representation of the pattern that can be projected as an image on the illumination target. The "black" areas of the projected image are thus achieved via reflection of light that may be recycled in the mixing chamber 110.

Fig. 2 illustrates another lighting device 100 according to an embodiment of the present invention. The mixing chamber 110 is provided with light emitting elements 120 emitting light which is mixed in the mixing chamber 110 and eventually exits the mixing chamber 110 through the light exit portion 114. The emitted light 105a then impinges on an optical mask 130 which covers the light exiting portion 114 such that a portion of the light is reflected back into the mixing chamber by the reflective portions of the pattern, and portion of the light is transmitted through the optical mask 130 via the transmitting portions. The optical mask 130 is interchangeably arranged over the light exit portion 114.

An optical focusing device is arranged after the optical mask 130, wherein the term "after" refers to the path of the light 105a, 105b transmitted through the optical mask 130, such that the transmitted light 105a, 105b can be focused or defocused. According to the embodiment depicted in Fig. 2, the optical focusing device comprises a plano-convex lens 142 arranged to cover the light exit side of the optical mask 130, and a Fresnel lens 144 arranged in a spaced relation (in the direction of the path of the light) to the plano-convex lens 142. The Fresnel lens 144 is controllably movable towards and away from the plano-convex lens 142 in order to vary the focus of the emitted light beam and thus the sharpness of the projected image. The optical focusing device may for example focus on a plane common with the pattern of the optical mask 130 to enable a sharp projection of the pattern on the illumination target.

In Fig. 3, an optical mask 130 is schematically depicted, comprising an at least partially light transmitting substrate 136. Portions 132 of an at least partially light reflecting material is applied (e.g. printed) onto a first side of the substrate 136 such that a reflective pattern 132 is defined. The portions 132 of the at least partially light reflecting material are separated by portions 134 of the at least partially light transmitting substrate 136 such that a repetitive, reflective pattern 132 is provided.

Referring to Fig. 4, there is shown a frontal view (in relation to Fig. 1) or top view (in relation to Fig. 3) of the optical mask 130 according to an embodiment of the present invention. The optical mask 130 comprises a pattern 132 defined by light reflecting areas which represent the outer periphery of the pattern, the circular structures, or dots 138, and truncated pyramidal structures 139. Light impinging on those areas is reflected back into the mixing chamber 110 wherein it may be recycled and mixed with the light emitted by the light emitting elements 120. The light reflecting areas thus represent "dark" areas in the resulting image that may be projected on the illumination target. The outer periphery of the light transmitting region 137, having the shape of a truncated pyramid, may for example represent the outer periphery of a wall of a building, which may reduce light pollutions outside the illuminated wall. Other, smaller structures representing circles 138, ovals (not shown), and truncated pyramids 139, may be provided to exclude e.g. windows of the target wall to be illuminated, and to reduce the intensity at certain regions of the wall. The larger area covered by the reflective portions 132, the more the illuminance will be reduced. It will however be realized that the dot pattern 138 may comprise smaller dots than indicated in Fig. 4, such that the illumination device not necessarily reproduces the dot pattern on the target area, but rather provides an illumination device having a reduced average brightness.

In Fig. 5a and 5b, a light mixing chamber 110 according to an embodiment of the present invention is schematically depicted. The light mixing chamber comprises four sidewalls 115, 116, 117, 118 including a first adjustable sidewall 117 and an opposite second adjustable sidewall 118. Each of the adjustable sidewalls 117, 118 is at least partially reflective, having at least partially reflective inner surfaces. Both sidewalls 117, 118 are moveable in relation to each other, while the sidewalls 115, 116 may be fixed in relation to each other. It will however be appreciated that the mixing chamber may comprise fewer sidewalls or more sidewalls, and that all or some of the sidewalls may be movable, or at least comprise portions which are movable in relation to each other. According to the present embodiment, the adjustable sidewalls 117, 118 comprise respective adjustable portions 117a, 118a which form the at least partially light reflecting portions of the beam shaper. The adjustable portions 117a, 118a may e.g. be articulated, folded, or bent towards and/or away from each other and/or any non-adjustable portion of the respective sidewall 117, 118, and in relation to the light exit aperture 114 so as to vary the position, shape and/or area of the at least one at least partially light transmitting region defined by the sidewalls of the mixing chamber. According to this embodiment, the at least one at least partially light transmitting region may form the light exit portion 114 of the mixing chamber. As shown in Fig. 5a, the first and second portions 117a, 118a of the sidewalls may be moved towards each other so as to form a relatively small light exit aperture 114. By moving the first and second portions 117a, 118a of the sidewalls of the light mixing chamber away from each other, such as shown in Fig. 5b, a light exit portion 114 may be provided, having a relatively large area.

As illustrated by Fig. 6a and 6b, a beam shaper according to embodiments of the invention may comprise a diaphragm member 150, such as an iris diaphragm. The at least partially light reflecting portions form a plurality of at least partially overlapping movable segments 152 arranged to define a substantially circular central light transmitting opening, or aperture 154. The segments 152 are arranged at the light exit portion 114 (indicated by dashed lines) of the mixing chamber 110 such that light impinging on the segments 152 is reflected back into the mixing chamber 110. By moving the segments 152 relative to each other, and adjusting the overlapping of each of the segments 152, the size of the central aperture 154 may be varied accordingly. Fig. 6a shows an iris diaphragm 150 wherein the overlapping segments 152 are arranged to define a relatively small aperture 154, whereas Fig. 6b shows an iris diaphragm 150 having a relatively large aperture 154.

Fig. 7 shows a general outline of a method of manufacturing an illumination device in accordance with what is described with reference to Figs. 1 and 2.

The method comprises providing 610 a light mixing chamber having a light reflecting inner surface, and arranging 620 a light emitting element such that light is emitted into the light mixing chamber. The method also comprises the step of arranging 630 a beam shaper, having an at least partially light reflecting portion and at least one at least partially light transmitting region, to reflect a first portion of light generated by the light emitting element back into the light mixing chamber, and to directly transmit a second portion of light generated by the light emitting element through the beam shaper.

The method may also comprise arranging 640 an optical imaging element to project the light transmitted through the optical mask to the target area.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, although the invention described with reference to Figs. 1 and 2 comprises one mixing chamber, it will be appreciated that the present invention may comprise a plurality of mixing chambers having any suitable shape and design known in the art, including for example cylindrical, spherical and conical shapes having for example a circular, elliptical, or polygonal cross section. It will also be appreciated that the illumination device, according the present invention, may comprise a plurality of optical masks having various shapes and constitution.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.