Illumination system for optically widened perception

An illumination system (1, 100, 200, 300) for providing an optically widened perception comprises a reflector unit (6, 206, 306) comprising a reflective surface (8A) and a luminous layer (10, 210, 310) for homogenously emitting diffuse light at a first color, the luminous layer (10, 210, 310) extending in front of the reflective surface (8A) and comprising a visible front area section (10A, 210A, 310A) of the reflector unit (6, 206, 306), which extends up to a first boundary (12A, 310A) and through which the diffuse light is emitted. The illumination system (1, 100, 200, 300) comprises further a light projector (2, 202, 302) configured to generate a light beam (3, 203, 303) adapted in size for comprehensively illuminating the visible front area section (10A, 210A, 310A) such that at least a portion of the light beam (3, 203, 303) passes through the luminous layer (10, 210, 310) before and after being reflected by the reflective surface (8A), thereby forming an illuminating light beam (3A) at a second color associated with a direct light correlated color temperature, and wherein the first color and the second color are separated in color space. The illumination system (1, 100, 200, 300) is further configured such that a perceivable light emission from a frame-like area next to and surrounding the visible front area (10A, 210A, 310A) section is essentially independent from the light beam (3, 203, 303) of the light projector (2, 202, 302).

TECHNICAL FIELD

The present disclosure relates generally to lighting systems, in particular to lighting systems for optically providing a widened perception/impression of the ambient space and in particular for imitating natural sunlight illumination. Moreover, the present disclosure relates generally to implementing such a lighting system, for example, in an indoor room or an outdoor environment.

BACKGROUND

The improvements in mirror manufacturing techniques during the 16th century caused an increasing use of optical mirror elements in interior architecture. For example, the overlay of a portion of a wall with a reflective surface generated the impression of space enhancement and an increase of depth perception. Since then, mirrors became essential components capable of improving the comfort of an ambience through a widening in the perceived volume, virtually doubling the size of the room. In modern and contemporary architecture, reflective surfaces are used, for example, to mirror the scene of a room, thereby giving in fact the feeling of a twin ambience existing behind the “mirror.”

Several applications such as EP 2 304 478 A1, EP 2 304 480 A1, and WO 2014/076656 A1, filed by the same applicants, disclose lighting systems that use a light source producing visible light, and a panel containing nanoparticles used in transmission, i.e. the light source and the illuminated area are positioned on opposing sides of the panel. During operation of those lighting systems, the panel receives the light from the light source and acts in transmission as a so-called Rayleigh diffuser, namely it diffuses light rays similarly to the earth atmosphere in clear-sky conditions. Specifically, the concept uses directional light with lower correlated color temperature (CCT), which corresponds to sunlight and generates shadows in presence of lit objects, and diffuse light with larger CCT, which corresponds to the light of the blue sky and, in principal, can generate shadows with a blue tinge.

The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.

SUMMARY OF THE DISCLOSURE

In an aspect, an illumination system for providing an optically widened perception comprises a reflector unit comprising a reflective surface and a luminous layer for homogenously emitting diffuse light at a first color, the luminous layer extending in front of the reflective surface and comprising a visible front area section of the reflector unit, which extends up to a first boundary and through which the diffuse light is emitted. The illumination system comprises further a light projector configured to generate a light beam adapted in size for comprehensively illuminating the visible front area section such that at least a portion of the light beam passes through the luminous layer before and after being reflected by the reflective surface, thereby forming an illuminating light beam at a second color associated with a direct light correlated color temperature, and wherein the first color and the second color are separated in color space.

In another aspect, an indoor illumination system installation comprises such an illumination system. The indoor illumination system installation may further comprise a room or a cabin such as room of a house, an elevator cabin, a hallway, or a hospital room having mounted therein the illumination system as described above.

In some embodiments, the illumination system is further configured such that a perceivable light emission from a frame-like area next to and surrounding the visible front area section is essentially independent from the light beam of the light projector.

Further embodiments of the above aspects, are disclosed in the claims, which are incorporated herein by reference. For example, in some embodiments, the reflector unit can be, for example, a mirror structure as disclosed in the above mentioned PCT application PCT/EP2014/059802, filed on 13 May 2014 by the same applicants and entitled “Chromatic Mirror, Chromatic Panel and Applications thereof,”, which is incorporated herein by reference. In particular, PCT application PCT/EP2014/059802 discloses a mirror with a mirroring surface and a diffusing layer in front of the mirroring surface that is used, for example, to illuminate an object of an exhibition in a sun-like manner. The diffusing layer preferentially scatters short-wavelength components of impinging light with respect to long-wavelength components of the impinging light. For example, the scattering occurs in the Rayleigh or Rayleigh-like regime.

In some embodiments, a secondary luminous layer associated light source is used, for example, for an additional illumination of the luminous layer from the side. Exemplary embodiments are disclosed, for example, in WO 2009/156347 A1. In those embodiments, the luminous layer may be configured to interact primarily with the light of that secondary light source or with the light from both light sources to provide for the diffuse light.

In some embodiments, a CCT of the diffuse light component from the luminous layer (e.g. in those propagation directions not associated with the illuminating light beam) is 1.2 times larger than the CCT of the light of the illuminating light beam.

In some embodiments, the light beam coming from the light source passes twice through the luminous layer. In some embodiments, the reflective surface is planar or curved such as a parabola. In some embodiments, the reflective surface is encompassed by a framing element, which, for example, is at least partly in relief-shape with respect to the reflective surface or is at least partly recessed with respect to the reflective surface (e.g. comprises a recessed notch or groove).

In some embodiments, the luminous layer comprises a Rayleigh diffuser.

DETAILED DESCRIPTION

The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.

The disclosure is based in part on the realization that directing a bright, directional light beam of a light projector onto a diffusing panel integrated in a reflector unit (in the sense that the light beam is directed onto a mirror surface behind the panel) can significantly increase the depth perception compared to a plane mirror, without essentially requiring any space in an indoor installation behind the mirror.

In such configurations, the brain is brought to compare and to reference the bright luminous peak consisting in the exit pupil of the light projector to the surroundings such as a frame of the reflector unit, in particular in terms of relative position estimations and depth estimations. In other words, an observer will start comparing the bright peak and the edge of the reflector unit in terms of depth cues: depth of focus, motion parallax, binocular parallax, etc.

Due to those depth cues and their typical ranges of efficacy, the observer may start perceiving the light source encompassed by the surroundings of the reflector unit as being positioned at a large distance, ideally infinite distance, behind the reflector unit, when the projector's pupil is positioned at a respective distance from the mirror. The result is a—at least partial—breakthrough effect giving the observer a sense of widened perception or impression of the ambient space. The result may occur at distances between the projector's pupil and the reflector unit for large rooms/outdoors in the range of 2 m and more, for indoor applications in the range of 1 m and more, and for small environments such as seat arrangements in cars, trains or planes in the range of 0.4 m and more. A further aspect of the sun-imitation is providing a projector angular pupil size, i.e. the angular size of the imitated sun as evaluated by an observer, in a position—downstream of the light projector along the reflected illuminating light beam at a distance from the reflector unit comparable to the distance from the reflector unit to the light projector, to be in the range of 5° and smaller such 2° or 3° (the real sun providing 0.5°).

It was further realized that typically the high luminance of the light source, e.g. the high luminance of an exit pupil of the light projector, tends to dominate—in terms of visual perception of the observer in the room—over the lower luminance of the rest of the scene reflected by the mirror. The former, however, may offer a reference to the observer that generally may emerge from the background, and the human visual system may continue to perceive the surrounding scene. Thereby, the breakthrough effect driven by the light source may be reduced (or may even collapse from infinite to finite) due to intermediate references that are introduced by different objects and planes of depth of the scene. Those objects and planes of depth may cancel the effect of a source at infinite distance and enforce a depth perception based on the real, finite case.

Thus, it was further realized that the effect of perception of infinite space/infinite distances beyond the reflector unit may remain in effect, if the objects in the ambience are excluded from perception within the reflector unit/mirror. Specifically, it was realized that such an exclusion may be ensured if one overlays a in particular uniform, luminous, for example diffusive, layer to the mirror surface. In this context, the luminous layer acts as a contrast suppressing unit that suppresses optical perception of the vision of the background. A luminous layer can be provided in various ways as disclosed below such as a scattering layer, diffusing part of a light beam projected by a light source, a luminescent layer, a side-lit panel, etc. In general, the luminous layer may be the basis of diffusive light which is emitted in a wide scattering angle. Moreover, a uniformity of the perception of the luminous layer may further increase the separation of a reflected light beam from its “surrounding” on the reflector unit.

Although the luminous diffusive layer may not offer any specific depth cue plainly by being uniform (e.g. not having any visible, macroscopic structure able to catch the vision, or able to drive the focusing mechanisms and/or to be resolvable by the eye), an additional haze provided to overlap any mirroring feature may act as a contrast suppressor of those optical signals caused by in particular highly luminous background structures.

In other words, providing a luminous layer may overcome the technical problem of the breakthrough reduction above described, e.g. by drowning the luminance of the scene (walls, furniture, etc.) well beneath the level of the luminance of the luminous diffusive layer. Here, it may be provided that the luminance of the layer is significantly higher than the luminance of the scene but much lower than the luminance of the light source.

It was further realized that an observer may be brought to perceive essentially three main elements inside the field of view defined by the reflector unit: the bright peak, the uniform luminance background, and the direct surrounding of the luminous layer herein referred to as the frame-like area.

Further is was realized that in the reflective configuration—in contrast to the transmissive configurations mentioned above—the light beam may extend laterally beyond of the luminous layer and in particular beyond a visible front area portion of the luminous layer. Thus, the light beam may affect the visual perception of the frame-like area, which again may affect the impression of light beam/projection based illumination. Thus, it was realized that special care to reduce or even to avoid any visual impression of such a light beam based illumination of the frame-like area may increase the effect of widened perception.

As one type of configurations, it was realized that one may introduce a frame element positioned in the frame-like area to form a frame area section of the reflector unit that extends outside of the visible front area section and at least partly along the first boundary. The frame element may be configured to essentially avoid contribution of the light portion of the light beam incident onto the frame area section to the illuminating light beam such that in particular light of the light beam incident onto the frame area section is essentially removed from the illumination system by, for example, absorption, reflection, and/or light guidance.

As another type of configurations, it was realized that one may at least partly adapt the size of the light beam to not extend at least into some section of the frame-like area. For example, it was realized that by forming a second boundary of the light beam, which at least partly follows a first boundary, e.g. does completely illuminate the visible front area section of the luminous layer but does not illuminate beyond the same, a reduction of the light beam based illumination of the frame-like area may be achieved. For such a limitation and adaptation of the light beam (in particular its shape and size), the light projector may comprise, for example, an optical system. Moreover, a control configuration may be provided to maintain the matching of the light beam's outer boundary and the luminous layer's outer boundary.

As another type of configurations, it was realized that one may configure the illumination system such that light of the light beam may freely pass by the visible front area section. Specifically, at least a large portion, with respect to the perception of an observer, will, for example, not fall onto a structure that would link the observer of the reflector unit to a light beam illumination. For example, it was realized that the reflector unit may be mounted at the top end of a post such that the light beam only illuminates the visible front section, or that illuminates under a large incident angle to spatially separate any light beam encountered structure from the reflector unit.

It was further realized that the various types of configurations may be applied in combination, e.g. providing a frame element in some section and a perfect adaptation of the beam shape in another section of the frame-like area.

Moreover, it was realized that providing the light emitted by the luminous layer with a color (for example, bluish, sky-like, e.g. in the range from 7000 K and more), the obtained blue background within, for example, a frame element structure may further enhance the depth perception. In particular, the blue color may be associated to aerial perspective. This may further shift the perceived distance of the intermediate-luminance layer to infinity similarly to what happens in the vision of landscape elements at great distances from the observer.

In is noted that the overall effect may resemble an open window through which the sky and the sun are seen. In other words, the perception induced in the observer is that produced by a window, opened to a bright sun at infinite distance surrounded by blue sky.

Moreover, referring to those lighting systems discussed above using a panel in transmission, the present disclosure is based in part on the realization that creating an infinite depth perception using those “transmissive” lighting systems may require a significant volume beyond/behind the panel where the light projector is positioned (for example, at a displacement of several meters from the panel). Even when using folding mirrors, thereby folding the required optical path length and reducing the depth of the system, the final size of the transmissive configuration can result in a significant loss of space in indoor installations. In contrast, using reflective configurations as disclosed herein may allow an efficient use of indoor space.

In the following, exemplary configurations of an illumination system are described, where in particular in connection withFIGS. 1 to 4frame-type configurations, in connection withFIGS. 5 to 7frame-like configurations, and in connection withFIGS. 8 to 10“ideal fit” configurations are disclosed. Exemplary indoor and outdoor installations are described in connection withFIGS. 11A to 13. In connection withFIGS. 14A and 14B, an exemplary side-lit configuration of a reflector unit is described. Aspects of light distribution, coloring, and color measuring are described in connection withFIGS. 15 and 16.

Referring toFIG. 1, aspects of an optical setup as well as the perceptive aspects of illuminations systems as generally described herein are described for an exemplary frame-based illumination system1.

Illumination system1comprises a light source2, configured to emit light in an emission solid angle to form a light beam3(inFIG. 1delimited by dashed lines13) propagating along a main light beam direction4(also referred to as main beam axis). Generally, light source2can be, for example, a cool white light source. Exemplary embodiments of light sources may comprise LED based light emitters or discharge lamp based light emitters or hydrargyrum medium-arc iodide lamp based light emitters or halogen lamp based light emitters and respective optical systems downstream of the respective light emitter.

Regarding light sources applicable to the technology disclosed herein, it is further referred to PCT/EP2014/001293, entitled “Light source and sunlight imitating lighting system,” filed on 14 May 2014 by the same applicants, the contents of which are herein incorporated in their entirety. In particular PCT/EP2014/001293 illustrates light source configurations providing high quality light beams.

To reduce the dimension of illumination system1, the optical systems downstream of the respective light emitter may include an optical system such as folding optics (not shown in the embodiment ofFIG. 1) or aperture based imaging (see, for example, the description below in connection withFIGS. 9A, 9B, and 10). For the optical imaging system, there may be geometric conditions on, for example reflected, light rays of the light beam to be specifically matched in dimension with downstream optical components.

Illumination system1further includes a reflector unit6that couples the light originating from light source2to a region to be lit up, for example an interior room of a building or an outside environment. In general, reflector unit6comprises a reflective structure8providing a reflective surface8A and a luminous layer10.

Reflective surface8A is generally any type of optical acting interface that reflects light having passed through luminous layer10. For example, reflective surface8A may be a surface of an aluminum layer or an interface between components, such as a reflective coating. Due to reflective surface8A, light of light beam3being incident on reflective surface8A is redirected to pass again through luminous layer10, thereafter forming an illuminating light beam3A (inFIG. 1delimited by dash-dash-dotted lines7A). InFIG. 1, a range7of sun-observer locations is illustrated, where it is referred in the wording “sun-observer locations” exemplarily to the “sun” because an especially impressive type of embodiments of illumination system1relates to sun-like illumination. Illuminating light beam3A is, thus, directed in the to be illuminated region that may be indoors or outdoors and comprises directed light (later also referred to as directed (light) component of the illumination system).

Luminous layer10is generally configured for emitting diffuse light (later also referred to as diffuse (light) component of the illumination system) at a first color, e.g. in case of a sky imitation a bluish sky color. Luminous layer10is superimposed to reflective surface8A, extends in front of reflective surface8A, and comprises a visible front area section10A of reflector unit6that an observer can see when looking at reflector unit6. Visible front area section10A extends up to a first boundary12A (forming a closed line). Through/from visible front area section10A, the diffuse light component is emitted.

In the exemplary embodiment ofFIG. 1, a frame-like area extends next to and surrounding visible front area section10A.

Light source2provides light beam3that is adapted in size for comprehensively illuminating visible front area section10A. In particular for a consistent perception in a sun imitating configuration, the comprehensive illumination will ensure that the sun is seen until it vanishes behind first boundary12A when an observer moves across the to be illuminated region (see also the description ofFIGS. 2A to 2D). Moreover, in case of the passive generation of light by luminous layer10as discussed below, the comprehensive illumination of visible front area section10A results in the complete visible front area section10A contributing to and generating the diffuse light component at the first color.

Comprehensively illuminating visible front area section10A ensures further that at least a portion of light beam3passes through luminous layer10before and after being reflected by reflective surface8A. As reflective surface8A extends similarly up to first boundary12A, it is ensured that illuminating light beam3A corresponds in size to first boundary12A. Illuminating light beam3A has a second color that is associated with, e.g., an illuminating light beam CCT. The first color associated with light emitted from luminous layer10and the second color associated with illuminating light beam3A are separated in color space.

For example, the first color and the second color may be separated in the CIE 1976 (u′,v′) color space by, at least 0.008 such as at least 0.01, 0.025, or 0.04, where the color difference Δu′v′ is defined as the Euclidean distance in the u′v′ color space. In particular for sun-imitation configurations, the illuminating light beam CCT of the second color may be close to the Planckian locus (e.g. in the range from 800 K to 6 500 K). In some embodiments the second color may correspond to u′v′ points with a maximum distance from the Planckian locus of e.g. 0.06. In other words, a distance from the Planckian locus is, for example in the range from 800 K to 6500 K, given by Δu′v′≤0.060. In this context, it is also referred toFIG. 15and the related disclosure.

As it is apparent to the skilled person, depending on any interaction of luminous layer10with light beam3, the color and/or CCT of light beam3and illuminating light beam3A may be essentially identical or may differ. Depending from the type of nanoparticles and their concentration, the CCT difference may be, for example, at least 300 K or even 1 000 K or more.

In the embodiment ofFIG. 1, reflector unit6further comprises a frame element14positioned in the frame-like area to form a frame area section14A of reflector unit6that extends outside of and next to visible front area section12A. Frame area section14A borders to and extends at least partly, for example at one or two sides, along first boundary12A.

In general, frame element14is configured to essentially avoid or at least reduce any contribution of the light portion of light beam3incident onto frame area section14A to the illuminating light beam3A. In consequence, any light incident on frame area section14A may no longer be perceived as illuminating the frame area section14A of illumination system1. For example, any light of light beam3incident onto frame area section14A is essentially removed from illumination system1by, for example, absorption, reflection, and/or light guidance. Alternatively or additionally, configurations of the frame's surface structure in relief, e.g. being embossed, may provide for a discontinuity with respect to the perception of the visible front area and, thereby, may form a basic condition that makes the light form the frame area section14A perceivable as being independent from light beam3.

In addition or alternatively, the perception of frame area section14A may be disconnected from light beam3by providing an absorptance (i.e. the ratio of the absorbed radiant or luminous flux to the incident flux, in line with designation: E284-09a of Standard Terminology of Appearance), e.g. an absorptance in the range of or. more than 60%. However, in dependence of the general—the perception affecting—conditions such as the depth of the surface modulation and the size of the illumination system in general, also essentially bright colorings of the frame area section14A may be acceptable such as the frame being white or grey.

Looking from within range7onto reflector unit6, an observer may have an optical perception as schematically indicated inFIG. 1within range7. The optical perception essentially depends on reflector unit6and the light coming therefrom as illustrated by dash-dotted lines7B being specific for the respective observer position. Specifically, illumination system1is configured such that light of significant intensity incident within range7of sun-observer locations originates from within first boundary12A. The light of significant intensity comprises light of light beam3A (originating from light source2and being light of light beam3redirected by reflector unit6), and diffuse light originating from visible front area section10A of reflector unit6, specifically originating from luminous layer10. In addition, the optical perception will—for the embodiment ofFIG. 1—comprise a, for example dark colored, frame-like area around visible front area section10A.

In line with the optical perception illustrated inFIG. 1, the observer, when looking from within range7of sun-observer locations onto reflector unit6, will see a large area16corresponding to visible front area section10A based on the homogenously emitted diffuse light at the first color. Large area16will be surrounded by a frame-like area18that is perceived homogenously or at least as essentially not being illuminated by a light beam because light incident on frame area section14A is removed from illumination system1, and, thus, does no longer take actively part in the perception of reflector unit6. In addition, the observer will see a sun-like spot19at the second color caused by the reflected light of light source2, specifically of illuminating light beam3A.

Reflector unit6may be of any shape such as a (planar) rectangular, quadratic, or circular shape. Reflector unit6is at least partly reflecting the light of light source2. Luminous layer10of reflector unit6may operate as a diffuse light generator such as a Rayleigh diffuser, which substantially does not absorb light in the visible range and which diffuses more efficiently the short-wavelength in respect to the long-wavelength components of the impinging light. Optical properties and microscopic characteristic of Rayleigh like diffusers are described in detail for the above mentioned transmissive type patent applications such as. in EP 2 304 478 A1.

In some embodiments, reflector unit6provides luminous layer10to diffuse the light of light source2, herein referred to as passive diffuse light generation. For passive diffuse light generation, under the asumption that light beam3diverges enough to illuminate completely visible front area section10A, reflector unit6will separate light beam3in two components, originating from the complete visible front area section10A, particularly in:

a reflected (directed non-diffuse) component, formed by light rays that pass twice through luminous layer10and do not experience significant deviations besides the reflection by reflective surface8A; e.g. is formed by light rays experiencing a deviation smaller than, e.g., 0.1° with respect to each other; a luminous flux of the transmitted component is a significant fraction of the overall luminous flux incident on luminous layer10; in some embodiments, luminous layer10may be configured to overlay a low angle white scattering feature onto the incoming light beam, thereby the illuminating light beam may comprise a spread of directions within a small cone (e.g. below 5°) but such a modified illuminating light beam is still, for the purpose of this disclosure, considered to be a directed light beam (it is noted that such a low angle scattering may allow averaging out an inhomogeneity over the light source aperture; and

a diffuse component, formed by scattered light exiting luminous layer10through visible front area section10A (with the exception of that illuminating light beam direction and of directions differing from that illuminating light beam direction by an angle smaller than 0.1°); the diffuse component includes scattered light directly exiting luminous layer10and scattered light being reflected by reflective surface8A; a luminous flux of the diffuse component may correspond to a blue skylight fraction generated from the overall luminous flux incident on luminous layer10.

For the passive scattered light generation, the optical properties of luminous layer10may be such that

the fraction of the diffuse component is within the range from 5% to 50% such as within the range from 7% to 40%, or even in the range from 10% to 30%, or within the range from 15% to 20% with respect to the total light falling onto visible front area section10A (in this respect, the low angle scattering is not considered to contribute to the diffuse component);

the average CCT of the diffuse component is significantly higher than the average correlated color temperature CCT of the reflected component e.g. at angles smaller 0.1°, for example it may be higher by a factor of 1.2, or 1.3, or 1.5 or more;

luminous layer10does not absorb significantly incident light, namely the sum of the two components is at least equal to 80%, or 90%, or even 95%, or 97% or more;

luminous layer10may scatter mostly forward, namely more than 1.1, or 1.3, or even 1.5, or 2 two times more than is back scattered; forward scattered light during the first passage being reflected by reflective surface8A; and

luminous layer10itself may have low reflection, namely less than a portion of 9%, or 6%, or even less than 3%, or 2% of the impinging light of light beam3is reflected.

In other embodiments, luminous layer10may at least partly be illuminated by a separate light source adapted to provide light as the basis for the diffuse component as described below in connection withFIGS. 14A and 14Bfor a side-lit configuration.

In general, light source2may illuminate the front surface of luminous layer10in its entirety under an angle of incidence of beam axis to the normal of the reflector within the range from, for example, about 15° to about 70° such as, for example, 50° for an angled incidence, or about 20° for a steep incidence. In some embodiments, light source2may be arranged essentially vertically below, for example, the center of luminous layer10, when, for example, luminous layer10is tilted with respect to the plane of a room ceiling. The angle of aperture (full aperture) of the light beam may be in the range from about 10° to about 60°.

In general, reflector unit6is positioned in the far field of light source2such that it interacts with a light beam as schematically illustrated inFIG. 1and described below in more detail. High quality light beams—having, for example, projector angular pupil size in the range of 5° and smaller—may allow light source2to provide a sun-like impression.

FIG. 1illustrates exemplarily light beam3as a divergent light beam in the far field. The far field depends on the near field as generated by light source2and is characterized by main light beam direction4. The local propagation direction across divergent light beam3, i.e. a propagation direction of the directed non-diffuse light, is modified/changes in dependence of the position within the cross-section of divergent light beam3as wells as of illuminating light beam3A. Exemplarily illustrated for light beam3but similarly applicable to illuminating light beam3A, a central propagation direction22is essentially parallel to main light beam direction4in an inner area of light beam3. However, a propagation direction24is increasingly inclined with respect to main light beam direction4with increasing distance from the inner area. Exemplarily, a maximum angle of 5° is indicated inFIG. 1for the light beam portion being the furthest out, which corresponds to a beam divergence (also referred to as total angular spread in the far field) of 2×5°=10° of divergent light beam3as wells as of illuminating light beam3A.

In general, light source2may include an emitter unit, a collimation unit, and a homogenization unit, which are those optical units that define an optical near field and emit light through a light source exit aperture that is, for example, fully flashed and represents a light emitting surface with a homogeneous luminance and an etendue that maintained as much of the original etendue of the emitter unit.

Light source2may further include an electronic control unit (not shown) for providing the electronic background to operating the primary light generation process that takes place in emitter unit. Similarly, light source2may include structural components such as a housing to provide support for the optical units and position them in a fixed manner with respect to each other. Moreover, the generated light is adaptable to the specific aspects of respective illumination conditions. In particular it may be adapted to the interaction with reflector unit6, e.g. to provide a desired color of the diffuse and directed component. The adaptation relates inter alia to the emission direction distribution, the color spectrum, and the intensity distribution.

For example, light source2provides light in the visible region of the light spectrum with wavelengths between 400 nm and 700 nm with a spectral width larger than 100 nm, e.g. larger than 170 nm.

In dependence of respective embodiments, the distance between light source2and reflector unit6may be in the range from 1.5 m to 7 m for a light source having an exit aperture of, for example, 0.15 m. For such a situation, an optical distance between the light source and the observer is, for example, in the range from at least 2.5 m to 9 m or more.

For the herein disclosed lighting systems, the required total angular spread in the far field depends on the distance to and the size of the to be illuminated reflector unit6. Orthogonal total angular spreads of 10° and 30°, respectively, for a rectangular object (reflector unit6) with size 1 m×2 m being illuminated under 45° provide an acceptable distance between light source2and reflector unit6. As will be apparent to the skilled person, total angular spreads in the range from 5° to 60° or in the range from 5° to 50° would be applicable for some of those lighting systems discussed herein and respective shapes of reflector units6.

As indicated above, light source2may be designed to have or may be adaptable to provide specific shapes of light beam3that are specifically adapted to completely illuminate visible front area section10A. Respective light sources may include an optical system to limit and to adapt a size of light beam3. For example, light sources may include a zoom lens system and/or a beam shape defining imaging system such as a fly's eye configuration, an essentially ideal CPC configuration, a transmissive aperture, and/or reflective aperture based imaging system upstream of the reflector unit, thereby in particular at least partly adapting the size of the light beam and forming a second boundary which at least partly follows first boundary12A. Exemplary configurations are disclosed below in connection withFIGS. 9A, 9B, and 10.

Referring again to the optical perception as illustrated inFIG. 1, first boundary12A delimits visible front area section10A. A second boundary13A corresponding to dashed lines13is formed on reflector unit6. Second boundary13A corresponds to the lateral extend of light beam3as it is given, for example, for a flat top beam having a steep decrease in luminance in radial direction in the region of second boundary13A.

Light beam3is at least as large so as to completely illuminate visible front area section10A. In the embodiment ofFIG. 1, second boundary13A will accordingly result on frame area section14A in an inner region being illuminated by light beam3and an outer region not being illuminated by light beam3. On dark frame-like area18, a dashed line18A illustrates a corresponding transition line between those regions. However, as frame area section14A is configured to not be affected in its visual appearance due to impinging light, dark frame-like area18is essentially seen as being not illuminated at its inner region by light beam3.

As only the beam portion falling within first boundary12A is reflected, illuminating light beam3A will in its lateral extent be defined by the size of visible front area section10A as indicated inFIG. 1by dash-dash-dotted line7A illustrating a third boundary and defining range7of sun-observer locations. It is noted that, when being outside of range7of sun-observer locations, an observer will—when looking at reflector unit6—notice an essentially homogenously emitting diffuse light area. The diffuse light may be in the color spectrum of the sky, and, in the embodiment ofFIG. 1, surrounded by frame elements14but without sun-like spot19as the reflective arrangement does not allow the observer to see the exit pupil of light source2. In addition, an observer—being within or outside of range7of sun-observer locations—sees collimated light of light beam3A illuminating any surface positioned within range7of sun-observer locations. Thereby, the perception of the sun-light imitation may be enforced.

It is noted further thatFIG. 1illustrates the components of reflector unit6individually and separated from each other for illustration purposes. However, the skilled person will understand that the various components are as “close” with respect to each other as their functions require. For example, reflective structure8and thus reflective surface8A may be in contact with the back side of luminous layer10. Frame element14may be as close as necessary to luminous layer10to ensure an observer being in range7of sun-observer locations not to resolve any optical inconsistencies.

Moreover, as shown inFIG. 1, frame area section14A and visual front area section10A of the front face of reflector unit may be positioned in a plane (e.g. curved or planar plane), thereby providing the impression of a flat continuous front face.

In general, frame element14may be positioned to create a light beam shadow zone (i.e. a region downstream of frame element not subject to illumination by light beam3) that essentially does not overlap with the visible front area section10A. This in particular may ensure complete illumination of the same as discussed below in combination withFIGS. 2A to 2D. Again, the extent of the shadow zone is limited to ensure an observer being in range7of sun-observer locations not to resolve any optical inconsistencies, in this case, for example, an unevenness of the diffuse component emitted through visible front area section10A.

The skilled person will recognize those aspects and features disclosed in connection withFIG. 1that equally will be applicable to the embodiments disclosed below in connection with the remaining figures. This applies, for example, to the luminous layer and the light source as well as the discussion of the light propagation. To simplify the following figures, only some of the reference numerals are included, which generally are used for describing differences between embodiments.

Returning to frame element14shown inFIG. 1, a surface configuration and/or a structural configuration of the frame element(s) may be, in general, configured to absorb at least 60% of a light portion of light beam3incident onto the respective frame area section. Specifically, an absorptance of at least 60% may be given in the visible spectrum (e.g. in the range between 400 nm and 700 nm), or at least in the portion of the visible spectrum in which a power spectral density of the projector is larger than 10% its peak value. For that purpose, frame element14may be provided with a light absorbing color.

In connection withFIG. 2, exemplary configurations of a frame element14B and a frame element14C are disclosed.

With respect to structural configurations, frame element14B may comprise coarse grain structures, large structures, decorations, and/or patchy finishing, for example, on the scale of the frame width such as 0.02 to 0.2 of the frame width. For example, a frame element with a coarse grain structure may comprise large (e.g. macroscopical, visible) structures such as a chessboard, foliage, random decorations, or fractal patterns that are painted or printed (2D) or molded/finished in relief (3D) with average grain/cell size on the scale 0.02-0.4 times the width of the frame. In addition or alternatively, the frame element may be provided with an absorptance modulation such that at least 5% of the surface area of the frame element differs in absorptance from the average value (on the frame element) by more than 10%. In general, the structured surface may result in an unevenness in optical appearance that even when partly illuminated may not allow or at least largely hinder any associating of the appearance of the frame to illumination by light beam3. However, the elevation of the structure should again not affect the complete illumination of the visible front area section.

Furthermore, sections of the frame element such as frame element14C being downstream of visible front area section10A may be tilted with respect to the plane of visible front area section10A to increase the angle of incidence and to reduce the visibility of the transition from within range7of sun-observer locations. In particular, the aspect of shadow extension may not apply to those sections of a frame element.

FIGS. 2A and 2Billustrate the influence of a comprehensive illumination, which is in particular important at that transition in and out of range7. At that transition, the aperture of light source2will enter the field of view. For complete illumination (shown inFIG. 2Afor a frame configuration and inFIG. 2Bfor a ideal fit configuration described in more detail below), the “sun” will appear (and disappear) exactly at the boarder of large area16.

In contrast, referring toFIG. 2C, assuming that frame14B generates a shadow zone26on visible front area section10A, light beam3illuminates only a part16′ of visible front area section10A. Thus, the perception of visible front area section10A (assumed to relate to a passive configuration) is split in two portions of different appearances—one being illuminated and one being in the shadow zone26. Moreover, “sun”19′ will appear at the border between shadow zone26and part16′ of visible front area section10A, i.e. at a distance to the frame, thereby reducing the sun-like impression.

For an active configuration of a luminous layer, as shown inFIG. 2D, large area16would in its generation of diffusive light not be affected by shadow zone26. However, “sun”19′ related to the (first) light source will appear at the boarder between shadow zone26as inFIG. 2C, i.e. at a distance to frame-like area18and in the middle of large area16, thereby similarly reducing the sun-like impression.

FIGS. 3A and 3Bas well asFIG. 4illustrate configurations of the frame element that remove—from illumination system1—the light of light beam3that hits next to visible front area section10A onto frame element14.

Specifically,FIG. 3A(schematic front view) andFIG. 3B(schematic cross-sectional view) illustrate a light trap28A for the case of near vertical incident light rays29A (indicated by arrows) onto a circular reflector unit6A. The incidence angles may be, for example, in the range from α=5° to 35°. Light trap28A is configured as a reflective frame (e.g. mirror based redirecting frame) that is able to guide incoming light, e.g. at least a portion of light beam3falling out of visible front area section10A, away. For example, light trap28A may deflect and, thereby, may redirect any potentially spurious light towards a dark wall31within light trap28A (the wall31having e.g. an absorptance as discussed above, e.g. of at least 60%). In addition or alternatively, light trap28A may redirect the right/left behind reflector unit6A. For a near orthogonal incidence, for example in the range from α=5° to 15°, essentially a rotation symmetric light trap28A surrounding the visible front area section10A may be provided as shown inFIG. 3A.

FIG. 4illustrates an alternative embodiment of a reflective unit6B with a frame element for use in particular in large angle incidence configurations in the range from α=55° to 70° (light rays29B indicated again as arrows). As shown inFIG. 4, a light trap28B is provided only at the downstream side of visible front area section10A, again configured for guiding the light away, e.g. onto an absorbing surface within light trap28B.

The light traps illustrated above are exemplary embodiments of frame elements that are at least partly recessed with respect to the visible front area section such as by comprising a recess such as a notch or a groove. The recess may in particular be configured to absorb the incident light on its wall surface(s).

In the respective embodiment ofFIG. 4, upstream and top/down (left/right) of visible front area section10A, no frame element may be provided, thereby either simply letting the respective section of the light beam pass behind reflector unit6and/or adapting the size and shape of the light beam accordingly (see also the following embodiment).

FIG. 5illustrates an embodiment of an illumination system100not relying on a frame element provided right next to luminous layer110, but instead on adapting the background provided downstream of a reflector unit106illuminated under an angle by a light source102. Specifically, reflector unit106is mounted with some distance to a wall configuration132such as an indoor room delimiting wall section or an outdoor wall configuration. Wall configuration132may be provided together with reflector unit106and may partly act as a portion of illumination system100.

Wall configuration132comprises inter alia a background wall section132A in front of which reflector unit106is positioned and mounted. In addition or alternatively, wall configuration132comprises a light subjected wall section132B. Onto both sections, light beam portions103A,103B of light beam103, which pass by reflector unit106, is incident.

At least one of background wall section132A and light subjected wall section132B may be provided with a light absorbing color and/or may comprise coarse grain structures, large structures, decorations, and/or patchy finishing as described above for frame element14B in connection withFIG. 2. In light of the absorption and the potentially spatial remoteness between the light impinging area on the wall sections and reflector unit, the visual perception of reflector unit106may be essentially unaffected by light beam portions132A,132B passing reflector unit106.

In general, a reflector unit may be adjustable in position and orientation, thereby affecting the location of range107of sun-observer locations.

The embodiment shown inFIG. 5exemplarily illustrates the concept of redirectable mirror units. Specifically, an adaptable mount136is schematically shown to be attached at the backside of reflector unit106. Specifically, mount136may turn reflector unit106within a preset angular range, thereby also enforcing a movement of the “sun.” Wall configuration132may be configured to provide respective remoteness of light beam portions132A,132B passing by reflector unit106for varying angular positions of reflector unit106. Thus, one may achieve that the desired perception is not lost despite a change in the illumination condition assuming that light beam103is large enough to cover visible front area section110A for any adjustable position. For example, turning reflector unit106around an axis138, may result in pivoting range7along arrow139, thereby resembling the movement of the sun for a stationary observer and, thus, strengthening the impression of sun-like illumination.

In other words, mount136acts as mechatronic mount system that is configured to mount the reflector unit and to produce an, in particular continuous, movement of the reflector unit to redirect the illuminating light beam into the ambience, thereby in particular resembling the movement of sun rays entering the ambience through a window, for example, for reproducing sunset, afternoon, and dawn sceneries, when, for example, further combined with a change in color of the light beam.

Moreover, the illumination system may be mounted in a non-stationary environment such as a ship, plane, or car, and the illumination system may use the mechatronic system having mounted the reflector unit and/or the light source thereon to compensate for movement of the non-stationary environment. For example, one may additionally provide an orientation detection device such as an accelerometer, a gravity sensor, and/or a tilt sensor for detecting a change in orientation such as inclination of the non-stationary environment such as a pitch and/or a roll of the ship. The control unit may be then configured to drive the mechatronic system to compensate for the change in orientation of the non-stationary environment, thereby in particular producing an illuminating light beam in counter-movement with respect to the non-stationary environment and in particular resembling the case of sunrays entering the non-stationary environment through a window.

As shown inFIG. 6, in some embodiments modification of illumination system100ofFIG. 5, specifically in an illumination system100A, light subjected wall section132B may comprise a window unit134through which the light of light beam103having passed by reflector unit106is guided out of wall configuration132, e.g. into a neighboring room for illumination purposes.

Moreover,FIG. 6illustrates that, for example, at an upstream side of reflector unit106a frame element114may be used. In particular, for the turnable configuration disclosed above, frame element114D may be configured, e.g. in size or light trap configuration, to remove respective light for e.g. all angular positions of reflector unit106.

Generally, the illumination systems disclosed herein may comprise a mount structure having the reflector unit and the light projector mounted thereon. The mount structure may be provided, for example in indoor configurations, by the wall and/or the ceiling and respective mount configurations. However, in particular for outdoor implementations, the mount structure may be in particular configured as a pole having the reflector unit and the light projector mounted thereon.

In the exemplary lighting system200ofFIG. 7a pole240extends, for example, vertically and has a reflector unit206attached far away, e.g. several meters, from ground201. Reflector unit206is illuminated by a light source202similarly attached to pole240in a bottom-up direction, i.e. along the pole direction into the sky. In such a configuration, any light232of light beam203(indicated by arrows) passing by reflector unit206will—with the exception of a mount branch240A—freely propagate to the top, and in an outdoor configuration, propagate into the (night) sky250. In particular, night sky250may act as a frame part and “absorb” any light of light beam203not falling within a visible front area section210A of a luminous layer210. Branch240A may be treated as a frame like element and configured to provide the respective absorption or redirection of any impinging light.

In other words, pole240may be mounted in an environment that provides a free space, for example free of any light scattering or light reflecting structure, of at least 1.5 m behind the reflector unit such that frame elements or the in the following described ideal fit may not be required.

In connection withFIGS. 5 to 7, embodiments of illumination systems were disclosed that may not require or may require only for some section(s) frame element(s). An alternative approach, which also may completely or at least partly make a frame element not required, is based on an ideal fit concept or an at least section-wise ideal fit concept of a light beam. The ideal fit concept matches the size and shape of the light beam at least partly to the visible front area section.

Specifically, in some illumination systems, additionally or alternatively, a matching of the first boundary (delimiting the visible front area section) and the second boundary (delimiting the light beam), specifically the lateral size of light beam, is performed at least for some part of the frame-like area.

The matching/adaptation may be performed using high precision mounts and/or specifically predesigned light source and reflector unit geometries. However, in embodiments prone to relative movement, a control unit may additionally be provided to monitor and to continuously adjust/maintain the matching.

FIG. 8illustrates exemplarily an ideal fit-based illumination system300. Specifically, illumination system300comprises a light projector302with an optical system302A to limit and to adapt a size of light beam303. Optical system302A may include, for example, a zoom lens system and/or a beam shape defining imaging system such as a fly's eye configuration, an essentially ideal CPC configuration, a transmissive aperture, and/or reflective aperture based imaging system upstream of a reflector unit306. Optical system302A may at least partly allow adapting the size and shape of light beam303and forming a second boundary313A, which at least partly follows a first boundary312A of reflector unit306.

Illumination system300further comprises a high precision mount360for mounting and aligning light projector302, and/or a tunable imaging system for adapting second boundary313A (delimiting light beam303) such that in particular at least 85%, for example in the range of 95%, of light beam303illuminate a visible front area section310A of reflector unit306and that at the most 15%, for example in the range of 5%, of the light of light beam303fall outside of first boundary312A.

High precision mount360may further be configured to mount reflector unit306(not shown inFIG. 8). In pre-installed embodiments, the relative position between reflector unit306and light source302may be fixed in dependence of the size of the light beam and the orientation and the position of the reflector unit. In some embodiments, continuous control may be required.

Illumination system300may further comprise a control unit362to control high precision mount360and/or optical to at least partly adapt second boundary313A to first boundary312A.

As a further modification shown inFIG. 8, reflector unit306may comprise, for example, light detectors364close to first boundary310A for providing position information on second boundary313A with respect to first boundary310A. Control unit362may be connected to optical system302A, high precision mount360, and light detectors364via control lines366to control precision mount360and/or optical system302A in response to the position information, thereby in particular ensuring proper and continuous alignment and matching of light beam303with a visible front area section310A of a luminous layer310of reflector unit306.

In ideal fit configurations, light source302is, for example, configured to produce a flat top illumination that is shaped in its boundary to fit to the visible front area section as seen from the light source's point of view.

In general, the light sources disclosed herein may comprise an optical system with an imaging optics that is based on an aperture. The image of the aperture is projected on the reflector unit by a projection optics and the shape of the aperture is tailored in order to match in general the frame-like area of the reflector unit (in case a frame element is present) or the size of the first boundary (in case ideal fit is used). The projection optics may use a lens or a system of lenses to create the image of the aperture on the reflector unit.

In some embodiments, the imaging optics may comprises a fly's eye lens array that is configured so that the second lens of each pair (of lenses) in the array produces the image of the first lens at distance (virtually infinite).

In some embodiments, the imaging optics may comprise an ideal CPC coupled with a light emitter fitting its entrance aperture (smaller aperture).

FIGS. 9A, 9B, and 10illustrate exemplary optical configurations that allow ideal fit implementations of illumination systems400,500as generally described in connection withFIG. 8.

In particular,FIG. 9Ashows a cross section, whileFIG. 9Bshows a partially perspective view of a light beam propagation concept of complete illumination of a reflector unit406comprising a luminous layer set-up having exemplarily an essentially circular visible front area section410A. A mounting structure470mounts a luminous layer410in a manner to at least partly surround visible front area section410A. Mounting structure470may be any type of structural component for holding luminous layer410and may or may not comprise a mounting front side section472. Mounting front side section472may not be specifically adapted to not be affected by illumination by a light beam403at its front side section472or it may, for precaution, be configured as disclosed above with respect to a frame element.

To allow such a flexibility with respect to the front side area surrounding visible front area section410A, the ideal matching of the extension of light beam403to the extension of visible front area section410A is used. For that purpose, light beam403may be configured as a flat top light beam for which a significant intensity only extends up to a second boundary413A.

To generate such a beam shape, an aperture structure474comprises an opening474A that in shape is identical to the projection of the tilted visible front area section410A onto a plane404A orthogonal to the main beam axis (direction404). Besides the adaptation to the shape of that projection, the beam divergence is adjusted such that the size of the respective shapes are identical at the moment when light beam403hits reflector unit406. The divergence is, for example, adaptable by a movable lens476arranged downstream of aperture structure474. For example, lens476and/or aperture structure474are movable in axial direction (indicated as the Z-axis inFIG. 9B) as well as in lateral directions (indicated as X- and Y-axis inFIG. 9B). Mounting stages (not shown) for lens476and aperture structure474may be connected to a control unit (as shown inFIG. 8) and may be driven, for example, in response to control signals received by optical detectors next to visible front area section410A or may be preset during initial installation.

Accordingly, the illustrated imaging system ofFIGS. 9A and 9Ballows adjusting the beam size and beam direction such that essentially only visible front area section410A is illuminated. Thereby, an observer does not notice any light from light source402falling next to visible front area section410A, which could affect any perception of the sun-like imitation, for example.

Accordingly, the illustrated imaging system ofFIGS. 9A and 9Ballows adjusting the beam size and beam direction such that essentially only visible front area section410A is illuminated. Thereby, an observer does not notice any light from light source402falling next to visible front area section410A, which could affect any perception of the sun-like imitation, for example.

FIG. 10illustrates in a three-dimensional view illumination system500with a reflective configuration for adjusting beam size and beam shape with respect to a similarly tilted rectangular reflector unit506. Specifically, reflector unit506is mounted onto a wall (not shown) under an angle of, for example, 30° with respect to the vertical direction.

A light source502is only schematically illustrated and emits light beam503onto a folding mirror580. Folding mirror580is shaped such—provided that the projector is in a specific position—that any beam reflected from folding mirror580will have, when encountering reflector unit506as a next reflective optical element, the same shape as a projection of reflector unit506onto a plane orthogonal to the beam propagation direction (see alsoFIG. 9A). To arrive at the respective shape, light beam503may impinge onto folding mirror580at a specifically preset angle, the shape of folding mirror580being adapted accordingly.

As furthermore shown inFIG. 10, a divergence of light beam503originating from light source502may be selected such that the size of beam503when impinging onto reflector unit506is identical to the respective size of an associated visible front area section510A.

Also for the configurations disclosed in connection withFIGS. 9A, 9B, and 10, an observer looking at the reflector units may not see any light next to the visible front area sections originating from the light source of the illumination system that could disturb a perception of, for example, the sun-like imitation.

Referring again toFIG. 10, the illustrated configuration allows a compact configuration for a drop down illumination within a roof. The skilled person will, however, recognize that additional structural components may be provided to avoid the visibility of folding mirror580from with the range of sun observer positions.

With respect toFIG. 11AandFIG. 11B, indoor installations of illumination systems600and700are schematically illustrated. The indoor installations may be provided in larger halls, rooms of civil housing, or elevator cabins and the like.

FIG. 11Aillustrates a drop-down illumination similar toFIG. 9within a, for example, rectangular room682. Room682comprises accordingly a ceiling682A and four walls, one of which being used to mount a reflector unit606and referred to as reflector unit mounting wall682B. A light source602is provided on top of ceiling682A. Ceiling682A may comprise an opening, for example covered by a, e.g. anti-reflective coated, glass window684. A light beam603of a light source602passes through glass window684and falls onto reflector unit606thereby being reflected into room682. An observer686looking at reflector unit606will primarily see the diffuse light component from any position within room682and the directed light component, when being within the range of sun-perceiving positions (not specifically indicated inFIG. 11A).

As further schematically illustrated inFIG. 11A, a screen structure688covers glass window684and comprises an opening in direction of reflector unit606such that light beam603can pass along and within screen structure688, thereby further hiding the optical configuration of light source602and glass window684from observer686.

In general, the rooms disclosed herein for being illuminated by the illumination systems may be rooms or cabin such as room of a house, an elevator cabin, a hallway, or a hospital room. Within room682or a cabin, a target region may be defined for specific position of an observer of the illumination system. For example, the target region may relate to a person accommodation furniture being present in the room682or cabin such as a bed, hospital bed, seat, couch, or chair. In some embodiments, the target region may relate to an observer path through room682or cabin. The illuminating light beam3A is directed to illuminate the target region. In some embodiments, such as in a hospital environment, the illumination system may be specifically controllable to illuminate the target region in a sun-imitating manner, for example, during the course of the day, e.g. providing incidence angles of the illuminating light beam or respective coloring of the illuminating light beam and/or luminous layer, thereby providing a day-like light/illumination pattern for patients, which may provide optimal awakening conditions and other benefits of the life rhythm.

As a further example, a floor lamp configuration—as an example of a pole based configuration as shown inFIG. 7—is indicated inFIG. 11Afor illuminating an armchair, while inFIG. 12an illumination of a bed, for example, within a windowless hospital room is shown.

FIG. 11Billustrates illumination system700having a light source702mounted within a room782. For example, light source162is mounted at a side wall782B and emits a light beam703directed upwards onto a reflector unit706mounted at a ceiling782A of room782.

Observers786within room782will again primarily see a diffuse light component when looking at reflector unit706and a directed light component when being within the range of sun-perception positions.

Similar toFIG. 11A, a screen structure788may be provided to at least initially hide light source702when guiding light beam703towards reflector unit706. In addition, screen structure788may reduce the possibility of a person within room782to interfere with (e.g. reach into) light beam703and, thereby, to affect the perception of reflector unit706. Screen structure788could be a transparent (e.g. glass) cover or theca (even completely closed on all sides) to prevent people intrusion into light beam703.

The herein disclosed embodiments may in addition comprise a volumetric-motion sensor (such as a passive infrared sensor) for detecting an intrusion of people inside a volume surrounding the light beam upstream the reflector unit. The sensor may be mounted to the light source and/or for example at the screens688,788disclosed in connection withFIGS. 11A and 11B. Moreover, a control unit may be provided for receiving a respective signal from the volumetric-motion sensor and configured to dim or to switch-off any light emission from the light source in case of an intrusion detection.

A further field of application of the herein disclosed illumination systems is the illumination of transportation units, such as trains and airplanes as well as ships. As an example,FIG. 12illustrates a cross-section through a cabin701of an airplane (or train) having a row of seats701A at one side and parallel thereto a zone701B where people may stay or walk such as a hallway or walkway.

The illumination of that zone701B is based on one or several reflector units706A,706B being respectively illuminated by light sources703A,703B. For example, reflector units706A may be provided within the ceiling of cabin701(e.g. surrounded by an area acting frame-like based on dark coloring) or reflector units706B may be provided on the sidewall or the transition between the sidewall and the ceiling. Light sources702A,702B may be positioned, for example, within the overhead luggage structure or mounted along the sidewall.

InFIG. 13, an embodiment of an illumination system800with two light sources802A,802B used in combination with a single reflector unit1806is schematically illustrated. Each of light sources802A,802B results in respective illumination regions890A,890B. Illumination regions890A,890B may be separated by a physical structure892such as a wall to clearly distinguish those illumination reception regions890A,890B and to avoid perception confusion. Alternative samples for physical structure892are furthermore in outdoor/indoor configurations, hedges, trees, or bushes, or small water area and the like.

The skilled person will recognize that the two light source embodiment shown inFIG. 13may be easily extended to three or more light sources. In particular, in indoor configurations thereby specific regions may be illuminated that are close to each other but separated by some structure or space, while each illumination region is subject to its own controllable illumination source.

For the technology related to the luminous layers disclosed herein it is further referred to PCT/EP2012/072648, entitled “Artificial illumination device,” filed on 14 Nov. 2012, and PCT/IB2013/060141, entitled “Artificial lighting system for simulating a natural lighting” by the same applicants the contents of which are herein incorporated in their entirety for illustration purposes of lighting systems using Rayleigh diffusers.

Although the Rayleigh diffusers of the herein disclosed embodiments are exemplarily shown in the drawings to be planar panel-shaped, thereby imitating a window appearance. However, although non-panel-like configurations may be used such as curved structures.

In general, the Rayleigh diffuser may be configured as a passive diffuser or a side-lit diffuser, e.g. a panel illuminated by, for example blue, LEDs from the side. Accordingly, the Rayleigh diffuser may in some embodiments be a secondary light source which emits diffuse light and is nevertheless partially transparent to the light of the (main) light source.

As indicated above, the luminous layer may be based on a passive luminous layer configurations, where the scattering of light of the light beam generates the diffuse light component. However, the luminous layer may be also based on an active luminous layer configuration comprising a secondary luminous layer specific light source configured to generate alone or at least to contribute to the generation of the diffuse light component. For example, the secondary light source or secondary light sources may direct light into the luminous layer from the side.

An example of such an active luminous layer configuration is illustrated inFIG. 14AandFIG. 14B. The general structure of a reflector unit906may comprise—as disclosed for the above embodiments—a reflective structure908with a reflective surface908A and a luminous layer910. In addition, for example, a frame element914may be provided next to luminous layer910.

In addition, for generating (or contributing to the generation) of the diffuse light component, one or more secondary light sources994are provided laterally from luminous layer910, for example behind frame element914. In such a side-lit configuration, secondary light sources994illuminate luminous layer910from the sides, while a light beam of a light source impinges onto visible front area section910A of luminous layer910from the front.

Accordingly, luminous layer910may be specifically configured to interact with light of secondary light sources994. In some embodiments, luminous layer910may be configured not to (or at least very limited or to a reduced extent) interact with the light of light beam3such that the diffuse light component generated by luminous layer910may be based primarily on the light of secondary light source994and only to some extent if at all on light of the primary light source (not shown inFIG. 14A).

FIG. 14Billustrates as an example a round shape of such an active luminous layer configuration comprising a circular secondary light source994A extending around luminous layer910.

FIG. 15shows a schematic uniform chromaticity diagram (also referred to as u′-v′-chromaticity diagram). Therein, points on the border correspond to monochromatic spectra (delta-like); in other words, the wavelengths increase at the curved surface border on the left and top side from, for example, 420 nm at the bottom point to about 510 nm at the top left corner to about 680 nm at the right corner. The coordinates are referred to as u′-chromaticity coordinate and v-′chromaticity coordinate. In addition, a Planckian Locus996is indicated inFIG. 15representing the spectrum of a Planck radiator at respective temperatures, for example, in the range from below 1000 K to about 100 000 K. Planckian locus996further defines the CCT for the various temperatures.

InFIG. 15, color areas are schematically indicated. Specifically, the reddish area is referenced as I, the greenish area as II, and the bluish area as III. The reddish area and the greenish area are essentially separated by Planckian locus996in the range from 2 000 K to 10 000 K, Planckian locus996ending within the bluish area.

For a sun-like imitation, the color of the light beam (specifically the second color associated with the light beam after having passed the reflector unit) will be next to Planckian locus996.

To provide for a respective difference between the first color and the second color resulting in the unique perception, the coordinates of the respective colors within the u′-v′ uniform chromaticity diagram may differ at least in the range from a Δu′v′ of at least 0.008 such as at least 0.01, 0.025, or 0.04. For example, providing the first color in the range of or at least close to Planckian locus996at about 7 0000 K to 10 000 K will result in a blue sky impression and the sun appearing at the second color at e.g. a CCT of 800 K to 6500 K.

Artificial background effects may be achieved moving the first color away from Planckian locus996, for example providing a greenish background.

In connection withFIG. 16a configuration1000for measuring the respective colors of the diffuse light component and the directed light component of illuminating light beam1003A is described. In the exemplary embodiment, an illumination of a reflector unit1006by a light source1002is performed under 45°. Reflector unit1006is mounted in a “dark” corner1032, for example, in front of walls being colored black to absorb any scattering light, for example with an absorptance greater 90%.

As schematically illustrated inFIG. 16, the diffuse light component may be measured with a color spectrometer1098A under 45° positioned outside of a light beam1003, thereby not disturbing the illumination of visible front area section1010A of reflector unit1006and collecting the first color information.

For measuring the second color of the direct light component, a white reference target1099(e.g. a Gray Card target with its 90% reflectivity, white side) is positioned within illuminating light beam1003A in a sun-observer position and oriented perpendicularly to the main direction1004A of illuminating beam1003A. A second color spectrometer1098B is directed onto white reference target1099under 45° with respect to the normal of white reference target1099, thereby collecting the second color information.

Although the above approach for color measurements of the illumination systems described herein may be applicable for many types of configurations, the skilled person will understand that similar or related configurations may also be used for identifying and measuring the respective colors, color differences, and correlated color temperatures.

For the technology of the luminous layer applied in the illumination systems disclosed herein it is further referred to PCT/EP2012/072648, entitled “Artificial illumination device,” filed on 14 Nov. 2012 and PCT/IB2013/060141, entitled “Artificial lighting system for simulating a natural lighting” by the same applicants the contents of which are herein incorporated in their entirety for illustration purposes of lighting systems using Rayleigh diffusers.

For completeness, exemplary features of the luminous layer are summarized below. The luminous layer is, for example, shaped as a panel such as a parallelepiped panel. In particular, the panel may be delimited by two parallel surfaces and may be thin with a thickness, measured along a direction perpendicular to the surfaces, which has a square value not larger than 5%, for example not larger than 1%, of the area of the surfaces.

The luminous layer may be a Rayleigh panel which substantially does not absorb light in the visible range and which diffuses light in the blue wavelength range (around 450 nm) at least 1.2 times, for example at least 1.4 times, such as at least 1.6 times more efficiently than light in the red wavelength range around (around 650 nm), wherein a diffusion efficiency is given by the ratio between the diffuse light radiant power with respect the impinging light radiant power.

In some embodiments, luminous layer comprises a solid matrix of a first material (e.g., a resin or plastics having excellent optical transparency), in which nanoparticles of a second material (e.g. inorganic oxide such as ZnO, TiO2, ZrO2, SiO2, Al2O3) are dispersed. The second material has a refractive index different from the first material's refractive index. Preferably, the first and the second material basically do not absorb electromagnetic radiation in the visible wavelength range.

Moreover, the luminous layer may be uniform, in the sense that, given any point of the luminous layer, the physical characteristics of the luminous layer in that point does not depend on the position of that point. Furthermore, the luminous layer may be monolithic.

In some embodiments, the spherically or otherwise shaped nanoparticles may be monodisperse and/or have an effective diameter D within the range [5 nm-350 nm], such as [10 nm-250 nm], or even [40 nm-180 nm], or [60 nm-150 nm], where the effective diameter D is given by the diameter of the nanoparticles times the first material's refractive index.

Moreover, nanoparticles may be distributed inside the luminous layer in a manner such that their areal density, namely the number N of nanoparticles per square meter, i.e. the number of nanoparticles within a volume element delimited by a portion of the surface of the luminous layer having an area of 1 m2, satisfies the condition N≥Nmin, where:

wherein ν is a dimensional constant equal to 1 meter6, Nmin is expressed as a number/meter2, the effective diameter D is expressed in meters and wherein m is the ratio between the particle and host medium refractive indices.

In some embodiments, the nanoparticles are distributed homogenously, at least as far as the areal density is concerned, i.e. the areal density is substantially uniform on the luminous layer, but the nanoparticle distribution may vary across the luminous layer. The areal density varies, for example, by less than 5% of the mean areal density. The aerial density is here intended as a quantity defined over areas larger 0.25 mm2.

In some embodiments, the areal density varies, so as to compensate illumination differences over the luminous layer, as lit by the light source. For example, the areal density N(x,y) at point (x,y) may be related to the illuminance I(x,y) produced by the light source at point (x,y) via the equation N(x,y)=Nav*Iav/I(x,y)±5%, where Nav and Jay are the averaged illuminance and areal density, these latter quantities being averaged over the surface of the luminous layer. In this case the luminance of the luminous layer may be equalized, in spite of the non-uniformity of the illuminance profile of light source2on the luminous layer. In this context, the luminance is the luminous flux of a beam emanating from a surface (or falling on a surface) in a given direction, per unit of projected area of the surface as viewed from the given direction, and per unit of solid angle, as reported, as an example, in the standard ASTM (American Society for Testing and Materials) E284-09a.

In the limit of small D and small volume fractions (i.e. thick panels) an areal density N≈Nmin is expected to produce scattering efficiency of about 5%. As the number of nanoparticles per unit area gets higher, the scattering efficiency is expected to grow proportionally to N, until multiple scattering or interferences (in case of high volume fraction) occur, which might compromise color quality. The choice of the number of nanoparticles is thus biased by the search for a compromise between scattering efficiency and desired color, as described in detail in EP 2 304 478 A1. Furthermore, as the size of nanoparticles gets larger, the ratio of the forward to backward luminous flux grows, such ratio being equal to one in the Rayleigh limit. Moreover, as the ratio grows, the aperture of the forward scattering cone gets smaller. Therefore, the choice of the ratio is biased by the search for a compromise between having light scattered at large angles and minimizing the flux of backward scattered light. However, in a per se known manner, an antireflection layer (not shown) may be deposited on the luminous layer, with the aim of minimizing reflection.

In some embodiments, nanoparticles may not have a spherical shape; in such case, the effective diameter D can be defined as the effective diameter of the equivalent spherical particles, namely the effective diameter of spherical particles having the same volume as the aforementioned nanoparticles.

Furthermore, in some embodiments, the nanoparticles are polydispersed, i.e. their effective diameters are characterized by a distribution N(D). Such distribution describes the number of nanoparticles per surface unit and unit interval of effective diameter in a neighborhood of the effective diameter D (that is, the number of particles per surface unit having an effective diameter between D1 e D2 is equal to

ND2-D1=∫D1D2⁢N⁡(D)⁢dD).
These effective diameters may fall in the range [5 nm-350 nm], i.e. the distribution may be non-null within this range. In this case, considering that scattering efficiency grows approximately, i.e. in the limit of small particles, with the sixth power of the nanoparticle's diameter, the polydisperse distribution behaves approximately as a monodisperse distribution with a representative diameter D′eff defined as:

D′eff may by selected so as to lie within the range [5 nm-350 nm], preferably [10 nm-250 nm], more preferably [40 nm-180 nm], still more preferably [60 nm-150 nm].

In some embodiments, the natural quality of lighting improves whenever the maximum luminance of the light source is greater than 0.1*106cd/m2, for example at least 1*106cd/m2, or at least 5*106cd/m2or more. For those values, as a matter of fact, the light source generates enough glare for the source itself to be difficult to look at, thereby preventing the observer from evaluating the source's distance by means of the mechanism of eye focusing. Those luminance values contribute to obtain an infinite breakthrough effect. Moreover, glare makes it difficult to detect possible non-uniformities in the luminance profile of the light source, thus making it difficult to detect differences between the image of the light source and an image of the real sun.

In some embodiments, the exit aperture of the light source approximates a circle, the image of the light source perceived by the observer is still circularly shaped because the optical system does not twist the image. In some embodiments, the luminous layer has an elliptic shape illuminated, for example, by a light beam having circular divergence. However, other shapes are also possible, e.g. an elongated shape.

Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.