Patent Description:
As used herein, a light mixing chamber is intended to mean a chamber, cavity, tube, box or the like which is adapted to or capable of mixing light originating from one or more light sources and travelling through it to form an output being a mixture of the light from the one or more light sources.

There is a rapidly increasing interest in dynamic LED lighting systems in which the beam changes its shape depending on the needs of the user. The beam can be controlled by a smartphone or a remote control. Current examples of beam control use a liquid crystal (LC) element to control the shape of a collimated LED beam. Other examples have a small built-in motor to control the movement of optical components within a luminaire. Dynamic beams are also possible by using pixelated LED sources. These configurations work very well, but require multiple optical components (such as collector lenses, multiple plano-convex lenses and diffuser films) to shape the final beam.

For instance, prior art document <CIT> disclose a device having a ball lens and an LED. The LED may be located in the focus of the ball lens, or within the focal distance. However, this device is an omnidirectional light source for decorative illumination, and not capable of projecting a well-defined image.

Also, all of the known concepts for remote adjustment of a light beam are either expensive or require a lot of effort to construct and maintain over a considerable lifetime (say more than <NUM> hours).

Therefore, there is a desire to provide a light emitting device of the type mentioned by way of introduction which has a simpler construction, which is cheap, which is easy to construct, and which requires little or no maintenance over its life time.

<CIT> discloses a lighting device having a light-guiding region that is delimited by (i) a light-redirection surface of a light-redirection element <NUM> and (ii) a light in-coupling surface portion of a sphere lens.

It is an object of the present invention to overcome this problem, and to provide a light emitting device adapted for projecting a beam onto a target surface, which light emitting device has a simpler construction, which is cheap, which is easy to construct, and which requires little or no maintenance over its life time.

According to a first aspect of the invention, this and other objects are achieved by means of a light emitting device adapted for projecting a beam onto a target surface, the light emitting device comprising a light engine comprising a light source, a light mixing chamber comprising a light exit window, an optical component having a spherical shape with a curved light-receiving surface, and a diffuser, the light source being arranged to, in operation, emit light towards the light exit window of the light mixing chamber, the light exit window of the light mixing chamber thereby acting as an extended light source with a curved light-emitting surface, wherein the diffuser is provided at the light exit window of the light mixing chamber, the optical component being provided adjacent to the diffuser, wherein the shape of the diffuser is conformal to the curved light-receiving surface of the optical component and coincident with a focal surface of the optical component, and wherein the light mixing chamber is divided into at least two compartments.

Thereby, a light emitting device is provided which makes it possible to provide an adjustable beam using a single optical component, namely the spherically shaped optical component, combined with a shaped, extended light source due to the provision of the at least one light mixing chamber. Such a light emitting device has a very simple construction, which necessitates few components and which is cheap to manufacture.

In particular, by providing that the curved light-receiving surface of the light mixing chamber is conformal to the curved light-receiving surface of the optical component, and further is coincident with a focal surface of the optical component, a light emitting device is provided which is particularly simple to construct and assemble, and which requires little or no maintenance over its life time. Such a light emitting device is capable of projecting a very well-defined image.

Furthermore, as will be clear from the below, because the extended light source can be divided in pixels or domains, pattern-wise (dynamic) lighting becomes possible. This approach has an enormous potential for retail/shop illumination, architectural lighting and outdoor lighting.

In an embodiment, the optical component is a spherical lens, a ball lens or a dielectric sphere.

Such an optical component is very useful for illumination purposes and provides for not only a particularly simple construction of the light emitting device, but also a particularly well-defined projected image.

In an embodiment, the light source comprises any one of at least one LED, an array of LEDs, an array of mini-LEDs and an array of micro-LEDs.

Such a light emitting device is particularly simple in construction. Furthermore, providing an array of LEDs, mini-LEDs or micro-LEDs provide for an especially uniform light output of the extended light source, and thus of the light beam exiting the light mixing chamber.

In an embodiment, each LED of the array of LEDs, mini-LEDs and/or micro-LEDs is individually controllable.

In addition to the above, this provides for enabling fine tuning of the light output of the extended light source, and thus of the light beam exiting the light mixing chamber.

In an embodiment, the light emitting device comprises two or more light engines.

Thereby a light emitting device is provided which has a greater versatility in terms of the variation in light outputs obtainable, and which may thus fulfill a greater range of user demands.

In an embodiment, the light exit window of the light mixing chamber is rectangular.

Thereby a light emitting device is provided which allows for providing more complex and customizable illumination patterns, especially if combined with employing more than one light source.

In an embodiment, the light mixing chamber comprises reflective walls.

Thereby a light emitting device is provided which loss of light in the light mixing chamber is minimized or avoided altogether, and with which the light output of the light mixing chamber is particularly uniform.

Inhe light emitting device according to the first aspect of the invention, a diffuser is provided at the light exit window of the light mixing chamber.

Thereby a light emitting device is provided with which the light delivered to the optical component is particularly uniform and is furthermore free from artefacts.

The shape of the diffuser is conformal to the shape of the optical component.

Thereby, a light emitting device is provided which is particularly simple to construct, and which requires little or no maintenance over its life time. Such a light emitting device is furthermore capable of projecting a particularly well-defined image.

The light mixing chamber is divided into at least two compartments.

Thereby a light emitting device is provided which has a greater versatility in terms of the possible illumination patterns obtainable, and which may thus fulfill a greater range of user demands.

In an embodiment, the at least two compartments of the light mixing chamber are separated by means of a diffusive or specular reflective wall.

Thereby, a light emitting device is provided which enables individual control of the light output of each compartment of the light mixing chamber, and which thus has a great versatility in terms of the variation in light outputs obtainable. Furthermore, by providing the separating wall as a reflective or specular wall, a light emitting device is provided which loss of light at the separating wall is minimized or avoided altogether, and with which the light output of the light mixing chamber is thus particularly uniform.

In an embodiment, the light mixing chamber comprises any one of mixing rods, tapered mixing rods, light guides, tapered light guides, a tapered hexagonal collimator and an array of square mixing rods.

Thereby a light emitting device is provided which has a particularly great versatility in terms of the possible illumination patterns obtainable, as in principle any illumination pattern may be obtained depending on the particular construction and distribution of the parts of the light mixing chamber.

Furthermore, by also collimating the light output of the light mixing chamber, the optical efficiency of the light emitting device is improved.

In an embodiment, the optical component is or comprises an array of lenses.

This embodiment is especially advantageous for spot modules, and provides for a further improved versatility in terms of the illumination patterns made possible.

In an embodiment, each lens of the array of lenses is associated with a light source.

Thereby a light emitting device is provided which has a reduced thickness, and which has a superior thermal performance.

The invention furthermore, in a second aspect, concerns a lamp, a luminaire, or a lighting fixture comprising a light emitting device according to the invention.

Such a lamp, a luminaire or a lighting fixture may be a lamp, a luminaire or a lighting fixture, for instance a spot module, for retail or shop illumination, for architectural lighting or for outdoor lighting purposes.

It is noted that throughout the drawing, cf. for instance <FIG>, E(x, y) denotes the illuminance on the plane of projection (for instance a floor or a wall) and, cf. for instance in <FIG>, I(θ, φ) denotes the far-field intensity profile obtained with the light emitting device.

<FIG> shows a cross-sectional side view of a light emitting device <NUM> according to a first embodiment of the invention.

Generally, and irrespective of the embodiment, the light emitting device <NUM> is of the type adapted for projecting a light beam <NUM> onto a target surface. The light emitting device <NUM> comprises at least one light engine <NUM>. The light engine <NUM> comprises one or more light sources <NUM>, at least one light mixing chamber <NUM> and an optical component <NUM>. The optical component <NUM> has a spherical shape.

Generally, and irrespective of the embodiment, when seen along the optical axis <NUM> of the light emitting device <NUM>, the at least one light mixing chamber <NUM> is arranged between the at least one light source <NUM> and the spherical optical component <NUM>.

The light emitting device may furthermore comprise a housing <NUM> with a front window <NUM>. The housing <NUM> may be a black absorbing housing or tube. The front window <NUM> is transparent and may for example be made of clear polycarbonate or textured PMMA, optionally provided with a diffusing component such as a diffuser film.

Generally, and irrespective of the embodiment, the at least one light source <NUM> comprises one or more LEDs. The LEDs may be adapted to emit light of any feasible color. In embodiments comprising two or more LEDs, the LEDs may be adapted to emit light of the same color temperature or of two or more different color temperatures. The at least one LED may also be a tunable LED.

Generally, and irrespective of the embodiment, the at least one light mixing chamber comprises a light exit surface or window <NUM>, a bottom surface <NUM> and a circumferential surface <NUM> extending between the light exit window <NUM> and the bottom surface <NUM>. The bottom surface <NUM> and the circumferential surface <NUM> are non-light emitting surfaces.

The light emitting device <NUM> of <FIG> comprises one light mixing chamber <NUM> and one light source <NUM>. The at least one light source <NUM> is arranged on the bottom surface <NUM> of the light mixing chamber.

Generally, and irrespective of the embodiment, the at least one light source <NUM> is arranged to, in operation, emit light in a direction generally towards the light exit window <NUM> of the light mixing chamber <NUM> such that the light exit window <NUM> of the light mixing chamber <NUM> thereby acts as an extended light source.

Generally, and irrespective of the embodiment, the optical component <NUM> is arranged adjacent to the light exit window <NUM> of the light mixing chamber <NUM>. The light exit window <NUM> of the light mixing chamber comprises a curved surface configured to being conformal to the curvature of the outer surface <NUM> of the optical component <NUM>. also <FIG> and <FIG> showing better the curvature of the light exit window <NUM>. Furthermore, the light exit window <NUM> is positioned such as to be coincident with the focal surface <NUM> of the optical component <NUM>.

The optical component <NUM> may, as illustrated schematically in <FIG>, be a dielectric sphere, a spherical lens or a ball lens. Such optical components are characterized by having a radius, R, and a refractive index, n. The optical component <NUM> further comprises a diameter d. <FIG> shows the focal point, F, of a parallel incoming beam. The focal point, F, is located on the focal plane <NUM>. The focal plane <NUM> is a spherical plane. Thus the focal length, f, fulfills the relation: <MAT>.

The focal plane (or focal surface) of a spherical lens is generally located close to the spherical lens surface. If, for instance, the refractive index, n, is <NUM>, the focal plane is located exactly on the surface of the ball lens. Such lenses are often used for fiber-fiber coupling.

Spherical lenses and ball lenses are very useful for illumination applications. Because the focal plane is quite close to the spherical lens surface, it is possible to project an image of an extended source on the floor or wall in an efficient way. A prerequisite is that the surface of the extended light source, and thus in the present invention of the light exit window <NUM> of the light mixing chamber <NUM>, follows the shape of the focal plane <NUM>.

<FIG> shows cross-sectional side view of a light emitting device <NUM> according to a second embodiment of the invention. <FIG> shows a bottom view of the light emitting device <NUM> according to <FIG> shows a perspective view of a light mixing chamber of the light emitting device <NUM> according to <FIG>. The light emitting device <NUM> differs from that of <FIG> described above in that the light mixing chamber <NUM> of the light emitting device <NUM> is provided with a square cross-sectional shape.

The reason for providing the light mixing chamber <NUM> of the light emitting device <NUM> with a square cross-sectional shape is to provide a square illuminated pattern. However, and as is illustrated on <FIG>, such a light mixing chamber <NUM> in fact provides a square light pattern with concave sides. <FIG> illustrates the intensity distribution of the pattern of <FIG>.

<FIG> shows cross-sectional side view of a light emitting device <NUM> according to a third embodiment of the invention. <FIG> shows a bottom view of the light emitting device <NUM> according to <FIG> shows a perspective view of a light mixing chamber <NUM> of the light emitting device <NUM> according to <FIG>. The light emitting device <NUM> differs from those of <FIG> described above in that the light mixing chamber <NUM> of the light emitting device <NUM> is provided with a square cross-sectional shape with concave sides. The concave sides are provided since to obtain a perfect square illumination pattern, the shape of the light exit window <NUM> should be adapted in comparison with that shown in <FIG>. The circumferential shape of the light exit window <NUM> of the light mixing chamber <NUM> could be defined by the following parametric equations: <MAT> <MAT>.

In equations <NUM> and <NUM>, t is the parameter in the parametric representation (x(t), y(t)) describing the circumference of the mixing chamber, a is a scaling factor and m is a factor determining the shape. By way of example, in equations <NUM> and <NUM>, a is equal to <NUM> millimeters and m is equal to <NUM>. In the embodiment shown, R is equal to <NUM> millimeters, n is equal to <NUM>, f is equal to <NUM> millimeters and d is equal to <NUM> millimeters. The resulting illuminance on the plane of projection (for instance a floor or a wall) is shown in <FIG> featuring a perfect square pattern, and the far-field intensity profile obtained with the light emitting device <NUM> is illustrated in <FIG>. In the examples illustrated in <FIG> and <FIG>, respectively, the distance between the light exit window <NUM> and the projection is <NUM> millimeters.

In the embodiments above, a perfectly uniform extended source is assumed, i.e. the luminous emittance (<NUM>/m<NUM>) of the extended light source is constant over the whole light emitting area. To tune illuminance of the projection (for example to produce a perfect uniform illuminated square), the luminous emittance of the extended light source may be adapted.

Another aspect is the quality or uniformity of the extended light source. This aspect may be taken into account by providing the light source <NUM> as a dense array of mini-LEDs or micro-LEDs. The size of a typical mini-LED is <NUM>-<NUM> micrometers. Micro-LEDs are much smaller, say <NUM>-<NUM> micrometers. These LEDs form an almost continuous luminous surface. In the projected image, the individual LEDs are barely visible. In this particular case, the micro LEDs form an almost continuous light emitting area. However, there are still small slits or gaps between the LEDs which may be visible when perfectly imaged. To avoid imaging of these slits or gaps, and thus to fine-tune the uniformity of the projected light pattern, the full collection of micro-LEDs can be placed slightly (say +/- <NUM> millimeters) out of focus, i.e. placed a bit in front or behind the focal plane. To fine-tune the uniformity of the projected light pattern, the sources can be placed slightly out of focus (for example in front or behind the focal plane).

Turning now to <FIG>, a cross-sectional side view of a light emitting device <NUM> according to a fourth embodiment of the invention is shown. <FIG> shows a cross-sectional side view of the light emitting device <NUM> according to <FIG> seen from another angle of view, and <FIG> shows a bottom view of the light emitting device <NUM> according to <FIG>. The light emitting device <NUM> differs from those described above in that two light sources <NUM> and <NUM> and two light mixing chambers <NUM> and <NUM>' are provided (cf. The two light sources <NUM>, <NUM> are arranged on the mutually adjacently arranged rectangular light mixing chambers <NUM>, <NUM>'. The light exit windows <NUM> of the two light exit chambers <NUM>, <NUM>' comprise such a curvature as to conform to the curvature of the surface <NUM> of the optical component <NUM>. In the example shown, this setup is combined with a spherical lens <NUM> with R being equal to <NUM> millimeters, n being equal to <NUM>, f being equal to <NUM> millimeters and d being equal to <NUM> millimeters). The two adjacently arranged light sources <NUM> and <NUM>, and thus also the two rectangular light exit windows <NUM> of the light mixing chambers <NUM>, <NUM>', emit light with different color temperatures, such as for instance <NUM> and <NUM>.

The two rectangular light exit windows <NUM> of the light mixing chambers <NUM>, <NUM>'create three possible illumination configurations as illustrated in <FIG> (both light sources <NUM>, <NUM> on), <FIG> (only light source <NUM> on) and <FIG> (only light source <NUM> on). The distance from light emitting device to projection plane is <NUM> millimeters. This embodiment allows much more complex and customizable illumination patterns.

<FIG> shows cross-sectional side view of a light emitting device <NUM> according to a fifth embodiment of the invention. <FIG> shows a perspective view of the light mixing chamber <NUM> of the light emitting device <NUM> according to <FIG>. The light emitting device <NUM> differs from those described above in that the light mixing chamber <NUM> is provided with two compartments <NUM> and <NUM> separated by an optical separation sheet or wall <NUM>. Embodiments with more than two such compartments are also feasible. More complex and flexible systems can thus be designed using a freeform mixing chamber consisting of a large number of compartments which can be individually controlled. The light sources <NUM> are placed on a flat surface <NUM> of the light mixing chamber <NUM>. The light mixing chamber <NUM> may especially in this embodiment be a light mixing box. The light mixing chamber <NUM> furthermore comprises a highly reflective, and optionally also diffuse, wall <NUM>. A diffuser <NUM> (<FIG>) is placed at the light exit window <NUM> of the light mixing chamber <NUM>. The diffuser <NUM> is shaped to follow the shape of the focal surface of the spherical optical component <NUM>. The advantage of such a light mixing chamber <NUM> is that the spherical optical component <NUM> receives uniform light without any artifacts from the individual light sources <NUM>.

The luminous emittance (lm/m<NUM>) of the extended light source, i.e. the light exit window <NUM> of the light mixing chamber <NUM>, can be tuned by changing the height, h, of the light mixing chamber <NUM> and/or the arrangement of the light sources <NUM> on the flat bottom surface <NUM>. This in principle applies to all embodiments disclosed herein.

Also, the diffuser <NUM> can have different diffusive properties depending on the corresponding position on the light exit window <NUM> of the light mixing chamber <NUM>. For instance, when a volume diffuser is used, the thickness of the diffuser <NUM> may vary over the light exit window <NUM>. In the example of <FIG>, the height, h, of the mixing chamber is <NUM> millimeters and the diameter, dm, is <NUM> millimeters. For the spherical optical component, R is equal to <NUM> millimeters, n is equal to <NUM> and d is equal to <NUM> millimeters. There are provided <NUM> light sources <NUM>, each of <NUM> millimeter by <NUM> millimeter in size. These light sources <NUM> are placed on a circle with a radius of <NUM> millimeters on the bottom <NUM> of the light mixing chamber <NUM>. The light sources <NUM> are LEDs with a Lambertian emission profile.

<FIG> illustrates the beam shape (far field intensity profile) obtained when the light sources in both compartments <NUM> and <NUM> of the light mixing chamber <NUM> of the light emitting device <NUM> of <FIG> are on, and <FIG> when only the light sources in one compartment are on. The illuminance on the projection area is also indicated in <FIG> and <FIG>. The projection area is <NUM> millimeters by <NUM> millimeters, and the distance to the projection area is <NUM> millimeters.

It is noted that the separation between the compartments can be hard or soft. <FIG> show a hard separation between the compartments. The transition can be made more soft or gradual by using a separation sheet or wall of a lower height, i.e. not touching the shaped diffuser over the whole length.

<FIG> shows a perspective view of a light emitting device <NUM> according to a sixth embodiment of the invention. The light emitting device <NUM> differs from those described above in that the light mixing chamber is provided with a tapered configuration. More particularly, the light mixing chamber <NUM> is a tapered, hexagonal collimator used to mix and collimate the light from two LED light sources <NUM>, <NUM> with a mutually different color temperature, for example <NUM> and <NUM>. The advantage of collimating the light (in addition to mixing the colors of the two different LED light sources) is that a higher optical efficiency and the formation of a more well-defined (sharp) image is obtained.

<FIG> shows a perspective view of a light emitting device <NUM> according to a seventh embodiment of the invention. <FIG> shows a cross-sectional side view of the light emitting device <NUM> according to <FIG>. The light emitting device <NUM> differs from those described above in that the light mixing chamber <NUM> comprises an array of mixing rods <NUM>, <NUM>' with square cross-sectional shape. In the example shown, an array of <NUM> by <NUM> - or a total of <NUM> - mixing rods <NUM>, <NUM>' are provided. Different array sizes are also feasible. The <NUM> thus formed light exit windows <NUM> are shaped such as to in combination conform to the shape of the focal surface of the spherical optical component <NUM>. Each mixing rod <NUM>, <NUM>' is associated with one or more LED light sources <NUM>. Each LED light source <NUM> or LED light source cluster is adapted to be individually controlled, i.e. turned on or off or even dimmed. By means of such a light emitting device <NUM>, complex light patterns can be produced as is illustrated in <FIG> and <FIG>. <FIG> shows the result of all light sources <NUM> being turned on, while <FIG> show the result of some light sources <NUM> being turned on and other turned off.

<FIG> shows cross-sectional side view of a light emitting device <NUM> according to an eighth embodiment of the invention. The light emitting device <NUM> differs from those described above, and in particular the one described in relation to <FIG>, in that an array of spherical optical components <NUM> are provided, each associated with a light mixing chamber <NUM> and one or more light sources. The light sources are not shown on <FIG> for the sake of simplicity. In other words, the light emitting device <NUM> comprises a plurality of light engines <NUM>, particularly as shown by way of a non-limiting example five light engines <NUM>.

Claim 1:
A light emitting device (<NUM>) adapted for projecting a light beam (<NUM>) onto a target surface, the light emitting device (<NUM>) comprising:
a light engine (<NUM>) comprising a light source (<NUM>),
a light mixing chamber (<NUM>) comprising a light exit window (<NUM>),
an optical component (<NUM>) having a spherical shape with a curved light-receiving surface (<NUM>), and
a diffuser (<NUM>),
wherein the light source (<NUM>) is arranged to, in operation, emit light towards the light exit window (<NUM>) of the light mixing chamber, the light exit window (<NUM>) of the light mixing chamber (<NUM>) thereby acting as an extended light source with a curved light-emitting surface,
wherein the diffuser (<NUM>) is provided at the light exit window (<NUM>) of the light mixing chamber (<NUM>),
wherein the optical component (<NUM>) is provided adjacent to the diffuser (<NUM>), and
wherein the shape of the diffuser (<NUM>) is conformal to the curved light-receiving surface (<NUM>) of the optical component (<NUM>) and coincident with a focal surface (<NUM>) of the optical component (<NUM>),
characterized in that the light mixing chamber (<NUM>) is divided into at least two compartments (<NUM>, <NUM>).