ZOOM SPOTLIGHT

Description

[0001] The present invention relates to a zoom spotlight with variable beam angle, comprising at least one light source, a focusing optics for emitting a beam of rays and a zoom element for adjusting the beam angle of the beam of rays emitted by the focusing optics.

[0002] Zoom spotlights are typically used to flexibly accentuate objects of varying sizes or spatial areas at different distances. Possible applications for such zoom spotlights range from stage lighting in theaters or variety shows to the illumination of paintings, sculptures, and objects in museums to product lighting in retail, where, for example, pop-up shops with varying product ranges and presentation layouts require variable illumination, but can also include general lighting applications.

[0003] The adjustable zoom optics allow the beam or widening angle of the light emitted by the zoom spotlight to be changed, thus allowing the light output to be flexibly adapted to the object to be illuminated or the corresponding area of ​​the room.

[0004] In their simplest design, such zoom spotlights only feature lens systems associated with the light source, for example, in the form of an aspherical lens that can be moved in front of the light source. However, such pure lens systems typically only achieve low optical efficiencies, not exceeding 40%, since the light source radiation largely passes laterally past the lens for the narrow beam range.

[0005] To avoid this lateral light loss, zoom spotlights are already known. Their optical system uses reflector-lens combinations. A reflector captures and focuses the light emitted by the light source. The desired zoom effect can be achieved by adjusting a lens positioned in front of the reflector.

[0006] A zoom spotlight of this type is shown, for example, in document DE 20 2014 000 449 U1, which intends to use a so-called COB LED as the light source, the light of which is captured by a reflector in the more expanded area, with a convex lens in front of the reflector being axially adjustable in order to achieve an adjustable zoom effect.

[0007] Such zoom spotlights with adjustable reflector-lens systems are more efficient than pure lens systems, but still have relatively limited efficiencies, at least when a larger zoom range is to be achieved by a larger lens adjustment range, since in this case, a portion of the light is typically emitted past the lens in the more distant adjustment positions. Furthermore, the homogeneity of the light emitted by the zoom spotlight is unsatisfactory. Due to the axial adjustment of the lens in front of the reflector, depending on the position of the lens, more or less significant inhomogeneities arise in the radiation area of ​​the zoom spotlight, which manifest themselves in uneven brightness of the irradiated object or spatial region.

[0008] From WO 99 / 06758 A2 a spotlight is known in which a color or scattering filter in the form of a glass plate can be inserted between the light source and the Fresnel lens in order to be able to adjust the color of the light emitted by the spotlight in the desired manner.

[0009] Furthermore, WO 2014 / 031644 A1 describes a stage spotlight in which a color filter, a pinhole, and so-called gobo elements are arranged one after the other in the light source, which is enclosed by a reflector. Lengthwise adjustable diffuser elements and a lengthwise adjustable zoom lens are then arranged in the further beam path.

[0010] Further radiators with plate-shaped diffuser elements are known from the documents US 2013 / 058094 A1, EP 37 42 047 A1 and WO 2017 / 173429 A1.

[0011] In order to generate homogeneous light distributions with high efficiency even with larger zoom ranges, it can be provided that the light beam coming from the light source is divergingly or specifically diverged before it hits the bundling optics, and that the diverging plane is adjustable in terms of its distance from the bundling optics in order to implement the zoom function. In this case, a diverging and / or expanding element provided with a light-diffusing and / or specifically diverging diverging and / or expanding structure can be used as the zoom element. This diverging and / or expanding element is provided between the bundling optics and the light source, wherein the said thin-walled diverging and / or expanding element and / or the bundling optics is / are mounted so as to be movable back and forth for zooming the beam of the emitter.

[0012] A diffusely scattering expansion in front of the focusing optics makes the zoom mechanism insensitive to alignment and positioning inaccuracies. However, targeted dispersion or expansion can also be provided, for example, with an expansion angle of 2 x 20° to 2 x 60° or 2 x 20° to 2 x 50°. Depending on the selected dispersion or expansion, the zoom effect can be flexibly adjusted, for example, an elliptical, oval, or even circular zoom. Regardless of this, the focusing optics are advantageously fully exposed to the beam angle in every zoom position, so that the lowest possible luminance can be achieved for a given intensity at a point in the irradiated field. Since the full cross-sectional area of ​​the focusing optics is always "visible," the light comes from the maximum possible area, so that the luminance is as low as possible for a given intensity.

[0013] Based on this, the present invention seeks to create an improved zoom spotlight of the type mentioned above that avoids the disadvantages of the prior art and advantageously develops them further. In particular, the aim is to achieve optically insensitive beam angle adjustment and flexible adjustment of the zoom type of the zoom spotlight while maintaining high system efficiency.

[0014] According to the invention, the stated object is achieved by a zoom spotlight according to claim 1 or 2. Preferred embodiments of the invention are the subject of the dependent claims.

[0015] In order not only to be able to adjust the beam angle but also to be able to adapt the type of zoom in a simple manner, according to the invention an interchangeable holder is provided for exchanging the thin-walled scattering and / or expanding element and for inserting differently designed scattering and / or expanding elements for generating beams of different contours and / or colors, wherein the said interchangeable holder can have detachable fastening means in order to be able to be easily detached from a radiator housing or a component carrier of the radiator and / or to be able to easily detach the thin-walled scattering and / or expanding element from the interchangeable holder.

[0016] In particular, the differently designed scattering and / or expanding elements can be configured to produce differently contoured beams, while simultaneously having a corresponding mounting contour for releasably attaching them to the same mounting contour of the same interchangeable holder. Although, for example, one of the different expanding or scattering elements produces a circular beam and another of the expanding or scattering elements produces an elliptical or angular beam, both or all of the expanding or scattering elements can have the same mounting contour or outline and thus be used in the same interchangeable holder.

[0017] The interchangeable holder is advantageously longitudinally displaceable substantially parallel to the main beam direction and can optionally also be mounted transversely displaceably transversely to the main beam direction, wherein preferably a screw sleeve for longitudinally displaceable mounting or a cross-slide guide for longitudinally and transversely displaceable mounting of the interchangeable holder can be provided in order to adjust the zoom angle and / or the zoom type and / or the color, as will be explained below.

[0018] The interchangeable holder has an annular film holder for the positive and / or non-positive holding of the thin-walled spreading and / or expanding element, which film holder is detachably attached to an adjustably mounted holder sleeve in order to enable easy changing of the spreading or expanding element.

[0019] In this case, a radiator housing can comprise a detachable or openable cover for closing a replacement opening through which the scattering and / or expanding element and / or a support element of the replacement holder, or even the entire replacement holder, can be removed and inserted. Preferably, an optics holder, on which the focusing optics is held, can be removed from the front of the radiator housing together with the focusing optics and can be removed from the radiator housing to expose the replacement opening located on the front. The focusing optics holder can thus form the removable housing cover.

[0020] Preferably, the interchangeable holder has fastening means that can be released manually, in particular without tools or by standard tools such as a screwdriver, for fastening a spreading and / or expanding element that is used in each case.

[0021] When using a scattering film, the detachable fastening means of the interchangeable holder can, for example, comprise edge-side clamping elements by means of which the scattering film can be clamped at the edge or a frame support to which the film is attached can be clamped.

[0022] Advantageously, a radiator housing can comprise a detachable and / or openable cover for closing a replacement opening through which the said replacement holder is accessible and the respective scattering and / or expanding element can be removed in order to be replaced by another scattering and / or expanding element.

[0023] In particular, in a further development of the invention, a set of differently designed interchangeable scattering and / or expanding elements can be provided, which are differently scattering and / or differently expanding, so that different scattering and / or expanding elements form different beam bundles, wherein the different interchangeable scattering and / or expanding elements advantageously simultaneously have a mutually corresponding fastening contour for fastening to the interchangeable holder or an interchangeable holder counterpart.

[0024] In particular, diffusion films with different diffusion layers can be used or exchanged for each other in order to set the desired zoom type.

[0025] Depending on which scattering and / or expanding element is used between the light source and the focusing optics, the beam emitted by the focusing optics has different contours and / or shapes. For example, if a scattering and / or expanding element that scatters evenly in different directions and produces a beam with a circular cross-section, for example, is replaced by a scattering and / or expanding element whose scattering and / or expanding structure is directional or which has a greater expansion in a first main direction than in a second, perpendicular main direction, an elliptical or approximately even somewhat rectangular beam can be emitted by the focusing optics instead of the beam with a circular cross-section previously emitted by the focusing optics.

[0026] In a further development of the invention, different colored scattering and / or expanding elements or scattering and / or expanding elements with different colored sections can also be used, wherein different colored scattering and / or expanding elements or differently colored sections can be easily exchanged for one another.

[0027] In particular, a scattering and / or expanding element can be used that has differently colored sections, so that the light beam coming from the light source partially hits, for example, a red section of the scattering and / or expanding element and another part of the light beam hits, for example, a green section of the scattering and / or expanding element. Due to the expanding, light-scattering design of the diffuser, light mixing occurs on the emission side of the scattering and / or expanding element, even before the bundling optics and / or after the bundling optics, so that in the above example with red and green sections of the scattering and / or expanding element, overall yellow light or yellowish mixed light is achieved.

[0028] Such a sectionally different color of the diffusion and / or expansion element can provide mixed light with very high photometric efficiency in terms of color, since, despite the mixture of two colors, only one film or one diffusion and / or expansion element needs to be irradiated. If the light is mixed in the conventional way and colored successively, for example, first by a red film and then by a green film arranged one behind the other, noticeably higher photometric losses occur.

[0029] At the same time, the color temperature of the generated mixed light can be very easily changed or variably adjusted using a diffusing and / or expanding element with differently colored sections. In particular, the diffusing and / or expanding element with the differently colored sections can be mounted so that it can be moved or adjusted transversely to the main beam direction of the light beam passing through the diffusing and / or expanding elements, in order to increase or decrease the respective irradiated surface portions, thus achieving a corresponding change in the mixed color.

[0030] For example, if a scattering and / or expanding element is used that has a red half and a green half, yellow light can be mixed by positioning the scattering and / or expanding element approximately centrally to the beam bundle, so that approximately 50% of the light beam flowing towards the bundling optics passes through the red half and approximately 50% through the green half of the scattering and / or expanding element. If the scattering and / or expanding element is moved transversely to the main beam direction, so that the beam bundle passes, for example, completely through the red half of the scattering and / or expanding element, red light can be generated. Conversely, green light can be generated if the scattering and / or expanding element is moved in a different direction so that the light only passes through the green half.

[0031] Advantageously, the scattering and / or expanding element can be moved gradually or continuously transversely to the main beam direction, so that mixed forms can also be adjusted gradually or continuously, for example in such a way that it can be changed from 40% red light and 60% green light to, for example, 70% red light and 30% green light in order to adjust the color of the generated mixed light more from greenish-yellow to more reddish-yellow or orange.

[0032] However, the light color can also be adjusted in other ways, for example, by inserting or moving a separate color film or other light-coloring optical element. For example, in addition to the scattering and / or expanding film, a color film with a smooth surface can be moved into the beam to be colored.

[0033] Alternatively or additionally, wave-optically active structures can be used, which can, for example, adjust the desired light color through extinction. For example, a color-changing scattering structure can be provided on a scattering element, which adjusts the desired color through wave-optical extinction. This can improve efficiency and, if necessary, reduce the thickness of the film or element.

[0034] The expanding or scattering structure of the scattering and / or expanding element can, if necessary, be combined with such a color-changing scattering structure in order to achieve both effects, i.e. the zoom effect and the color-changing effect, simultaneously.

[0035] The aforementioned transverse adjustability of the zoom element does not necessarily have to be used for color change, but can also be used in other ways. For example, a scattering and / or expanding element with differently structured sections can be used, so that differently structured sections can be moved into the irradiated area by transverse displacement. For example, this allows a diffusely scattering section and a specifically expanding section to be moved into the beam bundle, respectively, to achieve different zoom effects.

[0036] In order to be able to combine the aforementioned transverse adjustability with the zoom adjustability in a simple manner, a cross-slide guide can be provided, for example, on which the scattering and / or expanding element holder is mounted, for example in the form of the aforementioned interchangeable holder. Such a cross-slide guide can, for example, comprise a main slide that is mounted or guided for displacement parallel to the main beam direction of the beam that passes through the scattering and / or expanding element and / or radiates towards the bundling optics. An auxiliary slide can be mounted or guided on this main slide so that it can be displaced transversely to the aforementioned main beam direction in order to also be able to displace the scattering and / or expanding element transversely to the main beam direction.

[0037] If the main carriage is moved toward or away from the focusing optics, the zoom function is activated, and the beam angle of the beam emitted by the focusing optics is changed and adjusted. On the other hand, if the auxiliary carriage is moved or adjusted perpendicular to the main beam direction, the light temperature or color can be adjusted and changed.

[0038] Alternatively or additionally, the at least one scattering and / or expanding element and / or the at least one color-changing optical element can also be mounted in a rotationally adjustable manner in order to move differently designed sections of the respective element into or out of the beam bundle, for example in the manner of a revolver magazine.

[0039] The thin-walled scattering and / or expanding element can, in particular, be designed as a film or scattering and / or expanding film. Such scattering and / or expanding films are known per se, but have not been used as zoom elements in front of the focusing optics until now. Instead, they have typically been used on the emission side of the focusing optics of a spotlight, as a kind of soft-focus element, to shape the emitted light cone and create a softer light, which is often used in museum spotlights, for example. The scattering films were mounted statically, i.e., at a fixed distance from the focusing optics, since downstream scattering films, i.e., mounted behind the focusing optics, cannot produce a zoom effect even if they are shifted.

[0040] Such a scattering or expanding film can be flexible or pliable as is typical for films and can be very thin, for example having a thickness of less than 3 mm or less than 1 mm, whereby the thickness can also be only fractions of a millimeter.

[0041] In principle, however, it would also be possible to use a somewhat thicker, yet still thin-walled diffuser disc with a thickness in the range of a few millimeters, for example, 3, 4, or 5 mm, as the expanding scattering and / or expansion element. Such a diffuser disc can advantageously be plate-shaped, of consistent thickness, and / or flat. An at least approximately flat and / or plate-shaped design is possible regardless of the thickness and especially when using a scattering foil.

[0042] The scattering and / or expanding structure of the thin-walled scattering and / or expanding element can comprise a surface structure, wherein such a surface structure can comprise roughenings and / or a relief-like structuring, for example in the form of a matte surface. The scattering and / or expanding structure can also be designed so small, at least in some regions, that wave-optical effects, for example diffraction effects, can be achieved. Alternatively or additionally, the surface structure can also comprise directional structures such as grooves and / or facets, by means of which directional scattering of the light beam can also be achieved. If directional grooves or microfacets are used, for example, an expansion in one direction can be greater than in another, so that, for example, elliptical or approximately rectangular zoom beams can be achieved.

[0043] Alternatively or in addition to a surface structuring, the scattering and / or expanding structure can also comprise a particle structure embedded inside the thin-walled scattering and / or expanding element. In particular, very small, light-scattering particles can be embedded in the scattering film in an at least approximately uniformly distributed manner in order to effect the expanding effect inside the scattering film. The light-scattering, embedded particles have a diameter or thickness that is even smaller than the thickness of the film, so that the film surface can be formed by the plastic or material in which the particles are embedded. Accordingly, the film surface can be smooth. In principle, however, it would also be possible to combine a surface structuring with a light-scattering, embedded particle layer, for example if a scattering screen is used that is somewhat thicker than a scattering film.

[0044] In a further development of the invention, the aforementioned scattering and / or expansion structure can form a micro- or nanostructure whose individual structural elements have a size in the micro- or nano-range. For example, if relief-like roughenings or embedded particles are provided, the relief peaks or valleys or the aforementioned particles can have an extension of, for example, < 1 mm or < 1 µm.

[0045] Independently of this, the thin-walled scattering and / or expanding element can also be provided with a directed, cloud-like relief structure, for example, to achieve targeted expansions in the range of 2 x 20° to 2 x 60° or 2 x 20° to 2 x 40°. Such targeted expansion can, for example, create zoom effects of varying intensity in different directions, for example, to create an elliptical zoom effect.

[0046] Mixed forms with different scattering or expanding structures can also be provided in different sections of the film or thin-walled element. For example, a more strongly scattering structure can be provided in an inner or central section, and a less strongly scattering structure can be provided in an outer edge section of the element. Alternatively or additionally, directed expanding sections and diffusely scattering sections can also be provided on one element, for example, a central section of the zoom element can be provided with a specifically expanding structure and an edge section with a diffusely scattering structure.

[0047] Independently of this, gradual gradations or continuously changing scattering or expanding structures can also be provided, for example, such that the expanding effect of the structure decreases gradually or continuously toward the edge of the zoom element. Other gradients or section divisions are possible and should preferably be adapted to the respective zoom task.

[0048] In a further development of the invention, two or generally more scattering and / or expanding elements, in particular foils, can also be provided, which are arranged between the light source and the bundling optics and are preferably successively irradiated by the beam bundle to be formed and expanded.

[0049] Advantageously, such multiple scattering and / or expanding elements can be adjusted independently of one another relative to the focusing optics and / or relative to the light source, in particular, they can be moved back and forth between the light source and the focusing optics. For example, by changing the distance between the multiple scattering and / or expanding elements, different zoom effects can be achieved. For example, by adjusting the distance between two scattering and / or expanding elements with elliptical scattering structures, a rectangle with different aspect ratios can be generated when viewing the cross-section of the zoomed beam, or other beam cross-sections can be generated.

[0050] Advantageously, the plurality of scattering and / or expanding elements can also be adjusted together relative to the downstream bundling optics and / or relative to the light source, in particular moved back and forth.

[0051] In a further development of the invention, rotational adjustability of the at least one scattering and / or expanding element can also be provided. This allows, for example, the position of the main axes to be rotated in the case of an elliptical scattering structure. Advantageously, rotational adjustability can also be provided for multiple scattering and / or expanding elements, in particular to rotate the scattering and / or expanding elements relative to one another in order to adjust the shape of the zoomed beam as desired. Alternatively or additionally, a common rotational adjustment can also be provided.

[0052] In particular, the rotary adjustment axis can be aligned perpendicular to the scattering and / or expanding element and / or parallel to the main axis of the light beam coming from the light source.

[0053] Alternatively or in addition to adjusting the at least one scattering and / or expanding element, the downstream focusing optics can also be adjusted, for example, to position the focusing optics closer to or further away from the scattering and / or expanding element. For example, the focusing optics can be displaceably mounted in the direction of the beam coming from the at least one scattering and / or expanding element. This also allows the beam emitted by the focusing optics to be zoomed.

[0054] The said bundling optics can be designed in one or more parts and comprise one or more optical elements, wherein in the case of a multi-part design one or more optical elements can be adjustable in the manner mentioned, in particular can be displaceably mounted.

[0055] In a further development of the invention, the focusing optics can comprise a lens that can be spherically or aspherically curved to focus the light coming from the scattering and / or expanding element. Said lens can also be designed as a freeform surface lens to shape the emitted beam in the desired manner.

[0056] Alternatively or additionally, the bundling optics can also include a Fresnel lens, for example to minimize horizontal expansion.

[0057] Alternatively or in addition to such a lens, the bundling optics can also comprise a reflector which receives and radiates the expanded beam coming from the scattering and / or expanding element and thereby bundles it.

[0058] The light source arranged upstream of the scattering and / or expanding element can in principle be designed in different ways, whereby the term light source is to be understood broadly in the context of the present application, since the light beam directed onto the scattering and / or expanding element can also be emitted by an upstream optic, which then forms the "light source".

[0059] For example, a light mixing rod and / or a concentrator optic can be installed in front of the diffuser.

[0060] Such a mixing rod, positioned upstream of the scattering and / or expanding element, can fundamentally have a variety of designs, for example, a smooth or harmoniously curved peripheral surface. Alternatively, the mixing rod can also be provided with a profile on its outer surface running in the longitudinal direction of the rod, which can include longitudinal grooves and / or longitudinal ribs. Such a profile can be consistent over the length of the rod or can become weaker or tapered towards the light exit end of the light mixing rod.

[0061] In an advantageous further development of the invention, the profiling, viewed in the bar cross-section, can comprise alternating longitudinal grooves and longitudinal ribs of approximately equal width, so that peaks and valleys of the profiling have approximately the same width.

[0062] Irrespective of this, the longitudinal grooves and longitudinal ribs can have a rounded contour when viewed in the rod cross-section, so that the profiling, viewed in the rod cross-section, has an overall wave contour that can wrap around the circumference of the light mixing rod in the manner of a rounded flanging.

[0063] Alternatively, angular profile grooves or ribs could also be incorporated in the cross-section, so that the profile can also have a crenellated, angular contour when viewed in the bar's cross-section. For example, U-shaped profile ribs and / or grooves with angular or rounded corners can be provided at the leg transitions when viewed in cross-section, or triangular ribs or grooves can be formed.

[0064] In a further development of the invention, the longitudinal grooves and / or longitudinal ribs have a straight course parallel to the longitudinal direction of the rod.

[0065] In order to achieve sufficient light mixing, it may be sufficient if the aforementioned profiling extends from the light entry side over approximately 1 / 3 to 2 / 3 of the rod length, so that at least the last third of the light mixing rod towards its light exit end can remain unprofiled and have a smooth lateral surface.

[0066] The said elongated light mixing rod can be slim overall and have a length that is a multiple of the rod diameter, for example more than three times or more than five times the rod diameter.

[0067] Distributed around the circumference of the light mixing rod, for example, there can be 5 to 40, 10 to 30, or 12 to 20 longitudinal grooves and / or longitudinal ribs. The longitudinal grooves and / or longitudinal ribs can be distributed differently around the circumference, so that, for example, more longitudinal ribs and / or longitudinal grooves are provided in one circumferential sector than in another. For example, different numbers of ribs and / or grooves can be provided on different circumferential sides, particularly if the light mixing rod has an overall angular contour.

[0068] Alternatively or additionally, the longitudinal ribs and / or longitudinal grooves distributed over the circumference can have different widths and / or heights or depths. For example, deeper and / or wider longitudinal grooves and / or higher and / or wider longitudinal ribs can be provided in one circumferential sector or on one circumferential side, while flatter and / or narrower longitudinal grooves and / or lower and / or narrower longitudinal ribs can be provided in another circumferential sector and / or on another circumferential side.

[0069] The profile depth can vary over the length of the light mixing rod between 1 / 5 of the rod diameter and 0 or 1 / 10 of the rod diameter and 0 or 1 / 20 of the rod diameter and 0. In other words, the maximum profile depth can be between 1 / 5 and 1 / 20 of the rod diameter or 1 / 7 and 1 / 15 of the rod diameter, whereby for non-circular rod cross-sections the rod diameter can be regarded as the maximum transverse extent of the cross-sectional area.

[0070] The light mixing rod can have a cross-sectional contour that deviates from a circular shape, even if the profiling is ignored and the enveloping surface of the rod's lateral surface is considered. In particular, the enveloping surface of the light mixing rod can have a polygonal, for example, quadrangular or square, cross-sectional contour, whereby the enveloping surface cross-section can remain constant over the length of the mixing rod. For example, the enveloping surface can have a cylindrical shape that deviates from a circular cylinder, for example, in the manner of a polygonal extruded profile.

[0071] To avoid efficiency losses at the transition from the light mixing rod to the focusing optical element, the light exit surface of the light mixing rod can be designed to be congruent with the light entry surface of the focusing optical element. This allows the light to be directed across the entire rod cross-section into the full entry cross-section of the focusing optical element.

[0072] According to a further aspect, the aforementioned condensing optical element can be attached directly to the mixing rod. The direct, gap-free, flat connection between the light entry surface of the optical element and the light exit surface of the light mixing rod eliminates the loss of Fresnel reflection at an optical transition, allowing the mixing optics to operate more efficiently than a front-mounted optic.

[0073] Such an optically tight connection or optically tight assembly can be achieved, for example, by forming the condensing optical element integrally with the light mixing rod in a homogeneous, single-piece material, for example, by molding it from glass, transparent plastic, or silicone. However, an optically tight connection can also be achieved by bonding the light exit surface of the light mixing rod to the light entry surface of the optical element, preferably over the entire surface, using an optically transparent adhesive.

[0074] The said light mixing rod can be designed as a solid material rod, wherein a reflective coating can optionally be applied to the outer surface of the mixing rod consisting of transparent solid material, so that the light rays coupled into the light mixing rod can be totally reflected or reflected on the outer surface of the mixing rod.

[0075] However, the light mixing rod does not have to be a solid rod, but can also be a hollow rod, the inner surface of which can be reflective and provided with the aforementioned longitudinal ribs and / or grooves.

[0076] The said optical element, which is arranged downstream of the light mixing rod and is in particular a concentrating optical element, can in particular be a CPC or CPC-type element which transforms the light coming from the light mixing rod into a beam of rays, in the radiation area of ​​which every point is exposed to at least approximately the full luminance of the light source. In practice, the full luminance can of course suffer certain reductions in some places, e.g. due to inhomogeneities in the light source or defects, due to 3D effects or manufacturing tolerances of a reflector surface or the like, so that the full luminance may only be approximately achieved in some points. Apart from such practical effects, such a concentrator in the form of a CPC or CPC-type element transforms the light from the light source orIn the present case, however, the light received from the light mixing rod enters the aforementioned beam, in whose radiation area, at least theoretically, every point is exposed to the full luminance of the light source.

[0077] When viewed within the radiation area back into the CPC or CPC-like element, from any point within the radiation area, all visible, photoactive surfaces of the CPC or CPC-like element are fully exposed to the light from the light source, so that the entire, defined radiation area illuminates with virtually no holes. Accordingly, a new light source is created, which has been enlarged to the diameter of the optics or the CPC or CPC-like element, but radiates at a smaller solid angle than the actual light source.

[0078] In conjunction with the upstream light mixing rod, such a CPC or CPC-like element can achieve a quasi-homogeneous beam cone or beam cylinder in terms of light color, so that no different colored dots are visible in the illuminated target area or in the light cone, even by actors looking into the light, but rather a uniformly distributed, quasi-homogeneous light distribution is perceptible. More precisely, the mixing rod in question achieves such quasi-homogeneous light mixing. The CPC or CPC-like element focuses the mixed light onto the target area to be illuminated.

[0079] Such a CPC element, known as a compound parabolic concentrator element, is, in its original form, a concentrator composed of two curves and is typically used in solar technology. In its classic design, such a CPC element is composed of two parabolas; however, modifications have also become known in which the contour of the concentrator element is defined by other curves rather than parabolas. Such modified concentrators—provided they are no longer parabolic—are referred to as CPC-type elements. What CPC elements and modified CPC-type elements have in common is that they transform the light coming from the light rod into a beam of rays in the manner described above, in whose radiation area every point is exposed to the full luminance of the light source.

[0080] In order to achieve further light mixing, the said CPC or CPC-like element can be provided with a faceting, in particular a plurality of facets provided on the lateral surface.

[0081] The invention is explained in more detail below with reference to preferred embodiments and the accompanying drawings. In the drawings: Fig. 1: a longitudinal sectional view of a zoom emitter according to an advantageous embodiment of the invention, wherein in partial view a the zoom emitter and its beam path are shown with the expansion foil removed and in partial views b, c and d the zoom emitter with the expansion foil inserted in different zoom positions, Fig. 2: a longitudinal sectional view of the zoom emitter from Fig. 1 , whereby a different expansion film is used, which, in contrast to the one in Fig. 1used expansion film forms an increasingly elliptical beam when the expansion film is moved increasingly close to the bundling axis and the beam angle is increasingly widened, Fig. 3: a longitudinal sectional view of the zoom radiator from the previous figures, wherein yet another expansion film is inserted between the light source and the bundling optics, which forms an increasingly rectangular beam depending on the zoom position, wherein the beam becomes increasingly angular the closer the expansion film is moved to the bundling optics and the more the beam is expanded, Fig.4: a longitudinal sectional view of a zoom spotlight similar to the preceding figures, wherein a plurality of scattering and / or expanding foils are provided between the light source and the focusing optics, which foils can be moved back and forth independently of one another between the light source and the focusing optics in order to set various zoom effects, wherein partial views b, c and d show the two scattering and / or expanding foils in various zoom positions, Fig. 5: a longitudinal sectional view of a zoom spotlight similar to the preceding figures, wherein the focusing optics is designed in several parts and comprises a plurality of optical elements, Fig. 6: a longitudinal sectional view of a zoom spotlight whose focusing optics comprises a reflector, wherein partial views a and b show the scattering and / or expanding element in different zoom positions with different distances from the reflector and thus different beam angles of the beam emitted by the reflector, Fig.7: a longitudinal section through a zoom emitter with individually longitudinally adjustable bundling optics and also individually longitudinally adjustable zoom element according to an advantageous embodiment of the invention, according to which zoom and bundling optics sleeves are provided which can be adjusted longitudinally by rotating, Fig. 8: a partial detailed view of the fastening of the scattering and / or expanding element to an interchangeable holder which is longitudinally adjustable by means of the said rotatable holder sleeve, Fig. 9: an exploded view of the components of the zoom emitter from . Fig. 7 , and Fig. 10: a perspective view of the telescopically nested, sleeve-shaped holders for the bundling optics and the zoom element.

[0082] As the figures show, the zoom spotlight 1 comprises a light source 2, which can be configured, for example, as an LED or as an LED array. However, other, preferably point-shaped light sources are also conceivable. To adjust the light color in the area of ​​the light source 2, multicolored LED modules can also be combined or provided.

[0083] A mixing optics 3 can be arranged downstream of the light source 2, for example in order to be able to mix the light when using several LED components, in particular to mix different colored light components to form a homogeneous, colored light.

[0084] As the figures show, the mixing optics 3 can comprise a light mixing rod 4, which faces the said light source with its entrance end, so that the light source 2 can radiate its light substantially completely into the light mixing rod 4.

[0085] A bundling optical element 5 can be arranged downstream of the light mixing rod 4, which can be designed, for example, in the form of a CPC or CPC-like element.

[0086] As the figures show, the light mixing rod 4 can be directly connected to the respective associated optical elements 5 and placed directly next to one another. For example, the CPC-type optical element 5 can be cast onto the light mixing rod 4 or integrally connected in one piece, using a homogeneous material. Alternatively, the optical element 5 can also be formed separately and optically tightly connected to the mixing rod 4 using an optically transparent adhesive. In particular, the light exit surface of the light mixing rod 4 and the light entry surface of the optical element 5 can be connected to one another over the entire surface and without a gap.

[0087] The light mixing rod 4 can generally have a circular-cylindrical contour. Alternatively, the light mixing rod 4 can also be controlled in a shape that deviates from the circular-cylindrical shape, in particular having a polygonal, for example, square, cylindrical shape in the manner of an edge profile or an extruded profile.

[0088] Regardless of the enveloping surface cross-sectional shape, the light mixing rod can have a profile on its lateral surface which - viewed in cross-section - can have a wavy contour, which can, for example, comprise alternating, approximately equally wide, rounded wave troughs and wave crests. Such wave troughs and crests in the form of, for example, longitudinal grooves and longitudinal ribs, which can be concavely curved or convexly curved on the lateral surface of the mixing rod, can be provided in particular at the light entry end of the mixing rod 4 or, starting from there, taper off towards the light exit end of the mixing rod 4 into a lateral surface which is, for example, smooth, i.e., essentially profile-free, without grooves or ribs, which can then merge into the optical element 5. In principle, however, other designs are also possible with regard to the mixing rod and the optical element 5, where appropriate.one of these elements or both elements, i.e. the mixing rod 4 and the optical element 5, can be dispensed with.

[0089] The light beam 6 emerging from the mixed optics 3 – or possibly directly from the light source 2 – strikes a zoom element 7 and is directed by this onto a bundling optic 8, which then emits the zoom beam 9 of the zoom emitter 1, the beam angle of which can be variably adjusted using the zoom element 7. For example, the zoom function can be designed such that the zoom beam 9, like a spotlight, has no widening or a beam angle of 2 times 0°, cf. for example Figure 1a and Figure 1b , wherein the beam angle is preferably continuously variable or, if necessary, also gradually adjustable up to a maximum beam angle of, for example, 2 times 30°, as Figure 1d shows, or can be widened 2 times 45°.

[0090] The said bundling optics 8 can comprise a bundling lens 10, as is the case with Figures 1 to 3 show, wherein such a lens 10 can fundamentally have different contours, for example, it can be spherically or aspherically curved, but freeform surface lenses can also be used.

[0091] How Figure 6 shows, the bundling optics 8 can also comprise a reflector 11 which reflects the light beam coming from the zoom element 7 and thereby bundles it into the zoom beam 9, cf. Figure 4 .

[0092] Mixed forms of bundling optics are also possible, which may include a lens with a reflective surface or a lens and a reflector.

[0093] The zoom element 7 between the light source 2 and the bundling optics 8 is arranged between the bundling optics 8 and the mixing rod 3 or the optical element 5 when using a mixing rod 3 and / or a CPC-type optical element 5, cf. Figures 1 to 6 .

[0094] The zoom element 7 mentioned is a thin-walled, in particular disc-shaped scattering and / or expanding element 12 or the zoom element 7 comprises such a scattering and / or expanding element 12 which is designed to scatter and / or is provided with a light-scattering scattering and / or expanding structure.

[0095] In particular, the aforementioned scattering and / or expanding element 12 can be designed as a scattering film. Such a scattering film can, for example, be a translucent plastic film with a scattering and / or expanding structure.

[0096] The aforementioned scattering and / or expanding structure 13 can comprise a surface structuring, for example in the form of a roughened and / or micro-beveled or otherwise relief-like surface structure. Alternatively or additionally, the scattering and / or expanding structure 13 can also comprise a particle structure embedded in the material of the scattering film or the scattering and / or expanding element 12, which scatters the light passing through the scattering and / or expanding element 13.

[0097] As the figures show, the scattering and / or expanding element 12 can be shifted or moved at least approximately parallel to the main beam direction 14 of the light beam 6 passing through the scattering and / or expanding element 12 in order to be positioned closer to or further away from the bundling optics 8. Advantageously, the scattering and / or expanding element 12 can be adjusted along the entire distance between the light source 2—or, when using a mixing rod 3 and / or a CPC-type optical element 5, from the light exit surface of the mixing rod 3 or the optical element 5—to the bundling optics 8, so that the scattering and / or expanding element 12 is positioned at least approximately directly on the light exit surface of the light source 2 (or the mixing rod 3 or the optical element 5) in one end position and at least approximately directly on the bundling optics 8 in another end position.This allows a large zoom adjustment range to be achieved.

[0098] The scattering and / or expanding element 12 is expanding, as symbolized by the small arrows on the light exit side of the scattering and / or expanding element 12, so that the scattered or expanded light cone or the light bundle strikes the lens 10 or the reflector 11, as the figures illustrate.

[0099] Depending on the position, i.e. the spacing of the scattering foil or the scattering and / or expanding element 12 from the bundling optics 10, the zoom beam or the zoom beam bundle 9 emitted by the zoom emitter 1 is zoomed in to a lesser or greater extent, cf. Figure 1 , comparing the partial representations b, c and d.

[0100] If the scattering and / or expanding element 12 is located essentially directly on the light exit surface of the light source 2 or the mixing optics 3, essentially no zoom effect occurs or the zoom beam 9 emitted by the bundling optics 8 has essentially the same shape as if no scattering and / or expanding element 12 is used, as can be seen from a comparison of the partial views a and b of the Figures 1 , 2 and 3 clarified.

[0101] Advantageously, the scattering and / or expanding element 12 can be exchanged to enable different zoom types to be realized. For example, a scattering and / or expanding element 12 can be used that generates a zoom beam 9 with a substantially circular cross-section, see FIG. Figure 1 . For this purpose, the scattering and / or expanding element 12 can, for example, be designed to scatter uniformly in all directions.

[0102] Alternatively, for example, a scattering and / or expanding element 12 can be used, which generates an increasingly elliptical or oval zoom beam bundle as it is positioned increasingly closer to the bundling optics 8, cf. Figure 2 , there in particular the partial views c and d. Such a scattering and / or expanding element 12 can, for example, have a scattering and / or expanding structure 13 which is designed to be directionally scattering, so that an expansion in a first main direction is greater than an expansion in a second main direction perpendicular thereto.

[0103] Alternatively or additionally, a scattering and / or expanding element 12 can also be used, which generates an increasingly angular zoom beam 9 with increasingly closer positioning to the bundling optics 8, cf. Figure 3 This can be achieved, for example, by appropriately forming the scattering and / or expanding structure 13 or by contouring the outline thereof.

[0104] In order to be able to easily change or exchange the spreading and / or expanding elements 12, a change holder 15 can advantageously be provided, cf. Figure 3 , which holds the respective scattering and / or expanding element 12 in the beam 6 between the light source 2 and the bundling optics 6, in particular in an orientation substantially perpendicular to the main beam direction 14 of the light source 2 or of the mixing optics 3 arranged downstream of the light source.

[0105] For adjusting the scattering and / or expanding element 12, for example, a slide guide can be provided, wherein such a slide guide 16 can have a main slide 17 which can be mounted so as to be movable essentially parallel to the main beam direction 14.

[0106] Advantageously, the slide guide 16 further comprises an auxiliary slide 18, which can be mounted on said main slide 17, advantageously displaceable relative to the main slide 17 in a direction transverse to the main beam direction 14 of the light source 2, cf. for example Figure 2 or Figure 4 , which show the slide guide 16.

[0107] Such a cross-slide guide can be particularly advantageous when a scattering and / or expanding element 12 with differently colored sections is used, so that by transversely displacing the scattering and / or expanding element 12, the portions of the light beam 6 which irradiate through the section of one color and, on the other hand, the section of the other color can be adjusted in order to be able to vary the mixed color produced thereby, as explained at the beginning.

[0108] How Figure 4shows, a plurality of scattering and / or expanding elements 12 can also be provided between the light source 2 and the bundling optics 8 or between the mixing optics 3 and the bundling optics 8, wherein the said plurality of scattering and / or expanding elements 12 can advantageously each be designed as a scattering and / or expanding film.

[0109] The multiple scattering and / or expanding elements 12 can be provided with identical expanding structures, but can also have different expanding structures. For example, one film can be provided with a targeted scattering structure and one film with a diffuse scattering structure.

[0110] How Figure 4As shown, the two scattering and / or expanding elements 12 can advantageously be adjusted in their position independently of one another, in particular can be moved back and forth independently of one another between the light source 2 and the bundling optics 8. Advantageously, each of the scattering and / or expanding foils can be mounted on a slide guide 16, wherein, for example, a common main slide guide can be provided for the main slides 17 of the scattering and / or expanding elements 12.

[0111] How Figure 5 shows, the bundling optics 8 can also comprise several optical elements 10, for example in the form of several lenses or be designed in several parts. Instead of two lenses 10, as is the case with the Figure 5 shows, the bundling optics 8 can, for example, also comprise a lens and a reflector, or other mixed forms such as several lenses combined with a reflector.

[0112] As the Figures 7 and 8show, the aforementioned interchangeable holder 15 has an annular film carrier 15a to which the film-like spreading and / or expanding element 12 can preferably be releasably fastened, in particular in a form-fitting and / or force-fitting manner. Various fastening means can be used, which are preferably designed to be manually releasable, in particular can be loosened and tightened without tools or with simple standard tools such as a screwdriver, an Allen key, or a clamping pliers. Advantageously, the aforementioned fastening means can be designed to work in a form-fitting and / or force-fitting manner, wherein in an advantageous further development of the invention, for example, bayonet locking means can be provided on the aforementioned film carrier 15a, into which correspondingly designed edge sections of the spreading and / or expanding elements can be inserted and positively locked by twisting.Alternatively or additionally, clamping elements for clamping the respective spreading and / or expanding element 12 can also be provided on the film holder 15a. Alternatively or additionally, locking elements, for example in the form of clip elements, can be provided to engage or clip the respective spreading and / or expanding element 12 onto the film carrier 15a. Alternatively, it would also be possible to provide force-locking holding means, such as an adhesive, especially if the entire film carrier 15a is releasably attached.

[0113] How Figure 8shows, the annular film carrier 15b can be fastened at the end face and / or at an end section to a preferably sleeve-shaped zoom carrier 15b, wherein the fastening can advantageously be designed to be releasable. Such releasable fastening means can, for example, comprise screw or locking means such as clips or also tensioning or clamping elements that can be loosened and tightened manually or using simple tools such as a screwdriver. Alternatively or additionally, the aforementioned film carrier 15a can also have bayonet locking means in order to be secured in a bayonet-like manner and thus in a form-fitting manner by twisting with complementary contours of the zoom carrier 15b. Alternatively or additionally, the film carrier 15a could also be glued to the zoom carrier 15b.

[0114] As the Figures 7 and 10As illustrated, the focusing optics 8 and the zoom element 7 can each be individually adjusted relative to one another and relative to the light source 2, in particular longitudinally displaced parallel to the main beam direction 14. For this purpose, the focusing optics 8 and the zoom element 7 can each be attached, for example, to an adjustment sleeve, which can be mounted or attached to the radiator housing 60 via a screw thread 50, 51. If the sleeve-shaped zoom carrier 15b is rotated, the zoom carrier 15b undergoes a longitudinal displacement relative to the radiator housing 60 and thus relative to the light source 2 and the focusing optics 8 via the screw thread 50.

[0115] On the other hand, if the bundle optics carrier 61, which is also sleeve-shaped, is rotated, the bundle optics 8 undergoes a longitudinal adjustment in the direction of the main beam direction relative to the zoom element 7 and relative to the light source 2 via the screw thread 51. Thus, both the bundle optics 8 and the zoom element 7 can each be adjusted individually.

[0116] The bundle optics carrier 61 can - independently of its screw thread mounting - simultaneously form a detachable cover of the radiator housing 60, which, when opened or removed, allows access to the interchangeable carrier 15. As the Figures 7 and 10As can be seen from the drawings, the sleeve-shaped bundle optics carrier 61 can be pulled out or rotated from the front side of the radiator housing 60, whereby the film carrier 15a at the front end section of the zoom carrier 15b and thus the scattering and / or expanding film 12 becomes accessible and can be exchanged in the manner described in order to achieve a different type of zoom.

Claims

1. A zoom spotlight with variable beam angle, comprising at least one light source (2), a focussing optical system (8) for emitting a zoom beam (9), and a zoom element (7) for adjusting the beam angle of the zoom beam (9) emitted by the focussing optical system (8), wherein the zoom element (7) is a thin-walled scattering and / or expanding element (12), which is provided with a light-scattering and / or expanding scattering and / or expanding structure (13) and is provided between the focussing optical system (8) and the light source (2), wherein said scattering and / or expanding element (12) and / or the focussing optical system (8) is / are mounted so as to be movable to and fro for adjusting the beam angle of the emitted zoom beam (9), characterised in that a swap-out holder (15) for exchanging the scattering and / or expanding element (12) and inserting differently configured scattering and / or expanding elements (12) for producing differently contoured and / or differently coloured beams has an annular film holder (15a) for holding the thin-walled scattering and / or expanding element (12) in a form-fitting and / or frictionally engaged manner, which film holder (15a) is fastened releasably to an adjustably mounted holder sleeve (15b), wherein the swap-out holder (15) is mounted so as to be movable longitudinally displaceably substantially parallel to the main beam direction (14) along the entire path from the light source (2) to the focussing optical system (8), so that the scattering and / or expanding element in one end position is positioned directly at the light exit surface of the light source (2) and in another end position is positioned directly at the focussing optical system (8).

2. A zoom spotlight with variable beam angle, comprising at least one light source (2), a mixing optical system (3), which has a light mixing rod (4), to which a CPC-like, focussing optical element (5) is attached optionally, a focussing optical system (8) for emitting a zoom beam (9), and a zoom element (7) for adjusting the beam angle of the zoom beam (9) emitted by the focussing optical system (8), wherein the zoom element (7) is a thin-walled scattering and / or expanding element (12), which is provided with a light-scattering and / or expanding scattering and / or expanding structure (13) and is provided between the focussing optical system (8) and the light source (2), wherein said scattering and / or expanding element (12) and / or the focussing optical system (8) is / are mounted so as to be movable to and fro for adjusting the beam angle of the emitted zoom beam (9), characterised in that a swap-out holder (15) for exchanging the scattering and / or expanding element (12) and inserting differently configured scattering and / or expanding elements (12) for producing differently contoured and / or differently coloured beams has an annular film holder (15a) for holding the thin-walled scattering and / or expanding element (12) in a form-fitting and / or frictionally engaged manner, which film holder (15a) is fastened releasably to an adjustably mounted holder sleeve (15b), wherein the swap-out holder (15) is mounted so as to be movable longitudinally displaceably substantially parallel to the main beam direction (14) along the entire path from the light exit surface from said mixing rod (3) or the optionally provided CPC-like, focussing optical element (5) to the focussing optical system (8), so that the scattering and / or expanding element in one end position is positioned directly at the light exit surface of said mixing rod (3) or the optionally provided CPC-like, focussing optical element (5) and in another end position is positioned directly at the focussing optical system (8).

3. The zoom spotlight according to the preceding claim, wherein the differently configured scattering and / or expanding elements (12) for producing differently contoured beam bundles are configured to scatter differently and / or expand differently, wherein said scattering and / or expanding elements have a mutually corresponding fastening contour for releasable fastening to the same fastening contour of the same swap-out holder (15).

4. The zoom spotlight according to either one of the two preceding claims, wherein the swap-out holder (15) is mounted so as to be movable transversely displaceably transversely to the main radiation direction (14), wherein a cross-slide guide (16, 17, 18) for longitudinally and transversely displaceable mounting of the swap-out holder (15) is provided.

5. The zoom spotlight according to any one of the preceding claims, wherein a spotlight housing (60) comprises a releasable or openable cover for closing a swap-out opening, through which the scattering and / or expanding element (12) and / or a carrier element (15a) of the swap-out holder (15) can be removed and inserted, wherein preferably an optical system holder (61), on which the focussing optical system (8) is held, can be removed together with the focussing optical system (8) from the end face of the spotlight housing (61) and, by removal from the spotlight housing (6), frees the swap-out opening arranged at the end face.

6. The zoom spotlight according to any one of the preceding claims, wherein the swap-out holder (15) has manually releasable fastening means, in particular fastening means which can be released without tools or by using standard tools such as a screwdriver, for fastening an inserted scattering and / or expanding element (12).

7. The zoom spotlight according to any one of the preceding claims, wherein the scattering and / or expanding element (12) and the focussing optical system (8) are each mounted so as to be individually movable to and fro relative to one another and relative to the light source (2), in particular are mounted so as to be longitudinally displaceable substantially parallel to the main beam direction (14) and / or transversely to the main beam direction (14).

8. The zoom spotlight according to one of the preceding claims, wherein the scattering and / or expanding element (12) comprises at least one scattering and / or expanding film.

9. The zoom spotlight according to one of the preceding claims, wherein the scattering and / or expanding structure (13) comprises - a surface structure, and / or - a deliberately widening, cloud-like relief structure, and / or - a particle structure embedded in the interior of the scattering and / or expanding element (12), and / or - a micro- and / or nanostructure with relief and / or particle elements with an extent of < 1 mm or < 1 µm.

10. The zoom spotlight according to one of the preceding claims, wherein the scattering and / or expanding structure (13) is configured to radiate uniformly in different directions.

11. The zoom spotlight according to one of claims 1 to 9, wherein the scattering and / or expanding structure (13) - is configured to be directionally scattering, so that the expansion in a first main direction is stronger than the expansion in a second main direction perpendicular thereto, and / or - in different portions of the scattering and / or expanding element (12) is configured to expand or scatter to different degrees.

12. The zoom spotlight according to one of the preceding claims, wherein the scattering element (12) has differently configured, in particular differently structured and / or differently coloured, portions and is mounted so as be movable transversely to the main beam direction (14) of the light beam (6) passing through the scattering element (12), so that the differently configured portions of the scattering and / or expanding element (12) are movable into the light beam (6) passing through, wherein a colour adjustment device is provided which, by transverse displacement of the scattering element (12), changes the components of the beam which pass through a first colour portion of the scattering element (12) on the one hand and through a second colour portion of the scattering element (12) on the other hand, and hereby changes the colour of the light beam emerging from the scattering element (12).

13. The zoom spotlight according to one of the preceding claims, wherein a / the colour adjustment device - has at least one coloured disc which is provided in addition to the scattering and / or widening element (12) and is movable into the light beam (6) passing through the scattering and / or widening element (12), and / or - comprises at least one wave-optically active colour element for changing the light colour by wave-optical extinction.

14. The zoom spotlight according to one of the preceding claims, wherein the scattering and / or expanding element (12) is formed in multiple parts and / or a plurality of scattering and / or expanding elements (12) are provided, wherein the plurality of scattering and / or expanding elements and / or parts are preferably adjustable independently of one another, in particular are mounted so as to be movable to and fro between the focussing optical system (8) and the light source (2).

15. A zoom spotlight set comprising a plurality of zoom spotlights, which are each configured according to one of the preceding claims, wherein the plurality of zoom spotlights have differently configured scattering and / or expanding elements (12), which have a mutually corresponding fastening contour for fastening to a similarly configured holder, wherein - a first zoom spotlight has a scattering and / or expanding element (12) for generating a first beam which is circularly or elliptically or ovally or angularly contoured, and a second zoom spotlight has a scattering and / or expanding element (12) for generating a second beam which is contoured differently from the first beam and is selected from the group of circularly, elliptically, ovally and angularly contoured, or - a first zoom spotlight has a scattering and / or expanding element (12) for generating a first beam of a first colour, and a second zoom spotlight has a scattering and / or expanding element (12) for generating a second beam of a second colour which differs from the first colour.