MEDICAL LIGHT

Description

[0001] The present invention relates to a medical lamp, in particular a dental treatment lamp, with the aid of which the intraoral illumination of an operating field takes place.

[0002] To ensure the quality of medical treatment, it is essential that the examination or treatment site is adequately illuminated. Medical treatment lights are designed to illuminate the area to be examined or treated with an optimized light field that supports the examination and / or treatment.

[0003] In the case of dental lighting, the properties of this light field are defined by various standards. One of these is EN ISO 9680, which stipulates, for example, that the color rendering index (CRI) must be greater than 85, a minimum illuminance of 15,000 lux must be present, and the light field must have a color temperature between 3,600 and 6,400 Kelvin. Furthermore, to avoid irritation or even eye damage to the patient, the light field must have a sufficiently steep drop at the edges so that a strictly limited space around the treatment site is illuminated in the object plane.

[0004] A luminaire which meets the above requirements is known, for example, from EP 2 469 159 B1 in the name of the applicant. This luminaire has a plurality of lighting units, each with its own light source and its own optics. The light from the light source of a lighting unit, which is implemented using a plurality of LEDs, is influenced by the optics in such a way that a predetermined, usually approximately hexagonal area is illuminated at a certain distance in front of the luminaire, in the so-called object plane. The plurality of lighting units in this known luminaire are designed and positioned in such a way that they all jointly illuminate the corresponding area in the object plane, so that overall a homogeneously illuminated light field is created. If the light from an individual lighting unit, for example, is...If the area under examination is shadowed, for example, by a doctor's arm or otherwise, the light field is still illuminated by the other, unshaded lighting units. This ensures that the area under examination is illuminated as shadow-free as possible.

[0005] The well-known luminaire described above has proven itself in practice many times over. However, the manufacture of this luminaire involves a relatively complex assembly of the individual components, as achieving a homogeneously illuminated light field requires precise alignment of the individual light units. Deviations from this would result in undesirable brightness or color changes in the peripheral area of the light field.

[0006] A further problem is that the coordinated alignment of the individual lighting units results in the corresponding beams of light only precisely overlapping at a fixed distance from the luminaire. The desired homogeneous illumination of the light field is therefore primarily achieved at a specific plane in front of the luminaire. However, if this ideal distance is deviated from, the quality of the light field deteriorates.

[0007] Typically, the light is actually intended to be placed at a fixed distance from the area to be examined. However, this is not always possible, and it would therefore be desirable if the quality of the light field were less dependent on the distance of the light from the area to be illuminated.

[0008] US 2007 / 0147041 A1 also discloses a luminaire for general lighting purposes, in which the light from a light source is used to uniformly illuminate a light field. In this case, the optical system used consists of a plate-like collimator and a plate arranged downstream of the collimator, which is provided with lens-like structures. This results in a relatively simple overall design that helps achieve a symmetrically illuminated light field.

[0009] As mentioned at the beginning, the light field should be relatively strictly limited to avoid, for example, dazzling a patient being examined. This means that illumination should only be provided within a specific, predefined area, while the surrounding area should not be illuminated. However, it has been shown that excessive brightness differences can be tiring for the observer, as they place excessive strain on the adaptive function of the human eye.

[0010] The present invention is based on the object of providing a medical lamp that is optimized with regard to the above-mentioned aspects.

[0011] This object is achieved by a medical lamp, in particular a dental treatment lamp, having the features of claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0012] A key difference between the luminaire according to the invention and the solution known from EP 2 469 159 B1 is that the luminaire now has a single lighting unit with a single, essentially point-shaped LED light source. This can be a single LED or a compact LED cluster. However, multiple lighting units are not provided, which then have to be laboriously assembled and aligned with one another, as explained above, in order to achieve efficient and uniform illumination of a light field. Instead, the light emitted by the individual point-shaped LED light source is influenced in a special way with the aid of optical means in order to achieve homogeneous and uniform illumination of a light field, which is then, however, less dependent on the distance of the area to be illuminated from the luminaire.The optical means comprise a collimator and a cover plate, both components being provided with light-directing structures and components in a specific manner in order to enable optimized illumination of the light field despite a compact design.

[0013] Furthermore, in contrast to the solution of EP 2 469 159 B1 or US 2007 / 0147041 A1, it is intended to additionally influence the brightness gradient in the edge region of the light field, which, as already mentioned, should otherwise be homogeneously illuminated. Here, the optical means are designed such that the light field is asymmetrically expanded in one direction.

[0014] According to the present invention, a medical, in particular a dental, treatment light for the intraoral illumination of a surgical field is proposed, which comprises a lighting unit with illuminating means and optical means for generating a light field in an object plane. The illuminating means are formed by a substantially point-shaped LED light source, and the optical means comprise a plate-like collimator and a cover plate. wherein the collimator has a central region which is provided with light-refracting structures on a side facing away from the LED light source, and an outer region surrounding the central region which is provided with structures designed for total reflection on a side facing the LED light source, and wherein the cover plate is provided with a lens structure which has a plurality of individual lenses which are designed to project the light emitted by the collimator and entering the lenses onto the object plane.

[0015] The back of the central area of the collimator facing the LED light source is provided with partial surfaces which have an inclination with respect to a plane of the collimator and thus to the object plane in order to asymmetrically widen the light field in one direction.

[0016] Both components of the optical system are therefore specially designed to optimally influence the light emitted by the LED light source. The inventive design of the collimator takes into account that the spectral composition of the light emitted by a white-light LED light source depends on the angle at which the light is emitted. It is a well-known phenomenon of white-light LEDs that light emitted essentially perpendicular to the surface of the LED generally has a higher color temperature, i.e., a slightly bluish component, whereas light emitted strongly laterally has a lower color temperature and accordingly appears slightly yellowish.The inventive design of the collimator takes this effect into account and ensures that, on the one hand, a central light field is formed, which is attributable to the light emitted essentially perpendicularly by the LED light source, and, on the other hand, an outer light field is formed, which is formed by the light emitted laterally by the LED light source. The appropriate superposition of the central and outer light fields, which is achieved by the design of the cover plate, ultimately ensures that the final light field is actually evenly illuminated and that no color or color temperature changes occur in the edge area.At the same time, the use of a single light source in combination with the optical system designed according to the invention ensures that the uniform illumination of the light field is less dependent on the distance to the luminaire, which is why the problems known in the prior art described above are avoided.

[0017] The asymmetric widening of the light field according to the invention also leads to, for example, the brightness gradient at the upper and lower edges of the light field being influenced, whereby in the lower area in particular, the brightness drop in the edge region is less pronounced and, accordingly, less strong brightness contrasts occur than in the opposite edge region. Thus, undesired glare of a patient at the upper edge region of the light field is still avoided, since there is a sharp demarcation of the illuminated area from the surroundings. At the same time, excessively strong contrasts are avoided in the opposite edge region, thereby reducing fatigue for an observer, for example, the attending physician.

[0018] The asymmetric widening of the light field is thus achieved by the fact that the back of the central area of the collimator facing the LED light source is provided with partial surfaces which have an inclination compared to the plane of the collimator and thus to the object plane.

[0019] In particular, it can be provided that at least some of the partial surfaces, preferably all of them, are each tilted about an axis that lies in the plane (E3) of the collimator (40) and is substantially perpendicular to the direction of the asymmetric expansion. An alternative or additional possibility for achieving the asymmetric expansion of the light field can further consist in at least some of the lenses forming the lens structure being tilted with respect to the plane of the collimator about an axis that is oriented substantially perpendicular to the direction of the asymmetric expansion.

[0020] Preferably, the partial surfaces are formed by strip-shaped surface regions, each extending substantially perpendicular to the direction of the asymmetrical widening along its respective tilt axis. It can further be provided that the strip-shaped surface regions are concavely curved with respect to the direction of the asymmetrical widening, wherein the strip-shaped surface regions are particularly preferably each formed symmetrically with respect to a plane that is perpendicular to the plane of the collimator and is spanned by an axis running parallel to the direction of the asymmetrical widening. This measure results in a certain, but now symmetrical, widening of the light field being achieved in terms of width.

[0021] As an alternative to the strip-shaped partial areas, it would also be conceivable for the partial areas to be tile-shaped partial areas that cover the rear side of the central region of the collimator facing the LED light source in a matrix-like manner. In this case, analogous to the above-mentioned concave design of the tile-shaped partial areas, it can then be provided that at least some of the tile-shaped partial areas are tilted with respect to the plane of the collimator about an axis that runs parallel to the direction of the asymmetric widening, wherein in particular the majority of the tile-shaped partial areas are arranged symmetrically with respect to a plane that is perpendicular to the plane of the collimator and is spanned by an axis that runs parallel to the direction of the asymmetric widening. This measure again leads to a certain widening of the light field in terms of width.

[0022] The light-refracting structures of the central region of the collimator preferably form a so-called Fresnel structure. Furthermore, it is preferably provided that the structures of the collimator designed for total internal reflection form a further Fresnel structure facing the LED light source, which, in a projection perpendicular to the plane of the collimator, surrounds the central region in a ring-like manner. This design of the structures of the collimator makes it possible to design it in principle in the shape of a disk and nevertheless influence the light from the LED light source efficiently. This enables a compact design of the entire lighting unit. The light-refracting structures of the central region and the structures of the outer region of the collimator designed for total internal reflection can preferably have a common rotational symmetry. It is preferably provided that these structures form aspherical surface regions.

[0023] The lenses of the cover plate, which is also used according to the invention, are preferably arranged on a side of the cover plate facing the LED light source. In particular, if the cover plate forms an outer surface of the luminaire, the side of the cover plate facing away from the LED light source can be smooth. This, in particular, prevents dirt particles from accumulating on the surface of the luminaire and thus facilitates its cleaning.

[0024] Analogous to the collimator, the lens structure of the cover plate can also have an inner area and an outer area, whereby Lenses of the inner region are designed to project the light emitted by the central region of the collimator in the form of a central light field onto the object plane, lenses of the outer region are designed to project the light emitted by the outer region of the collimator in the form of an outer light field onto the object plane, and wherein the central light field and the outer light field preferably overlap substantially completely. In particular, it can be provided that each individual lens of the inner or outer region completely projects the corresponding central or outer light field. This measure, in turn, ensures that, even if part of the light emitted via the cover plate of the lamp is obscured, for example by an arm or the head of the attending physician, complete and still substantially homogeneous illumination of the desired area is achieved.

[0025] The lenses of the inner region can be substantially square, whereas the lenses of the outer region have a greater extension in the direction of an axis of the collimator which is perpendicular to the direction of the asymmetric expansion than in an axis which is parallel to the direction of the asymmetric expansion.

[0026] Ultimately, the present invention provides a luminaire that enables optimized illumination of a treatment area, while the light-emitting unit of the luminaire comprises relatively few components, resulting in simplified manufacture and assembly of the luminaire overall. In particular, however, it retains the advantage that the quality of the illumination of the light field is less dependent on the distance to the luminaire.

[0027] The invention will be explained in more detail below with reference to the accompanying drawings. They show: Figure 1 shows a perspective view of a medical lamp in which the lighting unit designed according to the invention is used; Figure 2 shows a schematic view of the light field that can be achieved with the aid of the lamp according to the invention; Figure 3 shows an illustration of the various components of the lighting unit according to a first embodiment; Figure 4 shows an enlarged view of a partial area of the collimator of Figure 3 ; Figure 5 shows a further enlarged view of a partial area of the collimator; Figure 6 shows the front side of the collimator facing away from the LED light source; Figure 7 shows the rear side of the collimator facing the LED light source; Figure 8 shows a view of the various components of the lighting unit according to a second embodiment; Figure 9 shows an enlarged view of a partial area of the collimator from Figure 8; Figures 10 and 11 show further sectional views of the collimator according to the second embodiment; Figure 12 shows the front side of the collimator according to the second embodiment facing away from the LED light source; Figure 13 shows the rear side of the collimator according to the second embodiment facing the LED light source; and Figure 14 shows a view of the cover plate provided with the lens structure.

[0028] Figure 1 shows a perspective view of a medical lamp, generally designated by reference numeral 100, in particular a dental treatment lamp, with the aid of which the operating field of a dental workstation is to be illuminated. The lamp 100 is designed in accordance with the invention, i.e., equipped with the lighting unit described in detail below, although the external shape of the lamp could, of course, also be designed differently. The illustration in Figure 1serves primarily to illustrate the planes and directions to which reference is made in the later explanation of the optical components of the lighting unit according to the invention.

[0029] Basically, the light 100 has a light head 110, which is adjustably mounted on an articulated arm 105 (not shown in detail) such that it can be aligned to the surgical area as desired. The housing 111 of the light head 110 has two lateral handles 112 for its adjustability, which enable manual alignment of the light 100.

[0030] In the representation according to Figure 1It is assumed that the orientation of the lamp head 110 is such that light is directed substantially horizontally along an axis A, which corresponds to the main axis of the optical system of the lamp 100, onto an area located in front of the lamp 100. In this illustration, the Figure 1The plane E2 shown is aligned horizontally, and the plane E1 is shown perpendicular to this and running through the main axis of the optical system A. The two axes I1 and I2 running in the planes E1 and E2 as well as the optical axis A are then each perpendicular to one another. As already mentioned, the lamp head 110 can of course also be pivoted during use in such a way that the plane E2 is not aligned horizontally, but runs diagonally downwards or inclined. This will be the case in particular if the lamp 100 is located above a patient in a lying position. For the following explanation, however, it is assumed that the plane E2 is aligned horizontally.

[0031] With the aid of the luminaire 100 according to the invention, in a specific area in front of the luminaire 100 in the so-called object plane O (see Figures 1 and 3 ) a schematic in the Figures 1 and2illustrated light field 200 can be achieved. The object plane O is parallel to the plane E3 of the collimator described in more detail below and thus, together with this, is aligned perpendicular to the optical axis A, whereby it should be noted that the distance between the plane E3 of the collimator E3 and the object plane O and thus the distance between the lamp 100 and the light field 200 will in reality be greater than is shown in the figures. As already mentioned above, the following explanations of the design of the optical components of the lamp 100 assume that the optical axis A runs horizontally and, accordingly, the object plane O and the plane E3 are aligned vertically. However, depending on the orientation of the lamp head 110 during actual use of the lamp 100,the optical axis A may also have an inclination or, in extreme cases, even point vertically downwards, which then leads to a corresponding change in the alignment of the various planes.

[0032] The light field 200 has a slightly rounded, but essentially rectangular shape, wherein the light field 200 extends further in the horizontal direction - along the axis O2 - than in the vertical direction along the axis O1. A special feature of the invention is that - as explained in more detail below - due to the special design of the optical means, the light output of the luminaire 100 is slightly asymmetrically widened in one direction - in the illustrated example in the vertical direction. As can be seen from the lines schematically representing the light field 200 in Figure 2As indicated, this means that in its upper edge region 201 the light field 200 is strongly demarcated from the surroundings, thus creating a high brightness gradient at the transition from the light field 200 to the unlit surroundings. As already mentioned, this strong demarcation serves to avoid dazzling a patient being examined, which is particularly important during dental examinations or treatments. On the opposite underside 202, however, the light emission is preferably slightly widened, so that lower brightness gradients are present here. The light field 200 therefore tapers off more gently towards the underside, reducing the proportion of high brightness contrasts in the entire field of view, for example of a doctor. Since such strong brightness contrasts require an ultimately tiring adaptation of the human eye, this measure enables more pleasant work for the dentist.Apart from these edge regions, however, it is intended to illuminate the light field 200 as homogeneously and uniformly as possible over its entire extent, whereby this should occur essentially independently of the distance from the luminaire 100. This effect is achieved with the aid of the inventive design of the lighting unit, which will be explained in detail below.

[0033] The optical structure of the lighting unit 10 provided inside the luminaire 100 according to a first embodiment is shown in Figure 3The essential components are, first of all, the illuminants 20 in the form of a point-shaped LED light source 21, which is arranged on a corresponding circuit board 22. The LED illuminants 21 form an essentially point-shaped, single light source. This is either a single high-performance LED or a relatively compact LED cluster consisting of several LEDs. In both cases, the LED light source 21 is designed to emit white light with a desired color temperature.

[0034] The optical system 30, which influences the light emitted by the illuminants 20 over a relatively wide angular range, consists of two components: a collimator 40 and a cover plate 50 following the collimator 40—as seen in the light emission direction. In the illustrated embodiment, this cover plate is slightly curved, in particular slightly concavely curved, but could also be flat or designed in another way. Both the collimator 40 and the cover plate 50 are made of a translucent material, in particular a plastic material, which has good light-influencing properties and is resistant to external influences, in particular to moisture and the like.

[0035] According to the invention, the collimator 40, which is formed by a one-piece, essentially plate-shaped component that defines the aforementioned plane E3, is divided into two regions. A first, light-refracting region 42 is provided in the geometric center of the collimator 40 and has light-refracting structures 43 on the side facing away from the LED light source 21. The function of this central region 42 is to convert the corresponding beam into a central light field, which is then emitted via the cover 50.

[0036] An outer region 46 is provided surrounding the central region 42, in which the light is redirected by means of total internal reflection. The corresponding structures 48 are located in this case on the side facing the LED light source 21 and generate a second, outer light field, which is also emitted via the cover 50. The ultimately desired uniform light field 200 is then achieved by superimposing the central and outer light fields. This superimposition is achieved by an expansion structure, described in more detail below, which is located on the side of the cover plate 50 facing the LED light source 21.Because the illuminants 20 and the associated components 40 and 50 of the optical system 30 form a substantially extended, uniformly illuminated surface as a light source, the effect of defocusing the target light field when the optimal imaging distance is left is advantageously achieved. In other words, the optical system 30 is fundamentally designed such that, at a predetermined distance of, for example, 700 mm, an exact superposition between the central and outer light fields is achieved, and accordingly, the target light field is particularly uniformly and homogeneously illuminated. However, if this ideal distance is deviated from, the resulting change in uniform illumination is less pronounced than with prior art luminaires.Essentially, optimal homogeneous illumination of the light field 200 can still be achieved in a range between 500 and 800mm distance.

[0037] The design of the collimator 40 can Figures 4 to 7 As already mentioned, it is essentially a plate-shaped plastic component, which - like the Figures 6 and 7 show - has a substantially square shape and serves to convert the beam of rays emitted by the LED light source 21 over a large angular range into a substantially parallel beam. For this purpose, the surfaces of the collimator 40 have certain light-influencing structures, which will be explained in more detail below.

[0038] Thus, in a central region 42 on the side of the collimator 40 facing away from the LED light source 21, a Fresnel-like structure 43 is provided, which is intended to deflect the light rays leaving the collimator 40 by means of light refraction in such a way that they are aligned essentially parallel to the main optical axis A of the system. Such Fresnel structures are already known and contribute to the fact that, compared to a classic convex lens, the thickness of the corresponding optical component can be reduced. Ultimately, with the help of the Figures 4 and 5 recognizable sawtooth-like structure, which - as in Figure 6 recognizable - has a rotational symmetry around the center or axis A, an extremely efficient bundling of the corresponding light can be achieved.

[0039] Surrounding the central region 42 in a ring-like manner, but now on the side facing the illuminants 20, the collimator 40 further has an outer region 46, which in turn is provided with Fresnel-like structures 48. These are also shown in Figure 7They are designed to be rotationally symmetrical with respect to the main optical axis A and serve to influence the light rays emitted more laterally in such a way that they are in turn aligned parallel to the optical axis A. However, while the Fresnel structures 43 of the central region 42 influence the light rays by means of refraction, the Fresnel structures 48 of the outer region 46 influence the light rays by means of total internal reflection. This means that these sawtooth-like structures are designed in such a way that light rays can initially enter the rib-like projections, but due to the difference in optical density between the collimator 40 and the surrounding air, they are totally reflected in such a way that they leave the collimator 40 in turn on the side facing away from the lighting means 20.The corresponding inclination of the flanks of the totally reflecting structures 48 ensures that the light is aligned parallel to the optical axis A of the system.

[0040] The light influenced in this way by the collimator 40 is then projected through the cover plate 50 onto the actual light field 200, which for this purpose has a lens structure described in more detail below, which ultimately causes the central light field and the outer light field to be superimposed in order to achieve a homogeneous, uniform illumination.

[0041] The interaction of these components, consisting of the compact LED light source 20, the collimator 40 with the light-refracting and totally reflective structures, and the cover plate 50, initially results in the ultimately achieved light field 200 having a large brightness gradient in the edge region, i.e., being strongly demarcated from the surroundings. This is particularly desirable on the upper side, i.e., in the direction of the eyes of a patient being examined, in order to avoid glare. On the opposite side, however, as already mentioned, the light field 200 should have a much blurrier demarcation in order to reduce the operator's fatigue. This means that the light field 200 should ideally have an asymmetry in one direction with a soft fade-out towards the underside.

[0042] To achieve this effect, an additional structuring is provided on the rear side of the collimator 40 opposite the light-refracting structures 43 of the central region 42, i.e. on the side of the collimator 40 facing the illuminants 20. This consists in the Figures 3 to 7 illustrated first embodiment of segment-like individual tiles 45, which - as in Figure 7recognizable - fill the entire central area 42 up to the outer structure 46 in a matrix-like manner. These facet-like tiles 45 now have a slight inclination or tilt in order to achieve the above-mentioned one-sided expansion of the light field. In particular, the tiles 45 are tilted about a horizontal axis (or generally about an axis which lies in the plane of the collimator 40 and is substantially perpendicular to the direction of the asymmetric expansion), i.e., in the case shown, they enclose a small angle with the vertical axis I1 or O1 (see Figure 4 ), so that light beams entering the collimator 40 are slightly widened towards the underside. Even a slight inclination of the tiles 45, as shown in the Figures 4 and 5 can be seen, already leads to the lower edge area of the light field 200 having a somewhat reduced brightness gradient.

[0043] Alternatively or in addition to the just-described tilting of the tiles 45 about an axis perpendicular to the direction of the asymmetric expansion, it would also be conceivable to tilt the lens structure on the cover plate 50 in a corresponding manner to create the desired advantageous effect of asymmetric light field distribution. This will be explained in more detail later.

[0044] Furthermore, however, the tiles 45 can also be tilted along the vertical axis I1 or O1 (or generally about an axis running parallel to the direction of the asymmetric expansion of the light field), in which case they are then preferably arranged symmetrically with respect to the plane E1, which is perpendicular to the plane E3 of the collimator 40 and is spanned by an axis I1 running parallel to the direction of the asymmetric expansion. This influences the horizontal extent of the central light field 200, which ultimately further contributes to the homogeneous illumination of the light field 200.

[0045] This further tilting of the tiles 45 about a vertical axis (or about an axis running parallel to the direction of the asymmetrical widening) and the symmetrical design with respect to the vertical plane E1 leads, overall, to an approximately concave design of the surface of the rear side of the central region 42 of the collimator 40 facing the illuminants 20. The resulting effect of even more homogeneous illumination of the light field 200 can now also be achieved by combining the individual tiles lying at the same height into a larger surface, which then also has a corresponding curvature or arch. A corresponding embodiment of this is shown in the Figures 8 to 13 and will be explained below, whereby comparable elements have been given the same reference numerals.

[0046] Thus, in this second embodiment, the optical system of the luminaire 100 according to the invention also consists of the plate-shaped collimator 40 and the cover plate 50 having the lens structure following the collimator 40. The collimator 40 again has a central region 42, which is provided with light-refracting structures 43 on its side facing away from the LED light source 21. Furthermore, an outer region 46 surrounding the central region 42 is provided with structures 48 designed for total reflection on a side facing the LED light source 21. Both the structures 43 of the central region 42 and the structures 48 of the ring-shaped outer region 46 correspond in terms of their design and function to the structures of the embodiment of the Figures 3 and 7 . Thus, there are no differences with regard to these features compared to the first embodiment.

[0047] The crucial difference between the first embodiment of the Figures 3 to 7 and the second embodiment of the Figures 8 to 13 lies in the design of the rear side of the collimator 40 opposite the light-refracting structures 43 of the central region 42, which in the first embodiment is covered in a matrix-like manner with the tiles 45 already mentioned.

[0048] In the second embodiment, partial surfaces 145 are again provided, which now, however, are in the form of strip-shaped surface areas 145, which, when the lamp is aligned accordingly, Figure 1 each extending horizontally (or generally perpendicular to the direction of the asymmetrical widening) from the left end of the central region 42 to the right end. Again, these strip-shaped surface regions 145 are arranged such that they preferably completely cover the rear side of the central region 42.

[0049] Analogous to the tiles 45, the essential function of the strip-shaped partial surfaces 145 is to achieve the inventive asymmetrical widening of the light field 200, such that a lower brightness contrast occurs on the underside or the side of the light field 200 opposite the patient's eye than on the opposite edge region. In this case, too, the strip-shaped partial surfaces 145 are each tilted about an axis, which lies in the plane E3 of the collimator 40 and is essentially perpendicular to the direction of asymmetrical widening of the light field 200. The corresponding sectional view of the Figure 9 , which is the representation of Figure 4 of the first embodiment, thus shows a comparable inclination of the partial surfaces 145, by which the light rays are influenced in an analogous manner, as described above in connection with the Figures 3 to 7The resulting sawtooth-like structure of the corresponding surface area of the collimator 40 can also be seen in the two perspective partial sectional views of the Figures 10 and 11 be taken.

[0050] In addition, it is provided that the strip-shaped surface areas 145 are concavely curved with respect to the direction of the asymmetric expansion of the light field 200, wherein the direction of the curvature is greatly exaggerated in Figure 11 is schematically represented by the double arrow. The concave configuration of the strip-shaped surface areas 145 is in turn preferably such that a symmetrical configuration results with respect to the plane E1, which is perpendicular to the plane E3 of the collimator 40 and is spanned by an axis I1 running parallel to the direction of the asymmetric widening. In the sectional view of the Figure 9Due to this concave curvature, the rear end regions of the strip-shaped surface regions 145 are each visible.

[0051] The resulting surface design of the back of the central area 42 of the collimator 40 corresponds overall to that of the embodiment of the Figures 3 to 7 , whereby the individual tiles 45 lying at the same height have now been replaced by continuously and steadily extending surface areas 145.

[0052] Compared to the first embodiment of the Figures 3 to 7 represents the second embodiment of the Figures 8 to 13This represents the preferred embodiment, since the edges at the transitions between two adjacent tiles 45 are now eliminated. Such edges generally entail the risk of unwanted, uncontrollable light scattering, so that by designing the surface according to the second embodiment, somewhat better control of the light by the collimator 40 can be achieved.

[0053] The measures described above take into account the fact that the spectrum of the light emitted by the LED light source 21 depends on the radiation angle. In particular, the light emitted in the center or centrally is colder and becomes warmer radially outwards with increasing radiation angle, which is due to the increasing path length of the blue light emitted by the LED chip through the corresponding color conversion material, e.g. through the phosphor. The light of the central light field and that of the outer light field will therefore initially have a different color or color temperature. However, because an overlay of both light fields is ultimately achieved with the help of the cover 50, a homogeneous illumination is achieved overall. For the targeted mixing of the light field orThe fact that the refractive structures 43 of the central collimation structure and the surfaces 48 of the outer collimation structure 46 are designed as aspherical surfaces also contributes to achieving a color-homogeneous light field. Their shape depends on the distance from the center of the optical axis A of the collimator 40; overall, however, both structures exhibit rotational symmetry, as can be seen in the figures.

[0054] The light rays influenced in this way by the collimator 40 are then finally influenced by the cover plate 50, which is designed in the same way for both embodiments of the collimator 40. As already mentioned, the cover plate 50 can be slightly concave or flat and has a lens structure on its side facing the LED light source 21. The side facing away from the lighting means, however, is preferably unstructured, i.e., smooth, and accordingly allows for easy cleaning, which is particularly advantageous when the cover 50 simultaneously forms the outer side of the luminaire 100.

[0055] Just like the collimator 40, the lens structure of the cover plate 50 is also designed in two parts. As in Figure 8As indicated, a first central region 52 with associated first lenses 53 and an outer region 56 with associated second lenses 58 are provided. Both regions of the lens structure correspond to the two regions of the collimator 40. In other words, light rays influenced by the central region 42 of the collimator 40 are to be influenced by the central lens region 52 of the cover, while the light emitted via the outer region 46 of the collimator 40 is influenced by the outer lens structure.

[0056] However, both lens structures 52 and 56 are each designed as a microlens array and serve as an expansion structure to project the corresponding partial light beams onto the area to be illuminated. The height-to-width ratio of the individual lenses defines the value of the horizontal and vertical expansion of the light field 200, whereby these values are slightly different for the central lenses 43 and the outer lenses 58, meaning that both light fields are expanded slightly differently. Ultimately, these measures result in the central light field and outer light field being essentially completely superimposed within the distance of approximately 500 to 800 mm intended for illumination, thus resulting in an overall homogeneously illuminated light field 200.

[0057] Each individual lens of the cover plate 50 projects the entire central or outer light field, so that the shading of individual lenses or parts of the cover plate 50 does not lead to shadows in the light field 200. This also contributes to optimized illumination. In the illustrated embodiment, the lenses of the outer region have a different size and shape compared to the lenses of the central region. In particular, the lenses 53 of the central region 52 are approximately square, whereas the lenses 58 of the outer region have a more rectangular shape. This does not necessarily have to be the case, however. The decisive factor is simply that the individual beams are widened by the lenses in such a way that there is a complete overlap, which leads to uniform illumination largely independent of the distance to the luminaire.The result is a homogeneous target light field that has the desired properties.

[0058] To achieve the asymmetric light field distribution explained above, it is conceivable that, as an alternative or in addition to the inclination of the tiles 45 or the strip-shaped partial surfaces 145, some of the lens structures 52 and / or the lens structures 56, or all of the lenses 53, 58, are tilted relative to the plane E3 of the collimator about an axis that is oriented substantially perpendicular to the direction of the asymmetric expansion. This measure also leads to the advantageous asymmetric expansion of the light field 200 on its underside 202, so that the corresponding inclined orientation of the tiles 45 or strip-shaped partial surfaces 145 could possibly be dispensed with.

[0059] Overall, the lamp according to the invention can be used to achieve high-quality illumination of an area to be examined or treated. The lamp is also characterized by its relatively simple design, which includes only a few individual components and, compared to known solutions, is significantly less critical with regard to the precise alignment and positioning of the individual components relative to one another.

Claims

1. Medical light (100), in particular dental treatment light for the intraoral illumination of an operation field, having an illumination unit (10) having lighting means (20) and optical means (30) for generating a light field (200) in an object plane (O), wherein the lighting means (20) are formed by an essentially punctiform LED light source (21) and the optical means (30) have a plate-shaped collimator (40) and a cover pane (50), wherein the collimator (40) has a central area (42), which is provided with light-refracting structures (43) on a side facing away from the LED light source (21), and an outer area (46), which surrounds the central area (42) and which is provided with structures (48) designed for total reflection on a side facing toward the LED light source (21), wherein the cover pane (50) is provided with a lens structure, which has a plurality of individual lenses each designed to project the light emitted by the collimator (40) and entering the lenses onto the object plane, and wherein the rear side of the central area (42) of the collimator (40) facing toward the LED light source (21) is provided with partial surfaces (45, 145), which have an inclination in relation to a plane (E3) of the collimator (40) and thus in relation to the object plane (O), characterized in that the partial surfaces (45, 145) are designed to asymmetrically expand the light field (200) in one direction.

2. Medical light according to Claim 1, characterized in that at least some of the partial surfaces (45, 145), preferably all of them, are each tilted around an axis which lies in the plane (E3) of the collimator (40) and is essentially perpendicular to the direction of the asymmetrical expansion.

3. Medical light according to Claim 2, characterized in that the partial surfaces (145) are formed strip-shaped and each extend essentially perpendicular to the direction of the asymmetrical expansion along their respective tilt axis.

4. Medical light according to Claim 3, characterized in that the strip-shaped surface areas (145) are concavely curved with respect to the direction of the asymmetrical expansion, wherein the strip-shaped surface areas (145) are preferably each formed symmetrically with respect to a plane (E1), which is perpendicular to the plane (E3) of the collimator (40) and is spanned by an axis (I1) extending parallel to the direction of the asymmetrical expansion.

5. Medical light according to Claim 2, characterized in that the partial surfaces (45) are tile-shaped and cover the rear side of the central area (42) of the collimator (40) facing toward the LED light source (21) like a matrix.

6. Medical light according to Claim 5, characterized in that at least some of the tile-shaped partial surfaces (45) are tilted with respect to the plane (E3) of the collimator (40) around an axis which extends parallel to the direction of the asymmetrical expansion.

7. Medical light according to Claim 6, characterized in that the majority of the tile-shaped partial surfaces (45) are arranged symmetrically with respect to a plane (E1), which is perpendicular to the plane (E3) of the collimator (40) and is spanned by an axis (I1) extending parallel to the direction of the asymmetrical expansion.

8. Medical light according to any one of the preceding claims, characterized in that the light-refracting structures (43) of the central area (42) of the collimator (40) form a Fresnel structure.

9. Medical light according to Claim 8, characterized in that the structures (48) of the collimator (40) designed for total reflection form a further Fresnel structure facing toward the LED light source (21), which preferably encloses the central area (42) like a ring in a projection perpendicular to the plane (E3) of the collimator (40).

10. Medical light according to Claim 8 and Claim 9, characterized in that the light-refracting structures (43) and the structures (48) of the collimator (40) designed for total reflection have a common rotational symmetry.

11. Medical light according to any one of Claims 8 to 10, characterized in that the light-refracting structures (43) and the structures (48) of the collimator (40) designed for total reflection have aspheric surface areas.

12. Medical light according to any one of the preceding claims, characterized in that the optical means (30) are constructed such that the light field (200), which is projected perpendicular to the optical axis (A) of the light (100) on the object plane (O), has a greater expansion along an axis (O2) extending perpendicular to the direction of the asymmetrical expansion than along an axis (O1) extending parallel to the direction of the asymmetrical expansion.

13. Medical light according to any one of the preceding claims, characterized in that at least some of the lenses (53, 58) forming the lens structure are tilted with respect to the plane (E3) of the collimator around an axis which is aligned essentially perpendicular to the direction of the asymmetrical expansion.

14. Medical light according to any one of the preceding claims, characterized in that the lenses (53, 58) are arranged on a side of the cover pane (50) facing toward the LED light source (21), wherein preferably the side of the cover pane (50) facing away from the LED light source (21) is formed smooth, in particular forms a smooth outer surface of the light (100).

15. Medical light according to any one of the preceding claims, characterized in that the lens structure of the cover pane (50) has an inner area (52) and an outer area (56), wherein • lenses (53) of the inner area (52) are designed to project the light emitted by the central area (42) of the collimator (40) in the form of a central light field on the object plane (O) and • lenses (58) of the outer area (56) are designed to project the light emitted by the outer area (46) of the collimator (40) in the form of an outer light field on the object plane (O), and wherein central light field and outer light field are essentially completely superimposed, wherein preferably each individual lens (53, 58) of the inner or outer area (52, 56) completely projects the corresponding central or outer light field, respectively.

16. Medical light according to Claim 15, characterized in that the lenses (53) of the inner area (52) are essentially square and the lenses (58) of the outer area (56) have a greater extension in the direction of an axis (I2) of the collimator (40), which extends perpendicular to the direction of the asymmetrical expansion, than in an axis (I1) of the collimator (40) extending parallel to the direction of the asymmetrical expansion.