The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "An illumination unit is known from International Patent Publication No. WO 2008/017968 A2, which discloses an illumination unit containing a semiconductor light source, a primary optical system and a secondary optical system. The primary optical system guides the light from the semiconductor light source onto the secondary optical system. The secondary optical system emits the light in a desired beam pattern. Owing to the geometrically narrowly delimited area of the light source, only a small quantity of light is introduced into the illumination unit via the primary optical system. Consequently, an illumination unit of this type achieves a low axial light intensity."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The present invention addresses the problem of providing an illumination unit comprising a surface light source in which the axial light intensity customary from a conventional reflector halogen incandescent lamp is achieved with at the same time a narrow emission angle.
"Various embodiments of the illumination unit comprise a surface light source, a primary optical element, a first reflector and a second reflector. The primary optical element is arranged at a surface light source in such a way that light emitted by the surface light source is imaged onto the first reflector by the primary optical element, the beam cross section of the light being reduced by the primary optical element at the same time. The first reflector images the light beam that has been reduced by means of the primary optical element onto the second reflector in order to emit the light from the second reflector from the illumination unit.
"The primary optical element that reduces the beam cross section makes it possible to use a surface light source having larger dimensions, for example, a large-area light-emitting diode (LED) module. Such surface light sources having large dimensions emit a multiple luminous flux compared with a customary LED or with an LED module having small dimensions. Through geometrical adaptation of the surface light source, it is thus possible to obtain a luminous flux comparable with a conventional light source such as, e.g., a halogen incandescent lamp.
"A luminous flux is directed onto the reflector arrangement via the primary optical element. The reflector arrangement comprises a first and a second reflector. The luminous flux is emitted from the illumination unit via the reflector arrangement, as a result of which the axial light intensity customary from a conventional illumination unit is achieved.
"Some embodiments of the illumination unit contain, as the surface light source, a light-emitting semiconductor component or a module having a plurality of light-emitting semiconductor components. Such semiconductor components can be, for example, light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs) or else laser diodes (LDs). Organic light-emitting electrochemical cells (OLEECs) would also be suitable as the surface light source.
"The light-emitting semiconductor components can emit in each case single-colored light (for example, in the colors red, green, blue, etc.), or mixed light (for example, white). A plurality of light-emitting semiconductor components can generate mixed light; e.g., white mixed light.
"As the temperature increases, a light-emitting semiconductor component loses efficiency and degrades earlier. Good dissipation of heat from the light-emitting semiconductor components is therefore sought. Besides cooling devices, the local temperature distribution at the semiconductor component plays an important part. The use of a surface light source having large dimensions proves to be advantageous. This is because the luminous flux required for the illumination unit is generated on a larger area. The heat that arises in this case is distributed over a larger area, as a result of which the individual semiconductor components are subjected to lower thermal loading and degrade more slowly.
"In one embodiment, the surface light source is fitted outside the reflector arrangement. In this case, the surface light source has larger dimensions than or the same dimensions as an opening in the vertex region of the second reflector. Through said opening, the light from the surface light source is guided into the reflector arrangement by means of the primary optical element, thereby enabling a high luminous flux to be coupled into the reflector arrangement with at the same time good dissipation of heat from the surface light source.
"In a further embodiment, the surface light source is a directional light source. In this case, the majority of the emitted light is emitted in a preferred direction, for example, perpendicular to the surface light source. In order that the light emitted by the surface light source is coupled into the primary optical element in a manner as free of losses as possible, the emission angle of the directional surface light source is limited to 80.degree. FWHM. In this case, the emission angle is indicated with the full width at half maximum (FWHM).
"The semiconductor components can contain optical elements which concentrate the light in the emission direction. Such optical elements can be attachment lenses. Alternatively, the semiconductor components themselves can contain curved surfaces which concentrate the emitted light in the preferred direction.
"Various embodiments contain a primary optical element having a conical element as light concentrator. The conical element can be a conical optical waveguide, for example, the light entrance area of which is greater than the light exit area thereof. The area ratio of entrance area to exit area should be at least 2:1, better still at least 9:1. The conical optical waveguide can be a hollow body having a conical lateral surface. One element that is technically easy to realize is a conical metal ring. Ideally, the inner side of the conical lateral surface is reflectively fashioned or provided with a reflective coating.
"Alternatively, the conical optical waveguide can consist of a transparent material such as glass or Plexiglas. In addition, the light entrance area of the conical optical waveguide can contain cutouts into which the light-emitting semiconductor components of the surface light source project. These depressions enable the light emitted by the surface light source to be coupled into the primary optical element with low losses.
"In further embodiments, the primary optical element contains a linear optical waveguide, which is adjacent to the exit opening of the conical element. The linear optical waveguide can be, for example, a cylindrical glass rod or cylindrical Plexiglas rod. The linear optical waveguide can alternatively consist of a metal tube, the inner side of which is reflectively fashioned or provided with a reflective layer. The optical waveguide guides the light concentrated by the conical element in the direction of the first reflector.
"In some embodiments, the first reflector is situated in an extension of the optical axis and conceals the exit area of the primary optical element. The optical axis is perpendicular to the surface light source and extends axially symmetrically through the illumination unit. The light emitted by the primary optical element is directed back onto the second reflector by the first reflector. The second reflector deflects the light beam from the illumination unit near the axis. Lateral emission from the illumination unit is suppressed, whereby glare perpendicular to the optical axis is avoided.
"In some embodiments, an axicon-shaped mirror is used as the first reflector. An axicon-shaped minor is a rotationally symmetrical minor having a conically extending mirror surface which images a circular light point into a circular light ring. The axicon-shaped mirror completely deflects the light beam emitted by the primary optical element onto the second reflector.
"In some embodiments, the second reflector is a parabolic minor, the vertex region of which contains an opening, through which the primary optical element projects into the illumination unit. The beams reflected by the axicon-shaped mirror form an annular light distribution corresponding to the dimensioning of the second reflector. Light losses owing to lateral emission are avoided. Lateral emission would mean light beams which led past within the inner annulus or outside the outer annulus of the second reflector. Ideally, the area of the second reflector is illuminated homogeneously by the reflection at the axicon-shaped mirror.
"The second reflector generates in the plane of the first reflector an annular light distribution, the internal diameter of which is greater than or equal to the diameter of the first reflector. The light beams are guided past at the first reflector without light losses owing to shading at the first reflector. By means of geometrical adaptation of the first reflector and second reflector, it is thus possible to achieve a light distribution near the axis without shading losses. The emission angle of the illumination unit is less than 10.degree. FWHM.
"If the surface light source contains multicolored LEDs, the lateral surface of the primary optical element or the surface of the second reflector can be faceted for the purpose of color homogenization. The facet dimensions of the second reflector are not greater than the light-emitting area of the individual LEDs.
"In further embodiments, the illumination unit comprises a transparent cover, which encloses the reflector arrangement. The transparent cover protects the illumination unit against ingress of dust or dirt and prevents corrosion of the optical components. The transparent cover can be fixed to the second reflector, for example, by a thread or a snap-action device.
"In one embodiment, the first reflector is fixed to the transparent cover, such that the first reflector is connected to the second reflector via the transparent cover. This embodiment obviates mechanical components which hold the first reflector in defined positions with respect to the primary optical element and the second reflector. This precludes light losses owing to shading at the mechanical components which otherwise lie in the beam path of the reflector arrangement.
"The transparent cover can contain a light-scattering structure having a scattering angle range of preferably 2.degree. to 4.degree. FWHM. A light distribution that is more homogenous in the far field is obtained as a result. In this case, the transparent cover can comprise a material having a light-scattering structure. Alternatively, the transparent cover can also comprise a material having high optical transparency such as glass or Plexiglas, for example, wherein a surface contains a light-scattering structure.
"In a further embodiment, the transparent cover contains a color-mixing structure, as a result of which, in particular, a better color homogeneity in the far field is achieved. This has an advantageous effect in particular in terms of the color homogeneity if the surface light source contains light-emitting diodes with multicolored emission or light-emitting diodes with different-colored mixed light such as warm-white or cold-white, for example.
BRIEF DESCRIPTION OF THE DRAWINGS
"Various exemplary embodiments of the illumination unit are explained in greater detail below with reference to the drawings. In the figures, the first digit(s) of a reference sign indicate the figure in which the reference sign is first used. Identical reference signs are used for elements and/or properties that are of identical type or act identically in all the figures.
"FIG. 1 shows a schematic cross-sectional illustration through a first exemplary embodiment of an illumination unit;
"FIG. 2 shows a schematic cross-sectional illustration of the primary optical element;
"FIG. 3 shows a further schematic cross-sectional illustration of the primary optical element;
"FIG. 4 shows a schematic cross-sectional illustration of the reflector arrangement; and
"FIG. 5 shows a schematic cross-sectional illustration through a second exemplary embodiment of an illumination unit with a transparent cover."
For additional information on this patent application, see: Weiss, Herbert; Kudaev, Sergey; Frunder, Tobias. Illumination Unit with Optical System. Filed
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