Patent Number: 
Section: claims

1. An illumination device comprising a radiation sourcehaving at least one light-emitting diode;a control unit; anda radiation receiving unit;wherein the radiation receiving unit is provided, during operation of the illumination device for receiving both a radiation emitted by the radiation source and a reference radiation and for generating a measurement signal upon receiving the radiation from the radiation source and a reference signal upon receiving the reference radiation, andwherein an operating point for the radiation source is tunable by means of the control unit in a manner concurrently dependent on the measurement signal and the reference signal,wherein the measurement of the reference signal and the measurement signal take place at the same time. 2. The illumination device as claimed in claim 1, wherein a color locus of the radiation from the radiation source is tunable by means of the control unit. 3. The illumination device as claimed in claim 2, wherein the color locus of the radiation from the radiation source is different from a color locus of the reference radiation in a targeted manner. 4. The illumination device as claimed in claim 2, wherein the color locus of the radiation from the radiation source corresponds to a color locus of the reference radiation. 5. The illumination device as claimed in claim 1, which comprises an electrically operable reference radiation source provided for generating the reference radiation. 6. The illumination device as claimed in claim 5, wherein the reference radiation source is nominally provided for operation with a rated power and the reference radiation source is operable below the rated power. 7. The illumination device as claimed in claim 1, which has a radiation exit surface. 8. The illumination device as claimed in claim 7, wherein the reference radiation source is arranged outside an optical beam path from the radiation source to the radiation exit surface. 9. The illumination device as claimed in claim 8, wherein the reference radiation source comprises an incandescent lamp or a gas discharge lamp. 10. The illumination device as claimed in claim 8, wherein the reference radiation source comprises an optoelectronic semiconductor component. 11. The illumination device as claimed in claim 1, wherein the illumination device comprises a phosphorescent material provided for generating the reference radiation. 12. The illumination device as claimed in claim 11, wherein the phosphorescent material is excited during operation of the illumination device and the reference radiation is generated by means of the persistence of the phosphorescent material. 13. The illumination device as claimed in claim 11, wherein the phosphorescent material is arranged and formed in such a way that it can be optically excited by means of the radiation source. 14. The illumination device as claimed in claim 11, wherein the phosphorescent material is arranged and formed in such a way that it can be excited independently of the radiation source. 15. The illumination device as claimed in claim 5, wherein the illumination device comprises a phosphorescent material which is provided for generating the reference radiation and which can be optically excited by means of the reference radiation source. 16. The illumination device as claimed in claim 11, wherein the phosphorescent material is integrated into the radiation source. 17. The illumination device as claimed in claim 11, wherein the phosphorescent material is formed separately from the radiation source. 18. The illumination device as claimed in claim 7, wherein radiation emitted by the radiation source is directed through the radiation exit surface at least partly by means of a reflective surface. 19. The illumination device as claimed in claim 18, wherein the reflective surface is embodied such that it is partly transparent to radiation emitted by the radiation source. 20. The illumination device as claimed in claim 18, wherein the radiation receiving unit is arranged on that side of the reflective surface which is remote from the radiation exit surface. 21. The illumination device as claimed in claim 1, wherein the radiation receiving unit comprises a radiation receiver which is sensitive over the visible spectral range. 22. The illumination device as claimed in claim 1, wherein the radiation receiving unit comprises a respective radiation receiver for at least two mutually different spectral ranges. 23. The illumination device as claimed in claim 22, wherein the radiation receiving unit is formed by means of radiation receivers formed in discrete fashion. 24. The illumination device as claimed in claim 22, wherein the radiation receiving unit is formed by means of radiation receivers formed in monolithically integrated fashion. 25. A method for adapting an emission characteristic of an illumination device to a predetermined emission characteristic, comprising the following steps:a) receiving a radiation from a radiation source of the illumination device by means of a radiation receiving unit and generating a measurement signal;b) feeding the measurement signal to a control unit;c) receiving a reference radiation by means of the radiation receiving unit and generating a reference signal;d) feeding the reference signal to the control unit; ande) setting an operating point for the radiation source by means of the control unit in a manner concurrently dependent on the measurement signal and the reference signal, wherein the measurement of the reference signal and the measurement signal take place at the same time. 26. The method as claimed in claim 25, wherein a sensitivity of the radiation receiving unit is calibrated by means of the reference radiation. 27. The method as claimed in claim 25, wherein a change in the sensitivity of the radiation receiving unit on account of at least one of aging of the radiation receiving unit or a change in temperature of the radiation receiving unit is monitored by means of the reference radiation. 28. The method as claimed in claim 25, wherein the color locus of the radiation generated by the radiation source is determined by means of the radiation receiving unit. 29. The method as claimed in claim 25, wherein the radiation source comprises at least two radiation emitters which are driven separately by the control unit. 30. The method as claimed in claim 29, wherein the radiation emitters emit radiation in mutually different spectral ranges. 31. The method as claimed in claim 29, wherein the radiation emitters are operated simultaneously for determining the color locus of the radiation source. 32. The method as claimed in claim 29, wherein the radiation emitters are operated successively for determining the color locus of the radiation source. 33. The method as claimed in claim 25, wherein the operating point for the radiation source is determined from the measurement signal and the reference signal by means of an arithmetic operation. 34. The method as claimed in claim 25, wherein the operating point is set by means of the control unit in such a way that a change in the emission characteristic that is induced by a change in temperature of the radiation source is at least partly compensated for. 35. The method as claimed in claim 25, wherein the operating point is set by means of the control unit in such a way that a change in the emission characteristic that is induced by aging of the radiation source is at least partly compensated for. 36. The method as claimed in claim 25, wherein the reference radiation is generated by means of a phosphorescent material. 37. The method as claimed in claim 36, wherein the phosphorescent material is excited and the reference radiation is generated by means of a persistence of the phosphorescent material. 38. The method as claimed in claim 36, wherein the phosphorescent material is optically excited. 39. The method as claimed in claim 36, wherein the phosphorescent material is excited by the radiation source. 40. The method as claimed in claim 29, wherein the reference signal is generated while the radiation source is switched off. 41. The method as claimed in claim 25, wherein the reference radiation is generated in such a way that an aging-dictated alteration of the emission properties of the reference radiation is smaller than aging-dictated alteration of the emission properties of the radiation source. 42. The method as claimed in claim 25, wherein the illumination device comprises a reference radiation source which is operated electrically. 43. The method as claimed in claim 42, wherein the reference radiation source is nominally provided for operation with a rated power and the reference radiation source is operated below the rated power. 44. The method as claimed in claim 42, wherein the reference radiation source is operated for a shorter time than the radiation source during operation of the illumination device. 45. The method as claimed in claim 36, wherein the illumination device comprises a reference radiation source which is operated electrically and wherein the phosphorescent material is excited by the reference radiation source. 46. The method as claimed in claim 25, wherein the measurement signal and/or the reference signal are stored in the control unit. 47. The method as claimed in claim 25, wherein the illumination devicecomprises a radiation source having at least one light-emitting diode;a control unit; anda radiation receiving unit;wherein the radiation receiving unit is provided, during operation of the illumination device for receiving both a radiation emitted by the radiation source and a reference radiation and for generating a measurement signal upon receiving the radiation from the radiation source and a reference signal upon receiving the reference radiation, andwherein an operating point for the radiation source is tunable by means of the control unit in a manner concurrently dependent on the measurement signal and the reference signal.