ILLUMINATION DEVICE, IN PARTICULAR AN ILLUMINATION DEVICE FOR A MOTOR VEHICLE

Abstract

An illumination device, in particular an illumination device for a motor vehicle, comprising a light source for generating light which has components in a blue, green, and red wavelength range, and a holographic optic which the light emitted by the light source strikes, wherein the light striking the holographic optics is used at least partially for reconstructing a hologram, wherein the light emerges from the illumination device after interaction with the holographic optic, and wherein the light source is designed so that the spectral distribution of the light emitted by the light source is adapted to the spectral diffraction efficiency of the holographic optics.

Claims

1. An illumination device for a motor vehicle, the illumnination device comprising: a light source for generating light which has components in a blue, green, and red wavelength range; and a holographic optic which the light emitted by the light source strikes, wherein the light striking the holographic optic is used at least partially for reconstructing a hologram, and wherein the light emerges from the illumination device after interaction with the holographic optic, wherein the light source is configured so that the spectral distribution of the light emitted by the light source is adapted to the spectral diffraction efficiency of the holographic optic.

2. The illumination device according to claim 1, wherein the light source comprises at least one light-emitting diode or at least one laser diode as well as a converter which at least partially changes the spectral distribution of the light emitted by the light source when the illumination device is in operation, and/or in wherein the light source is designed as an RGB light source and comprises a plurality of light-emitting diodes or a plurality of laser diodes of different wavelengths.

3. The illumination device according to claim 1, wherein the illumination device is designed so that the color point of the spectrum of the light emerging from the illumination device lies in the ECE white area.

4. The illumination device according to claim 1, wherein the illumination device is designed so that the color point of the spectrum of the light emitted by the light source does not lie in the ECE white area before the interaction with the holographic optic.

5. The illumination device according to claim 1, wherein the hologram was written in the holographic optic with three different types of laser light which had wavelengths different from one another, in particular with blue, green, and red laser light, for example, with blue laser light with a wavelength of about 450 nm, with green laser light with a wavelength of about 534 nm, and with red laser light with a wavelength of about 638 nm.

6. The illumination device according to claim 1, wherein the spectral diffraction efficiency of the holographic optic has local peaks in three spaced-apart wavelength ranges, or wherein an effective diffraction of the light striking the holographic optic takes place in a range of about ±15 nm around the local peaks.

7. The illumination device according to claim 6, wherein the local peaks of the diffraction efficiency of the holographic optic are located in a blue, green, and red wavelength range, in particular at about 450 nm, at about 534 nm, and at about 638 nm.

8. The illumination device according to claim 1, wherein the spectral distribution of the light emitted by the light source has a local peak in a blue and/or in a green and/or a red spectral range.

9. The illumination device according to claim 8, wherein the local peak of the spectral distribution of the light emitted by the light source, the peak located in the blue spectral range, has such a half width that the local peak of the spectral diffraction efficiency of the holographic optic, the peak located in the blue wavelength range, is within this half width, in particular wherein the intensity of the light emitted by the light source at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, the peak located in the blue wavelength range, is more than 60%, preferably more than 80% of the intensity of the local peak of the spectral distribution of the light emitted by the light source, said peak located in the blue spectral range.

10. The illumination device according to claim 8, wherein the local peak of the spectral distribution of the light emitted by the light source, said peak located in the green spectral range, has such a half width that the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the green wavelength range, is within this half width, in particular wherein the intensity of the light emitted by the light source at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the green wavelength range, is more than 60%, preferably more than 80% of the intensity of the local peak of the spectral distribution of the light emitted by the light source, said peak located in the green spectral range.

11. The illumination device according to claim 8, wherein the local peak of the spectral distribution of the light emitted by the light source, said peak located in the red spectral range, has such a half width that the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the red wavelength range, is within this half width, in particular wherein the intensity of the light emitted by the light source at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the red wavelength range, is more than 60%, preferably more than 80% of the intensity of the local peak of the spectral distribution of the light emitted by the light source, said peak located in the red spectral range.

12. The illumination device according to claim 1, wherein an intensity of the light emitted by the light source in a red spectral range is more than 50%, in particular more than 75%, preferably more than 85% of the intensity of the light in a green spectral range.

13. The illumination device according to claim 12, wherein the intensity of the light emitted by the light source at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the red wavelength range, is more than 50%, in particular more than 75%, preferably more than 85% of the intensity of the light at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the green wavelength range.

14. The illumination device according to claim 1, wherein an intensity of the light emitted by the light source in a red spectral range is more than 40%, in particular more than 50% of the intensity of the light in a blue spectral range.

15. The illumination device according to claim 14, wherein the intensity of the light emitted by the light source at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the red wavelength range, is more than 40%, in particular more than 50% of the intensity of the light at the wavelength of the local peak of the spectral diffraction efficiency of the holographic optic, said peak located in the blue wavelength range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0021] FIG. 1 shows a diagram in which the spectral distribution of the light emitted by a light source of a first embodiment of an illumination device of the invention, the spectral diffraction efficiency of a holographic optic, and the spectral distribution of a laser beam used to write the hologram of the holographic optic are illustrated, wherein the distributions and the diffraction efficiency are plotted in arbitrary units against the wavelength in nm;

[0022] FIG. 2 shows a diagram in which the spectral distribution of the light emitted by a light source of a second embodiment of an illumination device of the invention, the spectral diffraction efficiency of a holographic optic, and the spectral distribution of a laser beam used to write the hologram of the holographic optic are illustrated, wherein the distributions and the diffraction efficiency are plotted in arbitrary units against the wavelength in nm;

[0023] FIG. 3 shows a diagram in which the spectral distribution of the light emitted by a common white light light-emitting diode, the spectral diffraction efficiency of a holographic optic, and the spectral distribution of a laser beam used to write the hologram of the holographic optic are illustrated, wherein the distributions and the diffraction efficiency are plotted in arbitrary units against the wavelength in nm.

DETAILED DESCRIPTION

[0024] FIG. 1 shows the spectral distribution 1 of the light emitted by a light source of a first embodiment of an illumination device of the invention. The light source can be, for example, a blue light-emitting diode with a suitable converter. Because of the blue light-emitting diode, distribution 1 has a local peak 7 in the blue spectral range. In contrast to the white light light-emitting diode shown in FIG. 3, the wavelength of the blue light-emitting diode and the converter material are selected so that spectral distribution 1 is better adapted to spectral diffraction efficiency 2 of the holographic optic.

[0025] The holographic optic can comprise, for example, a film or a stack of films in which one or each hologram is written. The hologram can be a reflection hologram or a transmission hologram or an edge-lit hologram.

[0026] It becomes apparent that spectral distribution 1 of the light emitted by the light source has, in addition to the local peak 7 in the blue region, distinct local peaks 9, 10 in the green and red regions. Local peak 7 overlaps more strongly with local peak 3 of spectral diffraction efficiency 2 than in the case of the white light light-emitting diode shown in FIG. 3. Furthermore, local peaks 9, 10 are located substantially in the region of the green and red wavelengths of local peaks 4, 5 of spectral diffraction efficiency 2, so that an effective diffraction of the light, emitted by the light source, takes place in these regions as well.

[0027] FIG. 2 shows spectral distribution 1 of the light emitted by a light source of a second embodiment of an illumination device of the invention. The light source can be, for example, a blue light-emitting diode with a converter different from the embodiment according to FIG. 1. The light source can, however, also be an RGB light source or a combination of an RGB light source with a converter.

[0028] It becomes apparent that in this exemplary embodiment, spectral distribution 1 of the light emitted by the light source has, in addition to the local peak 7 in the blue region, more distinct local peaks 9, 10 in the green and red regions. Local peak 7 overlaps similarly strongly with local peak 3 of spectral diffraction efficiency 2 as in the embodiment according to FIG. 1. However, local peaks 9, 10 in the embodiment according to FIG. 2 are relatively narrow and are located almost exclusively in the region of the green and red wavelengths of local peaks 4, 5 of spectral diffraction efficiency 2.

[0029] As a result, in the embodiment according to FIG. 2, an even higher efficiency can be achieved because almost all of the spectral components of the light emitted by the light source can be used for diffraction on the hologram.

[0030] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.