Lamp

Abstract

The invention relates to a lamp (1) comprising a light source (2) that can be excited by microwaves to provide illumination and a housing (4) surrounding the light source, said housing having at least one light exit opening (5). The light exit opening (5) has associated therewith a grille structure (6) or a labyrinth structure (7) acting as a microwave shield.

Claims

1. A lamp comprising a light source that can be excited by microwaves to provide illumination and a housing surrounding the light source, said housing having at least one light exit opening, characterized in that the light exit opening has associated therewith a labyrinth structure acting as a microwave shield, said labyrinth structure being configured as a labyrinth panel comprising a plurality of labyrinth passages which extend at an oblique angle relative to the light exit direction, wherein light beams emitted by the light source travel through a housing interior, the labyrinth structure, and the light exit opening, wherein the plurality of labyrinth passages has a length that varies between the housing interior and the light exit opening.

2. The lamp according to claim 1, characterized in that the labyrinth structure is arranged in the housing interior in front of a light-transparent cover, when seen in the light exit direction, said light-transparent cover being in particular a glass or quartz plate.

3. The lamp according to claim 1, characterized in that the microwave shield is configured as an edge filter or a blocking filter.

4. The lamp according to claim 1, wherein the length of the plurality of labyrinth passages varies by increasing from a middle central axis in an outward direction toward the light exit opening.

5. The lamp according to claim 1, wherein the plurality of labyrinth passages has a middle central axis, wherein the middle central axis is an axis of symmetry for the plurality of labyrinth passages.

6. The lamp according to claim 1, characterized in that the light source has associated therewith a light reflection unit for deflecting light beams, which are emitted by said light source, substantially in the direction of the light exit opening.

7. The lamp according to claim 1, characterized in that the labyrinth panel is arranged on a back of the light-transparent cover, said back facing the light source.

8. The lamp according to claim 1, characterized in that the labyrinth panel is arranged such that it is exchangeable.

9. The lamp according to claim 1, wherein the plurality of labyrinth passages comprise at least one wall, wherein the at least one wall comprises a reflective material.

10. The lamp according to claim 9, wherein the plurality of labyrinth passages comprise at least one wall, wherein the at least one wall comprises metal.

11. The lamp according to claim 1, wherein the plurality of labyrinth passages comprise at least one wall, wherein the at least one wall has a diameter that substantially prevents passage of microwave radiation therethrough.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, advantageous embodiments of the present invention are explained in more detail making reference to the figures added in the drawing, in which:

(2) FIG. 1 shows a longitudinal section through an embodiment of a lamp according to the present invention;

(3) FIG. 2 shows a front view of a grille panel as a grille structure;

(4) FIG. 3 shows a view at an oblique angle of the grille structure according to FIG. 2;

(5) FIG. 4 shows a longitudinal section, analogously to FIG. 1, through a second embodiment of the present invention;

(6) FIG. 5 shows a front view of a labyrinth panel as a labyrinth structure, and

(7) FIG. 6 shows a view at an oblique angle of the labyrinth structure according to FIG. 5.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(8) FIG. 1 shows a longitudinal section through a first embodiment of a lamp 1 according to the present invention. This lamp 1 comprises a lamp housing 4, which is in principle rectangular in shape. Said lamp housing is only shown exemplarily and other shapes thereof are imaginable as well. The interior 8 of the housing has arranged therein a microwave generator 3 configured as a magnetron. This microwave generator feeds microwave energy to respective antennas arranged within the light source 2 comprising a suitable quartz bulb or the like. Between the antennas, a plasma is produced from a suitable inert gas by means of the microwave radiation, said plasma causing a metal halide salt applied to the glass or quartz bulb to evaporate and light in a respective spectral range being generated from the inert gas plasma and the metal halide salt vapor.

(9) The light source 2 is partially surrounded by a light reflection unit 18 configured e.g. as a parabolic mirror. By means of this parabolic mirror, light emitted by the light source 2 is directed towards a light exit opening 5 of the lamp housing 4. The lamp housing 4 normally consists of a metal constituting a shield against the microwave radiation. The light exit opening 5 has associated therewith a grille structure 6 defining a suitable microwave shield in the area of the light exit opening. The grille structure 6 is arranged on a back 19 of a light-transparent cover 9 configured as a glass or quartz plate 10. The light-transparent cover 9 and the grille structure 6 are arranged in a releasable end section 22 of the lamp housing 4. The grille structure 6 is arranged in front of the light-transparent cover 9, when seen in the light exit direction 20, i.e. on the back 19 of said light-transparent cover 9 facing the light source 2.

(10) The light exit opening is fully covered by the light-transparent cover 9, the respective grille structure 6 having analogous dimensions.

(11) Furthermore, two light beams 21 are exemplarily shown in FIG. 1, said light beams corresponding substantially to the maximum exit angle of light radiation from the light exit opening 5 of the lamp housing 4.

(12) The grille structure 6 is configured as a grille panel 11 comprising a plurality of holes 12. As can also be seen in FIGS. 2 and 3, these holes are arranged in rows and columns and have identical shapes and identical diameters.

(13) The diameter of the respective holes 12 is much smaller in comparison with the wavelength of the microwave radiation, a microwave radiation suitable for use being e.g. a 2.45 GHz radiation having a wavelength of approx. 12 cm. The respective holes 12 obstruct exiting of the light beams 21 only to a minor extent, whereas the grille structure 6 defines a reliable microwave shield for the microwave radiation.

(14) The grille panel 11 consists of a low-cost perforated metal plate, which is easy to produce and which can easily be adapted to respective sizes of the light exit opening and of the light-transparent cover 9. Like the labyrinth panels 13 referred to hereinbelow, this kind of grille panels 11 can be produced not only in the substantially square shape according to FIGS. 2, 3, 5 and 6, but also in the shape of almost any light exit opening with a suitable light-transparent cover 9.

(15) FIGS. 2 and 3 show the grille structure 6 in the form of the grille panel 11 in a front view and at an oblique angle from the front. What can especially be seen is the arrangement of the respective holes 12 in columns and rows. In the edge area, said holes 12 may also be formed only incompletely, cf. in FIG. 2 the holes along the upper and lower edges of the grille panel 11.

(16) FIG. 3 shows the grille panel according to FIG. 2 at an oblique angle from the front. Also in this case the arrangement in columns and rows as well as the incomplete formation of holes 12 along upper edges of the respective grille panel can be seen.

(17) FIG. 4 shows a second embodiment of a lamp 1 according to the present invention. For the sake of simplicity, the microwave generator 3 is here not shown. The structural design of the lamp 1 corresponds to that of FIG. 1, the only difference being that a labyrinth structure 7 instead of the grille structure 6 is used as a microwave shield. As regards the further description of the lamp 1 according to FIG. 4, the description according to FIG. 1 is referred to.

(18) In FIG. 4 a plurality of light beams 21 are shown, which pass through the labyrinth structure 7 in the form of a labyrinth panel 13. In order to allow this, the labyrinth panel 13 has a plurality of labyrinth passages 14. These labyrinth passages 14 extend outwards at an oblique angle relative to the light exit direction 20. Also the labyrinth panel 13 is arranged on the respective back 19 of the light-transparent cover 9 covering the light exit opening 5 of the lamp housing.

(19) The respective labyrinth passages 14 have an approximately rectangular cross-section on the exit side of the labyrinth panel 13, cf. FIG. 5, while extending in the direction of the light source 2 at an oblique angle inwards towards a central axis 15. The length of the respective labyrinth passages 14 increases from the central axis 15 in an outward direction, cf. the exemplarily shown length 16 in FIG. 4. Furthermore, the labyrinth panel 13 provided with the respective labyrinth passages 14 is configured symmetrically with respect to a horizontal plane extending through the central axis 15 as an axis of symmetry 17, cf. FIGS. 4 to 6. This means that, in the upper area of the labyrinth panel 13 according to FIG. 4, the labyrinth passages 14 extend at an oblique angle upwards in the direction of the light exit opening 5, and that the corresponding labyrinth passages 14 in the lower part of the labyrinth panel 13 extend at an oblique angle downwards in the direction of the light exit opening 5.

(20) The respective inner sides of the labyrinth passages 14 may be configured such that they reflect light beams so that the exiting of the light beams 21 from the light exit opening 5 will not be impeded to a substantial extent by said labyrinth passages. The size and the shape of the labyrinth passages 14 and in particular of the entrance openings thereof, which face the light source 2, are substantially analogous to the size and diameter of the holes 12 according to FIGS. 1 to 3.

(21) FIGS. 5 and 6 show, in analogy with FIGS. 2 and 3, a front view and a perspective view at an oblique angle from the front showing the respective labyrinth panel 13. The labyrinth passages 14 are arranged in rows and columns directly adjacent to one another. The respective labyrinth panel 13 with its labyrinth passages 14 also consists of a metal having suitable microwave shielding characteristics.

(22) According to the present invention, a reliable, simple and cost-efficient microwave shielding is obtained by means of the grille structure 6 or the labyrinth structure 7 associated directly with the light exit opening and the light-transparent cover 9 of said light exit opening 5, respectively. The respective openings provided in these structures are sufficiently small in size for preventing exiting of the microwave radiation. Whereas the perforated grille panel 11 also defines a blocking filter, the respective labyrinth panel 13 may also be regarded as a resonance seal. This means that the respective labyrinth passages define substantially rectangular waveguides, which are sufficiently small in comparison with the wavelength of the microwave radiation for preventing wave propagation along the labyrinth passages. A respective cutoff wavelength A is obtained e.g. according to the relationship λ.sub.c=2×a, where a is the longer side of the waveguide cross-section, cf. in this respect e.g. FIG. 5.

(23) The respective cutoff wavelength should be sufficiently small in comparison with the wavelength of the microwave radiation to be shielded off.

(24) In addition, it is possible to exchange the respective structures, cf. the grille structure 6 and the labyrinth structure 7, among one another as well as to exchange one for the other, so that a grille structure may e.g. also replace a labyrinth structure.