High-Pressure Discharge Lamp

Abstract

The invention relates to a high-pressure discharge lamp which comprises at least a burner (2) having a symmetrical discharge chamber (21), where at least the outer contour of the burner (2) has an elliptical shape in the region of the discharge chamber (21), two electrodes (41, 42) extending into the discharge chamber (21) and arranged in mutual opposition on the major axis of symmetry of the discharge chamber (21), and a multilayer interference filter (3) arranged on the outer contour of the burner (2) in the region of the discharge chamber (21), wherein the interference filter (3) mainly reflects light from at least one wavelength range of the UV light into the space between the two electrodes (41, 42).

Description

Further details, features, and advantages of the invention will become apparent from the ensuing description of a preferred embodiment which is given with reference to the drawing, in which:

FIG. 1 is a diagrammatic cross-sectional view of a lamp bulb of a high-pressure gas discharge lamp (UHP lamp) which supports a 17-layer interference filter.

FIG. 1 diagrammatically and in cross-section (FIG. 1.1) shows a lamp bulb 1 with a symmetrical discharge space 21 of a high-pressure gas discharge lamp (UHP lamp) according to the invention. The burner 2, which is formed from one integral piece, which hermetically encloses a discharge space 21 filled with a gas usual for this purpose, and whose material is usually hard glass or quartz glass, comprises two cylindrical, mutually opposed regions 22, 23 between which a substantially spherical region 24 with a diameter in a range of approximately 8 mm to 14 mm is present. The outer contour of the burner 2 in the region of the discharge chamber 21 has an elliptical shape. The elliptically shaped discharge space 21 with an electrode arrangement is centrally positioned in the region 24. The electrode arrangement substantially comprises a first electrode 41 and a second electrode 42, between whose mutually opposed tips a luminous discharge arc is excited in the discharge space 21, such that the discharge arc serves as a light source of the high-pressure gas discharge lamp. The ends of the electrodes 41, 42 arranged on the major axis of symmetry of the discharge chamber 21 are connected to electrical connection pins 51, 52 of the lamp via which a supply voltage necessary for lamp operation is supplied by means of a supply unit (not shown in FIG. 1.1) designed for connection to a mains voltage.

An interference filter 3 is provided on the entire outer surface of the region 24. The interference filter 3 has a total thickness of approximately 1 μm and comprises a plurality of layers. The design of the interference filter 3, or its construction, is visible in FIG. 1.2. The interference filter 3 is built up from 17 layers, wherein the total layer thickness of the SiO₂ layers is approximately 674.9 mm and the total thickness of the ZrO₂ layers is approximately 305.8 μnm.

The two individual layers 3.1 and 3.2 of the interference filter 3 are characterized in particular by their differing indices of refraction, such that a layer of low index alternates with a layer of higher index each time. The material for the layer 3.2 of lower refractive index is SiO₂; the material for the layer 3.1 of higher refractive index is ZrO₂.

The interference filter 3 reflects mainly UV light from the wavelength range from 335 to 395 nm with a reflectivity of more than 90% into the region between the two electrodes 41 and 42.

The layer-by-layer application of the interference filter 3 takes place in a manufacturing process by means of a sputtering method that is known per se.

No detrimental effects in excess of the normal ageing of comparable lamps could be observed for a UHP lamp with the lamp bulb 1 described above and operated at a rated power of 120 W, also after several thousands of hours of operation at the loading limit, i.e. at the high-load point.

The UHP lamp according to the invention was tested at a power consumption of 120 W for its photometric and electrical properties in a standard test procedure in an Ulbricht sphere photometer. The radiant power in the UV range (approximately 200 to 400 nm) was 1.33 W and in the visible range (approximately 400 to 780 mn) 31.2 W. Given a quantity of light of 7918 lm, the luminous efficacy was accordingly 66.2 lm/W.

A similar measurement of a comparable UHP lamp, but without the interference filter 3 described above, gave the following values. The radiant power in the UV range (approximately 200 to 400 nm) was 7.13 W and in the visible range (approximately 400 to 780 nm) 30.97 W. A light quantity of 7325 lm thus resulted in a luminous efficacy of 61.3 lm/W.

A particularly advantageous embodiment of the invention relates to a high-pressure gas discharge lamp used for projection purposes.

Claims

1. A high-pressure discharge lamp, at least with a burner (2) having a symmetrical discharge chamber (21), where at least the outer contour of the burner (2) has an elliptical shape in the region of the discharge chamber (21), with two electrodes (41, 42) extending into the discharge chamber (21) and arranged in mutual opposition on the major axis of symmetry of the discharge chamber (21), andwith a multilayer interference filter (3) which is arranged on the outer contour of the burner (2) in the region of the discharge chamber (21), wherein the interference filter (3) reflects mainly light from at least one wavelength range of UV light into the space between the two electrodes (41, 42).

2. A high-pressure discharge lamp as claimed in claim 1, characterized in that a layer (3.1) having a higher refractive index and a layer (3.2) having a lower refractive index occur in alternation in the layer construction of the multilayer interference filter (3).

3. A high-pressure discharge lamp as claimed in claim 1, characterized in that the light from those wavelength ranges of the UV light that are not reflected by the interference filter is absorbed.

4. A high-pressure discharge lamp as claimed in claim 2, characterized in that the layer (3.2) of the interference filter (3) having the lower refractive index is preferably made substantially of SiO2, and the second layer (3.1) of the interference filter (3) is made of a material having a higher refractive index than SiO2, preferably consisting substantially of zirconium oxide (ZrO2).

5. A high-pressure discharge lamp as claimed in claim 2, characterized in that the second layer (3.1) is made up of a material from the group of titanium oxide, tantalum oxide, niobium oxide, hafnium oxide, silicon nitride, and particularly preferably zirconium oxide ZrO2, or a mixture of these materials.

6. A high-pressure discharge lamp as claimed in claim 1, characterized in that the high-pressure discharge lamp is a UHP lamp.

7. A high-pressure discharge lamp as claimed in claim 6, characterized in that the interference filter (3) reflects mainly UV light in the wavelength range from 335 to 395 nm into the region between the two electrodes (41, 42).

8. A lighting unit comprising at least one lamp as claimed in claim 1.

9. A projection system comprising at least one lamp as claimed in claim 1.