DE19530821A1 - Metal halide arc discharge lamp for projection purposes - Google Patents

Abstract

A metal halide discharge lamp, for projection purposes, has a translucent discharge vessel which contains two opposed electrodes connected to externally extending leads and which contains an ionisable filling of mercury, one or more noble gases, one or more halogens, caesium, a rare earth metal and a further metal for forming metal halides. The novelty is that the further metal is niobium pref. present in amount 0.3-3 (esp. 1.0-1.5) micro-moles per cm<3> of vessel vol.

Description

The invention relates to a metal halide discharge lamp according to the Preamble of claim 1.

Metal halide discharge lamps of this type are mainly used in opti cal reflectors or other optical imaging systems installed. your Field of application is, for example, the projection or light guide technology u. a. for overhead, slide and cinema projection and especially for video projection or for endoscopy and boroscopy. For good imaging Accordingly, the results are very short arcs and the highest Luminance (more than approx. 30 kcd / cm² on average) at color temperatures of more than 4500 K and good color rendering required. Typical lei Power values are in the range between approx. 100 W and 600 W. In addition comes the temporal constancy of the location of the discharge arc within of the lamp vessel to a special meaning. If the bow is unsteady the discharge arc stochastically out of focus of the lamp reflector and thus affects the quality of the optical image.

WO 94/23441 describes such a lamp for specific arc powers disclosed between 60 and 140 W per mm arc length with one filling, which, in addition to mercury and an inert gas, also contains a halogen compound contains elements of cesium, dysprosium and tantalum. Disadvantageous is that at higher than the specified arc powers Bo occur unrest.

The invention has for its object to be the disadvantage mentioned sided and to create a metal halide discharge lamp which a Color temperature of more than 4500 K - with good color rendering - as well a slight unsteady bow even with very high specific bow outputs having.  

This object is achieved by the characterizing note male of claim 1 solved. Further advantageous features of the invention are explained in the subclaims.

The discharge vessel of the metal halide Discharge lamp contains per cm³ of vessel volume - except typically at least least 0.5 µmol cesium (Cs) and a rare earth metal (SE), preferred Dysprosium (Dy) with a typical fill in the range between 0.3 µmol and 3 µmol - additionally the element niobium (Nb) as another measurement tall to form metal halides. The filling quantity per cm³ vessel volume The element Nb is typically in the range between 0.3 µmol and 3 µmol, preferably in the range between 1 µmol and 1.5 µmol. In Preliminary experiments had surprisingly shown that by adding from Nb the unsteadiness of the bow even with specific bow performances of up to 200 W per mm arc length is still low. The filling still contains follow de further components: at least one inert gas, for example argon (Ar) or xenon (Xe) as ignition gas with a typical filling pressure in the range between approx. 20 kPa and 60 kPa, mercury to set the desired Burning voltage, typically in the range between approx. 5 mg and 15 mg per mm Arc length for burning voltages between 30 V and 50 V as well as one or several halogens, preferably iodine (I) and / or bromine (Br) for formation of metal halides.

The lamp is advantageously combined with a reflector to form a structural unit quantity added, as described in DE-PS 28 40 031. The lamp is nä approximately axially mounted in the reflector. The reflector is e.g. B. dichroic coated.

Quartz glass or a is suitable as the material for the lamp bulb transparent ceramic material, for example Al₂O₃. Suitable for the lamp in particular a discharge vessel closed on both sides.

Two electrodes face each other inside the discharge vessel. The electrodes are each connected to a power supply, the gas are led close to the outside.  

Typical values for the specific sheet power are in the range between approx. 100 W and 200 W per mm arc length, especially in the area between approx. 150 W and 200 W per mm arc length. Doing so will mean Luminance of typically more than 45 kcd / cm² achieved.

The invention is explained in more detail below using an exemplary embodiment explained. It shows the

Figure is a schematic sectional view of the lamp with reflector.

In the figure, the longitudinal section of a metal halide discharge lamp 1 fixedly connected to a reflector with a power of 270 W is shown schematically. The discharge vessel 2 made of quartz glass has a substantially spherical shape and has a neck at two diametrically opposite positions, in which pin-shaped tungsten electrodes 3 are melted by means of sealing foils 4 made of molybdenum. The Ent the cargo space opposite ends of the sealing foils 4 are guides with current-to 5 welded to the reflector base system are in turn connected to electrical terminals 6, 7th The reflector base system be - except for the electrical connections 6 , 7 - essentially from the reflector 8 and a two-part ceramic base 9 , 10th For a more detailed explanation of the reflector base system, reference is made to DE-PS 28 40 031.

The internal volume of the discharge vessel 2 enclosing an ionizable filling is approximately 0.33 cm 3. The axially opposed electrodes 3 are 1.6 mm apart.

In addition to 12 mg Hg and 45 kPa Ar as the base gas, the filling consists of the other filling components listed in Table 1 below in the amounts specified there. The volume-related molar amounts of some filling components calculated from this are listed in Table 2 below. The specific arc power and the operating voltage are approx. 167 W per mm arc length or approx. 35 V. Table 3 shows the lighting values achieved with the lamp.

Table 1

Amount of the filling components of the lamp

Table 2

Volume-related molar amounts of some filling components

Table 3

Light technical values achieved with the filling from Table 1

Claims (6)

1. Metal halide discharge lamp for projection purposes with a translucent discharge vessel in which two electrodes face each other, which are connected to external leads, the discharge vessel contains an ionizable filling, consisting of mercury, at least one noble gas, at least one halogen, Cesium (Cs) and a rare earth metal (SE) and another metal to form metal halides, characterized in that the filling contains niobium (Nb) as a further metal. 2. Metal halide discharge lamp according to claim 1, characterized records that the filling amount of Nb in the range between 0.3 µmol and 3 µmol per cm³ of the vessel volume. 3. Metal halide discharge lamp according to claim 2, characterized records that the filling amount of Nb preferably in the range between 1.0 µmol and 1.5 µmol per cm³ of the vessel volume. 4. Metal halide discharge lamp according to claim 1, characterized records that the filling amount of the Cs at least 0.5 µmol per cm- Vessel volume is. 5. Metal halide discharge lamp according to claim 1, characterized records that the filling contains dysprosium as rare earth, where with the filling quantity of the Dy in the range between 0.3 µmol and 3 µmol per cm³ of the vessel volume. 6. Metal halide discharge lamp according to claim 1, characterized records that the discharge vessel as halogens for the halogen nid compounds iodine and bromine in a molar ratio of iodine to bromine contains in the range between 0.2 and 2.