EP1217644B1 - Short arc high pressure discharge lamp for use in digital projection techniques - Google Patents

Description

Technical area

The invention relates to a short-arc high-pressure discharge lamp according to the preamble of claim 1. It is in particular a short-arc high-pressure discharge lamp with a xenon filling, as used in cinema projection.

State of the art

The familiar projection xenon short arc lamps have been optimized for arc lengths and electrode geometries that are ideal for 35 to 70 mm film projection. The image diagonals of these films are in the range between 28 and 60 mm. If such standard lamps are used in modern digital projection systems with DMD, DLP, LCD and D-ILA technology, the mismatch between the lamp and the optical system loses a lot of light that the screen does not reach. This lost light is converted into heat in the projector and leads to additional problems. Previously, this problem could be solved only by a larger lamp power, which then requires a higher cooling effort, an optimized mirror design that places high demands on the accuracy and the simulation effort and additional double mirror, which in turn bring cooling problems in the reflector volume.

From the DE-U-200 05 764 For example, a xenon short-arc lamp with a power of 3000 W, an arc length of 4 mm and a diameter of the anode casing body of 21 mm is known. For operation, this lamp is operated with a lamp current of 110 A.

Presentation of the invention

It is an object of the present invention to provide a xenon-filled short arc lamp according to the preamble of claim 1, which optimally focuses the light to small cross sections between 10 and 25 mm, corresponding to the diagonals of the integrators as used in digital projection techniques (DMD, DLP, LCD and D-ILA).

This object is solved by the characterizing features of claim 1. Particularly advantageous embodiments can be found in the dependent claims. The lamp is also advantageous to operate with a lamp current of the features of claim 5 is sufficient.

By setting the distance L in mm of the two mutually facing end portions of the anode and cathode in the hot state of the lamp according to the relation 0.8 x P ≦ L ≦ 1 x P + 1, where P is the lamp power in kW, an optimal illumination of the picture window. For larger arc lengths, the efficiency of the system, i. H. the ratio of emitted luminous flux to absorbed power clearly down. If the distance anode - cathode is shorter than in the relation, then the life span of the lamp falls below acceptable values.

The stronger heating of the anode front surface (anode plateau) with shorter arcs also requires an adaptation of the anode geometry. Thus, the diameter D of the anode in mm must satisfy the relation D ≥ 2.1 x L + 10, where L is the distance of the facing end sections of the anode and cathode in mm in the hot state of the lamp.

For an optimum light output with a long service life, the frustoconical end portion of the anode facing the cathode must have a plateau AP with a diameter in mm which corresponds to the relation 1.8 × L - 1 ≤ AP ≤ 1.8 x L + 1 is sufficient, where L in turn is the distance of the facing ends of the anode and cathode in mm in the hot state. Deviations of the anode plate diameter downwards lead to a shortening of the service life due to severe erosion (crater formation) on the anode plateau. In the case of a larger anode plateau than given by Relation, the system efficiency is due to the shading back.

For optimum luminance distribution over the entire lifetime, it is advantageous to form the tip of the conical end section of the cathode as a hemisphere, wherein the radius R of the hemisphere in mm of the relation 0.12 x P + 0.1 ≤ R ≤ 0.12 x P + 0 , 5 with P as lamp power in kW is sufficient. Larger diameters of the hemisphere result in a lower luminance, smaller diameters lead to increased cathode erosion.

Advantageously, the conical end portion of the cathode has a cone angle α between 36 and 44 °. In addition, the truncated conical end portion of the anode has a cone angle β between 90 and 105 ° for optimum operation. Higher geometries lead to a strong erosion of the electrode tips, while blunt geometries lead to a strong shading in the projector.

For optimum operation with a sufficiently high efficiency (lumens / W) and an acceptable luminous flux reduction over the life of the lamp, the lamp should have a rated power P between 0 and 5.5 kW with a lamp current I in A of 22 x P + 38 ≤ I ≤ 22 x P + 65 and at a rated power P between 5, 5 and 12 kW with a lamp current I in A of the relation 14 x P + 100 ≤ I ≤ 22 x P + 65 are operated. While lower currents reduce the light output in the system, at higher currents the erosion of the cathode increases and the maintenance falls below acceptable levels.

Description of the drawings

Figur 1

zeigt eine erfindungsgemäße Kurzbogen-Hochdruckentladungs-lampe

Figur 2

zeigt in vergrößerter Darstellung die Elektrodenanordnung der Kurzbogen-Hochdruckentladungslampe gemäß Figur 1

With the following figures, the invention will be explained in more detail with reference to an exemplary embodiment:

FIG. 1

shows a short-arc high-pressure discharge lamp according to the invention

FIG. 2

shows an enlarged view of the electrode assembly of the short-arc high-pressure discharge lamp according to FIG. 1

In FIG. 1 a short-arc high-pressure discharge lamp 1 according to the invention is shown with an Xe filling. The lamp 1 with a power consumption of 3000 W consists of a rotationally symmetrical lamp envelope 2 made of quartz glass at the two ends of each a lamp shaft 3, 4 is also made of quartz glass. In one shaft 3, an electrode rod 5 made of tungsten is sealed gas-tight, the inner end of which carries a cathode 6. In the other lamp shaft 4, an electrode rod 7 made of tungsten is also sealed gas-tight, at the inner end of an anode 8 is attached. At the outer ends of the electrode shafts 3, 4 base systems 9, 10 are mounted for mounting and electrical contact.

Like from the FIG. 2 the cathode 6 is composed of a conical end portion 6a facing towards the anode 8 and an end portion 6b facing the electrode rod 5 with a circular-cylindrical and frustoconical portion, wherein between these two portions 6a, 6b there is also a circular-cylindrical portion 6c, called heat build-up is of smaller diameter. The tip of the anode 8 facing conical end portion 6a with a cone angle α of 40 ° is formed as a hemisphere with a radius R of 0.6 mm.

The anode 8 consists of a circular cylindrical central portion 8a with a diameter D of 22 mm and two frustoconical end portions 8b, 8c facing the cathode 6 and the electrode rod 7, respectively. The cathode 6 facing the frusto-conical end portion 8c has a plateau AP with a diameter of 6 mm. All sections of the two electrodes 6, 8 are made of tungsten.

The two electrodes 6, 8 are mounted opposite one another in the axis of the lamp bulb 2 in such a way that, in the hot state of the lamp, there is an electrode spacing or an arc length of 3.5 mm.

When used in a digital projection system, this lamp can achieve an increase of up to 50% compared to conventional xenon-filled short arc high pressure discharge lamps.

Claims (5)

1. Short-arc high-pressure discharge lamp (1) with a discharge vessel (2) which, besides a cathode (6) and an anode (8) that are situated opposite each other, contains a fill comprising at least xenon, wherein the cathode (6) has a conical end section (6a) facing the anode (8) and the anode (8) has a circular-cylindrical middle section (8a) and a frustoconical end section (8c) facing the cathode (6), and the high-pressure discharge lamp (1) for use in digital projection technologies has the following further features:

   - the separation L in mm of the two mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) when the lamp is hot is given by the relationship $$\mathrm{0.8}\mathrm{\times }\mathrm{P}\mathrm{\le }\mathrm{L}\mathrm{\le }\mathrm{1}\mathrm{\times }\mathrm{P}\mathrm{+}\mathrm{1}$$

   

   
   where P is the lamp power in kW

   - the diameter D of the circular-cylindrical middle section (8a) of the anode (8) in mm is given by the relationship $$\mathrm{D}\mathrm{\ge }\mathrm{2.1}\mathrm{\times }\mathrm{L}\mathrm{+}\mathrm{10}$$

   

   
   where L is the separation of the mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) in mm,

   characterized in that the frustoconical end section (8c) of the anode (8), which faces the cathode (6), has a plateau AP with a diameter in mm that satisfies the relationship $$\mathrm{1.8}\mathrm{\times }\mathrm{L}-1\mathrm{\le }\mathrm{AP}\mathrm{\le }1.8\mathrm{\times }\mathrm{L}\mathrm{+}\mathrm{1}$$

   

   
   where L is the separation of the mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) in mm.
2. Short-arc high-pressure discharge lamp according to Claim 1, characterized in that the tip of the conical end section (6a) of the cathode (6) is designed as a hemisphere, wherein the radius R of the hemisphere in mm satisfies the relationship $$\mathrm{0.12}\mathrm{\times }\mathrm{P}+0.1\mathrm{\le }\mathrm{R}\mathrm{\le }0.12\mathrm{\times }\mathrm{P}\mathrm{+}0.5$$

   

   with P being the lamp power in kW.
3. Short-arc high-pressure discharge lamp according to Claim 2, characterized in that the conical end section (6a) of the cathode (6) has a vertex angle α of between 36 and 44°.
4. Short-arc high-pressure discharge lamp according to Claim 1, characterized in that the frustoconical end section (8a) of the anode (8), which faces the cathode (6), has a vertex angle β of between 90 and 105°.
5. Method of operating a short-arc high-pressure discharge lamp (1) according to one or more of Claims 1 to 4, characterized in that the short-arc high-pressure discharge lamp (1) is operated

   - at a rated power P of between 0 and 5.5 kW, with a lamp current I in A of the relationship $$\mathrm{22}\mathrm{\times }\mathrm{P}\mathrm{+}\mathrm{38}\mathrm{\le }\mathrm{I}\mathrm{\le }\mathrm{22}\mathrm{\times }\mathrm{P}\mathrm{+}\mathrm{65}$$

   

   - and at a rated power P of between 5.5 and 12 kW, with a lamp current I in A of the relationship $$\mathrm{10}\mathrm{\times }\mathrm{P}\mathrm{+}\mathrm{100}\mathrm{\le }\mathrm{I}\mathrm{\le }\mathrm{22}\mathrm{\times }\mathrm{P}\mathrm{+}\mathrm{65}$$

   

Images