Title of Invention

"SHORT-ARC HIGH-PRESSURE DISCHARGE LAMP FOR DIGITAL PROJECTION TECHNOLOGIES"

Abstract

This invention relates in a short-arc high-pressure discharge lamp (1) with a xenon fill for digital projection purposes, 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 0.8 x P < L < lx P+l, where p is the lamp power in KW. Further, the diameter 0 of the circular-cylindrical middle section (8a) of the anode (8) in mm obeys the relationship D > 2.1 x L +10.

Full Text

1A TECHNICAL FIELD The invention is based on a short-arc high-pressure discharge lamp according to the features of the invention. It involves in particular, a short-arc high-pressure discharge lamp with a xenon fill, as is used in cinema projection. Prior Art The known xenon short-arc lamps for projection purposes were optimized fro arc lengths and electrode geometries which are Ideal for 35 to 70 mm film projection. The picture diagonals of these films tie in the range of between 28 and 60 mm. If such standard lamps are used In modern digital projection systems with DMD, DLP, LCD and D-ILA technology, then owing to the mismatch between the tamp and the optical system, a great deal of light is lost and does not reach the screen. This lost light is converted into heat in the projector and leads to additional problems. To date, it has been possible to resolve this problem only by a higher lamp power, which then requires greater outlay on cooling, an optimized mirror design, which places great demands on the accuracy and the simultaneously tasks, and additional double mirrors, which in turn entail cooling problems in the reflection volume. Description of the Invention It is an object of the present invenuon to provided a short-arc lamp with a xenon fill, which permits optimum focusing of the tight onto small cross sections of between 10 and 25 mm, corresponding to the diagonals of the integrators that are used in digital projection technologies (DMD, DLP, LCD and D-JLA). 2 By setting the separation L in mm of the two mutually facing end lamp is hot, accordtog to the relationship 0.8 x P The stronger heating of the front surface of the anode (anode plateau) for shorter arcs also requfres adaption of the anode geometry. For instance, the diameter D of the anode in mm must satisfy the relationship D > 2.1 x L +10, where L is the separation of the mutually facing end sections of the anode and the cathode in mm when the lamp is hot Advantageously, for optimum luminous efficiency with a long life, the frustoconical end section of the anode, which faces the cathode, should have a plateau AP with a diameter in mm that satisfies the relationship 1.8 x L For optimum distrbution of the light density throughout the life, the tip of the conical end section of the cathode is further advantageously designed as a hemisphere, wherein the radius R of the hemisphere in -3- mm satisfies the relationship 0.12xp+0 .1 Advantageously, the conical end section of the cathode has a vertex angle or of between 36 and 44 °. Further, the frustoconical end section of the anode has, for optimum operation, a vertex angle p of between 90 and 105° . More pointed geometries lead to stronger burn-off of the electrode tips, while blunter geometries cause a high degree of shadowing in the proj ector. For optimum operation with a sufficiently high efficiency (lumen/W), and an acceptable decrease in the light flux over the life of the lamp, the lamp should be operated, at a rated power P of between 0 and 5.5 kW, with a lamp current I in Amperec of the relationship 22xp+38 Description of the accompanying drawings With the following figures, the invention will be explained in more detail in relation to an exemplary embodiment: Figure 1 shows a short-arc high-pressure discharge lamp according to the invention, Figure 2 shows, in an enlarged representation, the electrode arrangement of the short-arc high-pressure discharge lamp according to Figure 1. Figure 1 represents a short-arc high-pressure discharge lamp 1 according to the invention with a Xe fill. The lamp 1, with a power consumption of 3 000 W, consists of a rotationally symmetric light bulb 2 made of quartz glass, the two ends of which are each fitted with a lamp shaft 3, 4, also made of quartz glass. A - 4 - tungsten electrode rod 5, the inner end of which supports a cathode 6, is fused hermetically into one of the shafts, the shaft 3. A tungsten electrode rod 7, the inner end of which has an anode 8 fastened to it, is likewise fused hermetically into the other lamp shaft 4. Base systems 9, 10 for support and electrical connection are fitted to the outer ends of the electrode shafts 3, 4. As can be seen in Figure 2, the cathode 6 is composed of a conical end section 6a, which faces the anode 8, and an end section 6b which faces the electrode rod 5 and has a circular-cylindrical subsection as well as a frustoconical subsection, a section 6c of smaller diameter, which is likewise circular-cylindrical and is referred to as a heat damming groove being located between these two sections 6a, 6b. The tip of the conical end section 6a, which faces the anode 8 and has a vertex angle a of 40°, is designed as a hemisphere with a radius R of 0.6 mm. The anode 8 consists of a circular-cylindrical middle section 8a with a diameter D of 22 mm and two frustoconical end sections 8b, 8c, which respectively face the cathode 6 and the electrode rod 7. The frustoconical end section 8c that faces the cathode 6 has a plateau AP with a diameter of 6 mm. All the sections of the two electrodes 6, 8 are made of tungsten. The two electrodes 6, 7 are fitted opposite one another, in alignment with the axis of the lamp bulb 2, in such a way that the electrode separation, or arc length, is 3.5 mm when the lamp is hot. When this lamp is used in a digital projection system, an improvement of up to 50% can be achieved compared with conventional short-arc high-pressure discharge lamps with a xenon fill. 5 WE CLAIM 1. A short-arc high-pressure discharge tamp (1) comprising a discharge vessel (2) having oppositely disposed atteast one cathode (6) and atfeast one anode (8), the discharge vessel (2) containing 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 frustocontcal end section (8c) facing the cathode (6), and wherein when the discharge lamp (1) is used In digital projection technobgies, the high-pressure discharge lamp (1) additionally comprising: - a distance separation distance (L) configured in mm between the two mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) when the tamp is hot such as to satisfy a relationship of: 0.8xP - a diameter (D) of the crcular-cylndricat middle section (8a) of the anode (8) configured In mm to satisfy a relationship of: D > 2. lxL + 10, where L is the separation distance between the mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) fri mm. 2. The short-arc high-pressure discharge lamp as claimed in claim 1, wherein the frustoconkral end section (8c) of the anode (8), which faces the cathode (6), has a plateau (AP) with a diameter in mm that satisfies a relationship of: 1.8 X L-l 6 distance of the mutually facing end sections (6a, 8c) of the cathode (6) and the anode (8) h mm. 3. The short-arc high-pressure discharge lamp as claimed in claim 1, wherein the tip of the conical end section (6a) of the cathode (6) is designed as a hemisphere, and wherein the radius R of the hemisphere in mm satisfies a rebtionshfc of: 0.12 X P+0.1 with P being the tamp power in KW. 4. The short-arc high-pressure discharge lamp as claimed m claim 3, wherein the conical end section (6a) of the cathode (6) has a vertex angle a of between 36 and 44°. 5. The short-arc high-pressure discharge lamp as claimed in claim 1, wherein the frustoconical end section (8a) of the anode (8), which faces the cathode (6), has a vertex angle of between 90 and 105°. 6. A method of operating a short-arc high-pressure discharge tamp (1) as claimed in one or more of claims 1 to 5, characterized by comprising the steps of: - operating the lamp (1) at a rated power P between 0 and 5.5 KW, with a lamp current I in Ampere of a relationship 22 x P + 38 7 and operathg at a rated power P between 5.5 and 12 KW with a lamp current I in Ampere of a relationship 10 x P + 100 This invention relates in a short-arc high-pressure discharge lamp (1) with a xenon fill for digital projection purposes, 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 0.8 x P 2.1 x L +10.

Documents:

00661-cal-2001-abstract.pdf

00661-cal-2001-claims.pdf

00661-cal-2001-correspondence.pdf

00661-cal-2001-description(complete).pdf

00661-cal-2001-drawings.pdf

00661-cal-2001-form-1.pdf

00661-cal-2001-form-18.pdf

00661-cal-2001-form-2.pdf

00661-cal-2001-form-3.pdf

00661-cal-2001-form-5.pdf

00661-cal-2001-g.p.a.pdf

00661-cal-2001-letters patent.pdf

661-CAL-2001-CORRESPONDENCE 1.1.pdf

661-CAL-2001-OTHERS.pdf

661-CAL-2001-PA.pdf