Projection systems have found widespread use in conference rooms and other professional applications during the last decade and are now entering the home TV market at a considerable pace. Projectors as small as about one litre are able to deliver several thousand screen lumens and are, with a system efficacy of over 10 lm W −1 , the most efficient display systems realized today. Short arc lamps are a key component for projection systems of the highest efficiency for small-size projection displays. The introduction of the ultra high performance (UHP) lamp system by Philips in 1995 can be identified as one of the key enablers of the commercial success of projection systems. The UHP lamp concept features outstanding arc luminance, a well suited spectrum, long life and excellent lumen maintenance. For the first time it combines a very high pressure mercury discharge lamp with extremely short and stable arc gap with a regenerative chemical cycle keeping the discharge walls free from blackening, leading to lifetimes of over 10 000 h. Since the introduction of the UHP lamp system, many important new technology improvements have been realized: burner designs for higher lamp power, advanced ignition systems, miniaturized electronic drivers and innovative reflector concepts. These achievements enabled the impressive increase of projector light output, a remarkable reduction in projector size and even higher optical efficiency in projection systems during the last years. In this paper the concept of the UHP lamp system is described, followed by a discussion of the technological evolution the UHP lamp has undergone so far. Last, but not least, the important improvements of the UHP lamp system including the electronic driver and the reflector are discussed.
Infrared (IR) continuum radiation from the arc of high and ultra-high pressure (UHP) mercury lamps was measured and modelled. Three major contributions to the IR continuum are electron–atom bremsstrahlung, which is dominant, electron–ion bremsstrahlung and electron–ion recombination radiation. The line width of the resonance broadened Hg 71S0 to 61P1 transition at 1014 nm was used to determine the arc core Hg density, and the radiance of this line was used to determine the arc temperature as a function of radius. The temperature map for the UHP lamp was checked using the Bartels method on the 546 nm line of Hg. Model results based on recently published electron–atom bremsstrahlung coefficients were found to be in good agreement with measurements across the near IR.
Shorter arcs and higher gas pressures increase the collection efficiency and produce a spectrum which is ideal for video projection. Taking into account the physical lamp efficiency ideal arc lengths are given. New UHP products will realise 30% more light on the screen.
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Abstract.A systematic investigation into transition metal halides and ~oxides showed the high potential of transition metal oxides as visible radiators for highly efficient gas discharge light sources. Zirconium monoxide (ZrO) has been identified as most promising candidate combining highly attractive green and red emission band systems with very high dissociation energy (8.2eV) which assures that the molecule is stable even in the hot plasma centre. Thus far, however, it has been impossible to keep ZrO in the gas phase of a closed discharge vessel, because at wall temperature usually compounds are formed which have negligible vapour pressures. We succeeded in establishing a regenerative chemical cycle by filling ZrX 4 (X=Cl, Br, I) together with a stable, but volatile oxygen compound (like MoO 2 X 2 ) and realized thus highly attractive, novel gas discharge light sources.PACS numbers: 42.72. Bj, 82.33.Xj The aim of any lamp engineer is to develop a white light source with good colour rendering properties (Ra 8 > 80) and highest luminous efficacy . Current discharge lamps -emitting mainly atomic radiationare reaching only about half of the theoretical efficacy limit of 200-230 lm/W. The possible efficacy rise by increasing atomic radiation is limited by self-absorption of the atomic lines (= radiation trapping). This limitation does not apply for molecular radiation, since the molecular emission is distributed over a huge number of molecular transitions which is several orders of magnitude higher than the corresponding number of atomic lines. As a matter of fact, various molecular radiators have been investigated in gas discharges for lighting applications in the course of the last century [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Nevertheless there still is no large-scale commercially applied discharge lamp type on the market whose radiation output is dominated by molecular emission. Molecular discharge light sources investigated in the past suffered from serious drawbacks: Severe chemical attack of the wall material, corrosion of the tungsten electrodes and -in most cases -poor plasma efficacy. Therefore, we strive for a breakthrough efficacy improvement by introducing novel molecular radiators for discharge lamps.
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