Compact LCD projectors require compact, low power metal halide lamps to achieve maximum screen brightness. We have previously described such lighting systems, taking into account ballast stability, source etendue, and collection optics. Metal halide sources have a significant advantage over high pressure xenon, high pressure mercury, and halogen sources in that the spectral power distribution of the source can be optimized for the projection system. This is in addition to the inherently greater luminous efficacy of metal halide source. We present the result of recent studies on chemical dose composition in 50 Watt, 1.2 mm arc gap, long life metal halide lamps. Through designed experiments on chemical species, dose weight, and molar composition we were able to increase the luminous output by as much as 50 percent in some cases. The optimized metal halide lamp has 50 percent more red radiation than a 50 Watt, 1.3 mm gap high pressure mercury lamp and also produces a preferred color temperature. Knowledge of the significant factors that effect color allows us to design virtually any color gamut. It was possible to match the filter characteristics of a number of projection systems.
Compact LCD projectors require a high efficiency light source that has the smallest possible spatial extent. Further, they require optical systems that preserve the etendue. Current projector illumination systems have aberrations that produce a light beam whose etendue far exceeds the intrinsic etendue of the light source itself. As a result both efficiency and uniformity fall short of what is theoretically possible. We provide a theoretical framework for understanding these aberrations and the magnitude of their effect. We also present results showing the efficiency, uniformity, and other performance gains which are possible when these aberrations are corrected. This work also describes the performance of long-life, short-arc metal halide lighting systems that are able to increase screen brightness of compact projectors several fold without any increase in system power or heat. With these systems it has been possible to design and validate lamps operating at 50 Watts, producing > 3,000 lumens and having excellent lumen maintenance throughout their 4,000 hour life. The benefits of the combination of an improved etendue-preserving optical system and a short-arc metal halide lamp will be demonstrated.
Compact LCD projectors require a high efficiency light source that has the smallest possible spatial extent. The objective of the lamp design must be to preserve the system etendue to ensure excellent screen illuminance. We present the results of the development of projection lighting systems that produce 1,500 to 3,000 lumens, have luminous efficacious of >= 1m/W and source sizes of <EQ 1.2 mm. Results of statistically designed experiments on the lamp design parameters and design parameters of the lamp/ballast systems essential for rapid start, restart, and long life will be discussed. These design studies result in compact efficient systems. 3D luminance results - both model and experiment - will be discussed. The result of our studies is a better understanding of the factors impacting long life, high efficiency, metal halide lamps with very small source sizes. We have identified a series of designs for lamp/ballast systems that give the user an option of performance sets. We will describe recent work on the design and characterization of a long life 50 Watt, 1.2 m arc gap metal halide lighting system that produces 3,200 lumens. A theoretical characterization of the optical efficiency of an arbitrary projection optical system through discussion of the arc efficiency and the system etendue will be presented.
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