Research on the Dimming Characteristics of Short Arc Ultra-High Pressure Mercury Lamps for Projection Applications

Abstract

The voltage, current and power are measured for short arc ultra-high pressure mercury lamps (UHP) with rating power 250 W driven by 50 Hz square waveform power supply. It is found that the curve slope of voltage-current characteristics is positive in most of the power range, and negative around 170 W. The photometric, colorimetric and electric parameters are measured with an integrating sphere system couple with a spectrometer in UHP dimming experiments. The results show luminous flux increases with power linearly. The luminous efficacy and color rendering index (CRI) reduce with power reduction because of the decrease of spectral continuum. The mercury pressure are calculated with the full width at the half maximum (FWHM) of 546 nm spectral band, which is 6.2-11.0 nm according to the mercury pressure 15.3-25.8 MPa for UHP power 43-258 W.