Optical device

#1. Field of Invention

#The present invention concerns a light-source device used in liquid crystal projection equipment, more specifically, a light-source device using a short-arc type of high pressure mercury discharge lamp having 0.16 mg/mm3 or more of mercury sealed within a discharge envelope.

#2. Description of Related Art

#FIG. 1 is a cross-sectional view of an embodiment of the present invention.

#FIGS. 2(A) and 2(B) are explanatory diagrams showing the site of damage to the concave reflection mirror in cross-sectional and front elevational views, respectively.

#FIG. 3 is a front view of an embodiment of the present invention.

#A discharge envelope 11 of the short-arc type of high pressure mercury discharge lamp 10, in FIG. 1 is a roughly spherical unit composed of quartz glass. A pair of electrodes, an anode 13 and a cathode 14 are disposed facing each other within discharge envelope 11. In addition, mercury and a rare gas are sealed within discharge envelope 11. Sealing sections 12 are connected integrally at opposite sides of discharge envelope 11. Sealing sections 12 are formed by depressurization of the interior while the quartz glass bulbs extending from both ends of discharge envelope 11 are in the molten state. In short, they are formed by the shrink sealing method. Molybdenum foil (not illustrated) electrically connects the anode 13, cathode 14 and external lead 15 and is embedded within sealing sections 12.

#The polarity of the direct current lighting type of anode 13 and cathode 14 may be opposite from that shown in FIG. 1, and alternating current lighting type may also be used. Furthermore, sealing sections 12 may also be formed by the pinch seal method in which the quartz glass bulb is compressed while in the molten state.

#Specific examples of short-arc type of the high pressure mercury discharge lamp 10 will now be described. In the illustrated example, the amount of mercury sealed within the envelope 11 is 0.20 mg/mm3 while 10 KPa pressure of argon gas is sealed as the rare gas. Furthermore, the electrode separation is 1.5 mm, the internal volume of the discharge envelope 11 is 260 mm3, the rated voltage is 82 V and the rated consumed power is 200 W. Of course, these values are not sole ones usable. However, an amount of mercury in excess of 0.16 mg/mm3 must be sealed in the envelope 11 when short-arc type of high pressure mercury discharge lamp 10 is used as the light source lamp for a liquid crystal projector.