DC DISCHARGE LAMP, LIGHTING SYSTEM, AND IMAGE PROJECTING DEVICE

摘要

PROBLEM TO BE SOLVED: To accumulate extra halides that cannot be vaporized in a bulb to collect by forming the coolest portion in a place where light beams of the bulb are affected less. SOLUTION: A bulb 2 is provided with an almost spherical bulb portion 3. An anode 5 and a cathode 6 are sealed to the inside of the bulb portion 3 while being opposed to each other. A discharge medium containing a halide, a rare gas, and mercury is sealed in the bulb portion 3. In the sealed portion of the cathode 6 facing the inside of the bulb portion 3, a recess 10 is formed to bulge outward the bulb portion 3. The sealed portion of the cathode 6 is located in a place that affects light beams less, and the recess 10 is the coolest part of the tube wall of the bulb portion 8, accumulating extra halides therein. By keeping the bulb portion 3 almost spherical, an increase in the inner volume of the bulb is minimized to easily increase the load to the tube wall.