To provide a high brightness discharge lamp which can solve such problems as that luminous temperature changes from a prescribed range, or short life due to blackening, or delicate adjusting is difficult for maintaining discharge, when the lighting of high brightness discharge lamp is adjusted, and which prevents the problem that the lamp brightness varies greatly and gives a sense of incongruity to the users in case of putting out.
When the high brightness discharge lamp is turned off according to the level of outside light, a turn-off signal is transmitted by the operation of turn-on/turn-off means 5b. Then the power control device 6b controls the supply power to the high brightness discharge lamp so as to change gradually the lighting output of the above high brightness discharge lamp 4b. After an elapse of time of this gradual lighting output change, the high brightness discharge lamp is turned off. The users do not notice the brightness change as lighting output changes taking time. When the high brightness discharge lamp is turned on, the reverse relation occurs.
NAGASAKI FUMIHIKO
MATSUSHITA NOBUO
ITO AKIRA
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