Ushio Denki Kabushiki Kaisha

Keiichi Matsumoto

Takashi Yamashita

Koji Yamada

Takanori Samejima

Yukiharu Tagawa

Toyohiko Kumada

Tetsu Okamoto

Shoichi Terada

Akiko Hata

Makoto Fujii

A discharge lamp lighting device having a discharge lamp which has a pair of tungsten-made electrodes each having a protrusion formed at the tip thereof and an electric power feeding device which feeds an alternate current electric power to the discharge lamp, and is characterized in that the power feeding device has a function of switching between a first lighting mode in which a rated electric power is fed to the discharge lamp and a second lighting mode in which a lower electric power than the rated electric power is fed to the discharge lamp to light the discharge lamp, and therefore, can control electric power to be fed to the discharge lamp under such conditions that the average electric power change rate becomes 0.01-2.1 W/s during a mode switching period in which the switching from the first lighting mode into the second lighting mode is carried out.

Discharge lamp lighting apparatus

An ultra-high pressure mercury lamp in which the tungsten comprising the electrodes is prevented from spraying during starting and operation, and blackening on the inside wall of the arc tube is prevented is achieved in that at least one of the electrodes has an axial part which is made essentially of tungsten and a starting part which is made essentially of tungsten, at least one of the axial part and of the starting part containing an electron emission material with a smaller work function than tungsten such that the value of S/A in mm/% by weight is in the range 1&#x2266;S/A&#x2266;1&#xd7;10, S in mmdesignating the surface area of the part of the electrode projecting into the arc tube containing the electron emission material and A in % by weight indicating the concentration of the electron emission material in this part.

Ultra-high pressure mercury lamp

A low pressure discharge lamp in which, even during uninterrupted operation, a low lamp voltage characteristic is maintained over a long time interval and in which high radiant efficiency can be obtained over a long time is achieved via a low pressure discharge lamp which has a tubular glass bulb in which a pair of electrodes are located opposite one another, by an electron emission material which contains lithium being included on or in the electrode substrate. Advantageously, the electron emission material contains at least one of the following materials: metallic lithium, an alloy of lithium and another metal, an oxide of lithium, a mixture of an oxide of lithium with another metal oxide, and an oxide which contains lithium and another metal element and which is a compound identified by the formula Li--M--O.sub.x where M designates at least one element selected from among the alkali earth metals, rare earth metals and transition metal, and x is the number of oxygen atoms required for valency equalization.

Low pressure discharge lamp having electrodes with a lithium-containing

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Himeji, Japan

Keiichi Matsumoto