Abstract: The high pressure discharge lamp ballast drives a high pressure discharge lamp with a synthesized-waveform alternating current made of multiple frequency components, the high pressure discharge lamp having a pair of electrodes disposed to face each other. The ballast controls a ratio of the multiple frequency components per unit time; applies a synthesized-waveform current in accordance with the ratio to the high pressure discharge lamp; and detects a lamp parameter of the high pressure discharge lamp. The control circuit is configured to shift the ratio to a first ratio when the lamp parameter is in a first state, and shifts the ratio to a second ratio when the lamp parameter is in a second state. The control circuit changes the ratio stepwise when the ratio is shifted from the first ratio to the second ratio, or when the ratio is shifted from the second ratio to the first ratio.

Abstract: Starting performance is improved by efficient UV-light irradiation, suppressing creeping discharge or atmospheric discharge at the outside of a glow discharge tube, and preventing cracks in a pinch seal portion even when an external force is exerted in the direction of bending a lead. In a discharge tube for emitting a UV-light, a light emitting chamber is formed on one side of a pinch seal portion for sealing an electrode assembly, and a lead protrusion port is formed on the opposite side thereof while pinching the seal portion, the lead protrusion port is formed as a sleeve having a predetermined gap relative to the lead, an external electrode disposed to the outside of the light emitting chamber includes a hold formed by bending fabrication of a metal plate.

Abstract: A high pressure discharge lamp ballast performs driving with a synthesized current waveform comprising a combination of first and second sets of current waveforms. The ballast controls content rates of each of the sets per unit time; detects a rotation synchronization signal for a color wheel; applies a synthesized current waveform in accordance with the synchronization signal and the content rates to a high pressure discharge lamp; and detects a lamp voltage. A period of each of the first and second sets equals to one rotation of the color wheel. The number of inversions of the second set is larger than that of the first set. The content rate of the second set is set to RL% when the lamp voltage exceeds a value V, and the content rate of the second set is set to RH% when lamp voltage falls below a value V?.

Abstract: Disclosed is an arrangement for a cut type electrode, wherein the removal of a coil is prevented and the generation of gap between turns of a coil caused by repeatedly turning on and off of the lamp is suppressed. The electrode, which is for a discharge lamp, comprises: a core rod having a leading end portion for discharge formed by a cutting process; and a coil wound around the core rod in n-turns in a state exposing the leading end portion, wherein at least a first portion between a first turn and a turn adjacent to the first turn and a second portion between an n-th turn and a turn adjacent to the n-th turn are welded.

Abstract: Starting performance is improved by efficient UV-light irradiation, suppressing creeping discharge or atmospheric discharge at the outside of a glow discharge tube, and preventing cracks in a pinch seal portion even when an external force is exerted in the direction of bending a lead. In a discharge tube for emitting a UV-light, a light emitting chamber is formed on one side of a pinch seal portion for sealing an electrode assembly, and a lead protrusion port is formed on the opposite side thereof while pinching the seal portion, the lead protrusion port is formed as a sleeve having a predetermined gap relative to the lead, an external electrode disposed to the outside of the light emitting chamber includes a hold formed by bending fabrication of a metal plate.

Abstract: In a frequency control for a high pressure discharge lamp ballast, short-term increase and decrease of a lamp voltage are suppressed. The high pressure discharge lamp ballast drives a high pressure discharge lamp with a synthesized-waveform alternating current made of multiple frequency components, the high pressure discharge lamp having a pair of electrodes disposed to face each other. The ballast includes: a control means for controlling a component contained ratio of the multiple frequency components per unit time; an output means for applying a synthesized-waveform current in accordance with the component contained ratio to the high pressure discharge lamp; and detection means for detecting a lamp parameter of the high pressure discharge lamp.

Abstract: Even when usable driving frequencies are limited, a lamp voltage is appropriately controlled. A high pressure discharge lamp ballast performs driving with a synthesized current waveform comprising a combination of first and second sets of current waveforms. The ballast includes: a control means for controlling content rates of each of the sets per unit time; a detection means for detecting a rotation synchronization signal for a color wheel; an output means for applying a synthesized current waveform in accordance with the synchronization signal and the content rates to a high pressure discharge lamp; and a detection means for detecting a lamp voltage. The sets are each in a waveform inverted so as to correspond to at least one of a rotational speed and segment positions of color wheel. A period of each of the first and second sets has a length equivalent to one rotation of the color wheel. The number of inversions of the second set is larger than the number of inversions of the first set.