To provide a mercury discharge fluorescent lamp with an improved dimming characteristic.
A mercury discharge lamp includes amalgam for controlling mercury vapor pressure in the lamp, and this amalgam is selected so as to give a substantially optimum vapor pressure of mercury at an amalgam temperature corresponding to the maximum rated working power of the lamp and positioned in the lamp. This optimum vapor pressure is near to a minimum B at the temperature corresponding to the maximum working power and adjacent to a region D where mercury vapor pressure rises at a sharp gradient with the temperature decrease. By operating the lamp in this region, when the working power is lowered, the temperature falls, and accordingly vapor pressure of mercury is raised, whereby dimming of the lamp is performed.
MUCKLEJOHN STUART A
SCOTT MARTIN G
WHARMBY DAVID O
