This invention relates to vehicular lighting devices and more particularly to a bulb for use in a lamp of a motor vehicle.
When driving at night, the glare of the light from the headlight of a motor vehicle coming from the opposite direction may daze the driver's eyes and lead to dangerous or embarrassing situations. To prevent this glare, a bulb, referred to as the "H4" type in this field, has been proposed. This H4 bulb comprises a main filament employed during running periods and a submain filament employed when passing by a motor vehicle coming from the opposite direction.
In detail, the obvious normal procedure during night driving is to employ the main filament when a distant place is desired to be viewed and the sub-main filament when passing by a vehicle coming from the opposite direction so that the other driver is not dazed by the glare of the light from the headlight of the vehicle. However, this prior art lamp bulb proves to be insufficient to eliminate the glaring problem.