Ever since Irving Langmuir's invention of the tungsten filament lamp in 1916, researchers at the General Electric Company (GEC) have been trying to produce more effective light bulbs. One of the problems with the tungsten filament (or incandescent) light bulb is that the tungsten evaporates during operation. This not only produces an absorbing coating on the inside wall of the bulb but it also weakens the filament, eventually leading to breakage. The manufacturers' dilemma is that the hotter filaments produce greater efficiency, but the greater evaporation shortens their lifetime.
GEC research engineer Fredrick Moby made a breakthrough in 1960 when he placed an electrically heated, high temperature tungsten filament inside a compact fused quartz envelope filled with a halogen gas (usually iodine or bromine). His halogen lamp fitted into a standard light bulb socket. Not only did this bulb have a higher luminous efficiency, it also had about twice the lifetime (2,000 to 4,000 hours) of previous tungsten lamps. With a normal filament bulb, 98 percent of the power used is emitted as heat and only 2 percent as light. A halogen bulb changes these figures to 91 percent and 9 percent, and this saves money. Moby was working parallel to other engineers involved in the GEC project. Elmer Fridrich and Emmett Wiley also patented an improved type of incandescent lamp in 1959.
Getting more light for a specific power expenditure makes halogen bulbs ideal for car headlights. Also in offices much less air conditioning power is needed to counteract the effect of heating from lighting.
