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Standard Components Light Sources Light Sources Semiconductor Components Sensors and Switches Clutches, Motors, and Solenoids Other Electrical Components Consumables Our products use a variety of different light sources. These range from intense sources such as halogen lamps to relatively weak sources such as LED arrays. The light source selected depends on the function--original exposure, quenching, etc.--and the machine design. The most important light sources from a design point of view are those commonly used for original exposure (scanning)--the halogen lamp, the fluorescent lamp, and the xenon lamp. The most basic characteristics of these three lamps are summarized in the following table. Halogen Light Intensity Spectrum Temperature dependency* Stability at start-up Heat output Cost *Dependency of light intensity on temperature Fluorescent Low Narrow Large Poor Small Low Xenon Low Narrow Large Good Smallest Lowest High Wide Small Good Large High of these three lamp types. 1 April 2001 Page 980 Standard Components Light Sources Halogen Lamp A Halogen lamp is an incandescent lamp filled with halogen gas (iodine or bromine). The halogen gas suppresses filament evaporation using a chemical regeneration process known as the "halogen cycle" (see below). Halogen lamps have a long effective life and strong light output. Characteristics · · · Extensive spectrometric distribution High illumination level Small changes resulting from the temperature of the light source and small transient changes · Long lead time to lighting · Large electricity consumption · Large heat output halogen.pcx Halogen Cycle During lamp operation, the halogen gas combines with tungsten molecules that have evaporated off the filament. The evaporated tungsten molecules are then deposited back onto the filament, instead of on the lamp wall. Consequently, there is almost no reduction of light output from lamp wall darkening. Some light reduction from filament degradation does occur, but it is significantly lower than in other incandescent lamps. The halogen regenerative process requires that tungsten-halogen 1 April 2001 Page 981 Standard Components Light Sources lamps operate at an extremely high temperature, which slightly increases lamp efficiency, and produces bright light and high temperatures. To withstand these high temperatures, tungstenhalogen lamps usually have quartz glass walls. Halogen lamps with quartz walled bulbs must be handled carefully. Quartz materials are extremely sensitive to oil and dirt from human skin, which can cause bulb wall deterioration, and premature lamp failure. Applications The intense light and wide spectral output of the halogen lamp suit it to color copiers and high-speed copiers. However, as it consumes a lot of electricity and undergoes drastic rises in temperature, it is generally not used for low-speed copiers and single scanner models. Since halogen lamps output a large amount of heat, they are also commonly used as a he