Gas Discharge Lamps for Electrophotographic Exposure

The multitude of uses for lamps in the various steps of the xerographic process are enumerated. Particular emphasis is placed on the use of gas-discharge lamps for exposure, with their requirement of spectral control and adequate radiant power. The characteristics of various types of lamps are considered and the existence of a trouble-some ``power gap´´ is uncovered. The efficient performance of low-pressure arcs (such as fluorescent and low-pressure sodium lamps) is limited to low powers by electron de-excitation in the presence of self-absorption. On the other hand, high-pressure arc lamps perform efficiently at high powers, but it is difficult to operate these lamps at lower powers in the ``power gap´´ because of a complex set of interrelated reasons. Lamp designs which may fill this power gap are discussed. The radiant emission from various lamps is considered as well as techniques for manipulating the spectra, particularly the use of metallic halide additives. Overall, a major problem is that commercially available lamps reservice are designed for general illumination purposes while the electrophotographic requirements are different and more demanding.