Electrophotographic copying apparatus including drum conditioning

Abstract

This apparatus relates particularly to apparatus and method for conditioning and pre-fatiguing a photoconductive drum in an electrophotographic copying apparatus. In a preferred embodiment, a two color LED is located adjacent the photoconductive surface. The color of the emissions from these two-color LED's is controlled through the polarity of the voltage applied to the terminals; that is, reversal of the polarity of the voltage applied reverses the color displayed. Therefore, in a preferred embodiment of the present invention, means are provided for supplying an AC driving current to the LED which would inherently result in a synchronous high speed flashing of the red/green light. By combining this AC source with a controllable DC bias, it is possible to provide a drum discharge and preconditioning light which is an all red light; an all green light; or which has controllable percentages of red and green in each duty cycle. In an optimum conditioning cycle, when the machine is first turned on a maximum of two cycles of all red light are utilized to build in fatigue; it is thereafter desirable during extended use of the machine to use only green, which will reduce the light fatigue effect on the photoconductive surface. By an appropriate timing circuit, a controllable shift from all red at the beginning of use of the machine through a combined duty cycle combining both red and green to an all green light can be accomplished.