Contrast of electrostatic latent images with a light flooding step

In a method for the contrast enhancement of an electrostatic latent image on a dielectric surface which comprises:

• positioning a photoconductive member adjacent said dielectric surface in a manner forming an air gap therebetween, applying an electrical potential between said photoconductive member and said dielectric surface, irradiating selected portions of said photoconductive member while excluding other portions of the photoconductive member from said irradiation, whereby electric charge is caused to form on selected portions of said dielectric surface corresponding to said irradiated photoconductive member portions as a result of charge transfer between said photoconductive member and said dielectric when the voltage drop across said air gap bounded by facing surfaces of said photoconductive member and said dielectric exceeds a predetermined minimum value, said electrical potential being applied as a plurality of discrete pulses of similar polarity, said pulses being of a duration such that said voltage drop across said air gap will exceed said predetermined minimum value in the selected irradiated portions of said photoconductor and will be below said predetermined minimum value in said excluded portions thereof, said pulses of electrical potential being separated by time periods in which said applied electrical potential is essentially zero, said time periods having an average duration of at least the average duration of said applied pulses so that the relative density of electric charge in said selected portions of the dielectric surface is increased by said plurality of pulses over any electric charge density in the non-irradiated portions thereof, the improvement comprising:
• grounding and uniformly irradiating said photoconductive member during each said time period of essentially zero applied potential which separate said pulses, whereby the intensity and contrast of the electrostatic latent image thus formed is increased, said uniform irradiation being of greater intensity than said irradiation of the selected portions.