392 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 42, NO. 2, MARCH/APRIL 2006 Simulating Digital Exposure of Xerographic Photoreceptors Using the Domain-Decomposition Method P. S. Ramesh, Member,IEEE Abstract—In digital electrophotography, the photoreceptor (PR) is discharged by exposing it to a high-intensity laser beam from an imager for a very short duration in an imagewise fashion. The resultant latent image on the PR surface is a function of the PR properties, the imager properties, as well as the spatial and temporal exposure sequence. A generalized computational model for discharge based on charge generation, injection, and transport in a PR has been discussed previously (Proc. SPIE, vol. 2658, p. 112, 1996). In this paper, the use of the domain- decomposition method to enable an efficient simulation of a latent image for wide-area exposures (such as wide lines and solid areas) is discussed. A photo-induced discharge curve (PIDC) with a multibeam imager is simulated using this algorithm. The simulation results show that laser exposure sequence can create an inhomogeneous field on the generator layer, which may lead to varying amounts of charge injected at the generator layer for the various scan lines. However, the impact on the discharged image is reduced since charges in transit appear to reequilibrate spatially. The photo-induced discharge is somewhat less efficient (10–15 V for exposures greater than 5 ergs/cm 2 for results presented here) due to a two-beam interlaced exposure sequence compared to the case when all the pixels are exposed simultaneously. Simulation results for discharge of lines show that narrow positive lines grow due to the field dependence of collection efficiency during charge generation and subsequent spreading of charges in transit. A single-pixel positive line, for instance, can grow as much as 40%. The effect is less pronounced for wide lines. Index Terms—Charge injection and transport, computational electrostatics, electrophotography. I. I NTRODUCTION I N DIGITAL electrophotography, the photoreceptor (PR) is discharged by exposing it to a high-intensity modulated laser beam from a raster output scanner (ROS) for a very short duration in an imagewise fashion. An excellent review of the physics of electrophotography, including the exposure subsystem, may be found in [1]. Fig. 1 shows a schematic of the raster scan pattern for generating an image. An ROS writes an image by scanning repeatedly across a PR (in the fast-scan direction) as it is moved under the beam of an ROS. High-speed printing requires that the ROS be able to write the image on the Paper MSDAD-05-40, presented at the 2004 Industry Applications Society Annual Meeting, Seattle, WA, October 3–7, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Elec- trostatic Processes Committee of the IEEE Industry Applications Society. Manuscript submitted for review October 15, 2004 and released for publication December 27, 2005. The author is with the Wilson Center of Research and Technology, Xerox Corporation, Webster, NY 14580 USA (e-mail: pramesh@xeroxlabs.com). Digital Object Identifier 10.1109/TIA.2006.870041 Fig. 1. Raster scan pattern in both fast- and slow-scan directions used for generating an image in the machine shown on top, and the scan pattern only in the slow-scan direction used for generating a PIDC shown on the bottom. PR faster. This has led to the development of a multibeam ROS, where the image is written in parallel by using two or more beams spaced apart by a multiple of the pixel spacing. In digital electrophotography, several effects arise due to the interaction between the ROS and PR, which impact the overall system performance. One effect, often referred to as charge spreading, is a loss in resolution in the latent image due to the mutual coulombic repulsion of the charges in transit in the PR during the discharge. Another effect is the field dependence of the collection efficiency of the PR (defined as the ratio of charges responsible for discharge to the incoming photons), due to which the charge generated is itself spatially different from the incident ROS exposure profile. Kasap et al. [2] have discussed the mathematical models for charge generation and transport in PRs. A general computational framework for sim- ulating charge generation and transport in PRs, including the effects of charge spreading and field dependence of collection efficiency on the latent image, has been outlined in [3]. This framework allows arbitrary space and time dependent one dimensional images to be laid down in the fast-scan direction (i.e., perpendicular lines), and enables the study of the in- teraction between the ROS system parameters, such as laser wavelength, resolution [spots per inch (spi)], spot size and ex- posure profile, and the PR design parameters, such as thickness, mobility, and collection efficiency. 0093-9994/$20.00 © 2006 IEEE