Laser intensity modulated, time dependent exposure is calculated analytically using a diode circuit model. We found that the exposure of individual pulses with different intensities can be spatially superimposed by scaling the exposure based on the intensities. However, when the beam stays on and changes its intensity, this scaling method is no longer appropriate since there is no contribution from the fall time when the intensity changes. In this case, exposure calculation must be carried out from time dependent intensity equations with the current and previous asymptotic intensity levels and the intensity just before the beam changes its intensity. Different exposure integrals are solved separately depending on the relative magnitude of the current intensity. An iterative procedure for calculating the resultant exposure of a pulse with an arbitrary number of intensity modulations is presented and demonstrated.

Lateral motion of charge carriers at the photoconductor surface is numerically calculated and analyzed. Surface conduction is assumed to take place in a very thin surface charge layer. Our findings, based on the assumption that surface conduction is the predominant factor for image blurring, lead us to believe that the carrier mobility at the surface is field dependent, and consequently surface conduction is not Ohmic, although it has the appearance of being so after a sufficient amount of time has elapsed. Using a field enhanced surface mobility, time-dependent dynamics of photogenerated charge carriers as they arrive at the surface and begin to spread out in the surface charge layer are accounted for by empirically approximating vertical charge motion with an exponential rise expression that closely mimics the behavior of the carriers as they reach the surface. We found that vertical charge motion has a negligibly small effect on surface conduction over a period of time relatively long compared to the vertical transit time of the carriers, and surface conduction can remove jaggedness inherent in certain features. A developed toner mass (DMA) estimation procedure is presented using electric fields and potential in the developer gap. Quantitative comparisons between measurements printed from a test print engine and calculated toner mass arising from surface conduction are made using different input bitmaps, which are in good agreement. Our DMA calculation procedure can account for variation in surface conduction rate and it is validated using two toner cartridges of significantly different surface conduction rates.

An experimental and analytical investigation has been performed on vibration induced in a driving mechanism of a photoconductor drum in a color laser printer. The mechanism consists of a flywheel supported by a dry journal bearing and driven through a belt and a pulley that is connected to a shaft of the photoreceptor drum. From the results of the investigation, the following characteristics were deduced: (1) Pulley runout induced a vertical harmonic pull force to the flywheel through the belt and caused the vibration of the flywheel. (2) When the pull force is large enough to support the flywheel, the shaft of which is always in contact with the stator ring of the dry bearing, the harmonic vertical forced vibration takes place by the harmonic vertical force due to the eccentricity of the pulley through the belt. (3) On the other hand whirling takes place when the pull force is low. The shaft vibrates in the air gap not only in vertical but also horizontal directions. (4) The driving mechanism must be constructed to have small runout of the pulley and sufficient static tension of the belt.

Optimum toner charging and mass transfer are important factors to produce fine images with high quality in electrophotography. Also the uniformity of the image is one of the most important properties to produce high quality printing. The charging mechanism of toners and the mechanism of toner development in the electrophotographic monocomponent laser beam printer system was studied in this article. Development rollers with various surface properties were prepared. The dynamics of toner charging were investigated by using a current measurement technique. A current was observed to flow through each system part, i.e., development roller, blade, and supply roller, during the roller rotation with toner attached on its surface. Currents and toner charge to mass ratio and the uniformity of printing image were measured for each roller. It was found that the current had a strong relationship to the roller surface properties. It was also shown that the relationship between toner charge and roller surface properties is related to the uniformity of printing image. Finally the mechanism of toner development is discussed, and the design of a high quality development roller is proposed.

Liquid toners have been used in the development of electrostatic images in digital printing since the midfifties. In this article, several models are discussed that were introduced to explain the processes responsible for charging toner particles. The acid-base models had to be extended by equilibrium models describing dynamic dissociation, adsorption and desorption. The important role of water traces in non-aqueous media for the dissociation of molecules and stabilization of ions was investigated. Later, electrical conditions were considered to explain specific high field effects by additional charge generation and relaxation processes. The focus of this article is on the models developed for the charging mechanisms. The enormous progress in measurement techniques that was necessary for improving and, in some cases, correcting the models is not described in detail here nor are models concerning practical issues in printing.

Time dependent layer-by-layer toner development in AC biased monocomponent systems is numerically simulated. For a given gap length, a uniform toner cloud is assumed to be formed in the gap prior to initial development. The normal electric field in the toner cloud is obtained by taking the two-dimensional Fourier transform of the spatial potential and subsequently taking the negative gradient of the potential. The field is then used to determine the locations of toner deposition in each toner layer, whose thickness is obtained from the average toner particle size. As the photoconductor (PC) rolls away from the developer, the effective gap length increases and the sinusoidal AC bias oscillates. The time dependent effective gap length as a function of PC rotation angle is calculated using conformal mapping techniques. Our development calculation is carried out iteratively until the developed layers from the positive and negative peaks of the AC bias stabilize. Simulation results using different input bitmaps are presented and analyzed.

This study is aimed at determining the effect of the minute liquid compressibility on the flow of ink in a piezo-diaphragm driven Drop-On-Demand (DOD) ink jet nozzle. This goal is achieved by a comparison between the results obtained numerically for compressible and incompressible flows by means of Computational Fluid Dynamics calculations. In these calculations the exact geometry of the entire flow channel is modeled. Significant differences between the two flow models are observed in many aspects of the flow and drop evolution characteristics. Also, in some cases, seemingly similar features have been found to result from different physical driving forces. Despite the low Mach number and low condensation values involved, the very slightly compressible flow and the incompressible flow are very different. It is concluded that acoustic effects cannot be ignored and the incorporation of ink compressibility in the physical analysis of this flow system is essential.

The accuracy of scanner characterization is usually affected by two factors. First, the statistics may vary for individual color samples and, second, the behavior of the scanner may depart from the linear reflectance model. This article proposes a method of colorimetric and spectral characterization for a color scanner using local statistics to deal with these problems. The experimental results showed that the proposed method significantly outperforms one using global statistics. The color accuracy of the colorimetric characterization is slightly better than that of the spectral one, while cross-media metamerism exists for both methods.