The present paper discusses the subject of an RGB optimization for color data coding. The current RGB situation is analyzed and those requirements selected which exclusively address the data encoding, while disregarding any application or workflow related objectives. In this context, the limitation to the RGB triangle of color saturation, and the discretization due to the restricted resolution of 8 bits per channel are identified as the essential drawbacks of most of today's RGB data definitions. Specific validation metrics are proposed for assessing the codable color volume while at the same time considering the discretization loss due to the limited bit resolution. Based on those measures it becomes evident that the idea of the recently promoted RGB definition holds the potential of being qualified as a global RGB data standard without imposing restrictions in regard to feasible surface colors. Optimizing strategies are thus suggested and adapted to the RGB concept focusing on 8 bits per channel. The resulting RGB makes it possible to store a color value to a 32 bit word, yet covering the entire gamut of all existing surface colors at a resolution above the perceptible limit for any color sector, thus satisfying the requirements of a universal RGB, which is particularly optimized for color image data encoding.

Display characterization, deriving the relationship between the digital input values and the corresponding CIEXYZ tri-stimulus values, is necessary to reproduce accurate colors in a color management system. For colorimetric reproduction in a display device, an inverse characterization process is needed to input RGB corresponding to the desired tri-stimulus values. However, inverse display characterization using nine channel tone response curves (TRCs) cannot be directly inverted because the CIEXYZ values corresponding to each RGB value are inseparable. Inverse display characterization is usually implemented using the three-dimensional (3D)-look-up table (LUT) method, yet this requires a lot of memory space and a considerable amount of measurement data, although it provides a relatively accurate estimation. Accordingly, this paper proposes an inverse characterization method based on modeling channel-dependent values and a nine-channel inverse process using the gain-offset-gamma (GOG) model. First, the initially normalized luminance values for each RGB channel are computed using the inverse matrix. These normalized luminance values are then used to compensate the corresponding nine channel TRCs, thereby modifying the TRCs into input linearized values for the inverse process. Thereafter, each of the nine channel digital RGB values is estimated using the inverse GOG model based on the pre-determined parameters from the forward characterization. Finally, three digital RGB values are deduced for each RGB channel based on the ratio of the maximum CIEXYZ values to reduce the interpolation error. Consequently, the proposed method enhances the accuracy of the display characterization and reduces both the complexity and the number of measurement data required.

The dye sublimation transfer process, which allows continuous density gradation, is a process by which an image quality close to that of silver halide photographs can be obtained. However, deviations in process characteristics lead to deterioration in gradation characteristics in the highlight area and degradation in the image quality, such as color saturation and tone jumping in the highlight area. This paper describes a highlight error diffusion method for improving the gradation characteristics of highlight areas and stabilizing the microdensity, which will become an issue when implementing the method in a dye sublimation process. This method involves an algorithm that corrects the amount of heat applied to pixels based on the average density near those pixels. The proposed method improves gradation characteristics of the highlight area without visually recognizable granularity.

A digital gray scale image generally consists of 256 different gray tones. Printers and image setters normally generate much fewer levels and mostly only two levels. Therefore, in order to be able to display a digital cone-tone image by a multilevel device it has to be transformed into an image with fewer levels. The technique doing this transformation is called multi-level halftoning, and in the case of bilevel devices it is simply called halftoning. In this paper we propose a novel (bilevel) halftoning technique that is based on multilevel halftoning. The proposed method can also be categorized as belonging to hybrid amplitude modulated (AM)/ frequency modulated (FM) techniques. In this method the original digital image is firstly halftoned by a multilevel FM halftoning. Each level in the multilevel halftoned image is then replaced by a halftone table (microcell). An approach for extending any bilevel FM halftoning method to a multilevel method is also presented in this paper. The performance of the proposed method is examined by a number of illustrations where nonmodified error diffusion and our FM method are used. The problem with maze-like artifacts that occur when our FM halftoning, or similar methods such as DBS, are used as the macroscreen is discussed and a simple solution is introduced. An approach for extending the proposed method to be used in situations where the halftone dots cannot be produced smaller than a specific size is also proposed and examined. This modified version of the method can be useful for flexography, where the dots normally cannot be produced smaller than a critical size.

Electronic Paper has been studied as a new medium that appears to offer the advantages of both active displays and paper. A twisting ball display system is a promising candidate technology for Electronic Paper. Dielectric balls with colored hemispheres (black and white) are used as the display elements; each color has a different surface charge. Each ball can be rotated by applying the appropriate electric field. However, obtaining the ideal balls (those that show good rotation characteristics) is a remaining problem. This study proposes a way of clarifying the best ball configuration. Ball mobility is measured in a dielectric liquid under uniform electric fields. Experimental results show a strong relation between the mobility difference between the materials covering the ball and its angular rotation speed.

The bubble dynamics induced by direct laser heating is experimentally analyzed as a first step to assess the technical feasibility of laser-based ink jet technology. To understand the interaction between laser light and ink, the absorption spectrum is measured for various ink colors and concentrations. The hydrodynamics of laser-generated bubbles is examined by laser flash photography. When an Ar ion laser pulse (wavelength 488nm) with an output power up to 600 mW is incident on the ink solution through a transparent window, a hemispherical bubble with a diameter up to ∼ 100 μm can be formed with a lifetime in the range ∼O(10 μs) depending on the laser power and the focal-spot size. A parametric study has been performed to reveal the effect of laser pulse width, output power, ink concentration, and color on the bubble dynamics. The results show that the bubble generated by a laser pulse is largely similar to that produced by a thin film heater. Consequently, the present work demonstrates the feasibility of developing a laser-actuated droplet generation mechanism for applications in ink jet print heads. Furthermore, the results of this work indicate that the droplet generation frequency is likely to be further increased by optimizing the process parameters.

The effects of printhouse humidity and temperature on shade depths of three typical colors, black, blue, and yellow, are investigated. Cotton, silk, and nylon 6,6 fabrics were used for this study with reactive, acid, and acid dye inks, respectively. Our study found that a change of 10% relative humidity or 10 °c could cause 20% or even more differences in shade depths, although all the other printing conditions were the same. The mechanisms for the variations in shade depths with humidity and temperature are proposed and the possible approaches in minimizing shade variations are recommended.

In this paper, we present an algorithm to estimate the cell counts from cultured rat B104 neuroblastoma cell images. Assuming that cells are alike, the algorithm identifies the representative cell based on processing the sorted size sequence of the threshold-segmented regions. The size of the representative cell is used to estimate the number of cells in each cluster where cells are attached and inseparable. Preprocessing procedures include the homomorphic filtering for improving the evenness of the image background, and gray-level morphologic dilation and erosion operations for filling the hollow cells. Results on the B104 neuroblastoma cell images are provided and compared with the numbers derived from manual cell count by pathologists.

The correlation between organic photoconductor (OPC) thickness and several printer parameters and OPC aging are theoretically analyzed. We found that linewidth changes from varying the charge transport layer (CTL) thickness are analogous to those from adjusting several printer parameters. Thus, the same linewidths and print quality can be achieved by appropriately adjusting those parameters, provided that lateral motion of photogenerated charge carriers during their transit from the charge generation layer to the CTL surface is negligibly small. In particular, it is found that the laser power is required to increase exponentially with respect to an increase in CTL thickness in order to maintain the same linewidths, and the power sensitivity is inversely proportional to the quantum efficiency. In addition, it is found that, under certain conditions, varying the CTL thickness is analogous to adjusting several print engine parameters.

The results of digital printing trials using a Xeikon press on uncoated and coated paper were analyzed using interferometric profilometry to characterize printed paper topography and toner film thickness. Solid print areas were fused at various temperatures, including radiant fusing with and without heated rolls. The overall surface roughness of the prints is slightly higher on the coated than uncoated paper, but is mainly dictated by transferred toner amount and fusing conditions. Increased toner coverage degree, or layer thickness, gives reduced surface roughness, provided the applied fusing power suffices. Increase in radiant fusing temperature yields a decrease in overall print roughness, however, this decrease is more pronounced on coated paper and higher toner amounts. Bandpass analysis of print surface roughness shows that short-scale roughness at or below the lateral length scales of toner particle dimensions always decreases with increasing radiant fusing temperature, whereas roughness contributions at wavelengths above 10 μm can increase, with this transition value being shorter on coated paper and at lower toner amounts. Print gloss after radiant fusing is strongly correlated to print roughness on wavelengths up to this transition length scale, and the correlation can extend to order 100 μm if complemented by heated roll fusing.