An algorithm is proposed for the spectral and colorimetric characterization of digital still cameras (DSC) which allows them to be used as tele-colorimeters with CIE–XYZ color output, in cd/m². The spectral characterization consists in the calculation of the color-matching functions from the previously measured spectral sensitivities. The colorimetric characterization consists in transforming the raw RGB digital data into absolute tristimulus values CIE–XYZ (in cd/m²) under variable and unknown spectroradiometric conditions. Thus, in the first stage, a gray balance was applied over the raw RGB digital data to convert them into RGB relative colorimetric values. In the second stage, an algorithm of luminance adaptation versus lens aperture was inserted in the basic colorimetric profile. Capturing the ColorChecker chart under different light sources, and comparing the estimated XYZ data according to the developed color model in relation to the measured XYZ data (in cd/m²) using a tele-spectroradiometer, we verified that the proposed characterization model may be broken down into two portions. Firstly, there is the basic colorimetric profile in combination with the new luminance adaptation algorithm. Secondly, there is the linear correction term due only to the mismatch of the color matching functions of the camera. Although the linear color correction term works relatively well, despite the imposed initial conditions (unknown spectral content of the scene), the separation of the proposed characterization model into two portions (raw and corrected performance) would allow the future comparison of various commercial cameras.

This article summarizes two recently developed patterning techniques for plastic electronics: microcontact printing and thermal transfer printing. It reviews the methods and their capabilities, and presents new results on their use in forming transistors and circuits with a range of organic semiconductors. Active matrix backplane circuits for large, mechanical flexible sheets of electronic paper and other display devices represent one class of realistic application whose patterning requirements can be satisfied with current versions of these printing approaches.

Digital Paper was recently proposed as a new medium that offers the advantages of both softcopy and hardcopy. This study examines the possibility of realizing Digital Paper by using an ion projection head to drive a liquid crystal medium. A guest-host type liquid crystal sheet medium is prepared. An ion projection head with charge dot density of 300 dpi is used for surface charging. It is confirmed that white images could be repeatedly formed on a black background by ion projection followed by image erasure (by heating) to the black background. It is demonstrated that this sheet medium has ideal characteristics; it reproduces the viewing angle and flexibility of paper. This method is thus promising as a candidate for realizing Digital Paper.

Experiments have shown that multitoning with output levels equally spaced in CIE L^* does not produce uniform texture at different gray levels. In this study, psychophysical experiments are described, investigating the influence of spatial modulation on the perception of lightness difference. A variety of different patterns (square wave, checker-board, and 50% blue noise patterns) were tested at various frequencies and amplitudes (contrast). A significant frequency dependent effect was observed where the lightness difference perception is reduced for high frequency modulated gratings at low L^* values. The magnitude of this effect is highly related to the frequency of the modulation. There is no evidence to indicate that either modulation type or modulation amplitude has a significant effect on the lightness difference perception. Based on the experimental results, an effective lightness metric (L_e^*) is derived as a function of spatial frequency. The L_e^* metric is intended to provide a space that is linearly related to lightness difference perception for frequency modulated patterns. Results from a further visual experiment have verified that multitoning patterns produced using levels that are equally spaced in L_e^* produces results with more uniform texture visibility across the entire tone scale.

In amplitude modulated halftoning, Moiré refers to the low frequency textures created by superimposing the monochrome halftones of cyan, magenta, yellow, and black inks. Recently, a stochastic Moiré phenomenon has been discovered that accounts for the low frequency graininess created by superimposing frequency modulated (FM) halftones. A particularly interesting property of stochastic Moiré is that it is most visible when overlapping FM patterns are uncorrelated and are of equal intensity. So in a printer that cannot guarantee perfect alignment in the component screens, the only way to minimize the visibility of Moiré is to introduce clustering such that two overlapping dither patterns of equal intensity have different principal frequencies. In this article, we introduce an adaptive error diffusion halftoning algorithm that produces green-noise dither patterns with coarseness varying according to color content.

An experimental analysis of paper optical scattering is reported. The Kubelka-Munk parameters for scattering, S, absorption, K, thickness, L, and background reflectance, R_g, were measured for a variety of papers. Measurements were made of reflectance and transmittance using integrating sphere techniques, and the Kubelka-Munk Eqs. were inverted numerically to generate the corresponding S and K values. The modulation transfer function, MTF, of each paper sample was also measured by projecting a sharp edge onto the paper and measuring the resulting edge spread function. The MTF was calculated as the modulus of the Fourier transform of the derivative of the edge function. The inverse of the frequency at which the MTF = 0.5 was used as an index of the MTF and called κ_p. Values of κ_pwere compared to values of the Kubelka-Munk parameters. Through a combination of theory and empirical observation, a model was developed to relate κ_p to S, K, and L for R_g = 0. The results strongly indicate that an additional parameter is required in order to rationalize the observed MTF of papers. This additional parameter is suggested to be the scattering homogeneity of the paper.

Gloss, as has long been known, is a visual concept far more complex than the present methods of instrumental gloss evaluation are able to characterize. A newly developed measurement principle for gloss characterization gives perceptually relevant gloss information. The characterization results in a “Reflectance Vector Map” (RVM) which simultaneously contains spatially resolved information about directed reflectance and apparent inclination. The experimental phase of the present study uses the RVM and a rudimentary model of a virtual optical environment to interactively visualize a simulated surface. The performance of the visualization environment has been evaluated by comparing results from two visual assessments of perceived gloss homogeneity for a limited but demanding set of black printed paper surfaces. Assessments were performed both on the physical surfaces, and on the computer generated visualizations of the same surfaces, reconstructed from the corresponding RVM's. The results correlate well, with a less inter-judge variance in the visualization environment than with the physical surfaces. It is suggested that this visualization environment may be a powerful tool for gloss assessment, able to mediate perceptually important characteristics of gloss.

Oil-in-water microemulsions which contain a hydrophobic colorant were evaluated as water based ink jet inks.These microemulsion based ink jet inks are thermodynamically stable, have the features of dye based inks prior to printing, and the features of pigment based inks after printing. The microemulsion was prepared and printed, as described recently by Magdassi et al.^1,2 using the gemini-type surfactant, didodecyldiphenylether disulfonate, toluene, 1-propanol, water as the continuous phase and Nile Red or Sudan IV as the hydrophobic dye. Microemulsion average droplet size was measured by dynamic light scattering and found to be ∼8 nm. We found by AFM imaging that the printed 20 – 60 μm droplets are composed of nanoparticles with average size of 130 nm. The printing process was evaluated by a fluorescence microscope, while images of the droplets were viewed as a function of time after impact with the substrate. It was found that the microemulsion droplets formed distorted spheres on ink jet paper, more perfectly shaped spheres on Forbo paper substrate and perfect round spheres on vinyl slides. When printed on glass, a ‘bagel like’ shape was obtained. The droplet size varied, depending on the surface energy of the substrate, being at least 20 μm for low energy surfaces and growing larger for higher energy substrates. It was noticed that the time scales for spreading on paper was less than tens of milliseconds accompanied and followed by fixation and drying of the droplets in less than 3 – 5 seconds.

A series of novel copolymers having components with hole transport ability and silane functionality have been synthesized. These copolymers were prepared by radical polymerization. Through a sol-gel process with methyltrimethoxysilane, solutions of the copolymers were coated to form the hole transport layer of an organic photoreceptor. These hole transport active silsesquioxane layers were coated as either a charge transport layer (CTL) on a charge generation layer (CGL) or a protective overcoat on a CTL. The electrophotographic and scratch resistant properties of the photoreceptors prepared with these sol-gel layers are described.