Ionic wind occurs with corona discharge. Knowledge of the ionic wind in a machine is necessary for a measure of the degradation of the image that originates from the generation products on corona discharge. We investigate the characteristics of the ionic wind in the neighborhood of a corona device through Computational Fluid Dynamics to better understand this phenomenon. Various flow characteristics have been found. A λ-shaped flow appears on a cross section in the fan-off case. Several vortices are induced by the λ-shaped flow. Static pressure descends along the wire. We also find three-dimensional features. There is a countercurrent at both ends of the corona device. Momentum is axially transported. Our numerical calculations correlate well with our experimental results by Particle Image Velocimetry (PIV) and smokes. The λ-shaped flow appears also on a cross section in the fan-on case, while the flow rate of the whole system is hardly changed. The ionic wind locally has an influence on the flow field in the neighborhood of the corona device.

The relationships between the triboelectric charge to mass ratio (Q/M) and volume ratio (Q/V) of a monocomponent magnetic toner and the properties of magnetite incorporated in the toner were studied. To remove the influence of the development system on toner charging, the triboelectric charge of the magnetic toners against an iron oxide powder carrier was measured. Several kinds of magnetite differing in their particles size and shape were used, and the concentrations of magnetite in the toner were changed from approximately 5 to 55 wt%. The Q/M and the Q/V decreased proportionally with an increase in magnetite concentration. The Q/V decrease means the Q decrease for the same diameter toners. The relationships between the Q decrease and the number of magnetite particle and the total cross-sectional area of magnetite particles on a toner surface for same diameter toner group were analyzed. The result suggests that total cross-sectional area and surrounding area of magnetite on a toner surface has no triboelectric charge. In conclusion, the Q can be represented as Q = Q₀ × (1 − S_m/S), where, Q₀ is charge for the magnetite free tonerS is surface area of a toner, and S_m is the total effective cross-sectional area of magnetite on a toner surface.

A unique color fusing technology using induction heating has been developed, which has been adopted in a newly released one-pass color laser printer. The color fusing unit consists of a thin fusing belt made of heat resistant resin containing metal, a heating roller with low thermal capacity, a fusing roller, and a pressure roller to press the fusing roller with the fusing belt in between. An induction heater is disposed along and adjacent to the outer circumference of the fusing belt and heating roller. The newly developed fusing belt has a low thermal capacity, with a thickness of only several hundred micrometers, and has a structure that self-heats at high efficiency, since eddy currents are generated inside the belt by electromagnetic induction. In addition, the eddy currents generated by the alternating magnetic field heats the heating roller. This design shortens the warm-up time of the fusing unit from cold start to only 20 sec. This color laser printer eliminates the need to preheat the fusing unit during stand-by time by employing the induction heating technique and achieves energy saving of 90% or more compared with conventional printers.

Radiant fusing in the wavelength range between 500 nm – 10 μ m (visible – far infrared (IR C)) with continuous radiation or pulsed radiation has been used in copying and printing since the early days of commercial application of electrophotographic technology. We have evaluated the use of high intensity continuous and flash radiation for color independent radiant fusing and have chosen the UV range from 200 nm – 380 nm (UV-C – UV-A) of the spectrum which combines high intensity and low color dependency. We discuss matching of emission spectra of lamps with absorption spectra of the toners by fuser modifications, process and toner material optimization. In duplex fusing of prints for two-pass duplex electrophotographic engines, the paper goes through the fusing station twice, with the risk of reheating the first image above the softening point. Radiant fusing requires non-contact paper feeding in the heating zone followed by a non-contact paper feeding in the following cooling zone. In flash fusing we demonstrated that backside temperature of the substrate stays well below critical temperature so that conventional contact paper transport means like Kapton® belts are sufficient for duplex color flash fusing of sheet materials. Finally we discuss the potential of the technologies for future toner based high speed color production printers.

Print life estimation of consumer prints has historically been based on endpoint criteria defined in terms of changes in density (loss of density). This methodology has served the conventional silver halide community well for many years. The robustness of these endpoints for several new output technologies (thermal dye transfer, ink jet, electrophotographic) was evaluated. Also, how well the current endpoints correlate to customer judgment of print acceptability is evaluated. This paper will discuss a psychophysical study conducted to determine if the current metrics, based on changes in density, are robust over several technologies and correlate well with customer judgments of print acceptability. Eight output systems from six distinct output technologies were used to assess the current endpoint criteria. Customer judgments of 16 scenes at 25 levels of degradation were correlated to objective metrics based on densitometric measurements of color tonescales. The data show that the current endpoint criteria are not robust over the digital output systems included in this study when compared to the results of the psychophysical study and are therefore inadequate for comparing print life estimates across the various digital output technologies.

Focusing on subtractive color dyes currently used in dye-based color ink jet printers (IJs), we consider that it is important to increase the size of color gamut on high quality coated paper in particular. Development of the optimum subtractive color dyes will rely on full understanding of the relationship between dye amounts placed on the paper and resultant colors. In a previous study, the author verified that models were able to be used to predict the colorimetric gamut of a hypothetical dye set. Among the models, the Kubelka-Munk equation (KM) which relies only on the spectral reflectances of the primary colors achieved reproducible performance for the color gamut on coated paper used in a dye-based color IJ. Based on this result, the present study has used KM for prediction of the color gamut of a hypothetical dye set. The color gamut has been calculated by means of computer simulation, and the optimum combination of three dyes for a dye-based color IJ has been solved by constrained nonlinear programming. Moreover, the color gamut has been compared between the optimum three dyes obtained in this study and typical C, M and Y dyes for a dye-based color IJ. The result showed that the area of the color gamut obtained by the optimum combination of three dyes was only 1.1 times larger than that by the typical C, M and Y dyes, and the optimum peak wavelengths and absorption bandwidths depended on lightness.

Given the subtractive color dyes currently used in a dye-based color ink jet printer (IJ), it is important to increase the size of the color gamut, especially on high quality coated paper. In a previous study, the author obtained, by means of a computer simulation, the optimum three dyes in order to maximize the size of color gamut. The result showed however, that the color gamut obtained by the optimum three dyes was only 1.1 times larger than that obtained with typical C, M and Y dyes for a dye-based color IJ. This result proves that the typical C, M and Y dyes currently used in a dye-based color IJ achieve good performance for reproducible color gamut. By extension of the previous study, it is now important to know whether an increase from three dyes to four dyes is an efficient way to expand the size of color gamut. In this study we solved for the optimum four dyes for maximizing the size of color gamut, again by means of a computer simulation. The color gamut obtained with the optimum four dyes has been compared with that by the typical C, M and Y dyes for a dye-based color IJ. The result showed that the optimum four dyes achieved a desirable level of performance for reproducible color gamut.

A printer characterization attempts to map, in both directions, corresponding points in colorant and colorimetric spaces. Two limiting approaches are used: analytical models based on a small number of samples, and direct measurement and interpolation requiring many samples. For six-color printers, the former approach often has insufficient accuracy whereas the latter approach requires an excessive number of samples. An intermediate approach was used to characterize a CMYKGO ink jet printer, the Cellular-Yule-Nielsen-Spectral-Neugebauer (CYNSN) model. This model included an optimized Yule-Nielsen n value and onedimensional look-up tables between digital data and effective area coverage for each colorant. Each colorant was divided into three subspaces, or cells, requiring the selection of two intermediate values and fixed endpoints of 0% and 100% effective area coverage. An optimization was performed that determined these intermediate values by minimizing the maximum spectral error when one-colorant CYNSN models were used to predict 256-step ramps. This technique enabled a considerable reduction of the total number of required samples from several hundreds of thousands to 4,096, the required number of cellular Neugebauer primaries. Of these colors, only 1,024 could be printed; the remainder was non-printable due to inkblots. A third optimization synthesized the spectral properties of the non-printable cellular primaries using weighted spectral regression, the weighting a function of colorant-space location. The CYNSN model based on these three optimizations was able to predict 600 random colors sampling the colorimetric gamut to an average spectral RMS error of less than 0.5% and ΔE₀₀ of less than 1.0. The color gamut achievable using the synthesized spectra was 54% larger in colorant space and 15% larger in CIELAB space than that achievable when limiting the CYNSN model to printable cellular primaries.

We investigate the efficiency of color similarity measures in the context of color classification tasks. Color similarity measures are categorized into three major types: Point-type CSMs for classifying colors by absolute value, diffuse reflection component based CSMs for classifying “body colors” of object surfaces made of dielectric materials, and dichromatic reflection component based CSMs for classifying colors that include both the diffuse and the specular reflection component. First, the results of an evaluation of existing color similarity measures with regard to their ability to separate color classes using more than hundred test cases of the background-frame-differencing type are reported. It was found that especially two of the existing color similarity measures (S₇ and S₈) have good properties with respect to brightness, saturation and hue changes, and that they have a compact scalar field structure in RGB space. In addition, they have the largest margin for class separation. Second, we propose several new color similarity measures of the diffuse reflection component based color similarity type and report on the results of an evaluation regarding their class separation ability using more than 50 test images (for facial skin color classification). It was found that two color similarity measures (S₁₃ and S₁₄) perform best for separating color classes when the colors are treated as body color reflections. The properties of these measures with respect to brightness, saturation and hue changes are not perfect, but nonetheless reasonably good, and they have a compact scalar field structure in RGB space. Third, we propose a new color similarity measure of the dichromatic reflection component based type and discuss the problems associated with it. Finally, we introduce a shifted reference color similarity measure which can be used to compute the similarity between colors that may be the result of a systematic shift due to some physical phenomenon.