We introduce a modified Monte Carlo model of light scattering in paper for better understanding of optical dot gain origin. Using a realistic description of paper as a scattering medium and assuming that light distribution in paper (generally any homogeneous or inhomogeneous substrate) depends on its optical properties, we tried to determine light distribution inside paper with known optical properties. In our description, absorption and scattering coefficients of all paper constituents were taken as key functions insofar as they contribute in a real printing application. Due to the fact that paper is a complex medium, it is necessary to involve, in calculations, its surface structure, which was modeled on the base of microfacets. Depicted phenomena were observed and calculated in transmission and reflection. Agreement of the statistical light scattering model in a complex substrate with experimental data demonstrates that the new method successfully describes the phenomena of interest.

The electrical and dielectric properties of paper are important parameters in electrophotography, influencing both toner transfer and runnability in laser printers and in digital printing machines. These parameters are dependent on the ionic content and moisture content of the substrate. The effects of NaCl content of the substrate and the ambient relative humidity (RH) on the direct current resistivity in different electric fields and on the real part of the dielectric constant and dielectric loss factor at different frequencies have been investigated with experimental papers of different grammages. A physical model of electrical conductivity in papers with ionic addition is proposed, based on the hypothesis that ionic addition not only increases the number of available free ions but also changes the water state and the paper structure, which influence the ionic motion in an electric field. This model is supported by the dependencies of the real part of the dielectric constant and the dielectric loss factor on the NaCl content, RH, and frequency.

Particles of electrophotographic toner (black, silica-coated, number-weighted, and volume-weighted median diameters of 6.5 and 8.0 μm, respectively), having two different charge levels (nominally 30 and 55 μC/g), were electrostatically developed on the surface of a film of bisphenol-A polycarbonate coated on nickelized polyethylene terephthalate. The thickness of the coatings varied from 0.8 to 22.0 μm. The force needed to remove the particles was determined using ultracentrifugation. We found that removal of half of the particles from the film surface required a force of approximately 200 nN for all charge levels and film thickness except for the highest charged particles on the thinnest film. These results indicate that, for toner particles of this size, which typically have a charge of approximately 20-25 μC/g, adhesion is dominated by van der Waals interactions. However, for highly charged particles, electrostatic interactions can also significantly contribute to the adhesion forces.

An Al-complex with salicylic acid derivatives as ligands (commercial product E-88 from Orient Chemical Industries) is a typical commercial charge-control agent (CCA). At present, E-88 is widely used for full color toners, since it is colorless. However, E-88 possesses a relatively low and broad decomposition range between 130 and 170° C. For this reason, an attempt has been made in the present study to improve the thermal stability by investigating a new polymorph that possesses a higher thermal stability. Trial was then made to grow crystals by recrystallization from solution in various solvents. Among these, dimethylsulfoxide gave a hexanuclear Al-complex (molecular weight: 3310) that exhibits an extraordinarily high decomposition temperature of 270° C. In addition, this compound is found to exhibit excellent charge-control performance. Furthermore, the temperature dependence of the electrical conductivity of E-88 has also been studied in connection with our previously proposed charge-control mechanism of CCAs.

Thermal printing plates based on novolak, a phenol-formaldehyde condensation polymer, are now used by some 80% of the printing industry worldwide. Until recently, the image discrimination of these plates; i.e., the difference in the dissolution rate between exposed and unexposed areas was only moderate. About three years ago it was discovered that treatment of the plates with water vapor substantially improves image discrimination. This treatment is now an important manufacturing step, but there is no generally accepted explanation of the water vapor phenomenon. We venture to offer such an explanation and are exploring its consequences for the performance of the thermal plates.

To acquire a high dynamic range (HDR) image of a scene, several low dynamic range (LDR) images acquired from a digital camera with different exposure times are generally fused into one HDR image to cover the entire dynamic range of the scene. However, when capturing a scene, the scene dynamic range (SDR) is unknown. Consequently, the exposure times for the LDR images need to be as varied as possible to cover the unknown SDR. This paper proposes a method to estimate the SDR using two LDR images. Using the SDR information, SDR-adaptive exposure times can then be selected to achieve the optimal HDR image. The SDR is defined as two exposure times when captured LDR images are marginally clipped to black and white, indicating the lower and upper limits of the SDR, respectively. To identify these times, two LDR images, an overexposed and an underexposed image, are captured. Using the opto-electronic conversion function of the camera used, the minimum gray level in the overexposed image is then used to estimate the exposure time to make the minimum gray level of the image just black, while the maximum gray level in the underexposed image is used to estimate the exposure time to make the maximum gray level of the image just white. By evaluating the acquired HDR image error according to the exposure times of fused LDR images for various scenes, SDR-adaptive exposure times to acquire an optimal HDR image with the minimal error are selected. Experiments confirm that the quality of an HDR image based on fusing LDR images with the proposed SDR-adaptive exposure times is similar to that of an HDR image based on fusing LDR images with conventionally chosen exposure times, even though the number of LDR images used to acquire the HDR image with the proposed method is much smaller than that used by the conventional method.

This paper presents a new method for tracking moving objects with radical color changes using modified mean shift. The mean shift algorithm seeks the highest density value using a mean shift vector obtained from the density gradient. Density presents various forms of object information such as color and intensity depending on the application. Conventional color-based mean shift methods show good results when tracking nonrigid moving objects. However, they do not provide accurate results when the initial color distribution of the object disappears. In our method, color distribution is used to represent the objects. The mean shift algorithm is first used to derive an object candidate by estimating the maximum increase in density direction from its current position. Next, the color variation of the object is calculated and compared with a specific threshold value. When the color variation of the object exceeds this threshold value, the initial color of the search window is updated. The objective of our method is to provide for robust real-time object tracking with large color variation in the object whose color changes during motion. The implementation of the new algorithm shows effective tracking results with complete object color changing from time to time. Validation of our approach is illustrated by comparison of experimental results obtained using the methods described above.

The problem of extracting small retinal blood vessels using a Canny edge detection method is addressed. It shows that using the Canny edge detector to detect retinal blood vessels, especially small vessels, can be significantly improved if an adaptive edge detection filter is incorporated. The filter is designed as a local dynamic hysteresis thresholding value generator. It adapts knowledge of the location of major vessels to define a small neighborhood and to generate the local hysteresis threshold values to detect meaningful edges, especially the edges of small blood vessels that may be missing, using Canny edge detector alone. The effectiveness of the adaptive edge detection filter is demonstrated by the preliminary experimental results obtained with the proposed method. A comparative test is also presented to highlight the performance differences between the Canny edge detector with the adaptive edge detection filter and the one without the filter.