In the color conversion processing for DTP printer, it was a subject to realize both of preservation of black separation and colorimetric color reproduction. This paper describes the color conversion method of 4 input and 4 output signals for realization both of preservation of black separation and colorimetric color reproduction, and the evaluation results of the color separation characteristic and accuracy in color conversion. The new color conversion algorithm is proposed in this paper, it consists of these 4 parts, (1)L*a*b* color signals transformation from input YMCK signals, (2)output black(K')signal transformation on equal lightness with input black(K)signal, (3)output Y'M'C' signals determination by L*a*b* color signals and K' signal, (4)Y'M'C' signals adjustment to zero when all YMC signals are zero. This algorithm could realize both of preservation of black separation and colorimetric color reproduction, and accuracy in color conversion has been much improved as compared with the conventional method, which guaranteed preservation of black separation.

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High definition full color hardcopy with both high resolution and continuous tone can be obtained by laser dye thermal transfer printing. In this report, a mechanistic study on the dye transfer process during laser heating is conducted and extended to understanding of the continuous tone control feature. The thermal response of an ink layer obtained by time-resolved optical microscopy is explained in terms of the distribution of the energy density which takes into account the diffusion and loss of heat energy occurred in microseconds. On the basis of transient deformation of the ink layer, a simple model to predict the continuous tone characteristics is introduced. The amount of transferred dye calculated based on the model is in satisfactory agreement with that determined experimentally.

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Gold and silver are special colors that generally cannot be identified by physical measurements. This study aims at clarifying the perception mechanism for gold and silver color by a subjective experiment. The dependence of the recognized color on the size of the observation area was examined by placing masks with different aperture sizes on gold and silver objects. One interesting result is that the appearance of a gold (silver) area changes to yellow (gray) when the size of the observation area falls below a threshold. Another result is that the threshold is smaller at peripheral areas that include an object edge than at central areas. This indicates that gold or silver color perception requires the recognition of object configuration, which is easier at the peripheral areas.

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The Imaging Society of Japan has been eagerly seeking new frontiers for study themes since the renaming of the society in 1999. The seventh group in the technical committee of the Imaging Society of Japan has been discussing rewritable imaging technology as a promising area. This report is based on the results of discussions at the committee. It aims to clarify the study direction in this new field and to help this field develop into a major field of imaging technologies. Application fields for the rewritable marking technology are mapped to guide future study in this field. “Digital Paper” is defined as a new medium concept that is expected to have the merits of both hardcopy and softcopy; technology field of Digital Paper is defined as a new category that integrates the conventional fields of rewritable paper and paper-like displays. Three essential advantages that can be expected from this new medium are listed: the first one is enhanced readability, the second one is usage unrestricted by location or position, and the third one is a tight linkage to digital information. The physical forms of Digital Paper fall into four groups: plate style, scroll style, book style, and paper style. It is suggested that the key advantage of Digital Paper over conventional paper will be its breakage of the restrictive linkage between medium and information. Anticipated scenes for the usage of Digital paper are listed to encourage the development of many new applications.

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