A correlation between psychophysical and physical assessment of sharpness based on toner scatter
The use of color electrophotographic (EP) laser printing systems is growing because of their declining cost. Thus, the print quality of color EP laser printers has become increasingly important. Since toner scatter in color EP laser printers can significantly impact print quality, coring, defined as a process whereby the colorant level is reduced in the interior of text or characters, is introduced to preserve edge sharpness by reducing toner scatter. The desired amount of reduction for coring depends on line width and overall nominal colorant level. Contrary to physical assessment, cares must be taken to conduct psychophysical assessment due to the possibility of greater uncertainty and complex process. But yet, it should be noticed that the perceived data from a human viewer cannot be replaced with the physical measured data, in terms of acceptability to the end-user of imaging products. Therefore, the measured data by physical assessment should be correlated with the perceived data by psychophysical assessment.^ In the first chapter, we describe psychophysical studies to directly establish optimal coring values as a function of line width and nominal colorant level. For each line width and nominal colorant level, this is done by asking human subjects to choose the minimum amount of coring that is necessary to eliminate the perception of toner scatter. We conduct four separate psychophysical studies to address different aspects of this question.^ In the second chapter, we exploit the previously published psychophysical data based on perceived toner scatter. For physical data, we apply the Edge Transition Width (ETW) between T90(&thetas;) and T10(&thetas;) boundaries as a line metric to measure sharpness and the Weighted Differential Toner Spread (WDTS) within the region between T¯60 and T¯05 boundaries to measure the spread of toner scatter. Utilizing both perceived and measured data, we predict preferred coring level to reduce toner scatter in electrophotographic (EP) printing.^
Jan P. Allebach, Purdue University, Zygmunt Pizlo, Purdue University.
Engineering, Electronics and Electrical
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