Gloss Granularity of Electrophotographic Prints

The random variation in gloss often observed in images produced in electrophotographic printers has been examined by an analytical technique that combines the capabilities of a microdensitometer with a goniophotometer. The technique is called microgoniophotometry and measures both the spatial and the angular distribution of the specular component of reflected light. The analysis provides information about the spatial variation of specularly reflected light at all angles through which the specular light is reflected, not just at the equal/opposite angle at which gloss is traditionally measured. The results of this analysis have lead to an optical model of the random spatial variation in gloss. The results indicate that dry toner is typically not completely fused and can be described as a surface composed of two distinct regions. These two regions differ in the extent of fusing that has occurred, as manifested by their differences in specular reflectance characteristics. The difference in reflectance is manifested primarily in their different angular distributions of specular light and also in their spatial frequency.