Instrumental analysis of gloss and micro-gloss variations in printed images

Gloss characteristics of printed images contribute significantly to visual image quality. However, traditional gloss instruments provided limited information about first surface optical characteristics of printed materials. In the current work, several new instrumental techniques for characterizing gloss and gloss variations in printed images have been developed. These instruments use a radiometrically calibrated digital camera to capture gloss images of printed surfaces that can be resolved spatially to provide micro-gloss information. The unique characteristics of the instrument is in the illumination optics. Illumination is not done with a traditional collimated source at an equal/opposite angle. Rather, the illumination system modulates the light spatially in such a way that much more quantitative information about gloss can be extracted from the images. The instrument quantitatively separates diffusely reflected light from the first surface light. The first surface gloss can then be related quantitatively to the physical topography of the surface.