Reproducing Gloss Unevenness on Printed Paper Based on the Measurement and Analysis of Mesoscopic Facets

In this article, the authors reproduce gloss unevenness on a paper surface by expanding the Torrance–Sparrow model, which is based on the measurement and analysis of mesoscopic facets on paper. As the conventional Torrance–Sparrow model only considers macroscopic and microscopic facets, the authors expand the model to be able to consider mesoscopic facets. The normal vectors of mesoscopic facets on a paper surface were measured by using a collimator lens system with a small pinhole aperture, and the authors obtained the normal vector map by moving the stage for the paper. Gloss unevenness was reproduced by generating the same probability distribution as the measured distribution of the normal vectors. As a result, the authors succeeded in reproducing gloss unevenness using an expanded Torrance–Sparrow model. c © 2014 Society for Imaging Science and Technology. [DOI: 10.2352/J.ImagingSci.Technol.2014.58.3.030501] INTRODUCTION Gloss is an important quality of printing paper. Gloss is a specular reflection phenomenon, i.e., an optical phenomenon. Many reflection models have been proposed, and practical applications are used in computer graphics.1–5 In conventional simple reflection models, it is assumed that all microscopic facets have the same statistical properties; therefore, these models render a homogeneous gloss reproduction. However, the gloss that appears on paper is not homogeneous in real life. A number of measurement technologies have been developed and reported to evaluate the gloss.6–13 Some of them, in particular, have reported measurement technologies and evaluation methods with respect to gloss on paper.14–17 Conventionally, gloss is evaluated as averaged behavior on the surface of paper. A typical evaluation method is standardized for use with gloss in the Japanese Industrial Standards (JIS). 1Part of this article was presented at the IS&T CIC20 conference held in Los Angeles.