Paper Gloss Analysis by Specular Reflection Point Spread Function (Part I)

Glossiness is one of the major qualities of coated paper. For example, coated paper is categorized to glossy or matt. Glossiness can be most usually measured using a glossmeter. The standard units for measurement are “specular gloss”.However it is well known that the “specular gloss” values, in some cases, do not correspond to the glossiness by the visual inspection. In this paper, a new technique for measuring the specular reflection light of paper is proposed. We have developed the apparatus to measure the Point Spread Function (PSF) of specular reflection. A pinhole test pattern is projected to the sample paper, and the reflection light intensity distribution is measured by the two-dimensional CCD camera. The specular reflection PSFs of different type of paper were obtained.Results showed that the specular reflection PSFs of paper meet well with the visual inspection glossiness. We discuss the physical meaning of the specular reflection PSF. The specular reflection PSF works as transfer function for specular reflection image, naturally. In future work, we will discuss paper gloss evaluation by using spatial frequency analysis.