A. Elmoataz et al. (Eds.): ICISP 2014, LNCS 8509, pp. 35–42, 2014. © Springer International Publishing Switzerland 2014 Measurement and Modeling of Bidirectional Characteristics of Fluorescent Objects Shoji Tominaga, Keita Hirai, and Takahiko Horiuchi Graduate School of Advanced Integration Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba, 263-8522, Japan {shoji,hirai,horiuchi}@faculty.chiba-u.jp Abstract. A method is proposed for measurement and modeling of bidirectional characteristics of fluorescent objects. First, a gonio-spectro measurement sys- tem is constructed for measuring the spectral luminescent radiance factor of a variety of fluorescent object surfaces. Second, the angular dependency of the luminescence radiance factor is analyzed in different light incidence and view- ing directions. The observed radiance factors can then be described by the Lambertian model with good accuracy. We also analyze the bidirectional ref- lection radiance factor of a white mat surface. The whole characteristics of bispectral bidirectional radiance factors of a fluorescent object can be summa- rized as a compact mathematical model. Finally, image rendering of a fluores- cent object is performed using the Donaldson matrix estimated in a separate measurement system. The feasibility of the proposed method was examined experimentally. Keywords: Fluorescent object, bispectral bidirectional radiance factor, mea- surement and modeling. 1 Introduction The luminescent radiation effect of fluorescent objects improves the visual appear- ance of object surfaces. In particular, many fluorescent surfaces appear brighter and more vivid than the original color surfaces. For this reason, fluorescent materials are important and attractive as research objects of imaging science and technology [1]-[3]. In these days fluorescent substance applies to many common materials, for instance paints, plastics, papers, cloths, or even human teeth. Therefore, the appear- ance of fluorescent objects is analyzed in the field of computer vision and image processing [4]-[5]. The appearance synthesis is studied in computer graphics [6]-[7]. Knowing the bispectral characteristics of a fluorescent object is important. The spectral radiance factor of a fluorescent material consists of the sum of two compo- nents: a reflected radiance factor and a fluorescent (luminescent) radiance factor. Such fluorescent characteristics can be measured accurately by the two- monochromator method [8]. The results of bispectral measurements are summarized as a Donaldon matrix, which is an illuminant independent matrix representation of the bispectral radiance factor of a target object. However the two-monochromator method