Nondestructive, three-dimensional refractive-index measurements are used for the determination of both the crystallinity and orientation in thin polymer films. The prism wave-guide coupler is particularly suited for three-dimensional isotropic and anisotropic thin-film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to determining only the refractive index of transparent or weakly absorbing thin-film samples. On the basis of thin-film optics, this study develops a new internal reflection intensity analysis (IRIA) method, which uses the intensity information rather than the conventional mode angle values to acquire both the refractive index and the extinction coefficient over a range of transparent to highly absorbing polymer films. Therefore, the IRIA method overcomes the limitations of this prism wave-guide coupler technique, which can only measure the refractive index of a weakly absorbing sample. With a Metricon PC-2010 as the skeletal framework, a prototype instrument has been developed to apply and test the IRIA method. A study comparing both the refractive index and extinction coefficient obtained with ellipsometry, ultraviolet-visible/near-infrared reflectometry, and IRIA for solvent blue 59 dyed polystyrene films confirms that the IRIA method is effective for obtaining the three-dimensional refractive indices and extinction coefficients of polymer films. In addition, the refractive index and extinction coefficient spectrum (400-800 nm) of solvent blue 59 have been determined with the effective media theory. Furthermore, the three-dimensional complex refractive indices of highly absorbing black electrical tape, inaccessible to other optical measurement because of its surface character, has been determined by the IRIA method. (C) 2003 Wiley Periodicals, Inc.