We introduce a simple method to determine the in-plane birefringence of transparent flexible films by using transmission spectroscopic ellipsometry. The pseudo-ellipsometric constants which can represent their sample azimuthal angle dependent characteristics are introduced. The effect of in-plane birefringence and sample azimuthal angle on the pseudo ellipsometric constants is calculated using Jones matrix formalism, and the observed sample azimuthal angle dependence of measured pseudo-ellipsometric data is well understood. Wavelength dependence of in-plane birefringence is expressed in terms of the Sellmeier dispersion equation. The best fit pseudo-ellipsometric spectra to the measured ones at the sample azimuthal angles of every 15°from 0 to 90°are searched. The dispersion coefficients of the Sellmeier equation and the azimuthal angle of the optic axis are determined for polycarbonate (PC), poly(ethylene naphthalate) (PEN), poly(ethylene terephthalate) (PET), polyimide (PI), and colorless polyimide (CPI) films.

The anisotropic properties of polyethylene terephthalate film resulting from its manufacturing process are quantitatively investigated in terms of its optical, mechanical, and photoelastic aspects. Transmission ellipsometers and a Jones-matrix-based analysis software together with a 4 × 4 Berreman-matrix-based analysis software are adopted to determine the wavelengthdependent in-plane birefringence, the principal refractive indices, and the orientation of the optical axis. Mechanical anisotropy is characterized in terms of the elastic compliance tensor components using the measured azimuthal angle-dependent Young's modulus and Poisson's ratio. From the measured variation of the wavelength-dependent in-plane birefringence as a function of tensile stress, the dispersive photoelastic coefficients are obtained for a few sample azimuthal angles, and the components of the photoelastic tensor are determined.