Determination of Tilt Bias Angles in Nematic Liquid Crystal Cells by Observing Angular Dependence of Rayleigh Line Intensity

Intensity contours of the Rayleigh scatteering, I (E, E), I (E, O) and I (O, E), have been numerically calculated and graphically plotted as a function of θ and φ which specify the optic axis. Here the two superscipts of I represent the states of polarization, ordinary (O) or extraordinary (E), of the incident and scattered lights, respectively. There exist three points and one line where I becomes zero: I (E, E)=0 for (θ=90^° , φ=α/2) and φ=α/2±90^°; I (E, O)=0 for (θ=90^° , φ=0^°); and I (O, E)=0 for (θ=90^° , φ=α). We have experimentally demonstrated that these zero points and line can be used to determine the optic axis within a few minutes and hence the so-called “tilt bias angle γ” within an accuracy of about ±0.1^°, unless γ is close to 45°.