We have applied the light-scattering equation caused by liquid-crystal (LC)-director fluctuations as derived by De Gennes  to the case where the polarization direction of the incident light is at an arbitrary angle with respect to the LC directors within the cell. Based on the De Gennes's equation, we have used an out-of-plane (OPR) cell-rotation method to measure the pretilt angles of a tilted-homogeneously aligned LC cell. Our measured pretilt angles are in good agreement with that obtained by the published OPR-rotation method  based on a different mechanism. Our method is simple in setup and requires no complicated data-fitting calculations when the pretilt angles are below about 30 degrees. In addition, there is no need to know cell parameters except the ordinary and extraordinary refractive indices of the LC medium at the wavelength of incident light.
- Nematic liquid crystal; light scattering; director fluctuations