Determination of the Jones matrix of an LC cell and derivation of the physical parameters of the LC molecules

摘要

The wavelength-dependent Jones matrix representation of a twisted-nematic liquid crystal (TN-LC) cell contains four independent parameters. The absolute values of these parameters and two mutual sign relationships can be determined from comparatively simple transmission measurements of the TN-LC cells sandwiched between two rotatable polarizers. The physical parameters of the cell (twist angle a, director orientation Ψ, birefringence β) can be retrieved if the Jones matrix is known for more than one wavelength. We have measured the Jones matrices of the TN-LC cells of a translucent Sony LCX-016 microdisplay for six wavelengths ranging from 488 nm to 1064 nm and determined the physical parameters of the cell. We have also measured the Jones matrices for one wavelength for a number of applied voltages. These experimental results show that it is not sufficiently exact to calculate the Jones matrix from the known physical parameters of the cell assuming a voltage-dependent birefringence only. We attribute the deviations from the theoretical model to edge effects which are not taken into account. The direct experimental determination of the Jones matrix components is therefore preferable and permits a more accurate simulation of the TN-LC microdisplay in experimental configurations involving other polarization-dependent optical components.