A NOVEL OPTICAL MEASUREMENT METHOD FOR THE DETERMINATION OF LC PRETILT ANGLE WITHOUT A RESTRICTION OF PRETILT MAGNITUDE AND A CELL GAP OF LC

To measure a pretilt angle in liquid crystal cells, a crystal rotation method is commonly used because of its advantages such as high precis ion, short measurement time and small measurement area The method, how ever, has the restrictions on measurable pretilt range and available c ell thickness; pretilt in the range of about 16 similar to 60 degrees cannot be measured and the cell thickness should be larger than about 10 mu m. We developed a new pretilt measurement method without the res trictions of cell condition. In our new method, a pretilt angle is det ermined from a specific polarization direction of incident light, for which either ordinary or extraordinary wave is excited inside the cell . This method permits us to easily and accurately measure the pretilt angle in full range of 0-90 degrees.