| 摘要 |
The invention relates to a method of producing a phase device operating at at least one wavelength (?) comprising a cell containing a liquid crystal possessing a helical structure, inserted between two alignment layers possessing rubbing axes and means for applying a voltage to said cell, said helical structure exhibits a number of helical turns k, said liquid crystal exhibiting a defined angle of twist T between the rubbing axes of the two alignment layers, characterized in that it comprises the following steps: - the determination of a compensation angle e satisfying the following equation: (formula) with: N the integer closest to (formula) the angle of twist T=2Kp-e ?n: the birefringence of the liquid crystal; d: the thickness of the liquid crystal cell; ? : the wavelength of the light beam which passes through the liquid crystal cell; the rubbing of one of the faces in a direction of alignment of said liquid crystal molecules, defining the angle of twist: ? = 2Kp-e. |
