Patent ID: 8488098

Claim:
A phase-type diffraction device comprising: a substrate having a front surface and a rear surface; and a solidified liquid crystal layer formed on the front surface of the transparent substrate and constituted by a continuous film containing at least a liquid crystal compound; wherein the solidified liquid crystal layer is constituted by first, second and third regions arranged periodically, the third region being interposed between the first region and the second region; the first region is optically anisotropic and the second region is optically isotropic; the third region is not optically isotropic, a degree of orientation of mesogens of the liquid crystal compound being lower than that of the first region; and an in-plane average refractive index n i of the second region is different from an in-plane average refractive index n a of the first region and the third region has a value between n i and n a as an in-plane average refractive index n m .