US Patent 7369327 Variable optical-property element and optical apparatus including the same

A variable optical-property element includes a liquid crystal the pitch of twist is less than 60 times the wavelength of light used, so that a spatially uneven electric or magnetic field or temperature is applied to the liquid crystal to thereby form an index distribution, and the electric or magnetic field or the temperature is changed to thereby alter the index distribution. In this way, the variable optical-property element is capable of changing its optical properties as a liquid crystal lens and is used in an optical apparatus.