Diffractive elements of variable optical power and high diffraction efficiency.

The generation of diffractive elements of variable optical parameters and high diffraction efficiency is presented. It can be realized by a superposition of two conjugate kinoforms. In particular, the method gives rise to zone plates of variable focusing power as well as to circular and linear gratings of variable deflection angles. The theoretical description is illustrated by an experimental example of the blazed grating with a changeable period; some possible applications are mentioned.