Abstract: A method to compute diffractive elements focusing in a set of lines located in different focal planes along the optical axis is considered. A phase nonlinearity is applied to the phase function of a focusator in a line. It is proven that the selection of the nonlinearity is reduced to the problem of the phase diffraction grating with pre-set energy distribution in the orders. Combined multi-focal elements to focus in two sets of lines simultaneously are considered as well; the first consists of lines located in one plane and the second of lines located in different focal planes along the optical axis. !14
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