The design of the diffractive optical element to focus into a line in noparaxial case

The common analitical expression for the phase function of the diffractive optical element (DOE) to focus into a line in noparaxial case is received. The phase function is given in the special curvilinear coordinates. To calculate the function, that defines the energy distribution along the line, the iteration method is proposed. The calculation of the phase functions of the DOE to focus into the line-segment is produced.