Design of a variable diffractive zoom lens for interferometric purposes

We present the design of a compact zoom-lens for the realization of a space-limited interferometer objective with a large range of possible sphere radii. Based on the idea of Alvarez to change the lens-power by shifting two glass plates with cubic surface functions along their lateral axis and the implementation with diffractive optical elements by Lohmann, we realized a focal shift between 200 and 360 mm with two elements in a single shift setup. Additionally, astigmatism can be compensated by moving the plates in the related orthogonal direction as required for the measurement of anamorphic, aspheric, or freeform lenses. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)