Micro-alvarez lenses for a tunable-dynamic-range shack-hartmann wavefront sensor

Alvarez lenses (AL) consist of a pair of aspheric surfaces such that their relative lateral displacement results in tunable lenses from positive to negative powers. In applications requiring a range of only positive powers, the use of AL results in an inefficient use of the lens size. In this work, we introduce a basic design methodology by showing formulas to shape the surfaces to overcome this problem. On the other hand, a tradeoff between the sensitivity and dynamic range of a Shack-Hartmann wavefront sensor (SHWS) occurs when choosing the largest focal length of the lenslet array that allows each spot of the sensor to remain in the field of view of its lenslet. On the basis of the proposed formulas, the design parameters to construct an array of micro-ALs for a Shack-Hartmann sensor with a variable dynamic range are also given.