Array of Tunable Complex Amplitude Filters for Extended Depth of Field

Certain nonconventional masks are able to reduce the influence of focus errors on the Modulation Transfer Function (MTF). In this manner one can extend the depth of field of an optical system [1-3]. When extending the depth of field, there are two main challenges. First, if one wishes to preserve lateral resolution (associated to the full pupil aperture), then one avoids the trivial solution of closing down the pupil. Second, if one wishes to preserve light gathering power, then one must use phase-only masks. Here, we propose the use of a pair of optical arrays for generating an MTF with low sensitivity to focus errors and with reduced oscillations [4]. The proposed arrays preserve lateral resolution and exhibit a stable MTF as compared with previously proposed filters for controlling focal length and for extending the depth of field. [1] Jorge Ojeda-Castañeda, R. Ramos, and A. Noyola-Isgleas, Appl. Opt., Vol. 27, 2583 (1988). [2] Edward R. Dowski, Jr., and W. Thomas Cathey, Appl. Opt., Vol. 34,1859 (1995). [3] Jorge Ojeda-Castañeda, J. E. A. Landgrave and Cristina M. Gómez-Sarabia, Appl. Opt., Vol. 47, E1-E7 (2008). [4] J. Ojeda-Castañeda, E. Yépez-Vidal and E. García-Almanza, Phot. Let. of Poland, Vol. 2 (4), 162- 164 (2010).