Optimized logarithmic phase masks used to generate defocus invariant modulation transfer function for wavefront coding system

摘要

In a previous Letter [Opt. Lett. 33, 1171 (2008)], we proposed an improved logarithmic phase mask by making modificationsnto the original one designed by Sherif. However, further studies in another paper [Appl. Opt. 49, 229n(2010)] show that even when the Sherif mask and the improved one are optimized, their corresponding defocusednmodulation transfer functions (MTFs) are still not stable with respect to focus errors. So, by further modifying theirnphase profiles, we design another two logarithmic phase masks that exhibit more stable defocused MTF. However,nwith the defocus-induced phase effect considered, we find that the performance of the two masks proposed in thisnLetter is better than the Sherif mask, but worse than our previously proposed phase mask, according to the Hilbertnspace angle.