Variable resolution with pupil masks

There are many applications in which pupil-plane masks are useful for point-spread-function (PSF) apodization or superresolution. A limitation of this technique is that once a mask is fabricated, the corresponding PSF characteristics are fixed. To overcome this drawback we introduce a technique for easily varying the performance of pupil-plane masks. This technique is based on the modification of the transmittance of each of the mask zones and, thus, can be implemented using a spatial light modulator or linear polarizers, e.g., we apply the technique to binary phase-only masks and we check that the figures of merit that characterize the PSF can be easily controlled. We study different configurations that allow us to modify resolution or peak intensity in a continuous way and we derive analytical expressions for these figures of merit.