Control of the Focal Depth by Annular Phase-Only Pupil Filters

The general scalar diffractive theory for Gaussian beam has been investigated. The two-zone and three-zone annular phase-only pupil filters are adopted to provide specific numerical descriptions of improvement of DOF, respectively. The simulated results show that the annular phase-only pupil filters can be used to control the DOF of the optical system. For the well designed filters they can help improve the DOF in the axial direction and increase the resolution in the transverse direction, simultaneously. However, the Strehl ratio of the optical system maybe decline and the side-lobe to peak intensity ratio will increase with the improvement of the DOF which is hard for the optical imaging. Comparison results show that the two kinds of three-zone annular phase-only pupils have the same impact on the control of the light intensity distribution.