Optimized asymmetrical tangent phase mask to obtain defocus invariant modulation

Wavefront coding as an optical–digital hybrid imaging technique can be used to extend the depth of field. The key to wavefront coding lies in the design of suitable phase masks to achieve the invariant imaging properties over a wide range of defocus. In this Letter, we propose another phase mask with a tangent function to enrich the odd symmetrical kind of phase masks. The performance of the ta