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 tangent phase mask is evaluated by comparison with a cubic mask, improved-1 logarithmic mask, improved-2 logarithmic mask, and sinusoidal mask. The results demonstrate that the tangent phase mask has superior performance in extending the depth of field.
© 2014 Optical Society of America
Original Manuscript: January 8, 2014
Revised Manuscript: March 5, 2014
Manuscript Accepted: March 6, 2014
Published: March 31, 2014
Van Nhu Le, Shouqian Chen, and Zhigang Fan, "Optimized asymmetrical tangent phase mask to obtain defocus invariant modulation transfer function in incoherent imaging systems," Opt. Lett. 39, 2171-2174 (2014)