wavefront coding is an effective way to extend the depth of field of an incoherent imaging system. with a suitable phase mask, the defocus invariant imaging characteristic of an incoherent imaging system can be achieved. in this paper, an effective way to generate new type of phase mask is proposed. on the basis of the new method, the inverse sinusoidal phase mask is proposed to enrich the family of anti-symmetric phase masks. the performances of inverse sinusoidal phase mask are evaluated by comparisons with cubic, sinusoidal and tangent phase masks. numerical evaluations demonstrate that the proposed phase mask has superior performance in extending the depth of field and small artifacts in restored images, particularly at large defocus. (c) 2016 elsevier gmbh. all rights reserved.