A binary phase-Only Pupil masks for extending the depth of field of a microscopy

A binary phase-only pupil mask with "0, pi" phase rings is placed on the plane of the aperture to modulate the wave front of the traditional microscopic imaging system, the modulation transfer function curves, obtained by the annular ring aperture applied to the pupil of the imaging system, do not change much within the required depth of field range, therefore, the loss of system's imaging information is avoided, meanwhile the depth of the field is enlarged. The Zemax simulated result shows that it is able to make the depth of field of microscopic imaging system extend 10 times to adopt this method.