The Aberration Characteristics of Wave-front Coding System for Extending the Depth of Field

Wave-front coding involves the insertion of an aspheric phase mask to the pupil plane of an optical imaging system so as to achieve a final image with extended depth of field, when combines with decoding of intermediate image by digital processing. By using method of the stationary phase, an approximate expression of modulation transfer function (MTF) for wave-front coding system with cubic phase mask is derived while multiple aberrations are taken into account, and aberration characteristics are comprehensively analyzed. The analysis results show that spherical aberration will bring MTF degradation and vibration, but existence of defocus, astigmatism, or field curvature will improve such condition.