Extension of depth of field using amplitude modulation of the pupil function for bio-imaging

摘要

In this paper we present a novel approach to generate images of extended depth of field (DOF) without compromising the lateral resolution to support realization of three-dimensional imaging systems such as integral imaging. In our approach in extending DOF, we take advantage of the spatial frequency spectrum of the object specific to the task in hand. The pupil function is thus engineered in such a fashion that the modulation transfer function (MTF) is maximized only in these selected spatial frequencies. We extract these high energy spatial frequencies using PCA method. The advantage of our approach is illustrated using an amplitude modulation and a phase modulation example. In these examples, we split the pupil filter and choose the optimum transmission/phase value of each section in the filter in a way that the response of the system in all the DOF range as well as spatial frequencies of interest is optimized. Consequently, we have optimized the DOF extension process with blocking the minimum possible area in the pupil plane. This maximizes the output image quality (e.g. 10% DOF improvement) compared to the existing methods where non-optimal blocking of the lens area may cause more degradation in output image quality. Experimental results are presented to illustrate our proposed approach.