Real-time digital autofocusing using a priori estimated set of PSFs

Abstract

This paper proposes a real-time digital auto-focusing algorithm using a priori estimated set of point spread functions (PSFs). A priori set of PSFs are estimated by establishing the relation between two-dimensional PSF and onedimensional step response whose elements are samples of profile of degraded step edge. From the priori estimated set, the proposed auto-focusing algorithm can select the optimal PSF by the focusing criterion based on the frequency domain analysis. We then use the constrained least square (CLS) filter to obtain the in-focused image with the estimated optimal PSF. The proposed algorithm can be implemented in real-time because the set of PSFs are already estimated and the filtering is performed in the frequency domain.