An autofocus technique for imaging microscopy

The authors present an automatic focus (autofocus) technique for imaging microscopy. The technique successfully finds the optimum focus position for large working distance/small depth of focus optics. High throughput is realized by a combination linear-to-nonlinear digital signal processing algorithm. The optical design allows for focusing on image planes where no inherent image information exists. The optical design, the signal capture technique, the functional relationship between the definition of goodness-of-focus and objective to image distance, and how the algorithm exploits this functional relationship to achieve fast autofocus are described