High-speed autofocusing of multisized microobjects

This paper proposes a new high-speed autofocus algorithm for observing multisized microobjects under a transmitted light microscope. The method estimates the blurriness of the object by analyzing the intensity variation of a defined region around the object border in the frequency domain. A defocus function is proposed so that the best focused position of the object is found when the defocus function reaches its minimum within the close region around the focal plane. Experiments for execution time and accuracy evaluation have been performed to compare its performance to other autofocus algorithms. Experimental results showed that the proposed algorithm outperformed other algorithms in terms of execution time and accuracy and that it is more robust to environmental change.