Cooperative execution of auto-focusing metrics in digital lensless holographic microscopy for internal-structured samples.

The cooperative execution of two metrics to automatically determine the best focal plane in digital lensless holographic microscopy (DLHM) is presented. This proposal is comprised of two stages: first, a quick coarse search over the whole reconstruction range by using Dubois's metric allows the finding of a range in which the best focal plane can be found. In a second stage, the modified enclosed energy (MEE) metric is used within the found range in the former stage to finely determine the best focal plane. While this cooperative implementation keeps the proven effectiveness of the MEE in DLHM, it reduces by at least 11 times the total computational complexity of the auto-focusing method with respect to the MEE method only. This proposal has been validated experimentally with DLHM holograms of a paramecium specimen, polystyrene beads, and the section of the head of a Drosophila melanogaster fly.