Development of an Auto Focusing Stacker for Photomicrography of Marine Microorganisms

Most marine microorganisms and fossils have transparent outer shells, low contrast, and three-dimensional stereo configurations. Their delicate external morphology and fine structures provide an identification reference for taxonomic classification. However, because of the limitation of low focal depth at high magnification, presenting a refined image and contour of a specimen in a single image is impossible. This study describes the development of an autonomous focus stacking device dedicated to photomicrography of marine microorganisms and fossils. The customized device is equipped with a motorized fine-focusing mechanism, a control software interface, stacking software, and a digital single-lens reflex camera mounted on a stereomicroscope. Practical use of the device has resulted in greatly reduced operating time and error in the acquisition of photomicrographic images. Additionally, the depth of field of the photographs significantly improved without sacrificing image resolution. The use of an autonomous focus stacker extends photomicrography applications to digitization and observation of marine microorganisms and microfossils.