Just as it is difficult for a camera to keep both a nearby flower and a distant mountain sharply focused at the same time, conventional optical microscopes face a similar challenge when imaging structures located at different depths inside the body. Tighter focusing of light improves spatial resolution, but at the same time reduces the depth range over which the image remains sharply focused.

A joint research team led by professors Junsuk Rho and Chulhong Kim at POSTECH has developed a dual-focus metalens-based photoacoustic microscopy system that can switch between different imaging depths simply by controlling an applied voltage, without mechanically moving any optical components. The study is published in Light: Science & Applications.