Characterizing aberration of a pressure-actuated tunable biconvex microlens with a simple spherically-corrected design

► A tunable biconvex microlens of 1000 μm diameter is micromachined. ► The back focus length tuning range is demonstrated from 35 mm to 250 mm. ► Zoom ratio of up to seven is achieved without any mechanical moving components. ► A facile design to compensate spherical aberration based on differential thickness. ► Proposed microlens can be used potentially in medical imaging systems.