High-speed 3-D measurement with a large field of view based on direct-view confocal microscope with an electrically tunable lens

We propose a new structure of confocal imaging system based on a direct-view confocal microscope (DVCM) with an electrically tunable lens (ETL). Since it has no mechanical moving parts to scan both the lateral (x-y) and axial (z) directions, the DVCM with an ETL allows for high-speed 3-dimensional (3-D) imaging. Axial response and signal intensity of the DVCM were analyzed theoretically according to the pinhole characteristics. The system was designed to have an isotropic spatial resolution of 20 µm in both lateral and axial direction with a large field of view (FOV) of 10 × 10 mm. The FOV was maintained according to the various focal shifts as a result of an integrated design of an objective lens with the ETL. The developed system was calibrated to have linear focal shift over a range of 9 mm with an applied current to the ETL. The system performance of 3-D volume imaging was demonstrated using standard height specimens and a dental plaster.