Fourier ptychographic microscopy for extended focus range with conjugated optics

We propose a configuration of Fourier ptychographic microscopy (FPM) to modulate the focus to a large extent. FPM is widely used to obtain high-resolution images in a wide field of view. A conjugation mirror with an axially scannable mirror is introduced to conventional FPM to extend the focus range. The proposed FPM provides a wider field of view with higher resolution compared to general microscopy using the same numerical aperture. In addition, it can measure a wider focus range. Therefore, it is expected to be applied to volumetric samples more easily compared to FPM. The proposed technique is validated by measuring resolution while moving the United States Air Force resolution chart up to ± 2 mm in the axial direction and experimentally verified by measuring a volumetric sample with a depth of 4 mm created using bead with 1 μm of diameter.