Jae Sung Lee

Plane wave illumination for correct phase analysis and alternative phase unwrapping in dual-type (transmission and reflection) three-dimensional digital holographic microscopy

The digital holographic microscope (DHM) has emerged as a useful tool for verifying the three-dimensional structure of an object. A dual-type inline DHM that can be used with both transmission and reflection imaging in a single device is developed. The proper modes (between transmission and reflection imaging) can be easily changed according to the characteristics of the object in this system. The optimum condition for retrieving the correct phase information is illuminating a plane wave to an object. In contrast to the transmission imaging, it is difficult to illuminate an object using a plane wave without deformations in the reflection imaging. We developed an adequate relay lens module for illumination that can be adapted to any type of microscope objective without significant aberrations in the reflection imaging. The relationship between the illuminating condition and the measured phase based on the wave optics is analyzed. A specially designed and manufactured phase mask is observed in this system, and an alternative method for overcoming the limitation of phase unwrapping is introduced for the inspection of that object.

Wavefront error analysis and compensation in a digital holographic microscope

Digital holography (DH) has a big advantage to retrieve the three-dimensional (3D) information of the object from only one interference recording. Especially, the digital holographic microscope (DHM) using a microscope objective (MO) has been researched for 3D microscopy. The researches have progressed for compensation of aberrations and improvement of the resolution in the optical system in recent years. Most of small aberrations caused by a MO are compensated through various researches. However, the measured phase is distorted in the optical system, which has the significant wavefront deformation in illuminating wave larger than number of wavelengths. In this paper, the relation between illuminating wave and the reconstructed phase is studied based on the wave optics and the analysis is confirmed by the simulations. The analysis of the wavefront compensation is applied to a super-resolution DHM in theory and the technique for retrieving the distribution of the intensity and phase is demonstrated in simulation.