Study on elimination of twin image in a combined dual-type digital hologram microscope system

摘要

Holography has a considerable advantage to retrieve the three-dimensional (3D) information of an object from only one interference recording. For several decades, the technology of digital holography (DH), which uses numerical reconstruction as opposed to illuminating the reference beam to the hologram plate, has progressed with the assistance of improvements in 2D array detectors and computers. In this paper, a dual-type inline digital hologram microscope (DHM) system that can be used with both transmission imaging and reflection imaging in a single device is developed. The proper method depending on the modes (transmission imaging or reflection imaging) can be changed easily in this system according to the characteristics of the object. Illumination with a plane wave is the necessary condition for retrieving the correct phase information. In the case of reflection imaging, unlike in transmission imaging, a special relay lens in addition to the microscope objectives (MOs) is needed to meet the needs of this condition. However, the quality of the 3D information can deteriorate significantly due to the overlapping twin image that is inherent in holography. This study suggests an effective and convenient method for eliminating the twin image that is entangled in the reconstructed information. The proposed method does not require extra components, numerical iterations, and restrictions on the object.