High speed tomographic measurement systems for the transparent thin layered structures

Abstract

Transparent thin layered structure which is made by industrial fabrication process is widely adapted for the semiconductor, flat panel display, LED and solar cell industry. On the other hand, certain regions of human tissue such as retina, esophagus and heart vessels consist of thin layered structure with homogeneous cells. Therefore, it has been attempted to develop measurement tools to investigate the physical and chemical properties of thin layered structures. Among them, the optical measurement method is fascinated by high-speed cross-sectional measurement capability without destructing a sample. Thus, the optical method to investigate the thin layered structure has a big potential for the industrial and clinical applications. The thesis is mainly devoted to the improved intereferometric systems for the measurement of thin layered structures. The improved optical measurement systems based on the fiber-based and full-field imaging interferometry are proposed for the two kinds of layered structures, respectively: in-vivo human retinal imaging and volumetric thickness profile of thin films. The SNR improvement was focused on the fiber-based spectral domain OCT system by using the pulsed illumination and the adaptive optics. Lastly, a simultaneous measurement method for the total interference and self-interference of a sample is proposed. The proposed method is capable of making separate measurements of the three-dimensional thickness and surface profile of micro-patterned thin film. The system is an extension of a full-field wavelength scanning interferometer with a single acousto-optic tunable filter (AOTF) as a spectral imaging device. Separate measurements are realized via the polarization-sensitive diffraction of non-collinear acousto-optic interaction. That is, the diffraction angle of an AOTF is separated into different directions depending on the polarization state of the incident light. In so doing, the polarization states of a reference and a sam...