디지털 홀로그래피를 이용한 인장시험편 파단면의 표면조도측정

Abstract

Holography involves recording a modulated form of a desired object wave. It is also known as wave front reconstruction. The resulting device is called a hologram. This technique is more commonly known as diffractive. Some other terminologies used for diffractive optics are computer-generated holography, diffractive optical elements (DOEs), and binary optics. Holography was first discovered by Dennis Gabor in 1948, which is before the invention of the laser. Being a communications engineer, he recognized that the intensity resulting from the sum of a desired wave and a reference wave carries the information on both the amplitude and the phase of the object wave. Digital holography enables the storage of the whole optical wave field by a complex vector component proportional to electric or magnetic vector. The reconstruction is performed by the numerical simulation of the diffraction of the reference wave at the hologram in most of the cases. Holographic imaging depends on a number of parameters such as wavelength and CCD pixel size and reconstruction distance. Holography is now used widely as a display medium. In addition, it is firmly established as a tool for scientific and engineering studies, and has found a remarkably wide range of applications for which it is uniquely suited. For example, measure of height and movement in a cell, X-ray application, measurement for the determination of material quantities, evaluation of the refractive index, dis6tance shape control. However this application just used the medical and biology industry. According this thesis is expended the field in a metal material of machine. For reconstruction of specimen, the hologram is need to expressed parameters and reconstruction basic theory. There are three main reconstruction algorithms most widely used. Each method has different properties with respect to available reconstruction distance, resolution of reconstructed image, and computational load. This is very important for reliable reconstruction to choose the appropriate method in a given situation. In a accordance with, the reconstruction algorithm for this thesis is choose the angular spectrum method. Because this method correctly reconstructed near wavefields for more diffractive that the micro variation of object surface. In this thesis, the variation of outside condition is appeared to the temperature and volume, surface roughness of specimen. In the accordance with, the evolution is detected to Infrared camera and charged coupler device(CCD), system of Michelson interferometer. This condition is associated with each other. The thesis found it the association. That research isn't attempt to other technician so it has important things. The analysis of experiment will explain the next contents. Firstly, the tendency of volume variation according to temperature was measure liner. So the variation of temperature increase fracture moment. Also the surface roughness of fractured surround district increase abruptly because of fracture influence. Secondly, the fractured surface roughness isn't has variation in the changed tensile speed. This result explained which that roughness according to changed tensile speed influence the surround district. Third, the analysis explain the specimen surface appear to necking situation. Also using the above analysis data measured necking position. Lastly, the temperature and surface roughness are detectable in the required distance of fractured surface. In this thesis, the specimen variation according to outside condition measured the quantitative evaluation. The system of interferometer measured 10-9 unit. So, the micro variation and crack of object will be detectable. That result is very useful in the nondestructive testing method in industry.