Studies Of Digital Holography With Applications To Microstructure Topography Measurement

With the fast development of the micro-machining, the technology ofmicrostructure topography information obtained becomes an increasing concernedsubject. Digital holography is a technology that combines the digital technology andtraditional optical holography, the hologram generated by object is recorded directlyby CCD and stored digitally by computer, and then reconstructed numerically. Andintensity as well as phase information of a holographically stored wavefront can beachieved directly in the numerical reconstruction process. Digital holography is ahigh-resolution, quick, non-contact and non-invasive, and easy measurementtechnique and now has been developed into the prospect of a powerful new tool formicrodomain measurement and becomes an increasing and wide attention in variousfields.This paper centering about the application of object surfect topographymeasurement with digital holography is studied, and the basic theory of off-axisFresnel digital holographic system and the off-axis Fresnel digital holographic systembased on 4f for topography measurement have been analysized and experimentalresearch have been also done. The main contents of this paper are as follows:1. The basic theory of digital holography for surface topography measurementhas been analysized.2. The method adjusting the reconstructing light carrier frequency coefficientand the reconstructed distance in digital holography is analyzed theoretically.The method determined the reconstructing light carrier frequency coefficientby looking for the space-frequency center of object is presented, and thegood reconstructed images of digital holography are been obtained. Thesimulation analysis and the experimental validation have been completed.The method that decides the reconstructed distance in numericalreconstruction with the algorithms of "Grey level local variance", "Entropy"and "Tenengrad" has been also proposed, and theoretical simulation hasbeen done.3. The method that eliminates the disturb from a parabolic phase factor toobject's phase information by using the image character of 4f system hasbeen presented and a optics system of off-axis fresnel digital holographybased on 4f system has been designed.4. The experimental research of off-axis fresnel digital holography and off-axisfresnel digital holography based on 4f system has been done based on thetheories.