The Fundamental Study On Material Surface Topography Measurement Based On Digital Holography

Digital holographic measurement technology is an important methodology of none-contact surface measurement, which is combined with conventional optics and modern computer image processing technology together. It mainly uses high resolution photoelectric sensor(CCD or CMOS)to replace the conventional holographic plate to record the hologram, and then the hologram is reconstructed and processed rapidly by computer to achieve the goal of measuring the surface of the object. Due to the characteristics of none-damage, high resolution, none-contact and high efficiency, digital holographic measurement technology has been an effective methodology in many fields,such as material surface measuring, deformation measuring and biology study.The research is mainly conducted based on surface measuring of transparent object using digital holographic measurement technology. Firstly, the basic theory of digital holography is analyzed, including two kinds of fresnel algorithm and convolution algorithm, which are basic reconstruction algorithms. And then, digital holography imaging, hologram recording and reconstructing are simulated in computer. Secondly, the theory of phase unwrapping is shown. It discusses basic phase unwrapping and least square phase unwrapping and using MATLAB to simulate the process.Theoretical analysis and scheme of using physical experiment are adopted to test optical experiment in the paper. First, the basic theory of measuring material surface by digital holography is introduced and the feasibility of the process is verified by computer simulation. Second, a digital holographic experimental setup is established to test standard target and a droplet water on glass slide. The phase distribution can be obtained and then converted to height distribution information by a series of image processing.Finally, material surface information can be obtained. At the same time, Scanning three-dimensional contour instrument is used to make a comparison. By analysis and comparison, Digital holographic measurement technology is an effective method used to measure material surface.