Method Of Digital Holography For Three-dimensional Micro-structured Surface Topography

The extensive application of micro-structure objects needs high precision, fast non-destructive measurements to measure the surface topography information of them. Digital holographic imaging as a new technology, combined with traditional optical holography and post-digital image processing of computer, are widely used in the field of surface topography measurements of micro-structure objects. This technology becomes a new hot research area. Digital holographic measurement can obtain the surface topography of micro structure of objects with no damage, non-contact, high resolution, fast processing characteristics. By recording the hologram, we can obtain the phase map, which can quickly and accurately reflect the three-dimensional topography of the surface of the object. These unique advantages are just right for the topography measurement of the micro-structure objects.This paper focuses on the digital holography imaging measurement method of micro structure surface. This paper also discusses the basic theory of digital holographic imaging measurement, and use the method of dual-wavelength and single wavelength in the experiment.This paper describes the basic principles of the digital holographic imaging technology, and investigates the use of digital holographic measurement on the three-dimensional surface Topography measurement of transmission and reflection type of micro-structure of objects. Digital holography with dual-wavelength phase unwrapping are analyzed in theoretical simulation, and the advantage of dual-wavelength phase unwrapping for micro-structure objects is demonstrated in the experiment. In the experiments of the dual-wavelength digital holographic measurement on a transmission type micro-structure object, we correct the phase effects caused by the experimental conditions, and implement three-dimensional topography measurement on the micro-structure surface. And then, the altitude variations of three-dimensional micro-structure surface are obtained according to reconstructed phase values, which is consistent with that measured by Professional equipment. For reflective objects, we study single-wavelength digital holographic measurement techniques. by using off-axis digital holographic reflecting imaging system, we measure three-dimensional topography of the back of the DVD disc, and obtain the right three-dimensional topography information.