A System Based On White-light Interference Microscopy For3-D Surface Topography Measurement

With the developments of scientific research and advanced manufacturing technology,varieties of surface appear constantly to meet the demands of different functions, and theyhave been developing for the characteristics of surface from conventional statisticalcharacteristic to the personalized structure characteristic, for the shape of surface from simplegeometric surface to free form surface, and for the accuracy of surface from micrometer tonanometer. Those developments put forward new higher requirements for surface topographymeasurement technology. A microscopy system for3-D surface topography measurement isdeveloped based on the combination of white-light interference technique and phase shifttechnique, which is suitable for the structured surface, such as shoulders and slots, and so on.In this paper, a system based on white-light interference microscopy for3-D surfacetopography measurement is built. LED white-light is used in the system to avoid the heatinginfluence coming from halogen tungsten lamp; the grating positioning measurement device isconstructed to improve the accuracy.The local linearity characteristic of PZT is investigated,and a novel sampling strategy of the interference image is proposed based on it. Case studyshows that the improved sampling strategy can ensure the accuracy while improving themeasurement efficiency greatly.The integrated software for the white-light interferencemicroscopy measurement system is developed based on VC++6.0platform, which consists offive modules, image acquisition, positioning data acquisition,3-D topography recovery,3-Dtopography display and parameters for evaluation of surface profile. Four algorithms havebeen compared for3-D surface topography recovery, which are extremum method, gravitymethod, spatial frequency domain method and phase shifting method, and the extremummethod is employed. Experiments have been carried based on the measurement system, theresults show that: horizontal measurement range:880um×700μm; vertical measurementrange:36nm; horizontal resolution:0.68μm; vertical resolution:2nm. Experimental results show that profile measurement error is less than5%; the repeatability error of roughnessmeasurement is less than5%.