Some Key Technologies And Software System For White Light Interference Based AFM

With the development of advanced manufacturing technology, more and more parts develop toward to the Nano-scale and precision of the surface morphology, such as the optical surface, the lithography surface, the information storage surface and so on. To improve the surface quality, surface topography and structure measurement instruments are needed. White Light Interference based Atomic Force Microscope(hereinafter referred to WLIAFM) the high lateral resolution and vertical sensitivity of atomic force microscope are fully utilized, and high precision of displacement measurement with optical interference, the combination of white light interference and atomic force probe constitutes a kind of nanometer resolution surface topography and structure measuring instrument, which is of great significance. In this paper, some key technologies and software systems of WLIAFM are studied. The main work is exhibited as following:1. According to the position of the white light interference zero-order fringes on the atomic force probe cantilever, an improved extreme method based on range analysis and a new method of combining wavelet analysis with Hilbert transform is proposed. These two kinds of zero-order fringe extraction algorithm are different. The improved extreme method is fast and has high stability compare with simple extreme method, but the accuracy and robustness comparatively not high with envelope curve method. The envelope curve method has good robustness and high precision, but the calculating speed is slower than improve extreme method. Different algorithms can be chosen according to the different requirements of measurement efficiency and accuracy.2. Through modeling and analysis of atomic force probe, a fast calibration method for the relationship between the position of the white light interference fringes and the vertical displacement of the atomic force probe is proposed. The calibration method can effectively solve the problem of dynamic change of fringe resolution, and ensure the measurement accuracy of the instrument.3. The control method of an atomic force probe to automatically contact the measured surface is studied. According to the calibration results of the probe, the control method can calculate the zero-order fringe starting position which can satisfy the requirement of instrument resolution and control the atomic force probe quickly contact the work piece.4. Design and develop a software system for WLIAFM on the Visual Studio 2010 development platform. Multi-thread synchronization control technology is applied in the software system, to achieve motion control, image acquisition, image restoration and other functions of the effective integration and efficient time reuse, to complete the measurement, analysis and evaluation of Nano surface topography.5. Combined with the key technology and the software, the WLIAFM instrument was constructed. The running parameter was tested of the instrument to select appropriate parameters to reduce the measurement error. The whole test was carried out, and the results were obtained.