Research On Surface Topography Measurement Technology Based On Confocal Imaging

Surface topography is an important factor in evaluating the surface quality of objects.Surface roughness is an important parameter for surface topography.The detection of surface roughness is widely used in the manufacturing process of industrial parts.The existing roughness measurement methods mainly include nano surface roughness analysis method,stylus measurement method and white light interference method,but there are defects such as high measurement environment requirements or easy scratches on the surface of the object.The confocal microscopy imaging roughness measurement method can measure parts with high local slopes,and is a non-contact measurement method,which has important applications in the surface quality evaluation of high-precision parts.This paper studies the surface topography measurement technology based on confocal imaging in order to provide theoretical guidance for the development of domestically made surface measurement confocal microscopes.The main contents are as follows:(1)Aiming at the confocal microscopy imaging technology,the imaging principle and scanning method are analyzed,and its three-dimensional tomography capability is deeply explored.The confocal imaging is performed with a planer sample with Ra=1.6?m,and the confocal three-dimensional tomography capability is verified.On this basis,a three-dimensional reconstruction algorithm is proposed,which reconstructs the sequence pictures taken by the confocal imaging system to three-dimensionally restore the contour of the object;and conducts experiments on Mitutoyo 178-601 high-precision roughness samples and transparent samples with calibrated height differences,Perform qualitative and quantitative verification of the3 D reconstruction algorithm.The average relative error between the height difference of the transparent sample reconstructed in the experiment and the nominal value is3.11%,which verifies the feasibility of the 3D reconstruction algorithm and prepares for the next step of drawing roughness contours.(2)The surface topography of an object contains a variety of contour components,including roughness contour,waviness contour and shape contour.In order to extract the roughness profile from the original profile,the types and functions of the filter are analyzed,a mathematical model for Gaussian filtering to extract the roughness profile is established,and the method of selecting the cut-off wavelength in the mathematical model is explored.Computational simulation shows that the roughness contour extraction model can successfully extract the roughness contour of the object.(3)Due to the boundary effect of the Gaussian filter,a piece of data is lost at the left and right ends of the obtained roughness profile,and the boundary area correction algorithm needs to be used to correct the boundary area.In order to adapt to the surface with different steepness of the overall contour,a universal modified boundary area algorithm is proposed.The simulation shows that the universal correcting boundary area algorithm has a good correcting effect on steep contours.For objects with relatively smooth overall contours,experiments show that the conventional boundary contour extension method and the boundary region correction method have similar effects.For objects that are relatively steep as a whole,the relative errors of the conventional boundary contour extension method and boundary region correction algorithm are 0.31% and 3.48%,respectively,indicating that the boundary region algorithm in this paper has good adaptability to various contours.(4)In order to verify the surface measurement technology based on confocal imaging proposed in this article,16 experimental samples were imaged with a confocal imaging system,and the roughness parameter Ra value of each sample was calculated,and compared with Keyence VHX-6000 ultra-depth-of-field display The values measured by the micro-measurement system are compared,and the average relative error values of the two are within 5%,which shows that the surface measurement technology based on confocal imaging in this paper has high accuracy.(5)The surface roughness measurement software was written,and the confocal sequence pictures were successfully imported.The all-focus image and the three-dimensional contour image of the sample can be obtained,as well as the two-dimensional contour and the roughness parameter Ra value of the designated linear area,which can be used to guide the surface measurement.Development of focusing microscope.