Study Of Noncontact Measurement And Feature Evaluation Method For Areal Surface Texture

Surface structure means surface geometry structure and the relevant geometrical features. Surface texture plays a vital role in the functionality of modern engineering products. Currently surface metrology discipline is undergoing a huge paradigm shift from 2D profile to 3D areal and from stochastic to structured surface characterization. Areal surface texture measurements have greater fully functional significance parameters, better repeatability and more effectively visual express than profile measurements. The existing optical microscopy image measurement and white light microscopy interference measurement can be used for the noncontact measurement of 2D and 3D scale of areal surface texture respectively. However, the measurement field and lateral resolution of the two measurement methods are restricted to the numerical aperture of objective and one of the measurement methods can't achieve the simultaneous measurement of 2D and 3D scale commonly. At the same time, the existing surface texture evaluation methods can't satisfy the evaluation of areal surface texture.In response to these problems above, this thesis has carried out a systematic and in-depth research, and put forward the corresponding solution, the main innovation and research work of the thesis are as follows:A noncontact measurement method for areal surface texture based on the co-integration of optical microscopy image measurement and white light microscopy interference measurement is proposed, which measures not only 2D size of length but also 3D surface texture. Therefore the problem, which the existing single measurement method of optical microscopy image measurement or white light microscopy interference measurement can't give consideration to 2D size and 3D surface texture measurements and is of low efficiency, is solved.An automatic search and location method of fringe for white light interference measurement based on the normalized standard deviation of gray value of interference microscopy images is proposed. So the problem of inefficiency for the search of interference fringe by man is solved.A mathematic model for the calibration of CCD cameras and the calculation of the angles between CCD and level worktables is established and the problem is solved that the CCD calibration and angle measurement of general measurement system depending on external equipments.A non-orthogonal worktable moving strategy is set up for the seamless stitching measurement of optical microscopy image measurement and white light microscopy interference measurement, which reduces the cost of stitching and enlarges the measurement field of the two measurement methods. Therefore the problem of the two methods, which the lateral resolution and the measurement filed are restricted to the numerical aperture of objective, is solved.A method of region combination based on gray value pretreatment is proposed and then the problem of areal surface texture over segment is solved. The 3D-Motif evaluation method has been extended then the problem of surface structure analysis and evaluation with distinct regions is solved.A 2D&3D optical microscopy measurement system for areal surface texture has been developed. Compound optical microscopy imaging system, 3D precision displacement system, and corresponding hardware circuit have been designed independently. The software of optical microscopy image measurement, white light microscopy interference measurement and surface texture evaluation has been developed, the examples of measurement and evaluation and the measurement results are given. The practicality and effectiveness of the proposed method of measurement and assessment have been verified.