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11 November 2010 Design of 3D vision probe based on auto-focus
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Machine vision now is widely used as non-contact metrology which is a trend of measurement. In this article, a 3D machine vision probe for engineering is designed. The XY axial measurement is done by 2D vision metrology, while the Z axial height is measured by microscope through auto-focus (AF). As the critical part of probe, a long work distance (WD) microscope is well designed. To attain the long WD, a positive and a negative lens group configure the microscope. The microscope, with resolution of 1μm and WD of 35mm, is quite closed to diffraction limited as evidenced from MTF (Modulation Transfer Function) chart.The AF, a key technology in probe designing, is particularly introduced. Images acquired by microscope are calculated to get the AF curve data. To make the AF curve smooth, the images are denoised and the curve is processed with a low pass filter (LPF). And a new method of curve fitting is involved to get the accuracy focused position.The measurement with probe shows that the uncertainty is 0.03μm at XY axial plane, while the uncertainty is less than 3μm at Z axial height. It indicates that our probe achieves requirements.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Qian Liu, Daocheng Yuan, and Bo Liu "Design of 3D vision probe based on auto-focus", Proc. SPIE 7855, Optical Metrology and Inspection for Industrial Applications, 78551G (11 November 2010);


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