Imaging Analysis of Micro-milling Tool in the Process of Tool Setting Based on Digital Holography

In the process of ultra-precision machining, the tool-setting accuracy of the micro-milling tool is limited by the tool diameter. The accuracy of tool setting decreases with the decrease of tool diameter, which becomes an important factor for restricting the accuracy of ultra-precision machining. Based on the imaging principle of digital in-line holography, an efficient and non-contacted method for tool setting was proposed for improving the accuracy of tool setting. Aiming at the imaging problem of micro-milling tool, the evaluation function based on wavelet transform was introduced in the process of progressive search, so the optimal reconstructed image was accurately obtained through the autofocusing algorithm. Then the zero-order term and the conjugate image were eliminated via the self-snake diffusion. The tool contour was extracted by Sobel operator, and tool diameter was measured using different methods. Measurement results proved that holographic imaging can meet the requirements of in-position dynamic measurement for micro-milling tools, and also provided an important basis for the accuracy of tool setting.