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Surface Roughness Evaluation of Milled Steel Surfaces Using Wavelet Transform Of Laser Speckle Line Images
J. Mahashar Ali, H. Siddhi Jailani And M. Murugan

Surface roughness measurement and control are important issues in quality manufacturing. Conventional method of measuring the surface roughness using stylus instrument is intrusive and an offline process. So, there is an increasing need for a reliable method of online surface roughness measurement. In this study wavelet transform was used for online characterization of roughness of milled specimens. Surface laser speckle line images were acquired using a charge-coupled device (CCD) camera and a one-dimensional (1-D) image signal for each specimen was obtained MATLAB software. The 4th and 5th order detail coefficients of wavelet transformed image signal was used for the evaluation of milled surfaces. The hybrid surface roughness parameter root mean square slope (Rdq) was measured using a stylus instrument. The experiment showed that the mean intensity of the 4th order detail coefficients of the decomposed laser speckle line image signal correlate very well with Rdq values.

Keywords: Redline laser, EN8 plain carbon steel, milling, surface roughness, laser speckle line images, hybrid surface roughness parameter, vision system, image processing, wavelet transform.

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