Microscopic surface estimation through light distribution analysis of reflected laser beam

There are shortcomings for light interferometry-based non-contact microscopic surface measurements when used in-process, thus this study proposes an enhanced measurement method based on light reflectivity. Although reflected light contains information about surface shape, the entire surface profile cannot be measured directly such as in the interferometry-based method. Therefore, a different approach is used to overcome these limitations: a detailed surface model is developed from surface height and spatial frequency. Light reflectance theory is adopted to simulate light scattering in many virtual specimens, which are generated by a light reflectance model. As a result, a notable correlation between surface components and reflected light has been established. Even though either simulations or experiments can reveal the correlation as a numerical formula, one of the surface components is used separately, thus a signal-processing algorithm to decompose surface components is proposed in this study. In order to prove the reliability of the newly proposed measurement scheme, experiments are conducted using a fabricated optical probe.