Confocal measurement for surface area of hardness indentation

A confocal measurement method for hardness indentation surface area with diagonal length less than 20 μm was proposed. The indentation of samples was scanned and measured by laser scanning confocal microscope at an interval of 0.1 μm. The three dimensional data of indentation were obtained by the enveloped fitting of all data sets. The method of rotating plane was combined with the feature of normal vector to extract the indentation accurately. The surface area of the indentation was obtained by the triangular mesh construction algorithm, and the hardness value of the sample was calculated. Compared with the traditional imaging optical microscope method, the resolution of confocal measurement method was improved by 30%, and the uncertainty of synthetic standard decreases by 1 HV on average. The results show that the confocal method can measure the indentation surface area with high accuracy and high stability.