A non-imaging optical system for characterisation of ball-shaped micro-indenters

To quantitatively determine the tip radius of spherical/conical and Rockwell micro-indenters, a practical tip radius measurement system is presented. Realization of the optical system has been detailed, including its theoretical and actual resolution and error sources. For the purpose of experimental investigation of the performance of the non-imaging radius measurement system, a sapphire sphere with a nominal radius of 200 μm has been measured. Detailed data analysis indicates that higher-order form deviation of the object under test might be one of the key error sources within the calibration setup. Further experiments indicate that the prototype of the non-imaging system is able to measure real conical and Rockwell indenters with adequate resolution.