Fabrication of micro-ball styluses for scanning-type surface form metrology

Two types of micro-ball styluses were fabricated for scanning-type surface form metrology. The micro-ball stylus is composed of a precision glass micro-ball and a shaft made by stainless steel or glass tube. The diameter of the micro-ball was less than 50 μm. The tip angle of the glass-tube shaft was approximately 10 degrees and that of the stainless steel shaft was approximately 50 degrees. It was confirmed that the micro-ball stylus with the glass-tube shaft can tolerate a 90 mN external force applied from the direction with an angle of 45 degrees with respect to the shaft axis, which was much more tolerant than the micro-ball stylus with the stainless steel shaft. To reduce the influence of the stick-slip phenomena caused by friction between the ball and the scanned surface, a PZT actuator was added to the micro-ball stylus, which is called the micro-tapping probe, so that the ball can be oscillated with a high frequency. Experiments of scanning the micro-ball stylus, which was mounted on an air-bearing displacement sensor, over a flat surface were carried out to test some basic performances of the micro-ball stylus.