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Measurement Science and Technology Volume 25 Number 6, 2014.
Kuang-Chao Fan 1,2, Na Wang1, Zhi-Wei Wang1 , Hui Zhang1
1 School of Instrument Science and Opto-electronic Engineering, Hefei University of Technology, Tunxi Road 193, Heifei, 230009, People’s Republic of China and
2 Department of Mechanical Engineering, National Taiwan University, l, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan.
Abstract
In the field of micro/nano technology, microspheres are often used as the tip-ball of a measuring stylus, such as in micro/nano coordinate measuring machines (CMMs). Conventional tactile probes adopt ruby or steel balls with diameters in the range of several millimeters to 0.3 mm. For a micro-CMM, the required probing ball is as small as possible in order to be inserted into a small groove for side wall measurement. The exact diameter of the tip-ball has to be calibrated for radius compensation and its roundness error has to be qualified. A roundness measuring system for microspheres is developed in this study. Two small Michelson interferometers are designed for direct measurement of microsphere diameter from both sides, being a two-point method. By rotating the measured sphere and reading the displacement shifts of the two interferometers, the run-out of the sphere can be eliminated. The resolution of the developed system can reach 1 nm and the accuracy can reach 10 nm. Two microspheres are tested with good repeatability. This system can also be used for macrosphere measurement.
