Measurement of probe-stylus sphere diameter for micro-CMM based on spectral fingerprint of whispering gallery modes

Probe calibration contributes to the measurement uncertainty of micro-coordinate measuring machines (micro-CMMs). This study proposes a new method of measuring stylus sphere diameters for micro-CMMs based on the analysis of whispering gallery modes (WGMs). Depending on the incident wavelength, different WGMs will be excited in the probe stylus, resulting in a wavelength spectral fingerprint that is related to the sphere diameter. In this paper, the diameter of the microprobe stylus sphere was determined with a least-squares method using theoretical and measured spectra of WGMs. The measurement results showed that the precision of the proposed method was ±1 nm.