Design and development of a hybrid confocal-interferometric probe system with common path

Non-contact, high-precision measurement techniques are essential for accurately characterizing the surface profiles of optical components, particularly aspheric and freeform surfaces. Among these techniques, confocal and interferometric methods are widely adopted, offering high absolute accuracy and extended measurement range, respectively. However, due to differences in measurement principles, optical path compatibility, system size, and cost, their complementary strengths remain difficult to integrate—limiting both the efficiency and integration of advanced optical manufacturing systems. To address this challenge, we propose a hybrid confocal-interferometric probe system based on a dual-wavelength common-path optical design. By directing two different-wavelength laser beams into a common-path, the system effectively eliminates the differential drift typically observed in traditional dual-path configurations. To further reduce system footprint while maintaining high-precision performance, an integrated waveplate-array detector is developed to enable high-sensitivity phase detection of the interference signals. This compact design minimizes the size of interferometric detection module without compromising overall resolution and robustness. Experimental validation focused on the evaluation of zero-point positioning stability and repeatability in confocal mode. The results demonstrate the confocal module could effectively assist in the zero-point positioning of the probe, with a positioning error of less than 467 nm. This work presents a compact, integrated, and interference-resistant confocal-interferometric hybrid measurement system, providing a practical solution for high-precision and large-range surface metrology..