Confocal displacement sensors are widely used in precision metrology, yet their performance is constrained by the trade-off between the measurement range and resolution. In this paper, we propose a chromatic confocal displacement sensor based on dual-path dispersion splicing enabled by a plane-parallel optical film, which doubles the axial measurement range to 1030 µm while preserving a high resolution of 10 nm—an order of magnitude improvement over traditional methods. Guided by a theoretical model describing the chromatic focal modulation, the optical film is optimized to induce a controllable focal shift that supports complementary dispersion regions in the two paths. Experimental results confirm a maximum displacement error of 0.06 µm, comparable to that of a single-path configuration, demonstrating that range extension does not significantly introduce additional systematic error. This approach offers a low-cost and efficient solution for full-field measurement of complex microstructure samples.
Dong et al. (Mon,) studied this question.