Confocal displacement sensor based on chromatic dispersion splicing for high precision and wide range

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.