Polychromatic optical path compensation method for chromatic confocal spectral interferometric system design

Abstract Chromatic confocal spectral interferometry (CCSI), which integrates spectral confocal microscopy with white-light interferometry, enables high-precision, non-contact displacement measurements over a wide range with sub-micrometer axial resolution. However, traditional CCSI systems often suffer from inadequate optical path matching across the spectral bandwidth, leading to reduced interference contrast and limited accuracy. To address this issue, we propose a polychromatic optical path compensation method based on group-velocity optical path difference matching, and implement it in a Linnik-type CCSI system. This approach corrects chromatic dispersion and path mismatches, thereby maintaining stable coherence across the entire operational bandwidth. A CCSI system implementing this method is developed, achieving hardware-based dispersion compensation with sub-micrometer accuracy. Experimental validation demonstrates clear improvements in interference contrast, axial resolution, and repeatability. These enhancements significantly expand the performance envelope and applicability of CCSI, particularly for surface profiling, precision manufacturing, and micro- and nano-positioning.