Optical path optimization of chromatic line confocal displacement sensor for high resolution and wide range

This study introduces the optical path-optimized dual-grating chromatic line confocal imaging (DG-LCI) technique for high-resolution and wide-range surface topography measurements. Chromatic line confocal imaging (LCI) finds extensive applications in high-speed 3D imaging of surface morphology, roughness analysis in industrial production, and quality inspection. A key advantage of LCI is its ability to achieve a large depth of focus, enabling the imaging system to measure a wide range in the Z direction. However, the challenge lies in the trade-off between the measurement range and resolution. Increasing the measurement range reduces the resolution, making it unsuitable for precise measurements required in industrial processing. Conversely, enhancing the resolution limits the measurement range, thereby sacrificing the advantage of LCI systems’ broad measurement capabilities. Addressing this limitation, we propose a dual optical path dual-grating structure using a simplified and ingenious optical path optimization design. This design overcomes the challenge of sacrificing the millimeter-level measurement range while simultaneously improving the resolution. Rigorous simulations and experiments validate the effectiveness and validity of our proposed method.