Optical System Design for Chromatic Confocal Displacement Probes.

The Displacement probe is an important part of chromatic confocal systems, and its imaging capabilities directly affect the performance of the system. The optical structure of the probe is usually designed as a whole, but there are many variables that complicate the design. In this paper, a modular structure design scheme of the probe is proposed to simplify the design. The optical system consists of the collimation lens and the hyperchromatic lens, which are designed and optimized separately. The initial structural design scheme based on the aberration theory is mainly introduced. Two probes with ranges of 3 mm and 10 mm are taken as examples to show that different measurement performance of the probe can be achieved by changing the lens module. Finally, the height of three standard gauge blocks was measured with a 3 mm range displacement probe. The full width at half maximum (FWHM) of the spectral response curve in the working spectral band is 0.9-5.9 nm, and the height measurement errors of gauge blocks are less than $3.0\ \mu\mathrm{m}$ . In the case of selecting other experimental devices, the designed probe not only has high resolution, but also achieves micron-level measurement error. The proposed design scheme is feasible.