Spectral stripe based large range chromatic confocal displacement system with nanometer uncertainty

We present a novel, to the best of our knowledge, design of a chromatic confocal displacement system (CCDS) based on spectral stripe. In this system, confocal light collected by the dispersive lens is shaped by a Powell lens and then diffracted onto a detector in the form of a thin straight stripe. The displacement variant is converted into the change of stripe positions on the detector. Unlike the spectral profile or the diffractive spot, the spectral stripe significantly increases the pixel number for analysis and effectively suppresses random noises. Simulation and experiment results show that the positional uncertainty of the spectral stripe is dramatically reduced and reaches less than 1‰ pixel. Measurement uncertainty is less than 14.3 nm within the whole measuring range of 4 mm. It provides a new way for developing large range CCDS with nanometer uncertainty.