Improving axial resolution of fiber chromatic confocal systems via 2D spectral demodulation

This study proposes a fiber chromatic confocal method with a 2D spectral demodulation to improve the axial resolution, which is achieved by the cross-dispersion of an echelle grating and prism. A chromatic confocal axial response model is derived based on confocal imaging and grating diffraction theories. The model parameters are fitted using calibration data, thereby facilitating the decoding, intensity correction, and reconstruction of the spectrogram to convert the 2D spectral peak accurately into the measured position. Experimental results show the axial resolution of 0.1 μm for the fiber probe with a measurement range of 3 mm, doubling the performance of conventional 1D spectral demodulation methods. This improvement demonstrates the applicability of the proposed method for high-precision measurement requirements, such as the assembly and testing of aeroengines.