Fiber-based chromatic confocal microscope with Gaussian fitting method

The chromatic confocal microscopy is an effective method for displacement measurement. However, with relatively low detection efficiency, chromatic confocal systems from previous studies suffer from either a limited measuring range or an unsatisfying resolution. In this paper, a novel chromatic confocal system is proposed based on optical fiber with large diameter that is specifically chosen to allow more light to be detected, thus greatly improving the detection efficiency of the system. To accurately locate the peak wavelength of the recorded spectrum, four data processing methods are proposed and compared, within which the Gaussian fitting model is considered best for the system. A series of experiments are done to verify the feasibility, resolution and stability of the system. An applicable measuring range of 600 μm is discovered with a highly linear range of 400 μm. The system has a high resolution close to 0.10 μm with satisfying stability shown by a long-term displacement standard deviation of 0.16 μm.

► Gaussian fitting to accurately locate peak wavelength in spectrum. ► Highly linear scanning range of 400 μm with superior resolution of 0.10 μm. ► Optical fiber as both transmitting media and large spatial filter. ► Large fiber diameter produces higher detection efficiency.