Hybrid diffractive-refractive lens for chromatic confocal measurement system

A novel chromatic confocal measurement (CCM) method using a hybrid diffractive- refractive lens is presented. This hybrid diffractive- refractive lens is designed to optimize the linearity of chromatic dispersion and minimize the size of the optical system. The hybrid diffractive- refractive lens is fabricated by etching a diffractive surface onto a quartz aspheric lens through lithography, which combines the high numerical aperture (NA) of a refractive lens with the unique dispersion properties of the diffractive optical elements (DOE). The lens is incorporated as a dispersive objective lens in a CCM experimental system. The system has a measurement range of 514.8 µm, calibrated using a laser displacement interferometer. The experimental results show that the wavelength-to-axial position coding of the CCM system achieves high linearity (R