Calibration method of topography error of white light interferometry on curved surface sample measurement

White light microinterferometry has obvious advantages in measuring the topography of planar step structures. However, due to the limitation of the numerical aperture of the objective lens, the reflected light on the surface of the sample is weakened with the increase of the slope when measuring the curved surface sample, and the contrast of the interference signal decreases, which leads to the increase of the error of topography measurement. Based on the theory of surface transfer function (STF), the inverse filter can be calculated to correct the topography measurement error of curved surface samples. However, the gain of the inverse filter of the existing method is limited, which is unable to elevate the high-frequency signal in the spectrum, and the improvement of the maximum measurable slope is limited. To address this issue, the modulus of the virtual STF calculated by the characteristic parameters of the white light interferometer was used as the amplitude gain function, and the phase of the measured STF obtained by the Fourier transform of the measured interferogram was used as the phase compensation function. A virtual-measured fusion inverse filter was formed, which realized the correction of the curved surface topography measurement error of white light interferometer. Using this method to correct the topography measurement results of the microsphere, the maximum measurable slope after correction is increased from 8.09° to 21.20°, and the root mean square error is reduced from 0.545 5 μm to 0.175 9 μm, which achieves the purpose of improving the maximum measurable slope of curved surface sample and reducing the measurement error, and effectively improves the measurement range of the instrument for the curved surface sample.