Resolving phase errors in microsphere assisted interferometry

Microsphere assisted microscopy (MAM) has been rapidly developed to meet the measurement needs of microstructures. MAM can be integrated with optical interference microscopy (OIM) to achieve high lateral resolution surface profile measurement. However, the microspheres introduce intricate phase changes, resulting in optical path asymmetry which is very challenging to compensate for. This limitation constrains the application of MAM in OIM. In this paper, simulation analysis reveals that the phase transmission of the microsphere is influenced by parameters such as microsphere diameter and its relative position to the sample. It is concluded that a unique compensation process must be adopted for each individual microsphere. Addressing this issue, we proposed a phase compensation algorithm based on the three-dimensional position control of the microsphere and integrated it into our combined system of MAM and white light interferometry (WLI), reducing the phase errors introduced by the microspheres while enhancing the lateral resolution of optical system. This approach improved the profile measurement accuracy, offering a perspective for optically measuring the surface profile of intricate microstructures.