Lateral resolution, as one of the most important parameters of a confocal system, has a direct effect on the measurement
accuracy of a confocal system. The lateral resolution of a confocal system can be improved by introducing a radial
birefringent pupil filter into a differential confocal system. The pupil function of this radial birefringent pupil filter can
be obtained using Jones algorithm and, the angle between the polarization direction of the polarizing film of the lateral
birefringent filter and the optical axis of the birefringent element, and the size of a filter a, can be got by analyzing the
first zero point G. Meanwhile, we analyzed the influence of such factors as the defocusing amount on the lateral response
of the system. It was proved through simulation and experiments that the lateral resolution of a confocal system can be
improved using an optimized radial birefringent pupil filter.