Response characteristics of differential confocal system based on radial birefringent pupil

A radical birefringent pupil filter(RBPF) is designed and optimized in the light of actual needs, and incorporated into a differential confocal microscopic system. The response characteristics of the differential confocal microscope system based on RBPF are then investigated through simulation and experiment using birefringent pupil filter technology and differential confocal microscopic measurement technology. Simulation and experimental results indicate that, with NA=0.65 and λ=632.8 nm, the axial resolution of a differential microscopic system based on RBPF can go up to 2 nm, and compared to a microscopic confocal system without RBPF the relative error for the lateral resolution of a differential microscopic system with RBPF can be reduced by 6.167%. It can therefore be concluded that the differential confocal microscopic measurement system based on RBPF can be used to further improve the spatial resolution of a confocal system, and so it can be incorporated into a coordinate measuring machine for non-contact measurement of dimensions and surface roughness.