Phase-only pupil filtering confocal measurement system with higher lateral resolution

Abstract

Phase-only pupil filtering confocal microscopy (PFCM), a new approach is proposed to achieve a higher lateral resolution required for ultraprecision measurement of microstructural workpieces, which uses a three-zone phase-only pupil filter with lateral superresolution capability obtained through optimized design to change the confocal microscopy system's (CMS) distribution of three-dimensional point spread function, so that the CMS lateral resolution is therefore significantly improved while its axial resolution is slightly improved. Preliminary experimental comparison and analyses indicate that, the lateral and axial resolutions of PFCM are better than 0.2μm and 2nm, respectively, when λ= 632.8 nm, NA=0.85 and lateral spot size with a three-zone phase-only pupil filter G_T=0.65.