High-resolution divided-aperture differential confocal sensing technique

In order to improve axial resolution of the confocal sensor and realize high accuracy measurement of micro-topography, the split-pupil differential confocal sensing technique is proposed. The key parameter optimization theory is further studied, and a divided-aperture differential confocal microscopic sensor with optimal theoretical parameters is developed. The developed sensor combines divided-aperture differential confocal microscopy and virtual pinholes based on editable detection device. The offset of the detection area can bring the phase offset of the axial characteristic curve in the divided-aperture confocal microscopy. Two virtual pinholes are set symmetrically on the detection surface in a specific direction, whose responses are obtained and differentially processed to achieve high axial resolution and high positioning accuracy measurement. The developed sensor are tested The axial response, nonlinear property of the developed sensor are evaluated and the actual sample is measured. The axial relative displacement measurement formula is obtained. Experimental results indicate that the axial resolution of the developed sensor is 5 nm and the lateral resolution is 0.82 μm, which can provide a new sensing technology and system for the high-precision measurement of the three-dimensional surface of the microstructure.