Effect of pupil filter position on superresolution properties of confocal measurement system

Confocal measurement system is recently widely used as important tools for measurement of three-dimensional microstructures and surface contours because of its good 3D chromatographic imaging capability. And superresolution pupil filter is often used for improving the resolution of confocal measurement system because of its easy structure, thereby satisfying the measurement requirement of ultra-precision microstructures for higher spatial resolution. Because the pupil filter improves the resolution by changing the amplitude and phase distribution of light beam, the position of pupil filter has an important effect on the resolution. In this paper, the measurement model of confocal measurement system is established for different position of pupil filter, and based on these models; the resolution properties are analyzed by emulation to confirm the best position of pupil filter in the measurement system. And the optimized phase-only filter is combined with a confocal measurement system to improve the lateral resolution and the test setup is established. In order to verify the validation of the above theory, the standard step is measured using the established setup when the pupil filter is at different position. Preliminary experiments and analyses indicate the system using a phase-only filter at different positions can achieve different resolutions. The confirmation of the best position of the pupil filter can provide effective theory approach for optical system design, and more effectively improve the measurement capability.