High-speed and large-range laser differential confocal microscopy based on galvanometer and displacement stage

Considering the high-speed, large-range and high-resolution optical measurement demand in the fields of optical precision machining and semiconductor manufacturing, we propose a laser differential confocal measurement method based on galvanometer and displacement stage (GSLDCM). The method obtains a fitting equation through the differential confocal detection signal near the zero-point with high sensitivity and linearity, to achieve high-speed, high-resolution measurements without axial scanning. Utilizing the galvanometer scanning at a high speed in the transverse fast axis, together with the slow-axis displacement stage scanning, realizes high-speed two-dimensional transverse scanning measurements and large-range scanning in X-direction. This enables cross-scale, high-speed, and high-precision three-dimensional measurements of surface topography. A simulation analysis and experimental verification show that the axial resolution of this method is up to 1 nm. When a 100× measurement objective is used, a three-dimensional morphology measurement of 128 μm × 4 mm can be completed in 855 s. The measurement efficiency is approximately 5 times that of the traditional confocal splicing scanning measurement, which provides an effective technology pathway for a large-scale high-precision inspection in semiconductor manufacturing and other fields.