3D intraoral scanning system using fixed pattern mask and tunable-focus lens

Abstract

We report the fabrication and performance of a three-dimensional (3D) intraoral scanner based on structured illumination microscopy. The scanner uses a tunable-focus lens for depth scanning and a pattern mask for projecting structured light onto the sample. The tunable-focus lens was used to acquire images from various focal planes, and a fixed pattern was used to gauge the correct focus. By fixing the pattern mask, a camera installed at the same focal point as the sample focus acquired an image at each focal plane, resulting in an improvement in the scanning speed. The proposed method performs optical sectioning on sequentially acquired images while varying the focal planes by estimating pattern modulation in the spatial domain; it then reconstructs 3D point clouds by stacking up the optically sectioned image. The fixed pattern mask, however, caused a color loss at the pixels where the patterns are projected. The proposed method solves this problem by applying a low-pass filter and a polynomial interpolation to fill the loss. The feasibility of the proposed system is confirmed by reconstructing a three-dimensional image of the entire tooth sample by acquiring an image at 500 fps and obtaining 10 point clouds per second.