We demonstrated a three-dimensional (3D) dental scanning apparatus based on structured illumination. A liquid lens was used for tuning focus and a piezomotor stage was used for the shift of structured light. A simple algorithm, which detects intensity modulation, was used to perform optical sectioning with structured illumination. We reconstructed a 3D point cloud, which represents the 3D coordinates of the digitized surface of a dental gypsum cast by piling up sectioned images. We performed 3D registration of an individual 3D point cloud, which includes alignment and merging the 3D point clouds to exhibit a 3D model of the dental cast.

Whole slide imaging (WSI) refers to the process of creating a high-resolution digital image of a whole slide. Since digital images are typically produced by stitching image sequences acquired from different fields of view, the visual quality of the images can be degraded owing to shading distortion, which produces black plaid patterns on the images. A shading correction method for brightfield WSI is presented, which is simple but robust not only against typical image artifacts caused by specks of dust and bubbles, but also against fixed-pattern noise, or spatial variations in pixel values under uniform illumination. The proposed method comprises primarily of two steps. The first step constructs candidates of a shading distortion model from a stack of input image sequences. The second step selects the optimal model from the candidates. The proposed method was compared experimentally with two previous state-of-the-art methods, regularized energy minimization (CIDRE) and background and shading correction (BaSiC) and showed better correction scores, as smooth operations and constraints were not imposed when estimating the shading distortion. The correction scores, averaged over 40 image collections, were as follows: proposed method, 0.39 ± 0.099; CIDRE method, 0.67 ± 0.047; BaSiC method, 0.55 ± 0.038. Based on the quantitative evaluations, we can confirm that the proposed method can correct not only shading distortion, but also fixed-pattern noise, compared with the two previous state-of-the-art methods.

We report herein the fabrication and performance response of a three-dimensional (3-D) intraoral scan probe based on optical coherence tomography (OCT) that enables 3-D structural and functional diagnoses of the human teeth. The OCT system was configured using a swept-source OCT (SS-OCT) with a center wavelength of 1310 nm. The scan probe was built using an MEMS mirror and an optical collimator. The implemented SS-OCT equipped with the MEMS-based scan probe yielded an axial resolution of 10 μm and a scan range of 8 × 8 mm². Two-dimensional (2-D) cross-sectional images of the teeth were acquired by the scan probe based on the OCT. The 3-D volume image was acquired by combining a series of 2-D images, which includes internal and structural information of the human teeth. To utilize the OCT system as an intraoral scanner, partially overlapped 3-D volume images were sequentially acquired and stitched. The 3-D stitching was implemented based on an iterative closest point algorithm. The feasibility of the intraoral scan probe is demonstrated based on its ability to image and characterize the structure and function of the human teeth.

Generally, aspheric glass lenses are manufactured using a glass molding press (GMP) method and a tungsten carbide mold core. This study analyzes the thermal deformation that occurs during the GMP process, and the results were applied to compensate an aspheric glass lens. After the compensation process, the form accuracy of aspheric glass lenses improved from $∼3.7$ to $∼0.35μm$. The compensated lens complied with the actual specifications.

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.