High-speed color three-dimensional measurement based on parallel confocal detection with a focus tunable lens

Reflectance confocal microscopy is a widely used optical imaging technique for non-destructive three-dimensional (3D) surface measurement. In confocal microscopy, a stack of two-dimensional (2D) images along the axial position is used for 3D reconstruction. This means the speed of 3D volumetric acquisition is limited by the beam scanning and the mechanical axial scanning. To achieve fast volumetric imaging, simultaneous multiple point scanning by parallelizing the beam instead of transverse point scanning can be considered, using a pinhole array. Previously, we developed a direct-view confocal microscope with a focus tunable lens (FTL) to produce a monochrome 3D surface profile of a sample without any mechanical scanning. Here, we report a high-speed color 3D measurement method based on parallel confocal detection. The proposed method produces a color 3D image of an object by acquiring 180 2D color images with an acquisition time of 1 second. We also visualized the color information of the object by overlaying the color obtained with a color area detector and a white LED illumination on top of the 3D surface profile. In addition, we designed an improved optical system to reduce artifacts caused by internal reflections and developed a new algorithm for noise-resistant 3D measurements. The feasibility of the proposed non-contact high-speed color 3D measurement for use in industrial or biomedical fields was demonstrated by imaging the color 3D shapes of various specimens. We anticipate that this technology can be utilized in various fields, where rapid 3D surface profiles with color information are required.