2020 Volume 8 Issue 1 Pages 2-9
This paper presents a new technique to embed information in 3D printed objects using a near infrared fluorescent dye. Regions containing a small amount of fluorescent dye are formed inside an object during fabrication to embed information inside it, and these regions form a pattern that expresses certain information. When this object is irradiated with near-infrared rays, they pass through the object made of resin but are partly absorbed by the fluorescent dye in the pattern regions, and it emits near-infrared fluorescence. Therefore, the internal pattern can be captured as a high-contrast image using a near-infrared camera, and the embedded information can be nondestructively read out. This paper presents a technique of forming internal patterns at two different depths to double the amount of embedded information. We can determine the depth of the pattern from the image because the distribution of the brightness of the captured image of the pattern depends on its depth. We can also know from the brightness distribution whether or not a pattern exists at two depths. Because this can express four states, the amount of embedded information can be doubled using this method. We conducted experiments using deep learning to distinguish four states from the captured image. The experiments demonstrated the feasibility of this technique by showing that accurate embedded information can be read out.
