An apparent 3-D image can be perceived from only two 2-D images displayed at different depths, when an observer views them from the direction in which they are overlapped. The two 2-D images are created from an original 2-D image by dividing its luminance according to independently obtained depth information. Subjective test results show that (1) an apparent 3-D image is perceived and (2) the perceived depth continuously varies according to the change in luminance ratio between the two 2-D images.

This paper proposes a technique that can protect the copyrights of digital content for 3D printers. It embeds the information on copyrights inside real objects fabricated with 3D printers by forming a fine structure inside the objects as a watermark. Information on copyrights is included in the content before data are input into the 3D printer. This paper also presents a technique that can non-destructively read out information from inside real objects by using thermography. We conducted experiments where we structured fine cavities inside the objects by disposition, which expressed binary code depending on whether or not the code was at a designated position. The results obtained from the experiments demonstrated that binary code could be read out successfully when we used micro-cavities with a horizontal size of 2 x 2 mm, and character information using ASCCI code could be embedded and read out correctly. These results demonstrated the feasibility of the technique we propose.

We have found a novel three‐dimensional (3‐D) display mechanism using only two 2‐D images displayed at different depths. It is based on a new perceptual phenomenon induced by the human binocular visual system and enables an observer using no extra equipment to perceive an apparent 3‐D image of continous depth when the luminance is divided between the 2‐D images according to the 3‐D image depth. We have also develop a prototype direct‐vision 3‐D display using this mechanism. It can easily produce moving 3‐D color images by using color conventional 2‐D displays.

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A new 3D display system based on integral imaging technology was developed by combining two methods. One is the extended fractional view method in which various LCDs and fly's eye lenses can be used together, and the other is the slanted lens array method that can reduce the moiré pattern.

We propose a novel technology that can prevent the illegal use of images of objects that do not have watermarking. This technique uses illumination that invisibly contains the watermarking. As the illumination for the object contains watermarking, the image of the object taken by the camera also contains watermarking and this watermarking can be extracted by image processing. We conducted experiments where one-bit binary data were embedded in one block that consisted of 8 x 8 pixels using the phase of the highest frequency component generated by DCT. The experimental results revealed that embedded data could be read out extremely accurately, reaching 100% with the majority method, which used three data embedded in three separated blocks. The experimental results demonstrated the feasibility of the technology we propose.

This paper provides a novel technique to embed high-density information in objects fabricated with a 3D printer using a near infrared fluorescent dye. Regions containing a small amount of fluorescent dye are formed inside the object as it is fabricated to embed information inside an object, and these regions form a pattern that expresses certain information. When this object is irradiated with near-infrared rays, they pass through the resin but are partly absorbed by the dye, and it emits near-infrared fluorescence. Therefore, by using a near-infrared camera, the internal pattern can be captured as a high-contrast image, 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 know the depth of the patterns from the image because the profile of the brightness of the captured image of the patterns depends on its depth. Using these profiles enables doubling the amount of embedded information. Experiments we conducted demonstrate the feasibility of this technique.

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