In a previous study, we have developed a directional volumetric display that handles multiple directional images. To realize a multilingual digital signage system, we implement a language identification function on the directional volumetric display. The language identification (English, Spanish or French) is performed using a convolutional neural network. The discrimination accuracy of the three languages is 91.9%. Combining the language identification function with the directional volumetric display, an image can be directed toward a specific speaker. The result is a multilingual digital signage system that adapts the image presentation to the spoken language.

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Using threads and a projector, a directional volumetric display capable of moving images and full-color representation was developed in our previous work. However, the horizontal resolution of the directional volumetric display could only achieve 20 pixels with 400 threads. Further, the conventional algorithm requires P squared threads per P horizontal pixels of the input image. Because it is difficult to place a large number of threads, thus, a new algorithm for developing projected images to improve the directional volumetric display's resolution was proposed. It is feasible to display images of P pixels with at least P threads using this technique. However, the higher the resolution, the lower the image quality in the proposed algorithm. Thus, it was verified how many threads can be used to display high-resolution images without degrading the image quality. Further, by representing the horizontal resolution of the input image with 5-6 threads per pixel, it is possible to display high-resolution images while maintaining the image quality. The proposed technique can display 64 pixels per 384 threads, whereas the conventional method can only display 20 pixels input images per 400 threads.INDEX TERMS volumetric display, directional display, interactive display, high resolution.