We present an interactive 360-degree tabletop display system for collaborative work around a round table. Users are able to see 3D objects on the tabletop display anywhere around the table without 3D glasses. The system uses a visual perceptual mechanism for smooth motion parallax in the horizontal direction with fewer projectors than previous works. A 360-degree camera mounted above the table and image recognition software detects users' positions around the table and the heights of their faces (eyes) as they move around the table in real-time. Those mechanics help display correct vertical and horizontal direction motion parallax for different users simultaneously. Our system also has a user interaction function with a tablet device that manipulates 3D objects displayed on the table. These functions support collaborative work and communication between users. We implemented a prototype system and demonstrated the collaborative features of the 360-degree tabletop display system.

A method to create multipoles comprising a cluster of focused sources by using a linear loudspeaker array has recently been investigated. Directivities in a listening area were confirmed with examples of primitive multipoles such as dipoles and quadrupoles. This paper describes a method to create a sound source having more complex directivity by using a superposition of multipoles comprising a collection of focused sources. An analytical method is also described with which coefficients can be obtained for each multipole by circular harmonic expansion of a sound field created by a directional sound source and Taylor expansion of the corresponding sound field. Simulation results show that a superposition of multipoles based on analytical conversion introduces desired directivities to the sound sources created in the listening area by a linear loudspeaker array.