Transparent Tabletop Interface for Multiple Users on Lumisight Table Yasuaki Kakehi 1 , Takero Hosomi 1 , Makoto Iida 1 , Takeshi Naemura 1 , Mitsunori Matsushita 2 1 The University of Tokyo 2 NTT Communication Science Labs., NTT Corp. {kakehi, hosomi, iida, naemura}@hc.ic.i.u-tokyo.ac.jp, mat@cslab.kecl.ntt.co.jp Abstract This paper presents a new type of tabletop interface on Lumisight Table. Putting physical objects on a tabletop display is one of the typical methods for intuitive tangible input. To date, various interactive systems that can identify and track the tabletop objects by using a camera, have been proposed. However, in these systems, the existence of objects with special devices or markers can disturb users’ natural interaction by hiding displayed information. To solve this problem, the authors propose a transparent tabletop interface that is transparent from users but visible from a camera installed inside the system. This paper describes our research motivation, design and implementation of this interface, and examples of interaction. 1. Introduction In the fields of CHI (Computer Human Interaction) and CSCW (Computer-Supported Cooperative Work), tabletop displays have been attracting much attention, since an electronic display screen embedded on a horizontal tabletop is useful for supporting users’ work or group discussion. One special feature of a tabletop display is that physical objects can be placed on the screen. Because such actions are understood intuitively in the same way as work done at an ordinary desk, several systems in which the placement of physical objects serves as input methods have been proposed. The output corresponding to the placement of physical objects can appear in the content of the screen image. However, this method may result in inconveniences such as the following. Physical objects equipped with electronic devices, markers, etc. restrict user's natural interactions. Physical objects placed on the surface of the table obstruct view of the image on the display. To solve these problems, this paper proposes a transparent tabletop interface. So far, the authors have developed and reported an interactive view-dependent tabletop display system[1]. It can present different images to multiple users sitting around the table, and is called the Lumisight Table. Based on this technology, this paper presents a transparent tabletop interface for multiple users with the features listed below (See Figure 1). The interface appears transparent to the users around the table, so the image on the tabletop screen is not obstructed. The camera installed inside the table can recognize the positions of the objects so that their placement can be used for input. First, the authors briefly describe the Lumisight Table, and then explain the design and implementation of the transparent tabletop interface and present an example of interaction using it. 2. Related Works Tabletop displays can become an effective workspace for the users (e.g. users can put physical Figure 1. Transparent tabletop interfaces. Proceedings of the First IEEE International Workshop on Horizontal Interactive Human-Computer Systems (TABLETOP ’06) 0-7695-2494-X/05 $20.00 © 2006 IEEE Yasuaki Kakehi, Takero Hosomi, Makoto Iida, Takeshi Naemura, and Mitsunori Matsushita, "Transparent Tabletop Interface for Multiple Users on Lumisight Table," First IEEE International Workshop on Horizontal Interactive Human-Computer Systems (TABLETOP '06) pp. 143-150