In this paper, a semi-automatic realtime calibration technique for a handheld projector is described. The proposed technique always keeps a shape of a projected screen rectangular on a specified projection surface, while a user continuously changes his standing position or the pose of the projector. The technique is especially useful for a future mobile phone with a built-in projector that allows a user to project its screen onto any surface in any location and share the screen with multiple people. Informal evaluations using the technique have been conducted to identify the level of its acceptability by users and to find problems to be improved. An example entertainment application to explore possibilities of the proposed technique has been developed.

In this paper, a system called Caretta that integrates personal and shared spaces to support face-to-face collaboration is described. We use PDAs and a multiple-input sensing board for personal and shared spaces, respectively. Users of Caretta can discuss and negotiate with each other in the shared space by manipulating physical objects, while they individually examine their ideas in their own personal spaces. Caretta allows users to participate in group activities interchangeably and seamlessly using both these spaces. Caretta is applicable to various collaborative tasks. In this paper, it supports users in urban planning tasks. User studies of Caretta demonstrated that it allowed users to collaborate in a flexible fashion: users could work individually in their personal spaces at their own pace, cooperatively work together in the shared space, and smoothly transition between both of the spaces.