- With the use of an immersive display system such as the CAVE, the user is able to perceive a 3D environment realistically. However, the interaction on such systems faces some difficulties inherent with inaccurate tracking, lack of depth cues, and unstable spatial manipulation without sense of touch. In this paper we propose a see-through the lens interface using a PDA (Personal Digital Assistance) for supporting spatial manipulation within an immersive display. A PDA-based see-through the lens interface has a number of advantages over related studies, such as physical contact of screen surface for easy 2D manipulation in 3D space, built-in controls for immediate command execution, and built-in display for flexible GUI (graphical user interface), which we believe should give more natural and flexible manipulation and interaction schemes in an immersive environment. In this paper, described are basic ideas and implementation details of the proposed system and some functionalities provi...