Display systems with high quality and wide display screen can be used at fixed place due to big size and heavy weight. On the other hands, mobile systems have small display screen and thus decrease user-immersion because it is compact. In this paper, we resolve these drawbacks of established display systems by proposing a novel portable projection-based augmented reality (AR) system. The system uses a camera mounted on PDA and a small projector to measure characteristics of screen surface. We use geometric correction and radiometric compensation technique to project undistorted image in user viewpoint onto an arbitrary screen surface. Rather than float point operations, we use integer point operations to enhance system performance. Our proposed system not only supports mobility but also wide display screen. Usability of our system is verified through experimental results and user evaluation.