Resolution enhancement is a basic and important technology in image/video processing. The goal of resolution enhancement is to reconstruct high-resolution image frames from the corresponding low-resolution versions. In this paper, an adaptive resolution enhancement scheme based on iterative back-projection was proposed. According to sub-pixel interpolation, additional information composed of several low-resolution shifted images can be created. After giving initial estimates for each low-resolution shifted image, reconstructed high-resolution images are derived by using a modified iterative back-projection and then fused to be a high-resolution one. Finally, a post-processing is utilized to reduce the blocking artifacts within the reconstructed high-resolution images. According to performance comparison, the experimental results, in terms of PSNR and NQM, demonstrate that the proposed scheme is superior to these existing methods.