Object detection in image sequences has a very important role in many applications such as surveillance systems, tracking and recognition systems, coding systems and so on. This paper proposes a unified framework for background subtraction, which is very popular algorithm for object detection in image sequences. And we propose an algorithm using spatio-temporal thresholding and truncated variable adaptation rate (TVAR) for object detection and background adaptation, respectively. Especially when the camera moves and zooms in on something to track the target, we generate multi-resolution mosaic which is made up of many background mosaics with different resolution, and use it for object detection. Some experimental results in various environments show that the averaged performance of the proposed algorithm is good. (c) 2005 Elsevier B.V. All rights reserved.